Science.gov

Sample records for inhibit ligand-dependent transactivation

  1. PLZF-RAR[alpha] fusion proteins generated from the variant t(11; 17)(q23; q21) translocation in acute promyelocytic leukemia inhibit ligand-dependent transactivation of wild-type retinoic acid receptors

    SciTech Connect

    Chen, Zhu; Chen, Sai-Juan; Wang, Zhen-Yi ); Guidez, F.; Rousselot, P.; Agadir, A.; Degos, L.; Chomienne, C. ); Zelent, A. ); Waxman, S. )

    1994-02-01

    Recently, the authors described a recurrent variant translocation, t(11;17)(q23;q21), in acute promyelocytic leukemia (APL) which juxtaposes PLZF, a gene encoding a zinc finger protein, to RARA, encoding retinoic acid receptor [alpha] (RAR[alpha]). They have now cloned cDNAs encoding PLZF-RAR[alpha] chimeric proteins and studied their transactivating activities. In transient-expression assays, both the PLZF(A)-RAR[alpha] and PLZF(B)-RAR[alpha] fusion proteins like the PML-RAR[alpha] protein resulting from the well-known t(15;17) translocation in APL, antagonized endogenous and transfected wild-type RAR[alpha] in the presence of retinoic acid. Cotransfection assays showed that a significant repression of RAR[alpha] transactivation activity was obtained even with a very low PLZF-RAR[alpha]-expressing plasmid concentration. A [open quotes]dominant negative[close quotes] effect was observed with vectors expressing RAR[alpha] and retinoid X receptor [alpha] (RXR[alpha]). These abnormal transactivation properties observed in retinoic acid-sensitive myeloid cells strongly implicate the PLZF-RAR[alpha] fusion proteins in the molecular pathogenesis of APL.

  2. Ligand-dependent inhibition of beta-catenin/TCF signaling by androgen receptor.

    PubMed

    Chesire, Dennis R; Isaacs, William B

    2002-12-01

    Beta-catenin signaling may contribute to prostate cancer (CaP) progression. Although beta-catenin is known to upregulate T cell factor (TCF) target gene expression in CaP cells, recent evidence demonstrates its capacity to enhance ligand-dependent androgen receptor (AR) function. Thus, we wished to further understand the interaction between these two pathways. We find in both CaP cells (CWR22-Rv1, LAPC-4, DU145) and non-CaP cells (HEK-293, TSU, SW480, HCT-116) that beta-catenin/TCF-related transcription (CRT), as measured by activation of a synthetic promoter and that of cyclin D1, is inhibited by androgen treatment. This inhibition is AR-dependent, as it only occurs in cells expressing AR endogenously or transiently, and is abrogated by AR antagonists. Additional analyses convey that the ligand-dependent nature of CRT suppression depends on transactivation-competent AR in the nucleus, but not on indirect effects stemming from AR target gene expression. Given the recent work identifying an AR/beta-catenin interaction, and from our finding that liganded AR does not prompt gross changes in the constitutive nuclear localization of TCF4 or mutant beta-catenin, we hypothesized that transcription factor (i.e. AR and TCF) competition for beta-catenin recruitment may explain, in part, androgen-induced suppression of CRT. To address this idea, we expressed an AR mutant lacking its DNA-binding domain (DBD). This receptor could not orchestrate ligand-dependent CRT repression, thereby providing support for those recent data implicating the AR DBD/LBD as necessary for beta-catenin interaction. Further supporting this hypothesis, TCF/LEF over-expression counteracts androgen-induced suppression of CRT, and requires beta-catenin binding activity to do so. Interestingly, TCF4 over-expression potently antagonizes AR function; however, this inhibition may occur independently of beta-catenin/TCF4 interaction. These results from TCF4 over-expression analyses, taken together, provide

  3. ATF3 inhibits PDX-1-stimulated transactivation.

    PubMed

    Kim, Won-Ho; Jang, Min Kyung; Kim, Choi Hee; Shin, Hwa Kyoung; Jung, Myeong Ho

    2011-11-01

    Chronic endoplasmic reticulum (ER) stress leads to β-cell failure via reduction of pancreatic and duodenal homeobox-1 (PDX-1) activity, which contributes to the pathogenesis of type 2 diabetes. However, the exact mechanisms by which ER stress reduces PDX-1 activity in pancreatic β-cells are unclear. Previously, we showed that ATF3 downregulates PDX-1 gene expression in MIN6N8 pancreatic β-cells. Here, we investigated another role of ATF3 on the regulation of PDX-1 activity. ATF3 significantly inhibited PDX-1-stimulated transactivation of reporter plasmid containing promoters for PDX-1 binding element and the PDX-1 target gene glucokinase, which is dependent on C-terminal domain of ATF3. ATF3 interacted with PDX-1, and effectively inhibited p300-mediated transcriptional coactivation of the PBE-containing promoter, whereas C-terminal domain-deleted ATF3 did not inhibit the transcoactivation of p300. ATF3 decreased the interaction of p300 with PDX-1 in MIN6N8 cells coexpressing PDX-1 and ATF3. In addition, chromatin immunoprecipitation analysis demonstrated that both tunicamycin treatment and ATF3 overexpression inhibited the recruitment of p300 to PDX-1 on the insulin promoter in MIN6N8 cells. Taken together, these results suggest that ATF3 inhibits PDX-1-mediated transactivation through the inhibition of p300-stimulated coactivation, which may lead to β-cell dysfunction by ER stress.

  4. Ligand-dependent activation of transcription in vitro by retinoic acid receptor α/retinoid X receptor α heterodimers that mimics transactivation by retinoids in vivo

    PubMed Central

    Dilworth, F. Jeffrey; Fromental-Ramain, Catherine; Remboutsika, Eumorphia; Benecke, Arndt; Chambon, Pierre

    1999-01-01

    All-trans and 9-cis retinoic acids (RA) signals are transduced by retinoic acid receptor/retinoid X receptor (RAR/RXR) heterodimers that act as functional units controlling the transcription of RA-responsive genes. With the aim of elucidating the underlying molecular mechanisms, we have developed an in vitro transcription system using a chromatin template made up of a minimal promoter and a direct repeat with 5-spacing-based RA response element. RARα and RXRα were expressed in and purified from baculovirus-infected Sf9 cells, and transcription was carried out by using naked DNA or chromatin templates. Transcription from naked templates was not affected by the presence of RA and/or RAR/RXR heterodimers. In contrast, very little transcription occurred from chromatin templates in the absence of RA or RAR/RXR heterodimers whereas their addition resulted in a dosage-dependent stimulation of transcription that never exceeded that occurring on naked DNA templates. Most importantly, the addition of synthetic agonistic or antagonistic retinoids to the chromatin transcription system mimicked their stimulatory or inhibitory action in vivo, and activation by a RXR-specific retinoid was subordinated to the binding of an agonist ligand to the RAR partner. Moreover, the addition of the p300 coactivator generated a synergistic enhancement of transcription. Thus, the dissection of this transcription system ultimately should lead to the elucidation of the molecular mechanisms by which RAR/RXR heterodimers control transcription in a ligand-dependent manner. PMID:10051583

  5. ATF3 inhibits PPARγ-stimulated transactivation in adipocyte cells

    SciTech Connect

    Jang, Min-Kyung; Jung, Myeong Ho

    2015-01-02

    Highlights: • ATF3 inhibits PPARγ-stimulated transcriptional activation. • ATF3 interacts with PPARγ. • ATF3 suppresses p300-mediated transcriptional coactivation. • ATF3 decreases the binding of PPARγ and recruitment of p300 to PPRE. - Abstract: Previously, we reported that activating transcription factor 3 (ATF3) downregulates peroxisome proliferator activated receptor (PPARγ) gene expression and inhibits adipocyte differentiation in 3T3-L1 cells. Here, we investigated another role of ATF3 on the regulation of PPARγ activity. ATF3 inhibited PPARγ-stimulated transactivation of PPARγ responsive element (PPRE)-containing reporter or GAL4/PPARγ chimeric reporter. Thus, ATF3 effectively repressed rosiglitazone-stimulated expression of adipocyte fatty acid binding protein (aP2), PPARγ target gene, in 3T3-L1 cells. Coimmunoprecipitation and GST pulldown assay demonstrated that ATF3 interacted with PPARγ. Accordingly, ATF3 prevented PPARγ from binding to PPRE on the aP2 promoter. Furthermore, ATF3 suppressed p300-mediated transcriptional coactivation of PPRE-containing reporter. Chromatin immunoprecipitation assay showed that overexpression of ATF3 blocked both binding of PPARγ and recruitment of p300 to PPRE on aP2 promoter induced by rosiglitazone treatment in 3T3-L1 cells. Taken together, these results suggest that ATF3 interacts with PPARγ and represses PPARγ-mediated transactivation through suppression of p300-stimulated coactivation in 3T3-L1 cells, which may play a role in inhibition of adipocyte differentiation.

  6. ROS inhibit the expression of testicular steroidogenic enzyme genes via the suppression of Nur77 transactivation.

    PubMed

    Lee, Seung-Yon; Gong, Eun-Yeung; Hong, Cheol Yi; Kim, Keon-Hee; Han, Jung-Soo; Ryu, Jae Chun; Chae, Ho Zoon; Yun, Chul-Ho; Lee, Keesook

    2009-12-01

    Steroidogenesis decreases with aging in the testis, whereas the levels of reactive oxygen species (ROS) increase. In addition, ROS have been reported to inhibit testicular steroidogenesis. Here, we investigated the effects of ROS on the transcriptional activity of Nur77, one of the major transcription factors that regulate the expression of steroidogenic enzyme genes. ROS signaling inhibited Nur77 transactivation, which was diminished by either treatment with c-Jun N-terminal kinase (JNK) inhibitor or the expression of a dominant negative form of JNK. This suggests the involvement of JNK signaling, which elevates the expression of c-Jun as well as its phosphorylation in Leydig cells. In transient transfection assays, c-Jun suppressed Nur77 transactivation in a dose-dependent manner. Further studies using c-Jun mutants revealed that the protein level of c-Jun, but not phosphorylation itself, was important for the suppression of Nur77 transactivation. Nur77 directly interacted with c-Jun in vivo, which blocked the DNA binding activity of Nur77. Together, these results suggest that ROS signaling-mediated c-Jun upregulation suppresses the expression of steroidogenic enzyme genes by inhibiting Nur77 transactivation, resulting in the reduction of testicular steroidogenesis. These findings may provide a mechanistic explanation for the age-related decline in testicular steroid hormone production. PMID:19751824

  7. Bovine HEXIM1 inhibits bovine immunodeficiency virus replication through regulating BTat-mediated transactivation

    PubMed Central

    2013-01-01

    The bovine immunodeficiency virus (BIV) transactivator (BTat) recruits the bovine cyclin T1 (B-cyclin T1) to the LTR to facilitate the transcription of BIV. Here, we demonstrate that bovine hexamethylene bisacetamide (HMBA)-induced protein 1 (BHEXIM1) inhibits BTat-mediated BIV LTR transcription. The results of in vivo and in vitro assays show direct binding of BHEXIM1 to the B-cyclin T1. These results suggest that the repression arises from BHEXIM1-BTat competition for B-cyclin T1, which allows BHEXIM1 to displace BTat from B-cyclin T1. Furthermore, we found that the C-terminal region and the centrally located region of BHEXIM1 are required for BHEXIM1 to associate with B-cyclin T1. Knockdown of BHEXIM1 enhances BIV replication. Taken together, our study provides the first clear evidence that BHEXIM1 is involved in BIV replication through regulating BTat-mediated transactivation. PMID:23537346

  8. Bovine HEXIM1 inhibits bovine immunodeficiency virus replication through regulating BTat-mediated transactivation.

    PubMed

    Guo, Hong-yan; Ma, Yong-gang; Gai, Yuan-ming; Liang, Zhi-bin; Ma, Jing; Su, Yang; Zhang, Qi-cheng; Chen, Qi-min; Tan, Juan

    2013-03-27

    The bovine immunodeficiency virus (BIV) transactivator (BTat) recruits the bovine cyclin T1 (B-cyclin T1) to the LTR to facilitate the transcription of BIV. Here, we demonstrate that bovine hexamethylene bisacetamide (HMBA)-induced protein 1 (BHEXIM1) inhibits BTat-mediated BIV LTR transcription. The results of in vivo and in vitro assays show direct binding of BHEXIM1 to the B-cyclin T1. These results suggest that the repression arises from BHEXIM1-BTat competition for B-cyclin T1, which allows BHEXIM1 to displace BTat from B-cyclin T1. Furthermore, we found that the C-terminal region and the centrally located region of BHEXIM1 are required for BHEXIM1 to associate with B-cyclin T1. Knockdown of BHEXIM1 enhances BIV replication. Taken together, our study provides the first clear evidence that BHEXIM1 is involved in BIV replication through regulating BTat-mediated transactivation.

  9. Baicalein exhibits anti-inflammatory effects via inhibition of NF-κB transactivation.

    PubMed

    Patwardhan, Raghavendra S; Sharma, Deepak; Thoh, Maikho; Checker, Rahul; Sandur, Santosh K

    2016-05-15

    NF-κB is a crucial mediator of inflammatory and immune responses and a number of phytochemicals that can suppress this immune-regulatory transcription factor are known to have promising anti-inflammatory potential. However, we report that inducer of pro-inflammatory transcription factor NF-κB functions as an anti-inflammatory agent. Our findings reveal that a plant derived flavonoid baicalein could suppress mitogen induced T cell activation, proliferation and cytokine secretion. Treatment of CD4+ T cells with baicalein prior to transfer in to lymphopenic allogenic host significantly suppressed graft versus host disease. Interestingly, addition of baicalein to murine splenic lymphocytes induced DNA binding of NF-κB but did not suppress Concanavalin A induced NF-κB. Since baicalein did not inhibit NF-κB binding to DNA, we hypothesized that baicalein may be suppressing NF-κB trans-activation. Thioredoxin system is implicated in the regulation of NF-κB trans-activation potential and therefore inhibition of thioredoxin system may be responsible for suppression of NF-κB dependent genes. Baicalein not only inhibited TrxR activity in cell free system but also suppressed mitogen induced thioredoxin activity in the nuclear compartment of lymphocytes. Similar to baicalein, pharmacological inhibitors of thioredoxin system also could suppress mitogen induced T cell proliferation without inhibiting DNA binding of NF-κB. Further, activation of cellular thioredoxin system by the use of pharmacological activator or over-expression of thioredoxin could abrogate the anti-inflammatory action of baicalein. We propose a novel strategy using baicalein to limit NF-κB dependent inflammatory responses via inhibition of thioredoxin system.

  10. Hydroxyurea inhibits the transactivation of the HIV-long-terminal repeat (LTR) promoter

    PubMed Central

    Calzado, M A; Macho, A; Lucena, C; Muñoz, E

    2000-01-01

    HIV-1 gene expression is regulated by the promoter/enhancer located within the U3 region of the proviral 5′ LTR that contains multiple potential cis-acting regulatory sites. Here we describe that the inhibitor of the cellular ribonucleoside reductase, hydroxyurea (HU), inhibited phorbol myristate acetate- or tumour necrosis factor-alpha-induced HIV-1-LTR transactivation in both lymphoid and non-lymphoid cells in a dose-dependent manner within the first 6 h of treatment, with a 50% inhibitory concentration of 0·5 mm. This inhibition was found to be specific for the HIV-1-LTR since transactivation of either an AP-1-dependent promoter or the CD69 gene promoter was not affected by the presence of HU. Moreover, gel-shift assays in 5.1 cells showed that HU prevented the binding of the NF-κB to the κB sites located in the HIV-1-LTR region, but it did not affect the binding of both the AP-1 and the Sp-1 transcription factors. By Western blots and cell cycle analyses we detected that HU induced a rapid dephosphorylation of the pRB, the product of the retinoblastoma tumour suppressor gene, and the cell cycle arrest was evident after 24 h of treatment. Thus, HU inhibits HIV-1 promoter activity by a novel pathway that implies an inhibition of the NF-κB binding to the LTR promoter. The present study suggests that HU may be useful as a potential therapeutic approach for inhibition of HIV-1 replication through different pathways. PMID:10792382

  11. Paeonol attenuates TNBS-induced colitis by inhibiting NF-{kappa}B and STAT1 transactivation

    SciTech Connect

    Ishiguro, Kazuhiro . E-mail: kio@med.nagoya-u.ac.jp; Ando, Takafumi; Maeda, Osamu; Hasegawa, Motofusa; Kadomatsu, Kenji; Ohmiya, Naoki; Niwa, Yasumasa; Xavier, Ramnik; Goto, Hidemi

    2006-11-15

    Paeonol, a major phenolic component of Moutan Cortex, is known to have anti-inflammatory activity. However, the effect of Paeonol on colitis has not been evaluated and the molecular mechanism of its anti-inflammatory action remains unknown. The aim of this study was to determine if Paeonol enema attenuates trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. We also investigated the effects of Paeonol in colon cancer-derived CW-2 cells and T cell leukemia-derived Jurkat cells treated with tumor necrosis factor {alpha} (TNF{alpha}) and/or interferon {gamma} (IFN{gamma}), which play critical roles in TNBS-induced colitis. Paeonol enema attenuated TNBS-induced colitis judging by body weigh reduction, colon length and histological score. Myeloperoxidase activity and inducible nitric oxide synthase (iNOS) production in the colon were also reduced with Paeonol enema. In CW-2 cells, Paeonol inhibited iNOS protein and mRNA expression induced by costimulation of TNF{alpha} and IFN{gamma}. Furthermore, Paeonol reduced TNF{alpha}-induced NF-{kappa}B transactivation and IFN{gamma}-induced STAT1 transactivation in CW-2 cells and also in Jurkat cells. These findings suggest that Paeonol enema may be useful for the treatment of colitis.

  12. DAX-1 (dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X-chromosome, gene 1) selectively inhibits transactivation but not transrepression mediated by the glucocorticoid receptor in a LXXLL-dependent manner.

    PubMed

    Zhou, Junguo; Oakley, Robert H; Cidlowski, John A

    2008-07-01

    The glucocorticoid receptor (GR) mediates virtually all actions of glucocorticoids, and the nature and magnitude of a cell's response to these steroids are determined primarily by hormone concentration and GR signaling capacity. DAX-1 (dosagesensitive sex reversal-adrenal hypoplasia congenita critical region on the X-chromosome, gene 1) is an orphan nuclear receptor that functions as a corepressor, and deletion or mutation of DAX-1 causes a decrease in glucocorticoid production. However it is unclear whether DAX-1 also alters GR function as a transcription factor. Here, we demonstrate that DAX-1 acts as a novel selective GR modulator. It specifically inhibits ligand-dependent GR transactivation with little effect on GR-mediated transrepression. As demonstrated by coimmunoprecipitation and glutathione- S-transferase pull-down assays, DAX-1 physically interacts with GR, but this interaction does not influence either ligand-induced GR nuclear translocation or subsequent GR association with glucocorticoid-responsive elements. Instead, DAX-1 competes with coactivators such as GR-interacting protein 1 for binding to the receptor. Specifically, suppression of GR transactivation is mediated by the N-terminal half of DAX-1, and in particular the LXXLL motifs. Thus we demonstrate that DAX-1 directly modulates GR signaling in addition to affecting glucocorticoid hormone levels. PMID:18417736

  13. Inhibition of Wilms tumor 1 transactivation by bone marrow zinc finger 2, a novel transcriptional repressor.

    PubMed

    Lee, Tae Ho; Lwu, Shelly; Kim, Jungho; Pelletier, Jerry

    2002-11-22

    The Wilms tumor suppressor gene, wt1, encodes a zinc finger transcription factor that has been implicated in the regulation of a number of genes. Protein-protein interactions are known to modulate the transcription regulatory functions of Wilms tumor (WT1) and have also implicated WT1 in splicing. In this report, we identify a novel WT1-interacting protein, bone marrow zinc finger 2 (BMZF2), by affinity chromatography utilizing immobilized WT1 protein. BMZF2 is a potential transcription factor with 18 zinc fingers. The BMZF2 mRNA is mainly expressed in fetal tissues, and the protein is predominantly nuclear. Co-immunoprecipitation experiments are consistent with an in vivo association between WT1 and BMZF2. Glutathione S-transferase pulldown assays and far Western blots revealed that zinc fingers VI-X (amino acids 231-370) are required for interaction with the zinc finger region of WT1. Functionally, BMZF2 inhibits transcriptional activation by WT1. Moreover, a chimeric protein generated by fusion of BMZF2 to the GAL4 DNA-binding domain significantly decreases promoter activity of a reporter containing GAL4 DNA-binding sites, suggesting the presence of an active repressor domain within BMZF2. Our results suggest that BMZF2 interferes with the transactivation potential of WT1. PMID:12239212

  14. Adenosine signaling inhibits CIITA-mediated MHC class II transactivation in lung fibroblast cells.

    PubMed

    Fang, Mingming; Xia, Jun; Wu, Xiaoyan; Kong, Hui; Wang, Hong; Xie, Weiping; Xu, Yong

    2013-08-01

    Efficient antigen presentation by major histocompatibility complex (MHC) molecules represents a critical process in adaptive immunity. Class II transactivator (CIITA) is considered the master regulator of MHC class II (MHC II) transcription. Previously, we have shown that CIITA expression is upregulated in smooth muscle cells deficient in A2b adenosine receptor. Here, we report that treatment with the adenosine receptor agonist adenosine-5'N-ethylcarboxamide (NECA) attenuated MHC II transcription in lung fibro-blast cells as a result of CIITA repression. Further analysis revealed that NECA preferentially abrogated CIITA transcription through promoters III and IV. Blockade with a selective A2b receptor antagonist MRS-1754 restored CIITA-dependent MHC II transactivation. Forskolin, an adenylyl cyclase activator, achieved the same effect as NECA. A2b signaling repressed CIITA transcription by altering histone modifications and recruitment of key factors on the CIITA promoters in a STAT1-dependent manner. MRS-1754 blocked the antagonism of transforming growth factor beta (TGF-β) in CIITA induction by interferon gamma (IFN-γ), alluding to a potential dialogue between TGF-β and adenosine signaling pathways. Finally, A2b signaling attenuated STAT1 phosphorylation and stimulated TGF-β synthesis. In conclusion, we have identified an adenosine-A2b receptor-adenylyl cyclase axis that influences CIITA-mediated MHC II transactivation in lung fibroblast cells and as such have provided invaluable insights into the development of novel immune-modulatory strategies.

  15. Caffeic acid phenethyl ester downregulates phospholipase D1 via direct binding and inhibition of NFκB transactivation

    SciTech Connect

    Park, Mi Hee; Kang, Dong Woo; Jung, Yunjin; Choi, Kang-Yell; Min, Do Sik

    2013-12-06

    Highlights: •We found CAFÉ, a natural product that suppresses expression and activity of PLD1. •CAPE decreased PLD1 expression by inhibiting NFκB transactivation. •CAPE rapidly inhibited PLD activity via its binding to a Cys837 of PLD1. •PLD1 downregulation by CAPE inhibited invasion and proliferation of glioma cells. -- Abstract: Upregulation of phospholipase D (PLD) is functionally linked with oncogenic signals and tumorigenesis. Caffeic acid phenethyl ester (CAPE) is an active compound of propolis extract that exhibits anti-proliferative, anti-inflammatory, anti-oxidant, and antineoplastic properties. In this study, we demonstrated that CAPE suppressed the expression of PLD1 at the transcriptional level via inhibition of binding of NFκB to PLD1 promoter. Moreover, CAPE, but not its analogs, bound to a Cys837 residue of PLD1 and inhibited enzymatic activity of PLD. CAPE also decreased activation of matrix metalloproteinases-2 induced by phosphatidic acid, a product of PLD activity. Ultimately, CAPE-induced downregulation of PLD1 suppressed invasion and proliferation of glioma cells. Taken together, the results of this study indicate that CAPE might contribute to anti-neoplastic effect by targeting PLD1.

  16. Transactivation of ErbB Family of Receptor Tyrosine Kinases Is Inhibited by Angiotensin-(1-7) via Its Mas Receptor

    PubMed Central

    Akhtar, Saghir; Chandrasekhar, Bindu; Attur, Sreeja; Dhaunsi, Gursev S.; Yousif, Mariam H. M.; Benter, Ibrahim F.

    2015-01-01

    Transactivation of the epidermal growth factor receptor (EGFR or ErbB) family members, namely EGFR and ErbB2, appears important in the development of diabetes-induced vascular dysfunction. Angiotensin-(1–7) [Ang-(1–7)] can prevent the development of hyperglycemia-induced vascular complications partly through inhibiting EGFR transactivation. Here, we investigated whether Ang-(1–7) can inhibit transactivation of ErbB2 as well as other ErbB receptors in vivo and in vitro. Streptozotocin-induced diabetic rats were chronically treated with Ang-(1–7) or AG825, a selective ErbB2 inhibitor, for 4 weeks and mechanistic studies performed in the isolated mesenteric vasculature bed as well as in cultured vascular smooth muscle cells (VSMCs). Ang-(1–7) or AG825 treatment inhibited diabetes-induced phosphorylation of ErbB2 receptor at tyrosine residues Y1221/22, Y1248, Y877, as well as downstream signaling via ERK1/2, p38 MAPK, ROCK, eNOS and IkB-α in the mesenteric vascular bed. In VSMCs cultured in high glucose (25 mM), Ang-(1–7) inhibited src-dependent ErbB2 transactivation that was opposed by the selective Mas receptor antagonist, D-Pro7-Ang-(1–7). Ang-(1–7) via Mas receptor also inhibited both Angiotensin II- and noradrenaline/norephinephrine-induced transactivation of ErbB2 and/or EGFR receptors. Further, hyperglycemia-induced transactivation of ErbB3 and ErbB4 receptors could be attenuated by Ang-(1–7) that could be prevented by D-Pro7-Ang-(1–7) in VSMC. These data suggest that Ang-(1–7) via its Mas receptor acts as a pan-ErbB inhibitor and might represent a novel general mechanism by which Ang-(1–7) exerts its beneficial effects in many disease states including diabetes-induced vascular complications. PMID:26536590

  17. Transactivation of ErbB Family of Receptor Tyrosine Kinases Is Inhibited by Angiotensin-(1-7) via Its Mas Receptor.

    PubMed

    Akhtar, Saghir; Chandrasekhar, Bindu; Attur, Sreeja; Dhaunsi, Gursev S; Yousif, Mariam H M; Benter, Ibrahim F

    2015-01-01

    Transactivation of the epidermal growth factor receptor (EGFR or ErbB) family members, namely EGFR and ErbB2, appears important in the development of diabetes-induced vascular dysfunction. Angiotensin-(1-7) [Ang-(1-7)] can prevent the development of hyperglycemia-induced vascular complications partly through inhibiting EGFR transactivation. Here, we investigated whether Ang-(1-7) can inhibit transactivation of ErbB2 as well as other ErbB receptors in vivo and in vitro. Streptozotocin-induced diabetic rats were chronically treated with Ang-(1-7) or AG825, a selective ErbB2 inhibitor, for 4 weeks and mechanistic studies performed in the isolated mesenteric vasculature bed as well as in cultured vascular smooth muscle cells (VSMCs). Ang-(1-7) or AG825 treatment inhibited diabetes-induced phosphorylation of ErbB2 receptor at tyrosine residues Y1221/22, Y1248, Y877, as well as downstream signaling via ERK1/2, p38 MAPK, ROCK, eNOS and IkB-α in the mesenteric vascular bed. In VSMCs cultured in high glucose (25 mM), Ang-(1-7) inhibited src-dependent ErbB2 transactivation that was opposed by the selective Mas receptor antagonist, D-Pro7-Ang-(1-7). Ang-(1-7) via Mas receptor also inhibited both Angiotensin II- and noradrenaline/norephinephrine-induced transactivation of ErbB2 and/or EGFR receptors. Further, hyperglycemia-induced transactivation of ErbB3 and ErbB4 receptors could be attenuated by Ang-(1-7) that could be prevented by D-Pro7-Ang-(1-7) in VSMC. These data suggest that Ang-(1-7) via its Mas receptor acts as a pan-ErbB inhibitor and might represent a novel general mechanism by which Ang-(1-7) exerts its beneficial effects in many disease states including diabetes-induced vascular complications. PMID:26536590

  18. Naked Polyamidoamine Polymers Intrinsically Inhibit Angiotensin II-Mediated EGFR and ErbB2 Transactivation in a Dendrimer Generation- and Surface Chemistry-Dependent Manner.

    PubMed

    Akhtar, Saghir; El-Hashim, Ahmed Z; Chandrasekhar, Bindu; Attur, Sreeja; Benter, Ibrahim F

    2016-05-01

    The effects of naked polyamidoamine (PAMAM) dendrimers on renin-angiotensin system (RAS) signaling via Angiotensin (Ang) II-mediated transactivation of the epidermal growth factor receptor (EGFR) and the closely related family member ErbB2 (HER2) were investigated. In primary aortic vascular smooth muscle cells, a cationic fifth-generation (G5) PAMAM dendrimer dose- and time-dependently inhibited Ang II/AT1 receptor-mediated transactivation of EGFR and ErbB2 as well as their downstream signaling via extracellular-regulated kinase 1/2 (ERK1/2). Inhibition even occurred at noncytotoxic concentrations at short (1 h) exposure times and was dependent on dendrimer generation (G7 > G6 > G5 > G4) and surface group chemistry (amino > carboxyl > hydroxyl). Mechanistically, the cationic G5 PAMAM dendrimer inhibited Ang II-mediated transactivation of EGFR and ErbB2 via inhibition of the nonreceptor tyrosine kinase Src. This novel, early onset, intrinsic biological action of PAMAM dendrimers as inhibitors of the Ang II/AT1/Src/EGFR-ErbB2/ERK1/2 signaling pathway could have important toxicological and pharmacological implications.

  19. Overexpression of ERβ is sufficient to inhibit hypoxia-inducible factor-1 transactivation

    SciTech Connect

    Park, Choa; Lee, YoungJoo

    2014-07-18

    Highlights: • We examined the effect of ERβ specific ligand on HIF-1 inhibition. • DPN down-regulates the ARNT protein levels in PC3 cells. • DPN did not show additional effect in ERβ transfected MCF-7 cells. • Our study shows that unliganded ERβ is sufficient to inhibit HIF-1 in systems of overexpression. - Abstract: Estrogen receptor (ER) β is predicted to play an important role in the prevention of breast cancer development and progression. We have previously shown that ERβ suppresses hypoxia inducible factor (HIF)-1-mediated transcription through aryl hydrocarbon receptor nuclear translocator (ARNT) degradation via ubiquitination processes. In this study, we attempted to examine the effect of ERβ specific ligand on HIF-1 inhibition in ERβ positive PC3 cells and ERβ transfected MCF-7 cells. ERβ specific agonist diarylpropionitrile (DPN) stimulated estrogen response element (ERE)-luciferase activity in a similar fashion to estradiol in PC3 cells. We observed that DPN down-regulates the ARNT protein levels leading to an attenuation of hypoxia-induced hypoxia response element (HRE)-driven luciferase reporter gene activation in PC3 cells. Treatment of DPN reduced vascular endothelial growth factor (VEGF) expression and co-treatment with ERβ specific antagonist PHTPP abrogated the effect in PC3 cells. We then examined the effect of DPN in ERβ transfected MCF-7 cells. HIF-1 transcriptional activity repression by ERβ was not further reduced by DPN, as examined by HRE-driven luciferase assays. Expression of ERβ significantly decreased VEGF secretion and ARNT expression under hypoxic conditions. However, DPN did not additionally affect this suppression in MCF-7 cells transfected with ERβ. This result shows that unliganded ERβ is sufficient to inhibit HIF-1 in systems of overexpression.

  20. Pax6 represses androgen receptor-mediated transactivation by inhibiting recruitment of the coactivator SPBP.

    PubMed

    Elvenes, Julianne; Thomassen, Ernst Ivan Simon; Johnsen, Sylvia Sagen; Kaino, Katrine; Sjøttem, Eva; Johansen, Terje

    2011-01-01

    The androgen receptor (AR) has a central role in development and maintenance of the male reproductive system and in the etiology of prostate cancer. The transcription factor Pax6 has recently been reported to act as a repressor of AR and to be hypermethylated in prostate cancer cells. SPBP is a transcriptional regulator that previously has been shown to enhance the activity of Pax6. In this study we have identified SPBP to act as a transcriptional coactivator of AR. We also show that Pax6 inhibits SPBP-mediated enhancement of AR activity on the AR target gene probasin promoter, a repression that was partly reversed by increased expression of SPBP. Enhanced expression of Pax6 reduced the amount of SPBP associated with the probasin promoter when assayed by ChIP in HeLa cells. We mapped the interaction between both AR and SPBP, and AR and Pax6 to the DNA-binding domains of the involved proteins. Further binding studies revealed that Pax6 and SPBP compete for binding to AR. These results suggest that Pax6 represses AR activity by displacing and/or inhibiting recruitment of coactivators to AR target promoters. Understanding the mechanism for inhibition of AR coactivators can give rise to molecular targeted drugs for treatment of prostate cancer. PMID:21935435

  1. Pax6 Represses Androgen Receptor-Mediated Transactivation by Inhibiting Recruitment of the Coactivator SPBP

    PubMed Central

    Johnsen, Sylvia Sagen; Kaino, Katrine; Sjøttem, Eva; Johansen, Terje

    2011-01-01

    The androgen receptor (AR) has a central role in development and maintenance of the male reproductive system and in the etiology of prostate cancer. The transcription factor Pax6 has recently been reported to act as a repressor of AR and to be hypermethylated in prostate cancer cells. SPBP is a transcriptional regulator that previously has been shown to enhance the activity of Pax6. In this study we have identified SPBP to act as a transcriptional coactivator of AR. We also show that Pax6 inhibits SPBP-mediated enhancement of AR activity on the AR target gene probasin promoter, a repression that was partly reversed by increased expression of SPBP. Enhanced expression of Pax6 reduced the amount of SPBP associated with the probasin promoter when assayed by ChIP in HeLa cells. We mapped the interaction between both AR and SPBP, and AR and Pax6 to the DNA-binding domains of the involved proteins. Further binding studies revealed that Pax6 and SPBP compete for binding to AR. These results suggest that Pax6 represses AR activity by displacing and/or inhibiting recruitment of coactivators to AR target promoters. Understanding the mechanism for inhibition of AR coactivators can give rise to molecular targeted drugs for treatment of prostate cancer. PMID:21935435

  2. Inhibition of {beta}-catenin-mediated transactivation by flavanone in AGS gastric cancer cells

    SciTech Connect

    Park, Chi Hoon; Hahm, Eun Ryeong; Lee, Ju Hyung; Jung, Kyung Chae; Yang, Chul Hak . E-mail: chulyang@plaza.snu.ac.kr

    2005-06-17

    Recently, data which prove that Wnt pathway activation may be an early event in multistep carcinogenesis in the stomach have been accumulating. We examined the effect of flavanone against {beta}-catenin/Tcf signaling in AGS gastric cancer cells. Reporter gene assay showed that flavanone inhibited {beta}-catenin/Tcf signaling efficiently. In addition, the inhibition of {beta}-catenin/Tcf signaling by flavanone in HEK293 cells transiently transfected with constitutively mutant {beta}-catenin gene, whose product is not phosphorylated by GSK3{beta}, indicates that its inhibitory mechanism was related to {beta}-catenin itself or downstream components. To investigate the precise inhibitory mechanism, we performed immunofluorescence, Western blot, and EMSA. As a result, our data revealed that there is no change of {beta}-catenin distribution and of nuclear {beta}-catenin levels through flavanone. In addition, the binding of Tcf complexes to DNA is not influenced by flavanone. The {beta}-catenin/Tcf transcriptional target gene cyclinD1 was downregulated by flavanone. These data suggest that flavanone inhibits the transcription of {beta}-catenin/Tcf responsive genes, by modulating Tcf activity without disrupting {beta}-catenin/Tcf complex formation.

  3. Transactivation of the TIEG1 confers growth inhibition of transforming growth factor-β-susceptible hepatocellular carcinoma cells

    PubMed Central

    Jiang, Lei; Lai, Yiu-Kay; Zhang, Jin-Fang; Chan, Chu-Yan; Lu, Gang; Lin, Marie CM; He, Ming-Liang; Li, Ji-Cheng; Kung, Hsiang-Fu

    2012-01-01

    AIM: To investigate the role of transforming growth factor (TGF)-β-inducible early gene 1 (TIEG1) in TGF-β-induced growth inhibition in hepatocellular carcinoma (HCC) cells. METHODS: Human hepatocyte and HCC cell lines with varied susceptibilities to TGF-β1 were tested by methylthiazoletetrazolium (MTT) assay. The expression changes of Smad2, Smad3, Smad4, Smad7, TIEG1 and TIEG2 gene following treatment with TGF-β1 in a TGF-β-sensitive hepatocyte cell line (MIHA), a TGF-β-sensitive hepatoma cell line (Hep3B) and two TGF-β-insensitive hepatoma cell lines (HepG2 and Bel7404) were examined. SiRNA targeting TIEG1 was transfected into Hep3B cells and the sensitivity of cells to TGF-β1 was examined. Overexpression of TIEG1 was induced by lentiviral-mediated transduction in TGF-β1-resistant hepatoma cell lines (Bel7404 and HepG2). MTT assay and 4’,6-Diamidino-2-phenylindole staining were used to identify cell viability and apoptosis, respectively. The expression level of stathmin was measured by reverse transcriptase polymerase chain reaction and Western-blotting analysis, and stathmin promoter activity by TIEG1 was monitored by a luciferase reporter gene system. RESULTS: TIEG1 was significantly upregulated by TGF-β1 in the TGF-β1-sensitive HCC cell line, Hep3B, but not in the resistant cell lines. The suppression of TIEG1 by siRNAs decreased the sensitivity of Hep3B cells to TGF-β1, whereas the overexpression of TIEG1 mediated growth inhibition and apoptosis in TGF-β1-resistant HCC cell lines, which resembled those of TGF-β1-sensitive HCC cells treated with TGF-β1. Our data further suggested that stathmin was a direct target of TIEG1, as stathmin was significantly downregulated by TIEG1 overexpression, and stathmin promoter activity was inhibited by TIEG1 in a dose-dependent manner. CONCLUSION: Our data suggest that transactivation of TIEG1 conferred growth inhibition of TGF-β-susceptible human HCC cells. PMID:22563190

  4. A peptide nucleic acid-aminosugar conjugate targeting transactivation response element of HIV-1 RNA genome shows a high bioavailability in human cells and strongly inhibits tat-mediated transactivation of HIV-1 transcription.

    PubMed

    Das, Indrajit; Désiré, Jérôme; Manvar, Dinesh; Baussanne, Isabelle; Pandey, Virendra N; Décout, Jean-Luc

    2012-07-12

    The 6-aminoglucosamine ring of the aminoglycoside antibiotic neomycin B (ring II) was conjugated to a 16-mer peptide nucleic acid (PNA) targeting HIV-1 TAR RNA. For this purpose, we prepared the aminoglucosamine monomer 15 and attached it to the protected PNA prior to its cleavage from the solid support. We found that the resulting PNA-aminoglucosamine conjugate is stable under acidic conditions, efficiently taken up by the human cells and fairly distributed in both cytosol and nucleus without endosomal entrapment because cotreatment with endosome-disrupting agent had no effect on its cellular distribution. The conjugate displayed very high target specificity in vitro and strongly inhibited Tat mediated transactivation of HIV-1 LTR transcription in a cell culture system. The unique properties of this new class of PNA conjugate suggest it to be a potential candidate for therapeutic application.

  5. A Peptide Nucleic Acid-Aminosugar Conjugate Targeting Transactivation Response Element of HIV-1 RNA Genome Shows a High Bioavailability in Human Cells and Strongly Inhibits Tat-mediated Transactivation of HIV-1 Transcription

    PubMed Central

    Das, Indrajit; Désiré, Jérôme; Manvar, Dinesh; Baussanne, Isabelle; Pandey, Virendra N.; Décout, Jean-Luc

    2012-01-01

    The 6-aminoglucosamine ring of the aminoglycoside antibiotic neomycin B (ring II) was conjugated to a 16 mer peptide nucleic acid (PNA) targeting HIV-1 TAR RNA. For this purpose we prepared the aminoglucosamine monomer 15 and attached it to the protected PNA prior to its cleavage from the solid support. We found that the resulting PNA-aminoglucosamine conjugate is stable under acidic condition, efficiently taken up by the human cells and fairly distributed in both cytosol and nucleus without endosomal entrapment since co-treatment with endosome-disrupting agent had no effect on its cellular distribution. The conjugate displayed very high target specificity in vitro and strongly inhibited Tat mediated transactivation of HIV-1 LTR transcription in cell culture system. The unique properties of this new class of PNA conjugate suggest it to be a potential candidate for therapeutic application. PMID:22698070

  6. Variant max protein, derived by alternative splicing, associates with c-Myc in vivo and inhibits transactivation

    SciTech Connect

    Arsura, M.; Deshpande, A.; Sonenshein, G.E.

    1995-12-01

    This report identifies a variant form of Myc-associated factor X (Max) protein, which plays a central role in the functional activity of c-Myc as a transcriptional activator. This variation, termed dMax, lacks the basic region as well as helix 1 and loop regions as a result of alternative splicing of max mRNA. This nuclear dMax was unable to bind E-box Myc site DNA but associated with c-Myc in vitro and in vivo and repressed transactivation. 42 refs., 8 figs.

  7. Inhibition of HIV-1 Tat-mediated LTR transactivation and HIV-1 infection by anti-Tat single chain intrabodies.

    PubMed Central

    Mhashilkar, A M; Bagley, J; Chen, S Y; Szilvay, A M; Helland, D G; Marasco, W A

    1995-01-01

    Genes encoding the rearranged immunoglobulin heavy and light chain variable regions of anti-HIV-1 Tat, exon 1 or exon 2 specific monoclonal antibodies have been used to construct single chain intracellular antibodies 'intrabodies' for expression in the cytoplasm of mammalian cells. These anti-Tat single chain intrabodies (anti-Tat sFvs) are additionally modified with a C-terminal human C kappa domain to increase cytoplasmic stability and/or the C-terminal SV40 nuclear localization signal to direct the nascent intrabody to the nuclear compartment, respectively. The anti-Tat sFvs with specific binding activity against the N-terminal activation domain of Tat, block Tat-mediated transactivation of HIV-1 LTR as well as intracellular trafficking of Tat in mammalian cells. As a result, the transformed lymphocytes expressing anti-Tat sFvs are resistant to HIV-1 infection. Thus, these studies demonstrate that stably expressed single chain intrabodies and their modified forms can effectively target molecules in the cytoplasm and nuclear compartments of eukaryotic cells. Furthermore, these studies suggest that anti-Tat sFvs used either alone or in combination with other genetically based strategies may be useful for the gene therapy of HIV-1 infection and AIDS. Images PMID:7537216

  8. Nickel(II) Complex of Polyhydroxybenzaldehyde N4-Thiosemicarbazone Exhibits Anti-Inflammatory Activity by Inhibiting NF-κB Transactivation

    PubMed Central

    Loh, Sheng Wei; Looi, Chung Yeng; Hassandarvish, Pouya; Phan, Alicia Yi Ling; Wong, Won Fen; Wang, Hao; Paterson, Ian C.; Ea, Chee Kwee; Mustafa, Mohd Rais; Maah, Mohd Jamil

    2014-01-01

    Background The biological properties of thiosemicarbazone have been widely reported. The incorporation of some transition metals such as Fe, Ni and Cu to thiosemicarbazone complexes is known to enhance its biological effects. In this study, we incorporated nickel(II) ions into thiosemicarbazone with N4-substitution groups H3L (H; H3L1, CH3; H3L2, C6H5; H3L3 and C2H5; H3L4) and examined its potential anti-inflammatory activity. Methodology/Principal Findings Four ligands (1–4) and their respective nickel-containing complexes (5–8) were synthesized and characterized. The compounds synthesized were tested for their effects on NF-κB nuclear translocation, pro-inflammatory cytokines secretion and NF-κB transactivation activity. The active compound was further evaluated on its ability to suppress carrageenan-induced acute inflammation in vivo. A potential binding target of the active compound was also predicted by molecular docking analysis. Conclusions/Significance Among all synthesized compounds tested, we found that complex [Ni(H2L1)(PPh3)]Cl (5) (complex 5), potently inhibited IκBα degradation and NF-κB p65 nuclear translocation in LPS-stimulated RAW264.7 cells as well as TNFα-stimulated HeLa S3 cells. In addition, complex 5 significantly down-regulated LPS- or TNFα-induced transcription of NF-κB target genes, including genes that encode the pro-inflammatory cytokines TNFα, IFNβ and IL6. Luciferase reporter assays confirmed that complex 5 inhibited the transactivation activity of NF-κB. Furthermore, the anti-inflammatory effect of complex 5 was also supported by its suppressive effect on carrageenan-induced paw edema formation in wild type C57BL/6 mice. Interestingly, molecular docking study showed that complex 5 potentially interact with the active site of IKKβ. Taken together, we suggest complex 5 as a novel NF-κB inhibitor with potent anti-inflammatory effects. PMID:24977407

  9. A conserved face of the Jagged/Serrate DSL domain is involved in Notch trans-activation and cis-inhibition.

    PubMed

    Cordle, Jemima; Johnson, Steven; Tay, Joyce Zi Yan; Roversi, Pietro; Wilkin, Marian B; de Madrid, Beatriz Hernández; Shimizu, Hideyuki; Jensen, Sacha; Whiteman, Pat; Jin, Boquan; Redfield, Christina; Baron, Martin; Lea, Susan M; Handford, Penny A

    2008-08-01

    The Notch receptor and its ligands are key components in a core metazoan signaling pathway that regulates the spatial patterning, timing and outcome of many cell-fate decisions. Ligands contain a disulfide-rich Delta/Serrate/LAG-2 (DSL) domain required for Notch trans-activation or cis-inhibition. Here we report the X-ray structure of a receptor binding region of a Notch ligand, the DSL-EGF3 domains of human Jagged-1 (J-1(DSL-EGF3)). The structure reveals a highly conserved face of the DSL domain, and we show, by functional analysis of Drosophila melanogster ligand mutants, that this surface is required for both cis- and trans-regulatory interactions with Notch. We also identify, using NMR, a surface of Notch-1 involved in J-1(DSL-EGF3) binding. Our data imply that cis- and trans-regulation may occur through the formation of structurally distinct complexes that, unexpectedly, involve the same surfaces on both ligand and receptor.

  10. Regulation of Inducible Nitric Oxide Synthase Expression by Viral A238L-Mediated Inhibition of p65/RelA Acetylation and p300 Transactivation

    PubMed Central

    Granja, Aitor G.; Sabina, Prado; Salas, María L.; Fresno, Manuel; Revilla, Yolanda

    2006-01-01

    Uncontrolled generation of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) can cause damage to host cells and inflammation, two undesirable events for virus spreading. African swine fever virus (ASFV) infection regulates iNOS-induced gene expression through the synthesis of the A238L virus protein. We here explored the role of A238L, an NF-κB and NFAT inhibitor, in the regulation of iNOS transcription in macrophages. NO production and iNOS mRNA and protein levels as well as iNOS promoter activity after lipopolysaccharide (LPS)-gamma interferon (IFN-γ) treatment were down-regulated both during ASFV infection and in Raw 264.7 cells stably expressing the viral protein. Overexpression of p300, but not of a histone acetyltransferase (HAT) defective mutant, reverted the A238L-mediated inhibition of both basal and LPS-IFN-γ-induced iNOS promoter activity. Following stimulation with LPS-IFN-γ, p65 and p300 interaction was abolished in Raw-A238L cells. Expression of A238L also inhibited p65/relA and p300 binding to the distal NF-κB sequence of the iNOS promoter together with p65 acetylation. Finally, A238L abrogated p300 transactivation mediated by a GAL4-p300 construction. These results provide evidence for an unique viral mechanism involved in transcriptional regulation of iNOS gene expression. PMID:17041221

  11. Triptonide Effectively Inhibits Wnt/β-Catenin Signaling via C-terminal Transactivation Domain of β-catenin.

    PubMed

    Chinison, Jessica; Aguilar, Jose S; Avalos, Alan; Huang, Ying; Wang, Zhijun; Cameron, D Joshua; Hao, Jijun

    2016-01-01

    Abnormal activation of canonical Wnt/β-catenin signaling is implicated in many diseases including cancer. As a result, therapeutic agents that disrupt this signaling pathway have been highly sought after. Triptonide is a key bioactive small molecule identified in a traditional Chinese medicine named Tripterygium wilfordii Hook F., and it has a broad spectrum of biological functions. Here we show that triptonide can effectively inhibit canonical Wnt/β-catenin signaling by targeting the downstream C-terminal transcription domain of β-catenin or a nuclear component associated with β-catenin. In addition, triptonide treatment robustly rescued the zebrafish "eyeless" phenotype induced by GSK-3β antagonist 6-bromoindirubin-30-oxime (BIO) for Wnt signaling activation during embryonic gastrulation. Finally, triptonide effectively induced apoptosis of Wnt-dependent cancer cells, supporting the therapeutic potential of triptonide. PMID:27596363

  12. Triptonide Effectively Inhibits Wnt/β-Catenin Signaling via C-terminal Transactivation Domain of β-catenin

    PubMed Central

    Chinison, Jessica; Aguilar, Jose S.; Avalos, Alan; Huang, Ying; Wang, Zhijun; Cameron, D. Joshua; Hao, Jijun

    2016-01-01

    Abnormal activation of canonical Wnt/β-catenin signaling is implicated in many diseases including cancer. As a result, therapeutic agents that disrupt this signaling pathway have been highly sought after. Triptonide is a key bioactive small molecule identified in a traditional Chinese medicine named Tripterygium wilfordii Hook F., and it has a broad spectrum of biological functions. Here we show that triptonide can effectively inhibit canonical Wnt/β-catenin signaling by targeting the downstream C-terminal transcription domain of β-catenin or a nuclear component associated with β-catenin. In addition, triptonide treatment robustly rescued the zebrafish “eyeless” phenotype induced by GSK-3β antagonist 6-bromoindirubin-30-oxime (BIO) for Wnt signaling activation during embryonic gastrulation. Finally, triptonide effectively induced apoptosis of Wnt-dependent cancer cells, supporting the therapeutic potential of triptonide. PMID:27596363

  13. In vivo screening of ligand-dependent hammerhead ribozymes.

    PubMed

    Saragliadis, Athanasios; Klauser, Benedikt; Hartig, Jörg S

    2012-01-01

    The development of artificial switches of gene expression is of high importance for future applications in biotechnology and synthetic biology. We have developed a powerful RNA-based system which allows for the ligand-dependent and reprogrammable control of gene expression in Escherichia coli. Our system makes use of the hammerhead ribozyme (HHR) which acts as molecular scaffold for the sequestration of the ribosome binding site (RBS), mimicking expression platforms in naturally occurring riboswitches. Aptamer domains can be attached to the ribozyme as exchangeable ligand-sensing modules. Addition of ligands to the bacterial growth medium changes the activity of the ligand-dependent self-cleaving ribozyme which in turn switches gene expression. In this chapter, we describe the in vivo screening procedure allowing for reprogramming the ligand-specificity of our system. PMID:22315086

  14. Inhibition of aryl hydrocarbon receptor transactivation and DNA adduct formation by CYP1 isoform-selective metabolic deactivation of benzo[a]pyrene

    SciTech Connect

    Endo, Kaori; Uno, Shigeyuki; Seki, Taiichiro; Ariga, Toyohiko; Kusumi, Yoshiaki; Mitsumata, Masako; Yamada, Sachiko; Makishima, Makoto

    2008-07-15

    Benzo[a]pyrene (BaP), a polyaromatic hydrocarbon produced by the combustion of cigarettes and coke ovens, is a known procarcinogen. BaP activates the aryl hydrocarbon receptor (AhR) and induces the expression of a battery of genes, including CYP1A1, which metabolize BaP to toxic compounds. The possible role of CYP1 enzymes in mediating BaP detoxification or metabolic activation remains to be elucidated. In this study, we assessed the effects of CYP1 enzymes (CYP1A1, CYP1A2 and CYP1B1) on BaP-induced AhR transactivation and DNA adduct formation in HEK293 cells and HepG2 cells. Transfection of CYP1A1 and CYP1B1, but not CYP1A2, suppressed BaP-induced activation of AhR. Expression of CYP1A1 and CYP1A2, but not CYP1B1, inhibited DNA adduct formation in BaP-treated HepG2 cells. These results indicate that CYP1A1 and CYP1B1 play a role in deactivation of BaP on AhR and that CYP1A1 and CYP1A2 are involved in BaP detoxification by suppressing DNA adduct formation. BaP treatment did not induce DNA adduct formation in HEK293 cells, even after transfection of CYP1 enzymes, suggesting that expression of CYP1 enzymes is not sufficient for DNA adduct formation. Lower expression of epoxide hydrolase and higher expression of glutathione S-transferase P1 (GSTP1) and GSTM1/M2 were observed in HEK293 cells compared with HepG2 cells. Dynamic expression of CYP1A1, CYP1A2 and CYP1B1 along with expression of other enzymes such as epoxide hydrolase and phase II enzymes may determine the detoxification or metabolic activation of BaP.

  15. Ligand- and coactivator-mediated transactivation function (AF2) of the androgen receptor ligand-binding domain is inhibited by the cognate hinge region.

    PubMed

    Wang, Q; Lu, J; Yong, E L

    2001-03-01

    Transactivation functions (AF2) in the ligand-binding domains (LBD) of many steroid receptors are well characterized, but there is little evidence to support such a function for the LBD of the androgen receptor (AR). We report a mutant AR, with residues 628-646 in the hinge region deleted, which exhibited transactivation activity that was more than double that of the wild type (WT) AR. Although no androgen-dependent AF2 activity could be observed for the WT ARLBD fused to a heterologous DNA-binding domain, the mutant ARLBD(Delta628-646) was 30-40 times more active than the WT ARLBD. In the presence of the p160 coactivator TIF2, AR(Delta628-646) was significantly more active than similarly treated WT AR. Deletion of residues 628-646 also enhanced TIF2-ARLBD activity 8-fold, an effect not present when the LBD-interacting LXXLL motifs of TIF2 were mutated, suggesting that the negative modulatory activity of residues 628-646 were exerted via coactivator pathways. Although the AP-1 (c-Jun/c-Fos) system and NcoR have been reported to interact with and repress the activity of some steroid receptors, c-Jun, c-Fos, c-Jun/c-Fos, nor NcoR function was consistently affected by the absence or presence of residues 628-646, implying that the AR hinge region exerts its silencing effects in a manner independent of these corepressors. Our data provide evidence for the novel finding that strong androgen-dependent AF2 exists in the ARLBD and is the first report of a negative regulatory domain in the AR. Because mutations in this region are commonly associated with prostate cancer, it is important to characterize the mechanisms by which the hinge region exerts its repressor effect on ligand-activated and coactivator-mediated AF2 activity of the ARLBD.

  16. Nepetaefuran and leonotinin isolated from Leonotis nepetaefolia R. Br. potently inhibit the LPS signaling pathway by suppressing the transactivation of NF-κB.

    PubMed

    Ueda, Fumihito; Iizuka, Keito; Tago, Kenji; Narukawa, Yuji; Kiuchi, Fumiyuki; Kasahara, Tadashi; Tamura, Hiroomi; Funakoshi-Tago, Megumi

    2015-10-01

    Leonotis nepetaefolia R. Br., also known as Klip Dagga or Lion's Ear, has traditionally been used as a folk medicine to treat inflammatory diseases such as rheumatism, bronchitis, and asthma; however, the components that exhibit its anti-inflammatory activity have not yet been identified. In the present study, we investigated the effects of three types of diterpenoids, nepetaefuran, leonotinin, and leonotin, which were isolated from L. nepetaefolia R. Br., on the LPS signaling pathway in order to elucidate the anti-inflammatory mechanism involved. Nepetaefuran more potently inhibited the LPS-induced production of NO and CCL2 than leonotinin by suppressing the expression of iNOS mRNA and CCL2 mRNA. On the other hand, leonotin failed to inhibit the production of NO and CCL2 induced by LPS. Although nepetaefuran and leonotinin had no effect on the LPS-induced degradation of IκBα or nuclear translocation of NF-κB p65, they markedly inhibited the transcriptional activity of NF-κB. Nepetaefuran and leonotinin also inhibited the transcriptional activity of the GAL4-NF-κB p65 fusion protein. On the other hand, nepetaefuran, leonotinin and leonotin did not affect the LPS-induced activation of MAP kinase family members such as ERK, p38, and JNK. In addition, inhibitory effect of nepetaefuran and leonotinin on NF-κB activation is well correlated with their ability to induce activation of Nrf2 and ER stress. Taken together, these results demonstrated that nepetaefuran and leonotinin could be the components responsible for the anti-inflammatory activity of L. nepetaefolia R. Br. by specifically inhibiting the LPS-induced activation of NF-κB. PMID:26319953

  17. Multiple, Ligand-Dependent Routes from the Active Site of Cytochrome P450 2C9

    SciTech Connect

    Cojocaru, Vlad; Winn, Peter J.; Wade, Rebecca C.

    2012-02-13

    The active site of liver-specific, drug-metabolizing cytochrome P450 (CYP) monooxygenases is deeply buried in the protein and is connected to the protein surface through multiple tunnels, many of which were found open in different CYP crystal structures. It has been shown that different tunnels could serve as ligand passage routes in different CYPs. However, it is not understood whether one CYP uses multiple routes for substrate access and product release and whether these routes depend on ligand properties. From 300 ns of molecular dynamics simulations of CYP2C9, the second most abundant CYP in the human liver we found four main ligand exit routes, the occurrence of each depending on the ligand type and the conformation of the F-G loop, which is likely to be affected by the CYP-membrane interaction. A non-helical F-G loop favored exit towards the putative membrane-embedded region. Important protein features that direct ligand exit include aromatic residues that divide the active site and whose motions control access to two pathways. The ligands interacted with positively charged residues on the protein surface through hydrogen bonds that appear to select for acidic substrates. The observation of multiple, ligand-dependent routes in a CYP aids understanding of how CYP mutations affect drug metabolism and provides new possibilities for CYP inhibition.

  18. Sigma-1 receptor activation inhibits osmotic swelling of rat retinal glial (Müller) cells by transactivation of glutamatergic and purinergic receptors.

    PubMed

    Vogler, Stefanie; Winters, Helge; Pannicke, Thomas; Wiedemann, Peter; Reichenbach, Andreas; Bringmann, Andreas

    2016-01-01

    Water accumulation in retinal glial (Müller) and neuronal cells resulting in cellular swelling contributes to the development of retinal edema and neurodegeneration. Sigma (σ) receptor activation is known to have neuroprotective effects in the retina. Here, we show that the nonselective σ receptor agonist ditolylguanidine, and the selective σ1 receptor agonist PRE-084, inhibit the osmotic swelling of Müller cell somata induced by superfusion of rat retinal slices with a hypoosmotic solution containing barium ions. In contrast, PRE-084 did not inhibit the osmotic swelling of bipolar cell somata. The effects of σ receptor agonists on the Müller cell swelling were abrogated in the presence of blockers of metabotropic glutamate and purinergic P2Y1 receptors, respectively, suggesting that σ receptor activation triggers activation of a glutamatergic-purinergic signaling cascade which is known to prevent the osmotic Müller cell swelling. The swelling-inhibitory effect of 17β-estradiol was prevented by the σ1 receptor antagonist BD1047, suggesting that the effect is mediated by σ1 receptor activation. The data may suggest that the neuroprotective effect of σ receptor activation in the retina is in part mediated by prevention of the cytotoxic swelling of retinal glial cells. PMID:26499958

  19. NF2 loss promotes oncogenic RAS-induced thyroid cancers via YAP-dependent transactivation of RAS proteins and sensitizes them to MEK inhibition

    PubMed Central

    Garcia-Rendueles, Maria E.R.; Ricarte-Filho, Julio C.; Untch, Brian R.; Landa, Iňigo; Knauf, Jeffrey A.; Voza, Francesca; Smith, Vicki E.; Ganly, Ian; Taylor, Barry S.; Persaud, Yogindra; Oler, Gisele; Fang, Yuqiang; Jhanwar, Suresh C.; Viale, Agnes; Heguy, Adriana; Huberman, Kety H.; Giancotti, Filippo; Ghossein, Ronald; Fagin, James A.

    2015-01-01

    Ch22q LOH is preferentially associated with RAS mutations in papillary and in poorly differentiated thyroid cancer (PDTC). The 22q tumor suppressor NF2, encoding merlin, is implicated in this interaction because of its frequent loss of function in human thyroid cancer cell lines. Nf2 deletion or Hras mutation are insufficient for transformation, whereas their combined disruption leads to murine PDTC with increased MAPK signaling. Merlin loss induces RAS signaling in part through inactivation of Hippo, which activates a YAP-TEAD transcriptional program. We find that the three RAS genes are themselves YAP-TEAD1 transcriptional targets, providing a novel mechanism of promotion of RAS-induced tumorigenesis. Moreover, pharmacological disruption of YAP-TEAD with verteporfin blocks RAS transcription and signaling, and inhibits cell growth. The increased MAPK output generated by NF2 loss in RAS-mutant cancers may inform therapeutic strategies, as it generates greater dependency on the MAPK pathway for viability. PMID:26359368

  20. Upregulating endogenous genes by an RNA-programmable artificial transactivator

    PubMed Central

    Fimiani, Cristina; Goina, Elisa; Mallamaci, Antonello

    2015-01-01

    To promote expression of endogenous genes ad libitum, we developed a novel, programmable transcription factor prototype. Kept together via an MS2 coat protein/RNA interface, it includes a fixed, polypeptidic transactivating domain and a variable RNA domain that recognizes the desired gene. Thanks to this device, we specifically upregulated five genes, in cell lines and primary cultures of murine pallial precursors. Gene upregulation was small, however sufficient to robustly inhibit neuronal differentiation. The transactivator interacted with target gene chromatin via its RNA cofactor. Its activity was restricted to cells in which the target gene is normally transcribed. Our device might be useful for specific applications. However for this purpose, it will require an improvement of its transactivation power as well as a better characterization of its target specificity and mechanism of action. PMID:26152305

  1. H11-H12 loop retinoic acid receptor mutants exhibit distinct trans-activating and trans-repressing activities in the presence of natural or synthetic retinoids.

    PubMed

    Lefebvre, B; Mouchon, A; Formstecher, P; Lefebvre, P

    1998-06-30

    Retinoids, such as the naturally occurring all-trans-retinoic acid (atRA) and synthetic ligand CD367 modulate ligand-dependent transcription through retinoic acid receptors (RARs). Retinoid binding to RAR is believed to trigger structural transitions in the ligand-binding domain (LBD), leading to helix H1 and helix H12 repositioning and coactivator recruitment and corepressor release. Here, we carried out a detailed mutagenesis analysis of the H11-H12 loop (designated the L box) to study its contribution to hRARalpha activation process. Point mutations that reduced transactivation by atRA also reduced atRA-induced transrepression of AP1 transcription, correlating ligand-induced activation and repression. However, a correlation was not observed with these mutations when tested with another ligand CD367, a synthetic agonist with binding properties identical to those of atRA. Transcription was strongly inhibited in the presence of CD367 for some mutants, thus leading to an inverse agonist activity of this ligand. None of these mutations significantly altered binding affinity for either ligand, indicating that altered transcription was not caused by altered ligand binding by these mutations. Although simple correlations with transcriptional activities were not found, these mutations were also characterized by altered ligand-induced structural transitions, which were distinct for the atRA-hRARalpha or CD367-hRARalpha complexes. These results indicate that amino acids in the L box are involved in specifying trans-repressive and trans-activating properties of the hRARalpha, and support the notion that different agonists induce distinct conformations in the LBD of the receptor.

  2. The Shine-Dalgarno sequence of riboswitch-regulated single mRNAs shows ligand-dependent accessibility bursts

    PubMed Central

    Rinaldi, Arlie J.; Lund, Paul E.; Blanco, Mario R.; Walter, Nils G.

    2016-01-01

    In response to intracellular signals in Gram-negative bacteria, translational riboswitches—commonly embedded in messenger RNAs (mRNAs)—regulate gene expression through inhibition of translation initiation. It is generally thought that this regulation originates from occlusion of the Shine-Dalgarno (SD) sequence upon ligand binding; however, little direct evidence exists. Here we develop Single Molecule Kinetic Analysis of RNA Transient Structure (SiM-KARTS) to investigate the ligand-dependent accessibility of the SD sequence of an mRNA hosting the 7-aminomethyl-7-deazaguanine (preQ1)-sensing riboswitch. Spike train analysis reveals that individual mRNA molecules alternate between two conformational states, distinguished by ‘bursts' of probe binding associated with increased SD sequence accessibility. Addition of preQ1 decreases the lifetime of the SD's high-accessibility (bursting) state and prolongs the time between bursts. In addition, ligand-jump experiments reveal imperfect riboswitching of single mRNA molecules. Such complex ligand sensing by individual mRNA molecules rationalizes the nuanced ligand response observed during bulk mRNA translation. PMID:26781350

  3. The Shine-Dalgarno sequence of riboswitch-regulated single mRNAs shows ligand-dependent accessibility bursts

    NASA Astrophysics Data System (ADS)

    Rinaldi, Arlie J.; Lund, Paul E.; Blanco, Mario R.; Walter, Nils G.

    2016-01-01

    In response to intracellular signals in Gram-negative bacteria, translational riboswitches--commonly embedded in messenger RNAs (mRNAs)--regulate gene expression through inhibition of translation initiation. It is generally thought that this regulation originates from occlusion of the Shine-Dalgarno (SD) sequence upon ligand binding; however, little direct evidence exists. Here we develop Single Molecule Kinetic Analysis of RNA Transient Structure (SiM-KARTS) to investigate the ligand-dependent accessibility of the SD sequence of an mRNA hosting the 7-aminomethyl-7-deazaguanine (preQ1)-sensing riboswitch. Spike train analysis reveals that individual mRNA molecules alternate between two conformational states, distinguished by `bursts' of probe binding associated with increased SD sequence accessibility. Addition of preQ1 decreases the lifetime of the SD's high-accessibility (bursting) state and prolongs the time between bursts. In addition, ligand-jump experiments reveal imperfect riboswitching of single mRNA molecules. Such complex ligand sensing by individual mRNA molecules rationalizes the nuanced ligand response observed during bulk mRNA translation.

  4. Ligand-dependent recruitment of the Arnt coregulator determines DNA recognition by the dioxin receptor

    SciTech Connect

    Whitelaw, M.; Pongratz, I.; Wilhelmsson, A.; Gustafsson, J.; Poellinger, L. )

    1993-04-01

    Signal transduction by dioxins is mediated by the intracellular dioxin or aryl hydrocarbon receptor. This receptor binds dioxin and its planar aromatic congeners in a saturable manner with high affinity. The extreme toxicity of dioxin has been demonstrated in animals but not in humans. In animals, dioxin causes thymic wasting, immune suppression, severe epithelial disorders and tumor promotion. On a molecular level, dioxins are inducers of transcription of a battery of target genes encoding xenobiotic metabolizing enzymes. Dioxin also appears to transcriptionally regulate the expression of the growth modulatory genes for interleukin-1 Beta and plasminogen activator inhibitor-2. The dioxin induction response is mediated by single or multiple copies of dioxin-inducible transcriptional control elements in target promoters. The research data detailed in this paper examines the ligand-dependent recruitment of the Arnt coregulator which determines DNA recognition by the dioxin receptor. This data suggests that dioxin receptor activity is governed by a complex pattern of combinatorial regulation involving repression by hsp90 and then by ligand-dependent recruitment of the positive coregulator Arnt and that the dioxin receptor system provides the first example of signal-controlled dimerization of bHLH factors.

  5. A structural view of ligand-dependent activation in thermoTRP channels

    PubMed Central

    Steinberg, Ximena; Lespay-Rebolledo, Carolyne; Brauchi, Sebastian

    2014-01-01

    Transient Receptor Potential (TRP) proteins are a large family of ion channels, grouped into seven sub-families. Although great advances have been made regarding the activation and modulation of TRP channel activity, detailed molecular mechanisms governing TRP channel gating are still needed. Sensitive to electric, chemical, mechanical, and thermal cues, TRP channels are tightly associated with the detection and integration of sensory input, emerging as a model to study the polymodal activation of ion channel proteins. Among TRP channels, the temperature-activated kind constitute a subgroup by itself, formed by Vanilloid receptors 1–4, Melastatin receptors 2, 4, 5, and 8, TRPC5, and TRPA1. Some of the so-called “thermoTRP” channels participate in the detection of noxious stimuli making them an interesting pharmacological target for the treatment of pain. However, the poor specificity of the compounds available in the market represents an important obstacle to overcome. Understanding the molecular mechanics underlying ligand-dependent modulation of TRP channels may help with the rational design of novel synthetic analgesics. The present review focuses on the structural basis of ligand-dependent activation of TRPV1 and TRPM8 channels. Special attention is drawn to the dissection of ligand-binding sites within TRPV1, PIP2-dependent modulation of TRP channels, and the structure of natural and synthetic ligands. PMID:24847275

  6. Ligand-Independent Activation of Platelet-Derived Growth Factor Receptor β during Human Immunodeficiency Virus-Transactivator of Transcription and Cocaine-Mediated Smooth Muscle Hyperplasia.

    PubMed

    Dalvi, Pranjali N; Gupta, Vijayalaxmi G; Griffin, Brooke R; O'Brien-Ladner, Amy; Dhillon, Navneet K

    2015-09-01

    Our previous study supports an additive effect of cocaine to human immunodeficiency virus infection in the development of pulmonary arteriopathy through enhancement of proliferation of pulmonary smooth muscle cells (SMCs), while also suggesting involvement of platelet-derived growth factor receptor (PDGFR) activation in the absence of further increase in PDGF-BB ligand. Redox-related signaling pathways have been shown to regulate tyrosine kinase receptors independent of ligand binding, so we hypothesized that simultaneous treatment of SMCs with transactivator of transcription (Tat) and cocaine may be able to indirectly activate PDGFR through modulation of reactive oxygen species (ROS) without the need for PDGF binding. We found that blocking the binding of ligand using suramin or monoclonal IMC-3G3 antibody significantly reduced ligand-induced autophosphorylation of Y1009 without affecting ligand-independent transphosphorylation of Y934 residue on PDGFRβ in human pulmonary arterial SMCs treated with both cocaine and Tat. Combined treatment of human pulmonary arterial SMCs with cocaine and Tat resulted in augmented production of superoxide radicals and hydrogen peroxide when compared with either treatment alone. Inhibition of this ROS generation prevented cocaine- and Tat-mediated Src activation and transphosphorylation of PDGFRβ at Y934 without any changes in phosphorylation of Y1009, in addition to attenuation of smooth muscle hyperplasia. Furthermore, pretreatment with an Src inhibitor, PP2, also suppressed cocaine- and Tat-mediated enhanced Y934 phosphorylation and smooth muscle proliferation. Finally, we report total abrogation of cocaine- and Tat-mediated synergistic increase in cell proliferation on inhibition of both ligand-dependent and ROS/Src-mediated ligand-independent phosphorylation of PDGFRβ.

  7. Ligand-dependent repression of the erythroid transcription factor GATA-1 by the estrogen receptor.

    PubMed Central

    Blobel, G A; Sieff, C A; Orkin, S H

    1995-01-01

    High-dose estrogen administration induces anemia in mammals. In chickens, estrogens stimulate outgrowth of bone marrow-derived erythroid progenitor cells and delay their maturation. This delay is associated with down-regulation of many erythroid cell-specific genes, including alpha- and beta-globin, band 3, band 4.1, and the erythroid cell-specific histone H5. We show here that estrogens also reduce the number of erythroid progenitor cells in primary human bone marrow cultures. To address potential mechanisms by which estrogens suppress erythropoiesis, we have examined their effects on GATA-1, an erythroid transcription factor that participates in the regulation of the majority of erythroid cell-specific genes and is necessary for full maturation of erythrocytes. We demonstrate that the transcriptional activity of GATA-1 is strongly repressed by the estrogen receptor (ER) in a ligand-dependent manner and that this repression is reversible in the presence of 4-hydroxytamoxifen. ER-mediated repression of GATA-1 activity occurs on an artificial promoter containing a single GATA-binding site, as well as in the context of an intact promoter which is normally regulated by GATA-1. GATA-1 and ER bind to each other in vitro in the absence of DNA. In coimmunoprecipitation experiments using transfected COS cells, GATA-1 and ER associate in a ligand-dependent manner. Mapping experiments indicate that GATA-1 and the ER form at least two contacts, which involve the finger region and the N-terminal activation domain of GATA-1. We speculate that estrogens exert effects on erythropoiesis by modulating GATA-1 activity through protein-protein interaction with the ER. Interference with GATA-binding proteins may be one mechanism by which steroid hormones modulate cellular differentiation. PMID:7760810

  8. Functional evidence for ligand-dependent dissociation of thyroid hormone and retinoic acid receptors from an inhibitory cellular factor.

    PubMed Central

    Casanova, J; Helmer, E; Selmi-Ruby, S; Qi, J S; Au-Fliegner, M; Desai-Yajnik, V; Koudinova, N; Yarm, F; Raaka, B M; Samuels, H H

    1994-01-01

    The ligand-binding domains of thyroid hormone (L-triiodothyronine [T3]) receptors (T3Rs), all-trans retinoic acid (RA) receptors (RARs), and 9-cis RA receptors (RARs and RXRs) contain a series of heptad motifs thought to be important for dimeric interactions. Using a chimera containing amino acids 120 to 392 of chicken T3R alpha (cT3R alpha) positioned between the DNA-binding domain of the yeast GAL4 protein and the potent 90-amino-acid transactivating domain of the herpes simplex virus VP16 protein (GAL4-T3R-VP16), we provide functional evidence that binding of ligand releases T3Rs and RARs from an inhibitory cellular factor. GAL4-T3R-VP16 does not bind T3 and does not activate transcription from a GAL4 reporter when expressed alone but is able to activate transcription when coexpressed with unliganded T3R or RAR. This activation is reversed by T3 or RA, suggesting that these receptors compete with GAL4-T3R-VP16 for a cellular inhibitor and that ligand reverses this effect by dissociating T3R or RAR from the inhibitor. A chimera containing the entire ligand-binding domain of cT3R alpha (amino acids 120 to 408) linked to VP16 [GAL4-T3R(408)-VP16] is activated by unliganded receptor as well as by T3. In contrast, GAL4-T3R containing the amino acid 120 to 408 ligand-binding region without the VP16 domain is activated only by T3. The highly conserved ninth heptad, which is involved in heterodimerization, appears to participate in the receptor-inhibitor interaction, suggesting that the inhibitor is a related member of the receptor gene family. In striking contrast to T3R and RAR, RXR activates GAL4-T3R-VP16 only with its ligand, 9-cis RA, but unliganded RXR does not appear to be the inhibitor suggested by these studies. Further evidence that an orphan receptor may be the inhibitor comes from our finding that COUP-TF inhibits activation of GAL4-T3R-VP16 by unliganded T3R and the activation of GAL4-T3R by T3. These and other results suggest that an inhibitory factor

  9. Epidermal Growth Factor Receptor Transactivation: Mechanisms, Pathophysiology, and Potential Therapies in the Cardiovascular System.

    PubMed

    Forrester, Steven J; Kawai, Tatsuo; O'Brien, Shannon; Thomas, Walter; Harris, Raymond C; Eguchi, Satoru

    2016-01-01

    Epidermal growth factor receptor (EGFR) activation impacts the physiology and pathophysiology of the cardiovascular system, and inhibition of EGFR activity is emerging as a potential therapeutic strategy to treat diseases including hypertension, cardiac hypertrophy, renal fibrosis, and abdominal aortic aneurysm. The capacity of G protein-coupled receptor (GPCR) agonists, such as angiotensin II (AngII), to promote EGFR signaling is called transactivation and is well described, yet delineating the molecular processes and functional relevance of this crosstalk has been challenging. Moreover, these critical findings are dispersed among many different fields. The aim of our review is to highlight recent advancements in defining the signaling cascades and downstream consequences of EGFR transactivation in the cardiovascular renal system. We also focus on studies that link EGFR transactivation to animal models of the disease, and we discuss potential therapeutic applications.

  10. Multiple Mechanisms Are Responsible for Transactivation of the Epidermal Growth Factor Receptor in Mammary Epithelial Cells*

    PubMed Central

    Rodland, Karin D.; Bollinger, Nikki; Ippolito, Danielle; Opresko, Lee K.; Coffey, Robert J.; Zangar, Richard; Wiley, H. Steven

    2008-01-01

    The number of distinct signaling pathways that can transactivate the epidermal growth factor receptor (EGFR) in a single cell type is unclear. Using a single strain of human mammary epithelial cells, we found that a wide variety of agonists, such as lysophosphatidic acid (LPA), uridine triphosphate, growth hormone, vascular endothelial growth factor, insulin-like growth factor-1 (IGF-1), and tumor necrosis factor-α, require EGFR activity to induce ERK phosphorylation. In contrast, hepatocyte growth factor can stimulate ERK phosphorylation independent of the EGFR. EGFR transactivation also correlated with an increase in cell proliferation and could be inhibited with metalloprotease inhibitors. However, there were significant differences with respect to transactivation kinetics and sensitivity to different inhibitors. In particular, IGF-1 displayed relatively slow transactivation kinetics and was resistant to inhibition by the selective ADAM-17 inhibitor WAY-022 compared with LPA-induced transactivation. Studies using anti-ligand antibodies showed that IGF-1 transactivation required amphiregulin production, whereas LPA was dependent on multiple ligands. Direct measurement of ligand shedding confirmed that LPA treatment stimulated shedding of multiple EGFR ligands, but paradoxically, IGF-1 had little effect on the shedding rate of any ligand, including amphiregulin. Instead, IGF-1 appeared to work by enhancing EGFR activation of Ras in response to constitutively produced amphiregulin. This enhancement of EGFR signaling was independent of both receptor phosphorylation and PI-3-kinase activity, suggestive of a novel mechanism. Our studies demonstrate that within a single cell type, the EGFR autocrine system can couple multiple signaling pathways to ERK activation and that this modulation of EGFR autocrine signaling can be accomplished at multiple regulatory steps. PMID:18782770

  11. Sensitivity analysis of retrovirus HTLV-1 transactivation.

    PubMed

    Corradin, Alberto; Di Camillo, Barbara; Ciminale, Vincenzo; Toffolo, Gianna; Cobelli, Claudio

    2011-02-01

    Human T-cell leukemia virus type 1 is a human retrovirus endemic in many areas of the world. Although many studies indicated a key role of the viral protein Tax in the control of viral transcription, the mechanisms controlling HTLV-1 expression and its persistence in vivo are still poorly understood. To assess Tax effects on viral kinetics, we developed a HTLV-1 model. Two parameters that capture both its deterministic and stochastic behavior were quantified: Tax signal-to-noise ratio (SNR), which measures the effect of stochastic phenomena on Tax expression as the ratio between the protein steady-state level and the variance of the noise causing fluctuations around this value; t(1/2), a parameter representative of the duration of Tax transient expression pulses, that is, of Tax bursts due to stochastic phenomena. Sensitivity analysis indicates that the major determinant of Tax SNR is the transactivation constant, the system parameter weighting the enhancement of retrovirus transcription due to transactivation. In contrast, t(1/2) is strongly influenced by the degradation rate of the mRNA. In addition to shedding light into the mechanism of Tax transactivation, the obtained results are of potential interest for novel drug development strategies since the two parameters most affecting Tax transactivation can be experimentally tuned, e.g. by perturbing protein phosphorylation and by RNA interference.

  12. Ligand-dependent localization and function of ORP-VAP complexes at membrane contact sites.

    PubMed

    Weber-Boyvat, Marion; Kentala, Henriikka; Peränen, Johan; Olkkonen, Vesa M

    2015-05-01

    Oxysterol-binding protein/OSBP-related proteins (ORPs) constitute a conserved family of sterol/phospholipid-binding proteins with lipid transporter or sensor functions. We investigated the spatial occurrence and regulation of the interactions of human OSBP/ORPs or the S. cerevisiae orthologs, the Osh (OSBP homolog) proteins, with their endoplasmic reticulum (ER) anchors, the VAMP-associated proteins (VAPs), by employing bimolecular fluorescence complementation and pull-down set-ups. The ORP-VAP interactions localize frequently at distinct subcellular sites, shown in several cases to represent membrane contact sites (MCSs). Using established ORP ligand-binding domain mutants and pull-down assays with recombinant proteins, we show that ORP liganding regulates the ORP-VAP association, alters the subcellular targeting of ORP-VAP complexes, or modifies organelle morphology. There is distinct protein specificity in the effects of the mutants on subcellular targeting of ORP-VAP complexes. We provide evidence that complexes of human ORP2 and VAPs at ER-lipid droplet interfaces regulate the hydrolysis of triglycerides and lipid droplet turnover. The data suggest evolutionarily conserved, complex ligand-dependent functions of ORP-VAP complexes at MCSs, with implications for cellular lipid homeostasis and signaling.

  13. Transcriptional activation by the thyroid hormone receptor through ligand-dependent receptor recruitment and chromatin remodelling.

    PubMed

    Grøntved, Lars; Waterfall, Joshua J; Kim, Dong Wook; Baek, Songjoon; Sung, Myong-Hee; Zhao, Li; Park, Jeong Won; Nielsen, Ronni; Walker, Robert L; Zhu, Yuelin J; Meltzer, Paul S; Hager, Gordon L; Cheng, Sheue-yann

    2015-01-01

    A bimodal switch model is widely used to describe transcriptional regulation by the thyroid hormone receptor (TR). In this model, the unliganded TR forms stable, chromatin-bound complexes with transcriptional co-repressors to repress transcription. Binding of hormone dissociates co-repressors and facilitates recruitment of co-activators to activate transcription. Here we show that in addition to hormone-independent TR occupancy, ChIP-seq against endogenous TR in mouse liver tissue demonstrates considerable hormone-induced TR recruitment to chromatin associated with chromatin remodelling and activated gene transcription. Genome-wide footprinting analysis using DNase-seq provides little evidence for TR footprints both in the absence and presence of hormone, suggesting that unliganded TR engagement with repressive complexes on chromatin is, similar to activating receptor complexes, a highly dynamic process. This dynamic and ligand-dependent interaction with chromatin is likely shared by all steroid hormone receptors regardless of their capacity to repress transcription in the absence of ligand. PMID:25916672

  14. Transcriptional activation by the thyroid hormone receptor through ligand-dependent receptor recruitment and chromatin remodelling.

    PubMed

    Grøntved, Lars; Waterfall, Joshua J; Kim, Dong Wook; Baek, Songjoon; Sung, Myong-Hee; Zhao, Li; Park, Jeong Won; Nielsen, Ronni; Walker, Robert L; Zhu, Yuelin J; Meltzer, Paul S; Hager, Gordon L; Cheng, Sheue-yann

    2015-01-01

    A bimodal switch model is widely used to describe transcriptional regulation by the thyroid hormone receptor (TR). In this model, the unliganded TR forms stable, chromatin-bound complexes with transcriptional co-repressors to repress transcription. Binding of hormone dissociates co-repressors and facilitates recruitment of co-activators to activate transcription. Here we show that in addition to hormone-independent TR occupancy, ChIP-seq against endogenous TR in mouse liver tissue demonstrates considerable hormone-induced TR recruitment to chromatin associated with chromatin remodelling and activated gene transcription. Genome-wide footprinting analysis using DNase-seq provides little evidence for TR footprints both in the absence and presence of hormone, suggesting that unliganded TR engagement with repressive complexes on chromatin is, similar to activating receptor complexes, a highly dynamic process. This dynamic and ligand-dependent interaction with chromatin is likely shared by all steroid hormone receptors regardless of their capacity to repress transcription in the absence of ligand.

  15. Ligand-dependent localization and function of ORP-VAP complexes at membrane contact sites.

    PubMed

    Weber-Boyvat, Marion; Kentala, Henriikka; Peränen, Johan; Olkkonen, Vesa M

    2015-05-01

    Oxysterol-binding protein/OSBP-related proteins (ORPs) constitute a conserved family of sterol/phospholipid-binding proteins with lipid transporter or sensor functions. We investigated the spatial occurrence and regulation of the interactions of human OSBP/ORPs or the S. cerevisiae orthologs, the Osh (OSBP homolog) proteins, with their endoplasmic reticulum (ER) anchors, the VAMP-associated proteins (VAPs), by employing bimolecular fluorescence complementation and pull-down set-ups. The ORP-VAP interactions localize frequently at distinct subcellular sites, shown in several cases to represent membrane contact sites (MCSs). Using established ORP ligand-binding domain mutants and pull-down assays with recombinant proteins, we show that ORP liganding regulates the ORP-VAP association, alters the subcellular targeting of ORP-VAP complexes, or modifies organelle morphology. There is distinct protein specificity in the effects of the mutants on subcellular targeting of ORP-VAP complexes. We provide evidence that complexes of human ORP2 and VAPs at ER-lipid droplet interfaces regulate the hydrolysis of triglycerides and lipid droplet turnover. The data suggest evolutionarily conserved, complex ligand-dependent functions of ORP-VAP complexes at MCSs, with implications for cellular lipid homeostasis and signaling. PMID:25420878

  16. Sox5 induces epithelial to mesenchymal transition by transactivation of Twist1

    SciTech Connect

    Pei, Xin-Hong; Lv, Xin-Quan; Li, Hui-Xiang

    2014-03-28

    Highlights: • Depletion of Sox5 inhibits breast cancer proliferation, migration, and invasion. • Sox5 transactivates Twist1 expression. • Sox5 induces epithelial to mesenchymal transition through transactivation of Twist1 expression. - Abstract: The epithelial to mesenchymal transition (EMT), a highly conserved cellular program, plays an important role in normal embryogenesis and cancer metastasis. Twist1, a master regulator of embryonic morphogenesis, is overexpressed in breast cancer and contributes to metastasis by promoting EMT. In exploring the mechanism underlying the increased Twist1 in breast cancer cells, we found that the transcription factor SRY (sex-determining region Y)-box 5(Sox5) is up-regulation in breast cancer cells and depletion of Sox5 inhibits breast cancer cell proliferation, migration, and invasion. Furthermore, depletion of Sox5 in breast cancer cells caused a dramatic decrease in Twist1 and chromosome immunoprecipitation assay showed that Sox5 can bind directly to the Twist1 promoter, suggesting that Sox5 transactivates Twist1 expression. We further demonstrated that knockdown of Sox5 up-regulated epithelial phenotype cell biomarker (E-cadherin) and down-regulated mesenchymal phenotype cell biomarkers (N-cadherin, Vimentin, and Fibronectin 1), resulting in suppression of EMT. Our study suggests that Sox5 transactivates Twist1 expression and plays an important role in the regulation of breast cancer progression.

  17. Ligand-dependent EphB1 signaling suppresses glioma invasion and correlates with patient survival

    PubMed Central

    Teng, Lei; Nakada, Mitsutoshi; Furuyama, Natsuki; Sabit, Hemragul; Furuta, Takuya; Hayashi, Yutaka; Takino, Takahisa; Dong, Yu; Sato, Hiroshi; Sai, Yoshimichi; Miyamoto, Ken-ichi; Berens, Michael E.; Zhao, Shi-Guang; Hamada, Jun-Ichiro

    2013-01-01

    Background Extensive evidence implicates the Eph receptor family of tyrosine kinases and its ligand, ephrin, in glioma invasion, but it remains incompletely understood how these receptors affect chemotactic behavior of glioma. We sought to identify the Eph family members that correlate with patients' survival and to reveal the function of Eph in glioma invasion. Methods Clinical relevance of EphB genes was confirmed in a clinically annotated expression data set of 195 brain biopsy specimens. The function of EphB was analyzed in vitro and in vivo. Results Levels of mRNA of certain EphB members were significantly different in histological grades of glioma. According to Kaplan–Meier analysis, only the EphB1 level among 5 members of EphB emerged to be a powerful predictor of favorable survival in malignant glioma (n = 97, P = .0048), although the levels of EphB1 expression did not vary across the tumor grades. Immunoprecipitation showed that tyrosine phosphorylated EphB1 was not detected in all glioma cells tested. Forced overexpression and autophosphorylation of EphB1 in low expressor cell lines (U251, U87) did not affect cell migration or invasion in vitro, whereas EphB1 phosphorylation induced by ephrin-B2/Fc significantly decreased migration and invasion. Cells expressing ephrin-B2 showed noteworthy morphological changes consistent with migration induction; this alteration was negated by EphB1 overexpression. Concomitantly, overexpression of EphB1 abrogated the increased migration and invasion induced by ephrin-B2 in vitro and in vivo. Conclusions These data suggest that ligand-dependent EphB1 signaling negatively regulates glioma cell invasion, identifying EphB1 as a favorable prognostic factor in malignant glioma. PMID:24121831

  18. Coactivators p300 and PCAF physically and functionally interact with the foamy viral trans-activator

    PubMed Central

    Bannert, Helmut; Muranyi, Walter; Ogryzko, Vasily V; Nakatani, Yoshihiro; Flügel, Rolf M

    2004-01-01

    Background Foamy virus Bel1/Tas trans-activators act as key regulators of gene expression and directly bind to Bel1 response elements (BRE) in both the internal and the 5'LTR promoters leading to strong transcriptional trans-activation. Cellular coactivators interacting with Bel1/Tas are unknown to date. Results Transient expression assays, co-immunoprecipitation experiments, pull-down assays, and Western blot analysis were used to demonstrate that the coactivator p300 and histone acetyltransferase PCAF specifically interact with the retroviral trans-activator Bel1/Tas in vivo. Here we show that the Bel1/Tas-mediated trans-activation was enhanced by the coactivator p300, histone acetyltransferases PCAF and SRC-1 based on the crucial internal promoter BRE. The Bel1/Tas-interacting region was mapped to the C/H1 domain of p300 by co-immunoprecipitation and pull-down assays. In contrast, coactivator SRC-1 previously reported to bind to the C-terminal domain of p300 did not directly interact with the Bel1 protein but nevertheless enhanced Bel1/Tas-mediated trans-activation. Cotransfection of Bel1/Tas and p300C with an expression plasmid containing the C/H1domain partially inhibited the p300C-driven trans-activation. Conclusions Our data identify p300 and PCAF as functional partner molecules that directly interact with Bel1/Tas. Since the acetylation activities of the three coactivators reside in or bind to the C-terminal regions of p300, a C/H1 expression plasmid was used as inhibitor. This is the first report of a C/H1 domain-interacting retroviral trans-activator capable of partially blocking the strong Bel1/Tas-mediated activation of the C-terminal region of coactivator p300. The potential mechanisms and functional roles of the three histone and factor acetyltransferases p300, PCAF, and SRC-1 in Bel1/Tas-mediated trans-activation are discussed. PMID:15350211

  19. ERK2 phosphorylation of EBNA1 serine 383 residue is important for EBNA1-dependent transactivation

    PubMed Central

    Lee, Eun Kyung; Choi, Eun Young; Kang, Myung-Soo

    2016-01-01

    Functional inhibition of Epstein-Barr virus (EBV)-encoded nuclear antigen 1 (EBNA1) can cause the death of EBV infected cells. In this study, a bioinformatics tool predicted the existence of putative extracellular signal-regulated kinase (ERK) docking and substrate consensus sites on EBNA1, suggesting that ERK2 could bind to and phosphorylate EBNA1. In accordance, ERK2 was found to phosphorylate EBNA1 serine 383 in a reaction suppressed by H20 (a structural congener of the ERK inhibitor), U0126 (an inhibitor of MEK kinase), and mutations at substrate (S383A) or putative ERK docking sites. Wild-type (S383) and phosphomimetic (S383D) EBNA1 demonstrated comparable transactivation function, which was suppressed by H20 or U0126. In contrast, non-phosphorylated EBNA1 mutants displayed significantly impaired transactivation activity. ERK2 knock-down by siRNA, or treatment with U0126 or H20 repressed EBNA1-dependent transactivation. Collectively, these data indicate that blocking ERK2-directed phosphorylation can suppress EBNA1-transactivation function in latent EBV-infected cells, validating ERK2 as a drug target for EBV-associated disorders. PMID:27009860

  20. Crosstalk between the peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) and the vitamin D receptor (VDR) in human breast cancer cells: PPAR{gamma} binds to VDR and inhibits 1{alpha},25-dihydroxyvitamin D{sub 3} mediated transactivation

    SciTech Connect

    Alimirah, Fatouma; Peng, Xinjian; Yuan, Liang; Mehta, Rajeshwari R.; Knethen, Andreas von; Choubey, Divaker; Mehta, Rajendra G.

    2012-11-15

    Heterodimerization and cross-talk between nuclear hormone receptors often occurs. For example, estrogen receptor alpha (ER{alpha}) physically binds to peroxisome proliferator-activated receptor gamma (PPAR{gamma}) and inhibits its transcriptional activity. The interaction between PPAR{gamma} and the vitamin D receptor (VDR) however, is unknown. Here, we elucidate the molecular mechanisms linking PPAR{gamma} and VDR signaling, and for the first time we show that PPAR{gamma} physically associates with VDR in human breast cancer cells. We found that overexpression of PPAR{gamma} decreased 1{alpha},25-dihydroxyvitamin D{sub 3} (1,25D{sub 3}) mediated transcriptional activity of the vitamin D target gene, CYP24A1, by 49% and the activity of VDRE-luc, a vitamin D responsive reporter, by 75% in T47D human breast cancer cells. Deletion mutation experiments illustrated that helices 1 and 4 of PPAR{gamma}'s hinge and ligand binding domains, respectively, governed this suppressive function. Additionally, abrogation of PPAR{gamma}'s AF2 domain attenuated its repressive action on 1,25D{sub 3} transactivation, indicating that this domain is integral in inhibiting VDR signaling. PPAR{gamma} was also found to compete with VDR for their binding partner retinoid X receptor alpha (RXR{alpha}). Overexpression of RXR{alpha} blocked PPAR{gamma}'s suppressive effect on 1,25D{sub 3} action, enhancing VDR signaling. In conclusion, these observations uncover molecular mechanisms connecting the PPAR{gamma} and VDR pathways. -- Highlights: PPAR{gamma}'s role on 1{alpha},25-dihydroxyvitamin D{sub 3} transcriptional activity is examined. Black-Right-Pointing-Pointer PPAR{gamma} physically binds to VDR and inhibits 1{alpha},25-dihydroxyvitamin D{sub 3} action. Black-Right-Pointing-Pointer PPAR{gamma}'s hinge and ligand binding domains are important for this inhibitory effect. Black-Right-Pointing-Pointer PPAR{gamma} competes with VDR for the availability of their binding partner, RXR{alpha}.

  1. Inhibition of Receptor Signaling and of Glioblastoma-derived Tumor Growth by a Novel PDGFRβ Aptamer

    PubMed Central

    Camorani, Simona; Esposito, Carla L; Rienzo, Anna; Catuogno, Silvia; Iaboni, Margherita; Condorelli, Gerolama; de Franciscis, Vittorio; Cerchia, Laura

    2014-01-01

    Platelet-derived growth factor receptor β (PDGFRβ) is a cell-surface tyrosine kinase receptor implicated in several cellular processes including proliferation, migration, and angiogenesis. It represents a compelling therapeutic target in many human tumors, including glioma. A number of tyrosine kinase inhibitors under development as antitumor agents have been found to inhibit PDGFRβ. However, they are not selective as they present multiple tyrosine kinase targets. Here, we report a novel PDGFRβ-specific antagonist represented by a nuclease-resistant RNA-aptamer, named Gint4.T. This aptamer is able to specifically bind to the human PDGFRβ ectodomain (Kd: 9.6 nmol/l) causing a strong inhibition of ligand-dependent receptor activation and of downstream signaling in cell lines and primary cultures of human glioblastoma cells. Moreover, Gint4.T aptamer drastically inhibits cell migration and proliferation, induces differentiation, and blocks tumor growth in vivo. In addition, Gint4.T aptamer prevents PDGFRβ heterodimerization with and resultant transactivation of epidermal growth factor receptor. As a result, the combination of Gint4.T and an epidermal growth factor receptor–targeted aptamer is better at slowing tumor growth than either single aptamer alone. These findings reveal Gint4.T as a PDGFRβ-drug candidate with translational potential. PMID:24566984

  2. Direct interaction of the tau 1 transactivation domain of the human glucocorticoid receptor with the basal transcriptional machinery.

    PubMed Central

    McEwan, I J; Wright, A P; Dahlman-Wright, K; Carlstedt-Duke, J; Gustafsson, J A

    1993-01-01

    We have used a yeast (Saccharomyces cerevisiae) cell free transcription system to study protein-protein interactions involving the tau 1 transactivation domain of the human glucocorticoid receptor that are important for transcriptional transactivation by the receptor. Purified tau 1 specifically inhibited transcription from a basal promoter derived from the CYC1 gene and from the adenovirus 2 major late core promoter in a concentration-dependent manner. This inhibition or squelching was correlated with the transactivation activity of tau 1. Recombinant yeast TATA-binding protein (yTFIID), although active in vitro, did not specifically reverse the inhibitory effect of tau 1. In addition, no specific interaction between tau 1 and yTFIID could be shown in vitro by affinity chromatography. Taken together, these results indicate that the tau 1 transactivation domain of the human glucocorticoid receptor interacts directly with the general transcriptional apparatus through some target protein(s) that is distinct from the TATA-binding factor. Furthermore, this assay can be used to identify interacting factors, since after phosphocellulose chromatography of a whole-cell yeast extract, a fraction that contained an activity which selectively counteracted the squelching effect of tau 1 was found. Images PMID:8417339

  3. Invasive Trophoblasts Stimulate Vascular Smooth Muscle Cell Apoptosis by a Fas Ligand-Dependent Mechanism

    PubMed Central

    Harris, Lynda K.; Keogh, Rosemary J.; Wareing, Mark; Baker, Philip N.; Cartwright, Judith E.; Aplin, John D.; Whitley, Guy St J.

    2006-01-01

    During pregnancy, trophoblasts migrate from the placenta into uterine spiral arteries, transforming them into wide channels that lack vasoconstrictive properties. In pathological pregnancies, this process is incomplete. To define the fundamental events involved in spiral artery remodeling, we have studied the effect of trophoblasts on vascular smooth muscle cells (SMCs). Here we demonstrate for the first time that apoptosis of SMCs can be initiated by invading trophoblasts. When trophoblasts isolated from normal placenta (primary trophoblasts) or conditioned medium was perfused into spiral or umbilical artery segments, apoptosis of SMCs resulted. Culture of human aortic SMCs (HASMCs) with primary trophoblasts, primary trophoblast-conditioned medium, or a trophoblast-derived cell line (SGHPL-4) also significantly increased SMC apoptosis. Fas is expressed by spiral artery SMCs, and a Fas-activating antibody triggered HASMC apoptosis. Furthermore, a Fas ligand (FasL)-blocking antibody significantly inhibited HASMC apoptosis induced by primary trophoblasts, SGHPL-4, or trophoblast-conditioned medium. Depleting primary trophoblast-conditioned medium of FasL also abrogated SMC apoptosis in vessels in situ. These results suggest that apoptosis triggered by the release of soluble FasL from invading trophoblasts contributes to the loss of smooth muscle from the walls of spiral arteries during pregnancy. PMID:17071607

  4. ADAM-mediated amphiregulin shedding and EGFR transactivation

    PubMed Central

    Kasina, S.; Scherle, P. A.; Hall, C. L.; Macoska, J. A.

    2011-01-01

    Introduction The ectodomain shedding of epidermal growth factor receptor (EGFR) ligands, such as amphiregulin (AREG), by ADAMs (A Disintegrin And Metalloproteases) can be stimulated by G protein-coupled receptor (GPCR) agonists. Interactions between the CXCR4 GPCR and the CXCL12 chemokine have been shown to mediate gene transcription and cellular proliferation in non-transformed and transformed prostate epithelial cells, as well as motility/invasiveness in transformed cells. Objectives In this report, we investigated the ability of CXCL12 to stimulate amphiregulin ectodomain shedding in non-transformed and transformed prostate epithelial cells that respond proliferatively to sub-nanomolar levels of CXCL12 and amphiregulin. Materials and Methods Non-transformed N15C6 and transformed PC3 prostate epithelial cells were assessed for amphiregulin shedding, ADAM activation, Src phosphorylation and EGFR activation using ELISA, immunoblot, and immunoprecipitation techniques, and for proliferation using cell counting after stimulation with CXCL12 or vehicle. Results The results of these studies identify CXCL12 as a novel inducer of amphiregulin ectodomain shedding and show that both basal and CXCL12-mediated amphiregulin shedding are ADAM10- and Src kinase-dependent in non-transformed N15C6 cells. In contrast, amphiregulin shedding is not amplified subsequent to stimulation with exogenous CXCL12, and is not reduced subsequent to metalloprotease- or Src kinase-inhibition, in highly aggressive PC3 prostate cancer cells. These data also show that CXCL12-mediated cellular proliferation requires EGFR transactivation in a Src-and ADAM-dependent manner in non-transformed prostate epithelial cells. However, these same mechanisms are dysfunctional in highly transformed prostate cancer cells, which secrete amphiregulin in an autocrine manner that cannot be repressed through metalloprotease- or Src kinase inhibition. Conclusion These findings show that non-transformed and transformed

  5. Gli2 protein expression level is a feasible marker of ligand-dependent hedgehog activation in pancreatic neoplasms.

    PubMed

    Sugiyama, Y; Sasajima, J; Mizukami, Y; Koizumi, K; Kawamoto, T; Ono, Y; Karasaki, H; Tanabe, H; Fujiya, M; Kohgo, Y

    2016-06-01

    The hedgehog pathway is known to promote proliferation of pancreatic ductal adenocarcinoma (PDA) and has been shown to restrain tumor progression. To understand how hedgehog causes these effects, we sought to carefully examine protein expression of hedgehog signaling components during different tumor stages. Genetically engineered mice, Pdx1-Cre;LSL-KrasG12D and Pdx1-Cre;LSL-KrasG12D;p53lox/+, were utilized to model distinct phases of tumorigenesis, pancreatic intraepithelial neoplasm (PanIN) and PDA. Human pancreatic specimens of intraductal papillary mucinous neoplasm (IPMN) and PDA were also employed. PanIN and IPMN lesions highly express Sonic Hedgehog, at a level that is slightly higher than that observed in PDA. GLI2 protein is also expressed in both PanIN/IPMN and PDA. Although there was no difference in the nuclear staining, the cytoplasmic GLI2 level in PDA was modest in comparison to that in PanIN/IPMN. Hedgehog interacting protein was strongly expressed in the precursors, whereas the level in PDA was significantly attenuated. There were no differences in expression of Patched1 at early and late stages. Finally, a strong correlation between Sonic Hedgehog and GLI2 staining was found in both human and murine pancreatic tumors. The results indicate that the GLI2 protein level could serve as a feasible marker of ligand-dependent hedgehog activation in pancreatic neoplasms. PMID:27543868

  6. Suppression of estrogen receptor-alpha transactivation by thyroid transcription factor-2 in breast cancer cells

    SciTech Connect

    Park, Eunsook; Gong, Eun-Yeung; Romanelli, Maria Grazia; Lee, Keesook

    2012-05-11

    Highlights: Black-Right-Pointing-Pointer TTF-2 was expressed in mammary glands and breast cancer cells. Black-Right-Pointing-Pointer TTF-2 repressed ER{alpha} transactivation. Black-Right-Pointing-Pointer TTF-2 inhibited the proliferation of breast cancer cells. -- Abstract: Estrogen receptors (ERs), which mediate estrogen actions, regulate cell growth and differentiation of a variety of normal tissues and hormone-responsive tumors through interaction with cellular factors. In this study, we show that thyroid transcription factor-2 (TTF-2) is expressed in mammary gland and acts as ER{alpha} co-repressor. TTF-2 inhibited ER{alpha} transactivation in a dose-dependent manner in MCF-7 breast cancer cells. In addition, TTF-2 directly bound to and formed a complex with ER{alpha}, colocalizing with ER{alpha} in the nucleus. In MCF-7/TTF-2 stable cell lines, TTF-2 repressed the expression of endogenous ER{alpha} target genes such as pS2 and cyclin D1 by interrupting ER{alpha} binding to target promoters and also significantly decreased cell proliferation. Taken together, these data suggest that TTF-2 may modulate the function of ER{alpha} as a corepressor and play a role in ER-dependent proliferation of mammary cells.

  7. MCRS2 represses the transactivation activities of Nrf1

    PubMed Central

    Wu, Jia-Long; Lin, Young-Sun; Yang, Chi-Chiang; Lin, Yu-Jen; Wu, Shan-Fu; Lin, Ying-Ting; Huang, Chien-Fu

    2009-01-01

    Background Nrf1 [p45 nuclear factor-erythroid 2 (p45 NF-E2)-related factor 1], a member of the CNC-bZIP (CNC basic region leucine zipper) family, is known to be a transcriptional activator by dimerization with distinct partners, such as Maf, FosB, c-Jun, JunD, etc. The transcriptional roles of CNC-bZIP family are demonstrated to be involved in globin gene expression as well as the antioxidant response. For example, CNC-bZIP factors can regulate the expression of detoxification proteins through AREs, such as expression of human gamma-glutamylcysteine synthetases (GCS), glutathione S-transferases (GST), UDP-glucuronosyl transferase (UDP-GT), NADP (H) quinone oxidoreductase (NQOs), etc. To further explore other factor(s) in cells related to the function of Nrf1, we performed a yeast two-hybrid screening assay to identify any Nrf1-interacting proteins. In this study, we isolated a cDNA encoding residues 126–475 of MCRS2 from the HeLa cell cDNA library. Some functions of MCRS1 and its splice variant-MSP58 and MCRS2 have been previously identified, such as transforming, nucleolar sequestration, ribosomal gene regulation, telomerase inhibition activities, etc. Here, we demonstrated MCRS2 can function as a repressor on the Nrf1-mediated transactivation using both in vitro and in vivo systems. Results To find other proteins interacting with the CNC bZIP domain of Nrf1, the CNC-bZIP region of Nrf1 was used as a bait in a yeast two-hybrid screening assay. MCRS2, a splicing variant of p78/MCRS1, was isolated as the Nrf1-interacting partner from the screenings. The interaction between Nrf1 and MCRS2 was confirmed in vitro by GST pull-down assays and in vivo by co-immunoprecipitation. Further, the Nrf1-MCRS2 interaction domains were mapped to the residues 354–447 of Nrf1 as well as the residues 314–475 of MCRS2 respectively, by yeast two-hybrid and GST pull-down assays. By immunofluorescence, MCRS2-FLAG was shown to colocalize with HA-Nrf1 in the nucleus and didn't result

  8. Cholinergic agonists transactivate EGFR and stimulate MAPK to induce goblet cell secretion.

    PubMed

    Kanno, Harumi; Horikawa, Yoshitaka; Hodges, Robin R; Zoukhri, Driss; Shatos, Marie A; Rios, Jose D; Dartt, Darlene A

    2003-04-01

    Conjunctival goblet cells are the primary source of mucins in the mucous layer, the innermost layer of the tear film. Conjunctival goblet cell mucin secretion is under neural control because exogenous addition of parasympathetic agonists stimulates goblet cell secretion. To elucidate the intracellular signal pathways used by cholinergic agonists to stimulate goblet cell mucin secretion, we determined whether p42/p44 mitogen-activated protein kinase (MAPK) is activated during cholinergic agonist-stimulated mucin secretion. Rat conjunctiva was removed, preincubated with or without antagonists, and stimulated with the cholinergic agonist carbachol (10(-4) M). Carbachol statistically significantly stimulated the phosphorylation of MAPK in a time- and concentration-dependent manner. U-0126, an inhibitor of MAPK activation, completely inhibited both the activation of MAPK and goblet cell secretion stimulated by carbachol. The M(1) muscarinic antagonist pirenzepine, the M(2) muscarinic antagonist gallamine, and the M(1)/M(3) muscarinic receptor antagonist N-(3-chloropropyl)-4-piperidinyl diphenylacetate (4-DAMP) also inhibited carbachol-stimulated MAPK activation. Increasing the intracellular Ca(2+) concentration with a Ca(2+) ionophore increased MAPK activation, and chelation of extracellular Ca(2+) inhibited carbachol-stimulated activation. Carbachol also increased tyrosine phosphorylation of Pyk2, p60Src, and the epidermal growth factor receptor (EGFR). The Src inhibitor PP1 and the EGFR inhibitor AG-1478 completely inhibited carbachol-stimulated MAPK activation. AG-1478 also inhibited goblet cell secretion. We conclude that carbachol transactivates the EGFR to activate MAPK, leading to conjunctival goblet cell secretion. In addition, carbachol also activates Pyk2 and p60Src that could play a role in the transactivation of the EGFR.

  9. Ligand-Dependent Disorder of Loop Observed in Extended-Spectrum SHV-Type beta-Lactamase

    SciTech Connect

    J Sampson; W Ke; C Bethel; S Pagadala; M Nottingham; R Bonomo; J Buynak; F van den Akker

    2011-12-31

    Among Gram-negative bacteria, resistance to {beta}-lactams is mediated primarily by {beta}-lactamases (EC 3.2.6.5), periplasmic enzymes that inactivate {beta}-lactam antibiotics. Substitutions at critical amino acid positions in the class A {beta}-lactamase families result in enzymes that can hydrolyze extended-spectrum cephalosporins, thus demonstrating an 'extended-spectrum' {beta}-lactamase (ESBL) phenotype. Using SHV ESBLs with substitutions in the {Omega} loop (R164H and R164S) as target enzymes to understand this enhanced biochemical capability and to serve as a basis for novel {beta}-lactamase inhibitor development, we determined the spectra of activity and crystal structures of these variants. We also studied the inactivation of the R164H and R164S mutants with tazobactam and SA2-13, a unique {beta}-lactamase inhibitor that undergoes a distinctive reaction chemistry in the active site. We noted that the reduced K{sub i} values for the R164H and R164S mutants with SA2-13 are comparable to those with tazobactam (submicromolar). The apo enzyme crystal structures of the R164H and R164S SHV variants revealed an ordered {Omega} loop architecture that became disordered when SA2-13 was bound. Important structural alterations that result from the binding of SA2-13 explain the enhanced susceptibility of these ESBL enzymes to this inhibitor and highlight ligand-dependent {Omega} loop flexibility as a mechanism for accommodating and hydrolyzing {beta}-lactam substrates.

  10. Estrogen receptor alpha is cell cycle-regulated and regulates the cell cycle in a ligand-dependent fashion.

    PubMed

    JavanMoghadam, Sonia; Weihua, Zhang; Hunt, Kelly K; Keyomarsi, Khandan

    2016-06-17

    Estrogen receptor alpha (ERα) has been implicated in several cell cycle regulatory events and is an important predictive marker of disease outcome in breast cancer patients. Here, we aimed to elucidate the mechanism through which ERα influences proliferation in breast cancer cells. Our results show that ERα protein is cell cycle-regulated in human breast cancer cells and that the presence of 17-β-estradiol (E2) in the culture medium shortened the cell cycle significantly (by 4.5 hours, P < 0.05) compared with unliganded conditions. The alterations in cell cycle duration were observed in the S and G2/M phases, whereas the G1 phase was indistinguishable under liganded and unliganded conditions. In addition, ERα knockdown in MCF-7 cells accelerated mitotic exit, whereas transfection of ERα-negative MDA-MB-231 cells with exogenous ERα significantly shortened the S and G2/M phases (by 9.1 hours, P < 0.05) compared with parental cells. Finally, treatment of MCF-7 cells with antiestrogens revealed that tamoxifen yields a slower cell cycle progression through the S and G2/M phases than fulvestrant does, presumably because of the destabilizing effect of fulvestrant on ERα protein. Together, these results show that ERα modulates breast cancer cell proliferation by regulating events during the S and G2/M phases of the cell cycle in a ligand-dependent fashion. These results provide the rationale for an effective treatment strategy that includes a cell cycle inhibitor in combination with a drug that lowers estrogen levels, such as an aromatase inhibitor, and an antiestrogen that does not result in the degradation of ERα, such as tamoxifen.

  11. A Functional Selectivity Mechanism at the Serotonin-2A GPCR Involves Ligand-Dependent Conformations of Intracellular Loop 2

    PubMed Central

    2014-01-01

    With recent progress in determination of G protein-coupled receptor (GPCR) structure with crystallography, a variety of other experimental approaches (e.g., NMR spectroscopy, fluorescent-based assays, mass spectrometry techniques) are also being used to characterize state-specific and ligand-specific conformational states. MD simulations offer a powerful complementary approach to elucidate the dynamic features associated with ligand-specific GPCR conformations. To shed light on the conformational elements and dynamics of the important aspect of GPCR functional selectivity, we carried out unbiased microsecond-length MD simulations of the human serotonin 2A receptor (5-HT2AR) in the absence of ligand and bound to four distinct serotonergic agonists. The 5-HT2AR is a suitable system to study the structural features involved in the ligand-dependent conformational heterogeneity of GPCRs because it is well-characterized experimentally and exhibits a strong agonist-specific phenotype in that some 5-HT2AR agonists induce LSD-like hallucinations, while others lack this psychoactive property entirely. Here we report evidence for structural and dynamic differences in 5-HT2AR interacting with such pharmacologically distinct ligands, hallucinogens, and nonhallucinogens obtained from all-atom MD simulations. Differential ligand binding contacts were identified for structurally similar hallucinogens and nonhallucinogens and found to correspond to different conformations in the intracellular loop 2 (ICL2). From the different ICL2 conformations, functional selective phenotypes are suggested through effects on dimerization and/or distinct direct interaction with effector proteins. The findings are presented in the context of currently proposed hallucinogenesis mechanisms, and ICL2 is proposed as a fine-tuning selective switch that can differentiates modes of 5-HT2AR activation. PMID:25314362

  12. Nuclear AURKA acquires kinase-independent transactivating function to enhance breast cancer stem cell phenotype.

    PubMed

    Zheng, Feimeng; Yue, Caifeng; Li, Guohui; He, Bin; Cheng, Wei; Wang, Xi; Yan, Min; Long, Zijie; Qiu, Wanshou; Yuan, Zhongyu; Xu, Jie; Liu, Bing; Shi, Qian; Lam, Eric W-F; Hung, Mien-Chie; Liu, Quentin

    2016-01-01

    Centrosome-localized mitotic Aurora kinase A (AURKA) facilitates G2/M events. Here we show that AURKA translocates to the nucleus and causes distinct oncogenic properties in malignant cells by enhancing breast cancer stem cell (BCSC) phenotype. Unexpectedly, this function is independent of its kinase activity. Instead, AURKA preferentially interacts with heterogeneous nuclear ribonucleoprotein K (hnRNP K) in the nucleus and acts as a transcription factor in a complex that induces a shift in MYC promoter usage and activates the MYC promoter. Blocking AURKA nuclear localization inhibits this newly discovered transactivating function of AURKA, sensitizing resistant BCSC to kinase inhibition. These findings identify a previously unknown oncogenic property of the spatially deregulated AURKA in tumorigenesis and provide a potential therapeutic opportunity to overcome kinase inhibitor resistance. PMID:26782714

  13. Nuclear AURKA acquires kinase-independent transactivating function to enhance breast cancer stem cell phenotype

    PubMed Central

    Zheng, Feimeng; Yue, Caifeng; Li, Guohui; He, Bin; Cheng, Wei; Wang, Xi; Yan, Min; Long, Zijie; Qiu, Wanshou; Yuan, Zhongyu; Xu, Jie; Liu, Bing; Shi, Qian; Lam, Eric W.-F.; Hung, Mien-Chie; Liu, Quentin

    2016-01-01

    Centrosome-localized mitotic Aurora kinase A (AURKA) facilitates G2/M events. Here we show that AURKA translocates to the nucleus and causes distinct oncogenic properties in malignant cells by enhancing breast cancer stem cell (BCSC) phenotype. Unexpectedly, this function is independent of its kinase activity. Instead, AURKA preferentially interacts with heterogeneous nuclear ribonucleoprotein K (hnRNP K) in the nucleus and acts as a transcription factor in a complex that induces a shift in MYC promoter usage and activates the MYC promoter. Blocking AURKA nuclear localization inhibits this newly discovered transactivating function of AURKA, sensitizing resistant BCSC to kinase inhibition. These findings identify a previously unknown oncogenic property of the spatially deregulated AURKA in tumorigenesis and provide a potential therapeutic opportunity to overcome kinase inhibitor resistance. PMID:26782714

  14. Vitamin D interferes with transactivation of the growth hormone gene by thyroid hormone and retinoic acid.

    PubMed Central

    Garcia-Villalba, P; Jimenez-Lara, A M; Aranda, A

    1996-01-01

    The thyroid hormone, retinoic acid (RA), and vitamin D regulate gene expression by binding to similar receptors which act as ligand-inducible transcription factors. Incubation of pituitary GH4C1 cells with nanomolar concentrations of vitamin D markedly reduces the response of the rat growth hormone mRNA to thyroid hormone triiodothyronine (T3) and RA. The stimulation of growth hormone gene expression by both ligands is mediated by a common hormone response element (TREGH) present in the 5'-flanking region of the gene, and the inhibition caused by vitamin D is due to transcriptional interference of the vitamin D receptor on this DNA element. No inhibition of the basal promoter activity by the vitamin was observed. The response to T3 and RA of a heterologous promoter containing this element, the palindromic T3- and RA-responsive sequence TREPAL, or a direct repeat of the same motif is also inhibited by vitamin D. In contrast, vitamin D strongly induces the activity of constructs containing a vitamin D response element, and neither T3 nor RA reduces vitamin D-mediated transactivation. Transfection with an expression vector for the retinoid X receptor alpha (RXR alpha) increases transactivation by T3 and RA but does not abolish the inhibition caused by the vitamin. Gel retardation experiments show that the vitamin D receptor (VDR) as a heterodimer with RXR weakly binds to the T3- and RA-responsive elements. Additionally, VDR displaces binding of T3 and RA receptors in a dose-dependent manner. Our data suggest the formation of TR-VDR and RAR-VDR heterodimers with RXR. The fact that the same response element mediates opposite effects of at least four different nuclear receptors provides a greater complexity and flexibility of the transcriptional responses to their ligands. PMID:8524311

  15. ERK phosphorylation in intact, adult brain by alpha(2)-adrenergic transactivation of EGF receptors.

    PubMed

    Du, Ting; Li, Baoman; Liu, Shufang; Zang, Peizhuo; Prevot, Vincent; Hertz, Leif; Peng, Liang

    2009-12-01

    Our previous work demonstrated dexmedetomidine-activated phosphorylation of extracellular regulated kinases 1 and 2 (ERK(1/2)) in primary cultures of mouse astrocytes and showed that it is evoked by alpha(2)-adrenoceptor-mediated transactivation of epidermal growth factor (EGF) receptors, a known response to activation of G(i/o)- or G(q)-coupled receptors [Li, B., Du, T., Li, H., Gu, L., Zhang, H., Huang, J., Hertz, L., Peng, L., 2008a. Signaling pathways for transactivation by dexmedetomidine of epidermal growth factor receptors in astrocytes and its paracrine effect on neurons. Br. J. Pharmacol. 154, 191-203]. Like most studies of transactivation, that study used cultured cells, raising the question whether a similar effect can be demonstrated in intact brain tissue and the brain in vivo. In the present study we have shown that (i) dexmedetomidine-mediated ERK(1/2) phosphorylation occurs in mouse brain slices with a similar concentration dependence as in cultured astrocytes (near-maximum effect at 50nM); (ii) intraperitoneal injection of dexmedetomidine (3microg/kg) in adult mice causes rapid phosphorylation of the EGF receptor (at Y845 and Y992) and of ERK(1/2) in the brain; (iii) both EGF receptor and ERK(1/2) phosphorylation are inhibited by intraventricular administration of (a) AG 1478, a specific inhibitor of the receptor-tyrosine kinase of the EGF receptor; (b) GM 6001, an inhibitor of metalloproteinase(s) required for release of EGF receptor agonists from membrane-bound precursors; or (c) heparin, neutralizing heparin-binding EGF (HB-EGF). Thus, in intact brain HB-EGF, known to be expressed in brain, may be the major EGF agonist released in response to stimulation of alpha(2)-adrenoceptors, the released agonist(s) activate(s) EGF receptors, and ERK(1/2) is phosphorylated as a conventional response to EGF receptor activation. Our previous paper (see above) showed that dexmedetomidine evokes no ERK(1/2) phosphorylation in cultured neurons, but neurons

  16. Identification of the simian foamy virus transcriptional transactivator gene (taf).

    PubMed Central

    Mergia, A; Shaw, K E; Pratt-Lowe, E; Barry, P A; Luciw, P A

    1991-01-01

    Simian foamy virus type 1 (SFV-1), a member of spumavirus subfamily of retroviruses, encodes a transcriptional transactivator that functions to strongly augment gene expression directed by the viral long terminal repeat (LTR). The objective of this study was to identify the viral gene responsible for transactivation. Nucleotide sequences between the env gene and the LTR of SFV-1 were determined. The predicted amino acid sequence revealed two large open reading frames (ORFs), designated ORF-1 (311 amino acids) and ORF-2 (422 amino acids). In the corresponding region of the human foamy virus, three ORFs (bel-1, bel-2, and bel-3) have been identified (R. M. Flugel, A. Rethwilm, B. Maurer, and G. Darai, EMBO J. 6:2077-2084, 1987). Pairwise comparisons of the ORF-1 and ORF-2 with bel-1 and bel-2 show small clusters of homology; less than 39% overall homology of conserved amino acids is observed. A counterpart for human foamy virus bel-3 is not present in the SFV-1 sequence. Three species of viral RNA have been identified in cells infected with SFV-1; an 11.5-kb RNA representing full-length transcripts, a 6.5-kb RNA representing the env message, and a 2.8-kb RNA from the ORF region. Analysis of a cDNA clone encoding the ORF region of SFV-1 reveals that the 2.8-kb message is generated by complex splicing events involving the 3' end of the env gene. In transient expression assays in cell lines representing several species. ORF-1 was shown to be necessary and sufficient for transactivating viral gene expression directed by the SFV-1 LTR. The target for transactivation is located in the U3 domain of the LTR, upstream from position - 125 (+ 1 represents the transcription initiation site). We propose that OFF-1 of SFV-1 be designated the transcriptional transactivator of foamy virus (taf). Images PMID:1851862

  17. trans-dominant mutants of E1A provide genetic evidence that the zinc finger of the trans-activating domain binds a transcription factor.

    PubMed Central

    Webster, L C; Ricciardi, R P

    1991-01-01

    The 289R E1A protein of adenovirus stimulates transcription of early viral and certain cellular genes. trans-Activation requires residues 140 to 188, which encompass a zinc finger. Several studies have indicated that trans-activation by E1A is mediated through cellular transcription factors. In particular, the ability of the trans-dominant E1A point mutant hr5 (Ser-185 to Asn) to inhibit wild-type E1A trans-activation was proposed to result from the sequestration of a cellular factor. Using site-directed mutagenesis, we individually replaced every residue within and flanking the trans-activating domain with a conservative amino acid, revealing 16 critical residues. Six of the individual substitutions lying in a contiguous stretch C terminal to the zinc finger (carboxyl region183-188) imparted a trans-dominant phenotype. trans-Dominance was even produced by deletion of the entire carboxyl region183-188. Conversely, an intact finger region147-177 was absolutely required for trans-dominance, since second-site substitution of every critical residue in this region abrogated the trans-dominant phenotype of the hr5 protein. These data indicate that the finger region147-177 bind a limiting cellular transcription factor and that the carboxyl region183-188 provides a separate and essential function. In addition, we show that four negatively charged residues within the trans-activating domain do not comprise a distinct acidic activating region. We present a model in which the trans-activating domain of E1A binds to two different cellular protein targets through the finger and carboxyl regions. Images PMID:1831535

  18. Molecular dissection of the cauliflower mosaic virus translation transactivator.

    PubMed Central

    De Tapia, M; Himmelbach, A; Hohn, T

    1993-01-01

    The cauliflower mosaic virus (CaMV) transactivator (TAV) is a complex protein that appears to be involved in many aspects of the virus life cycle. One of its roles is to control translation from the polycistronic CaMV 35S RNA. Here we report a molecular dissection of TAV in relation to its ability to enhance dicistronic translation in transient expression experiments. We have identified a protein domain that is responsible and sufficient for that activity. This 'MiniTAV domain' consists of only 140 of the 520 amino acids in the full-length sequence. A further domain located outside the MiniTAV, and therefore dispensable for transactivation, is probably involved in interactions with other molecules. This was identified by its ability to compete with wild-type TAV and some of its deletion mutants. We found, furthermore, that the TAV protein binds RNA. Two regions needed for RNA-binding properties were defined outside the MiniTAV domain and RNA binding seems not to be directly involved in the transactivation mechanism. Images PMID:8344266

  19. Tristetraprolin Represses Estrogen Receptor α Transactivation in Breast Cancer Cells*

    PubMed Central

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-01-01

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer. PMID:24737323

  20. Tristetraprolin represses estrogen receptor α transactivation in breast cancer cells.

    PubMed

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-05-30

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer.

  1. Tristetraprolin represses estrogen receptor α transactivation in breast cancer cells.

    PubMed

    Barrios-García, Tonatiuh; Tecalco-Cruz, Angeles; Gómez-Romero, Vania; Reyes-Carmona, Sandra; Meneses-Morales, Iván; León-Del-Río, Alfonso

    2014-05-30

    Estrogen receptor α (ERα) mediates the effects of 17β-estradiol (E2) in normal mammary gland, and it is a key participant in breast cancer tumor development. ERα transactivation activity is mediated by the synergistic interaction of two domains designated AF1 and AF2. The function of AF2 is to recruit coactivator and corepressor proteins that allow ERα to oscillate between the roles of transcriptional activator and repressor. In contrast, the mechanism responsible for AF-1 transcriptional activity is not completely understood. In this study, we identified tristetraproline (TTP) as a novel ERα-associated protein. TTP expression in MCF7 cells repressed ERα transactivation and reduced MCF7 cell proliferation and the ability of the cells to form tumors in a mouse model. We show that TTP transcriptional activity is mediated through its recruitment to the promoter region of ERα target genes and its interaction with histone deacetylases, in particular with HDAC1. TTP expression attenuates the coactivating activity of SRC-1, suggesting that exchange between TTP and other coactivators may play an important role in fine-tuning ERα transactivation. These results indicate that TTP acts as a bona fide ERα corepressor and suggest that this protein may be a contributing factor in the development of E2-dependent tumors in breast cancer. PMID:24737323

  2. Intracellular transactivation of epidermal growth factor receptor by α1A-adrenoceptor is mediated by phosphatidylinositol 3-kinase independently of activation of extracellular signal regulated kinases 1/2 and serine-threonine kinases in Chinese hamster ovary cells.

    PubMed

    Ulu, Nadir; Henning, Robert H; Guner, Sahika; Zoto, Teuta; Duman-Dalkilic, Basak; Duin, Marry; Gurdal, Hakan

    2013-10-01

    Transactivation of epidermal growth factor receptor (EGFR) by α1-adrenoceptor (α1-AR) is implicated in contraction and hypertrophy of vascular smooth muscle (VSM). We examine whether all α1-AR subtypes transactivate EGFR and explore the mechanism of transactivation. Chinese hamster ovary (CHO) cells stably expressing one subtype of α1-AR were transiently transfected with EGFR. The transactivation mechanism was examined both by coexpression of a chimeric erythropoietin (EPO)-EGFR with an extracellular EPO and intracellular EGFR domain, and by pharmacologic inhibition of external and internal signaling routes. All three α1-AR subtypes transactivated EGFR, which was dependent on the increase in intracellular calcium. The EGFR kinase inhibitor AG1478 [4-(3'-chloroanilino)-6,7-dimethoxyquinazoline] abrogated α1A-AR and α1D-AR induced phosphorylation of EGFR, but both the inhibition of matrix metalloproteinases by GM6001 [(R)-N4-hydroxy-N(1)-[(S)-2-(1H-indol-3-yl)-1-methylcarbamoyl-ethyl]-2-isobutyl-succinamide] or blockade of EGFR by cetuximab did not. Stimulation of α1A-AR and α1D-AR also induced phosphorylation of EPO-EGFR chimeric receptors. Moreover, α1A-AR stimulation enhanced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 and serine-threonine kinases (Akt), which were both unaffected by AG1478, indicating that ERK1/2 and Akt phosphorylation is independent of EGFR transactivation. Accordingly, inhibitors of ERK1/2 or Akt did not influence the α1A-AR-mediated EGFR transactivation. Inhibition of calcium/calmodulin-dependent kinase II (CaMKII), phosphatidylinositol 3-kinase (PI3K), and Src, however, did block EGFR transactivation by α1A-AR and α1D-AR. These findings demonstrate that all α1-AR subtypes transactivate EGFR, which is dependent on an intracellular signaling route involving an increase in calcium and activation of CaMKII, PI3K, and Src, but not the of ERK1/2 and Akt pathways.

  3. Ligand-dependent coactivation of the human bile acid receptor FXR by the peroxisome proliferator-activated receptor gamma coactivator-1alpha.

    PubMed

    Savkur, Rajesh S; Thomas, Jeffrey S; Bramlett, Kelli S; Gao, Yunling; Michael, Laura F; Burris, Thomas P

    2005-01-01

    Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) has been shown to play an important role in energy metabolism by coordinating transcriptional programs involved in mitochondrial biogenesis, adaptive thermogenesis, gluconeogenesis, and fatty acid oxidation. PGC-1alpha also plays a crucial role in cholesterol metabolism by serving as a coactivator of the liver X receptor-alpha and inducing the expression of cholesterol 7-alpha-hydroxylase. Here, we demonstrate that PGC-1alpha also functions as an effective coactivator of farnesoid X receptor (FXR), the bile acid receptor. Transient cotransfection assays demonstrate that PGC-1alpha enhances ligand-mediated FXR transcription when either full-length FXR or Gal4 DNA binding domain-FXR-ligand binding domain chimeras were analyzed. Mammalian two-hybrid analyses, glutathione S-transferase affinity chromatography and biochemical coactivator recruitment assays demonstrate ligand-dependent interaction between the two proteins both in vivo and in vitro. PGC-1alpha-mediated coactivation of FXR was highly ligand-dependent and absolutely required an intact activation function-2 (AF-2) domain of FXR and the LXXLL motif in PGC-1alpha. The integrity of the charge clamp was required, further illustrating the role of the ligand binding domain of FXR in PGC-1alpha recognition. Together, these results indicate that PGC-1alpha functions as a potent coactivator for FXR and further implicates its role in the regulation of genes that are involved in bile acid and lipid metabolism.

  4. Ligand-dependent active-site closure revealed in the crystal structure of Mycobacterium tuberculosis MenB complexed with product analogues.

    PubMed

    Song, Haigang; Sung, Hoi Pang; Tse, Yuk Sing; Jiang, Ming; Guo, Zhihong

    2014-11-01

    1,4-Dihydroxy-2-naphthoyl coenzyme A (DHNA-CoA) synthase catalyzes an essential intramolecular Claisen condensation in menaquinone biosynthesis and is an important target for the development of new antibiotics. This enzyme in Mycobacterium tuberculosis is cofactor-free and is classified as a type II DHNA-CoA synthase, differing from type I enzymes, which rely on exogenous bicarbonate for catalysis. Its crystal structures in complex with product analogues have been determined at high resolution to reveal ligand-dependent structural changes, which include the ordering of a 27-residue active-site loop (amino acids 107-133) and the reorientation of the carboxy-terminal helix (amino acids 289-301) that forms part of the active site from the opposing subunit across the trimer-trimer interface. These structural changes result in closure of the active site to the bulk solution, which is likely to take place through an induced-fit mechanism, similar to that observed for type I DHNA-CoA synthases. These findings demonstrate that the ligand-dependent conformational changes are a conserved feature of all DHNA-CoA synthases, providing new insights into the catalytic mechanism of this essential tubercular enzyme.

  5. Role of EGFR transactivation in angiotensin II signaling to extracellular regulated kinase in preglomerular smooth muscle cells.

    PubMed

    Andresen, Bradley T; Linnoila, Jenny J; Jackson, Edwin K; Romero, Guillermo G

    2003-03-01

    Angiotensin (Ang) II promotes the phosphorylation of extracellular regulated kinase (ERK); however, the mechanisms leading to Ang II-induced ERK phosphorylation are debated. The currently accepted theory involves transactivation of epidermal growth factor receptor (EGFR). We have shown that generation of phosphatidic acid (PA) is required for the recruitment of Raf to membranes and the activation of ERK by multiple agonists, including Ang II. In the present report, we confirm that phospholipase D-dependent generation of PA is required for Ang II-mediated phosphorylation of ERK in Wistar-Kyoto and spontaneously hypertensive rat preglomerular smooth muscle cells (PGSMCs). However, EGF stimulation does not activate phospholipase D or generate PA. These observations indicate that EGF recruits Raf to membranes via a mechanism that does not involve PA, and thus, Ang II-mediated phosphorylation of ERK is partially independent of EGFR-mediated signaling cascades. We hypothesized that phosphoinositide-3-kinase (PI3K) can also act to recruit Raf to membranes; therefore, inhibition of PI3K should inhibit EGF signaling to ERK. Wortmannin, a PI3K inhibitor, inhibited EGF-mediated phosphorylation of ERK (IC50, approximately 14 nmol/L). To examine the role of the EGFR in Ang II-mediated phosphorylation of ERK we utilized 100 nmol/L wortmannin to inhibit EGFR signaling to ERK and T19N RhoA to block Ang II-mediated ERK phosphorylation. Wortmannin treatment inhibited EGF-mediated but not Ang II-mediated phosphorylation of ERK. Furthermore, T19N RhoA inhibited Ang II-mediated ERK phosphorylation, whereas T19N RhoA had significantly less effect on EGF-mediated ERK phosphorylation. We conclude that transactivation of the EGFR is not primarily responsible for Ang II-mediated activation of ERK in PGSMCs.

  6. Transactivation of Vascular Endothelial Growth Factor Receptor-2 by Interleukin-8 (IL-8/CXCL8) Is Required for IL-8/CXCL8-induced Endothelial Permeability

    PubMed Central

    Petreaca, Melissa L.; Yao, Min; Liu, Yan; DeFea, Kathryn

    2007-01-01

    Interleukin-8 (IL-8/CXCL8) is a chemokine that increases endothelial permeability during early stages of angiogenesis. However, the mechanisms involved in IL-8/CXCL8-induced permeability are poorly understood. Here, we show that permeability induced by this chemokine requires the activation of vascular endothelial growth factor receptor-2 (VEGFR2/fetal liver kinase 1/KDR). IL-8/CXCL8 stimulates VEGFR2 phosphorylation in a VEGF-independent manner, suggesting VEGFR2 transactivation. We investigated the possible contribution of physical interactions between VEGFR2 and the IL-8/CXCL8 receptors leading to VEGFR2 transactivation. Both IL-8 receptors interact with VEGFR2 after IL-8/CXCL8 treatment, and the time course of complex formation is comparable with that of VEGFR2 phosphorylation. Src kinases are involved upstream of receptor complex formation and VEGFR2 transactivation during IL-8/CXCL8-induced permeability. An inhibitor of Src kinases blocked IL-8/CXCL8-induced VEGFR2 phosphorylation, receptor complex formation, and endothelial permeability. Furthermore, inhibition of the VEGFR abolishes RhoA activation by IL-8/CXCL8, and gap formation, suggesting a mechanism whereby VEGFR2 transactivation mediates IL-8/CXCL8-induced permeability. This study points to VEGFR2 transactivation as an important signaling pathway used by chemokines such as IL-8/CXCL8, and it may lead to the development of new therapies that can be used in conditions involving increases in endothelial permeability or angiogenesis, particularly in pathological situations associated with both IL-8/CXCL8 and VEGF. PMID:17928406

  7. In situ autoradiography and ligand-dependent tyrosine kinase activity reveal insulin receptors and insulin-like growth factor I receptors in prepancreatic chicken embryos.

    PubMed Central

    Girbau, M; Bassas, L; Alemany, J; de Pablo, F

    1989-01-01

    We previously reported specific cross-linking of 125I-labeled insulin and 125I-labeled insulin-like growth factor I (IGF-I) to the alpha subunit of their respective receptors in chicken embryos of 20 somites and older. To achieve adequate sensitivity and localize spatially the receptors in younger embryos, we adapted an autoradiographic technique using whole-mounted chicken blastoderms. Insulin receptors and IGF-I receptors were expressed and could be localized as early as gastrulation, before the first somite is formed. Relative density was analyzed by a computer-assisted image system, revealing overall slightly higher binding of IGF-I than of insulin. Structures rich in both types of receptors were predominantly of ectodermal origin: Hensen's node in gastrulating embryos and neural folds, neural tube and optic vesicles during neurulation. The signal transduction capability of the receptors in early organogenesis was assessed by their ability to phosphorylate the exogenous substrate poly(Glu80Tyr20). Ligand-dependent tyrosine phosphorylation was demonstrable with both insulin and IGF-I in glycoprotein-enriched preparations from embryos at days 2 through 6 of embryogenesis. There was a developmentally regulated change in ligand-dependent tyrosine kinase activity, with a sharp increase from day 2 to day 4, in contrast with a small increase in the ligand binding. Binding of 125I-labeled IGF-I was, with the solubilized receptors, severalfold higher than binding of 125I-labeled insulin. However, the insulin-dependent phosphorylation was as high as the IGF-I-dependent phosphorylation at each developmental stage. Images PMID:2548191

  8. Quantitative Analysis of NF-κB Transactivation Specificity Using a Yeast-Based Functional Assay

    PubMed Central

    Sharma, Vasundhara; Jordan, Jennifer J.; Ciribilli, Yari; Resnick, Michael A.; Bisio, Alessandra; Inga, Alberto

    2015-01-01

    The NF-κB transcription factor family plays a central role in innate immunity and inflammation processes and is frequently dysregulated in cancer. We developed an NF-κB functional assay in yeast to investigate the following issues: transactivation specificity of NF-κB proteins acting as homodimers or heterodimers; correlation between transactivation capacity and in vitro DNA binding measurements; impact of co-expressed interacting proteins or of small molecule inhibitors on NF-κB-dependent transactivation. Full-length p65 and p50 cDNAs were cloned into centromeric expression vectors under inducible GAL1 promoter in order to vary their expression levels. Since p50 lacks a transactivation domain (TAD), a chimeric construct containing the TAD derived from p65 was also generated (p50TAD) to address its binding and transactivation potential. The p50TAD and p65 had distinct transactivation specificities towards seventeen different κB response elements (κB-REs) where single nucleotide changes could greatly impact transactivation. For four κB-REs, results in yeast were predictive of transactivation potential measured in the human MCF7 cell lines treated with the NF-κB activator TNFα. Transactivation results in yeast correlated only partially with in vitro measured DNA binding affinities, suggesting that features other than strength of interaction with naked DNA affect transactivation, although factors such as chromatin context are kept constant in our isogenic yeast assay. The small molecules BAY11-7082 and ethyl-pyruvate as well as expressed IkBα protein acted as NF-κB inhibitors in yeast, more strongly towards p65. Thus, the yeast-based system can recapitulate NF-κB features found in human cells, thereby providing opportunities to address various NF-κB functions, interactions and chemical modulators. PMID:26147604

  9. Hydrogen sulfide represses androgen receptor transactivation by targeting at the second zinc finger module.

    PubMed

    Zhao, Kexin; Li, Shuangshuang; Wu, Lingyun; Lai, Christopher; Yang, Guangdong

    2014-07-25

    Androgen receptor (AR) signaling is indispensable for the development of prostate cancer from the initial androgen-dependent state to a later aggressive androgen-resistant state. This study examined the role of hydrogen sulfide (H(2)S), a novel gasotransmitter, in the regulation of AR signaling as well as its mediation in androgen-independent cell growth in prostate cancer cells. Here we found that H(2)S inhibits cell proliferation of both androgen-dependent (LNCaP) and antiandrogen-resistant prostate cancer cells (LNCaP-B), with more significance on the latter, which was established by long term treatment of parental LNCaP cells with bicalutamide. The expression of cystathionine γ-lyase (CSE), a major H(2)S producing enzyme in prostate tissue, was reduced in both human prostate cancer tissues and LNCaP-B cells. LNCaP-B cells were resistant to bicalutamide-induced cell growth inhibition, and CSE overexpression could rebuild the sensitivity of LNCaP-B cells to bicalutamide. H(2)S significantly repressed the expression of prostate-specific antigen (PSA) and TMPRSS2, two AR-targeted genes. In addition, H(2)S inhibited AR binding with PSA promoter and androgen-responsive element (ARE) luciferase activity. We further found that AR is post-translationally modified by H(2)S through S-sulfhydration. Mutation of cysteine 611 and cysteine 614 in the second zinc finger module of AR-DNA binding domain diminished the effects of H(2)S on AR S-sulfhydration and AR dimerization. These data suggest that reduced CSE/H2S signaling contributes to antiandrogen-resistant status, and sufficient level of H(2)S is able to inhibit AR transactivation and treat castration-resistant prostate cancer.

  10. Molecular characterization of chicken class II transactivator gene.

    PubMed

    Nikbakht Brujeni, Gholamreza; Khosravi, Mohammad

    2015-01-01

    Class II transactivator (CIITA) is an effective transcriptional factor regulating various genes in the immune system. Since the detection of CIITA in 1993, there has been considerable progress toward understanding its role as an activator of MHC II genes in human and mouse; however, there is little knowledge of this gene in other animals such as chicken. Molecular characterization of the chicken CIITA gene transcript was performed to determine its sequence and expression in different tissues. The CIITA cDNA was first generated through reverse transcriptase-polymerase chain reaction (RT-PCR) from Cobb chicken spleen cell RNA, using oligonucleotide primers based on the predicted cDNA sequence. The effect of the immune system stimulation on the CIITA gene expression in kidney, liver, thymus, and spleen were assessed by semi-quantitative RT-PCR analysis. A partial cDNA sequence (1,688 bp) encoding part of the NACHT domain followed by seven of the transactivator and one of the NLS domains were obtained. Comparison of the deduced amino acid sequence with other CIITAs reveals high level of similarities in amino acid composition, secondary structure and phosphorylation sites. Furthermore, in comparison to the Red Jungle Fowl (RJF) sequence, we found 17 single nucleotide polymorphisms in Cobb broiler chicken, ten of which were reported for the first time. Gene expression analysis indicated that CIITA RNA amounts increased in all the examined tissues following stimulation with Brucella antigen. This investigation may indicate that CIITA molecule has an important role in the chicken immune responses as well as human and other animals.

  11. Human kininogen gene is transactivated by the farnesoid X receptor.

    PubMed

    Zhao, Annie; Lew, Jane-L; Huang, Li; Yu, Jinghua; Zhang, Theresa; Hrywna, Yaroslav; Thompson, John R; de Pedro, Nuria; Blevins, Richard A; Peláez, Fernando; Wright, Samuel D; Cui, Jisong

    2003-08-01

    Human kininogen belongs to the plasma kallikreinkinin system. High molecular weight kininogen is the precursor for two-chain kinin-free kininogen and bradykinin. It has been shown that the two-chain kinin-free kininogen has the properties of anti-adhesion, anti-platelet aggregation, and anti-thrombosis, whereas bradykinin is a potent vasodilator and mediator of inflammation. In this study we show that the human kininogen gene is strongly up-regulated by agonists of the farnesoid X receptor (FXR), a nuclear receptor for bile acids. In primary human hepatocytes, both the endogenous FXR agonist chenodeoxycholate and synthetic FXR agonist GW4064 increased kininogen mRNA with a maximum induction of 8-10-fold. A more robust induction of kininogen expression was observed in HepG2 cells, where kininogen mRNA was increased by chenodeoxycholate or GW4064 up to 130-140-fold as shown by real time PCR. Northern blot analysis confirmed the up-regulation of kininogen expression by FXR agonists. To determine whether kininogen is a direct target of FXR, we examined the sequence of the kininogen promoter and identified a highly conserved FXR response element (inverted repeat, IR-1) in the proximity of the kininogen promoter (-66/-54). FXR/RXRalpha heterodimers specifically bind to this IR-1. A construct of a minimal promoter with the luciferase reporter containing this IR-1 was transactivated by FXR. Deletion or mutation of this IR-1 abolished FXR-mediated promoter activation, indicating that this IR-1 element is responsible for the promoter transactivation by FXR. We conclude that kininogen is a novel and direct target of FXR, and bile acids may play a role in the vasodilation and anti-coagulation processes.

  12. The N-terminal part of TIF1, a putative mediator of the ligand-dependent activation function (AF-2) of nuclear receptors, is fused to B-raf in the oncogenic protein T18.

    PubMed Central

    Le Douarin, B; Zechel, C; Garnier, J M; Lutz, Y; Tora, L; Pierrat, P; Heery, D; Gronemeyer, H; Chambon, P; Losson, R

    1995-01-01

    Nuclear receptors (NRs) bound to response elements mediate the effects of cognate ligands on gene expression. Their ligand-dependent activation function, AF-2, presumably acts on the basal transcription machinery through intermediary proteins/mediators. We have isolated a mouse nuclear protein, TIF1, which enhances RXR and RAR AF-2 in yeast and interacts in a ligand-dependent manner with several NRs in yeast and mammalian cells, as well as in vitro. Remarkably, these interactions require the amino acids constituting the AF-2 activating domain conserved in all active NRs. Moreover, the oestrogen receptor (ER) AF-2 antagonist hydroxytamoxifen cannot promote ER-TIF1 interaction. We propose that TIF1, which contains several conserved domains found in transcriptional regulatory proteins, is a mediator of ligand-dependent AF-2. Interestingly, the TIF1 N-terminal moiety is fused to B-raf in the mouse oncoprotein T18. Images PMID:7744009

  13. Nrf1 and Nrf2 Transcription Factors Regulate Androgen Receptor Transactivation in Prostate Cancer Cells

    PubMed Central

    Schultz, Michelle A.; Hagan, Sharika S.; Datta, Amrita; Zhang, Yiguo; Freeman, Michael L.; Sikka, Suresh C.; Abdel-Mageed, Asim B.; Mondal, Debasis

    2014-01-01

    Despite androgen deprivation therapy (ADT), persistent androgen receptor (AR) signaling enables outgrowth of castration resistant prostate cancer (CRPC). In prostate cancer (PCa) cells, ADT may enhance AR activity through induction of oxidative stress. Herein, we investigated the roles of Nrf1 and Nrf2, transcription factors that regulate antioxidant gene expression, on hormone-mediated AR transactivation using a syngeneic in vitro model of androgen dependent (LNCaP) and castration resistant (C4-2B) PCa cells. Dihydrotestosterone (DHT) stimulated transactivation of the androgen response element (ARE) was significantly greater in C4-2B cells than in LNCaP cells. DHT-induced AR transactivation was coupled with higher nuclear translocation of p65-Nrf1 in C4-2B cells, as compared to LNCaP cells. Conversely, DHT stimulation suppressed total Nrf2 levels in C4-2B cells but elevated total Nrf2 levels in LNCaP cells. Interestingly, siRNA mediated silencing of Nrf1 attenuated AR transactivation while p65-Nrf1 overexpression enhanced AR transactivation. Subsequent studies showed that Nrf1 physically interacts with AR and enhances AR’s DNA-binding activity, suggesting that the p65-Nrf1 isoform is a potential AR coactivator. In contrast, Nrf2 suppressed AR-mediated transactivation by stimulating the nuclear accumulation of the p120-Nrf1 which suppressed AR transactivation. Quantitative RT-PCR studies further validated the inductive effects of p65-Nrf1 isoform on the androgen regulated genes, PSA and TMPRSS2. Therefore, our findings implicate differential roles of Nrf1 and Nrf2 in regulating AR transactivation in PCa cells. Our findings also indicate that the DHT-stimulated increase in p65-Nrf1 and the simultaneous suppression of both Nrf2 and p120-Nrf1 ultimately facilitates AR transactivation in CRPC cells. PMID:24466341

  14. Platelet-activating factor induces ovine fetal pulmonary venous smooth muscle cell proliferation: role of epidermal growth factor receptor transactivation.

    PubMed

    Zhou, Weilin; Ibe, Basil O; Raj, J Usha

    2007-06-01

    We have previously reported that platelet-activating factor (PAF) is present in very high levels in the ovine fetal lung and circulation and that PAF serves as an important physiological vasoconstrictor of the pulmonary circulation in utero. However, it is not known whether PAF stimulates pulmonary vascular smooth muscle cell (SMC) proliferation. In this study, we used ovine fetal pulmonary venous SMCs as our model system to study the effects and mechanisms of action of PAF on SMC proliferation. We found that PAF induced SMC proliferation in a dose-dependent manner. PAF also stimulated activation of both ERK and p38 but not c-Jun NH(2) terminal kinase (JNK) mitogen-activated protein (MAP) kinase pathways. PAF (10 nM) induced phosphorylation of epidermal growth factor receptor (EGFR). Specific inhibition of EGFR by AG-1478 and by the expression of a dominant-negative EGFR mutant in SMCs attenuated PAF-stimulated cell proliferation. Inhibition of heparin-binding EGF-like growth factor (HB-EGF) release by CRM-197 and inhibition of matrix metalloproteinases (MMP) by GM-6001 abolished PAF-induced MAP kinase activation and cell proliferation. Increased alkaline phosphatase (AP) activity after PAF treatment in AP-HB-EGF fusion construct-transfected SMCs indicated that PAF induced the release of HB-EGF within 1 min. Gelatin zymography data showed that PAF stimulated MMP-2 activity and MMP-9 activity within 1 min. These results suggest that PAF promotes pulmonary vascular SMC proliferation via transactivation of EGFR through MMP activation and HB-EGF, resulting in p38 and ERK activation and that EGFR transactivation is essential for the mitogenic effect of PAF in pulmonary venous SMC. PMID:17322418

  15. Global and local perturbation of the tomato microRNA pathway by a trans-activated DICER-LIKE 1 mutant

    PubMed Central

    Arazi, Tzahi

    2014-01-01

    DICER-like 1 (DCL1) is a major player in microRNA (miRNA) biogenesis and accordingly, its few known loss-of-function mutants are either lethal or display arrested development. Consequently, generation of dcl1 mutants by reverse genetics and functional analysis of DCL1 in late-developing organs are challenging. Here, these challenges were resolved through the unique use of trans-activated RNA interference. Global, as well as organ-specific tomato DCL1 (SlDCL1) silencing was induced by crossing the generated responder line (OP:SlDCL1IR) with the appropriate driver line. Constitutive trans-activation knocked down SlDCL1 levels by ~95%, resulting in severe abnormalities including post-germination growth arrest accompanied by decreased miRNA and 21-nucleotide small RNA levels, but prominently elevated levels of 22-nucleotide small RNAs. The increase in the 22-nucleotide small RNAs was correlated with specific up-regulation of SlDCL2b and SlDCL2d, which are probably involved in their biogenesis. Leaf- and flower-specific OP:SlDCL1IR trans-activation inhibited blade outgrowth, induced premature bud senescence and produced pale petals, respectively, emphasizing the importance of SlDCL1-dependent small RNAs in these processes. Together, these results establish OP:SlDCL1IR as an efficient tool for analysing processes regulated by SlDCL1-mediated gene regulation in tomato. PMID:24376253

  16. Neuropeptide Y receptor mediates activation of ERK1/2 via transactivation of the IGF receptor.

    PubMed

    Lecat, Sandra; Belemnaba, Lazare; Galzi, Jean-Luc; Bucher, Bernard

    2015-07-01

    Neuropeptide Y binds to G-protein coupled receptors whose action results in inhibition of adenylyl cyclase activity. Using HEK293 cells stably expressing the native neuropeptide Y Y1 receptors, we found that the NPY agonist elicits a transient phosphorylation of the extracellular signal-regulated kinases (ERK1/2). We first show that ERK1/2 activation following Y1 receptor stimulation is dependent on heterotrimeric Gi/o since it is completely inhibited by pre-treatment with pertussis toxin. In addition, ERK1/2 activation is internalization-independent since mutant Y1 receptors unable to recruit β-arrestins, can still activate ERK signaling to the same extent as wild-type receptors. We next show that this activation of the MAPK pathway is inhibited by the MEK inhibitor U0126, is not dependent on calcium signaling at the Y1 receptor (no effect upon inhibition of phospholipase C, protein kinase C or protein kinase D) but instead dependent on Gβ/γ and associated signaling pathways that activate PI3-kinase. Although inhibition of the epidermal-growth factor receptor tyrosine kinase did not influence NPY-induced ERK1/2 activation, we show that the inhibition of insulin growth factor receptor IGFR by AG1024 completely blocks activation of ERK1/2 by the Y1 receptor. This Gβ/γ-PI3K-AG1024-sensitive pathway does not involve activation of IGFR through the release of a soluble ligand by metalloproteinases since it is not affected by the metalloproteinase inhibitor marimastat. Finally, we found that a similar pathway, sensitive to wortmannin-AG1024 but insensitive to marimastat, is implicated in activation of ERK signaling in HEK293 cells by endogenously expressed GPCRs coupled to Gq-protein (muscarinic M3 receptors) or coupled to Gs-protein (endothelin ETB receptors). Our analysis is the first to show that β-arrestin recruitment to the NPY Y1 receptor is not necessary for MAPK activation by this receptor but that transactivation of the IGFR receptor is required.

  17. Ligand-dependent responses of the silkworm prothoracicotropic hormone receptor, Torso, are maintained by unusual intermolecular disulfide bridges in the transmembrane region.

    PubMed

    Konogami, Tadafumi; Yang, Yiwen; Ogihara, Mari H; Hikiba, Juri; Kataoka, Hiroshi; Saito, Kazuki

    2016-03-01

    The insect membrane-protein, Torso, is a member of the receptor-tyrosine-kinase family, and is activated by its ligand, prothoracicotropic hormone (PTTH). Although PTTH is one of the most important regulators of insect development, the mechanism of Torso activation by the hormone has remained elusive. In this study, using heterologous expression in cultured Drosophila S2 cells, we detected ligand-independent dimerization of silkworm Torso, and found that the receptor molecules in the dimer were linked by intermolecular disulfide bridges. By examining the oligomerization states of several truncation and substitution mutants of Torso, atypical cysteine residues in the transmembrane region were identified as being responsible for the intermolecular linkage in the dimer. The replacement of all of the cysteines in the region with phenylalanines abolished the disulfide-bond-mediated dimerization; however, non-covalent dimerization of the mutant was detected using a cross-linking reagent, both with and without ligand stimulation. This non-covalent dimerization caused apparent receptor autophosphorylation independently of the ligand stimulation, but did not promote the ERK phosphorylation in the downstream signaling pathway. The unique Torso structure with the intermolecular disulfide bridges in the transmembrane region is necessary to maintain the ligand-dependent receptor functions of autophosphorylation and downstream activation.

  18. Role of PHD fingers and COOH-terminal 30 amino acids in AIRE transactivation activity.

    PubMed

    Meloni, Alessandra; Incani, Federica; Corda, Denise; Cao, Antonio; Rosatelli, Maria Cristina

    2008-02-01

    Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomic autoimmune disease resulting from the defective function of a gene codifying for a transcription factor named autoimmune regulation (AIRE). The AIRE protein contains several domains among which two PHD fingers involved in the transcriptional activation. We investigated the function of the two PHD finger domains and the COOH terminal portion of AIRE by using several mutated constructs transfected in mammalian cells and a luciferase reporter assay. The results predict that the second PHD as well as the COOH terminal regions have marked transactivational properties. The COOH terminal region contains the fourth LXXLL and the PXXPXP motifs which play a critical role in mediating the transactivation capacity of the AIRE protein. Our study provides a definition of the role of the PHD fingers in transactivation and identifies a new transactivation domain of the AIRE protein localized in the COOH terminal region.

  19. Interactions between the Class II Transactivator and CREB Binding Protein Increase Transcription of Major Histocompatibility Complex Class II Genes

    PubMed Central

    Fontes, Joseph D.; Kanazawa, Satoshi; Jean, Dickson; Peterlin, B. Matija

    1999-01-01

    Class II major histocompatibility (class II) genes are regulated in a B-cell-specific and gamma interferon-inducible fashion. The master switch for the expression of these genes is the class II transactivator (CIITA). In this report, we demonstrate that one of the functions of CIITA is to recruit the CREB binding protein (CBP) to class II promoters. Not only functional but also specific binding interactions between CIITA and CBP were demonstrated. Moreover, a dominant negative form of CBP decreased the activity of class II promoters and levels of class II determinants on the surface of cells. Finally, the inhibition of class II gene expression by the glucocorticoid hormone could be attributed to the squelching of CBP by the glucocorticoid receptor. We conclude that CBP, a histone acetyltransferase, plays an important role in the transcription of class II genes. PMID:9858618

  20. Pigment-cell-specific genes from fibroblasts are transactivated after chromosomal transfer into melanoma cells.

    PubMed Central

    Powers, T P; Shows, T B; Davidson, R L

    1994-01-01

    Human and mouse fibroblast chromosomes carrying tyrosinase or b-locus genes were introduced, by microcell hybridization, into pigmented Syrian hamster melanoma cells, and the microcell hybrids were tested for transactivation of the fibroblast tyrosinase and b-locus genes. By using species-specific PCR amplification to distinguish fibroblast and melanoma cDNAs, it was demonstrated that the previously silent fibroblast tyrosinase and b-locus genes were transactivated following chromosomal transfer into pigmented melanoma cells. However, transactivation of the mouse fibroblast tyrosinase gene was unstable in microcell hybrid subclones and possibly dependent on a second fibroblast locus that could have segregated in the subclones. This second locus was not necessary for transactivation of the fibroblast b-locus gene, thus demonstrating noncoordinate transactivation of fibroblast tyrosinase and b-locus genes. Transactivation of the fibroblast tyrosinase gene in microcell hybrids apparently is dependent on the absence of a putative fibroblast extinguisher locus for tyrosinase gene expression, which presumably is responsible for the extinction of pigmentation in hybrids between karyotypically complete fibroblasts and melanoma cells. Images PMID:8289799

  1. Pigment-cell-specific genes from fibroblasts are transactivated after chromosomal transfer into melanoma cells

    SciTech Connect

    Powers, T.P.; Davidson, R.L.; Shows, T.B.

    1994-02-01

    Human and mouse fibroblast chromosomes carrying tyrosinase or b-locus genes were introduced, by microcell hybridization, into pigmented Syrian hamster melanoma cells, and the microcell hybrids were tested for transactivation of the fibroblast tyrosinase and b-locus genes. By using species-specific PCR amplification to distinguish fibroblast and melanoma cDNAs, it was demonstrated that the previously silent fibroblast tyrosinase and b-locus genes were transactivated following chromosomal transfer into pigmented melanoma cells. However, transactivation of the mouse fibroblast tyrosinase gene was unstable in microcell hybrid subclones and possibly dependent on a second fibroblast locus that could have segregated in the subclones. This second locus was not necessary for transactivation of the fibroblast b-locus gene, thus demonstrating noncoordinate transactivation of fibroblast tyrosinase and b-locus genes. Transactivation of the fibroblast tyrosinase gene in microcell hybrids apparently is dependent on the absence of a putative fibroblast extinguisher locus for tyrosinase gene expression, which presumably is responsible for the extinction of pigmentation in hybrids between karyotypically complete fibroblasts and melanoma cells. 46 refs., 5 figs., 2 tabs.

  2. A functional siRNA screen identifies genes modulating angiotensin II-mediated EGFR transactivation.

    PubMed

    George, Amee J; Purdue, Brooke W; Gould, Cathryn M; Thomas, Daniel W; Handoko, Yanny; Qian, Hongwei; Quaife-Ryan, Gregory A; Morgan, Kylie A; Simpson, Kaylene J; Thomas, Walter G; Hannan, Ross D

    2013-12-01

    The angiotensin type 1 receptor (AT1R) transactivates the epidermal growth factor receptor (EGFR) to mediate cellular growth, however, the molecular mechanisms involved have not yet been resolved. To address this, we performed a functional siRNA screen of the human kinome in human mammary epithelial cells that demonstrate a robust AT1R-EGFR transactivation. We identified a suite of genes encoding proteins that both positively and negatively regulate AT1R-EGFR transactivation. Many candidates are components of EGFR signalling networks, whereas others, including TRIO, BMX and CHKA, have not been previously linked to EGFR transactivation. Individual knockdown of TRIO, BMX or CHKA attenuated tyrosine phosphorylation of the EGFR by angiotensin II stimulation, but this did not occur following direct stimulation of the EGFR with EGF, indicating that these proteins function between the activated AT1R and the EGFR. Further investigation of TRIO and CHKA revealed that their activity is likely to be required for AT1R-EGFR transactivation. CHKA also mediated EGFR transactivation in response to another G protein-coupled receptor (GPCR) ligand, thrombin, indicating a pervasive role for CHKA in GPCR-EGFR crosstalk. Our study reveals the power of unbiased, functional genomic screens to identify new signalling mediators important for tissue remodelling in cardiovascular disease and cancer. PMID:24046455

  3. Delineation of a small region within the major transactivation domain of the human glucocorticoid receptor that mediates transactivation of gene expression.

    PubMed Central

    Dahlman-Wright, K; Almlöf, T; McEwan, I J; Gustafsson, J A; Wright, A P

    1994-01-01

    Previous deletion analysis localized the major transactivation function of the human glucocorticoid receptor to a 185-amino acid segment close to the N terminus of the receptor protein. This region was named tau 1 [Hollenberg, S. M. & Evans, R. M. (1988) Cell 55, 899-906]. To delineate the smallest active region within tau 1, we have systematically tested the transactivation capacity of deletion derivatives of the tau 1 domain, fused to the glucocorticoid receptor DNA-binding domain, in yeast cells. Internal scanning deletions suggested that residues near the C terminus of tau 1 are most important for activity. Deletions of N-terminal and C-terminal sequences identified a 41-amino acid "core" region near the C terminus of tau 1 that is crucial for tau 1 function. Small peptide fragments containing the tau 1 core region are competent for transactivation, while regions outside the tau 1 core are not active. We have previously demonstrated that the intact tau 1 domain squelches the activity of a minimal promoter in vivo and in vitro, suggesting involvement of interactions with a component/components of the basal transcription machinery in the mechanism of transactivation. This activity was maintained in the tau 1 core-containing segments. Images PMID:8127854

  4. Analysis of cytochrome P450 CYP119 ligand-dependent conformational dynamics by two-dimensional NMR and X-ray crystallography.

    PubMed

    Basudhar, Debashree; Madrona, Yarrow; Kandel, Sylvie; Lampe, Jed N; Nishida, Clinton R; de Montellano, Paul R Ortiz

    2015-04-17

    Defining the conformational states of cytochrome P450 active sites is critical for the design of agents that minimize drug-drug interactions, the development of isoform-specific P450 inhibitors, and the engineering of novel oxidative catalysts. We used two-dimensional (1)H,(15)N HSQC chemical shift perturbation mapping of (15)N-labeled Phe residues and x-ray crystallography to examine the ligand-dependent conformational dynamics of CYP119. Active site Phe residues were most affected by the binding of azole inhibitors and fatty acid substrates, in agreement with active site localization of the conformational changes. This was supported by crystallography, which revealed movement of the F-G loop with various azoles. Nevertheless, the NMR chemical shift perturbations caused by azoles and substrates were distinguishable. The absence of significant chemical shift perturbations with several azoles revealed binding of ligands to an open conformation similar to that of the ligand-free state. In contrast, 4-phenylimidazole caused pronounced NMR changes involving Phe-87, Phe-144, and Phe-153 that support the closed conformation found in the crystal structure. The same closed conformation is observed by NMR and crystallography with a para-fluoro substituent on the 4-phenylimidazole, but a para-chloro or bromo substituent engendered a second closed conformation. An open conformation is thus favored in solution with many azole ligands, but para-substituted phenylimidazoles give rise to two closed conformations that depend on the size of the para-substituent. The results suggest that ligands selectively stabilize discrete cytochrome P450 conformational states.

  5. Analysis of Cytochrome P450 CYP119 Ligand-dependent Conformational Dynamics by Two-dimensional NMR and X-ray Crystallography*

    PubMed Central

    Basudhar, Debashree; Madrona, Yarrow; Kandel, Sylvie; Lampe, Jed N.; Nishida, Clinton R.; de Montellano, Paul R. Ortiz

    2015-01-01

    Defining the conformational states of cytochrome P450 active sites is critical for the design of agents that minimize drug-drug interactions, the development of isoform-specific P450 inhibitors, and the engineering of novel oxidative catalysts. We used two-dimensional 1H,15N HSQC chemical shift perturbation mapping of 15N-labeled Phe residues and x-ray crystallography to examine the ligand-dependent conformational dynamics of CYP119. Active site Phe residues were most affected by the binding of azole inhibitors and fatty acid substrates, in agreement with active site localization of the conformational changes. This was supported by crystallography, which revealed movement of the F-G loop with various azoles. Nevertheless, the NMR chemical shift perturbations caused by azoles and substrates were distinguishable. The absence of significant chemical shift perturbations with several azoles revealed binding of ligands to an open conformation similar to that of the ligand-free state. In contrast, 4-phenylimidazole caused pronounced NMR changes involving Phe-87, Phe-144, and Phe-153 that support the closed conformation found in the crystal structure. The same closed conformation is observed by NMR and crystallography with a para-fluoro substituent on the 4-phenylimidazole, but a para-chloro or bromo substituent engendered a second closed conformation. An open conformation is thus favored in solution with many azole ligands, but para-substituted phenylimidazoles give rise to two closed conformations that depend on the size of the para-substituent. The results suggest that ligands selectively stabilize discrete cytochrome P450 conformational states. PMID:25670859

  6. Polycomb recruitment at the Class II transactivator gene.

    PubMed

    Boyd, Nathaniel H; Morgan, Julie E; Greer, Susanna F

    2015-10-01

    The Class II Transactivator (CIITA) is the master regulator of Major Histocompatibility Class II (MHC II) genes. Transcription of CIITA through the IFN-γ inducible CIITA promoter IV (CIITA pIV) during activation is characterized by a decrease in trimethylation of histone H3 lysine 27 (H3K27me3), catalyzed by the histone methyltransferase Enhancer of Zeste Homolog 2 (EZH2). While EZH2 is the known catalytic subunit of the Polycomb Repressive Complex 2 (PRC2) and is present at the inactive CIITA pIV, the mechanism of PRC2 recruitment to mammalian promoters remains unknown. Here we identify two DNA-binding proteins, which interact with and regulate PRC2 recruitment to CIITA pIV. We demonstrate Yin Yang 1 (YY1) and Jumonji domain containing protein 2 (JARID2) are binding partners along with EZH2 in mammalian cells. Upon IFN-γ stimulation, YY1 dissociates from CIITA pIV while JARID2 binding to CIITA pIV increases, suggesting novel roles for these proteins in regulating expression of CIITA pIV. Knockdown of YY1 and JARID2 yields decreased binding of EZH2 and H3K27me3 at CIITA pIV, suggesting important roles for YY1 and JARID2 at CIITA pIV. JARID2 knockdown also results in significantly elevated levels of CIITA mRNA upon IFN-γ stimulation. This study is the first to identify novel roles of YY1 and JARID2 in the epigenetic regulation of the CIITA pIV by recruitment of PRC2. Our observations indicate the importance of JARID2 in CIITA pIV silencing, and also provide a novel YY1-JARID2-PRC2 regulatory complex as a possible explanation of differential PRC2 recruitment at inducible versus permanently silenced genes.

  7. Recipient myeloid-derived immunomodulatory cells induce PD-1 ligand-dependent donor CD4+Foxp3+ regulatory T cell proliferation and donor-recipient immune tolerance after murine nonmyeloablative bone marrow transplantation.

    PubMed

    van der Merwe, Marie; Abdelsamed, Hossam A; Seth, Aman; Ong, Taren; Vogel, Peter; Pillai, Asha B

    2013-12-01

    We showed previously that nonmyeloablative total lymphoid irradiation/rabbit anti-thymocyte serum (TLI/ATS) conditioning facilitates potent donor-recipient immune tolerance following bone marrow transplantation (BMT) across MHC barriers via recipient invariant NKT (iNKT) cell-derived IL-4-dependent expansion of donor Foxp3(+) naturally occurring regulatory T cells (nTregs). In this study, we report a more specific mechanism. Wild-type (WT) BALB/c (H-2(d)) hosts were administered TLI/ATS and BMT from WT or STAT6(-/-) C57BL/6 (H-2(b)) donors. Following STAT6(-/-) BMT, donor nTregs demonstrated no loss of proliferation in vivo, indicating that an IL-4-responsive population in the recipient, rather than the donor, drives donor nTreg proliferation. In graft-versus-host disease (GVHD) target organs, three recipient CD11b(+) cell subsets (Gr-1(high)CD11c(-), Gr-1(int)CD11c(-), and Gr-1(low)CD11c(+)) were enriched early after TLI/ATS + BMT versus total body irradiation/ATS + BMT. Gr-1(low)CD11c(+) cells induced potent H-2K(b+)CD4(+)Foxp3(+) nTreg proliferation in vitro in 72-h MLRs. Gr-1(low)CD11c(+) cells were reduced significantly in STAT6(-/-) and iNKT cell-deficient Jα18(-/-) BALB/c recipients after TLI/ATS + BMT. Depletion of CD11b(+) cells resulted in severe acute GVHD, and adoptive transfer of WT Gr-1(low)CD11c(+) cells to Jα18(-/-) BALB/c recipients of TLI/ATS + BMT restored day-6 donor Foxp3(+) nTreg proliferation and protection from CD8 effector T cell-mediated GVHD. Blockade of programmed death ligand 1 and 2, but not CD40, TGF-β signaling, arginase 1, or iNOS, inhibited nTreg proliferation in cocultures of recipient-derived Gr-1(low)CD11c(+) cells with donor nTregs. Through iNKT-dependent Th2 polarization, myeloid-derived immunomodulatory dendritic cells are expanded after nonmyeloablative TLI/ATS conditioning and allogeneic BMT, induce PD-1 ligand-dependent donor nTreg proliferation, and maintain potent graft-versus-host immune tolerance.

  8. Muscarinic Type 3 Receptor Induces Cytoprotective Signaling in Salivary Gland Cells through Epidermal Growth Factor Receptor Transactivation

    PubMed Central

    Kajiya, Mikihito; Ichimonji, Isao; Min, Christine; Zhu, Tongbo; Jin, Jun-O; Yu, Qing; Almazrooa, Soulafa A.; Cha, Seunghee

    2012-01-01

    Muscarinic type 3 receptor (M3R) plays a pivotal role in the induction of glandular fluid secretions. Although M3R is often the target of autoantibodies in Sjögren's syndrome (SjS), chemical agonists for M3R are clinically used to stimulate saliva secretion in patients with SjS. Aside from its activity in promoting glandular fluid secretion, however, it is unclear whether activation of M3R is related to other biological events in SjS. This study aimed to investigate the cytoprotective effect of chemical agonist-mediated M3R activation on apoptosis induced in human salivary gland (HSG) cells. Carbachol (CCh), a muscarinic receptor-specific agonist, abrogated tumor necrosis factor α/interferon γ-induced apoptosis through pathways involving caspase 3/7, but its cytoprotective effect was decreased by a M3R antagonist, a mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) inhibitor, a phosphatidylinositol 3-kinase/Akt inhibitor, or an epidermal growth factor receptor (EGFR) inhibitor. Ligation of M3R with CCh transactivated EGFR and phosphorylated ERK and Akt, the downstream targets of EGFR. Inhibition of intracellular calcium release or protein kinase C δ, both of which are involved in the cell signaling of M3R-mediated fluid secretion, did not affect CCh-induced ERK or Akt phosphorylation. CCh stimulated Src phosphorylation and binding to EGFR. A Src inhibitor attenuated the CCh/M3R-induced cytoprotective effect and EGFR transactivation cascades. Overall, these results indicated that CCh/M3R induced transactivation of EGFR through Src activation leading to ERK and Akt phosphorylation, which in turn suppressed caspase 3/7-mediated apoptotic signals in HSG cells. This study, for the first time, proposes that CCh-mediated M3R activation can promote not only fluid secretion but also survival of salivary gland cells in the inflammatory context of SjS. PMID:22511543

  9. Zinc Finger and X-Linked Factor (ZFX) Binds to Human SET Transcript 2 Promoter and Transactivates SET Expression

    PubMed Central

    Xu, Siliang; Duan, Ping; Li, Jinping; Senkowski, Tristan; Guo, Fengbiao; Chen, Haibin; Romero, Alberto; Cui, Yugui; Liu, Jiayin; Jiang, Shi-Wen

    2016-01-01

    SET (SE Translocation) protein carries out multiple functions including those for protein phosphatase 2A (PP2A) inhibition, histone modification, DNA repair, and gene regulation. SET overexpression has been detected in brain neurons of patients suffering Alzheimer’s disease, follicle theca cells of Polycystic Ovary Syndrome (PCOS) patients, and ovarian cancer cells, indicating that SET may play a pathological role for these disorders. SET transcript 2, produced by a specific promoter, represents a major transcript variant in different cell types. In this study, we characterized the transcriptional activation of human SET transcript 2 promoter in HeLa cells. Promoter deletion experiments and co-transfection assays indicated that ZFX, the Zinc finger and X-linked transcription factor, was able to transactivate the SET promoter. A proximal promoter region containing four ZFX-binding sites was found to be critical for the ZFX-mediated transactivation. Mutagenesis study indicated that the ZFX-binding site located the closest to the transcription start site accounted for most of the ZFX-mediated transactivity. Manipulation of ZFX levels by overexpression or siRNA knockdown confirmed the significance and specificity of the ZFX-mediated SET promoter activation. Chromatin immunoprecipitation results verified the binding of ZFX to its cognate sites in the SET promoter. These findings have led to identification of ZFX as an upstream factor regulating SET gene expression. More studies are required to define the in vivo significance of this mechanism, and specifically, its implication for several benign and malignant diseases related to SET dysregulation. PMID:27775603

  10. The nucleotide-binding domain of NLRC5 is critical for nuclear import and transactivation activity

    SciTech Connect

    Meissner, Torsten B.; Li, Amy; Liu, Yuen-Joyce; Gagnon, Etienne; Kobayashi, Koichi S.

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer NLRC5 requires an intact NLS for its function as MHC class I transactivator. Black-Right-Pointing-Pointer Nuclear presence of NLRC5 is required for MHC class I induction. Black-Right-Pointing-Pointer Nucleotide-binding controls nuclear import and transactivation activity of NLRC5. -- Abstract: Major histocompatibility complex (MHC) class I and class II are crucial for the function of the human adaptive immune system. A member of the NLR (nucleotide-binding domain, leucine-rich repeat) protein family, NLRC5, has recently been identified as a transcriptional regulator of MHC class I and related genes. While a 'master regulator' of MHC class II genes, CIITA, has long been known, NLRC5 specifically associates with and transactivates the proximal promoters of MHC class I genes. In this study, we analyzed the molecular requirements of NLRC5 nuclear import and transactivation activity. We show that NLRC5-mediated MHC class I gene induction requires an intact nuclear localization signal and nuclear distribution of NLRC5. In addition, we find that the nucleotide-binding domain (NBD) of NLRC5 is critical not only for nuclear translocation but also for the transactivation of MHC class I genes. Changing the cellular localization of NLRC5 is likely to immediately impact MHC class I expression as well as MHC class I-mediated antigen presentation. NLRC5 may thus provide a promising target for the modulation of MHC class I antigen presentation, especially in the setting of transplant medicine.

  11. Molecular Basis of Ligand-Dependent Regulation of NadR, the Transcriptional Repressor of Meningococcal Virulence Factor NadA.

    PubMed

    Liguori, Alessia; Malito, Enrico; Lo Surdo, Paola; Fagnocchi, Luca; Cantini, Francesca; Haag, Andreas F; Brier, Sébastien; Pizza, Mariagrazia; Delany, Isabel; Bottomley, Matthew J

    2016-04-01

    Neisseria adhesin A (NadA) is present on the meningococcal surface and contributes to adhesion to and invasion of human cells. NadA is also one of three recombinant antigens in the recently-approved Bexsero vaccine, which protects against serogroup B meningococcus. The amount of NadA on the bacterial surface is of direct relevance in the constant battle of host-pathogen interactions: it influences the ability of the pathogen to engage human cell surface-exposed receptors and, conversely, the bacterial susceptibility to the antibody-mediated immune response. It is therefore important to understand the mechanisms which regulate nadA expression levels, which are predominantly controlled by the transcriptional regulator NadR (Neisseria adhesin A Regulator) both in vitro and in vivo. NadR binds the nadA promoter and represses gene transcription. In the presence of 4-hydroxyphenylacetate (4-HPA), a catabolite present in human saliva both under physiological conditions and during bacterial infection, the binding of NadR to the nadA promoter is attenuated and nadA expression is induced. NadR also mediates ligand-dependent regulation of many other meningococcal genes, for example the highly-conserved multiple adhesin family (maf) genes, which encode proteins emerging with important roles in host-pathogen interactions, immune evasion and niche adaptation. To gain insights into the regulation of NadR mediated by 4-HPA, we combined structural, biochemical, and mutagenesis studies. In particular, two new crystal structures of ligand-free and ligand-bound NadR revealed (i) the molecular basis of 'conformational selection' by which a single molecule of 4-HPA binds and stabilizes dimeric NadR in a conformation unsuitable for DNA-binding, (ii) molecular explanations for the binding specificities of different hydroxyphenylacetate ligands, including 3Cl,4-HPA which is produced during inflammation, (iii) the presence of a leucine residue essential for dimerization and conserved in

  12. Molecular Basis of Ligand-Dependent Regulation of NadR, the Transcriptional Repressor of Meningococcal Virulence Factor NadA

    PubMed Central

    Liguori, Alessia; Malito, Enrico; Lo Surdo, Paola; Fagnocchi, Luca; Cantini, Francesca; Haag, Andreas F.; Brier, Sébastien; Pizza, Mariagrazia; Delany, Isabel; Bottomley, Matthew J.

    2016-01-01

    Neisseria adhesin A (NadA) is present on the meningococcal surface and contributes to adhesion to and invasion of human cells. NadA is also one of three recombinant antigens in the recently-approved Bexsero vaccine, which protects against serogroup B meningococcus. The amount of NadA on the bacterial surface is of direct relevance in the constant battle of host-pathogen interactions: it influences the ability of the pathogen to engage human cell surface-exposed receptors and, conversely, the bacterial susceptibility to the antibody-mediated immune response. It is therefore important to understand the mechanisms which regulate nadA expression levels, which are predominantly controlled by the transcriptional regulator NadR (Neisseria adhesin A Regulator) both in vitro and in vivo. NadR binds the nadA promoter and represses gene transcription. In the presence of 4-hydroxyphenylacetate (4-HPA), a catabolite present in human saliva both under physiological conditions and during bacterial infection, the binding of NadR to the nadA promoter is attenuated and nadA expression is induced. NadR also mediates ligand-dependent regulation of many other meningococcal genes, for example the highly-conserved multiple adhesin family (maf) genes, which encode proteins emerging with important roles in host-pathogen interactions, immune evasion and niche adaptation. To gain insights into the regulation of NadR mediated by 4-HPA, we combined structural, biochemical, and mutagenesis studies. In particular, two new crystal structures of ligand-free and ligand-bound NadR revealed (i) the molecular basis of ‘conformational selection’ by which a single molecule of 4-HPA binds and stabilizes dimeric NadR in a conformation unsuitable for DNA-binding, (ii) molecular explanations for the binding specificities of different hydroxyphenylacetate ligands, including 3Cl,4-HPA which is produced during inflammation, (iii) the presence of a leucine residue essential for dimerization and conserved in

  13. Evolution of p53 Transactivation Specificity through the Lens of a Yeast-Based Functional Assay

    PubMed Central

    Lion, Mattia; Raimondi, Ivan; Donati, Stefano; Jousson, Olivier; Ciribilli, Yari; Inga, Alberto

    2015-01-01

    Co-evolution of transcription factors (TFs) with their respective cis-regulatory network enhances functional diversity in the course of evolution. We present a new approach to investigate transactivation capacity of sequence-specific TFs in evolutionary studies. Saccharomyces cerevisiae was used as an in vivo test tube and p53 proteins derived from human and five commonly used animal models were chosen as proof of concept. p53 is a highly conserved master regulator of environmental stress responses. Previous reports indicated conserved p53 DNA binding specificity in vitro, even for evolutionary distant species. We used isogenic yeast strains where p53-dependent transactivation was measured towards chromosomally integrated p53 response elements (REs). Ten REs were chosen to sample a wide range of DNA binding affinity and transactivation capacity for human p53 and proteins were expressed at two levels using an inducible expression system. We showed that the assay is amenable to study thermo-sensitivity of frog p53, and that chimeric constructs containing an ectopic transactivation domain could be rapidly developed to enhance the activity of proteins, such as fruit fly p53, that are poorly effective in engaging the yeast transcriptional machinery. Changes in the profile of relative transactivation towards the ten REs were measured for each p53 protein and compared to the profile obtained with human p53. These results, which are largely independent from relative p53 protein levels, revealed widespread evolutionary divergence of p53 transactivation specificity, even between human and mouse p53. Fruit fly and human p53 exhibited the largest discrimination among REs while zebrafish p53 was the least selective. PMID:25668429

  14. Evolution of p53 transactivation specificity through the lens of a yeast-based functional assay.

    PubMed

    Lion, Mattia; Raimondi, Ivan; Donati, Stefano; Jousson, Olivier; Ciribilli, Yari; Inga, Alberto

    2015-01-01

    Co-evolution of transcription factors (TFs) with their respective cis-regulatory network enhances functional diversity in the course of evolution. We present a new approach to investigate transactivation capacity of sequence-specific TFs in evolutionary studies. Saccharomyces cerevisiae was used as an in vivo test tube and p53 proteins derived from human and five commonly used animal models were chosen as proof of concept. p53 is a highly conserved master regulator of environmental stress responses. Previous reports indicated conserved p53 DNA binding specificity in vitro, even for evolutionary distant species. We used isogenic yeast strains where p53-dependent transactivation was measured towards chromosomally integrated p53 response elements (REs). Ten REs were chosen to sample a wide range of DNA binding affinity and transactivation capacity for human p53 and proteins were expressed at two levels using an inducible expression system. We showed that the assay is amenable to study thermo-sensitivity of frog p53, and that chimeric constructs containing an ectopic transactivation domain could be rapidly developed to enhance the activity of proteins, such as fruit fly p53, that are poorly effective in engaging the yeast transcriptional machinery. Changes in the profile of relative transactivation towards the ten REs were measured for each p53 protein and compared to the profile obtained with human p53. These results, which are largely independent from relative p53 protein levels, revealed widespread evolutionary divergence of p53 transactivation specificity, even between human and mouse p53. Fruit fly and human p53 exhibited the largest discrimination among REs while zebrafish p53 was the least selective. PMID:25668429

  15. Astrocytic transactivation by alpha2A-adrenergic and 5-HT2B serotonergic signaling.

    PubMed

    Peng, Liang; Li, Baoman; Du, Ting; Kong, Ebenezer K C; Hu, Xiaoling; Zhang, Shiquen; Shan, Xiaolei; Zhang, Meixia

    2010-11-01

    EGF receptor transactivation has been known for more than ten years. It is a signal pathway in which a G-protein-coupled receptor (GPCR) signal leads to release of a growth factor, which in turn activates the EGF receptor-tyrosine kinase in the same or adjacent cells. Astrocytes express a number of GPCRs and play key roles in brain function. Astrocytic transactivation is of special interest, since its autocrine effect may regulate gene expression and alter cell functions in the cells themselves and its paracrine effect may provide additional opportunities for cross-talk between astrocytes and their neighbors, such as neurons. The signal pathways of EGF transactivation are complicated. This does not only apply to the pathways leading to shedding of growth factor(s), but also to the downstream signal pathways of the EGF receptor, i.e., MAPK and PI3K. The latter may vary according to the type of growth factor released, the sites of tyrosine phosphorylation on the EGF receptor, and the duration of the phosphorylation. Using primary cell cultures we have found that dexmedetomidine, a specific alpha(2)-adrenergic receptor, induced shedding of HB-EGF from astrocytes, which in turn transactivated EGF receptors and stimulated astrocytic c-Fos and FosB expression. At the same time released HB-EGF protected neurons from injury caused by H(2)O(2). We have also confirmed dexmedetomidine transactivation in the brain in vivo. EGF transactivation by 5-HT(2B) receptor stimulation was responsible for up-regulation of cPLA(2) in astrocytes by fluoxetine, an antidepressant and inhibitor of the serotonin transporter, which also is a specific 5-HT(2B) agonist. PMID:20450946

  16. Wild-type human p53 transactivates the human proliferating cell nuclear antigen promoter

    SciTech Connect

    Shivakumar, C.V.; Brown, D.R.; Deb, S.; Deb, S.P.

    1995-12-01

    The p53 tumor suppressor protein negatively regulates cell growth and somatic mutations in the p53 gene lead to uncontrolled cell growth and oncogenesis. This report describes research which demonstrates, using a number of different cell lines, that at low levels, wild-type p53 transactivates the human proliferating cell nuclear antigen (PCNA) promoter. When expressed at similar levels, tumor-derived p53 mutants did not transactivate the PCNA promoter. It also reports the identification of a wild-type human p53-binding site on the human PCNA promote. 84 refs., 5 figs, 3 tabs.

  17. Transactivation of bad by vorinostat-induced acetylated p53 enhances doxorubicin-induced cytotoxicity in cervical cancer cells.

    PubMed

    Lee, Sook-Jeong; Hwang, Sung-Ook; Noh, Eun Joo; Kim, Dong-Uk; Nam, Miyoung; Kim, Jong Hyeok; Nam, Joo Hyun; Hoe, Kwang-Lae

    2014-02-14

    Vorinostat (VOR) has been reported to enhance the cytotoxic effects of doxorubicin (DOX) with fewer side effects because of the lower DOX dosage in breast cancer cells. In this study, we investigated the novel mechanism underlying the synergistic cytotoxic effects of VOR and DOX co-treatment in cervical cancer cells HeLa, CaSki and SiHa cells. Co-treatment with VOR and DOX at marginal doses led to the induction of apoptosis through caspase-3 activation, poly (ADP-ribose) polymerase cleavage and DNA micronuclei. Notably, the synergistic growth inhibition induced by the co-treatment was attributed to the upregulation of the pro-apoptotic protein Bad, as the silencing of Bad expression using small interfering RNA (siRNA) abolished the phenomenon. As siRNA against p53 did not result in an increase in acetylated p53 and the consequent upregulation of Bad, the observed Bad upregulation was mediated by acetylated p53. Moreover, a chromatin immunoprecipitation analysis showed that the co-treatment of HeLa cells with VOR and DOX increased the recruitment of acetylated p53 to the bad promoter, with consequent bad transactivation. Conversely, C33A cervical cancer cells containing mutant p53 co-treated with VOR and DOX did not exhibit Bad upregulation, acetylated p53 induction or consequent synergistic growth inhibition. Together, the synergistic growth inhibition of cervical cancer cell lines induced by co-treatment with VOR and DOX can be attributed to the upregulation of Bad, which is induced by acetylated p53. These results show for the first time that the acetylation of p53, rather than histones, is a mechanism for the synergistic growth inhibition induced by VOR and DOX co-treatments.

  18. Structure of the EGF receptor transactivation circuit integrates multiple signals with cell context

    SciTech Connect

    Joslin, Elizabeth J.; Shankaran, Harish; Opresko, Lee K.; Bollinger, Nikki; Lauffenburger, Douglas A.; Wiley, H. S.

    2010-05-10

    Transactivation of the epidermal growth factor receptor (EGFR) has been proposed to be a mechanism by which a variety of cellular inputs can be integrated into a single signaling pathway, but the regulatory topology of this important system is unclear. To understand the transactivation circuit, we first created a “non-binding” reporter for ligand shedding. We then quantitatively defined how signals from multiple agonists were integrated both upstream and downstream of the EGFR into the extracellular signal regulated kinase (ERK) cascade in human mammary epithelial cells. We found that transactivation is mediated by a recursive autocrine circuit where ligand shedding drives EGFR-stimulated ERK that in turn drives further ligand shedding. The time from shedding to ERK activation is fast (<5 min) whereas the recursive feedback is slow (>15 min). Simulations showed that this delay in positive feedback greatly enhanced system stability and robustness. Our results indicate that the transactivation circuit is constructed so that the magnitude of ERK signaling is governed by the sum of multiple direct inputs, while recursive, autocrine ligand shedding controls signal duration.

  19. Integrated cell-based platform to study EGFR activation and transactivation.

    PubMed

    Caruso, Marie-Elaine; Clément, Paule; Parent, Stéphane; Dupriez, Vincent; Bossé, Roger; Rouleau, Nathalie

    2013-09-01

    The epidermal growth factor receptor (EGFR) pathway is one of the most deregulated molecular pathways in human epithelial cancers. Many approved drugs were optimized to directly target EGFR but yielded only modest clinical improvement in cancer patients due to low efficacy and drug resistance. Transactivation of EGFR by other cell surface receptors such as G-protein-coupled receptors (GPCRs) was proposed to explain this lack of efficacy. Even if direct EGFR activation and transactivation by GPCR contribute to the activation of the same signaling pathways, they are often studied as independent events resulting in partial investigation of a drug's mechanism of action. We present a novel high-throughput approach that integrates interrogation of direct activation of EGFR and its transactivation via GPCR activation. Using distinct technology platforms, three readouts were used to measure (1) direct activation of GPCR via cyclic adenosine monophosphate (cAMP) detection, (2) direct activation of EGFR through the release of intracellular Ca(2+), and (3) EGFR transactivation by GPCR using the detection of p-extracellular-signal-regulated kinases 1/2 (p-ERK1/2). In addition to being simple, quick, and homogenous, our methods were shown to be more sensitive than those in current use. These enabling tools should improve the knowledge pertaining to GPCRs and receptor tyrosine kinases trans-regulation and facilitate the design of more potent and better targeted new therapeutic strategies.

  20. STRUCTURE OF THE EGF RECEPTOR TRANSACTIVATION CIRCUIT INTEGRATES MULTIPLE SIGNALS WITH CELL CONTEXT

    PubMed Central

    Joslin, Elizabeth J.; Shankaran, Harish; Opresko, Lee K.; Bollinger, Nikki; Lauffenburger, Douglas A.; Wiley, H. Steven

    2012-01-01

    Summary Transactivation of the epidermal growth factor receptor (EGFR) is thought to be a process by which a variety of cellular inputs can be integrated into a single signaling pathway through either stimulated proteolysis (shedding) of membrane-anchored EGFR ligands or by modification of the activity of the EGFR. As a first step towards building a predictive model of the EGFR transactivation circuit, we quantitatively defined how signals from multiple agonists were integrated both upstream and downstream of the EGFR to regulate extracellular signal regulated kinase (ERK) activity in human mammary epithelial cells. By using a “non-binding” reporter of ligand shedding, we found that transactivation triggers a positive feedback loop from ERK back to the EGFR such that ligand shedding drives EGFR-stimulated ERK that in turn drives further ligand shedding. Importantly, activated Ras and ERK levels were nearly linear functions of ligand shedding and the effect of multiple, sub-saturating inputs was additive. Simulations showed that ERK-mediated feedback through ligand shedding resulted in a stable steady-state level of activated ERK, but also showed that the extracellular environment can modulate the level of feedback. Our results suggest that the transactivation circuit acts as a context-dependent integrator and amplifier of multiple extracellular signals and that signal integration can effectively occur at multiple points in the EGFR pathway. PMID:20458382

  1. Proteomic Analysis of the Herpes Simplex Virus 1 Virion Protein 16 Transactivator Protein in Infected Cells

    PubMed Central

    Oh, Hyung Suk; Knipe, David M.

    2015-01-01

    The herpes simplex virus 1 VP16 tegument protein forms a transactivation complex with the cellular proteins HCF-1 and Oct-1 upon entry into the host cell. VP16 has also been shown to interact with a number of virion tegument proteins and viral glycoprotein H to promote viral assembly, but no comprehensive study of the VP16 proteome has been performed at early times post-infection. We therefore performed a proteomic analysis of VP16-interacting proteins at 3 hours post-infection. We confirmed the interaction of VP16 with HCF-1 and a large number of cellular Mediator complex proteins, but most surprisingly, we found that the major viral protein associating with VP16 is the ICP4 immediate-early transactivator protein. These results raise the potential for a new function for VP16 in associating with the immediate-early ICP4 and playing a role in transactivation of early and late gene expression, in addition to its well-documented function in transactivation of immediate-early gene expression. PMID:25809282

  2. Proteomic analysis of the herpes simplex virus 1 virion protein 16 transactivator protein in infected cells.

    PubMed

    Suk, Hyung; Knipe, David M

    2015-06-01

    The herpes simplex virus 1 virion protein 16 (VP16) tegument protein forms a transactivation complex with the cellular proteins host cell factor 1 (HCF-1) and octamer-binding transcription factor 1 (Oct-1) upon entry into the host cell. VP16 has also been shown to interact with a number of virion tegument proteins and viral glycoprotein H to promote viral assembly, but no comprehensive study of the VP16 proteome has been performed at early times postinfection. We therefore performed a proteomic analysis of VP16-interacting proteins at 3 h postinfection. We confirmed the interaction of VP16 with HCF-1 and a large number of cellular Mediator complex proteins, but most surprisingly, we found that the major viral protein associating with VP16 is the infected cell protein 4 (ICP4) immediate-early (IE) transactivator protein. These results raise the potential for a new function for VP16 in associating with the IE ICP4 and playing a role in transactivation of early and late gene expression, in addition to its well-documented function in transactivation of IE gene expression.

  3. Cyclin E/Cdk2, P/CAF, and E1A regulate the transactivation of the c-myc promoter by FOXM1

    SciTech Connect

    Wierstra, Inken Alves, Juergen

    2008-03-28

    FOXM1c transactivates the c-myc promoter by binding directly to its TATA-boxes. The present study demonstrates that the transactivation of the c-myc promoter by FOXM1c is enhanced by the key proliferation signal cyclin E/Cdk2, but repressed by P/CAF and the adenoviral oncoprotein E1A. Furthermore, FOXM1c interacts with the coactivator and histone acetyltransferase P/CAF. This study shows that, on the c-myc-P1 TATA-box, FOXM1c does not function simply as normal transcription factor just binding to an unusual site. Moreover, the inhibitory N-terminus of FOXM1c does not inhibit its transrepression domain or its EDA. Others reported that a cyclin/Cdk-binding LXL-motif of the splice variant FoxM1b is required for its interaction with Cdk2, Cdk1, and p27, its phosphorylation by Cdk1 and its activation by Cdc25B. In contrast, we now demonstrate that this LXL-motif is not required for the activation of FOXM1c by cyclin D1/Cdk4, cyclin E/Cdk and cyclin A/Cdk2 or for the repression of FOXM1c by p27.

  4. Leptin stimulates endothelin-1 expression via extracellular signal-regulated kinase by epidermal growth factor receptor transactivation in rat aortic smooth muscle cells.

    PubMed

    Chao, Hung-Hsing; Hong, Hong-Jye; Liu, Ju-Chi; Lin, Jia-Wei; Chen, Yen-Ling; Chiu, Wen-Ta; Wu, Chieh-Hsi; Shyu, Kou-Gi; Cheng, Tzu-Hurng

    2007-11-14

    Obesity is a major risk factor for the development of hypertension. Recent studies have suggested that leptin, a 167-amino acid peptide hormone produced by white adipose tissue, is related to the pathogenesis of obesity-related hypertension. However, the signaling mechanisms underlying the effects of leptin remain to be extensively examined. In this study, we found that leptin induced extracellular signal-regulated kinase phosphorylation and endothelin-1 expression in rat aortic smooth muscle cells. Both PD98059 and U0126, inhibitors of the upstream activator of mitogen-activated protein kinase kinase, inhibited augmentation of endothelin-1 expression stimulated with leptin. Leptin induced significant tyrosine phosphorylation of epidermal growth factor receptor, which was significantly attenuated by two inhibitors, an epidermal growth factor receptor tyrosine kinase inhibitor, AG1478, and a broad-spectrum matrix metalloproteinase inhibitor, GM6001. This indicates that the pathway of epidermal growth factor receptor transactivation induced by leptin is dependent on proteolytically released epidermal growth factor receptor ligands. Pretreatment of cells with AG1478 significantly reduced the degree of phosphorylation of extracellular signal-regulated kinase and endothelin-1 expression. Our results reveal that epidermal growth factor receptor transactivation is involved in the leptin signaling pathway in vascular smooth muscle cells, which may be related to the increased risk of hypertension and other cardiovascular diseases in obese subjects. PMID:17678888

  5. Transactivation specificity is conserved among p53 family proteins and depends on a response element sequence code

    PubMed Central

    Ciribilli, Yari; Monti, Paola; Bisio, Alessandra; Nguyen, H. Thien; Ethayathulla, Abdul S.; Ramos, Ana; Foggetti, Giorgia; Menichini, Paola; Menendez, Daniel; Resnick, Michael A.; Viadiu, Hector; Fronza, Gilberto; Inga, Alberto

    2013-01-01

    Structural and biochemical studies have demonstrated that p73, p63 and p53 recognize DNA with identical amino acids and similar binding affinity. Here, measuring transactivation activity for a large number of response elements (REs) in yeast and human cell lines, we show that p53 family proteins also have overlapping transactivation profiles. We identified mutations at conserved amino acids of loops L1 and L3 in the DNA-binding domain that tune the transactivation potential nearly equally in p73, p63 and p53. For example, the mutant S139F in p73 has higher transactivation potential towards selected REs, enhanced DNA-binding cooperativity in vitro and a flexible loop L1 as seen in the crystal structure of the protein–DNA complex. By studying, how variations in the RE sequence affect transactivation specificity, we discovered a RE-transactivation code that predicts enhanced transactivation; this correlation is stronger for promoters of genes associated with apoptosis. PMID:23892287

  6. Glucocorticoid Repression of Inflammatory Gene Expression Shows Differential Responsiveness by Transactivation- and Transrepression-Dependent Mechanisms

    PubMed Central

    King, Elizabeth M.; Chivers, Joanna E.; Rider, Christopher F.; Minnich, Anne; Giembycz, Mark A.; Newton, Robert

    2013-01-01

    Binding of glucocorticoid to the glucocorticoid receptor (GR/NR3C1) may repress inflammatory gene transcription via direct, protein synthesis-independent processes (transrepression), or by activating transcription (transactivation) of multiple anti-inflammatory/repressive factors. Using human pulmonary A549 cells, we showed that 34 out of 39 IL-1β-inducible mRNAs were repressed to varying degrees by the synthetic glucocorticoid, dexamethasone. Whilst these repressive effects were GR-dependent, they did not correlate with either the magnitude of IL-1β-inducibility or the NF-κB-dependence of the inflammatory genes. This suggests that induction by IL-1β and repression by dexamethasone are independent events. Roles for transactivation were investigated using the protein synthesis inhibitor, cycloheximide. However, cycloheximide reduced the IL-1β-dependent expression of 13 mRNAs, which, along with the 5 not showing repression by dexamethasone, were not analysed further. Of the remaining 21 inflammatory mRNAs, cycloheximide significantly attenuated the dexamethasone-dependent repression of 11 mRNAs that also showed a marked time-dependence to their repression. Such effects are consistent with repression occurring via the de novo synthesis of a new product, or products, which subsequently cause repression (i.e., repression via a transactivation mechanism). Conversely, 10 mRNAs showed completely cycloheximide-independent, and time-independent, repression by dexamethasone. This is consistent with direct GR transrepression. Importantly, the inflammatory mRNAs showing attenuated repression by dexamethasone in the presence of cycloheximide also showed a significantly greater extent of repression and a higher potency to dexamethasone compared to those mRNAs showing cycloheximide-independent repression. This suggests that the repression of inflammatory mRNAs by GR transactivation-dependent mechanisms accounts for the greatest levels of repression and the most potent

  7. HIV-1 Tat transactivator recruits p300 and CREB-binding protein histone acetyltransferases to the viral promoter

    PubMed Central

    Marzio, Giuseppe; Tyagi, Mudit; Gutierrez, Maria Ines; Giacca, Mauro

    1998-01-01

    In cells infected with HIV type 1 (HIV-1), the integrated viral promoter is present in a chromatin-bound conformation and is transcriptionally silent in the absence of stimulation. The HIV-1 Tat protein binds to a stem-loop structure at the 5′ end of viral mRNA and relieves this inhibition by inducing a remodeling of the nucleosome arrangement downstream of the transcription-initiation site. Here we show that Tat performs this activity by recruiting to the viral long terminal repeat (LTR) the transcriptional coactivator p300 and the closely related CREB-binding protein (CBP), having histone acetyltransferase (HAT) activity. Tat associates with HAT activity in human nuclear extracts and binds to p300 and CBP both in vitro and in vivo. Integrity of the basic domain of Tat is essential for this interaction. By a quantitative chromatin immunoprecipitation assay we show that the delivery of recombinant Tat induces the association of p300 and CBP with the chromosomally integrated LTR promoter. Expression of human p300 in both human and rodent cells increases the levels of Tat transactivation of the integrated LTR. These results reinforce the evidence that p300 and CBP have a pivotal function at both cellular and viral promoters and demonstrate that they also can be recruited by an RNA-targeted activator. Additionally, these findings have important implications for the understanding of the mechanisms of HIV-1 latency and reactivation. PMID:9811832

  8. The ligand-binding domains of the thyroid hormone/retinoid receptor gene subfamily function in vivo to mediate heterodimerization, gene silencing, and transactivation.

    PubMed Central

    Qi, J S; Desai-Yajnik, V; Greene, M E; Raaka, B M; Samuels, H H

    1995-01-01

    The ligand-binding domains (LBDs) of the thyroid/retinoid receptor gene subfamily contain a series of heptad motifs important for dimeric interactions. This subfamily includes thyroid hormone receptors (T3Rs), all-trans retinoic acid (RA) receptors (RARs), 9-cis RA receptors (RARs and retinoid X receptors [RXRs]), the 1,25-dihydroxyvitamin D3 receptor (VDR), and the receptors that modulate the peroxisomal beta-oxidation pathway (PPARs). These receptors bind to their DNA response elements in vitro as heterodimers with the RXRs. Unliganded receptors in vivo, in particular the T3Rs, can mediate gene silencing and ligand converts these receptors into a transcriptionally active form. The in vivo interactions of these receptors with RXR were studied by using a GAL4-RXR chimera containing the yeast GAL4 DNA-binding domain and the LBD of RXR beta. GAL4-RXR activates transcription from GAL4 response elements in the presence of 9-cis RA. Unliganded T3R, which does not bind or activate GAL4 elements, represses the activation of GAL4-RXR by 9-cis RA in HeLa cells. However, addition of T3 alone leads to transcriptional activation. These findings suggest that T3R can repress or activate transcription while tethered to the LBD of GAL4-RXR and that heterodimerization can occur in vivo without stabilization by hormone response elements. Similar ligand-dependent activation was observed in HeLa cells expressing RAR, VDR, or PPAR and in GH4C1 cells from endogenous receptors. Replacement of the last 17 amino acids of the LBD of RXRbeta with the 90-amino-acid transactivating domain of the herpes simplex virus VP16 protein leads to a GAL4 constitutive activator that is repressed by wild-type T3R but not by a ninth heptad mutant that does not form heterodimers. This finding suggests that the ninth heptad or T3R is important for gene silencing and that the LBD of RXR does not exhibit silencing activity. This conclusion was verified with GAL4-LBD chimeras and with wild-type receptors in

  9. A novel antagonist anti-cMet antibody with antitumor activities targeting both ligand-dependent and ligand-independent c-Met receptors.

    PubMed

    Gonzalez, Alexandra; Broussas, Matthieu; Beau-Larvor, Charlotte; Haeuw, Jean-François; Boute, Nicolas; Robert, Alain; Champion, Thierry; Beck, Alain; Bailly, Christian; Corvaïa, Nathalie; Goetsch, Liliane

    2016-10-15

    c-Met is a prototypic member of a sub-family of RTKs. Inappropriate c-Met activation plays a crucial role in tumor formation, proliferation and metastasis. Using a key c-Met dimerization assay, a set of 12 murine whole IgG1 monoclonal antibodies was selected and a lead candidate, m224G11, was humanized by CDR-grafting and engineered to generate a divalent full antagonist humanized IgG1 antibody, hz224G11. Neither m224G11 nor hz224G11 bind to the murine c-Met receptor. Their antitumor activity was investigated in vitro in a set of experiments consistent with the reported pleiotropic effects mediated by c-Met and, in vivo, using several human tumor xenograft models. Both m224G11 and hz224G11 exhibited nanomolar affinities for the receptor and inhibited HGF binding, c-Met phosphorylation, and receptor dimerization in a similar fashion, resulting in a profound inhibition of all c-Met functions in vitro. These effects were presumably responsible for the inhibition of c-Met's major functions including cell proliferation, migration, invasion scattering, morphogenesis and angiogenesis. In addition to these in vitro properties, hz224G11 dramatically inhibits the growth of autocrine, partially autophosphorylated and c-Met amplified cell lines in vivo. Pharmacological studies performed on Hs746T gastric cancer xenografts demonstrate that hz224G11 strongly downregulates c-Met expression and phosphorylation. It also decreases the tumor mitotic index (Ki67) and induces apoptosis. Taken together, the in vitro and in vivo data suggest that hz224G11 is a promising candidate for the treatment of tumors. This antibody, now known as ABT-700 and currently in Phase I clinical trials, may provide a novel therapeutic approach to c-Met-expressing cancers.

  10. The 9aaTAD Transactivation Domains: From Gal4 to p53

    PubMed Central

    Havelka, Marek; Rezacova, Martina

    2016-01-01

    The family of the Nine amino acid Transactivation Domain, 9aaTAD family, comprises currently over 40 members. The 9aaTAD domains are universally recognized by the transcriptional machinery from yeast to man. We had identified the 9aaTAD domains in the p53, Msn2, Pdr1 and B42 activators by our prediction algorithm. In this study, their competence to activate transcription as small peptides was proven. Not surprisingly, we elicited immense 9aaTAD divergence in hundreds of identified orthologs and numerous examples of the 9aaTAD species' convergence. We found unforeseen similarity of the mammalian p53 with yeast Gal4 9aaTAD domains. Furthermore, we identified artificial 9aaTAD domains generated accidentally by others. From an evolutionary perspective, the observed easiness to generate 9aaTAD transactivation domains indicates the natural advantage for spontaneous generation of transcription factors from DNA binding precursors. PMID:27618436

  11. Dissection of Cauliflower Mosaic Virus Transactivator/Viroplasmin Reveals Distinct Essential Functions in Basic Virus Replication

    PubMed Central

    Kobayashi, Kappei; Hohn, Thomas

    2003-01-01

    Cauliflower mosaic virus (CaMV) transactivator/viroplasmin (Tav) is an essential multifunctional viral protein. Dissection of Tav by deletion mutagenesis revealed that the central region is essential for CaMV replication in single cells but that the N- and C-terminal parts are not. Strains with mutations in the central region were defective in the translational transactivator function and could be complemented by coexpressing Gag (capsid protein precursor) and Pol (polyprotein with protease, reverse transcriptase, and RNase H activity) from separate monocistronic plasmids. In contrast, total omission of Tav was only partially complemented by Gag and Pol overexpression from separate plasmids. These results indicate that CaMV basic replication requires both Tav-activated polycistronic translation and some posttranslational function(s) of Tav that is not affected by the deletions in the central region of Tav. PMID:12857928

  12. Exploitation of Herpesviral Transactivation Allows Quantitative Reporter Gene-Based Assessment of Virus Entry and Neutralization

    PubMed Central

    Reinhard, Henrike; Le, Vu Thuy Khanh; Ohlin, Mats; Hengel, Hartmut; Trilling, Mirko

    2011-01-01

    Herpesviral entry is a highly elaborated process requiring many proteins to act in precise conjunction. Neutralizing antibodies interfere with this process to abrogate viral infection. Based on promoter transactivation of a reporter gene we established a novel method to quantify herpesvirus entry and neutralization by antibodies. Following infection with mouse and human cytomegalovirus and Herpes simplex virus 1 we observed promoter transactivation resulting in substantial luciferase expression (>1000-fold). No induction was elicited by UV-inactivated viruses. The response was MOI-dependent and immunoblots confirmed a correlation between luciferase induction and pp72-IE1 expression. Monoclonal antibodies, immune sera and purified immunoglobulin preparations decreased virus-dependent luciferase induction dose-dependently, qualifying this approach as surrogate virus neutralization test. Besides the reduced hands-on time, this assay allows analysis of herpesvirus entry in semi-permissive and non-adherent cells, which were previously non-assessable but play significant roles in herpesvirus pathology. PMID:21264213

  13. The 9aaTAD Transactivation Domains: From Gal4 to p53.

    PubMed

    Piskacek, Martin; Havelka, Marek; Rezacova, Martina; Knight, Andrea

    2016-01-01

    The family of the Nine amino acid Transactivation Domain, 9aaTAD family, comprises currently over 40 members. The 9aaTAD domains are universally recognized by the transcriptional machinery from yeast to man. We had identified the 9aaTAD domains in the p53, Msn2, Pdr1 and B42 activators by our prediction algorithm. In this study, their competence to activate transcription as small peptides was proven. Not surprisingly, we elicited immense 9aaTAD divergence in hundreds of identified orthologs and numerous examples of the 9aaTAD species' convergence. We found unforeseen similarity of the mammalian p53 with yeast Gal4 9aaTAD domains. Furthermore, we identified artificial 9aaTAD domains generated accidentally by others. From an evolutionary perspective, the observed easiness to generate 9aaTAD transactivation domains indicates the natural advantage for spontaneous generation of transcription factors from DNA binding precursors. PMID:27618436

  14. Transactivation of Epidermal Growth Factor Receptor by G Protein-Coupled Receptors: Recent Progress, Challenges and Future Research

    PubMed Central

    Wang, Zhixiang

    2016-01-01

    Both G protein-coupled receptors (GPCRs) and receptor-tyrosine kinases (RTKs) regulate large signaling networks, control multiple cell functions and are implicated in many diseases including various cancers. Both of them are also the top therapeutic targets for disease treatment. The discovery of the cross-talk between GPCRs and RTKs connects these two vast signaling networks and complicates the already complicated signaling networks that regulate cell signaling and function. In this review, we focus on the transactivation of epidermal growth factor receptor (EGFR), a subfamily of RTKs, by GPCRs. Since the first report of EGFR transactivation by GPCR, significant progress has been made including the elucidation of the mechanisms underlying the transactivation. Here, we first provide a basic picture for GPCR, EGFR and EGFR transactivation by GPCR. We then discuss the progress made in the last five years and finally provided our view of the future challenge and future researches needed to overcome these challenges. PMID:26771606

  15. c-Jun transactivates Puma gene expression to promote osteoarthritis.

    PubMed

    Lu, Huading; Hou, Gang; Zhang, Yongkai; Dai, Yuhu; Zhao, Huiqing

    2014-05-01

    Osteoarthritis (OA) is a chronic degenerative joint disorder in which genetic, hormonal, mechanical and ageing factors affect its progression. Current studies are focusing on chondrocytes as a key mediator of OA at a cellular level. however, the mechanism underlying chondrocyte apoptosis remains unclear. PUMA is a pro-apoptotic member of the BH3-only subgroup of the Bcl-2 family and is involved in a large number of physiological and pathological processes. In the present study, we examined whether PUMA has a role in IL-1β-induced apoptosis and whether the c-Jun N-terminal kinase (JNK)/c-Jun pathway mediates the induction of PUMA, thus contributing to chondrocyte apoptosis. The results demonstrated an increase in PUMA protein and mRNA levels in cultured mouse chondrocytes following 4 h of IL-1β treatment. Furthermore, this upregulation of PUMA was critical for chondrocyte apoptosis as knockdown of PUMA using PUMA-specific siRNA significantly reduced apoptosis in cultured cells. Upon pharmacological inhibition of the JNK/c-Jun pathway with CE11004 or SP600125, the expression of PUMA was notably suppressed with a concomitant decrease in apoptosis observed in IL-1β-treated chondrocytes. Also, immunohistochemical studies revealed that the PUMA and c-Jun proteins were upregulated in chondrocytes from the articular cartilage of OA patients. Together, these data suggest a role for PUMA and the JNK/c-Jun pathway in the regulation of chondrocyte apoptosis during OA.

  16. HNF1beta/TCF2 mutations impair transactivation potential through altered co-regulator recruitment.

    PubMed

    Barbacci, Elena; Chalkiadaki, Angeliki; Masdeu, Christelle; Haumaitre, Cécile; Lokmane, Ludmilla; Loirat, Chantal; Cloarec, Sylvie; Talianidis, Iannis; Bellanne-Chantelot, Christine; Cereghini, Silvia

    2004-12-15

    Mutations in the HNF1beta gene, encoding the dimeric POU-homeodomain transcription factor HNF1beta (TCF2 or vHNF1), cause various phenotypes including maturity onset diabetes of the young 5 (MODY5), and abnormalities in kidney, pancreas and genital tract development. To gain insight into the molecular mechanisms underlying these phenotypes and into the structure of HNF1beta, we functionally characterized eight disease-causing mutations predicted to produce protein truncations, amino acids substitutions or frameshift deletions in different domains of the protein. Truncated mutations, retaining the dimerization domain, displayed defective nuclear localization and weak dominant-negative activity when co-expressed with the wild-type protein. A frameshift mutation located within the C-terminal QSP-rich domain partially reduced transcriptional activity, whereas selective deletion of this domain abolished transactivation. All five missense mutations, which concern POU-specific and homeodomain residues, were correctly expressed and localized to the nucleus. Although having different effects on DNA-binding capacity, which ranged from complete loss to a mild reduction, these mutations exhibited a severe reduction in their transactivation capacity. The transcriptional impairment of those mutants, whose DNA-binding activity was weakly or not affected, correlated with the loss of association with one of the histone-acetyltransferases CBP or PCAF. In contrast to wild-type HNF1beta, whose transactivation potential depends on the synergistic action of CBP and PCAF, the activity of these mutants was not increased by the synergistic action of these two coactivators or by treatment with the specific histone-deacetylase inhibitor TSA. Our findings suggest that the complex syndrome associated with HNF1beta-MODY5 mutations arise from either defective DNA-binding or transactivation function through impaired coactivator recruitment. PMID:15509593

  17. EPAS1 trans-activation during hypoxia requires p42/p44 MAPK.

    PubMed

    Conrad, P W; Freeman, T L; Beitner-Johnson, D; Millhorn, D E

    1999-11-19

    Hypoxia is a common environmental stress that regulates gene expression and cell function. A number of hypoxia-regulated transcription factors have been identified and have been shown to play critical roles in mediating cellular responses to hypoxia. One of these is the endothelial PAS-domain protein 1 (EPAS1/HIF2-alpha/HLF/HRF). This protein is 48% homologous to hypoxia-inducible factor 1-alpha (HIF1-alpha). To date, virtually nothing is known about the signaling pathways that lead to either EPAS1 or HIF1-alpha activation. Here we show that EPAS1 is phosphorylated when PC12 cells are exposed to hypoxia and that p42/p44 MAPK is a critical mediator of EPAS1 activation. Pretreatment of PC12 cells with the MEK inhibitor, PD98059, completely blocked hypoxia-induced trans-activation of a hypoxia response element (HRE) reporter gene by transfected EPAS1. Likewise, expression of a constitutively active MEK1 mimicked the effects of hypoxia on HRE reporter gene expression. However, pretreatment with PD98059 had no effect on EPAS1 phosphorylation during hypoxia, suggesting that MAPK targets other proteins that are critical for the trans-activation of EPAS1. We further show that hypoxia-induced trans-activation of EPAS1 is independent of Ras. Finally, pretreatment with calmodulin antagonists nearly completely blocked both the hypoxia-induced phosphorylation of MAPK and the EPAS1 trans-activation of HRE-Luc. These results demonstrate that the MAPK pathway is a critical mediator of EPAS1 activation and that activation of MAPK and EPAS1 occurs through a calmodulin-sensitive pathway and not through the GTPase, Ras. These results are the first to identify a specific signaling pathway involved in EPAS1 activation. PMID:10559262

  18. BRCA1 splice variants exhibit overlapping and distinct transcriptional transactivation activities.

    PubMed

    McEachern, Kristen A; Archey, William B; Douville, Karen; Arrick, Bradley A

    2003-05-01

    The global changes in gene expression induced by transient increased expression of full length BRCA1 as well as the spliced variant BRCA1(S) were evaluated by cDNA expression array in a human non-tumorigenic mammary epithelial cell line, MCF10A. Over 30 genes were identified that displayed an altered expression pattern in response to the expression of BRCA1 splice variants. The expression of NFkappaB inducing kinase was markedly down-regulated in BRCA1(L) transfected cells. However, a NFkappaB-responsive promoter construct yielded increased basal activity in BRCA1(L) transfected cells, as well as following treatment with tumor necrosis factor-alpha or lymphotoxin. In addition, nuclear extracts from BRCA1(L) transfected cells displayed increased DNA binding to the kappaB consensus site. The transcriptional activity of a panel of promoter constructs was evaluated following expression of wild type or mutant BRCA1. Full length BRCA1 transactivated the estrogen receptor-alpha (ERalpha) and BCL2 promoters as well as AP-1, SRE, and CRE containing promoters. Transactivation activity of the exon 11-deleted BRCA1(S) was more limited and usually of lower magnitude. The ability of a pathogenic mutation, 5382insC, to abrogate the transcriptional transactivation by BRCA1(L) and BRCA1(S) was also investigated. Mutant BRCA1 retained wild type levels of transcriptional activity for the ERalpha promoter as well as for the NFkappaB, AP-1, and CRE-responsive promoters but had reduced or no activity with the BCL2 and SRE promoters. These results show that BRCA1 isoforms have both overlapping and distinct transcriptional transactivation activity, and that a mutant form of BRCA1 implicated in carcinogenesis is not devoid of all activity.

  19. Identification of Essential Genetic Baculoviral Elements for Recombinant Protein Expression by Transactivation in Sf21 Insect Cells.

    PubMed

    Bleckmann, Maren; Schürig, Margitta; Chen, Fang-Fang; Yen, Zen-Zen; Lindemann, Nils; Meyer, Steffen; Spehr, Johannes; van den Heuvel, Joop

    2016-01-01

    The Baculovirus Expression Vector System (BEVS) is widely used to produce high amounts of recombinant proteins. Nevertheless, generating recombinant baculovirus in high quality is rather time-consuming and labor-intensive. Alternatively, virus-free expression in insect cells did not achieve similar expression levels for most proteins so far. The transactivation method is a promising approach for protein expression in Sf21 cells. It combines advantages of BEVS and plasmid-based expression by activating strong virus-dependent promoters on a transfected plasmid by baculoviral coinfection. Here, we identified expression elements required for transactivation. Therefore, we designed several vectors comprising different viral promoters or promoter combinations and tested them for eGFP expression using the automated BioLector microcultivation system. Remarkably, only the combination of the very late promoter p10 together with the homologous region 5 (hr5) could boost expression during transactivation. Other elements, like p10 alone or the late viral promoter polH, did not respond to transactivation. A new combination of hr5 and p10 with the strongest immediate early OpMNPV viral promoter OpIE2 improved the yield of eGFP by ~25% in comparison to the previous applied hr5-IE1-p10 expression cassette. Furthermore, we observed a strong influence of the transcription termination sequence and vector backbone on the level of expression. Finally, the expression levels for transactivation, BEVS and solely plasmid-based expression were compared for the marker protein eGFP, underlining the potential of transactivation for fast recombinant protein expression in Sf21 cells. In conclusion, essential elements for transactivation could be identified. The optimal elements were applied to generate an improved vector applicable in virus-free plasmid-based expression, transactivation and BEVS. PMID:26934632

  20. Identification of two distinct transactivation domains in the pluripotency sustaining factor nanog.

    PubMed

    Pan, Guang Jin; Pei, Duan Qing

    2003-12-01

    Nanog is a newly identified homeodomain gene that functions to sustain the pluripotency of embryonic stem cells. However, the molecular mechanism through which nanog regulates stem cell pluripotency remains unknown. Mouse nanog encodes a polypeptide of 305 residues with a divergent homeodomain similar to those in the NK-2 family. The rest of nanog contains no apparent homology to any known proteins characterized so far. It is hypothesized that nanog encodes a transcription factor that regulates stem cell pluripotency by switching on or off target genes. To test this hypothesis, we constructed fusion proteins between nanog and DNA binding domains of the yeast transcription factor Gal4 and tested the transactivation potentials of these constructs. Our data demonstrate that both regions N- and C- terminal to the homeodomain have transcription activities. Despite the fact that it contains no apparent transactivation motifs, the C-terminal domain is about 7 times as active as the N-terminal one. This unique arrangement of dual transactivators may confer nanog the flexibility and specificity to regulate downstream genes critical for both pluripotency and differentiation of stem cells.

  1. I-mfa domain proteins specifically interact with HTLV-1 Tax and repress its transactivating functions.

    PubMed

    Kusano, Shuichi; Yoshimitsu, Makoto; Hachiman, Miho; Ikeda, Masanori

    2015-12-01

    The I-mfa domain proteins HIC (also known as MDFIC) and I-mfa (also known as MDFI) are candidate tumor suppressor genes that are involved in cellular and viral transcriptional regulation. Here, we show that HIC and I-mfa directly interact with human T-cell leukemia virus type-1 (HTLV-1) Tax protein in vitro. In addition, HIC and I-mfa repress Tax-dependent transactivation of an HTLV-1 long terminal repeat (LTR) reporter construct in COS-1, Jurkat and high-Tax-producing HTLV-1-infected T cells. HIC also interacts with Tax through its I-mfa domain in vivo and represses Tax-dependent transactivation of HTLV-1 LTR and NF-κB reporter constructs in an interaction-dependent manner. Furthermore, we show that HIC decreases the nuclear distribution and stimulates the proteasomal degradation of Tax. These data reveal that HIC specifically interacts with HTLV-1 Tax and negatively regulates Tax transactivational activity by altering its subcellular distribution and stability.

  2. A human chromosome 12-associated 83-kilodalton cellular protein specifically binds to the loop region of human immunodeficiency virus type 1 trans-activation response element RNA.

    PubMed Central

    Hart, C E; Saltrelli, M J; Galphin, J C; Schochetman, G

    1995-01-01

    trans activation of human immunodeficiency virus type 1 (HIV-1) involves the viral trans-activator protein (Tat) and a cellular factor(s) encoded on human chromosome 12 (HuChr12) that targets the trans-activation response element (TAR) in the viral long terminal repeat. Because nascent TAR RNA is predicted to form a secondary structure that specifically binds cellular proteins, we investigated the composition of the TAR RNA-protein complex for HuChr12-specific proteins. UV cross-linking of TAR RNA-nuclear protein complexes formed in vitro identified an 83-kDa protein in human cells and in a human-hamster hybrid cell containing only HuChr12. The 83-kDa TAR RNA-binding protein was absent in the parental hamster cells. TAR RNA mutations that inhibited binding of the 83-kDa protein in vitro also inhibited HuChr12-dependent Tat trans activation. These TAR mutations changed the native sequence or secondary structure of the TAR loop. The TAR RNA binding activity of the 83-kDa protein also correlated with a HuChr12-dependent increase in steady-state HIV-1 RNA expression during Tat trans activation. Our results suggest that either a species-specific 83-kDa TAR RNA loop-binding protein is directly encoded on HuChr12 or a HuChr12 protein(s) induces the expression of an 83-kDa TAR-binding protein in nonprimate cells. PMID:7666565

  3. Cytokine signal transduction in P19 embryonal carcinoma cells: regulation of Stat3-mediated transactivation occurs independently of p21ras-Erk signaling.

    PubMed

    van Puijenbroek, A A; van der Saag, P T; Coffer, P J

    1999-09-15

    Ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) are members of a subfamily of related cytokines that share gp130 as common signal-transducing receptor component. CNTF has recently been demonstrated to induce increased survival and neuronal differentiation of P19 embryonal carcinoma (EC) cells; however, the molecular mechanisms underlying these effects are still elusive. Here we report that CNTF and LIF, but not interleukin-6, activated signal transducers and activators of transcription (STAT)-reporter constructs in P19 EC cells. Supershift analysis revealed that the STAT-element binding complex contained the transcription factor Stat3. Binding of Stat3 was inhibited by protein tyrosine kinase inhibitors, but not by the broad serine/threonine protein kinase inhibitor, H7. However, H7 inhibited CNTF-induced Stat3 transactivation. Using a dominant-negative p21ras construct and a specific inhibitor of mitogen-activated protein kinase kinase (MEK; PD098059) we demonstrated that CNTF-induced Stat3 transactivation was independent of the p21ras-mitogen-activated protein kinase (MAPK) pathway, while CNTF-induced MAPK activation was p21ras- and MEK-dependent. Taken together, our results demonstrate the activation of the p21ras-MAPK and STAT signal transduction pathways in response to CNTF and LIF in P19 EC cells and reveal that there is no modulating crosstalk between these pathways. Furthermore, our data suggest that CNTF- and LIF-induced Stat3 activation in P19 EC cells involves an H7-sensitive p21ras/MAPK- and Ca(2+)-independent kinase.

  4. Mycobacterium-Specific γ9δ2 T Cells Mediate Both Pathogen-Inhibitory and CD40 Ligand-Dependent Antigen Presentation Effects Important for Tuberculosis Immunity.

    PubMed

    Abate, Getahun; Spencer, Charles T; Hamzabegovic, Fahreta; Blazevic, Azra; Xia, Mei; Hoft, Daniel F

    2016-02-01

    Numerous pathogens, including Mycobacterium tuberculosis, can activate human γ9δ2 T cells to proliferate and express effector mechanisms. γ9δ2 T cells can directly inhibit the growth of intracellular mycobacteria and may also act as antigen-presenting cells (APC). Despite evidence for γδ T cells having the capacity to function as APC, the mechanisms involved and importance of these effects on overall tuberculosis (TB) immunity are unknown. We prepared M. tuberculosis-specific γ9δ2 T cell lines to study their direct protective effects and APC functions for M. tuberculosis-specific αβ T cells. The direct inhibitory effects on intracellular mycobacteria were measured, and the enhancing effects on proliferative and effector responses of αβ T cells assessed. Furthermore, the importance of cell-to-cell contact and soluble products for γ9δ2 T cell effector responses and APC functions were investigated. We demonstrate, in addition to direct inhibitory effects on intracellular mycobacteria, the following: (i) γ9δ2 T cells enhance the expansion of M. tuberculosis-specific αβ T cells and increase the ability of αβ T cells to inhibit intracellular mycobacteria; (ii) although soluble mediators are critical for the direct inhibitory effects of γ9δ2 T cells, their APC functions do not require soluble mediators; (iii) the APC functions of γ9δ2 T cells involve cell-to-cell contact that is dependent on CD40-CD40 ligand (CD40L) interactions; and (iv) fully activated CD4(+) αβ T cells and γ9δ2 T cells provide similar immune enhancing/APC functions for M. tuberculosis-specific T cells. These effector and helper effects of γ9δ2 T cells further indicate that these T cells should be considered important new targets for new TB vaccines.

  5. Kinetic analysis of internalization, recycling and redistribution of atrial natriuretic factor-receptor complex in cultured vascular smooth-muscle cells. Ligand-dependent receptor down-regulation.

    PubMed Central

    Pandey, K N

    1992-01-01

    The kinetics of internalization, sequestration and metabolic degradation of atrial natriuretic factor (ANF)-receptor complex were studied in rat thoracic aortic smooth-muscle (RTASM) cells. These parameters were directly determined by measuring 125I-ANF binding to total, intracellular and cell-surface receptors. Pretreatment of cells with the lysosomotropic agent chloroquine and the energy depleter dinitrophenol led to an increase in the intracellular 125I-ANF radioactivity. After 60 min incubation at 37 degrees C, cell-associated 125I-ANF radioactivity fell rapidly in chloroquine-treated cells (> 85%) compared with the controls (< 45%). 125I-ANF radioactivity increased to a peak of 65% of the initial level within 15 min in chloroquine-treated cells compared with only 22% in the control cells. During the initial incubation period at 37 degrees C, chloroquine inhibited the release of both intact and degraded 125I-ANF in a time-dependent manner. However, at later incubation times, the effect of chloroquine was diminished and release of both degraded and intact ligand was resumed. Extracellular unlabelled ANF did not affect the release of degraded 125I-ANF but it accelerated the release of intact ANF by a retroendocytotic mechanism. After the endocytosis, about 30-40% of ANF receptors were restored to the cell surface from the internalized pool of receptors. The restoration was blocked by chloroquine or dinitrophenol but not by cycloheximide. Exposure of RTASM cells to unlabelled ANF resulted in a time- and concentration-dependent loss of ANF receptors. Unlabelled ANF (10 nM) induced a loss of more than 52% of 125I-ANF binding, and a complete loss occurred at micromolar concentrations. It is inferred that ANF-induced down-regulation of its receptor resulted primarily from an increased rate in internalization and metabolic degradation of ligand-receptor complex by receptor-mediated endocytotic mechanisms. PMID:1445281

  6. Divergent Transactivation of Maize Storage Protein Zein Genes by the Transcription Factors Opaque2 and OHPs

    PubMed Central

    Yang, Jun; Ji, Chen; Wu, Yongrui

    2016-01-01

    Maize transcription factors (TFs) opaque2 (O2) and the O2 heterodimerizing proteins (OHP1 and OHP2) originated from an ancient segmental duplication. The 22-kDa (z1C) and 19-kDa (z1A, z1B, and z1D) α-zeins are the most abundant storage proteins in maize endosperm. O2 is known to regulate α-zein gene expression, but its target motifs in the 19-kDa α-zein gene promoters have not been identified. The mechanisms underlying the regulation of α-zein genes by these TFs are also not well understood. In this study, we found that the O2 binding motifs in the α-zein gene promoters are quite flexible, with ACGT being present in the z1C and z1A promoters and a variant, ACAT, being present in the z1B and z1D promoters. OHPs recognized and transactivated all of the α-zein promoters, although to much lower levels than did O2. In the presence of O2, the suppression of OHPs did not cause a significant reduction in the transcription of α-zein genes, but in the absence of O2, OHPs were critical for the expression of residual levels of α-zeins. These findings demonstrated that O2 is the primary TF and that OHPs function as minor TFs in this process. This relationship is the converse of that involved in 27-kDa γ-zein gene regulation, indicating that the specificities of O2 and the OHPs for regulating zein genes diverged after gene duplication. The prolamine-box binding factor by itself has limited transactivation activity, but it promotes the binding of O2 to O2 motifs, resulting in the synergistic transactivation of α-zein genes. PMID:27474726

  7. Identification of TRIML2, a Novel p53 Target, that Enhances p53-SUMOylation and Regulates the Transactivation of Pro-apoptotic Genes

    PubMed Central

    Kung, Che-Pei; Khaku, Sakina; Jennis, Matthew; Zhou, Yan; Murphy, Maureen E.

    2014-01-01

    The tumor suppressor protein p53, encoded by TP53, inhibits tumorigenesis by inducing cell cycle arrest, senescence and apoptosis. Several genetic polymorphisms exist in TP53, including a proline to arginine variant at amino acid 72 (P72 and R72, respectively); this polymorphism alters p53 function. In general, the P72 variant shows increased ability to induce cell cycle arrest, while the R72 variant possesses increased ability to induce apoptosis, relative to P72. At present, the underlying mechanisms for these functional differences are not fully understood. Toward elucidating the molecular basis for these differences a gene expression microarray analysis was conducted on normal human fibroblast cells that are homozygous for P72 and R72 variants, along with subclones of these lines that express a p53 short hairpin (shp53). Approximately three dozen genes were identified whose transactivation is affected by the codon 72 polymorphism. One of these is the tripartite motif family-like 2 (TRIML2) gene, which is preferentially induced by the R72 variant. Importantly, the accumulated data indicate that TRIML2 interacts with p53, and facilitates the modification of p53 with SUMO2. TRIML2 also enhances the ability of p53 to transactivate a subset of pro-apoptotic target genes associated with prolonged oxidative stress, including PIDD, PIG3 (TP53I3) and PIG6 (PRODH). These data indicate that TRIML2 is part of a feed-forward loop that activates p53 in cells expressing the R72 variant, particularly after prolonged stress. PMID:25256710

  8. Transactivation of the Receptor-tyrosine Kinase Ephrin Receptor A2 Is Required for the Low Molecular Weight Hyaluronan-mediated Angiogenesis That Is implicated in Tumor Progression*

    PubMed Central

    Lennon, Frances E; Mirzapoiazova, Tamara; Mambetsariev, Nurbek; Mambetsariev, Bolot; Salgia, Ravi; Singleton, Patrick A.

    2014-01-01

    Angiogenesis or the formation of new blood vessels is important in the growth and metastatic potential of various cancers. Therefore, understanding the mechanism(s) by which angiogenesis occurs can have important therapeutic implications in numerous malignancies. We and others have demonstrated that low molecular weight hyaluronan (LMW-HA, ∼2500 Da) promotes endothelial cell (EC) barrier disruption and angiogenesis. However, the mechanism(s) by which this occurs is poorly defined. Our data indicate that treatment of human EC with LMW-HA induced CD44v10 association with the receptor-tyrosine kinase, EphA2, transactivation (tyrosine phosphorylation) of EphA2, and recruitment of the PDZ domain scaffolding protein, PATJ, to the cell periphery. Silencing (siRNA) CD44, EphA2, PATJ, or Dbs (RhoGEF) expression blocked LMW-HA-mediated angiogenesis (EC proliferation, migration, and tubule formation). In addition, silencing EphA2, PATJ, Src, or Dbs expression blocked LMW-HA-mediated RhoA activation. To translate our in vitro findings, we utilized a novel anginex/liposomal targeting of murine angiogenic endothelium with either CD44 or EphA2 siRNA and observed inhibition of LMW-HA-induced angiogenesis in implanted Matrigel plugs. Taken together, these results indicate LMW-HA-mediated transactivation of EphA2 is required for PATJ and Dbs membrane recruitment and subsequent RhoA activation required for angiogenesis. These results suggest that targeting downstream effectors of LMW-HA could be a useful therapeutic intervention for angiogenesis-associated diseases including tumor progression. PMID:25023279

  9. Role of epidermal growth factor receptor transactivation in the activation of cytosolic phospholipase A(2) in leptin protection of salivary gland acinar cells against ethanol cytotoxicity.

    PubMed

    Slomiany, B L; Slomiany, A

    2009-06-01

    A pleiotropic hormone, leptin, secreted into saliva by the acinar cells of salivary glands is an important mediator of the processes of oral mucosal defense. Here, we report on the role of epidermal growth factor receptor (EGFR) transactivation in the signaling events that mediate leptin protection of sublingual salivary gland acinar cells against ethanol cytotoxicity. We show that the protective effect of leptin against ethanol cytotoxicity was associated with the increased EGFR protein tyrosine kinase and cytosolic phospholipase A(2) (cPLA(2)) activity, and characterized by a marked increase in matrix metalloproteinase MMP-9 and arachidonic acid (AA) release, and PGE(2) generation. The loss in countering capacity of leptin against ethanol cytotoxicity was attained with JAK inhibitor AG490, Src inhibitor PP2, and EGFR inhibitor AG1478, as well as ERK inhibitor PD98059. Moreover, the agents evoked also the inhibition in leptin-induced up-regulation in cPLA(2) activity, AA release, and PGE(2) generation. The changes caused by leptin in EGFR phosphorylation, MMP-9, and cPLA(2) activation were susceptible to suppression by metalloprotease inhibitor GM6001, but the production of MMP-9 was not affected by EGFR inhibitor AG1478 or PKC inhibitor Ro318220. These findings point to the involvement of MMP-9 in the event of leptin-induced EGFR transactivation that results in the signaling cascade leading to cPLA(2) activation and up-regulation in PGE(2) generation, thus providing new insights into the mechanism of oral mucosal protection against ethanol toxicity.

  10. NF-kappaB p65-Dependent Transactivation of miRNA Genes following Cryptosporidium parvum Infection Stimulates Epithelial Cell Immune Responses

    PubMed Central

    Liu, Jun; Gong, Ai-Yu; Drescher, Kristen M.; Chen, Xian-Ming

    2009-01-01

    Cryptosporidium parvum is a protozoan parasite that infects the gastrointestinal epithelium and causes diarrheal disease worldwide. Innate epithelial immune responses are key mediators of the host's defense to C. parvum. MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional level and are involved in regulation of both innate and adaptive immune responses. Using an in vitro model of human cryptosporidiosis, we analyzed C. parvum-induced miRNA expression in biliary epithelial cells (i.e., cholangiocytes). Our results demonstrated differential alterations in the mature miRNA expression profile in cholangiocytes following C. parvum infection or lipopolysaccharide stimulation. Database analysis of C. parvum-upregulated miRNAs revealed potential NF-κB binding sites in the promoter elements of a subset of miRNA genes. We demonstrated that mir-125b-1, mir-21, mir-30b, and mir-23b-27b-24-1 cluster genes were transactivated through promoter binding of the NF-κB p65 subunit following C. parvum infection. In contrast, C. parvum transactivated mir-30c and mir-16 genes in cholangiocytes in a p65-independent manner. Importantly, functional inhibition of selected p65-dependent miRNAs in cholangiocytes increased C. parvum burden. Thus, we have identified a panel of miRNAs regulated through promoter binding of the NF-κB p65 subunit in human cholangiocytes in response to C. parvum infection, a process that may be relevant to the regulation of epithelial anti-microbial defense in general. PMID:19997496

  11. NF-kappaB p65-dependent transactivation of miRNA genes following Cryptosporidium parvum infection stimulates epithelial cell immune responses.

    PubMed

    Zhou, Rui; Hu, Guoku; Liu, Jun; Gong, Ai-Yu; Drescher, Kristen M; Chen, Xian-Ming

    2009-12-01

    Cryptosporidium parvum is a protozoan parasite that infects the gastrointestinal epithelium and causes diarrheal disease worldwide. Innate epithelial immune responses are key mediators of the host's defense to C. parvum. MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional level and are involved in regulation of both innate and adaptive immune responses. Using an in vitro model of human cryptosporidiosis, we analyzed C. parvum-induced miRNA expression in biliary epithelial cells (i.e., cholangiocytes). Our results demonstrated differential alterations in the mature miRNA expression profile in cholangiocytes following C. parvum infection or lipopolysaccharide stimulation. Database analysis of C. parvum-upregulated miRNAs revealed potential NF-kappaB binding sites in the promoter elements of a subset of miRNA genes. We demonstrated that mir-125b-1, mir-21, mir-30b, and mir-23b-27b-24-1 cluster genes were transactivated through promoter binding of the NF-kappaB p65 subunit following C. parvum infection. In contrast, C. parvum transactivated mir-30c and mir-16 genes in cholangiocytes in a p65-independent manner. Importantly, functional inhibition of selected p65-dependent miRNAs in cholangiocytes increased C. parvum burden. Thus, we have identified a panel of miRNAs regulated through promoter binding of the NF-kappaB p65 subunit in human cholangiocytes in response to C. parvum infection, a process that may be relevant to the regulation of epithelial anti-microbial defense in general.

  12. Multiple Mechanisms are Responsible for Transactivation of the Epidermal Growth Factor Receptor in Mammary Epithelial Cells

    SciTech Connect

    Rodland, Karin D.; Bollinger, Nikki; Ippolito, Danielle L.; Opresko, Lee; Coffey, Robert J.; Zangar, Richard C.; Wiley, H. S.

    2008-11-14

    REVIEW ENTIRE DOCUMENT AT: https://pnlweb.pnl.gov/projects/bsd/ERICA%20Manuscripts%20for%20Review/KD%20Rodland%20D7E80/HMEC_transactivation_ms01_15+Figs.pdf ABSTRACT: Using a single nontransformed strain of human mammary epithelial cells, we found that the ability of multiple growth factors and cytokines to induce ERK phosphorylation was dependent on EGFR activity. These included lysophosphatidic acid (LPA), uridine triphosphate, growth hormone, vascular endothelial growth factor, insulin-like growth factor-1 (IGF-1), and tumor necrosis factoralpha. In contrast, hepatocyte growth factor could stimulate ERK phosphorylation independent of EGFR activity...

  13. 5-HT(1A) receptors transactivate the platelet-derived growth factor receptor type beta in neuronal cells.

    PubMed

    Kruk, Jeff S; Vasefi, Maryam S; Liu, Hui; Heikkila, John J; Beazely, Michael A

    2013-01-01

    In the absence of ligand, certain growth factor receptors can be activated via G-protein coupled receptor (GPCR) activation in a process termed transactivation. Serotonin (5-HT) receptors can transactivate platelet-derived growth factor (PDGF) β receptors in smooth muscle cells, but it is not known if similar pathways occur in neuronal cells. Here we show that 5-HT can transiently increase the phosphorylation of PDGFβ receptors through 5-HT(1A) receptors in a time- and dose-dependent manner in SH-SY5Y neuroblastoma cells. 5-HT also transactivates PDGFβ receptors in primary cortical neurons. This transactivation pathway is pertussis-toxin sensitive and Src tyrosine kinase-dependent. This pathway is also dependent on phospholipase C activity and intracellular calcium signaling. Several studies involving PDGFβ receptor transactivation by GPCRs have also demonstrated a PDGFβ receptor-dependent increase in the phosphorylation of ERK1/2. Yet in SH-SY5Y cells, 5-HT treatment causes a PDGFβ receptor-independent increase in ERK1/2 phosphorylation. This crosstalk between 5-HT and PDGFβ receptors identifies a potentially important signaling link between the serotonergic system and growth factor signaling in neurons. PMID:23006663

  14. Piroxicam and c-phycocyanin prevent colon carcinogenesis by inhibition of membrane fluidity and canonical Wnt/β-catenin signaling while up-regulating ligand dependent transcription factor PPARγ.

    PubMed

    Saini, Manpreet Kaur; Sanyal, Sankar Nath

    2014-06-01

    The colon cancer tissues from DMH treated rats exhibited higher membrane potential, fluidity and changed lipid order as examined by Merocyanine 540 and 1,6-diphenyl-1,3,5-hexatriene, respectively. A transition from gel to liquid crystalline state was observed by Laurdan fluorescence and also reduced fluorescence quenching of NBD-PE as contributed in the decreased membrane lipid phase separation. With piroxicam, a traditional NSAID and c-phycocyanin, a biliprotein from Spirulina platensis, these effects were normalized. An augmented intracellular Ca(+2) had contributed to the drug mediated apoptosis which is supported by an elevated calpain-9 expression. Histopathologically, a large pool of secreted acid/neutral mucopolysaccrides as well as the presence of blood vessels and dysplastic crypts signifies invasive mucinous adenocarcinoma while both the drugs reduced these neoplastic alterations. Wnt/β-catenin pathway was also found to be up-regulated which served as a crucial indicator for cancer cell growth. A concomitant down regulation of PPARγ was noted in DMH treatment which is associated with tumor progression. The expression of PPARα and δ, the other two isoforms of PPAR family was also modulated. We conclude that piroxicam and c-phycocyanin exert their anti-neoplastic effects via regulating membrane properties, raising calpain-9 and PPARγ expression while suppressing Wnt/β-catenin signaling in experimental colon carcinogenesis. PMID:24721324

  15. A versatile cis-blocking and trans-activation strategy for ribozyme characterization

    PubMed Central

    Kennedy, Andrew B.; Liang, Joe C.; Smolke, Christina D.

    2013-01-01

    Synthetic RNA control devices that use ribozymes as gene-regulatory components have been applied to controlling cellular behaviors in response to environmental signals. Quantitative measurement of the in vitro cleavage rate constants associated with ribozyme-based devices is essential for advancing the molecular design and optimization of this class of gene-regulatory devices. One of the key challenges encountered in ribozyme characterization is the efficient generation of full-length RNA from in vitro transcription reactions, where conditions generally lead to significant ribozyme cleavage. Current methods for generating full-length ribozyme-encoding RNA rely on a trans-blocking strategy, which requires a laborious gel separation and extraction step. Here, we develop a simple two-step gel-free process including cis-blocking and trans-activation steps to support scalable generation of functional full-length ribozyme-encoding RNA. We demonstrate our strategy on various types of natural ribozymes and synthetic ribozyme devices, and the cleavage rate constants obtained for the RNA generated from our strategy are comparable with those generated through traditional methods. We further develop a rapid, label-free ribozyme cleavage assay based on surface plasmon resonance, which allows continuous, real-time monitoring of ribozyme cleavage. The surface plasmon resonance-based characterization assay will complement the versatile cis-blocking and trans-activation strategy to broadly advance our ability to characterize and engineer ribozyme-based devices. PMID:23155065

  16. NLRC5/MHC class I transactivator is a target for immune evasion in cancer.

    PubMed

    Yoshihama, Sayuri; Roszik, Jason; Downs, Isaac; Meissner, Torsten B; Vijayan, Saptha; Chapuy, Bjoern; Sidiq, Tabasum; Shipp, Margaret A; Lizee, Gregory A; Kobayashi, Koichi S

    2016-05-24

    Cancer cells develop under immune surveillance, thus necessitating immune escape for successful growth. Loss of MHC class I expression provides a key immune evasion strategy in many cancers, although the molecular mechanisms remain elusive. MHC class I transactivator (CITA), known as "NLRC5" [NOD-like receptor (NLR) family, caspase recruitment (CARD) domain containing 5], has recently been identified as a critical transcriptional coactivator of MHC class I gene expression. Here we show that the MHC class I transactivation pathway mediated by CITA/NLRC5 constitutes a target for cancer immune evasion. In all the 21 tumor types we examined, NLRC5 expression was highly correlated with the expression of MHC class I, with cytotoxic T-cell markers, and with genes in the MHC class I antigen-presentation pathway, including LMP2/LMP7, TAP1, and β2-microglobulin. Epigenetic and genetic alterations in cancers, including promoter methylation, copy number loss, and somatic mutations, were most prevalent in NLRC5 among all MHC class I-related genes and were associated with the impaired expression of components of the MHC class I pathway. Strikingly, NLRC5 expression was significantly associated with the activation of CD8(+) cytotoxic T cells and patient survival in multiple cancer types. Thus, NLRC5 constitutes a novel prognostic biomarker and potential therapeutic target of cancers. PMID:27162338

  17. Enhancement of alkaloid production in opium and California poppy by transactivation using heterologous regulatory factors.

    PubMed

    Apuya, Nestor R; Park, Joon-Hyun; Zhang, Liping; Ahyow, Maurice; Davidow, Patricia; Van Fleet, Jennifer; Rarang, Joel C; Hippley, Matthew; Johnson, Thomas W; Yoo, Hye-Dong; Trieu, Anthony; Krueger, Shannon; Wu, Chuan-yin; Lu, Yu-ping; Flavell, Richard B; Bobzin, Steven C

    2008-02-01

    Genes encoding regulatory factors isolated from Arabidopsis, soybean and corn have been screened to identify those that modulate the expression of genes encoding for enzymes involved in the biosynthesis of morphinan alkaloids in opium poppy (Papaver somniferum) and benzophenanthridine alkaloids in California poppy (Eschscholzia californica). In opium poppy, the over-expression of selected regulatory factors increased the levels of PsCOR (codeinone reductase), Ps4'OMT (S-adenosyl-l-methionine:3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase) and Ps6OMT [(R,S)-norcoclaurine 6-O-methyltransferase] transcripts by 10- to more than 100-fold. These transcriptional activations translated into an enhancement of alkaloid production in opium poppy of up to at least 10-fold. In California poppy, the transactivation effect of regulatory factor WRKY1 resulted in an increase of up to 60-fold in the level of EcCYP80B1 [(S)-N-methylcoclaurine 3'-hydroxylase] and EcBBE (berberine bridge enzyme) transcripts. As a result, the accumulations of selected alkaloid intermediates were enhanced up to 30-fold. The transactivation effects of other regulatory factors led to the accumulation of the same intermediates. These regulatory factors also led to the production of new alkaloids in California poppy callus culture.

  18. Enhancement of alkaloid production in opium and California poppy by transactivation using heterologous regulatory factors.

    PubMed

    Apuya, Nestor R; Park, Joon-Hyun; Zhang, Liping; Ahyow, Maurice; Davidow, Patricia; Van Fleet, Jennifer; Rarang, Joel C; Hippley, Matthew; Johnson, Thomas W; Yoo, Hye-Dong; Trieu, Anthony; Krueger, Shannon; Wu, Chuan-yin; Lu, Yu-ping; Flavell, Richard B; Bobzin, Steven C

    2008-02-01

    Genes encoding regulatory factors isolated from Arabidopsis, soybean and corn have been screened to identify those that modulate the expression of genes encoding for enzymes involved in the biosynthesis of morphinan alkaloids in opium poppy (Papaver somniferum) and benzophenanthridine alkaloids in California poppy (Eschscholzia californica). In opium poppy, the over-expression of selected regulatory factors increased the levels of PsCOR (codeinone reductase), Ps4'OMT (S-adenosyl-l-methionine:3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase) and Ps6OMT [(R,S)-norcoclaurine 6-O-methyltransferase] transcripts by 10- to more than 100-fold. These transcriptional activations translated into an enhancement of alkaloid production in opium poppy of up to at least 10-fold. In California poppy, the transactivation effect of regulatory factor WRKY1 resulted in an increase of up to 60-fold in the level of EcCYP80B1 [(S)-N-methylcoclaurine 3'-hydroxylase] and EcBBE (berberine bridge enzyme) transcripts. As a result, the accumulations of selected alkaloid intermediates were enhanced up to 30-fold. The transactivation effects of other regulatory factors led to the accumulation of the same intermediates. These regulatory factors also led to the production of new alkaloids in California poppy callus culture. PMID:17961129

  19. NLRC5 exclusively transactivates MHC class I and related genes through a distinctive SXY module.

    PubMed

    Ludigs, Kristina; Seguín-Estévez, Queralt; Lemeille, Sylvain; Ferrero, Isabel; Rota, Giorgia; Chelbi, Sonia; Mattmann, Chantal; MacDonald, H Robson; Reith, Walter; Guarda, Greta

    2015-03-01

    MHC class II (MHCII) genes are transactivated by the NOD-like receptor (NLR) family member CIITA, which is recruited to SXY enhancers of MHCII promoters via a DNA-binding "enhanceosome" complex. NLRC5, another NLR protein, was recently found to control transcription of MHC class I (MHCI) genes. However, detailed understanding of NLRC5's target gene specificity and mechanism of action remained lacking. We performed ChIP-sequencing experiments to gain comprehensive information on NLRC5-regulated genes. In addition to classical MHCI genes, we exclusively identified novel targets encoding non-classical MHCI molecules having important functions in immunity and tolerance. ChIP-sequencing performed with Rfx5(-/-) cells, which lack the pivotal enhanceosome factor RFX5, demonstrated its strict requirement for NLRC5 recruitment. Accordingly, Rfx5-knockout mice phenocopy Nlrc5 deficiency with respect to defective MHCI expression. Analysis of B cell lines lacking RFX5, RFXAP, or RFXANK further corroborated the importance of the enhanceosome for MHCI expression. Although recruited by common DNA-binding factors, CIITA and NLRC5 exhibit non-redundant functions, shown here using double-deficient Nlrc5(-/-)CIIta(-/-) mice. These paradoxical findings were resolved by using a "de novo" motif-discovery approach showing that the SXY consensus sequence occupied by NLRC5 in vivo diverges significantly from that occupied by CIITA. These sequence differences were sufficient to determine preferential occupation and transactivation by NLRC5 or CIITA, respectively, and the S box was found to be the essential feature conferring NLRC5 specificity. These results broaden our knowledge on the transcriptional activities of NLRC5 and CIITA, revealing their dependence on shared enhanceosome factors but their recruitment to distinct enhancer motifs in vivo. Furthermore, we demonstrated selectivity of NLRC5 for genes encoding MHCI or related proteins, rendering it an attractive target for therapeutic

  20. Inhibition of HIV-1 reactivation by a telomerase-derived peptide in a HSP90-dependent manner

    PubMed Central

    Kim, Hong; Choi, Myung-Soo; Inn, Kyung-Soo; Kim, Bum-Joon

    2016-01-01

    A peptide vaccine designed to induce T-cell immunity to telomerase, GV1001, has been shown to modulate cellular signaling pathways and confer a direct anti-cancer effect through the interaction with heat shock protein (HSP) 90 and 70. Here, we have found that GV1001 can modulate transactivation protein-mediated human immunodeficiency virus (HIV)-1 transactivation in an HSP90-dependent manner. GV1001 treatment resulted in significant suppression of HIV-1 replication and rescue of infected cells from death by HIV-1. Transactivation of HIV-long terminal repeat (LTR) was inhibited by GV1001, indicating that GV1001 suppressed the transcription from proviral HIV DNA. The anti-HIV-1 activity of GV1001 was completely abrogated by an HSP90-neutralizing antibody, indicating that the antiviral activity depends on HSP90. Further mechanistic studies revealed that GV1001 suppresses basal NF-κB activation, which is required for HIV-1 LTR transactivation in an HSP90-dependent manner. Inhibition of LTR transactivation by GV1001 suggests its potential to suppress HIV-1 reactivation from latency. Indeed, PMA-mediated reactivation of HIV-1 from latent infected cells was suppressed by GV1001. The results suggest the potential therapeutic use of GV1001, a peptide proven to be safe for human use, as an anti-HIV-1 agent to suppress the reactivation from latently infected cells. PMID:27363520

  1. The dorsal-related immunity factor, Dif, is a sequence-specific trans-activator of Drosophila Cecropin gene expression.

    PubMed Central

    Petersen, U M; Björklund, G; Ip, Y T; Engström, Y

    1995-01-01

    A new member of the Rel family of transcription factors, the dorsal-related immunity factor, Dif, was recently cloned and suggested to be involved in regulating the immune response in Drosophila. Despite its classification as a Rel family member, the Dif cDNA-encoded product has not been proven previously to be a transcription factor. We now present evidence that the Dif gene product trans-activates the Drosophila Cecropin A1 gene in co-transfection assays. The transactivation requires a 40 bp upstream element including an insect kappa B-like motif. A dimer of the kappa B-like motif 5'-GGGGATTTTT inserted into a minimal promoter conferred high levels of reporter gene expression by Dif, while a multimer of several mutated versions of this motif was not activated, demonstrating the sequence specificity of Dif. Full trans-activation by Dif requires the C-terminal part of the protein. The morphogen dorsal (dl) can also activate the Cecropin A1 promoter, but to a lesser extent and in a less sequence-specific manner than Dif. Simultaneous overexpression of Dif and dl in co-transfection assays revealed that dl possesses a dominant negative effect on Dif transactivation. This study establishes that Dif is a sequence-specific transcription factor and is probably a key activator of the immune response in Drosophila. Images PMID:7621828

  2. Mutational analysis of the human immunodeficiency virus type 1 Rev transactivator: essential residues near the amino terminus.

    PubMed Central

    Hope, T J; McDonald, D; Huang, X J; Low, J; Parslow, T G

    1990-01-01

    The expression of certain mRNAs from human immunodeficiency virus type 1 (HIV-1) is controlled by the viral transactivator Rev, a nucleolar protein that binds a cis-acting element in these mRNAs. Rev is encoded by two viral exons that specify amino acids 1 to 26 and 27 to 116, respectively. Earlier studies have mapped essential regions of the protein that are encoded in the second exon. By further mutational analysis of Rev, we have now identified a novel locus encoded by the first exon that also is essential for transactivation in vivo. Defined by mutations at residues 14 to 20, this locus coincides with a cluster of positively charged and nonpolar amino acids that is conserved in Rev proteins of all known primate immunodeficiency viruses. Rev proteins that contained mutations at this site were defective in both nuclear localization and transactivation and did not function as trans-dominant inhibitors of wild-type Rev. Fusion of these mutants to a heterologous nuclear protein complemented the defect in localization but did not restore biological activity. Our findings suggest that this N-terminal locus may play a direct role in transactivation, perhaps contributing to essential protein-protein interactions or forming part of the RNA-binding domain of Rev. Images PMID:2120472

  3. Interactions of thyroid hormone receptor with the human immunodeficiency virus type 1 (HIV-1) long terminal repeat and the HIV-1 Tat transactivator.

    PubMed Central

    Desai-Yajnik, V; Hadzic, E; Modlinger, P; Malhotra, S; Gechlik, G; Samuels, H H

    1995-01-01

    Thyroid hormone (T3) receptor (T3R) regulates the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) by binding to and activating thyroid hormone response elements (TREs) embedded within the viral NF-kappa B and Sp1 motifs. The TREs within the NF-kappa B sites are necessary for activation by T3 in the absence of Tat, while those in the Sp1 motifs function as TREs only when Tat is expressed, suggesting that Tat and T3R interact in the cell. Transactivation of the HIV-1 LTR by T3R alpha and several receptor mutants revealed that the 50-amino-acid N-terminal A/B region of T3R alpha, known to interact with the basal transcription factor TFIIB, is critical for activation of both Tat-dependent and Tat-independent responsive sequences of the LTR. A single amino acid change in the highly conserved tau 1 region in the ligand-binding domain of T3R alpha eliminates Tat-independent but not Tat-dependent activation of the HIV-1 LTR by T3. Ro 5-3335 [7-chloro-5-(2-pyrryl)-3H-1,4-benzodiazepin-2(H)-one], which inhibits Tat-mediated transactivation of HIV-1, also inhibits the functional interaction between Tat and T3R alpha. Binding studies with glutathione-S-transferase fusion proteins and Western (immunoblot) analysis indicate that T3R alpha interacts with Tat through amino acids within the DNA-binding domain of T3R alpha. Mutational analysis revealed that amino acid residues in the basic and C-terminal regions of Tat are required for the binding of Tat to T3R alpha, while the N terminus of Tat is not required. These studies provide functional and physical evidence that stimulation of the HIV-1 LTR by T3 involves an interaction between T3R alpha and Tat. Our results also suggest a model in which multiple domains of T3R alpha interact with Tat and other factors to form transcriptionally important complexes. PMID:7609079

  4. ARA67/PAT1 Functions as a Repressor To Suppress Androgen Receptor Transactivation

    PubMed Central

    Zhang, Yanqing; Yang, Yue; Yeh, Shuyuan; Chang, Chawnshang

    2004-01-01

    The androgen receptor (AR) may recruit multiple coregulators for proper or optimal transactivation. Here we report the identification and characterization of ARA67/PAT1 as an AR coregulator from a prostate cDNA library. ARA67/PAT1 was screened out as an AR N terminus interacting protein. Interaction mapping shows that the cooperation of multiple domains within ARA67/PAT1 may be required for the maximal interaction with AR. ARA67/PAT1 functions as a repressor with better suppressive effects on AR compared to glucocorticoid receptor and estrogen receptor. Further mechanism dissection reveals that the interrupted AR cytoplasmic-nuclear shuttling may play a major role in ARA67/PAT1 mediated suppression on AR. Together, these results suggest that ARA67/PAT1 may function as a novel repressor that can modulate AR function in prostate cancer. PMID:14729952

  5. Histone acetyltransferase p300 promotes MKL1-mediated transactivation of catechol-O-methyltransferase gene.

    PubMed

    Liu, Zhipeng; Luo, Xuegang; Liu, Lei; Zhao, Wenwen; Guo, Shu; Guo, Yu; Wang, Nan; He, Hongpeng; Liao, Xinghua; Ma, Wenjian; Zhou, Hao; Zhang, Tongcun

    2013-12-01

    Previous studies have revealed that histone acetyltransferase p300 is recruited to the promoters of certain cardiac and smooth muscle specific genes to enhance the transactivation activity of myocardin, which is a master regulator in cardiovascular differentiation and development. Here, we found that the gene encoding catechol-O-methyltransferase (COMT), an important metabolic enzyme catalyzing the conversion of estrogen, is also a target gene of myocardin-related transcription factors (MRTFs). Megakaryoblastic leukemia 1 (MKL1, also named MRTF-A) and p300 could synergistically augment the expression of COMT gene, increase the metabolic rate of estrogen, and thus reduce the proliferation of MCF-7 breast cancer cells stimulated by estrogen. PMID:24096006

  6. Enhancement of gene transactivation activity of androgen receptor by hepatitis B virus X protein

    SciTech Connect

    Zheng Yanyan; Chen Wenling; Ma, W.-L. Maverick; Chang Chawnshang; Ou, J.-H. James . E-mail: jamesou@hsc.usc.edu

    2007-07-05

    Hepatitis B virus (HBV) X protein (HBx) is a regulatory protein that is required for efficient replication of HBV in its natural host. In this report, we demonstrate by co-immunoprecipitation experiments that HBx can physically bind to the androgen receptor (AR), which is a nuclear hormone receptor that is expressed in many different tissues including the liver. This observation is further supported by confocal microscopy, which reveals that HBx can alter the subcellular localization of the AR both in the presence and in the absence of dihydrotestosterone (DHT). Further studies indicate that HBx can enhance the gene transactivation activity of AR by enhancing its DNA binding activity in a DHT-dependent manner. However, HBx does not remain associated with AR on the DNA. As AR can regulate the expression of a number of cellular genes, our results raise the possibility that HBV pathogenesis may be mediated in part via the interaction between HBx and AR.

  7. Phosphorylation of RAF Kinase Dimers Drives Conformational Changes that Facilitate Transactivation.

    PubMed

    Jambrina, Pablo G; Rauch, Nora; Pilkington, Ruth; Rybakova, Katja; Nguyen, Lan K; Kholodenko, Boris N; Buchete, Nicolae-Viorel; Kolch, Walter; Rosta, Edina

    2016-01-18

    RAF kinases are key players in the MAPK signaling pathway and are important targets for personalized cancer therapy. RAF dimerization is part of the physiological activation mechanism, together with phosphorylation, and is known to convey resistance to RAF inhibitors. Herein, molecular dynamics simulations are used to show that phosphorylation of a key N-terminal acidic (NtA) motif facilitates RAF dimerization by introducing several interprotomer salt bridges between the αC-helix and charged residues upstream of the NtA motif. Additionally, we show that the R-spine of RAF interacts with a conserved Trp residue in the vicinity of the NtA motif, connecting the active sites of two protomers and thereby modulating the cooperative interactions in the RAF dimer. Our findings provide a first structure-based mechanism for the auto-transactivation of RAF and could be generally applicable to other kinases, opening new pathways for overcoming dimerization-related drug resistance.

  8. Functional interaction of the bovine papillomavirus E2 transactivation domain with TFIIB.

    PubMed

    Yao, J M; Breiding, D E; Androphy, E J

    1998-02-01

    Induction of gene expression by the papillomavirus E2 protein requires its approximately 220-amino-acid amino-terminal transactivation domain (TAD) to interact with cellular factors that lead to formation of an activated RNA polymerase complex. These interaction partners have yet to be identified and characterized. The E2 protein localizes the transcription complex to the target promoter through its carboxy-terminal sequence-specific DNA binding domain. This domain has been reported to bind the basal transcription factors TATA-binding protein and TFIIB. We present evidence establishing a direct interaction between amino acids 74 to 134 of the E2 TAD and TFIIB. Within this region, the E2 point mutant N127Y was partially defective and W99C was completely defective for TFIIB binding in vitro, and these mutants displayed reduced or no transcriptional activity, respectively, upon transfection into C33A cells. Overexpression of TFIIB specifically restored transactivation by N127Y to close to wild-type levels, while W99C remained inactive. To further demonstrate the functional interaction of TFIIB with the wild-type E2 TAD, this region was fused to a bacterial DNA binding domain (LexA:E2:1-216). Upon transfection with increasing amounts of LexA:E2:1-216, there was reduction of its transcriptional activity, a phenomenon thought to result from titration of limiting factors, or squelching. Squelching of LexA:E2:1-216, or the wild-type E2 activator, was partially relieved by overexpression of TFIIB. We conclude that a specific region of the E2 TAD functionally interacts with TFIIB.

  9. Identification of transcriptional regulatory nodes in soybean defense networks using transient co-transactivation assays

    PubMed Central

    Wang, Yongli; Wang, Hui; Ma, Yujie; Du, Haiping; Yang, Qing; Yu, Deyue

    2015-01-01

    Plant responses to major environmental stressors, such as insect feeding, not only occur via the functions of defense genes but also involve a series of regulatory factors. Our previous transcriptome studies proposed that, in addition to two defense-related genes, GmVSPβ and GmN:IFR, a high proportion of transcription factors (TFs) participate in the incompatible soybean-common cutworm interaction networks. However, the regulatory mechanisms and effects of these TFs on those induced defense-related genes remain unknown. In the present work, we isolated and identified 12 genes encoding MYB, WRKY, NAC, bZIP, and DREB TFs from a common cutworm-induced cDNA library of a resistant soybean line. Sequence analysis of the promoters of three co-expressed genes, including GmVSPα, GmVSPβ, and GmN:IFR, revealed the enrichment of various TF-binding sites for defense and stress responses. To further identify the regulatory nodes composed of these TFs and defense gene promoters, we performed extensive transient co-transactivation assays to directly test the transcriptional activity of the 12 TFs binding at different levels to the three co-expressed gene promoters. The results showed that all 12 TFs were able to transactivate the GmVSPβ and GmN:IFR promoters. GmbZIP110 and GmMYB75 functioned as distinct regulators of GmVSPα/β and GmN:IFR expression, respectively, while GmWRKY39 acted as a common central regulator of GmVSPα/β and GmN:IFR expression. These corresponding TFs play crucial roles in coordinated plant defense regulation, which provides valuable information for understanding the molecular mechanisms involved in insect-induced transcriptional regulation in soybean. More importantly, the identified TFs and suitable promoters can be used to engineer insect-resistant plants in molecular breeding studies. PMID:26579162

  10. Hypo- and Hypermorphic FOXC1 Mutations in Dominant Glaucoma: Transactivation and Phenotypic Variability

    PubMed Central

    Medina-Trillo, Cristina; Sánchez-Sánchez, Francisco; Aroca-Aguilar, José-Daniel; Ferre-Fernández, Jesús-José; Morales, Laura; Méndez-Hernández, Carmen-Dora; Blanco-Kelly, Fiona; Ayuso, Carmen; García-Feijoo, Julián; Escribano, Julio

    2015-01-01

    Dominant glaucoma, a heterogeneous, infrequent and irreversible optic neuropathy, is often associated with elevated intraocular pressure and early-onset. The role of FOXC1 in this type of glaucoma was investigated in twelve Spanish probands via nucleotide variation screening of its proximal promoter and unique exon. Functional evaluations of the identified variants included analyses of the transcriptional activity, protein stability, DNA binding ability and subcellular localization. Four different mutations that were identified in four probands (33.3%) were associated with remarkable phenotypic variability and were functionally classified as either hypermorphic (p.Y47X, p.Q106X and p.G447_G448insDG) or hypomorphic (p.I126S) alleles. To the best of our knowledge, three of the variants are novel (p.Y47X, p.I126S and p.G447_G448insDG) and, in addition, hypermorphic FOXC1 mutations are reported herein for the first time. The presence of an intact N-terminal activation domain in the truncated proteins p.Y47X and p.Q106X may underlie their associated transactivation hyperactivity by a gain-of-function mechanism involving dysregulated protein-protein interactions. Similarly, altered molecular interactions may also lead to increased p.G447_G448insDG activity. In contrast, the partial loss-of-function associated with p.I126S was due to impaired protein stability, DNA binding, protein phosphorylation and subcellular distribution. These results support that moderate and variable FOXC1 transactivation changes are associated with moderate goniodysgenesis, dominant glaucoma and remarkable phenotypic variability. PMID:25786029

  11. Comparison of the transactivation domains of Stat5 and Stat6 in lymphoid cells and mammary epithelial cells.

    PubMed Central

    Moriggl, R; Berchtold, S; Friedrich, K; Standke, G J; Kammer, W; Heim, M; Wissler, M; Stöcklin, E; Gouilleux, F; Groner, B

    1997-01-01

    Stat (signal transducers and activators of transcription) and Jak (Janus kinases) proteins are central components in the signal transduction events in hematopoietic and epithelial cells. They are rapidly activated by various cytokines, hormones, and growth factors. Upon ligand binding and cytokine receptor dimerization, Stat proteins are phosphorylated on tyrosine residues by Jak kinases. Activated Stat proteins form homo- or heterodimers, translocate to the nucleus, and induce transcription from responsive genes. Stat5 and Stat6 are transcription factors active in mammary epithelial cells and immune cells. Prolactin activates Stat5, and interleukin-4 (IL-4) activates Stat6. Both cytokines are able to stimulate cell proliferation, differentiation, and survival. We investigated the transactivation potential of Stat6 and found that it is not restricted to lymphocytes. IL-4-dependent activation of Stat6 was also observed in HC11 mammary epithelial cells. In these cells, Stat6 activation led to the induction of the beta-casein gene promoter. The induction of this promoter was confirmed in COS7 cells. The glucocorticoid receptor was able to further enhance IL-4-induced gene transcription through the action of Stat6. Deletion analysis of the carboxyl-terminal region of Stat6 and recombination of this region with a heterologous DNA binding domain allowed the delimitation and characterization of the transactivation domain of Stat6. The potencies of the transactivation domains of Stat5, Stat6, and viral protein VP16 were compared. Stat6 had a transactivation domain which was about 10-fold stronger than that of Stat5. In pre-B cells (Ba/F3), the transactivation domain of Stat6 was IL-4 regulated, independently from its DNA binding function. PMID:9199300

  12. Transactivation, dimerization, and DNA-binding activity of white spot syndrome virus immediate-early protein IE1.

    PubMed

    Liu, Wang-Jing; Chang, Yun-Shiang; Wang, Hao-Ching; Leu, Jiann-Horng; Kou, Guang-Hsiung; Lo, Chu-Fang

    2008-11-01

    Immediate-early proteins from many viruses function as transcriptional regulators and exhibit transactivation activity, DNA binding activity, and dimerization. In this study, we investigated these characteristics in white spot syndrome virus (WSSV) immediate-early protein 1 (IE1) and attempted to map the corresponding functional domains. Transactivation was investigated by transiently expressing a protein consisting of the DNA binding domain of the yeast transactivator GAL4 fused to full-length IE1. This GAL4-IE1 fusion protein successfully activated the Autographa californica multicapsid nucleopolyhedrovirus p35 basal promoter when five copies of the GAL4 DNA binding site were inserted upstream of the TATA box. A deletion series of GAL4-IE1 fusion proteins suggested that the transactivation domain of WSSV IE1 was carried within its first 80 amino acids. A point mutation assay further showed that all 12 of the acidic residues in this highly acidic domain were important for IE1's transactivation activity. DNA binding activity was confirmed by an electrophoresis mobility shift assay using a probe with (32)P-labeled random oligonucleotides. The DNA binding region of WSSV IE1 was located in its C-terminal end (amino acids 81 to 224), but mutation of a putative zinc finger motif in this C-terminal region suggested that this motif was not directly involved in the DNA binding activity. A homotypic interaction between IE1 molecules was demonstrated by glutathione S-transferase pull-down assay and a coimmunoprecipitation analysis. A glutaraldehyde cross-linking experiment and gel filtration analysis showed that this self-interaction led to the formation of stable IE1 dimers. PMID:18768963

  13. A novel simian virus 40 early-region domain mediates transactivation of the cyclin A promoter by small-t antigen and is required for transformation in small-t antigen-dependent assays.

    PubMed Central

    Porrás, A; Bennett, J; Howe, A; Tokos, K; Bouck, N; Henglein, B; Sathyamangalam, S; Thimmapaya, B; Rundell, K

    1996-01-01

    At least three regions of the simian virus 40 small-t antigen (small-t) contribute to the protein's ability to enhance cellular transformation. As we showed previously for rat F111 cells, one region includes sequences from residues 97 to 103 that are involved in the binding and inhibition of protein phosphatase 2A. In the present study, the role of the protein phosphatase 2A binding region was confirmed in two additional small-t-dependent transformation systems. Second, small-t was found to provide a function previously identified as a large-T transformation domain. Mutations in residues 19 to 28 of large-T affected its transforming ability, but these mutations were complemented by a wild-type small-t. A third region of small-t was also required for efficient transformation. This region, the 42-47 region, is shared by large-T and small-t and contains a conserved HPDKGG hexapeptide. The 42-47 region function could be provided by either small-t or large-T in small-t-dependent systems. Mutations in the 42-47 region reduced the ability of small-t to transactivate the cyclin A promoter, of interest because small-t increased endogenous cyclin A mRNA levels in both human and monkey cells, as well as transactivating the promoter in transient assays. PMID:8794333

  14. Transcriptional regulation of the human papillomavirus-16 E6-E7 promoter by a keratinocyte-dependent enhancer, and by viral E2 trans-activator and repressor gene products: implications for cervical carcinogenesis.

    PubMed

    Cripe, T P; Haugen, T H; Turk, J P; Tabatabai, F; Schmid, P G; Dürst, M; Gissmann, L; Roman, A; Turek, L P

    1987-12-01

    The transcriptional promoter of the candidate E6-E7 transforming gene region of human papillomavirus (HPV)-16 (P97) was active in transiently transfected cervical carcinoma cells when linked to the HSV-1 tk or bacterial cat genes. Sequences 5' to P97 contain a short enhancer element responding to cellular factor(s) in uninfected human foreskin keratinocytes and in cervical carcinoma cells, but not in human or animal fibroblasts. The E2 trans-activator products of HPV-16 or of the related bovine papillomavirus (BPV)-1 further elevated HPV-16-driven transcripts in co-transfections, and required the presence of E2-binding ACC(N)6GGT cores in cis. A 'short E2' C-terminal repressor gene product (sE2) of HPV-16 or the BPV-1 sE2 repressor not only inhibited viral E2 trans-activation, but also suppressed enhancer response to keratinocytic factors. Suppression by the sE2 products was abolished by deletion of the E2-binding cores in cis or by a mutation in the sE2 DNA binding domain. The keratinocyte-dependent enhancer is likely to contribute to the epithelial cell tropism of HPV-16, and may direct persistent E6-E7 gene transcription in response to cellular factors in cervical carcinoma cells in which the viral E2 genes are inactive. PMID:2448139

  15. NF-κB accumulation associated with COL1A1 transactivators defects during chronological aging represses type I collagen expression through a -112/-61-bp region of the COL1A1 promoter in human skin fibroblasts.

    PubMed

    Bigot, Nicolas; Beauchef, Gallic; Hervieu, Magalie; Oddos, Thierry; Demoor, Magali; Boumediene, Karim; Galéra, Philippe

    2012-10-01

    The aging process, especially of the skin, is governed by changes in the epidermal, dermo-epidermal, and dermal compartments. Type I collagen, which is the major component of dermis extracellular matrix (ECM), constitutes a prime target for intrinsic and extrinsic aging-related alterations. In addition, under the aging process, pro-inflammatory signals are involved and collagens are fragmented owing to enhanced matrix metalloproteinase activities, and fibroblasts are no longer able to properly synthesize collagen fibrils. Here, we demonstrated that low levels of type I collagen detected in aged skin fibroblasts are attributable to an inhibition of COL1A1 transcription. Indeed, on one hand, we observed decreased binding activities of specific proteins 1 and 3, CCAAT-binding factor, and human collagen-Krüppel box, which are well-known COL1A1 transactivators acting through the -112/-61-bp promoter sequence. On the other hand, the aging process was accompanied by elevated amounts and binding activities of NF-κB (p65 and p50 subunits), together with an increased number of senescent cells. The forced expression of NF-κB performed in young fibroblasts was able to establish an old-like phenotype by repressing COL1A1 expression through the short -112/-61-bp COL1A1 promoter and by elevating the senescent cell distribution. The concomitant decrease of transactivator functions and increase of transinhibitor activity is responsible for ECM dysfunction, leading to aging/senescence in dermal fibroblasts.

  16. Selective modulation of MHC class II chaperons by a novel IFN-γ-inducible class II transactivator variant in lung adenocarcinoma A549 cells.

    PubMed

    Chiu, Bau-Lin; Li, Chia-Hsuan; Chang, Chien-Chung

    2013-10-11

    Class II transactivator (CIITA) plays a critical role in controlling major histocompatibility complex (MHC) class II gene expression. In this study, two novel alternatively spliced variants of human interferon (IFN)-γ-inducible CIITA, one missing exon 7 (CIITAΔE7), the other with TAG inserted at exon 4/5 junction (CIITA-TAG), were identified and characterized. Both variants are naturally occurring since they are present in primary cells. Unlike CIITA-TAG, CIITAΔE7 is expressed more abundantly in lung adenocarcinoma A549 cells than in the non-transformed counterpart BEAS-2B cells following IFN-γ stimulation. Transfection experiments showed that CIITAΔE7 induced a markedly lower level of surface HLA-DR, -DP, -DQ expression than CIITA-TAG in A549 cells but not in BEAS-2B cells, although both variants elicited similar amounts of total DR, DP, and DQ proteins. This differential effect was correlated with, in A549 cells, decreased expression of Ii and HLA-DM genes, along with increased expression of HLA-DO genes. Ii and HLA-DM are chaperons assisting in HLA class II assembly, while HLA-DO functions to inhibit endosomal peptide loading and HLA class II membrane transport. These findings raise the possibility that CIITAΔE7 interacts with unknown cancer-associated factors to selectively modulate genes involved in the assembly and transport of HLA class II molecules.

  17. Interferon-β Induces Cellular Senescence in Cutaneous Human Papilloma Virus-Transformed Human Keratinocytes by Affecting p53 Transactivating Activity

    PubMed Central

    Chiantore, Maria V.; Vannucchi, Serena; Accardi, Rosita; Tommasino, Massimo; Percario, Zulema A.; Vaccari, Gabriele; Affabris, Elisabetta; Fiorucci, Gianna; Romeo, Giovanna

    2012-01-01

    Interferon (IFN)-β inhibits cell proliferation and affects cell cycle in keratinocytes transformed by both mucosal high risk Human Papilloma Virus (HPV) and cutaneous HPV E6 and E7 proteins. In particular, upon longer IFN-β treatments, cutaneous HPV38 expressing cells undergo senescence. IFN-β appears to induce senescence by upregulating the expression of the tumor suppressor PML, a well known IFN-induced gene. Indeed, experiments in gene silencing via specific siRNAs have shown that PML is essential in the execution of the senescence programme and that both p53 and p21 pathways are involved. IFN-β treatment leads to a modulation of p53 phosphorylation and acetylation status and a reduction in the expression of the p53 dominant negative ΔNp73. These effects allow the recovery of p53 transactivating activity of target genes involved in the control of cell proliferation. Taken together, these studies suggest that signaling through the IFN pathway might play an important role in cellular senescence. This additional understanding of IFN antitumor action and mechanisms influencing tumor responsiveness or resistance appears useful in aiding further promising development of biomolecular strategies in the IFN therapy of cancer. PMID:22615843

  18. The cAMP responsive element binding protein 1 transactivates epithelial membrane protein 2, a potential tumor suppressor in the urinary bladder urothelial carcinoma.

    PubMed

    Li, Chien-Feng; Wu, Wen-Jeng; Wu, Wen-Ren; Liao, Yu-Jing; Chen, Lih-Ren; Huang, Chun-Nung; Li, Ching-Chia; Li, Wei-Ming; Huang, Hsuan-Ying; Chen, Yi-Ling; Liang, Shih-Shin; Chow, Nan-Haw; Shiue, Yow-Ling

    2015-04-20

    In this study, we report that EMP2 plays a tumor suppressor role by inducing G2/M cell cycle arrest, suppressing cell viability, proliferation, colony formation/anchorage-independent cell growth via regulation of G2/M checkpoints in distinct urinary bladder urothelial carcinoma (UBUC)-derived cell lines. Genistein treatment or exogenous expression of the cAMP responsive element binding protein 1 (CREB1) gene in different UBUC-derived cell lines induced EMP2 transcription and subsequent translation. Mutagenesis on either or both cAMP-responsive element(s) dramatically decreased the EMP2 promoter activity with, without genistein treatment or exogenous CREB1 expression, respectively. Significantly correlation between the EMP2 immunointensity and primary tumor, nodal status, histological grade, vascular invasion and mitotic activity was identified. Multivariate analysis further demonstrated that low EMP2 immunoexpression is an independent prognostic factor for poor disease-specific survival. Genistein treatments, knockdown of EMP2 gene and double knockdown of CREB1 and EMP2 genes significantly inhibited tumor growth and notably downregulated CREB1 and EMP2 protein levels in the mice xenograft models. Therefore, genistein induced CREB1 transcription, translation and upregulated pCREB1(S133) protein level. Afterward, pCREB1(S133) transactivated the tumor suppressor gene, EMP2, in vitro and in vivo. Our study identified a novel transcriptional target, which plays a tumor suppressor role, of CREB1.

  19. Activating transcription factor 4 mediates a multidrug resistance phenotype of esophageal squamous cell carcinoma cells through transactivation of STAT3 expression.

    PubMed

    Zhu, Hongwu; Chen, Xiong; Chen, Bin; Chen, Bei; Fan, Jianyong; Song, Weibing; Xie, Ziying; Jiang, Dan; Li, Qiuqiong; Zhou, Meihua; Sun, Dayong; Zhao, Yagang

    2014-11-01

    Multidrug resistance (MDR) is a major challenge to the clinical treatment of esophageal cancer. The stress response gene activating transcription factor 4 (ATF4) is involved in homeostasis and cellular protection. However, relatively little is known about the expression and function of ATF4 in esophageal squamous cell carcinoma (ESCC) MDR. In this study, we investigate the potential role and mechanisms of ATF4 in ESCC MDR. We demonstrated that overexpression of ATF4 promotes the MDR phenotype in ESCC cells, while depletion of ATF4 in the MDR ESCC cell line induces drug re-sensitization. We also demonstrated that ATF4 transactivates STAT3 expression by directly binding to the signal transducers and activators of transcription 3 (STAT3) promoter, resulting in MDR in ESCC cells. Significantly, inhibition of STAT3 by small interfering RNA (siRNA) or a selective inhibitor (JSI-124) reintroduces therapeutic sensitivity. In addition, increased Bcl-2, survivin, and MRP1 expression levels were observed in ATF4-overexpressing cells. In conclusion, ATF4 may promote MDR in ESCC cells through the up-regulation of STAT3 expression, and thus is an attractive therapeutic target to combat therapeutic resistance in ESCC.

  20. Molecular Cloning Reveals that the p160 Myb-Binding Protein Is a Novel, Predominantly Nucleolar Protein Which May Play a Role in Transactivation by Myb

    PubMed Central

    Tavner, Fiona J.; Simpson, Richard; Tashiro, Shigeki; Favier, Diane; Jenkins, Nancy A.; Gilbert, Debra J.; Copeland, Neal G.; Macmillan, Elizabeth M.; Lutwyche, Jodi; Keough, Rebecca A.; Ishii, Shunsuke; Gonda, Thomas J.

    1998-01-01

    We have previously detected two related murine nuclear proteins, p160 and p67, that can bind to the leucine zipper motif within the negative regulatory domain of the Myb transcription factor. We now describe the molecular cloning of cDNA corresponding to murine p160. The P160 gene is located on mouse chromosome 11, and related sequences are found on chromosomes 1 and 12. The predicted p160 protein is novel, and in agreement with previous studies, we find that the corresponding 4.5-kb mRNA is ubiquitously expressed. We showed that p67 is an N-terminal fragment of p160 which is generated by proteolytic cleavage in certain cell types. The protein encoded by the cloned p160 cDNA and an engineered protein (p67*) comprising the amino-terminal region of p160 exhibit binding specificities for the Myb and Jun leucine zipper regions identical to those of endogenous p160 and p67, respectively. This implies that the Myb-binding site of p160 lies within the N-terminal 580 residues and that the Jun-binding site is C-terminal to this position. Moreover, we show that p67* but not p160 can inhibit transactivation by Myb. Unexpectedly, immunofluorescence studies show that p160 is localized predominantly in the nucleolus. The implications of these results for possible functions of p160 are discussed. PMID:9447996

  1. Ammonia-induced Na,K-ATPase/ouabain-mediated EGF receptor transactivation, MAPK/ERK and PI3K/AKT signaling and ROS formation cause astrocyte swelling.

    PubMed

    Dai, Hongliang; Song, Dan; Xu, Junnan; Li, Baoman; Hertz, Leif; Peng, Liang

    2013-11-01

    Ammonia toxicity is clinically important and biologically poorly understood. We reported previously that 3mM ammonia chloride (ammonia), a relevant concentration for hepatic encephalopathy studies, increases production of endogenous ouabain and activity of Na,K-ATPase in astrocytes. In addition, ammonia-induced upregulation of gene expression of α2 isoform of Na,K-ATPase in astrocytes could be inhibited by AG1478, an inhibitor of the EGF receptor (EGFR), and by PP1, an inhibitor of Src, but not by GM6001, an inhibitor of metalloproteinase and shedding of growth factor, suggesting the involvement of endogenous ouabain-induced EGF receptor transactivation. In the present cell culture study, we investigated ammonia effects on phosphorylation of EGF receptor and its intracellular signal pathway towards MAPK/ERK1/2 and PI3K/AKT; interaction between EGF receptor, α1, and α2 isoforms of Na,K-ATPase, Src, ERK1/2, AKT and caveolin-1; and relevance of these signal pathways for ammonia-induced cell swelling, leading to brain edema, an often fatal complication of ammonia toxicity. We found that (i) ammonia increases EGF receptor phosphorylation at EGFR(845) and EGFR(1068); (ii) ammonia-induced ERK1/2 and AKT phosphorylation depends on the activity of EGF receptor and Src, but not on metalloproteinase; (iii) AKT phosphorylation occurs upstream of ERK1/2 phosphorylation; (iv) ammonia stimulates association between the α1 Na,K-ATPase isoform, Src, EGF receptor, ERK1/2, AKT and caveolin-1; (v) ammonia-induced ROS production might occur later than EGFR transactivation; (vi) both ammonia induced ERK phosphorylation and ROS production can be abolished by canrenone, an inhibitor of ouabain, and (vii) ammonia-induced cell swelling depends on signaling via the Na,K-ATPase/ouabain/Src/EGF receptor/PI3K-AKT/ERK1/2, but in response to 3mM ammonia it does not appear until after 12h. Based on literature data it is suggested that the delayed appearance of the ammonia-induced swelling at

  2. Retinoic acid receptor alpha mediates growth inhibition by retinoids in human colon carcinoma HT29 cells.

    PubMed

    Nicke, B; Kaiser, A; Wiedenmann, B; Riecken, E O; Rosewicz, S

    1999-08-11

    Although retinoids have been suggested to inhibit chemically induced colon carcinogenesis, the molecular mechanisms underlying retinoid-mediated growth regulation in colon carcinoma cells are unknown. Therefore, we investigated the biological effects of retinoids on growth in HT29 colon carcinoma cells. All-trans retinoic acid (ATRA) treatment of HT29 cells resulted in a profound inhibition of anchorage-independent growth without biochemical or morphological evidence for induction of differentiation. Treatment with the selective RARalpha agonist Ro 40-6055 completely mimicked the effects of ATRA on growth and transactivation of a betaRAREx2-luciferase reporter construct, while RARbeta- and gamma-specific analogues were ineffective. Furthermore, ATRA-regulated growth and transactivation could be completely blocked by a RARalpha-selective receptor antagonist. Thus, ATRA potently inhibits anchorage-independent growth in HT29 cells and this effect is mainly if not exclusively mediated by the retinoic acid receptor alpha.

  3. Synthesis, characterization and properties of a family of lead(II)-organic frameworks based on a multi-functional ligand 2-amino-4-sulfobenzoic acid exhibiting auxiliary ligand-dependent dehydration-rehydration behaviours.

    PubMed

    Zhang, Kou-Lin; Zhong, Zhao-Yin; Zhang, Lei; Jing, Chu-Yue; Daniels, Luke M; Walton, Richard I

    2014-08-14

    A systematic investigation is reported of the use of the multi-functional ligand 2-amino-4-sulfobenzoate (asba(2-)) to construct lead(II)-organic frameworks in the presence and absence of N-donor auxiliary ligands phen, bipy and bix [phen = 1,10-phenanthroline, bipy = 2,2'-bipyridine and bix = 1,4-(methylene-benzene)bisimidazole]. Under ambient, aqueous conditions the assembly of asba(2-) with Pb(II) and phen or bipy leads to two iso-structural 2D double-layer frameworks, {[Pb2(asba)2(phen)2(H2O)]·2H2O}n (1) and {[Pb2(asba)2(bipy)2(H2O)]·2H2O}n (2). [Pb2(asba)2(bix)2(H2O)2]n (3) is obtained in the presence of the auxiliary ligand bix and possesses a 3D network built up from 2D Pb(II)-asba(2-)-bridged double-layer pillared by bix. A 2D (4,4) topological network [Pb(asba)(H2O)]n (4) is obtained in the absence of any second ligand or presence of some bistriazole bridging spacers. The coordination modes of the ligand asba(2-) in 1-4 are greatly dependent on the type of auxiliary ligand and the compounds exhibit auxiliary ligand-dependent dehydration-rehydration behaviours; 1 shows in situ rapid and reversible dehydration-rehydration behaviour in air, while the iso-structural compound 2 loses crystallinity in air and transforms into {[Pb2(asba)2(bipy)2(H2O)]·H2O}n (2A) verified by TGA, elemental analysis and powder X-ray diffraction analysis (PXRD). 3 also shows reversible dehydration-rehydration behaviour, but it takes around one week to rehydrate even after exposure to water vapor, while the dehydrated phase of 4 rehydrates to a new crystalline material. 1 and 3 fall within the category of the "recoverable collapsing" and "guest-induced re-formation" frameworks. The water molecules in 1 and 3 have some influence on their solid state fluorescent emission intensity.

  4. Generation and characterization of a transgenic zebrafish expressing the reverse tetracycline transactivator.

    PubMed

    Gu, Qilin; Yang, Xiaojie; He, Xiaozhen; Li, Qing; Cui, Zongbin

    2013-10-20

    Conditional expression of a target gene during zebrafish development is a powerful approach to elucidate gene functions. The tetracycline-controlled systems have been successfully used in the modulation of gene expression in mammalian cells, but few lines of zebrafish carrying these systems are currently available. In this study, we had generated a stable transgenic zebrafish line that ubiquitously expressed the second-generation of reverse Tet transactivator (rtTA-M2). Southern blotting analysis and high-throughput genome sequencing verified that a single copy of rtTA-M2 gene had stably integrated into the zebrafish genome. After induction with doxycycline (Dox), a strong green fluorescent protein (GFP) was seen in rtTA-transgenic eggs injected with pTRE-EGFP plasmids. The fluorescent signal gradually decreased after the withdrawal of Dox and disappeared. However, leaky expression of GFP was undetectable before Dox-induction. Additionally, transgenic embryos expressing rtTA-M2 exhibited no obvious defects in morphological phenotypes, hatching behavior and expression patterns of developmental marker genes, suggesting that rtTA-M2 had little effect on the development of transgenic zebrafish. Moreover, expressed Dickkopf-1 (DKK1) in pTRE-DKK1-injected embryos led to alterations in the expression of marker genes associated with Wnt signaling. Thus, this rtTA-transgenic zebrafish can be utilized to dissect functions of genes in a temporal manner.

  5. Transactivation and Coactivator Recruitment Assays for Measuring Farnesoid X Receptor Activity.

    PubMed

    Hsu, Chia-Wen Amy; Zhao, Jinghua; Xia, Menghang

    2016-01-01

    The farnesoid X receptor (FXR) is a nuclear receptor responsible for homeostasis of bile acids, lipids, and glucose. Compounds that alter endogenous FXR signaling can be used as therapeutic candidates or identified as potentially hazardous compounds depending on exposure doses and health states. Therefore, there is an increasing need for high-throughput screening assays of FXR activity to profile large numbers of environmental chemicals and drugs. This chapter describes a workflow of FXR modulator identification and characterization. To identify compounds that modulate FXR transactivation at the cellular level, we first screen compounds from the Tox21 10 K compound library in an FXR-driven beta-lactamase reporter gene assay multiplexed with a cell viability assay in the same well of the 1536-well plates. The selected compounds are then tested biochemically for their ability to modulate FXR-coactivator binding interactions using a time-resolved fluorescence resonance energy transfer (TR-FRET) coactivator assay. The assay results from the workflow can be used to prioritize compounds for more extensive investigations. PMID:27518622

  6. The c-Myc Transactivation Domain Is a Direct Modulator of Apoptotic versus Proliferative Signals

    PubMed Central

    Chang, David W.; Claassen, Gisela F.; Hann, Stephen R.; Cole, Michael D.

    2000-01-01

    We have assayed the oncogenic, proliferative, and apoptotic activities of the frequent mutations that occur in the c-myc gene in Burkitt's lymphomas. Some alleles have a modest (50 to 60%) increase in transforming activity; however, the most frequent Burkitt's lymphoma allele (T58I) had an unexpected substantial decrease in transforming activity (85%). All alleles restored the proliferation function of c-Myc in cells that grow slowly due to a c-myc knockout. There was discordance for some alleles between apoptotic and oncogenic activities, but only the T58A allele had elevated transforming activity with a concomitant reduced apoptotic potential. We discovered a novel missense mutation, MycS71F, that had a very low apoptotic activity compared to wild-type Myc, yet this mutation has never been found in lymphomas, suggesting that there is no strong selection for antiapoptotic c-Myc alleles. MycS71F also induced very low levels of cytochrome c release from mitochondria, suggesting a mechanism of action for this mutation. Phosphopeptide mapping provided a biochemical basis for the dramatically different biological activities of the transformation-defective T58I and transformation-enhanced T58A c-Myc alleles. Furthermore, the antiapoptotic survival factor insulin-like growth factor 1 was found to suppress phosphorylation of T58, suggesting that the c-Myc transactivation domain is a direct target of survival signals. PMID:10825194

  7. Different Modes of Transactivation of Bacteriophage Mu Late Promoters by Transcription Factor C.

    PubMed

    Swapna, Ganduri; Kumari, Vandana; Nagaraja, Valakunja

    2015-01-01

    Transactivator protein C is required for the expression of bacteriophage Mu late genes from lys, I, P and mom promoters during lytic life cycle of the phage. The mechanism of transcription activation of mom gene by C protein is well understood. C activates transcription at Pmom by initial unwinding of the promoter DNA, thereby facilitating RNA polymerase (RNAP) recruitment. Subsequently, C interacts with the ß' subunit of RNAP to enhance promoter clearance. The mechanism by which C activates other late genes of the phage is not known. We carried out promoter-polymerase interaction studies with all the late gene promoters to determine the individual step of C mediated activation. Unlike at Pmom, at the other three promoters, RNAP recruitment and closed complex formation are not C dependent. Instead, the action of C at Plys, PI, and PP is during the isomerization from closed complex to open complex with no apparent effect at other steps of initiation pathway. The mechanism of transcription activation of mom and other late promoters by their common activator is different. This distinction in the mode of activation (promoter recruitment and escape versus isomerization) by the same activator at different promoters appears to be important for optimized expression of each of the late genes. PMID:26058069

  8. Brain-Targeted Delivery of Trans-Activating Transcriptor-Conjugated Magnetic PLGA/Lipid Nanoparticles

    PubMed Central

    Zhang, Yifang; Sun, Tingting; Zhang, Fang; Wu, Jian; Fu, Yanyan; Du, Yang; Zhang, Lei; Sun, Ying; Liu, YongHai; Ma, Kai; Liu, Hongzhi; Song, Yuanjian

    2014-01-01

    Magnetic poly (D,L-lactide-co-glycolide) (PLGA)/lipid nanoparticles (MPLs) were fabricated from PLGA, L-α-phosphatidylethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-amino (polyethylene glycol) (DSPE-PEG-NH2), and magnetic nanoparticles (NPs), and then conjugated to trans-activating transcriptor (TAT) peptide. The TAT-MPLs were designed to target the brain by magnetic guidance and TAT conjugation. The drugs hesperidin (HES), naringin (NAR), and glutathione (GSH) were encapsulated in MPLs with drug loading capacity (>10%) and drug encapsulation efficiency (>90%). The therapeutic efficacy of the drug-loaded TAT-MPLs in bEnd.3 cells was compared with that of drug-loaded MPLs. The cells accumulated higher levels of TAT-MPLs than MPLs. In addition, the accumulation of QD-loaded fluorescein isothiocyanate (FITC)-labeled TAT-MPLs in bEnd.3 cells was dose and time dependent. Our results show that TAT-conjugated MPLs may function as an effective drug delivery system that crosses the blood brain barrier to the brain. PMID:25187980

  9. Platelet transactivation by monocytes promotes thrombosis in heparin-induced thrombocytopenia.

    PubMed

    Tutwiler, Valerie; Madeeva, Daria; Ahn, Hyun Sook; Andrianova, Izabella; Hayes, Vincent; Zheng, X Long; Cines, Douglas B; McKenzie, Steven E; Poncz, Mortimer; Rauova, Lubica

    2016-01-28

    Heparin-induced thrombocytopenia (HIT) is characterized by a high incidence of thrombosis, unlike other antibody-mediated causes of thrombocytopenia. We have shown that monocytes complexed with surface-bound platelet factor 4 (PF4) activated by HIT antibodies contribute to the prothrombotic state in vivo, but the mechanism by which this occurs and the relationship to the requirement for platelet activation via fragment crystallizable (Fc)γRIIA is uncertain. Using a microfluidic model and human or murine blood, we confirmed that activation of monocytes contributes to the prothrombotic state in HIT and showed that HIT antibodies bind to monocyte FcγRIIA, which activates spleen tyrosine kinase and leads to the generation of tissue factor (TF) and thrombin. The combination of direct platelet activation by HIT immune complexes through FcγRIIA and transactivation by monocyte-derived thrombin markedly increases Annexin V and factor Xa binding to platelets, consistent with the formation of procoagulant coated platelets. These data provide a model of HIT wherein a combination of direct FcγRIIA-mediated platelet activation and monocyte-derived thrombin contributes to thrombosis in HIT and identifies potential new targets for lessening this risk.

  10. BFV activates the NF-kappaB pathway through its transactivator (BTas) to enhance viral transcription

    SciTech Connect

    Wang Jian; Tan Juan; Zhang Xihui; Guo Hongyan; Zhang Qicheng; Guo Tingting; Geng Yunqi; Qiao Wentao

    2010-05-10

    Multiple families of viruses have evolved sophisticated strategies to regulate nuclear factor-kappaB (NF-kappaB) signaling, which plays a pivotal role in diverse cellular events, including virus-host interactions. In this study, we report that bovine foamy virus (BFV) is able to activate the NF-kappaB pathway through the action of its transactivator, BTas. Both cellular IKKbeta and IkappaBalpha also participate in this activation. In addition, we demonstrate that BTas induces the processing of p100, which implies that BTas can activate NF-kappaB through a noncanonical pathway as well. Co-immunoprecipitation analysis shows that BTas interacts with IKK catalytic subunits (IKKalpha and IKKbeta), which may be responsible for regulation of IKK kinase activity and persistent NF-kappaB activation. Furthermore, our results indicate that the level of BTas-mediated LTR transcription correlates with the activity of cellular NF-kappaB. Together, this study suggests that BFV activates the NF-kappaB pathway through BTas to enhance viral transcription.

  11. Radical acceleration of nuclear reprogramming by chromatin remodeling with the transactivation domain of MyoD.

    PubMed

    Hirai, Hiroyuki; Tani, Tetsuya; Katoku-Kikyo, Nobuko; Kellner, Steven; Karian, Peter; Firpo, Meri; Kikyo, Nobuaki

    2011-09-01

    Induced pluripotent stem cells (iPSCs) can be created by reprogramming differentiated cells through introduction of defined genes, most commonly Oct4, Sox2, Klf4, and c-Myc (OSKM). However, this process is slow and extremely inefficient. Here, we demonstrate radical acceleration of iPSC creation with a fusion gene between Oct4 and the powerful transactivation domain (TAD) of MyoD (M(3)O). Transduction of M(3) O as well as Sox2, Klf4, and c-Myc into fibroblasts effectively remodeled patterns of DNA methylation, chromatin accessibility, histone modifications, and protein binding at pluripotency genes, raising the efficiency of making mouse and human iPSCs more than 50-fold in comparison to OSKM. These results identified that one of the most critical barriers to iPSC creation is poor chromatin accessibility and protein recruitment to pluripotency genes. The MyoD TAD has a capability of overcoming this problem. Our approach of fusing TADs to unrelated transcription factors has far-reaching implications as a powerful tool for transcriptional reprogramming beyond application to iPSC technology. PMID:21732495

  12. Abnormal XPD-induced nuclear receptor transactivation in DNA repair disorders: trichothiodystrophy and xeroderma pigmentosum.

    PubMed

    Zhou, Xiaolong; Khan, Sikandar G; Tamura, Deborah; Ueda, Takahiro; Boyle, Jennifer; Compe, Emmanuel; Egly, Jean-Marc; DiGiovanna, John J; Kraemer, Kenneth H

    2013-08-01

    XPD (ERCC2) is a DNA helicase involved in nucleotide excision repair and in transcription as a structural bridge tying the transcription factor IIH (TFIIH) core with the cdk-activating kinase complex, which phosphorylates nuclear receptors. Mutations in XPD are associated with several different phenotypes, including trichothiodystrophy (TTD), with sulfur-deficient brittle hair, bone defects, and developmental abnormalities without skin cancer, xeroderma pigmentosum (XP), with pigmentary abnormalities and increased skin cancer, or XP/TTD with combined features, including skin cancer. We describe the varied clinical features and mutations in nine patients examined at the National Institutes of Health who were compound heterozygotes for XPD mutations but had different clinical phenotypes: four TTD, three XP, and two combined XP/TTD. We studied TFIIH-dependent transactivation by nuclear receptor for vitamin D (VDR) and thyroid in cells from these patients. The vitamin D stimulation ratio of CYP24 and osteopontin was associated with specific pairs of mutations (reduced in 5, elevated in 1) but not correlated with distinct clinical phenotypes. Thyroid receptor stimulation ratio for KLF9 was not significantly different from normal. XPD mutations frequently were associated with abnormal VDR stimulation in compound heterozygote patients with TTD, XP, or XP/TTD. PMID:23232694

  13. Transactivation of the proximal promoter of human oxytocin gene by TR4 orphan receptor

    SciTech Connect

    Wang, C.-P.; Lee, Y.-F.; Chang, C.; Lee, H.-J. . E-mail: hjlee@mail.ndhu.edu.tw

    2006-12-08

    The human testicular receptor 4 (TR4) shares structural homology with members of the nuclear receptor superfamily. Some other members of this superfamily were able to regulate the transcriptional activity of the human oxytocin (OXT) promoter by binding to the first DR0 regulatory site. However, little investigation was conducted systematically in the study of the second dDR4 site of OXT proximal promoter, and the relationship between the first and the second sites of OXT promoter. Here, we demonstrated for the first time that TR4 could increase the proximal promoter activity of the human OXT gene via DR0, dDR4, and OXT (both DR0 and dDR4) elements, respectively. TR4 might induce OXT gene expression through the OXT element in a dose-dependent manner. However, there is no synergistic effect between DR0 and dDR4 elements during TR4 transactivation. Taken together, these results suggested that TR4 should be one of important regulators of OXT gene expression.

  14. Phosphorylation of RAF Kinase Dimers Drives Conformational Changes that Facilitate Transactivation

    PubMed Central

    Jambrina, Pablo G.; Rauch, Nora; Pilkington, Ruth; Rybakova, Katja; Nguyen, Lan K.; Kholodenko, Boris N.; Buchete, Nicolae‐Viorel

    2015-01-01

    Abstract RAF kinases are key players in the MAPK signaling pathway and are important targets for personalized cancer therapy. RAF dimerization is part of the physiological activation mechanism, together with phosphorylation, and is known to convey resistance to RAF inhibitors. Herein, molecular dynamics simulations are used to show that phosphorylation of a key N‐terminal acidic (NtA) motif facilitates RAF dimerization by introducing several interprotomer salt bridges between the αC‐helix and charged residues upstream of the NtA motif. Additionally, we show that the R‐spine of RAF interacts with a conserved Trp residue in the vicinity of the NtA motif, connecting the active sites of two protomers and thereby modulating the cooperative interactions in the RAF dimer. Our findings provide a first structure‐based mechanism for the auto‐transactivation of RAF and could be generally applicable to other kinases, opening new pathways for overcoming dimerization‐related drug resistance. PMID:26644280

  15. Transactivation and Coactivator Recruitment Assays for Measuring Farnesoid X Receptor Activity.

    PubMed

    Hsu, Chia-Wen Amy; Zhao, Jinghua; Xia, Menghang

    2016-01-01

    The farnesoid X receptor (FXR) is a nuclear receptor responsible for homeostasis of bile acids, lipids, and glucose. Compounds that alter endogenous FXR signaling can be used as therapeutic candidates or identified as potentially hazardous compounds depending on exposure doses and health states. Therefore, there is an increasing need for high-throughput screening assays of FXR activity to profile large numbers of environmental chemicals and drugs. This chapter describes a workflow of FXR modulator identification and characterization. To identify compounds that modulate FXR transactivation at the cellular level, we first screen compounds from the Tox21 10 K compound library in an FXR-driven beta-lactamase reporter gene assay multiplexed with a cell viability assay in the same well of the 1536-well plates. The selected compounds are then tested biochemically for their ability to modulate FXR-coactivator binding interactions using a time-resolved fluorescence resonance energy transfer (TR-FRET) coactivator assay. The assay results from the workflow can be used to prioritize compounds for more extensive investigations.

  16. Structure-based design of a potent artificial transactivation domain based on p53.

    PubMed

    Langlois, Chantal; Del Gatto, Annarita; Arseneault, Geneviève; Lafrance-Vanasse, Julien; De Simone, Mariarosaria; Morse, Thomas; de Paola, Ivan; Lussier-Price, Mathieu; Legault, Pascale; Pedone, Carlo; Zaccaro, Laura; Omichinski, James G

    2012-01-25

    Malfunctions in transcriptional regulation are associated with a number of critical human diseases. As a result, there is considerable interest in designing artificial transcription activators (ATAs) that specifically control genes linked to human diseases. Like native transcriptional activator proteins, an ATA must minimally contain a DNA-binding domain (DBD) and a transactivation domain (TAD) and, although there are several reliable methods for designing artificial DBDs, designing artificial TADs has proven difficult. In this manuscript, we present a structure-based strategy for designing short peptides containing natural amino acids that function as artificial TADs. Using a segment of the TAD of p53 as the scaffolding, modifications are introduced to increase the helical propensity of the peptides. The most active artificial TAD, termed E-Cap-(LL), is a 13-mer peptide that contains four key residues from p53, an N-capping motif and a dileucine hydrophobic bridge. In vitro analysis demonstrates that E-Cap-(LL) interacts with several known p53 target proteins, while in vivo studies in a yeast model system show that it is a 20-fold more potent transcriptional activator than the native p53-13 peptide. These results demonstrate that structure-based design represents a promising approach for developing artificial TADs that can be combined with artificial DBDs to create potent and specific ATAs. PMID:22191432

  17. SIP1/NHERF2 enhances estrogen receptor alpha transactivation in breast cancer cells

    PubMed Central

    Meneses-Morales, Ivan; Tecalco-Cruz, Angeles C.; Barrios-García, Tonatiuh; Gómez-Romero, Vania; Trujillo-González, Isis; Reyes-Carmona, Sandra; García-Zepeda, Eduardo; Méndez-Enríquez, Erika; Cervantes-Roldán, Rafael; Pérez-Sánchez, Víctor; Recillas-Targa, Félix; Mohar-Betancourt, Alejandro; León-Del-Río, Alfonso

    2014-01-01

    The estrogen receptor alpha (ERα) is a ligand-activated transcription factor that possesses two activating domains designated AF-1 and AF-2 that mediate its transcriptional activity. The role of AF-2 is to recruit coregulator protein complexes capable of modifying chromatin condensation status. In contrast, the mechanism responsible for the ligand-independent AF-1 activity and for its synergistic functional interaction with AF-2 is unclear. In this study, we have identified the protein Na+/H+ Exchanger RegulatoryFactor 2 (NHERF2) as an ERα-associated coactivator that interacts predominantly with the AF-1 domain of the nuclear receptor. Overexpression of NHERF2 in breast cancer MCF7 cells produced an increase in ERα transactivation. Interestingly, the presence of SRC-1 in NHERF2 stably overexpressing MCF7 cells produced a synergistic increase in ERα activity. We show further that NHERF2 interacts with ERα and SRC-1 in the promoter region of ERα target genes. The binding of NHERF2 to ERα in MCF7 cells increased cell proliferation and the ability of MCF7 cells to form tumors in a mouse model. We analyzed the expression of NHERF2 in breast cancer tumors finding a 2- to 17-fold increase in its mRNA levels in 50% of the tumor samples compared to normal breast tissue. These results indicate that NHERF2 is a coactivator of ERα that may participate in the development of estrogen-dependent breast cancer tumors. PMID:24771346

  18. SIP1/NHERF2 enhances estrogen receptor alpha transactivation in breast cancer cells.

    PubMed

    Meneses-Morales, Ivan; Tecalco-Cruz, Angeles C; Barrios-García, Tonatiuh; Gómez-Romero, Vania; Trujillo-González, Isis; Reyes-Carmona, Sandra; García-Zepeda, Eduardo; Méndez-Enríquez, Erika; Cervantes-Roldán, Rafael; Pérez-Sánchez, Víctor; Recillas-Targa, Félix; Mohar-Betancourt, Alejandro; León-Del-Río, Alfonso

    2014-06-01

    The estrogen receptor alpha (ERα) is a ligand-activated transcription factor that possesses two activating domains designated AF-1 and AF-2 that mediate its transcriptional activity. The role of AF-2 is to recruit coregulator protein complexes capable of modifying chromatin condensation status. In contrast, the mechanism responsible for the ligand-independent AF-1 activity and for its synergistic functional interaction with AF-2 is unclear. In this study, we have identified the protein Na+/H+ Exchanger RegulatoryFactor 2 (NHERF2) as an ERα-associated coactivator that interacts predominantly with the AF-1 domain of the nuclear receptor. Overexpression of NHERF2 in breast cancer MCF7 cells produced an increase in ERα transactivation. Interestingly, the presence of SRC-1 in NHERF2 stably overexpressing MCF7 cells produced a synergistic increase in ERα activity. We show further that NHERF2 interacts with ERα and SRC-1 in the promoter region of ERα target genes. The binding of NHERF2 to ERα in MCF7 cells increased cell proliferation and the ability of MCF7 cells to form tumors in a mouse model. We analyzed the expression of NHERF2 in breast cancer tumors finding a 2- to 17-fold increase in its mRNA levels in 50% of the tumor samples compared to normal breast tissue. These results indicate that NHERF2 is a coactivator of ERα that may participate in the development of estrogen-dependent breast cancer tumors.

  19. Transactivation of vimentin by beta-catenin in human breast cancer cells.

    PubMed

    Gilles, Christine; Polette, Myriam; Mestdagt, Mélanie; Nawrocki-Raby, Béatrice; Ruggeri, Philippe; Birembaut, Philippe; Foidart, Jean-Michel

    2003-05-15

    The cytoplasmic and nuclear redistribution of beta-catenin and the de novo expression of vimentin are frequently involved in the epithelial-to-mesenchymal transition associated with increased invasive/migratory properties of epithelial cells. Because beta-catenin can act as a coactivator of transcription through its binding to the T-cell factor (TCF)/lymphoid enhancer factor 1 transcription factor family, we have explored the possibility that beta-catenin/TCF could directly transactivate vimentin. We first compared vimentin expression in relation with the localization of beta-catenin in eight breast cancer cell lines displaying various degrees of invasiveness and in a model of cell migration using human mammary MCF10A cells. We could thus show a cytoplasmic and/or nuclear distribution of beta-catenin in invasive/migratory cells expressing vimentin, but not in noninvasive/stationary vimentin-negative cell lines. In addition, the human vimentin promoter was found to be up-regulated by beta-catenin and TCF-4 cotransfection. Varying with the cellular background, a diminution of this up-regulation was observed when the putative beta-catenin/TCF binding site of the vimentin promoter was mutated. Our results therefore demonstrate that the vimentin promoter is a target of the beta-catenin/TCF pathway and strongly suggest an implication of this regulation in epithelial cell migration/invasion.

  20. SIP1/NHERF2 enhances estrogen receptor alpha transactivation in breast cancer cells.

    PubMed

    Meneses-Morales, Ivan; Tecalco-Cruz, Angeles C; Barrios-García, Tonatiuh; Gómez-Romero, Vania; Trujillo-González, Isis; Reyes-Carmona, Sandra; García-Zepeda, Eduardo; Méndez-Enríquez, Erika; Cervantes-Roldán, Rafael; Pérez-Sánchez, Víctor; Recillas-Targa, Félix; Mohar-Betancourt, Alejandro; León-Del-Río, Alfonso

    2014-06-01

    The estrogen receptor alpha (ERα) is a ligand-activated transcription factor that possesses two activating domains designated AF-1 and AF-2 that mediate its transcriptional activity. The role of AF-2 is to recruit coregulator protein complexes capable of modifying chromatin condensation status. In contrast, the mechanism responsible for the ligand-independent AF-1 activity and for its synergistic functional interaction with AF-2 is unclear. In this study, we have identified the protein Na+/H+ Exchanger RegulatoryFactor 2 (NHERF2) as an ERα-associated coactivator that interacts predominantly with the AF-1 domain of the nuclear receptor. Overexpression of NHERF2 in breast cancer MCF7 cells produced an increase in ERα transactivation. Interestingly, the presence of SRC-1 in NHERF2 stably overexpressing MCF7 cells produced a synergistic increase in ERα activity. We show further that NHERF2 interacts with ERα and SRC-1 in the promoter region of ERα target genes. The binding of NHERF2 to ERα in MCF7 cells increased cell proliferation and the ability of MCF7 cells to form tumors in a mouse model. We analyzed the expression of NHERF2 in breast cancer tumors finding a 2- to 17-fold increase in its mRNA levels in 50% of the tumor samples compared to normal breast tissue. These results indicate that NHERF2 is a coactivator of ERα that may participate in the development of estrogen-dependent breast cancer tumors. PMID:24771346

  1. Immediate-early gene region of human cytomegalovirus trans-activates the promoter of human immunodeficiency virus

    SciTech Connect

    Davis, M.G.; Kenney, S.C.; Kamine, J.; Pagano, J.S.; Huang, E.S.

    1987-12-01

    Almost all homosexual patients with acquired immunodeficiency syndrome are also actively infected with human cytomegalovirus (HCMV). The authors have hypothesized that an interaction between HCMV and human immunodeficiency virus (HIV), the agent that causes acquired immunodeficiency syndrome, may exist at a molecular level and contribute to the manifestations of HIV infection. In this report, they demonstrate that the immediate-early gene region of HCMV, in particular immediate-early region 2, trans-activates the expression of the bacterial gene chloramphenicol acetyltransferase that is fused to the HIV long terminal repeat and carried by plasmid pHIV-CAT. The HCMV immediate-early trans-activator increases the level of mRNA from the plamid pHIV-CAT. The sequences of HIV that are responsive to trans-activation by the HDMV immediate-early region are distinct from HIV sequences that are required for response to the HIV tat. The stimulation of HIV gene expression by HDMV gene functions could enhance the consequences of HIV infection in persons with previous or concurrent HCMV infection.

  2. Lysophosphatidic Acid-induced ERK Activation and Chemotaxis in MC3T3-E1 Preosteoblasts are Independent of EGF Receptor Transactivation

    SciTech Connect

    Karagiosis, Sue A.; Chrisler, William B.; Bollinger, Nikki; Karin, Norman J.

    2009-06-01

    Growing evidence indicates that bone-forming osteoblasts and their progenitors are target cells for the lipid growth factor lysophosphatidic acid (LPA) which is produced by degranulating platelets at sites of injury. LPA is a potent inducer of bone cell migration, proliferation and survival in vitro and an attractive candidate to facilitate preosteoblast chemotaxis during skeletal regeneration in vivo, but the intracellular signaling pathways mediating the effects of this lipid on bone cells are not defined. In this study we measured the ability of LPA to stimulate extracellular signal-related kinase (ERK1/2) in MC3T3-E1 preosteoblastic cells and determined the contribution of this pathway to LPA-stimulated chemotaxis. LPA-treated cells exhibited a bimodal activation of ERK1/2 with maximal phosphorylation at 5 and 60 minutes. The kinetics of ERK1/2 phosphorylation were not coupled to Ras activation or LPA-induced elevations in cytosolic Ca2+. While LPA is coupled to the transactivation of the EGF receptor in many cell types, LPA-stimulated ERK1/2 activation in MC3T3-E1 cells was unaffected by inhibition of EGF receptor function. ERK isoforms rapidly accumulated at nuclear sites in LPA-treated cells, a process that was blocked if ERK1/2 phosphorylation was prevented with the MEK1 inhibitor U0126. Blocking ERK1/2 phosphorylation with U0126 also diminished MC3T3-E1 cell migration and altered the normal disassembly of LPA-induced stress fibers, while the inhibition of EGF receptor function had no effect on LPA-coupled preosteoblast motility. Our results identify ERK1/2 activation as a mediatora mediator of LPA-stimulated MC3T3-E1 cell migration that may be relevant to preosteoblast motility during bone repair in vivo.

  3. Alpha1a-Adrenoceptor Genetic Variant Triggers Vascular Smooth Muscle Cell Hyperproliferation and Agonist Induced Hypertrophy via EGFR Transactivation Pathway.

    PubMed

    Gradinaru, Irina; Babaeva, Ekaterina; Schwinn, Debra A; Oganesian, Anush

    2015-01-01

    α1a Adrenergic receptors (α1aARs) are the predominant AR subtype in human vascular smooth muscle cells (SMCs). α1aARs in resistance vessels are crucial in the control of blood pressure, yet the impact of naturally occurring human α1aAR genetic variants in cardiovascular disorders remains poorly understood. To this end, we present novel findings demonstrating that 3D cultures of vascular SMCs expressing human α1aAR-247R (247R) genetic variant demonstrate significantly increased SMC contractility compared with cells expressing the α1aAR-WT (WT) receptor. Stable expression of 247R genetic variant also triggers MMP/EGFR-transactivation dependent serum- and agonist-independent (constitutive) hyperproliferation and agonist-dependent hypertrophy of SMCs. Agonist stimulation reduces contractility Using pathway-specific inhibitors we determined that the observed hyperproliferation of 247R-expressing cells is triggered via β-arrestin1/Src/MMP-2/EGFR/ERK-dependent mechanism. MMP-2-specific siRNA inhibited 247R-triggered hyperproliferation indicating MMP-2 involvement in 247R-triggered hyperproliferation in SMCs. β-arrestin1-specific shRNA also inhibited 247R-triggered hyperproliferation but did not affect hypertrophy in 247R-expressing SMCs, indicating that agonist-dependent hypertrophy is independent of β-arrestin1. Our data reveal that in different cardiovascular cells the same human receptor genetic variant can activate alternative modulators of the same signaling pathway. Thus, our findings in SMCs demonstrate that depending on the type of cells expressing the same receptor (or receptor variant), different target-specific inhibitors could be used to modulate aberrant hyperproliferative or hypertrophic pathways in order to restore normal phenotype.

  4. Neutrophil elastase enhances IL-12p40 production by lipopolysaccharide-stimulated macrophages via transactivation of the PAR-2/EGFR/TLR4 signaling pathway.

    PubMed

    Yamaguchi, Rui; Yamamoto, Takatoshi; Sakamoto, Arisa; Narahara, Shinji; Sugiuchi, Hiroyuki; Yamaguchi, Yasuo

    2016-07-01

    Proteinase-activated receptor 2 (PAR-2) and toll-like receptor 4 (TLR4) are involved in innate immune responses and signaling cross-talk between these receptor molecules has the potential to augment an ongoing inflammatory response. The aim of this study was to evaluate the possible cooperative influence of PAR-2 and TLR4 on IL-12p40 production by macrophages after stimulation with lipopolysaccharide (LPS). During culture, GM-CSF upregulated PAR-2 expression by macrophages in a time-dependent manner. Stimulation with LPS enhanced IL-12p40 production by macrophages in a concentration-dependent manner. While human neutrophil elastase (HNE) did not induce IL-12p40 production, pretreatment of macrophages with HNE synergistically increased the IL-12p40 protein level after LPS exposure. Silencing of TLR4 with small interfering RNA blunted the synergistic enhancement of IL-12p40 by HNE combined with LPS. Silencing of β-arrestin 2, p22phox, or ERK1/2 also inhibited an increase of IL-12p40. Interestingly, transfection of macrophages with small interfering RNA duplexes for DUOX-2, EGFR, TLR4, or TRAF6 significantly blunted the increase of IL-12p40 in response to treatment with HNE plus LPS. U73122 and Rottlerin also inhibited the increased production of IL-12p40. In conclusion, HNE is involved in transactivation of TLR4 through activation of DUOX-2/EGFR and synergistically enhances IL-12p40 production by macrophages stimulated with LPS. PMID:27282560

  5. Omega 3 but not omega 6 fatty acids inhibit AP-1 activity and cell transformation in JB6 cells

    PubMed Central

    Liu, Guangming; Bibus, Douglas M.; Bode, Ann M.; Ma, Wei-Ya; Holman, Ralph T.; Dong, Zigang

    2001-01-01

    Epidemiological and animal-based investigations have indicated that the development of skin cancer is in part associated with poor dietary practices. Lipid content and subsequently the derived fatty acid composition of the diet are believed to play a major role in the development of tumorigenesis. Omega 3 (ω3) fatty acids, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), can effectively reduce the risk of skin cancer whereas omega 6 (ω6) fatty acids such as arachidonic acid (AA) reportedly promote risk. To investigate the effects of fatty acids on tumorigenesis, we performed experiments to examine the effects of the ω3 fatty acids EPA and DHA and of the ω6 fatty acid AA on phorbol 12-tetradecanoate 13-acetate (TPA)-induced or epidermal growth factor (EGF)-induced transcription activator protein 1 (AP-1) transactivation and on the subsequent cellular transformation in a mouse epidermal JB6 cell model. DHA treatment resulted in marked inhibition of TPA- and EGF-induced cell transformation by inhibiting AP-1 transactivation. EPA treatment also inhibited TPA-induced AP-1 transactivation and cell transformation but had no effect on EGF-induced transformation. AA treatment had no effect on either TPA- or EGF-induced AP-1 transactivation or transformation, but did abrogate the inhibitory effects of DHA on TPA- or EGF-induced AP-1 transactivation and cell transformation in a dose-dependent manner. The results of this study demonstrate that the inhibitory effects of ω3 fatty acids on tumorigenesis are more significant for DHA than for EPA and are related to an inhibition of AP-1. Similarly, because AA abrogates the beneficial effects of DHA, the dietary ratio of ω6 to ω3 fatty acids may be a significant factor in mediating tumor development. PMID:11416221

  6. Exosomes Derived from HIV-1-infected Cells Contain Trans-activation Response Element RNA*

    PubMed Central

    Narayanan, Aarthi; Iordanskiy, Sergey; Das, Ravi; Van Duyne, Rachel; Santos, Steven; Jaworski, Elizabeth; Guendel, Irene; Sampey, Gavin; Dalby, Elizabeth; Iglesias-Ussel, Maria; Popratiloff, Anastas; Hakami, Ramin; Kehn-Hall, Kylene; Young, Mary; Subra, Caroline; Gilbert, Caroline; Bailey, Charles; Romerio, Fabio; Kashanchi, Fatah

    2013-01-01

    Exosomes are nano-sized vesicles produced by healthy and virus-infected cells. Exosomes derived from infected cells have been shown to contain viral microRNAs (miRNAs). HIV-1 encodes its own miRNAs that regulate viral and host gene expression. The most abundant HIV-1-derived miRNA, first reported by us and later by others using deep sequencing, is the trans-activation response element (TAR) miRNA. In this study, we demonstrate the presence of TAR RNA in exosomes from cell culture supernatants of HIV-1-infected cells and patient sera. TAR miRNA was not in Ago2 complexes outside the exosomes but enclosed within the exosomes. We detected the host miRNA machinery proteins Dicer and Drosha in exosomes from infected cells. We report that transport of TAR RNA from the nucleus into exosomes is a CRM1 (chromosome region maintenance 1)-dependent active process. Prior exposure of naive cells to exosomes from infected cells increased susceptibility of the recipient cells to HIV-1 infection. Exosomal TAR RNA down-regulated apoptosis by lowering Bim and Cdk9 proteins in recipient cells. We found 104–106 copies/ml TAR RNA in exosomes derived from infected culture supernatants and 103 copies/ml TAR RNA in the serum exosomes of highly active antiretroviral therapy-treated patients or long term nonprogressors. Taken together, our experiments demonstrated that HIV-1-infected cells produced exosomes that are uniquely characterized by their proteomic and RNA profiles that may contribute to disease pathology in AIDS. PMID:23661700

  7. Dimerization and Transactivation Domains as Candidates for Functional Modulation and Diversity of Sox9

    PubMed Central

    Geraldo, Marcos Tadeu; Valente, Guilherme Targino; Nakajima, Rafael Takahiro; Martins, Cesar

    2016-01-01

    Sox9 plays an important role in a large variety of developmental pathways in vertebrates. It is composed of three domains: high-mobility group box (HMG box), dimerization (DIM) and transactivation (TAD). One of the main processes for regulation and variability of the pathways involving Sox9 is the self-gene expression regulation of Sox9. However, the subsequent roles of the Sox9 domains can also generate regulatory modulations. Studies have shown that TADs can bind to different types of proteins and its function seems to be influenced by DIM. Therefore, we hypothesized that both domains are directly associated and can be responsible for the functional variability of Sox9. We applied a method based on a broad phylogenetic context, using sequences of the HMG box domain, to ensure the homology of all the Sox9 copies used herein. The data obtained included 4,921 sequences relative to 657 metazoan species. Based on coevolutionary and selective pressure analyses of the Sox9 sequences, we observed coevolutions involving DIM and TADs. These data, along with the experimental data from literature, indicate a functional relationship between these domains. Moreover, DIM and TADs may be responsible for the functional plasticity of Sox9 because they are more tolerant for molecular changes (higher Ka/Ks ratio than the HMG box domain). This tolerance could allow a differential regulation of target genes or promote novel targets during transcriptional activation. In conclusion, we suggest that DIM and TADs functional association may regulate differentially the target genes or even promote novel targets during transcription activation mediated by Sox9 paralogs, contributing to the subfunctionalization of Sox9a and Sox9b in teleosts. PMID:27196604

  8. Strain background influences neurotoxicity and behavioral abnormalities in mice expressing the tetracycline transactivator.

    PubMed

    Han, Harry J; Allen, Carolyn C; Buchovecky, Christie M; Yetman, Michael J; Born, Heather A; Marin, Miguel A; Rodgers, Shaefali P; Song, Bryan J; Lu, Hui-Chen; Justice, Monica J; Probst, Frank J; Jankowsky, Joanna L

    2012-08-01

    The tet-off system has been widely used to create transgenic models of neurological disorders including Alzheimer's, Parkinson's, Huntington's, and prion disease. The utility of this system lies in the assumption that the tetracycline transactivator (TTA) acts as an inert control element and does not contribute to phenotypes under study. Here we report that neuronal expression of TTA can affect hippocampal cytoarchitecture and behavior in a strain-dependent manner. While studying neurodegeneration in two tet-off Alzheimer's disease models, we unexpectedly discovered neuronal loss within the dentate gyrus of single transgenic TTA controls. Granule neurons appeared most sensitive to TTA exposure during postnatal development, and doxycycline treatment during this period was neuroprotective. TTA-induced degeneration could be rescued by moving the transgene onto a congenic C57BL/6J background and recurred on reintroduction of either CBA or C3H/He backgrounds. Quantitative trait analysis of B6C3 F2 TTA mice identified a region on Chromosome 14 that contains a major modifier of the neurodegenerative phenotype. Although B6 mice were resistant to degeneration, they were not ideal for cognitive testing. F1 offspring of TTA C57BL/6J and 129X1/SvJ, FVB/NJ, or DBA/1J showed improved spatial learning, but TTA expression caused subtle differences in contextual fear conditioning on two of these backgrounds, indicating that strain and genotype can interact independently under different behavioral settings. All model systems have limitations that should be recognized and mitigated where possible; our findings stress the importance of mapping the effects caused by TTA alone when working with tet-off models.

  9. Dimerization and Transactivation Domains as Candidates for Functional Modulation and Diversity of Sox9.

    PubMed

    Geraldo, Marcos Tadeu; Valente, Guilherme Targino; Nakajima, Rafael Takahiro; Martins, Cesar

    2016-01-01

    Sox9 plays an important role in a large variety of developmental pathways in vertebrates. It is composed of three domains: high-mobility group box (HMG box), dimerization (DIM) and transactivation (TAD). One of the main processes for regulation and variability of the pathways involving Sox9 is the self-gene expression regulation of Sox9. However, the subsequent roles of the Sox9 domains can also generate regulatory modulations. Studies have shown that TADs can bind to different types of proteins and its function seems to be influenced by DIM. Therefore, we hypothesized that both domains are directly associated and can be responsible for the functional variability of Sox9. We applied a method based on a broad phylogenetic context, using sequences of the HMG box domain, to ensure the homology of all the Sox9 copies used herein. The data obtained included 4,921 sequences relative to 657 metazoan species. Based on coevolutionary and selective pressure analyses of the Sox9 sequences, we observed coevolutions involving DIM and TADs. These data, along with the experimental data from literature, indicate a functional relationship between these domains. Moreover, DIM and TADs may be responsible for the functional plasticity of Sox9 because they are more tolerant for molecular changes (higher Ka/Ks ratio than the HMG box domain). This tolerance could allow a differential regulation of target genes or promote novel targets during transcriptional activation. In conclusion, we suggest that DIM and TADs functional association may regulate differentially the target genes or even promote novel targets during transcription activation mediated by Sox9 paralogs, contributing to the subfunctionalization of Sox9a and Sox9b in teleosts. PMID:27196604

  10. Arsenic trioxide phosphorylates c-Fos to transactivate p21{sup WAF1/CIP1} expression

    SciTech Connect

    Liu Zimiao; Huang, H.-S.

    2008-12-01

    An infamous poison, arsenic also has been used as a drug for nearly 2400 years; in recently years, arsenic has been effective in the treatment of acute promyelocytic leukemia. Increasing evidence suggests that opposite effects of arsenic trioxide (ATO) on tumors depend on its concentrations. For this reason, the mechanisms of action of the drug should be elucidated, and it should be used therapeutically only with extreme caution. Previously, we demonstrated the opposing effects of ERK1/2 and JNK on p21{sup WAF1/CIP1} (p21) expression in response to ATO in A431 cells. In addition, JNK phosphorylates c-Jun (Ser{sup 63/73}) to recruit TGIF/HDAC1 to suppress p21 gene expression. Presently, we demonstrated that a high concentration of ATO sustains ERK1/2 phosphorylation, and increases c-Fos biosynthesis and stability, which enhances p21 gene expression. Using site-directed mutagenesis, a DNA affinity precipitation assay, and functional assays, we demonstrated that phosphorylation of the C-terminus of c-Fos (Thr{sup 232}, Thr{sup 325}, Thr{sup 331}, and Ser{sup 374}) plays an important role in its binding to the p21 promoter, and in conjunction with N-terminus phosphorylation of c-Fos (Ser{sup 70}) to transactivate p21 promoter expression. In conclusion, a high concentration of ATO can sustain ERK1/2 activation to enhance c-Fos expression, then dimerize with dephosphorylated c-Jun (Ser{sup 63/73}) and recruit p300/CBP to the Sp1 sites (- 84/- 64) to activate p21 gene expression in A431 cells.

  11. Resistance of mitochondrial p53 to dominant inhibition

    PubMed Central

    Heyne, Kristina; Schmitt, Katrin; Mueller, Daniel; Armbruester, Vivienne; Mestres, Pedro; Roemer, Klaus

    2008-01-01

    Background Mutation of a tumor suppressor allele leaves the second as backup. Not necessarily so with p53. This homo-tetrameric transcription factor can become contaminated with mutant p53 through hetero-tetramerization. In addition, it can be out-competed by the binding to p53 DNA recognition motifs of transactivation-incompetent isoforms (ΔN and ΔTA-isoforms) of the p53/p63/p73 family of proteins. Countermeasures against such dominant-negative or dominant-inhibitory action might include the evolutionary gain of novel, transactivation-independent tumor suppressor functions by the wild-type monomer. Results Here we have studied, mostly in human HCT116 colon adenocarcinoma cells with an intact p53 pathway, the effects of dominant-inhibitory p53 mutants and of Δex2/3p73, a tumor-associated ΔTA-competitor of wild-type p53, on the nuclear transactivation-dependent and extra-nuclear transactivation-independent functions of wild-type p53. We report that mutant p53 and Δex2/3p73, expressed from a single gene copy per cell, interfere with the stress-induced expression of p53-responsive genes but leave the extra-nuclear apoptosis by mitochondrial p53 largely unaffected, although both wild-type and mutant p53 associate with the mitochondria. In accord with these observations, we present evidence that in contrast to nuclear p53 the vast majority of mitochondrial p53, be it wild-type or mutant, is consisting of monomeric protein. Conclusion The extra-nuclear p53-dependent apoptosis may constitute a fail-safe mechanism against dominant inhibition. PMID:18547443

  12. Transforming growth factor-β1 induces EMT by the transactivation of epidermal growth factor signaling through HA/CD44 in lung and breast cancer cells.

    PubMed

    Li, Lingmei; Qi, Lisha; Liang, Zhijie; Song, Wangzhao; Liu, Yanxue; Wang, Yalei; Sun, Baocun; Zhang, Bin; Cao, Wenfeng

    2015-07-01

    Epithelial-mesenchymal transition (EMT), a process closely related to tumor development, is regulated by a variety of signaling pathways and growth factors, such as transforming growth factor-β1 (TGF-β1) and epidermal growth factor (EGF). Hyaluronan (HA) has been shown to induce EMT through either TGF-β1 or EGF signaling and to be a regulator of the crosstalk between these two pathways in fibroblasts. In this study, in order to clarify whether HA has the same effect in tumor cells, we utilized the lung cancer cell line, A549, and the breast cancer cell line, MCF-7, and found that the effects of stimulation with TGF-β1 were more potent than those of EGF in regulating the expression of EMT-associated proteins and in enhancing cell migration and invasion. In addition, we observed that TGF-β1 activated EGF receptor (EGFR) and its downstream AKT and extracellular signal-regulated kinase (ERK) pathways. Furthermore, we found that TGF-β1 upregulated the expression of hyaluronan synthases (HAS1, HAS2 and HAS3) and promoted the expression of CD44, a cell surface receptor for HA, which interacts with EGFR, resulting in the activation of the downstream AKT and ERK pathways. Conversely, treatment with 4-methylumbelliferone (4-MU; an inhibitor of HAS) prior to stimulation with TGF-β1, inhibited the expression of CD44 and EGFR, abolished the interaction between CD44 and EGFR. Furthermore, the use of shRNA targeting CD44 impaired the expression of EGFR, deactivated the AKT and ERK pathways, reversed EMT and decreased the migration and invasion ability of cells. In conclusion, our data demonstrate that TGF-β1 induces EMT by the transactivation of EGF signaling through HA/CD44 in lung and breast cancer cells.

  13. Niacin activates the PI3K/Akt cascade via PKC- and EGFR-transactivation-dependent pathways through hydroxyl-carboxylic acid receptor 2.

    PubMed

    Sun, Huawang; Li, Guo; Zhang, Wenjuan; Zhou, Qi; Yu, Yena; Shi, Ying; Offermanns, Stefan; Lu, Jianxin; Zhou, Naiming

    2014-01-01

    Niacin has been demonstrated to activate a PI3K/Akt signaling cascade to prevent brain damage after stroke and UV-induced skin damage; however, the underlying molecular mechanisms for HCA2-induced Akt activation remain to be elucidated. Using CHO-K1 cells stably expressing HCA2 and A431 cells, a human epidermoid cell line with high levels of endogenous expression of functional HCA2 receptors, we first demonstrated that niacin induced a robust Akt phosphorylation at both Thr308 and Ser473 in a time-dependent fashion, with a maximal activation at 5 min and a subsequent reduction to baseline by 30 min through HCA2, and that the activation was significantly blocked by pertussis toxin. The HCA2-mediated activation of Akt was also significantly inhibited by the PKC inhibitors GF109203x and Go6983 in both cell lines, by the PDGFR-selective inhibitor tyrphostin A9 in CHO-HCA2 cells and by the MMP inhibitor GM6001 and EGFR-specific inhibitor AG1478 in A431 cells. These results suggest that the PKC pathway and PDGFR/EGFR transactivation pathway play important roles in HCA2-mediated Akt activation. Further investigation indicated that PI3K and the Gβγ subunit were likely to play an essential role in HCA2-induced Akt activation. Moreover, Immunobloting analyses using an antibody that recognizes p70S6K1 phosphorylated at Thr389 showed that niacin evoked p70S6K1 activation via the PI3K/Akt pathway. The results of our study provide new insight into the signaling pathways involved in HCA2 activation.

  14. Human immunodeficiency virus trans-activator of transcription peptide detection via ribonucleic acid aptamer on aminated diamond biosensor

    NASA Astrophysics Data System (ADS)

    Rahim Ruslinda, A.; Wang, Xianfen; Ishii, Yoko; Ishiyama, Yuichiro; Tanabe, Kyosuke; Kawarada, Hiroshi

    2011-09-01

    The potential of ribonucleic acid (RNA) as both informational and ligand binding molecule have opened a scenario in the development of biosensors. An aminated diamond-based RNA aptasensor is presented for human immunodeficiency virus (HIV) trans-activator of transcription (Tat) peptide protein detection that not only gives a labeled or label-free detection method but also provides a reusable platform for a simple, sensitive, and selective detection of proteins. The immobilized procedure was based on the binding interaction between positively charged amine terminated diamond and the RNA aptamer probe molecules with the negatively charged surface carboxylic compound linker molecule such as terephthalic acid.

  15. Transactivation of the proenkephalin gene promoter by the Tax sub 1 protein of human T-cell lymphotropic virus type I

    SciTech Connect

    Joshi, J.B. ); Dave, H.P.G. )

    1992-02-01

    Human T-cell lymphotropic virus type I (HTLV-I), an etiologic agent for adult T-cell leukemia, is strongly associated with certain neurological diseases. The HTLV-I genome encodes a protein, Tax{sub 1}, that transactivates viral gene transcription. CD4-positive T helper lymphocytes express the proenkephalin gene, and enkephalins have been implicated as neuroimmunomodulators. The authors have investigated the effect of Tax{sub 1} on the proenkephalin gene promoter in C6 rat glioma cells and demonstrated its transactivation. Analysis using 5{prime} deletion mutants of the promoter region showed that sequences upstream of base pair - 190 are necessary for maximal transactivation. Forskolin, a cAMP modulator, synergistically increased Tax{sub 1}-mediated transactivation of the proenkephalin promoter. Neither Tax{sub 1} transactivation alone nor Tax{sub 1}/cAMP synergism exclusively involved cAMP-responsive elements. Endogenous proenkephalin gene expression increased in Tax{sub 1}-expressing C6 cells. Since HTLV-I infects lymphocytes, which express proenkephalin mRNA, Tax{sub 1} transregulation of proenkephalin expression may provide bidirectional communication between the nervous and immune systems in HTLV-I-related diseases.

  16. Interactions between human cyclin T, Tat, and the transactivation response element (TAR) are disrupted by a cysteine to tyrosine substitution found in mouse cyclin T

    PubMed Central

    Fujinaga, Koh; Taube, Ran; Wimmer, Jörg; Cujec, Thomas P.; Peterlin, B. Matija

    1999-01-01

    The transcriptional transactivator Tat from HIV binds to the transactivation response element (TAR) RNA to increase rates of elongation of viral transcription. Human cyclin T supports these interactions between Tat and TAR. In this study, we report the sequence of mouse cyclin T and identify the residues from positions 1 to 281 in human cyclin T that bind to Tat and TAR. Mouse cyclin T binds to Tat weakly and is unable to facilitate interactions between Tat and TAR. Reciprocal exchanges of the cysteine and tyrosine at position 261 in human and mouse cyclin T proteins also render human cyclin T inactive and mouse cyclin T active. These findings reveal the molecular basis for the restriction of Tat transactivation in rodent cells. PMID:9990016

  17. STAT3 and its phosphorylation are involved in HIV-1 Tat-induced transactivation of glial fibrillary acidic protein.

    PubMed

    Fan, Yan; Timani, Khalid Amine; He, Johnny J

    2015-01-01

    Human immunodeficiency virus type 1 (HIV-1) Tat protein is a major pathogenic factor in HIV-associated neurological diseases; it exhibits direct neurotoxicity and indirect astrocyte-mediated neurotoxicity. We have shown that Tat alone is capable of activating glial fibrillary acidic protein (GFAP) expression and inducing astrocytosis involving sequential activation of early growth response protein 1 (Egr-1) and p300. In this study, we determined the roles of signal transducer and activator of transcription 3 (STAT3) in Tat-induced GFAP transactivation. STAT3 expression and phosphorylation led to significant increases in GFAP transcription and protein expression. Tat expression was associated with increased STAT3 expression and phosphorylation in Tat-expressing astrocytes and HIV-infected astrocytes. GFAP, Egr-1 and p300 transcription and protein expression all showed positive response to STAT3 and its phosphorylation. Importantly, knockdown of STAT3 resulted in significant decreases in Tat-induced GFAP and Egr-1 transcription and protein expression. Taken together, these findings show that STAT3 is involved in and acts upstream of Egr1 and p300 in the Tat-induced GFAP transactivation cascade and suggest important roles of STAT3 in controlling astrocyte proliferation and activation in the HIV-infected central nervous system.

  18. HMGN2 inducibly binds a novel transactivation domain in nuclear PRLr to coordinate Stat5a-mediated transcription.

    PubMed

    Fiorillo, Alyson A; Medler, Terry R; Feeney, Yvonne B; Liu, Yi; Tommerdahl, Kalie L; Clevenger, Charles V

    2011-09-01

    The direct actions of transmembrane receptors within the nucleus remain enigmatic. In this report, we demonstrate that the prolactin receptor (PRLr) localizes to the nucleus where it functions as a coactivator through its interactions with the latent transcription factor signal transducer and activator of transcription 5a (Stat5a) and the high-mobility group N2 protein (HMGN2). We identify a novel transactivation domain within the PRLr that is activated by ligand-induced phosphorylation, an event coupled to HMGN2 binding. The association of the PRLr with HMGN2 enables Stat5a-responsive promoter binding, thus facilitating transcriptional activation and promoting anchorage-independent growth. We propose that HMGN2 serves as a critical regulatory factor in Stat5a-driven gene expression by facilitating the assembly of PRLr/Stat5a onto chromatin and that these events may serve to promote biological events that contribute to a tumorigenic phenotype. Our data imply that phosphorylation may be the molecular switch that activates a cell surface receptor transactivation domain, enabling it to tether chromatin-modifying factors, such as HMGN2, to target promoter regions in a sequence-specific manner.

  19. The nuclear cofactor RAC3/AIB1/SRC-3 enhances Nrf2 signaling by interacting with transactivation domains

    PubMed Central

    Kim, Jung-Hwan; Yu, Siwang; Chen, J. Don; Kong, A.-N. Tony

    2012-01-01

    Nuclear factor erythroid 2-related factor 2 (Nrf2, NM 006164, 605 AA) is essential for the antioxidant responsive element (ARE)-mediated expression of a group of detoxifying antioxidant genes that detoxify carcinogens and protect against oxidative stress. Several proteins have been identified as Nrf2-interacting molecules. In this study, we found that the overexpression of RAC3/AIB-1/SRC-3, a nuclear co-regulator and oncogene frequently amplified in human breast cancers, induced heme oxygenase-1 (HO-1) through Nrf2 transactivation in HeLa cells. Next, we determined the interaction between RAC3 and Nrf2 proteins using a co-immunoprecipitation assay (co-IP) and fluorescence resonance energy transfer (FRET) analysis. The results showed that RAC3 bound directly to the Nrf2 protein in the nucleus. Subsequently, we identified the interacting domains of Nrf2 and RAC3 using a GST pull-down assay. The results showed that both the N-terminal RAC3-pasB and C-terminal RAC3-R3B3 domains were tightly bound to the Neh4 and Neh5 transactivation domains. Furthermore, chromatin immunoprecipitation (ChIP) showed that RAC3 bound tightly to the ARE enhancer region of the HO-1 promoter via Nrf2 binding. These data suggest that Nrf2 activation is modulated and directly controlled through interactions with the RAC3 protein in HeLa cells. PMID:22370642

  20. Transactivation of ErbB receptors by leptin in the cardiovascular system: mechanisms, consequences and target for therapy.

    PubMed

    Bełtowski, Jerzy; Jazmroz-Wiśniewska, Anna

    2014-01-01

    Many experimental and clinical studies have demonstrated that elevated leptin concentration in patients with obesity/metabolic syndrome contributes to the pathogenesis of cardiovascular disorders including arterial hypertension, atherosclerosis, restenosis after coronary angioplasty and myocardial hypertrophy. Receptor tyrosine kinases belonging to the ErbB family, especially ErbB1 (epidermal growth factor receptor) and ErbB2 are abundantly expressed in the blood vessels and the heart. EGFR is activated not only by its multiple peptide ligands but also by many other factors including angiotensin II, endothelin-1, norepinephrine, thrombin and prorenin; the phenomenon referred to as "transactivation". Augmented EGFR signaling contributes to abnormalities of vascular tone and renal sodium handling as well as vascular remodeling and myocardial hypertrophy through various intracellular mechanisms, in particular extracellular signal-regulated kinases (ERK) and phosphoinositide 3-kinase (PI3K). Recent experimental studies indicate that chronically elevated leptin transactivates the EGFR through the mechanisms requiring reactive oxygen species and cytosolic tyrosine kinase, c-Src. In addition, hyperleptinemia increases ErbB2 activity in the arterial wall. Stimulation of EGFR and ErbB2 downstream signaling pathways such as ERK and PI3K in the vascular wall and the kidney may contribute to the increase in vascular tone, enhanced tubular sodium reabsorption as well as vascular and renal lesions in hyperleptinemic obese subjects.

  1. IDX-1: a new homeodomain transcription factor expressed in rat pancreatic islets and duodenum that transactivates the somatostatin gene.

    PubMed Central

    Miller, C P; McGehee, R E; Habener, J F

    1994-01-01

    We describe the cloning from a rat islet somatostatin-producing cell line of a 1.4 kb cDNA encoding a new homeoprotein, IDX-1 (islet/duodenum homeobox-1), with close sequence similarity to the Drosophila melanogaster homeobox protein Antennapedia (Antp) and the Xenopus laevis endoderm-specific homeoprotein XlHbox8. Analyses of IDX-1 mRNA and protein in rat tissues show that IDX-1 is expressed in pancreatic islets and ducts and in the duodenum. In electrophoretic mobility shift assays IDX-1 binds to three sites in the 5' flanking region of the rat somatostatin gene. In co-transfection experiments IDX-1 transactivates reporter constructs containing somatostatin promoter sequences, and mutation of the IDX-1 binding sites attenuates transactivation. Reverse transcription-polymerase chain reaction of islet RNA using degenerate amplimers for mRNAs encoding homeoproteins indicates that IDX-1 is the most abundant of 12 different Antp-like homeodomain mRNAs expressed in adult rat islets. The pattern of expression, relative abundance and transcriptional regulatory activity suggests that IDX-1 may be involved in the regulation of islet hormone genes and in cellular differentiation in the endocrine pancreas and the duodenum. Images PMID:7907546

  2. Characterization of ERM transactivation domain binding to the ACID/PTOV domain of the Mediator subunit MED25.

    PubMed

    Landrieu, Isabelle; Verger, Alexis; Baert, Jean-Luc; Rucktooa, Prakash; Cantrelle, François-Xavier; Dewitte, Frédérique; Ferreira, Elisabeth; Lens, Zoé; Villeret, Vincent; Monté, Didier

    2015-08-18

    The N-terminal acidic transactivation domain (TAD) of ERM/ETV5 (ERM38-68), a PEA3 group member of Ets-related transcription factors, directly interacts with the ACID/PTOV domain of the Mediator complex subunit MED25. Molecular details of this interaction were investigated using nuclear magnetic resonance (NMR) spectroscopy. The TAD is disordered in solution but has a propensity to adopt local transient secondary structure. We show that it folds upon binding to MED25 and that the resulting ERM-MED25 complex displays characteristics of a fuzzy complex. Mutational analysis further reveals that two aromatic residues in the ERM TAD (F47 and W57) are involved in the binding to MED25 and participate in the ability of ERM TAD to activate transcription. Mutation of a key residue Q451 in the VP16 H1 binding pocket of MED25 affects the binding of ERM. Furthermore, competition experiments show that ERM and VP16 H1 share a common binding interface on MED25. NMR data confirms the occupancy of this binding pocket by ERM TAD. Based on these experimental data, a structural model of a functional interaction is proposed. This study provides mechanistic insights into the Mediator-transactivator interactions. PMID:26130716

  3. Characterization of ERM transactivation domain binding to the ACID/PTOV domain of the Mediator subunit MED25

    PubMed Central

    Landrieu, Isabelle; Verger, Alexis; Baert, Jean-Luc; Rucktooa, Prakash; Cantrelle, François-Xavier; Dewitte, Frédérique; Ferreira, Elisabeth; Lens, Zoé; Villeret, Vincent; Monté, Didier

    2015-01-01

    The N-terminal acidic transactivation domain (TAD) of ERM/ETV5 (ERM38–68), a PEA3 group member of Ets-related transcription factors, directly interacts with the ACID/PTOV domain of the Mediator complex subunit MED25. Molecular details of this interaction were investigated using nuclear magnetic resonance (NMR) spectroscopy. The TAD is disordered in solution but has a propensity to adopt local transient secondary structure. We show that it folds upon binding to MED25 and that the resulting ERM–MED25 complex displays characteristics of a fuzzy complex. Mutational analysis further reveals that two aromatic residues in the ERM TAD (F47 and W57) are involved in the binding to MED25 and participate in the ability of ERM TAD to activate transcription. Mutation of a key residue Q451 in the VP16 H1 binding pocket of MED25 affects the binding of ERM. Furthermore, competition experiments show that ERM and VP16 H1 share a common binding interface on MED25. NMR data confirms the occupancy of this binding pocket by ERM TAD. Based on these experimental data, a structural model of a functional interaction is proposed. This study provides mechanistic insights into the Mediator–transactivator interactions. PMID:26130716

  4. Low levels of the reverse transactivator fail to induce target transgene expression in vascular smooth muscle cells.

    PubMed

    Viceconte, Nikenza; McKenna, Tomás; Eriksson, Maria

    2014-01-01

    Hutchinson-Gilford progeria syndrome (HGPS) is a genetic disease with multiple features that are suggestive of premature aging. Most patients with HGPS carry a mutation on one of their copies of the LMNA gene. The LMNA gene encodes the lamin A and lamin C proteins, which are the major proteins of the nuclear lamina. The organs of the cardiovascular system are amongst those that are most severely affected in HGPS, undergoing a progressive depletion of vascular smooth muscle cells, and most children with HGPS die in their early teens from cardio-vascular disease and other complications from atherosclerosis. In this study, we developed a transgenic mouse model based on the tet-ON system to increase the understanding of the molecular mechanisms leading to the most lethal aspect of HGPS. To induce the expression of the most common HGPS mutation, LMNA c.1824C>T; p.G608G, in the vascular smooth muscle cells of the aortic arch and thoracic aorta, we used the previously described reverse tetracycline-controlled transactivator, sm22α-rtTA. However, the expression of the reverse sm22α-transactivator was barely detectable in the arteries, and this low level of expression was not sufficient to induce the expression of the target human lamin A minigene. The results from this study are important because they suggest caution during the use of previously functional transgenic animal models and emphasize the importance of assessing transgene expression over time.

  5. Technical advance: An estrogen receptor-based transactivator XVE mediates highly inducible gene expression in transgenic plants.

    PubMed

    Zuo, J; Niu, Q W; Chua, N H

    2000-10-01

    We have developed an estrogen receptor-based chemical-inducible system for use in transgenic plants. A chimeric transcription activator, XVE, was assembled by fusion of the DNA-binding domain of the bacterial repressor LexA (X), the acidic transactivating domain of VP16 (V) and the regulatory region of the human estrogen receptor (E; ER). The transactivating activity of the chimeric XVE factor, whose expression was controlled by the strong constitutive promoter G10-90, was strictly regulated by estrogens. In transgenic Arabidopsis and tobacco plants, estradiol-activated XVE can stimulate expression of a GFP reporter gene controlled by the target promoter, which consists of eight copies of the LexA operator fused upstream of the -46 35S minimal promoter. Upon induction by estradiol, GFP expression levels can be eightfold higher than that transcribed from a 35S promoter, whereas the uninduced controls have no detectable GFP transcripts, as monitored by Northern blot analysis. Neither toxic nor adverse physiological effects of the XVE system have been observed in transgenic Arabidopsis plants under all the conditions tested. The XVE system thus appears to be a reliable and efficient chemical-inducible system for regulating transgene expression in plants.

  6. A phosphorylation site located in the NH2-terminal domain of c-Myc increases transactivation of gene expression.

    PubMed

    Seth, A; Alvarez, E; Gupta, S; Davis, R J

    1991-12-15

    The c-myc gene encodes a sequence-specific DNA-binding protein (c-Myc) that forms leucine zipper complexes and can act as a transcription factor. Growth factor stimulation of cells causes the phosphorylation of the c-Myc transcriptional activation domain at Ser62 within a proline-rich region that is highly conserved among members of the Myc family (Alvarez, E., Northwood, I.C., Gonzalez, F. A., Latour, D. A., Seth, A., Abate, C., Curran, T., and Davis, R. J. (1991) J. Biol. Chem. 266, 15277-15285). This phosphorylation site is a substrate for growth factor-regulated MAP kinases and for the cell cycle-dependent protein kinase p34cdc2. We report that serum treatment of cells results in a marked increase in the transactivation of gene expression mediated by the c-Myc transcriptional activation domain. A point mutation at the site of growth factor-stimulated phosphorylation (Ser62) decreases the serum induction of transactivation. These data indicate that the c-Myc transcriptional activation domain may be a direct target of signal transduction pathways. PMID:1748630

  7. Transactivation domains facilitate promoter occupancy for the dioxin-inducible CYP1A1 gene in vivo.

    PubMed Central

    Ko, H P; Okino, S T; Ma, Q; Whitlock, J P

    1997-01-01

    We have studied the transcriptional regulation of the dioxin-inducible mouse CYP1A1 gene in its native chromosomal setting. We analyzed the ability of aromatic hydrocarbon receptor (AhR) mutants and AhR chimeras to restore dioxin responsiveness to the CYP1A1 gene in AhR-defective mouse hepatoma cells. Our data reveal that transactivation domains in AhR's C-terminal half mediate occupancy of the nuclear factor 1 site and TATA box for the CYP1A1 promoter in vivo. Transactivation domains of VP16 and AhR nuclear translocator, but not Sp1, can substitute for AhR's C-terminal half in facilitating protein binding at the promoter. Our data also reveal an apparent linear relationship between promoter occupancy and CYP1A1 gene expression in chromatin. These findings provide new insights into the in vivo mechanism of transcriptional activation for an interesting mammalian gene. PMID:9199285

  8. Activation of human papillomavirus type 18 gene expression by herpes simplex virus type 1 viral transactivators and a phorbol ester

    SciTech Connect

    Gius, D.; Laimins, L.A.

    1989-02-01

    Several viral trans-activators and a tumor promoter were examined for the ability to activate human papillomavirus type 18 (HPV-18) gene expression. A plasmid containing the HPV-18 noncoding region placed upstream of the chloramphenicol acetyltransferase reporter gene was cotransfected with different herpes simplex virus type 1 (HSV-1) genes into several cell lines. Both HSV-1 TIF and ICPO activated HPV-18 expression; however, activation by TIF was observed only in epithelial cells, while ICPO stimulated expression in a wide variety of cells. The element activated by both TIF and ICOP was mapped to a 229-base-pair fragment which also contains an HPV-18 epithelial cell-preferred enhancer. The inclusion of a papillomavirus E2 trans-activator with TIF and ICOP further increased HPV-18 expression. In contrast, the HSV-1 ICP4 and ICP27 genes, as well as the human T-cell lymphotropic virus type I and human immunodeficiency virus type 1 tat genes, were found to have no effect on HPV-18 expression. In transient assays, the addition of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) also activated HPV-18 expression. The region of HPV-18 activated by TPA was localized to a sequence which is homologous to other TPA-responsive elements.

  9. A Lactobacillus rhamnosus GG-derived soluble protein, p40, stimulates ligand release from intestinal epithelial cells to transactivate epidermal growth factor receptor.

    PubMed

    Yan, Fang; Liu, Liping; Dempsey, Peter J; Tsai, Yu-Hwai; Raines, Elaine W; Wilson, Carole L; Cao, Hailong; Cao, Zheng; Liu, LinShu; Polk, D Brent

    2013-10-18

    p40, a Lactobacillus rhamnosus GG (LGG)-derived soluble protein, ameliorates intestinal injury and colitis, reduces apoptosis, and preserves barrier function by transactivation of the EGF receptor (EGFR) in intestinal epithelial cells. The aim of this study is to determine the mechanisms by which p40 transactivates the EGFR in intestinal epithelial cells. Here we show that p40-conditioned medium activates EGFR in young adult mouse colon epithelial cells and human colonic epithelial cell line, T84 cells. p40 up-regulates a disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) catalytic activity, and broad spectrum metalloproteinase inhibitors block EGFR transactivation by p40 in these two cell lines. In ADAM17-deficient mouse colonic epithelial (ADAM17(-/-) MCE) cells, p40 transactivation of EGFR is blocked, but can be rescued by re-expression with WT ADAM17. Furthermore, p40 stimulates release of heparin binding (HB)-EGF, but not transforming growth factor (TGF)α or amphiregulin, in young adult mouse colon cells and ADAM17(-/-) MCE cells overexpressing WT ADAM17. Knockdown of HB-EGF expression by siRNA suppresses p40 effects on transactivating EGFR and Akt, preventing apoptosis, and preserving tight junction function. The effects of p40 on HB-EGF release and ADAM17 activation in vivo are examined after administration of p40-containing pectin/zein hydrogel beads to mice. p40 stimulates ADAM17 activity and EGFR activation in colonic epithelial cells and increases HB-EGF levels in blood from WT mice, but not from mice with intestinal epithelial cell-specific ADAM17 deletion. Thus, these data define a mechanism of a probiotic-derived soluble protein in modulating intestinal epithelial cell homeostasis through ADAM17-mediated HB-EGF release, leading to transactivation of EGFR.

  10. A Lactobacillus rhamnosus GG-derived Soluble Protein, p40, Stimulates Ligand Release from Intestinal Epithelial Cells to Transactivate Epidermal Growth Factor Receptor*

    PubMed Central

    Yan, Fang; Liu, Liping; Dempsey, Peter J.; Tsai, Yu-Hwai; Raines, Elaine W.; Wilson, Carole L.; Cao, Hailong; Cao, Zheng; Liu, LinShu; Polk, D. Brent

    2013-01-01

    p40, a Lactobacillus rhamnosus GG (LGG)-derived soluble protein, ameliorates intestinal injury and colitis, reduces apoptosis, and preserves barrier function by transactivation of the EGF receptor (EGFR) in intestinal epithelial cells. The aim of this study is to determine the mechanisms by which p40 transactivates the EGFR in intestinal epithelial cells. Here we show that p40-conditioned medium activates EGFR in young adult mouse colon epithelial cells and human colonic epithelial cell line, T84 cells. p40 up-regulates a disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) catalytic activity, and broad spectrum metalloproteinase inhibitors block EGFR transactivation by p40 in these two cell lines. In ADAM17-deficient mouse colonic epithelial (ADAM17−/− MCE) cells, p40 transactivation of EGFR is blocked, but can be rescued by re-expression with WT ADAM17. Furthermore, p40 stimulates release of heparin binding (HB)-EGF, but not transforming growth factor (TGF)α or amphiregulin, in young adult mouse colon cells and ADAM17−/− MCE cells overexpressing WT ADAM17. Knockdown of HB-EGF expression by siRNA suppresses p40 effects on transactivating EGFR and Akt, preventing apoptosis, and preserving tight junction function. The effects of p40 on HB-EGF release and ADAM17 activation in vivo are examined after administration of p40-containing pectin/zein hydrogel beads to mice. p40 stimulates ADAM17 activity and EGFR activation in colonic epithelial cells and increases HB-EGF levels in blood from WT mice, but not from mice with intestinal epithelial cell-specific ADAM17 deletion. Thus, these data define a mechanism of a probiotic-derived soluble protein in modulating intestinal epithelial cell homeostasis through ADAM17-mediated HB-EGF release, leading to transactivation of EGFR. PMID:24043629

  11. Inhibition of the FACT Complex Reduces Transcription from the Human Cytomegalovirus Major Immediate Early Promoter in Models of Lytic and Latent Replication.

    PubMed

    O'Connor, Christine M; Nukui, Masatoshi; Gurova, Katerina V; Murphy, Eain A

    2016-04-01

    The successful colonization of the majority of the population by human cytomegalovirus is a direct result of the virus's ability to establish and, more specifically, reactivate from latency. The underlying cellular factors involved in viral reactivation remain unknown. Here, we show that the host complexfacilitateschromatintranscription (FACT) binds to the major immediate early promoter (MIEP) and that inhibition of this complex reduces MIEP transactivation, thus inhibiting viral reactivation. PMID:26865717

  12. Transactivation Assays to Assess Canine and Rodent Pregnane X Receptor (PXR) and Constitutive Androstane Receptor (CAR) Activation

    PubMed Central

    Pinne, Marija; Ponce, Elsa; Raucy, Judy L.

    2016-01-01

    The pregnane X receptor (PXR/SXR, NR1I2) and constitutive androstane receptor (CAR, NR1I3) are nuclear receptors (NRs) involved in the regulation of many genes including cytochrome P450 enzymes (CYPs) and transporters important in metabolism and uptake of both endogenous substrates and xenobiotics. Activation of these receptors can lead to adverse drug effects as well as drug-drug interactions. Depending on which nuclear receptor is activated will determine which adverse effect could occur, making identification important. Screening for NR activation by New Molecular Entities (NMEs) using cell-based transactivation assays is the singular high throughput method currently available for identifying the activation of a particular NR. Moreover, screening for species-specific NR activation can minimize the use of animals in drug development and toxicology studies. With this in mind, we have developed in vitro transactivation assays to identify compounds that activate canine and rat PXR and CAR3. We found differences in specificity for canine and rat PXR, with the best activator for canine PXR being 10 μM SR12813 (60.1 ± 3.1-fold) and for rat PXR, 10 μM dexamethasone (60.9 ± 8.4 fold). Of the 19 test agents examined, 10 and 9 significantly activated rat and canine PXR at varying degrees, respectively. In contrast, 5 compounds exhibited statistically significant activation of rat CAR3 and 4 activated the canine receptor. For canine CAR3, 50 μM artemisinin proved to be the best activator (7.3 ± 1.8 and 10.5 ± 2.2 fold) while clotrimazole (10 μM) was the primary activator of the rat variant (13.7 ± 0.8 and 26.9 ± 1.3 fold). Results from these studies demonstrated that cell-based transactivation assays can detect species-specific activators and revealed that PXR was activated by at least twice as many compounds as was CAR3, suggesting that there are many more agonists for PXR than CAR. PMID:27732639

  13. The hepatitis B virus X protein increases the cellular level of TATA-binding protein, which mediates transactivation of RNA polymerase III genes

    SciTech Connect

    Wang, Horng-Dar; Johnson, D.L.; Yuh, Chio-Hwa

    1995-12-01

    This report decribes the mechanism by which the hepatitis B virus X gene product induces RNA polymerase III genes. The RNA pol III transcription system serves as model for understanding the mechanism of X in the transactivation of cellular genes in both Drosophila and rat cell lines. 53 refs., 7 figs., 1 tab.

  14. The Myc Transactivation Domain Promotes Global Phosphorylation of the RNA Polymerase II Carboxy-Terminal Domain Independently of Direct DNA Binding▿ †

    PubMed Central

    Cowling, Victoria H.; Cole, Michael D.

    2007-01-01

    Myc is a transcription factor which is dependent on its DNA binding domain for transcriptional regulation of target genes. Here, we report the surprising finding that Myc mutants devoid of direct DNA binding activity and Myc target gene regulation can rescue a substantial fraction of the growth defect in myc−/− fibroblasts. Expression of the Myc transactivation domain alone induces a transcription-independent elevation of the RNA polymerase II (Pol II) C-terminal domain (CTD) kinases cyclin-dependent kinase 7 (CDK7) and CDK9 and a global increase in CTD phosphorylation. The Myc transactivation domain binds to the transcription initiation sites of these promoters and stimulates TFIIH binding in an MBII-dependent manner. Expression of the Myc transactivation domain increases CDK mRNA cap methylation, polysome loading, and the rate of translation. We find that some traditional Myc transcriptional target genes are also regulated by this Myc-driven translation mechanism. We propose that Myc transactivation domain-driven RNA Pol II CTD phosphorylation has broad effects on both transcription and mRNA metabolism. PMID:17242204

  15. Phenotypic Complementation Establishes Requirements for Specific POU Domain and Generic Transactivation Function of Oct-3/4 in Embryonic Stem Cells

    PubMed Central

    Niwa, Hitoshi; Masui, Shinji; Chambers, Ian; Smith, Austin G.; Miyazaki, Jun-ichi

    2002-01-01

    Transcription factors of the POU family govern cell fate through combinatorial interactions with coactivators and corepressors. The POU factor Oct-3/4 can define differentiation, dedifferentation, or self-renewal of pluripotent embryonic stem (ES) cells in a sensitive, dose-dependent manner (H. Niwa, J.-I. Miyazali, and A. G. Smith, Nat. Genet. 24:372-376, 2000). Here we have developed a complementation assay based on the ability of Oct-3/4 transgenes to rescue self-renewal in conditionally null ES cells and used this to define which domains of Oct-3/4 are required to sustain the undifferentiated stem cell phenotype. Surprisingly, we found that molecules lacking either the N-terminal or C-terminal transactivation domain, though not both, can effectively replace full-length Oct-3/4. Furthermore, a fusion of the heterologous transactivation domain of Oct-2 to the Oct-3/4 POU domain can also sustain self-renewal. Thus, the unique function of Oct-3/4 in ES cell propagation resides in combination of the specific POU domain with a generic proline-rich transactivation domain. Interestingly, however, Oct-3/4 target gene expression elicited by the N- and C-terminal transactivation domains is not identical, indicating that at least one class of genes activated by Oct-3/4 is not required for ES cell propagation. PMID:11839818

  16. Epidermal Growth Factor Receptor Transactivation Is Required for Mitogen-Activated Protein Kinase Activation by Muscarinic Acetylcholine Receptors in HaCaT Keratinocytes

    PubMed Central

    Ockenga, Wymke; Kühne, Sina; Bocksberger, Simone; Banning, Antje; Tikkanen, Ritva

    2014-01-01

    Non-neuronal acetylcholine plays a substantial role in the human skin by influencing adhesion, migration, proliferation and differentiation of keratinocytes. These processes are regulated by the Mitogen-Activated Protein (MAP) kinase cascade. Here we show that in HaCaT keratinocytes all five muscarinic receptor subtypes are expressed, but M1 and M3 are the subtypes involved in mitogenic signaling. Stimulation with the cholinergic agonist carbachol leads to activation of the MAP kinase extracellular signal regulated kinase, together with the protein kinase Akt. The activation is fully dependent on the transactivation of the epidermal growth factor receptor (EGFR), which even appears to be the sole pathway for the muscarinic receptors to facilitate MAP kinase activation in HaCaT cells. The transactivation pathway involves a triple-membrane-passing process, based on activation of matrix metalloproteases, and extracellular ligand release; whereas phosphatidylinositol 3-kinase, Src family kinases or protein kinase C do not appear to be involved in MAP kinase activation. Furthermore, phosphorylation, ubiquitination and endocytosis of the EGF receptor after cholinergic transactivation are different from that induced by a direct stimulation with EGF, suggesting that ligands other than EGF itself mediate the cholinergic transactivation. PMID:25421240

  17. Epidermal growth factor/TNF-α transactivation modulates epithelial cell proliferation and apoptosis in a mouse model of parenteral nutrition

    PubMed Central

    Feng, Yongjia

    2012-01-01

    Epidermal growth factor (EGF) and tumor necrosis factor-α (TNF-α) signaling are critical for effective proliferative and apoptotic actions; however, little is known about the codependency of these signaling pathways in the intestinal epithelium. Because total parenteral nutrition (TPN) is associated with loss of intestinal epithelial cell (IEC) proliferation and increased apoptosis, we utilized a mouse model to explore these transactivation pathways in small bowel epithelium. Mice underwent intravenous cannulation and were given enteral nutrition or TPN for 7 days. Outcomes included IEC proliferation, apoptosis, and survival. To address transactivation or dependence of EGF and TNF on IEC physiology, TNF-α receptor knockout (KO) mice, TNFR1-KO, R2-KO, or R1R2-double KO, were used. Exogenous EGF and pharmacological blockade of ErbB1 were performed in other groups to examine the relevance of the ErB1 pathway. TPN increased IEC TNFR1 and decreased EGF and ErbB1 abundance. Loss of IEC proliferation was prevented by exogenous EGF or blockade of TNFR1. However, EGF action was prevented without effective TNFR2 signaling. Also, blockade of TNFR1 could not prevent loss of IEC proliferation without effective ErbB1 signaling. TPN increased IEC apoptosis and was due to increased TNFR1 signaling. Exogenous EGF or blockade of TNFR1 could prevent increased apoptosis, and both pathways were dependent on effective ErbB1 signaling. Exogenous EGF prevented increased apoptosis in mice lacking TNFR2 signaling. TPN mice had significantly decreased survival vs. controls, and this was associated with the TNFR1 signaling pathway. We concluded that these findings identify critical mechanisms that contribute to TPN-associated mucosal atrophy via altered TNF-α/EGF signaling. It emphasizes the importance of both TNFR1 and TNFR2 pathways, as well as the strong interdependence on an intact EGF/ErbB1 pathway. PMID:22075779

  18. The EBNA-2 N-Terminal Transactivation Domain Folds into a Dimeric Structure Required for Target Gene Activation

    PubMed Central

    Hennig, Janosch; Zou, Peijian; Nössner, Elfriede; Ling, Paul D.; Sattler, Michael; Kempkes, Bettina

    2015-01-01

    Epstein-Barr virus (EBV) is a γ-herpesvirus that may cause infectious mononucleosis in young adults. In addition, epidemiological and molecular evidence links EBV to the pathogenesis of lymphoid and epithelial malignancies. EBV has the unique ability to transform resting B cells into permanently proliferating, latently infected lymphoblastoid cell lines. Epstein-Barr virus nuclear antigen 2 (EBNA-2) is a key regulator of viral and cellular gene expression for this transformation process. The N-terminal region of EBNA-2 comprising residues 1-58 appears to mediate multiple molecular functions including self-association and transactivation. However, it remains to be determined if the N-terminus of EBNA-2 directly provides these functions or if these activities merely depend on the dimerization involving the N-terminal domain. To address this issue, we determined the three-dimensional structure of the EBNA-2 N-terminal dimerization (END) domain by heteronuclear NMR-spectroscopy. The END domain monomer comprises a small fold of four β-strands and an α-helix which form a parallel dimer by interaction of two β-strands from each protomer. A structure-guided mutational analysis showed that hydrophobic residues in the dimer interface are required for self-association in vitro. Importantly, these interface mutants also displayed severely impaired self-association and transactivation in vivo. Moreover, mutations of solvent-exposed residues or deletion of the α-helix do not impair dimerization but strongly affect the functional activity, suggesting that the EBNA-2 dimer presents a surface that mediates functionally important intra- and/or intermolecular interactions. Our study shows that the END domain is a novel dimerization fold that is essential for functional activity. Since this specific fold is a unique feature of EBNA-2 it might provide a novel target for anti-viral therapeutics. PMID:26024477

  19. The viral transactivator HBx protein exhibits a high potential for regulation via phosphorylation through an evolutionarily conserved mechanism

    PubMed Central

    2012-01-01

    Background Hepatitis B virus (HBV) encodes an oncogenic factor, HBx, which is a multifunctional protein that can induce dysfunctional regulation of signaling pathways, transcription, and cell cycle progression, among other processes, through interactions with target host factors. The subcellular localization of HBx is both cytoplasmic and nuclear. This dynamic distribution of HBx could be essential to the multiple roles of the protein at different stages during HBV infection. Transactivational functions of HBx may be exerted both in the nucleus, via interaction with host DNA-binding proteins, and in the cytoplasm, via signaling pathways. Although there have been many studies describing different pathways altered by HBx, and its innumerable binding partners, the molecular mechanism that regulates its different roles has been difficult to elucidate. Methods In the current study, we took a bioinformatics approach to investigate whether the viral protein HBx might be regulated via phosphorylation by an evolutionarily conserved mechanism. Results We found that the phylogenetically conserved residues Ser25 and Ser41 (both within the negative regulatory domain), and Thr81 (in the transactivation domain) are predicted to be phosphorylated. By molecular 3D modeling of HBx, we further show these residues are all predicted to be exposed on the surface of the protein, making them easily accesible to these types of modifications. Furthermore, we have also identified Yin Yang sites that might have the potential to be phosphorylated and O-β-GlcNAc interplay at the same residues. Conclusions Thus, we propose that the different roles of HBx displayed in different subcellular locations might be regulated by an evolutionarily conserved mechanism of posttranslational modification, via phosphorylation. PMID:23079056

  20. Integrin-mediated transactivation of P2X7R via hemichannel-dependent ATP release stimulates astrocyte migration.

    PubMed

    Alvarez, Alvaro; Lagos-Cabré, Raúl; Kong, Milene; Cárdenas, Areli; Burgos-Bravo, Francesca; Schneider, Pascal; Quest, Andrew F G; Leyton, Lisette

    2016-09-01

    Our previous reports indicate that ligand-induced αVβ3 integrin and Syndecan-4 engagement increases focal adhesion formation and migration of astrocytes. Additionally, ligated integrins trigger ATP release through unknown mechanisms, activating P2X7 receptors (P2X7R), and the uptake of Ca(2+) to promote cell adhesion. However, whether the activation of P2X7R and ATP release are required for astrocyte migration and whether αVβ3 integrin and Syndecan-4 receptors communicate with P2X7R via ATP remains unknown. Here, cells were stimulated with Thy-1, a reported αVβ3 integrin and Syndecan-4 ligand. Results obtained indicate that ATP was released by Thy-1 upon integrin engagement and required the participation of phosphatidylinositol-3-kinase (PI3K), phospholipase-C gamma (PLCγ) and inositol trisphosphate (IP3) receptors (IP3R). IP3R activation leads to increased intracellular Ca(2+), hemichannel (Connexin-43 and Pannexin-1) opening, and ATP release. Moreover, silencing of the P2X7R or addition of hemichannel blockers precluded Thy-1-induced astrocyte migration. Finally, Thy-1 lacking the integrin-binding site did not stimulate ATP release, whereas Thy-1 mutated in the Syndecan-4-binding domain increased ATP release, albeit to a lesser extent and with delayed kinetics compared to wild-type Thy-1. Thus, hemichannels activated downstream of an αVβ3 integrin-PI3K-PLCγ-IP3R pathway are responsible for Thy-1-induced, hemichannel-mediated and Syndecan-4-modulated ATP release that transactivates P2X7Rs to induce Ca(2+) entry. These findings uncover a hitherto unrecognized role for hemichannels in the regulation of astrocyte migration via P2X7R transactivation induced by integrin-mediated ATP release.

  1. EGFR trans-activation by urotensin II receptor is mediated by β-arrestin recruitment and confers cardioprotection in pressure overload-induced cardiac hypertrophy.

    PubMed

    Esposito, Giovanni; Perrino, Cinzia; Cannavo, Alessandro; Schiattarella, Gabriele G; Borgia, Francesco; Sannino, Anna; Pironti, Gianluigi; Gargiulo, Giuseppe; Di Serafino, Luigi; Franzone, Anna; Scudiero, Laura; Grieco, Paolo; Indolfi, Ciro; Chiariello, Massimo

    2011-06-01

    Urotensin II (UTII) and its seven trans-membrane receptor (UTR) are up-regulated in the heart under pathological conditions. Previous in vitro studies have shown that UTII trans-activates the epidermal growth factor receptor (EGFR), however, the role of such novel signalling pathway stimulated by UTII is currently unknown. In this study, we hypothesized that EGFR trans-activation by UTII might exert a protective effect in the overloaded heart. To test this hypothesis, we induced cardiac hypertrophy by transverse aortic constriction (TAC) in wild-type mice, and tested the effects of the UTII antagonist Urantide (UR) on cardiac function, structure, and EGFR trans-activation. After 7 days of pressure overload, UR treatment induced a rapid and significant impairment of cardiac function compared to vehicle. In UR-treated TAC mice, cardiac dysfunction was associated with reduced phosphorylation levels of the EGFR and extracellular-regulated kinase (ERK), increased apoptotic cell death and fibrosis. In vitro UTR stimulation induced membrane translocation of β-arrestin 1/2, EGFR phosphorylation/internalization, and ERK activation in HEK293 cells. Furthermore, UTII administration lowered apoptotic cell death induced by serum deprivation, as shown by reduced TUNEL/Annexin V staining and caspase 3 activation. Interestingly, UTII-mediated EGFR trans-activation could be prevented by UR treatment or knockdown of β-arrestin 1/2. Our data show, for the first time in vivo, a new UTR signalling pathway which is mediated by EGFR trans-activation, dependent by β-arrestin 1/2, promoting cell survival and cardioprotection.

  2. Trans-activation function of a 3 prime truncated X gene-cell fusion product from integrated hepatitis B virus DNA in chronic hepatitis tissues

    SciTech Connect

    Takada, Shinako; Koike, Katsuro )

    1990-08-01

    To investigate the expression and transactivation function of the X gene in integrated hepatitis B virus (HBV) DNA from chronic hepatitis tissues, a series of transfectants containing cloned integrated HBV DNAs was made and analyzed for X mRNA expression and trans-activation activity by using a chloramphenicol acetyltransferase assay. Most of the integrated HBV DNAs expressed X mRNA and encoded a product with trans-activation activity in spite of the loss of the 3{prime} end region of the X gene due to integration. From cDNA cloning and sequence analysis of X mRNA transcribed from native or integrated HBV DNA, the X protein was found to be translated from the X open reading frame without splicing. For integrated HBV DNA, transcription was extended to a cellular flanking DNA and an X gene-cell fusion transcript was terminated by using a cellular poly(A) signal. The amino acid sequence deduced from an X-cell fusion transcript indicated truncation of the carboxyl-terminal five amino acids, but the upstream region of seven amino acids conserved among hepadnaviruses was retained in the integrated HBV DNA, suggesting that this conserved region is essential for the transactivation function of the X protein. These findings support the following explanation for hepatocarcinogenesis by HBV DNA integration: the expression of a cellular oncogene(s) is transactivated at the time of chronic infection by the increasing amounts of the integrated HBV gene product(s), such as the X-cell fusion product.

  3. Potent inhibition of HIV-1 replication by a Tat mutant.

    PubMed

    Meredith, Luke W; Sivakumaran, Haran; Major, Lee; Suhrbier, Andreas; Harrich, David

    2009-11-10

    Herein we describe a mutant of the two-exon HIV-1 Tat protein, termed Nullbasic, that potently inhibits multiple steps of the HIV-1 replication cycle. Nullbasic was created by replacing the entire arginine-rich basic domain of wild type Tat with glycine/alanine residues. Like similarly mutated one-exon Tat mutants, Nullbasic exhibited transdominant negative effects on Tat-dependent transactivation. However, unlike previously reported mutants, we discovered that Nullbasic also strongly suppressed the expression of unspliced and singly-spliced viral mRNA, an activity likely caused by redistribution and thus functional inhibition of HIV-1 Rev. Furthermore, HIV-1 virion particles produced by cells expressing Nullbasic had severely reduced infectivity, a defect attributable to a reduced ability of the virions to undergo reverse transcription. Combination of these inhibitory effects on transactivation, Rev-dependent mRNA transport and reverse transcription meant that permissive cells constitutively expressing Nullbasic were highly resistant to a spreading infection by HIV-1. Nullbasic and its activities thus provide potential insights into the development of potent antiviral therapeutics that target multiple stages of HIV-1 infection.

  4. Pumpkin seed extract: Cell growth inhibition of hyperplastic and cancer cells, independent of steroid hormone receptors.

    PubMed

    Medjakovic, Svjetlana; Hobiger, Stefanie; Ardjomand-Woelkart, Karin; Bucar, Franz; Jungbauer, Alois

    2016-04-01

    Pumpkin seeds have been known in folk medicine as remedy for kidney, bladder and prostate disorders since centuries. Nevertheless, pumpkin research provides insufficient data to back up traditional beliefs of ethnomedical practice. The bioactivity of a hydro-ethanolic extract of pumpkin seeds from the Styrian pumpkin, Cucurbita pepo L. subsp. pepo var. styriaca, was investigated. As pumpkin seed extracts are standardized to cucurbitin, this compound was also tested. Transactivational activity was evaluated for human androgen receptor, estrogen receptor and progesterone receptor with in vitro yeast assays. Cell viability tests with prostate cancer cells, breast cancer cells, colorectal adenocarcinoma cells and a hyperplastic cell line from benign prostate hyperplasia tissue were performed. As model for non-hyperplastic cells, effects on cell viability were tested with a human dermal fibroblast cell line (HDF-5). No transactivational activity was found for human androgen receptor, estrogen receptor and progesterone receptor, for both, extract and cucurbitin. A cell growth inhibition of ~40-50% was observed for all cell lines, with the exception of HDF-5, which showed with ~20% much lower cell growth inhibition. Given the receptor status of some cell lines, a steroid-hormone receptor independent growth inhibiting effect can be assumed. The cell growth inhibition for fast growing cells together with the cell growth inhibition of prostate-, breast- and colon cancer cells corroborates the ethnomedical use of pumpkin seeds for a treatment of benign prostate hyperplasia. Moreover, due to the lack of androgenic activity, pumpkin seed applications can be regarded as safe for the prostate.

  5. Role of conserved intracellular motifs in Serrate signalling, cis-inhibition and endocytosis

    PubMed Central

    Glittenberg, Marcus; Pitsouli, Chrysoula; Garvey, Clare; Delidakis, Christos; Bray, Sarah

    2006-01-01

    Notch is the receptor in a signalling pathway that operates in a diverse spectrum of developmental processes. Its ligands (e.g. Serrate) are transmembrane proteins whose signalling competence is regulated by the endocytosis-promoting E3 ubiquitin ligases, Mindbomb1 and Neuralized. The ligands also inhibit Notch present in the same cell (cis-inhibition). Here, we identify two conserved motifs in the intracellular domain of Serrate that are required for efficient endocytosis. The first, a dileucine motif, is dispensable for trans-activation and cis-inhibition despite the endocytic defect, demonstrating that signalling can be separated from bulk endocytosis. The second, a novel motif, is necessary for interactions with Mindbomb1/Neuralized and is strictly required for Serrate to trans-activate and internalise efficiently but not for it to inhibit Notch signalling. Cis-inhibition is compromised when an ER retention signal is added to Serrate, or when the levels of Neuralized are increased, and together these data indicate that cis-inhibitory interactions occur at the cell surface. The balance of ubiquitinated/unubiquitinated ligand will thus affect the signalling capacity of the cell at several levels. PMID:17006545

  6. Myocardin-related transcription factor A is up-regulated by 17β-estradiol and promotes migration of MCF-7 breast cancer cells via transactivation of MYL9 and CYR61.

    PubMed

    Zhang, Chunling; Luo, Xuegang; Liu, Lei; Guo, Shu; Zhao, Wenwen; Mu, Ai; Liu, Zhipeng; Wang, Nan; Zhou, Hao; Zhang, Tongcun

    2013-11-01

    Many lines of evidence have suggested that estrogen plays important roles not only in the initiation and proliferation of breast cancer, but also in cancer metastasis. However, the mechanistic basis of the latter events is poorly understood. In addition, recent studies have suggested that myocardin-related transcription factor A (MRTF-A) might be related to cancer metastasis. However, as reports are contradictory, certain of its roles still remain confusing. In the present study, we showed that excessive 17β-estradiol could promote the migration of MCF-7 breast cancer cells and up-regulate the expression of MRTF-A, myosin regulatory light chain 9 (MYL9), and cysteine-rich angiogenic inducer 61 (CYR61). Overexpression of MRTF-A significantly promoted the migration of MCF-7 cells through its transactivation effects on MYL9 and CYR61 genes, while RNA interference-mediated knockdown of MRTF-A strongly inhibited transcription and expression of the target genes and reduced the migration ability of MCF-7 cells. These results provided novel evidence supporting the metastasis-promoting functions of MRTF-A, and implied that MRTF-A might be a switch for the estrogen pathway to change its proliferation-promoting roles into migration-stimulating roles in breast cancer. PMID:24084383

  7. Isolation and Characterization of Ischemia-Derived Astrocytes (IDAs) with Ability to Transactivate Quiescent Astrocytes

    PubMed Central

    Villarreal, Alejandro; Rosciszewski, Gerardo; Murta, Veronica; Cadena, Vanesa; Usach, Vanina; Dodes-Traian, Martin M.; Setton-Avruj, Patricia; Barbeito, Luis H.; Ramos, Alberto J.

    2016-01-01

    Reactive gliosis involving activation and proliferation of astrocytes and microglia, is a widespread but largely complex and graded glial response to brain injury. Astroglial population has a previously underestimated high heterogeneity with cells differing in their morphology, gene expression profile, and response to injury. Here, we identified a subset of reactive astrocytes isolated from brain focal ischemic lesions that show several atypical characteristics. Ischemia-derived astrocytes (IDAs) were isolated from early ischemic penumbra and core. IDA did not originate from myeloid precursors, but rather from pre-existing local progenitors. Isolated IDA markedly differ from primary astrocytes, as they proliferate in vitro with high cell division rate, show increased migratory ability, have reduced replicative senescence and grow in the presence of macrophages within the limits imposed by the glial scar. Remarkably, IDA produce a conditioned medium that strongly induced activation on quiescent primary astrocytes and potentiated the neuronal death triggered by oxygen-glucose deprivation. When re-implanted into normal rat brains, eGFP-IDA migrated around the injection site and induced focal reactive gliosis. Inhibition of gamma secretases or culture on quiescent primary astrocytes monolayers facilitated IDA differentiation to astrocytes. We propose that IDA represent an undifferentiated, pro-inflammatory, highly replicative and migratory astroglial subtype emerging from the ischemic microenvironment that may contribute to the expansion of reactive gliosis. Main Points: Ischemia-derived astrocytes (IDA) were isolated from brain ischemic tissue IDA show reduced replicative senescence, increased cell division and spontaneous migration IDA potentiate death of oxygen-glucose deprived cortical neurons IDA propagate reactive gliosis on quiescent astrocytes in vitro and in vivo Inhibition of gamma secretases facilitates IDA differentiation to astrocytes PMID:27313509

  8. Antidepressant Drugs Transactivate TrkB Neurotrophin Receptors in the Adult Rodent Brain Independently of BDNF and Monoamine Transporter Blockade

    PubMed Central

    Rantamäki, Tomi; Di Lieto, Antonio; Tammela, Päivi; Schmitt, Angelika; Lesch, Klaus-Peter; Rios, Maribel; Castrén, Eero

    2011-01-01

    Background Antidepressant drugs (ADs) have been shown to activate BDNF (brain-derived neurotrophic factor) receptor TrkB in the rodent brain but the mechanism underlying this phenomenon remains unclear. ADs act as monoamine reuptake inhibitors and after prolonged treatments regulate brain bdnf mRNA levels indicating that monoamine-BDNF signaling regulate AD-induced TrkB activation in vivo. However, recent findings demonstrate that Trk receptors can be transactivated independently of their neurotrophin ligands. Methodology In this study we examined the role of BDNF, TrkB kinase activity and monoamine reuptake in the AD-induced TrkB activation in vivo and in vitro by employing several transgenic mouse models, cultured neurons and TrkB-expressing cell lines. Principal Findings Using a chemical-genetic TrkBF616A mutant and TrkB overexpressing mice, we demonstrate that ADs specifically activate both the maturely and immaturely glycosylated forms of TrkB receptors in the brain in a TrkB kinase dependent manner. However, the tricyclic AD imipramine readily induced the phosphorylation of TrkB receptors in conditional bdnf−/− knock-out mice (132.4±8.5% of control; P = 0.01), indicating that BDNF is not required for the TrkB activation. Moreover, using serotonin transporter (SERT) deficient mice and chemical lesions of monoaminergic neurons we show that neither a functional SERT nor monoamines are required for the TrkB phosphorylation response induced by the serotonin selective reuptake inhibitors fluoxetine or citalopram, or norepinephrine selective reuptake inhibitor reboxetine. However, neither ADs nor monoamine transmitters activated TrkB in cultured neurons or cell lines expressing TrkB receptors, arguing that ADs do not directly bind to TrkB. Conclusions The present findings suggest that ADs transactivate brain TrkB receptors independently of BDNF and monoamine reuptake blockade and emphasize the need of an intact tissue context for the ability of ADs to

  9. β-Catenin Binds to the Activation Function 2 Region of the Androgen Receptor and Modulates the Effects of the N-Terminal Domain and TIF2 on Ligand-Dependent Transcription

    PubMed Central

    Song, Liang-Nian; Herrell, Roger; Byers, Stephen; Shah, Salimuddin; Wilson, Elizabeth M.; Gelmann, Edward P.

    2003-01-01

    β-Catenin is a multifunctional molecule that is activated by signaling through WNT receptors. β-Catenin can also enhance the transcriptional activity of some steroid hormone receptors such as the androgen receptor and retinoic acid receptor α. Androgens can affect nuclear translocation of β-catenin and influence its subcellular distribution. Using mammalian two-hybrid binding assays, analysis of reporter gene transcription, and coimmunoprecipitation, we now show that β-catenin binds to the androgen receptor ligand-binding domain (LBD) and modulates the transcriptional effects of TIF2 and the androgen receptor N-terminal domain (NTD). In functional assays, β-catenin bound to androgen receptor only in the presence of ligand agonists, not antagonists. β-Catenin binding to the androgen receptor LBD was independent of and cooperative with the androgen receptor NTD and the p160 coactivator TIF2, both of which bind to the activation function 2 (AF-2) region of the androgen receptor. Different mutations of androgen receptor helix 3 amino acids disrupted binding of androgen receptor NTD and β-catenin. β-Catenin, androgen receptor NTD, and TIF2 binding to the androgen receptor LBD were affected similarly by a subset of helix 12 mutations, but disruption of two sites on helix 12 affected only binding of β-catenin and not of TIF2 or the androgen receptor NTD. Mutational disruption of each of five LXXLL peptide motifs in the β-catenin armadillo repeats did not disrupt either binding to androgen receptor or transcriptional coactivation. ICAT, an inhibitor of T-cell factor 4 (TCF-4), and E-cadherin binding to β-catenin also blocked binding of the androgen receptor LBD. We also demonstrated cross talk between the WNT and androgen receptor signaling pathways because excess androgen receptor could interfere with WNT signaling and excess TCF-4 inhibited the interaction of β-catenin and androgen receptor. Taken together, the data show that β-catenin can bind to the

  10. Episodic Inhibition

    ERIC Educational Resources Information Center

    Racsmany, Mihaly; Conway, Martin A.

    2006-01-01

    Six experiments examined the proposal that an item of long-term knowledge can be simultaneously inhibited and activated. In 2 directed forgetting experiments items to-be-forgotten were found to be inhibited in list-cued recall but activated in lexical decision tasks. In 3 retrieval practice experiments, unpracticed items from practiced categories…

  11. AMF/PGI transactivates the MMP-3 gene through the activation of Src-RhoA-phosphatidylinositol 3-kinase signaling to induce hepatoma cell migration.

    PubMed

    Shih, Wen-Ling; Liao, Ming-Huei; Yu, Feng-Ling; Lin, Ping-Yuan; Hsu, Hsue-Yin; Chiu, Shu-Jun

    2008-11-01

    We have previously shown that AMF/PGI induces hepatoma cell migration through the induction of MMP-3. This work investigates how AMF/PGI activates the MMP-3 gene. We demonstrated that AMF/PGI transactivates the MMP-3 gene promoter through AP-1. The transactivation and induction of cell migration effect of AMF/PGI directly correlates with its enzymatic activity. Various analyses showed that AMF/PGI stimulated the Src-RhoA-PI3-kinase signaling pathway, and these three signaling molecules could form a complex. Our results demonstrate a new mechanism of AMF/PGI-induced cell migration and a link between Src-RhoA-PI3-kinase, AP-1, MMP-3 and hepatoma cell migration.

  12. A 1.3-Å resolution crystal structure of the HIV-1 trans-activation response region RNA stem reveals a metal ion-dependent bulge conformation

    PubMed Central

    Ippolito, Joseph A.; Steitz, Thomas A.

    1998-01-01

    The crystal structure of an HIV-1 trans-activation response region (TAR) RNA fragment containing the binding site for the trans-activation protein Tat has been determined to 1.3-Å resolution. In this crystal structure, the characteristic UCU bulge of TAR adopts a conformation that is stabilized by three divalent calcium ions and differs from those determined previously by solution NMR. One metal ion, crucial to the loop conformation, binds directly to three phosphates in the loop region. The structure emphasizes the influence of metal ion binding on RNA structure and, given the abundance of divalent metal ion in the cell, raises the question of whether metal ions play a role in the conformation of TAR RNA and the interaction of TAR with Tat and cyclin T in vivo. PMID:9707559

  13. Sequence-specific interaction of Tat protein and Tat peptides with the transactivation-responsive sequence element of human immunodeficiency virus type 1 in vitro.

    PubMed Central

    Cordingley, M G; LaFemina, R L; Callahan, P L; Condra, J H; Sardana, V V; Graham, D J; Nguyen, T M; LeGrow, K; Gotlib, L; Schlabach, A J

    1990-01-01

    Bacterially expressed Tat protein of human immunodeficiency virus type 1 binds selectively to short RNA transcripts containing the viral transactivation-responsive element (TAR). Sequences sufficient for Tat interaction map to the distal portion of the TAR stem-loop. We show that critical sequences for Tat binding are located in the single-stranded "bulge," but no requirement for specific "loop" sequences could be demonstrated. TAR RNA competed for complex formation, and TAR mutants exhibited up to 10-fold reduced affinity for Tat. Synthetic peptides containing the basic region of Tat bound selectively to TAR RNA and exhibited the same sequence requirements and similar relative affinities for mutant TAR RNA as the intact protein. These results suggest that Tat contains a small RNA-binding domain capable of recognizing TAR and implicate functional relevance for direct Tat-TAR interaction in transactivation. Images PMID:2247474

  14. Hepatocyte nuclear factor (HNF) 4α transactivation of cytochrome P450 (Cyp) 2d40 promoter is enhanced during pregnancy in mice

    PubMed Central

    Ning, Miaoran; Koh, Kwi Hye; Pan, Xian; Jeong, Hyunyoung

    2015-01-01

    We have recently reported that transactivation of cytochrome P450 (CYP) 2D6 promoter by hepatocyte nuclear factor (HNF) 4α is enhanced during pregnancy, and this is triggered in part by altered expression of small heterodimer partner (SHP) and Krüppel-like factor 9 (KLF9). The objective of this study is to determine whether this is conserved for mouse endogenous Cyp2d gene(s). Among the eight Cyp2d homologs of mouse we examined, only Cyp2d40 expression was found induced (by 6-fold) at term pregnancy as compared to pre-pregnancy level. In mice where hepatic Hnf4α was knocked-down, the pregnancy-mediated increase in Cyp2d40 expression was abrogated. Results from transient transfection, promoter reporter assays, and electrophoretic mobility shift assays indicated that HNF4α transactivates Cyp2d40 promoter via direct binding to −117/−105 of the gene. Chromatin immunoprecipitation assay showed a 2.3-fold increase in HNF4α recruitment to Cyp2d40 promoter during pregnancy. Results from mice treated with an SHP inducer (i.e., GW4064) and HepG2 cells co-transfected with KLF9 suggest that neither SHP nor KLF9 is involved in the increased HNF4α transactivation of Cyp2d40 promoter during pregnancy. Together, our results indicate that while the underlying molecular mechanism is different from that for CYP2D6, Cyp2d40 is induced during pregnancy through enhanced transactivation by HNF4α. PMID:25598084

  15. Hepatocyte nuclear factor (HNF) 4α transactivation of cytochrome P450 (Cyp) 2d40 promoter is enhanced during pregnancy in mice.

    PubMed

    Ning, Miaoran; Koh, Kwi Hye; Pan, Xian; Jeong, Hyunyoung

    2015-03-01

    We have recently reported that transactivation of cytochrome P450 (CYP) 2D6 promoter by hepatocyte nuclear factor (HNF) 4α is enhanced during pregnancy, and this is triggered in part by altered expression of small heterodimer partner (SHP) and Krüppel-like factor 9 (KLF9). The objective of this study is to determine whether this is conserved for mouse endogenous Cyp2d gene(s). Among the eight Cyp2d homologs of mouse we examined, only Cyp2d40 expression was found induced (by 6-fold) at term pregnancy as compared to pre-pregnancy level. In mice where hepatic Hnf4α was knocked-down, the pregnancy-mediated increase in Cyp2d40 expression was abrogated. Results from transient transfection, promoter reporter assays, and electrophoretic mobility shift assays indicated that HNF4α transactivates Cyp2d40 promoter via direct binding to -117/-105 of the gene. Chromatin immunoprecipitation assay showed a 2.3-fold increase in HNF4α recruitment to Cyp2d40 promoter during pregnancy. Results from mice treated with an SHP inducer (i.e., GW4064) and HepG2 cells co-transfected with KLF9 suggest that neither SHP nor KLF9 is involved in the increased HNF4α transactivation of Cyp2d40 promoter during pregnancy. Together, our results indicate that while the underlying molecular mechanism is different from that for CYP2D6, Cyp2d40 is induced during pregnancy through enhanced transactivation by HNF4α.

  16. Conditional gene expression in the epidermis of transgenic mice using the tetracycline-regulated transactivators tTA and rTA linked to the keratin 5 promoter.

    PubMed

    Diamond, I; Owolabi, T; Marco, M; Lam, C; Glick, A

    2000-11-01

    To produce conditional expression of genes in the mouse epidermis we have generated transgenic mouse lines in which the tetracycline-regulated transcriptional transactivators, tTA and rTA, are linked to the bovine keratin 5 promoter. The transactivator lines were crossed with the tetOlacZ indicator line to test for transactivation in vivo. In the absence of doxycycline, the K5/tTA line induced beta-galactosidase enzyme activity in the epidermis at a level 500-fold higher than controls, and oral and topical doxycycline caused a dose- and time-dependent suppression of beta-galactosidase mRNA levels and enzyme activity. In the K5/rTA lines, doxycycline induced beta-galactosidase activity between 3- and 50-fold higher depending on the founder line, and this occurred within 24-48 h after dosing. Histochemical analysis of all lines localized beta-galactosidase expression to the basal layer of the epidermis and the outer root sheath of the hair follicle, as well as other keratin 5 positive tissues. In several K5/rTA lines, skin-specific transactivation was restricted to the hair follicle. Treatment of these double transgenic mice with 12-O-tetradecanoyl-phorbol-13-acetate caused rapid migration of beta-galactosidase marked cells from the hair follicle through the interfollicular epidermis, demonstrating the usefulness of this specific double transgenic for fate mapping cells in the epidermis. These results show that the tetracycline regulatory system produces effective conditional gene expression in the mouse epidermis, and suggest that it should be amenable to suppression and activation of foreign genes during development and specific pathologic conditions relevant to the epidermis.

  17. Cynaropicrin from Cynara scolymus L. suppresses photoaging of skin by inhibiting the transcription activity of nuclear factor-kappa B.

    PubMed

    Tanaka, Yuka Tsuda; Tanaka, Kiyotaka; Kojima, Hiroyuki; Hamada, Tomoji; Masutani, Teruaki; Tsuboi, Makoto; Akao, Yukihiro

    2013-01-15

    Aging of skin is characterized by skin wrinkling, laxity, and pigmentation induced by several environmental stress factors. Histological changes during the photoaging of skin include hyperproliferation of keratinocytes and melanocytes causing skin wrinkles and pigmentation. Nuclear factor kappa B (NF-κB) is one of the representative transcription factors active in conjunction with inflammation. NF-κB is activated by stimulation such as ultraviolet rays and inflammatory cytokines and induces the expression of various genes such as those of basic fibroblast growth factor (bFGF) and matrix metalloprotease-1 (MMP-1). We screened several plant extracts for their possible inhibitory effect on the transcriptional activity of NF-κB. One of them, an extract from Cynara scolymus L., showed a greatest effect on the suppression of NF-κB transactivation. As a result, we found that cynaropicrin, which is a sesquiterpene lactone, inhibited the NF-κB-mediated transactivation of bFGF and MMP-1. Furthermore, it was confirmed that in an in vivo mouse model cynaropicrin prevented skin photoaging processes leading to the hyperproliferation of keratinocytes and melanocytes. These findings taken together indicate that cynaropicrin is an effective antiphotoaging agent that acts by inhibiting NF-κB-mediated transactivation. PMID:23232059

  18. Cynaropicrin from Cynara scolymus L. suppresses photoaging of skin by inhibiting the transcription activity of nuclear factor-kappa B.

    PubMed

    Tanaka, Yuka Tsuda; Tanaka, Kiyotaka; Kojima, Hiroyuki; Hamada, Tomoji; Masutani, Teruaki; Tsuboi, Makoto; Akao, Yukihiro

    2013-01-15

    Aging of skin is characterized by skin wrinkling, laxity, and pigmentation induced by several environmental stress factors. Histological changes during the photoaging of skin include hyperproliferation of keratinocytes and melanocytes causing skin wrinkles and pigmentation. Nuclear factor kappa B (NF-κB) is one of the representative transcription factors active in conjunction with inflammation. NF-κB is activated by stimulation such as ultraviolet rays and inflammatory cytokines and induces the expression of various genes such as those of basic fibroblast growth factor (bFGF) and matrix metalloprotease-1 (MMP-1). We screened several plant extracts for their possible inhibitory effect on the transcriptional activity of NF-κB. One of them, an extract from Cynara scolymus L., showed a greatest effect on the suppression of NF-κB transactivation. As a result, we found that cynaropicrin, which is a sesquiterpene lactone, inhibited the NF-κB-mediated transactivation of bFGF and MMP-1. Furthermore, it was confirmed that in an in vivo mouse model cynaropicrin prevented skin photoaging processes leading to the hyperproliferation of keratinocytes and melanocytes. These findings taken together indicate that cynaropicrin is an effective antiphotoaging agent that acts by inhibiting NF-κB-mediated transactivation.

  19. Release, uptake, and effects of extracellular human immunodeficiency virus type 1 Tat protein on cell growth and viral transactivation.

    PubMed Central

    Ensoli, B; Buonaguro, L; Barillari, G; Fiorelli, V; Gendelman, R; Morgan, R A; Wingfield, P; Gallo, R C

    1993-01-01

    During acute human immunodeficiency virus type 1 (HIV-1) infection or after transfection of the tat gene, Tat protein is released into the cell culture supernatant. In this extracellular form, Tat stimulates both HIV-1 gene expression and the growth of cells derived from Kaposi's sarcoma (KS) lesions of HIV-1-infected individuals (AIDS-KS cells). Tat protein and its biological activities appear in the cell supernatants at the peak of Tat expression, when the rate of cell death is low (infection) or cell death is undetectable (transfection) and increased levels of cytoplasmic Tat are present. Tat-containing supernatants stimulate maximal AIDS-KS cell growth but only low to moderate levels of HIV-1 gene expression. This is due to the different concentrations of exogenous Tat required for the two effects. The cell growth-promoting effects of Tat peak at between 0.1 and 1 ng of purified recombinant protein per ml in the cell growth medium and do not increase with concentration. In contrast, both the detection of nuclear-localized Tat taken up by cells and the induction of HIV-1 gene expression or replication require higher Tat concentrations (> or = 100 ng/ml), and all increase linearly with increasing amounts of the exogenous protein. These data suggest that Tat can be released by a mechanism(s) other than cell death and that the cell growth-promoting activity and the virus-transactivating effect of extracellular Tat are mediated by different pathways. Images PMID:8416373

  20. EBNA-2 transactivates a lymphoid-specific enhancer in the BamHI C promoter of Epstein-Barr virus.

    PubMed Central

    Sung, N S; Kenney, S; Gutsch, D; Pagano, J S

    1991-01-01

    Among the few Epstein-Barr virus (EBV) genes expressed during latency are the Epstein-Barr nuclear antigens (EBNAs), at least one of which contributes to the ability of the virus to transform B lymphocytes. We have analyzed a promoter located in the BamHI-C fragment of EBV which is responsible for the expression of EBNA-1 in some cell lines. Deletion analysis of a 1.4-kb region 5' of the RNA start site has identified a 700-bp fragment that is required for optimal promoter activity in latently infected B lymphocytes, as shown by promoter constructs linked to the chloramphenicol acetyltransferase reporter gene. This fragment is also able to enhance activity, in an orientation-independent manner, of the simian virus 40 early promoter linked to the chloramphenicol acetyltransferase gene. The enhancer element has some constitutive activity in EBV-negative lymphoid cells, which is increased in the presence of the EBNA-2 gene product. Further deletions have shown that the EBNA-2-responsive region requires a 98-bp region that contains a degenerate octamer-binding motif. In epithelial cells there was no enhancer activity regardless of the presence of EBNA-2. These results demonstrate that BamHI-C promoter activity may be dependent not on an enhancer contained in the ori-P, as was previously assumed, but rather on EBNA-2 transactivation of this more proximal enhancer located in the upstream region of the BamHI C promoter itself. Images PMID:1850003

  1. Improvement of the reverse tetracycline transactivator by single amino acid substitutions that reduce leaky target gene expression to undetectable levels

    PubMed Central

    Roney, Ian J.; Rudner, Adam D.; Couture, Jean-François; Kærn, Mads

    2016-01-01

    Conditional gene expression systems that enable inducible and reversible transcriptional control are essential research tools and have broad applications in biomedicine and biotechnology. The reverse tetracycline transcriptional activator is a canonical system for engineered gene expression control that enables graded and gratuitous modulation of target gene transcription in eukaryotes from yeast to human cell lines and transgenic animals. However, the system has a tendency to activate transcription even in the absence of tetracycline and this leaky target gene expression impedes its use. Here, we identify single amino-acid substitutions that greatly enhance the dynamic range of the system in yeast by reducing leaky transcription to undetectable levels while retaining high expression capacity in the presence of inducer. While the mutations increase the inducer concentration required for full induction, additional sensitivity-enhancing mutations can compensate for this effect and confer a high degree of robustness to the system. The novel transactivator variants will be useful in applications where tight and tunable regulation of gene expression is paramount. PMID:27323850

  2. Transactivator of transcription (TAT) peptide– chitosan functionalized multiwalled carbon nanotubes as a potential drug delivery vehicle for cancer therapy

    PubMed Central

    Dong, Xia; Liu, Lanxia; Zhu, Dunwan; Zhang, Hailing; Leng, Xigang

    2015-01-01

    Carbon nanotube (CNT)-based drug delivery vehicles might find great potential in cancer therapy via the combination of chemotherapy with photothermal therapy due to the strong optical absorbance of CNTs in the near-infrared region. However, the application of CNTs in cancer therapy was considerably constrained by their lack of solubility in aqueous medium, as well as the cytotoxicity caused by their hydrophobic surface. Intracellular delivery efficiency is another factor determining the application potential of CNTs in cancer therapy. In the present study, low-molecular-weight chitosan conjugated with transactivator of transcription (TAT) peptide was used for noncovalent functionalization of multiwalled carbon nanotubes (MWCNTs), aiming at providing a more efficient drug delivery vehicle for cancer therapy. The TAT–chitosan-conjugated MWCNTs (MWCNTs-TC) were further investigated for their water solubility, cytotoxicity, cell-penetrating capability, and accumulation in tumor. It was found that MWCNTs-TC were essentially nontoxic with satisfying water solubility, and they were more efficient in terms of cancer-targeted intracellular transport both in vitro and in vivo as compared with chitosan-modified MWCNTs (MWCNTs-CS), suggesting the great application potential of MWCNTs-TC in cancer therapy. PMID:26082633

  3. Transactivator of transcription (TAT) peptide- chitosan functionalized multiwalled carbon nanotubes as a potential drug delivery vehicle for cancer therapy.

    PubMed

    Dong, Xia; Liu, Lanxia; Zhu, Dunwan; Zhang, Hailing; Leng, Xigang

    2015-01-01

    Carbon nanotube (CNT)-based drug delivery vehicles might find great potential in cancer therapy via the combination of chemotherapy with photothermal therapy due to the strong optical absorbance of CNTs in the near-infrared region. However, the application of CNTs in cancer therapy was considerably constrained by their lack of solubility in aqueous medium, as well as the cytotoxicity caused by their hydrophobic surface. Intracellular delivery efficiency is another factor determining the application potential of CNTs in cancer therapy. In the present study, low-molecular-weight chitosan conjugated with transactivator of transcription (TAT) peptide was used for noncovalent functionalization of multiwalled carbon nanotubes (MWCNTs), aiming at providing a more efficient drug delivery vehicle for cancer therapy. The TAT-chitosan-conjugated MWCNTs (MWCNTs-TC) were further investigated for their water solubility, cytotoxicity, cell-penetrating capability, and accumulation in tumor. It was found that MWCNTs-TC were essentially nontoxic with satisfying water solubility, and they were more efficient in terms of cancer-targeted intracellular transport both in vitro and in vivo as compared with chitosan-modified MWCNTs (MWCNTs-CS), suggesting the great application potential of MWCNTs-TC in cancer therapy.

  4. Nuclear import of prototype foamy virus transactivator Bel1 is mediated by KPNA1, KPNA6 and KPNA7

    PubMed Central

    Duan, Jihui; Tang, Zhiqin; Mu, Hong; Zhang, Guojun

    2016-01-01

    Bel1, a transactivator of the prototype foamy virus (PFV), plays pivotal roles in the replication of PFV. Previous studies have demonstrated that Bel1 bears a nuclear localization signal (NLS); however, its amino acid sequence remains unclear and the corresponding adaptor importins have not yet been identified. In this study, we inserted various fragments of Bel1 into an EGFP-GST fusion protein and investigated their subcellular localization by fluorescence microscopy. We found that the 215PRQKRPR221 fragment, which accords with the consensus sequence K(K/R)X(K/R) of the monopartite NLS, directed the nuclear translocation of Bel1. Point mutation experiments revealed that K218, R219 and R221 were essential for the nuclear localization of Bel1. The results of GST pull-down assay revealed that the Bel1 peptide 215-221, which bears the NLS, interacted with the nucleocytoplasmic transport receptors, karyopherin alpha 1 (importin alpha 5) (KPNA1), karyopherin alpha 6 (importin alpha 7) (KPNA6) and karyopherin alpha 7 (importin alpha 8) (KPNA7). Finally, in vitro nuclear import assays demonstrated that KPNA1, KPNA6 or KPNA7, along with other necessary nuclear factors, caused Bel1 to localize to the nucleus. Thus, the findings of our study indicate that KPNA1, KPNA6 and KPNA7 are involved in Bel1 nuclear distribution. PMID:27277550

  5. Role of trans-activating proteins in the generation of active chromatin at the PHO5 promoter in S. cerevisiae.

    PubMed Central

    Fascher, K D; Schmitz, J; Hörz, W

    1990-01-01

    Induction of the PHO5 gene in Saccharomyces cerevisiae by phosphate starvation was previously shown to be accompanied by the removal of four positioned nucleosomes from the promoter. We have now investigated the role of two trans-activating proteins, encoded by PHO2 and PHO4, which bind to the PHO5 promoter. Both proteins are absolutely required for the chromatin transition to occur as shown by analysis of null mutants of the two genes. Transformation of these mutant strains with plasmids containing the respective genes restores the wild type chromatin response. Increasing the gene dosage of PHO2 and of PHO4 makes it possible to differentiate functionally between the two proteins. From over-expressing PHO4 in a wild type and also in a pho2 null mutant strain and complementary experiments with PHO2, it is concluded that the PHO4 protein is the primary trigger for the chromatin transition, consistent with one of its two binding sites being located between positioned nucleosomes in repressed chromatin and thereby accessible. PHO2, the binding site of which is located within a nucleosome under conditions of PHO5 repression, contributes to the chromatin transition either by destabilizing histone-DNA interactions or by under-going interactions with PHO4. Images Fig. 2. Fig. 4. Fig. 5. Fig. 6. Fig. 7. PMID:2196175

  6. HIV-1 trans-activator of transcription substitutes for oxidative signaling in activation-induced T cell death.

    PubMed

    Gülow, Karsten; Kaminski, Marcin; Darvas, Katalin; Süss, Dorothee; Li-Weber, Min; Krammer, Peter H

    2005-05-01

    Termination of an immune response requires elimination of activated T lymphocytes by activation-induced cell death (AICD). In AICD, CD95 (Apo-1/Fas) ligand (L) triggers apoptosis of CD95-positive activated T lymphocytes. In AIDS patients, AICD is strongly enhanced and accelerated. We and others have previously shown that HIV-1 trans-activator of transcription (HIV-1 Tat) sensitizes T cells toward CD95-mediated apoptosis and up-regulates CD95L expression by affecting the cellular redox balance. In this study, we show that it is hydrogen peroxide (H(2)O(2)) that functions as an essential second messenger in TCR signaling. The H(2)O(2) signal combined with simultaneous calcium (Ca(2+)) influx into the cytosol constitutes the minimal requirement for induction of CD95L expression. Either signal alone is insufficient. We further show that HIV-1 Tat interferes with TCR signaling and induces a H(2)O(2) signal. H(2)O(2) generated by HIV-1 Tat combines with CD4-dependent calcium influx and causes massive T cell apoptosis. Thus, our data provide an explanation for CD4(+) T lymphocyte depletion during progression of AIDS.

  7. Structural characterization of a noncovalent complex between ubiquitin and the transactivation domain of the erythroid-specific factor EKLF.

    PubMed

    Raiola, Luca; Lussier-Price, Mathieu; Gagnon, David; Lafrance-Vanasse, Julien; Mascle, Xavier; Arseneault, Genevieve; Legault, Pascale; Archambault, Jacques; Omichinski, James G

    2013-11-01

    Like other acidic transactivation domains (TAD), the minimal TAD from the erythroid-specific transcription factor EKLF (EKLFTAD) has been shown to contribute both to its transcriptional activity as well as to its ubiquitin(UBI)-mediated degradation. In this article, we examine the activation-degradation role of the acidic TAD of EKLF and demonstrate that the first 40 residues (EKLFTAD1) within this region form a noncovalent interaction with UBI. Nuclear magnetic resonance (NMR) structural studies of an EKLFTAD1-UBI complex show that EKLFTAD1 adopts a 14-residue α helix that forms the recognition interface with UBI in a similar manner as the UBI-interacting helix of Rabex5. We also identify a similar interaction between UBI and the activation-degradation region of SREBP1a, but not with the activation-degradation regions of p53, GAL4, and VP16. These results suggest that select activation-degradation regions like the ones found in EKLF and SREBP1a function in part through their ability to form noncovalent interactions with UBI. PMID:24139988

  8. The Grainyhead-like epithelial transactivator Get-1/Grhl3 regulates epidermal terminal differentiation and interacts functionally with LMO4.

    PubMed

    Yu, Zhengquan; Lin, Kevin K; Bhandari, Ambica; Spencer, Joel A; Xu, Xiaoman; Wang, Ning; Lu, Zhongxian; Gill, Gordon N; Roop, Dennis R; Wertz, Philip; Andersen, Bogi

    2006-11-01

    Defective permeability barrier is an important feature of many skin diseases and causes mortality in premature infants. To investigate the control of barrier formation, we characterized the epidermally expressed Grainyhead-like epithelial transactivator (Get-1)/Grhl3, a conserved mammalian homologue of Grainyhead, which plays important roles in cuticle development in Drosophila. Get-1 interacts with the LIM-only protein LMO4, which is co-expressed in the developing mammalian epidermis. The epidermis of Get-1(-/-) mice showed a severe barrier function defect associated with impaired differentiation of the epidermis, including defects of the stratum corneum, extracellular lipid composition and cell adhesion in the granular layer. The Get-1 mutation affects multiple genes linked to terminal differentiation and barrier function, including most genes of the epidermal differentiation complex. Get-1 therefore directly or indirectly regulates a broad array of epidermal differentiation genes encoding structural proteins, lipid metabolizing enzymes and cell adhesion molecules. Although deletion of the LMO4 gene had no overt consequences for epidermal development, the epidermal terminal differentiation defect in mice deleted for both Get-1 and LMO4 is much more severe than in Get-1(-/-) mice with striking impairment of stratum corneum formation. These findings indicate that the Get-1 and LMO4 genes interact functionally to regulate epidermal terminal differentiation.

  9. New mechanisms of signal transduction inhibitor action: receptor tyrosine kinase down-regulation and blockade of signal transactivation.

    PubMed

    Lee, Adrian V; Schiff, Rachel; Cui, Xiaojiang; Sachdev, Deepali; Yee, Douglas; Gilmore, Andrew P; Streuli, Charles H; Oesterreich, Steffi; Hadsell, Darryl L

    2003-01-01

    The explosion of signal transduction research over the last 10 years has provided a unique insight into the complexity of these intricate pathways. Whereas intermediates of multiple signaling pathways have been identified, understanding their function and, in particular, the interactions between them has become a daunting task. The increasing evidence that many of these pathways can cross-talk with each other via signal transactivation inevitably raises the question of how cells determine specificity in signaling. Despite the mind-numbing complexity of these pathways, progress has been made in developing highly specific and potent signal transduction inhibitors (STIs). STIs show promise in the treatment of cancer in preclinical studies and are currently in a number of clinical trials. Whereas many of these agents were "rationally designed," we barely understand their mechanisms of action. This review will highlight how recent studies using these STIs have elucidated novel mechanisms of STI action that may be used in the development of new therapeutic strategies for the treatment of cancer.

  10. The Ability of Positive Transcription Elongation Factor b To Transactivate Human Immunodeficiency Virus Transcription Depends on a Functional Kinase Domain, Cyclin T1, and Tat

    PubMed Central

    Fujinaga, Koh; Cujec, Thomas P.; Peng, Junmin; Garriga, Judit; Price, David H.; Graña, Xavier; Peterlin, B. Matija

    1998-01-01

    By binding to the transactivation response element (TAR) RNA, the transcriptional transactivator (Tat) from the human immunodeficiency virus increases rates of elongation rather than initiation of viral transcription. Two cyclin-dependent serine/threonine kinases, CDK7 and CDK9, which phosphorylate the C-terminal domain of RNA polymerase II, have been implicated in Tat transactivation in vivo and in vitro. In this report, we demonstrate that CDK9, which is the kinase component of the positive transcription elongation factor b (P-TEFb) complex, can activate viral transcription when tethered to the heterologous Rev response element RNA via the regulator of expression of virion proteins (Rev). The kinase activity of CDK9 and cyclin T1 is essential for these effects. Moreover, P-TEFb binds to TAR only in the presence of Tat. We conclude that Tat–P-TEFb complexes bind to TAR, where CDK9 modifies RNA polymerase II for the efficient copying of the viral genome. PMID:9696809

  11. Prostaglandin E2 transactivates the colony-stimulating factor-1 receptor and synergizes with colony-stimulating factor-1 in the induction of macrophage migration via the mitogen-activated protein kinase ERK1/2.

    PubMed

    Digiacomo, Graziana; Ziche, Marina; Dello Sbarba, Persio; Donnini, Sandra; Rovida, Elisabetta

    2015-06-01

    Prostaglandin E2 (PGE2), a key mediator of immunity, inflammation, and cancer, acts through 4 G-protein-coupled E-prostanoid receptors (EPs 1-4). Crosstalk between EPs and receptor tyrosine kinases also occurs. Colony-stimulating factor-1 receptor (CSF-1R) is an RTK that sustains the survival, proliferation, and motility of monocytes/macrophages, which are an essential component of innate immunity and cancer development. The aim of this study was to investigate on a possible crosstalk between EP and CSF-1R. In BAC1.2F5 and RAW264.7 murine macrophages, CSF-1 (EC₅₀ = 18.1 and 10.2 ng/ml, respectively) and PGE2 (EC₅₀ = 1.5 and 5.5 nM, respectively) promoted migration. PGE2 induced rapid CSF-1R phosphorylation that was dependent on Src family kinases (SFKs). CSF-1R inhibition reduced PGE2-elicited ERK1/2 phosphorylation and macrophage migration, indicating that CSF-1R plays a role in PGE2-mediated immunoregulation. EP4 appeared responsible for functional PGE2/CSF-1R crosstalk. Furthermore, PGE2 synergized with CSF-1 in inducing ERK1/2 phosphorylation and macrophage migration. ERK1/2 inhibition completely blocked migration induced by the combination CSF-1/PGE2. CSF-1/PGE2 functional interaction with respect to migration also occurred in bone marrow-derived murine macrophages (EC₅₀ CSF-1, 6.7 ng/ml; EC₅₀ PGE2, 16.7 nM). These results indicated that PGE2 transactivates CSF-1R and synergizes with its signaling at ERK1/2 level in promoting macrophage migration.

  12. Antidepressants activate the lysophosphatidic acid receptor LPA(1) to induce insulin-like growth factor-I receptor transactivation, stimulation of ERK1/2 signaling and cell proliferation in CHO-K1 fibroblasts.

    PubMed

    Olianas, Maria C; Dedoni, Simona; Onali, Pierluigi

    2015-06-15

    Different lines of evidence indicate that the lysophosphatidic acid (LPA) receptor LPA1 is involved in neurogenesis, synaptic plasticity and anxiety-related behavior, but little is known on whether this receptor can be targeted by neuropsychopharmacological agents. The present study investigated the effects of different antidepressants on LPA1 signaling. We found that in Chinese hamster ovary (CHO)-K1 fibroblasts expressing endogenous LPA1 tricyclic and tetracyclic antidepressants and fluoxetine induced the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) and CREB. This response was antagonized by either LPA1 blockade with Ki16425 and AM966 or knocking down LPA1 with siRNA. Antidepressants induced ERK1/2 phosphorylation in human embryonic kidney (HEK)-293 cells overexpressing LPA1, but not in wild-type cells. In PathHunter™ assay measuring receptor-β-arrestin interaction, amitriptyline, mianserin and fluoxetine failed to induce activation of LPA2 and LPA3 stably expressed in CHO-K1 cells. ERK1/2 stimulation by antidepressants and LPA was suppressed by pertussis toxin and inhibition of Src, phosphatidylinositol-3 kinase and insulin-like growth factor-I receptor (IGF-IR) activities. Antidepressants and LPA induced tyrosine phosphorylation of IGF-IR and insulin receptor-substrate-1 through LPA1 and Src. Prolonged exposure of CHO-K1 fibroblasts to either mianserin, mirtazapine or LPA enhanced cell proliferation as indicated by increased [(3)H]-thymidine incorporation and Ki-67 immunofluorescence. This effect was inhibited by blockade of LPA1- and ERK1/2 activity. These data provide evidence that different antidepressants induce LPA1 activation, leading to receptor tyrosine kinase transactivation, stimulation of ERK1/2 signaling and enhanced cell proliferation.

  13. Transcriptional repressor NIR interacts with the p53-inhibiting ubiquitin ligase MDM2

    PubMed Central

    Heyne, Kristina; Förster, Juliane; Schüle, Roland; Roemer, Klaus

    2014-01-01

    NIR (novel INHAT repressor) can bind to p53 at promoters and inhibit p53-mediated gene transactivation by blocking histone acetylation carried out by p300/CBP. Like NIR, the E3 ubiquitin ligase MDM2 can also bind and inhibit p53 at promoters. Here, we present data indicating that NIR, which shuttles between the nucleolus and nucleoplasm, not only binds to p53 but also directly to MDM2, in part via the central acidic and zinc finger domain of MDM2 that is also contacted by several other nucleolus-based MDM2/p53-regulating proteins. Like some of these, NIR was able to inhibit the ubiquitination of MDM2 and stabilize MDM2; however, unlike these nucleolus-based MDM2 regulators, NIR did not inhibit MDM2 to activate p53. Rather, NIR cooperated with MDM2 to repress p53-induced transactivation. This cooperative repression may at least in part involve p300/CBP. We show that NIR can block the acetylation of p53 and MDM2. Non-acetylated p53 has been documented previously to more readily associate with inhibitory MDM2. NIR may thus help to sustain the inhibitory p53:MDM2 complex, and we present evidence suggesting that all three proteins can indeed form a ternary complex. In sum, our findings suggest that NIR can support MDM2 to suppress p53 as a transcriptional activator. PMID:24413661

  14. CITED2 silencing sensitizes cancer cells to cisplatin by inhibiting p53 trans-activation and chromatin relaxation on the ERCC1 DNA repair gene

    PubMed Central

    Liu, Yu-Chin; Chang, Pu-Yuan; Chao, Chuck C.-K.

    2015-01-01

    In this study, we show that silencing of CITED2 using small-hairpin RNA (shCITED2) induced DNA damage and reduction of ERCC1 gene expression in HEK293, HeLa and H1299 cells, even in the absence of cisplatin. In contrast, ectopic expression of ERCC1 significantly reduced intrinsic and induced DNA damage levels, and rescued the effects of CITED2 silencing on cell viability. The effects of CITED2 silencing on DNA repair and cell death were associated with p53 activity. Furthermore, CITED2 silencing caused severe elimination of the p300 protein and markers of relaxed chromatin (acetylated H3 and H4, i.e. H3K9Ac and H3K14Ac) in HEK293 cells. Chromatin immunoprecipitation assays further revealed that DNA damage induced binding of p53 along with H3K9Ac or H3K14Ac at the ERCC1 promoter, an effect which was almost entirely abrogated by silencing of CITED2 or p300. Moreover, lentivirus-based CITED2 silencing sensitized HeLa cell line-derived tumor xenografts to cisplatin in immune-deficient mice. These results demonstrate that CITED2/p300 can be recruited by p53 at the promoter of the repair gene ERCC1 in response to cisplatin-induced DNA damage. The CITED2/p300/p53/ERCC1 pathway is thus involved in the cell response to cisplatin and represents a potential target for cancer therapy. PMID:26384430

  15. CITED2 silencing sensitizes cancer cells to cisplatin by inhibiting p53 trans-activation and chromatin relaxation on the ERCC1 DNA repair gene.

    PubMed

    Liu, Yu-Chin; Chang, Pu-Yuan; Chao, Chuck C-K

    2015-12-15

    In this study, we show that silencing of CITED2 using small-hairpin RNA (shCITED2) induced DNA damage and reduction of ERCC1 gene expression in HEK293, HeLa and H1299 cells, even in the absence of cisplatin. In contrast, ectopic expression of ERCC1 significantly reduced intrinsic and induced DNA damage levels, and rescued the effects of CITED2 silencing on cell viability. The effects of CITED2 silencing on DNA repair and cell death were associated with p53 activity. Furthermore, CITED2 silencing caused severe elimination of the p300 protein and markers of relaxed chromatin (acetylated H3 and H4, i.e. H3K9Ac and H3K14Ac) in HEK293 cells. Chromatin immunoprecipitation assays further revealed that DNA damage induced binding of p53 along with H3K9Ac or H3K14Ac at the ERCC1 promoter, an effect which was almost entirely abrogated by silencing of CITED2 or p300. Moreover, lentivirus-based CITED2 silencing sensitized HeLa cell line-derived tumor xenografts to cisplatin in immune-deficient mice. These results demonstrate that CITED2/p300 can be recruited by p53 at the promoter of the repair gene ERCC1 in response to cisplatin-induced DNA damage. The CITED2/p300/p53/ERCC1 pathway is thus involved in the cell response to cisplatin and represents a potential target for cancer therapy.

  16. Temperature inducible β-sheet structure in the transactivation domains of retroviral regulatory proteins of the Rev family

    NASA Astrophysics Data System (ADS)

    Thumb, Werner; Graf, Christine; Parslow, Tristram; Schneider, Rainer; Auer, Manfred

    1999-11-01

    The interaction of the human immunodeficiency virus type 1 (HIV-1) regulatory protein Rev with cellular cofactors is crucial for the viral life cycle. The HIV-1 Rev transactivation domain is functionally interchangeable with analog regions of Rev proteins of other retroviruses suggesting common folding patterns. In order to obtain experimental evidence for similar structural features mediating protein-protein contacts we investigated activation domain peptides from HIV-1, HIV-2, VISNA virus, feline immunodeficiency virus (FIV) and equine infectious anemia virus (EIAV) by CD spectroscopy, secondary structure prediction and sequence analysis. Although different in polarity and hydrophobicity, all peptides showed a similar behavior with respect to solution conformation, concentration dependence and variations in ionic strength and pH. Temperature studies revealed an unusual induction of β-structure with rising temperatures in all activation domain peptides. The high stability of β-structure in this region was demonstrated in three different peptides of the activation domain of HIV-1 Rev in solutions containing 40% hexafluoropropanol, a reagent usually known to induce α-helix into amino acid sequences. Sequence alignments revealed similarities between the polar effector domains from FIV and EIAV and the leucine rich (hydrophobic) effector domains found in HIV-1, HIV-2 and VISNA. Studies on activation domain peptides of two dominant negative HIV-1 Rev mutants, M10 and M32, pointed towards different reasons for the biological behavior. Whereas the peptide containing the M10 mutation (L 78E 79→D 78L 79) showed wild-type structure, the M32 mutant peptide (L 78L 81L 83→A 78A 81A 83) revealed a different protein fold to be the reason for the disturbed binding to cellular cofactors. From our data, we conclude, that the activation domain of Rev proteins from different viral origins adopt a similar fold and that a β-structural element is involved in binding to a

  17. Recognition of the disordered p53 transactivation domain by the transcriptional adapter zinc finger domains of CREB-binding protein.

    PubMed

    Krois, Alexander S; Ferreon, Josephine C; Martinez-Yamout, Maria A; Dyson, H Jane; Wright, Peter E

    2016-03-29

    An important component of the activity of p53 as a tumor suppressor is its interaction with the transcriptional coactivators cyclic-AMP response element-binding protein (CREB)-binding protein (CBP) and p300, which activate transcription of p53-regulated stress response genes and stabilize p53 against ubiquitin-mediated degradation. The highest affinity interactions are between the intrinsically disordered N-terminal transactivation domain (TAD) of p53 and the TAZ1 and TAZ2 domains of CBP/p300. The NMR spectra of simple binary complexes of the TAZ1 and TAZ2 domains with the p53TAD suffer from exchange broadening, but innovations in construct design and isotopic labeling have enabled us to obtain high-resolution structures using fusion proteins, uniformly labeled in the case of the TAZ2-p53TAD fusion and segmentally labeled through transintein splicing for the TAZ1-p53TAD fusion. The p53TAD is bipartite, with two interaction motifs, termed AD1 and AD2, which fold to form short amphipathic helices upon binding to TAZ1 and TAZ2 whereas intervening regions of the p53TAD remain flexible. Both the AD1 and AD2 motifs bind to hydrophobic surfaces of the TAZ domains, with AD2 making more extensive hydrophobic contacts consistent with its greater contribution to the binding affinity. Binding of AD1 and AD2 is synergistic, and structural studies performed with isolated motifs can be misleading. The present structures of the full-length p53TAD complexes demonstrate the versatility of the interactions available to an intrinsically disordered domain containing bipartite interaction motifs and provide valuable insights into the structural basis of the affinity changes that occur upon stress-related posttranslational modification. PMID:26976603

  18. Recognition of the disordered p53 transactivation domain by the transcriptional adapter zinc finger domains of CREB-binding protein

    PubMed Central

    Krois, Alexander S.; Ferreon, Josephine C.; Martinez-Yamout, Maria A.; Wright, Peter E.

    2016-01-01

    An important component of the activity of p53 as a tumor suppressor is its interaction with the transcriptional coactivators cyclic-AMP response element-binding protein (CREB)-binding protein (CBP) and p300, which activate transcription of p53-regulated stress response genes and stabilize p53 against ubiquitin-mediated degradation. The highest affinity interactions are between the intrinsically disordered N-terminal transactivation domain (TAD) of p53 and the TAZ1 and TAZ2 domains of CBP/p300. The NMR spectra of simple binary complexes of the TAZ1 and TAZ2 domains with the p53TAD suffer from exchange broadening, but innovations in construct design and isotopic labeling have enabled us to obtain high-resolution structures using fusion proteins, uniformly labeled in the case of the TAZ2–p53TAD fusion and segmentally labeled through transintein splicing for the TAZ1–p53TAD fusion. The p53TAD is bipartite, with two interaction motifs, termed AD1 and AD2, which fold to form short amphipathic helices upon binding to TAZ1 and TAZ2 whereas intervening regions of the p53TAD remain flexible. Both the AD1 and AD2 motifs bind to hydrophobic surfaces of the TAZ domains, with AD2 making more extensive hydrophobic contacts consistent with its greater contribution to the binding affinity. Binding of AD1 and AD2 is synergistic, and structural studies performed with isolated motifs can be misleading. The present structures of the full-length p53TAD complexes demonstrate the versatility of the interactions available to an intrinsically disordered domain containing bipartite interaction motifs and provide valuable insights into the structural basis of the affinity changes that occur upon stress-related posttranslational modification. PMID:26976603

  19. Leptin overexpression in VTA trans-activates the hypothalamus whereas prolonged leptin action in either region cross-desensitizes.

    PubMed

    Scarpace, P J; Matheny, M; Kirichenko, N; Gao, Y X; Tümer, N; Zhang, Y

    2013-02-01

    High-fat feeding or CNS leptin overexpression in chow-fed rats results in a region-specific cellular leptin resistance in medial basal hypothalamic regions and the ventral tegmental area (VTA). The present investigation examined the effects of targeted chronic leptin overexpression in the VTA as compared with the medial basal hypothalamus on long-term body weight homeostasis. The study also examined if this targeted intervention conserves regional leptin sensitivity or results in localized leptin resistance. Cellular leptin resistance was assessed by leptin-stimulated phosphorylation of signal transducers and activators of transcription 3 (STAT3). Tyrosine hydroxylase was measured in hypothalamus and VTA along with brown adipose tissue uncoupling protein 1. Leptin overexpression in VTA tempered HF-induced obesity, but to a slightly lesser extent than that with leptin overexpression in the hypothalamus. Moreover, the overexpression of leptin in the VTA stimulated cellular STAT3 phosphorylation in several regions of the medial basal hypothalamus, whereas verexpression in the hypothalamus did not activate STAT3 signaling in the VTA. This unidirectional trans-stimulation did not appear to involve migration of either the vector or the gene product. Long-term leptin overexpression in either the medial basal hypothalamus or VTA caused desensitization of leptin signaling in the treated region and cross-desensitization of leptin signaling in the untreated region. These results demonstrate a role of leptin receptors in the VTA in long-term body weight regulation, but the trans-activation of the hypothalamus following VTA leptin stimulation suggests that an integrative response involving both brain regions may account for the observed physiological outcomes.

  20. Mitochondrial dysfunction and transactivation of p53-dependent apoptotic genes in BaP-treated human fetal lung fibroblasts.

    PubMed

    Yang, Guangtao; Jiang, Ying; Rao, Kaimin; Chen, Xi; Wang, Qian; Liu, Ailin; Xiong, Wei; Yuan, Jing

    2011-12-01

    Benzo(a)pyrene (BaP) has been shown to be an inducer of apoptosis. However, mechanisms involved in BaP-induced mitochondrial dysfunction are not well-known. In this study, human fetal lung fibroblasts cells were treated with BaP (8, 16, 32, 64 and 128 μM) for 4 and 12 h. Cell viability, intracellular level of reactive oxygen species (ROS), total antioxidant capacity (T-AOC), mitochondrial membrane potential (ΔΨ(m)) and cytochrome c release were determined. Changes in transcriptional levels of p53-dependent apoptotic genes (p53, APAF1, CASPASE3, CASPASE9, NOXA and PUMA) were measured. At time point of 4 h, BaP induced the intracellular ROS generation in 64 (p < .05) and 128 μM BaP groups (p < .01) but decreased the T-AOC activities in 32, 64 (p < .05 for both) and 128 μM BaP groups (p < .01). At time point of 12 h, ΔΨ(m) significantly decreased in ≥32 μM BaP groups (p < .05 for all). Amount of mitochondrial cytochrome c significantly increased in 128 μM BaP group (p < .01). Transcriptional levels of CASPASE3, CASPASE9, APAF1 and PUMA were up-regulated in all BaP groups (p < .05 for all) and in ≥32 μM groups for NOXA (p < .05). But only in 16 μM BaP group a relatively little expression of p53 mRNA was observed (p < .05). The results indicate that in the earlier period BaP promoted the generation of excessive ROS and subsequently the mitochondrial depolarization, whereas transactivations of the p53-dependent apoptotic genes were significantly induced at the later period.

  1. Urinary miR-16 transactivated by C/EBPβ reduces kidney function after ischemia/reperfusion–induced injury

    PubMed Central

    Chen, Hsi-Hsien; Lan, Yi-Fan; Li, Hsiao-Fen; Cheng, Ching-Feng; Lai, Pei-Fang; Li, Wei-Hua; Lin, Heng

    2016-01-01

    Ischemia-reperfusion (I/R) induced acute kidney injury (AKI) is regulated by transcriptional factors and microRNAs (miRs). However, modulation of miRs by transcriptional factors has not been characterized in AKI. Here, we found that urinary miR-16 was 100-fold higher in AKI patients. MiR-16 was detected earlier than creatinine in mouse after I/R. Using TargetScan, the 3′UTR of B-cell lymphoma 2 (BCL-2) was found complementary to miR-16 to decrease the fluorescent reporter activity. Overexpression of miR-16 in mice significantly attenuated renal function and increased TUNEL activity in epithelium tubule cells. The CCAAT enhancer binding protein beta (C/EBP-β) increased the expression of miR-16 after I/R injury. The ChIP and luciferase promoter assay indicated that about −1.0 kb to −0.5 kb upstream of miR-16 genome promoter region containing C/EBP-β binding motif transcriptionally regulated miR-16 expression. Meanwhile, the level of pri-miR-16 was higher in mice infected with lentivirus containing C/EBP-β compared with wild-type (WT) mice and overexpression of C/EBP-β in the kidney of WT mice reduced kidney function, increased kidney apoptosis, and elevated urinary miR-16 level. Our results indicated that miR-16 was transactivated by C/EBP-β resulting in aggravated I/R induced AKI and that urinary miR-16 may serve as a potential biomarker for AKI. PMID:27297958

  2. Exosomes from HIV-1-infected Cells Stimulate Production of Pro-inflammatory Cytokines through Trans-activating Response (TAR) RNA.

    PubMed

    Sampey, Gavin C; Saifuddin, Mohammed; Schwab, Angela; Barclay, Robert; Punya, Shreya; Chung, Myung-Chul; Hakami, Ramin M; Zadeh, Mohammad Asad; Lepene, Benjamin; Klase, Zachary A; El-Hage, Nazira; Young, Mary; Iordanskiy, Sergey; Kashanchi, Fatah

    2016-01-15

    HIV-1 infection results in a chronic illness because long-term highly active antiretroviral therapy can lower viral titers to an undetectable level. However, discontinuation of therapy rapidly increases virus burden. Moreover, patients under highly active antiretroviral therapy frequently develop various metabolic disorders, neurocognitive abnormalities, and cardiovascular diseases. We have previously shown that exosomes containing trans-activating response (TAR) element RNA enhance susceptibility of undifferentiated naive cells to HIV-1 infection. This study indicates that exosomes from HIV-1-infected primary cells are highly abundant with TAR RNA as detected by RT-real time PCR. Interestingly, up to a million copies of TAR RNA/μl were also detected in the serum from HIV-1-infected humanized mice suggesting that TAR RNA may be stable in vivo. Incubation of exosomes from HIV-1-infected cells with primary macrophages resulted in a dramatic increase of proinflammatory cytokines, IL-6 and TNF-β, indicating that exosomes containing TAR RNA could play a direct role in control of cytokine gene expression. The intact TAR molecule was able to bind to PKR and TLR3 effectively, whereas the 5' and 3' stems (TAR microRNAs) bound best to TLR7 and -8 and none to PKR. Binding of TAR to PKR did not result in its phosphorylation, and therefore, TAR may be a dominant negative decoy molecule in cells. The TLR binding through either TAR RNA or TAR microRNA potentially can activate the NF-κB pathway and regulate cytokine expression. Collectively, these results imply that exosomes containing TAR RNA could directly affect the proinflammatory cytokine gene expression and may explain a possible mechanism of inflammation observed in HIV-1-infected patients under cART.

  3. Nuclear import of prototype foamy virus transactivator Bel1 is mediated by KPNA1, KPNA6 and KPNA7.

    PubMed

    Duan, Jihui; Tang, Zhiqin; Mu, Hong; Zhang, Guojun

    2016-08-01

    Bel1, a transactivator of the prototype foamy virus (PFV), plays pivotal roles in the replication of PFV. Previous studies have demonstrated that Bel1 bears a nuclear localization signal (NLS); however, its amino acid sequence remains unclear and the corresponding adaptor importins have not yet been identified. In this study, we inserted various fragments of Bel1 into an EGFP-GST fusion protein and investigated their subcellular localization by fluorescence microscopy. We found that the 215PRQKRPR221 fragment, which accords with the consensus sequence K(K/R)X(K/R) of the monopartite NLS, directed the nuclear translocation of Bel1. Point mutation experiments revealed that K218, R219 and R221 were essential for the nuclear localization of Bel1. The results of GST pull-down assay revealed that the Bel1 peptide 215-221, which bears the NLS, interacted with the nucleocytoplasmic transport receptors, karyopherin alpha 1 (importin alpha 5) (KPNA1), karyopherin alpha 6 (importin alpha 7) (KPNA6) and karyopherin alpha 7 (importin alpha 8) (KPNA7). Finally, in vitro nuclear import assays demonstrated that KPNA1, KPNA6 or KPNA7, along with other necessary nuclear factors, caused Bel1 to localize to the nucleus. Thus, the findings of our study indicate that KPNA1, KPNA6 and KPNA7 are involved in Bel1 nuclear distribution. PMID:27277550

  4. Retinoic acid receptors inhibit AP1 activation by regulating extracellular signal-regulated kinase and CBP recruitment to an AP1-responsive promoter.

    PubMed

    Benkoussa, Madjid; Brand, Céline; Delmotte, Marie-Hélène; Formstecher, Pierre; Lefebvre, Philippe

    2002-07-01

    Retinoids exhibit antineoplastic activities that may be linked to retinoid receptor-mediated transrepression of activating protein 1 (AP1), a heterodimeric transcription factor composed of fos- and jun-related proteins. Here we show that transcriptional activation of an AP1-regulated gene through the mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) pathway (MAPK(ERK)) is characterized, in intact cells, by a switch from a fra2-junD dimer to a junD-fosB dimer loading on its promoter and by simultaneous recruitment of ERKs, CREB-binding protein (CBP), and RNA polymerase II. All-trans-retinoic acid (atRA) receptor (RAR) was tethered constitutively to the AP1 promoter. AP1 transrepression by retinoic acid was concomitant to glycogen synthase kinase 3 activation, negative regulation of junD hyperphosphorylation, and to decreased RNA polymerase II recruitment. Under these conditions, fra1 loading to the AP1 response element was strongly increased. Importantly, CBP and ERKs were excluded from the promoter in the presence of atRA. AP1 transrepression by retinoids was RAR and ligand dependent, but none of the functions required for RAR-mediated transactivation was necessary for AP1 transrepression. These results indicate that transrepressive effects of retinoids are mediated through a mechanism unrelated to transcriptional activation, involving the RAR-dependent control of transcription factors and cofactor assembly on AP1-regulated promoters.

  5. Ligand-Dependent Conformational Dynamics of Dihydrofolate Reductase

    PubMed Central

    Reddish, Michael J.; Vaughn, Morgan B.; Fu, Rong; Dyer, R. Brian

    2016-01-01

    Enzymes are known to change among several conformational states during turnover. The role of such dynamic structural changes in catalysis is not fully understood. The influence of dynamics in catalysis can be inferred, but not proven, by comparison of equilibrium structures of protein variants and protein–ligand complexes. A more direct way to establish connections between protein dynamics and the catalytic cycle is to probe the kinetics of specific protein motions in comparison to progress along the reaction coordinate. We have examined the enzyme model system dihydrofolate reductase (DHFR) from Escherichia coli with tryptophan fluorescence-probed temperature-jump spectroscopy. We aimed to observe the kinetics of the ligand binding and ligand-induced conformational changes of three DHFR complexes to establish the relationship among these catalytic steps. Surprisingly, in all three complexes, the observed kinetics do not match a simple sequential two-step process. Through analysis of the relationship between ligand concentration and observed rate, we conclude that the observed kinetics correspond to the ligand binding step of the reaction and a noncoupled enzyme conformational change. The kinetics of the conformational change vary with the ligand's identity and presence but do not appear to be directly related to progress along the reaction coordinate. These results emphasize the need for kinetic studies of DHFR with highly specific spectroscopic probes to determine which dynamic events are coupled to the catalytic cycle and which are not. PMID:26901612

  6. Rutin inhibits B[a]PDE-induced cyclooxygenase-2 expression by targeting EGFR kinase activity.

    PubMed

    Choi, Seunghwan; Lim, Tae-Gyu; Hwang, Mun Kyung; Kim, Yoon-A; Kim, Jiyoung; Kang, Nam Joo; Jang, Tae Su; Park, Jun-Seong; Yeom, Myeong Hun; Lee, Ki Won

    2013-11-15

    Rutin is a well-known flavonoid that exists in various natural sources. Accumulative studies have represented the biological effects of rutin, such as anti-oxidative and anti-inflammatory effects. However, the underlying mechanisms of rutin and its direct targets are not understood. We investigated whether rutin reduced B[a]PDE-induced-COX-2 expression. The transactivation of AP-1 and NF-κB were inhibited by rutin. Rutin also attenuated B[a]PDE-induced Raf/MEK/ERK and Akt activation, but had no effect on the phosphorylation of EGFR. An in vitro kinase assay revealed rutin suppressed EGFR kinase activity. We also confirmed direct binding between rutin and EGFR, and found that the binding was regressed by ATP. The EGFR inhibitor also inhibited the B[a]PDE-induced MEK/ERK and Akt signaling pathways and subsequently, suppressed COX-2 expression and promoter activity, in addition to suppressing the transactivation of AP-1 and NF-κB. In EGFR(-/-)mouse embryonic fibroblast cells, B[a]PDE-induced COX-2 expression was also diminished. Collectively, rutin inhibits B[a]PDE-induced COX-2 expression by suppressing the Raf/MEK/ERK and Akt signaling pathways. EGFR appeared to be the direct target of rutin.

  7. GATA-1 associates with and inhibits p53

    PubMed Central

    Mas, Caroline; Archambault, Patrick; Di Lello, Paola

    2009-01-01

    In addition to orchestrating the expression of all erythroid-specific genes, GATA-1 controls the growth, differentiation, and survival of the erythroid lineage through the regulation of genes that manipulate the cell cycle and apoptosis. The stages of mammalian erythropoiesis include global gene inactivation, nuclear condensation, and enucleation to yield circulating erythrocytes, and some of the genes whose expression are altered by GATA-1 during this process are members of the p53 pathway. In this study, we demonstrate a specific in vitro interaction between the transactivation domain of p53 (p53TAD) and a segment of the GATA-1 DNA-binding domain that includes the carboxyl-terminal zinc-finger domain. We also show by immunoprecipitation that the native GATA-1 and p53 interact in erythroid cells and that activation of p53-responsive promoters in an erythroid cell line can be inhibited by the overexpression of GATA-1. Mutational analysis reveals that GATA-1 inhibition of p53 minimally requires the segment of the GATA-1 DNA-binding domain that interacts with p53TAD. This inhibition is reciprocal, as the activation of a GATA-1–responsive promoter can be inhibited by p53. Based on these findings, we conclude that inhibition of the p53 pathway by GATA-1 may be essential for erythroid cell development and survival. PMID:19411634

  8. GATA-1 associates with and inhibits p53.

    PubMed

    Trainor, Cecelia D; Mas, Caroline; Archambault, Patrick; Di Lello, Paola; Omichinski, James G

    2009-07-01

    In addition to orchestrating the expression of all erythroid-specific genes, GATA-1 controls the growth, differentiation, and survival of the erythroid lineage through the regulation of genes that manipulate the cell cycle and apoptosis. The stages of mammalian erythropoiesis include global gene inactivation, nuclear condensation, and enucleation to yield circulating erythrocytes, and some of the genes whose expression are altered by GATA-1 during this process are members of the p53 pathway. In this study, we demonstrate a specific in vitro interaction between the transactivation domain of p53 (p53TAD) and a segment of the GATA-1 DNA-binding domain that includes the carboxyl-terminal zinc-finger domain. We also show by immunoprecipitation that the native GATA-1 and p53 interact in erythroid cells and that activation of p53-responsive promoters in an erythroid cell line can be inhibited by the overexpression of GATA-1. Mutational analysis reveals that GATA-1 inhibition of p53 minimally requires the segment of the GATA-1 DNA-binding domain that interacts with p53TAD. This inhibition is reciprocal, as the activation of a GATA-1-responsive promoter can be inhibited by p53. Based on these findings, we conclude that inhibition of the p53 pathway by GATA-1 may be essential for erythroid cell development and survival. PMID:19411634

  9. Zinc finger protein 131 inhibits estrogen signaling by suppressing estrogen receptor {alpha} homo-dimerization

    SciTech Connect

    Oh, Yohan; Chung, Kwang Chul

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer ZNF131 directly interacts with ER{alpha}. Black-Right-Pointing-Pointer The binding affinity of ZNF131 to ER{alpha} increases upon E2 stimulation. Black-Right-Pointing-Pointer ZNF131 inhibits ER{alpha}-mediated trans-activation by suppressing its homo-dimerization. Black-Right-Pointing-Pointer ZNF131 inhibits ER{alpha}-dimerization and E2-induced breast cancer cell proliferation. Black-Right-Pointing-Pointer ZNF131 inhibits estrogen signaling by acting as an ER{alpha}-co-repressor. -- Abstract: Steroid hormone estrogen elicits various physiological functions, many of which are mediated through two structurally and functionally distinct estrogen receptors, ER{alpha} and ER{beta}. The functional role of zinc finger protein 131 (ZNF131) is poorly understood, but it is assumed to possess transcriptional regulation activity due to the presence of a DNA binding motif. A few recent reports, including ours, revealed that ZNF131 acts as a negative regulator of ER{alpha} and that SUMO modification potentiates the negative effect of ZNF131 on estrogen signaling. However, its molecular mechanism for ER{alpha} inhibition has not been elucidated in detail. Here, we demonstrate that ZNF131 directly interacts with ER{alpha}, which consequently inhibits ER{alpha}-mediated trans-activation by suppressing its homo-dimerization. Moreover, we show that the C-terminal region of ZNF131 containing the SUMOylation site is necessary for its inhibition of estrogen signaling. Taken together, these data suggest that ZNF131 inhibits estrogen signaling by acting as an ER{alpha}-co-repressor.

  10. Differential transactivation by orphan nuclear receptor NOR1 and its fusion gene product EWS/NOR1: possible involvement of poly(ADP-ribose) polymerase I, PARP-1.

    PubMed

    Ohkura, Naganari; Nagamura, Yuko; Tsukada, Toshihiko

    2008-10-15

    In extraskeletal myxoid chondrosarcoma, a chromosomal translocation creates a gene fusion between EWS and an orphan nuclear receptor, NOR1. The resulting fusion protein EWS/NOR1 has been believed to lead to malignant transformation by functioning as a transactivator for NOR1-target genes. By comparing the gene expression profiles of NOR1- and EWS/NOR1-overexpressing cells, we found that they largely shared up-regulated genes, but no significant correlation was observed with respect to the transactivation levels of each gene. In addition, the proteins associated with NOR1 and EWS/NOR1 were mostly the same in these cells. The results suggest that these proteins differentially transactivate overlapping target genes through a similar transcriptional machinery. To clarify the mechanisms underlying the transcriptional divergence between NOR1 and EWS/NOR1, we searched for alternatively associated proteins, and identified poly(ADP-ribose) polymerase I (PARP-1) as an NOR1-specific binding protein. Consistent with its binding properties, PARP-1 acted as a transcriptional repressor of NOR1, but not EWS/NOR1, in a luciferase reporter assay employing PARP-1(-/-) fibroblasts. Interestingly, suppressive activity of PARP-1 was observed in a DNA response element-specific manner, and in a subtype-specific manner toward the NR4A family (Nur77, Nurr1, and NOR1), suggesting that PARP-1 plays a role in the diversity of transcriptional regulation mediated by the NR4A family in normal cells. Altogether, our findings suggest that NOR1 and EWS/NOR1 regulate overlapping target genes differently by utilizing associated proteins, including PARP-1; and that EWS/NOR1 may acquire oncogenic activities by avoiding (or gaining) transcription factor-specific modulation by the associated proteins.

  11. In vitro and in silico evaluation of transactivation potencies of avian AHR1 and AHR2 by endogenous ligands: Implications for the physiological role of avian AHR2.

    PubMed

    Kim, In-Sung; Hwang, Ji-Hee; Hirano, Masashi; Iwata, Hisato; Kim, Eun-Young

    2016-09-01

    Aryl hydrocarbon receptor (AHR) is well conserved from invertebrates to vertebrates, and it mediates the toxic effects of exogenous ligands, including dioxins. Recent studies reported that AHRs activated by endogenous ligands play critical roles in mammalian physiological homeostasis. Avian species possess at least two AHR isoforms (AHR1 and AHR2), which exhibit species- and isoform-specific transactivation potencies to exogenous ligands, whereas mammals possess a single AHR. To delineate the profiles and roles of endogenous ligands for avian AHR isoforms, we investigated in vitro transactivation potencies of avian AHRs (AHR1 and AHR2 from the jungle crow, Corvus macrorhynchos; common cormorant, Phalacrocorax carbo; and black-footed albatross, Phoebastria nigripes) treated with the endogenous tryptophan metabolites 6-formylindolo [3,2-b] carbazole (FICZ), l-kynurenine (l-Kyn), kynurenic acid (KYNA), and indoxyl sulfate (IS). Furthermore, we analyzed the binding mode of these ligands to each avian AHR isoform by in silico docking simulations. The EC50 of FICZ (0.009-0.032nM) was similar regardless of the species or isoform of AHR. The estimated in silico binding mode of FICZ to AHRs was well conserved in both isoforms. The transactivation potencies of avian AHRs to other tryptophan metabolites were 10(5)-10(7) fold lower than those for FICZ, and EC50 values varied in a species- and isoform-specific manner. This was consistent with poor conservation of the binding mode of l-Kyn, KYNA, and IS predicted in in silico docking simulations. Our results suggest that in avian species, FICZ is the most potent endogenous AHR ligand, and that AHR1 and AHR2 are physiologically functional. PMID:27060260

  12. Inhibition of Mer and Axl receptor tyrosine kinases leads to increased apoptosis and improved chemosensitivity in human neuroblastoma.

    PubMed

    Li, Yixin; Wang, Xiqian; Bi, Shaojie; Zhao, Kun; Yu, Chao

    2015-02-13

    Ectopic expression of Mer and Axl receptor tyrosine kinases (RTKs) are frequently found in various cancers as known to promote oncogenesis by activating antiapoptotic signaling pathways. However, the roles of these receptors in neuroblastoma remain unclear. We found Mer and Axl was co-expressed in neuroblastoma patient samples and cell lines. Ligand-dependent Mer or Axl activation led to an increase in phosphorylated ERK1/2, AKT and FAK indicating roles for these RTKs in multiple oncogenic processes. Furthermore, Mer and Axl knockdown led to apoptosis and inhibition of migration as well as a significant increase in chemosensitivity in response to cisplatin and vincristine treatment. Taken together, our results demonstrated that inhibition of Mer and Axl improved apoptotic response and chemosensitivity in neuroblastoma, providing new insights into development of novel therapeutic strategies by targeting these oncogenes.

  13. Inhibition of human papillomavirus DNA replication by small molecule antagonists of the E1-E2 protein interaction.

    PubMed

    White, Peter W; Titolo, Steve; Brault, Karine; Thauvette, Louise; Pelletier, Alex; Welchner, Ewald; Bourgon, Lise; Doyon, Louise; Ogilvie, William W; Yoakim, Christiane; Cordingley, Michael G; Archambault, Jacques

    2003-07-18

    Human papillomavirus (HPV) DNA replication is initiated by recruitment of the E1 helicase by the E2 protein to the viral origin. Screening of our corporate compound collection with an assay measuring the cooperative binding of E1 and E2 to the origin identified a class of small molecule inhibitors of the protein interaction between E1 and E2. Isothermal titration calorimetry and changes in protein fluorescence showed that the inhibitors bind to the transactivation domain of E2, the region that interacts with E1. These compounds inhibit E2 of the low risk HPV types 6 and 11 but not those of high risk HPV types or of cottontail rabbit papillomavirus. Functional evidence that the transactivation domain is the target of inhibition was obtained by swapping this domain between a sensitive (HPV11) and a resistant (cottontail rabbit papillomavirus) E2 type and by identifying an amino acid substitution, E100A, that increases inhibition by approximately 10-fold. This class of inhibitors was found to antagonize specifically the E1-E2 interaction in vivo and to inhibit HPV DNA replication in transiently transfected cells. These results highlight the potential of the E1-E2 interaction as a small molecule antiviral target.

  14. Modulation of F1 hybrid stature without altering parent plants through trans-activated expression of a mutated rice GAI homologue.

    PubMed

    Su, Ning; Sullivan, James A; Deng, Xing Wang

    2005-03-01

    Hybrid breeding, by taking advantage of heterosis, brings about many superior properties to the F1 progeny. However, some properties, such as increased plant height, are not desirable for agronomic purposes. To specifically counter the height increase associated with hybrid progeny, we employed an Arabidopsis model and tested a trans-activation system for specifically expressing a mutated GAI gene only in the F1 hybrid plants to reduce plant stature. A transcriptional activator, the Gal4 DNA-binding domain fused to the acidic activation domain of herpes simplex virus VP16 protein, driven by a maize ubiquitin promoter, was introduced in one parental line. A rice GAI homologue with an N-terminal deletion of the DELLA domain, driven by a promoter that is responsive to the transcriptional activator, was transferred into another parental line. After genetic crossing, trans-activation of the GAI mutant gene resulted in a dwarf phenotype. Over 50 pair-wise crosses between the parental lines were performed, and analyses suggested that the percentage of F1 progeny exhibiting dwarfism ranged from about 25% to 100%. Furthermore, the dwarfism trait introduced in F1 progeny did not seem to affect total seed yield. Our result suggests the feasibility of manipulating F1 hybrid progeny traits without affecting parent plants or the agronomic property of the progeny.

  15. Deregulation of Rb-E2F1 Axis Causes Chromosomal Instability by Engaging the Transactivation Function of Cdc20–Anaphase-Promoting Complex/Cyclosome

    PubMed Central

    Nath, Somsubhra; Chowdhury, Abhishek; Dey, Sanjib; Roychoudhury, Anirban; Ganguly, Abira; Bhattacharyya, Dibyendu

    2014-01-01

    The E2F family of transcription factors regulates genes involved in various aspects of the cell cycle. Beyond the well-documented role in G1/S transition, mitotic regulation by E2F has also been reported. Proper mitotic progression is monitored by the spindle assembly checkpoint (SAC). The SAC ensures bipolar separation of chromosomes and thus prevents aneuploidy. There are limited reports on the regulation of the SAC by E2F. Our previous work identified the SAC protein Cdc20 as a novel transcriptional regulator of the mitotic ubiquitin carrier protein UbcH10. However, none of the Cdc20 transcription complex proteins have any known DNA binding domain. Here we show that an E2F1-DP1 heterodimer is involved in recruitment of the Cdc20 transcription complex to the UBCH10 promoter and in transactivation of the gene. We further show that inactivation of Rb can facilitate this transactivation process. Moreover, this E2F1-mediated regulation of UbcH10 influences mitotic progression. Deregulation of this pathway results in premature anaphase, chromosomal abnormalities, and aneuploidy. We conclude that excess E2F1 due to Rb inactivation recruits the complex of Cdc20 and the anaphase-promoting complex/cyclosome (Cdc20-APC/C) to deregulate the expression of UBCH10, leading to chromosomal instability in cancer cells. PMID:25368385

  16. Deregulation of Rb-E2F1 axis causes chromosomal instability by engaging the transactivation function of Cdc20-anaphase-promoting complex/cyclosome.

    PubMed

    Nath, Somsubhra; Chowdhury, Abhishek; Dey, Sanjib; Roychoudhury, Anirban; Ganguly, Abira; Bhattacharyya, Dibyendu; Roychoudhury, Susanta

    2015-01-01

    The E2F family of transcription factors regulates genes involved in various aspects of the cell cycle. Beyond the well-documented role in G1/S transition, mitotic regulation by E2F has also been reported. Proper mitotic progression is monitored by the spindle assembly checkpoint (SAC). The SAC ensures bipolar separation of chromosomes and thus prevents aneuploidy. There are limited reports on the regulation of the SAC by E2F. Our previous work identified the SAC protein Cdc20 as a novel transcriptional regulator of the mitotic ubiquitin carrier protein UbcH10. However, none of the Cdc20 transcription complex proteins have any known DNA binding domain. Here we show that an E2F1-DP1 heterodimer is involved in recruitment of the Cdc20 transcription complex to the UBCH10 promoter and in transactivation of the gene. We further show that inactivation of Rb can facilitate this transactivation process. Moreover, this E2F1-mediated regulation of UbcH10 influences mitotic progression. Deregulation of this pathway results in premature anaphase, chromosomal abnormalities, and aneuploidy. We conclude that excess E2F1 due to Rb inactivation recruits the complex of Cdc20 and the anaphase-promoting complex/cyclosome (Cdc20-APC/C) to deregulate the expression of UBCH10, leading to chromosomal instability in cancer cells.

  17. Subcellular localisation of BAG-1 and its regulation of vitamin D receptor-mediated transactivation and involucrin expression in oral keratinocytes: Implications for oral carcinogenesis

    SciTech Connect

    Lee, San San; Crabb, Simon J.; Janghra, Nari; Carlberg, Carsten; Williams, Ann C.; Cutress, Ramsey I.; Packham, Graham; Hague, Angela

    2007-09-10

    In oral cancers, cytoplasmic BAG-1 overexpression is a marker of poor prognosis. BAG-1 regulates cellular growth, differentiation and survival through interactions with diverse proteins, including the vitamin D receptor (VDR), a key regulator of keratinocyte growth and differentiation. BAG-1 is expressed ubiquitously in human cells as three major isoforms of 50 kDa (BAG-1L), 46 kDa (BAG-1M) and 36 kDa (BAG-1S) from a single mRNA. In oral keratinocytes BAG-1L, but not BAG-1M and BAG-1S, enhanced VDR transactivation in response to 1{alpha},25-dihydroxyvitamin D{sub 3.} BAG-1L was nucleoplasmic and nucleolar, whereas BAG-1S and BAG-1M were cytoplasmic and nucleoplasmic in localisation. Having identified the nucleolar localisation sequence in BAG-1L, we showed that mutation of this sequence did not prevent BAG-1L from potentiating VDR activity. BAG-1L also potentiated transactivation of known vitamin-D-responsive gene promoters, osteocalcin and 24-hydroxylase, and enhanced VDR-dependent transcription and protein expression of the keratinocyte differentiation marker, involucrin. These results demonstrate endogenous gene regulation by BAG-1L by potentiating nuclear hormone receptor function and suggest a role for BAG-1L in 24-hydroxylase regulation of vitamin D metabolism and the cellular response of oral keratinocytes to 1{alpha},25-dihydroxyvitamin D{sub 3}. By contrast to the cytoplasmic BAG-1 isoforms, BAG-1L may act to suppress tumorigenesis.

  18. Transactivation of a cellular promoter by the NS1 protein of the parvovirus minute virus of mice through a putative hormone-responsive element.

    PubMed Central

    Vanacker, J M; Corbau, R; Adelmant, G; Perros, M; Laudet, V; Rommelaere, J

    1996-01-01

    The promoter of the thyroid hormone receptor alpha gene (c-erbA-1) is activated by the nonstructural protein 1 (NS1) of parvovirus minute virus of mice (prototype strain [MVMp]) in ras-transformed FREJ4 cells that are permissive for lytic MVMp replication. This stimulation may be related to the sensitivity of host cells to MVMp, as it does not take place in parental FR3T3 cells, which are resistant to the parvovirus killing effect. The analysis of a series of deletion and point mutants of the c-erbA-1 promoter led to the identification of an upstream region that is necessary for NS1-driven transactivation. This sequence harbors a putative hormone-responsive element and is sufficient to render a minimal promoter NS1 inducible in FREJ4 but not in FR3T3 cells, and it is involved in distinct interactions with proteins from the respective cell lines. The NS1-responsive element of the c-erbA-1 promoter bears no homology with sequences that were previously reported to be necessary for NS1 DNA binding and transactivation. Altogether, our data point to a novel, cell-specific mechanism of promoter activation by NS1. PMID:8642664

  19. The wedelolactone derivative inhibits estrogen receptor-mediated breast, endometrial, and ovarian cancer cells growth.

    PubMed

    Xu, Defeng; Lin, Tzu-Hua; Yeh, Chiuan-Ren; Cheng, Max A; Chen, Lu-Min; Chang, Chawnshang; Yeh, Shuyuan

    2014-01-01

    Estrogen and estrogen receptor (ER)-mediated signaling pathways play important roles in the etiology and progression of human breast, endometrial, and ovarian cancers. Attenuating ER activities by natural products and their derivatives is a relatively practical strategy to control and reduce breast, endometrial, and ovarian cancer risk. Here, we found 3-butoxy-1,8,9-trihydroxy-6H-benzofuro[3,2-c]benzopyran-6-one (BTB), a new derivative of wedelolactone, could effectively inhibit the 17-estradiol (E2)-induced ER transactivation and suppress the growth of breast cancer as well as endometrial and ovarian cancer cells. Our results indicate that 2.5 μM BTB effectively suppresses ER-positive, but not ER-negative, breast, endometrial, and ovarian cancer cells. Furthermore, our data indicate that BTB can modulate ER transactivation and suppress the expression of E2-mediated ER target genes (Cyclin D1, E2F1, and TERT) in the ER-positive MCF-7, Ishikawa, and SKOV-3 cells. Importantly, this BTB mediated inhibition of ER activity is selective since BTB does not suppress the activities of other nuclear receptors, including glucocorticoid receptor and progesterone receptor, suggesting that BTB functions as a selective ER signaling inhibitor with the potential to treat breast, endometrial, and ovarian cancers.

  20. Activation of Epidermal Growth Factor Receptor in Macrophages Mediates Feedback Inhibition of M2 Polarization and Gastrointestinal Tumor Cell Growth.

    PubMed

    Zhao, Gang; Liu, Liping; Peek, Richard M; Hao, Xishan; Polk, D Brent; Li, Hui; Yan, Fang

    2016-09-23

    EGF receptor (EGFR) in tumor cells serves as a tumor promoter. However, information about EGFR activation in macrophages in regulating M2 polarization and tumor development is limited. This study aimed to investigate the effects of EGFR activation in macrophages on M2 polarization and development of gastrointestinal tumors. IL-4, a cytokine to elicit M2 polarization, stimulated release of an EGFR ligand, HB-EGF, and transactivation and down-regulation of EGFR in Raw 264.7 cells and peritoneal macrophages from WT mice. Knockdown of HB-EGF in macrophages inhibited EGFR transactivation by IL-4. IL-4-stimulated STAT6 activation, Arg1 and YM1 gene expression, and HB-EGF production were further enhanced by inhibition of EGFR activity in Raw 264.7 cells using an EGFR kinase inhibitor and in peritoneal macrophages from Egfr(wa5) mice with kinase inactive EGFR and by knockdown of EGFR in peritoneal macrophages from Egfr(fl/fl) LysM-Cre mice with myeloid cell-specific EGFR deletion. Chitin induced a higher level of M2 polarization in peritoneal macrophages in Egfr(fl/fl) LysM-Cre mice than that in Egfr(fl/fl) mice. Accordingly, IL-4-conditioned medium stimulated growth and epithelial-to-mesenchymal transition in gastric epithelial and colonic tumor cells, which were suppressed by that from Raw 264.7 cells with HB-EGF knockdown but promoted by that from Egfr(wa5) and Egfr(fl/fl) LysM-Cre peritoneal macrophages. Clinical assessment revealed that the number of macrophages with EGFR expression became less, indicating decreased inhibitory effects on M2 polarization, in late stage of human gastric cancers. Thus, IL-4-stimulated HB-EGF-dependent transactivation of EGFR in macrophages may mediate inhibitory feedback for M2 polarization and HB-EGF production, thereby inhibiting gastrointestinal tumor growth.

  1. Vitamin D3 transactivates the zinc and manganese transporter SLC30A10 via the Vitamin D receptor.

    PubMed

    Claro da Silva, Tatiana; Hiller, Christian; Gai, Zhibo; Kullak-Ublick, Gerd A

    2016-10-01

    competition EMSA revealed binding of select sequences, namely, nt -1623/-1588 and nt -1758/-1723 relative to the transcription start site, to VDR-containing nuclear extracts. In conclusion, we have shown that vitamin D3 transactivates the SLC30A10 gene in a VDR-dependent manner, resulting in increased ZnT10 protein expression. Because SLC30A10 is highly expressed in the small intestine, it is possible that the control of zinc and manganese systemic levels is regulated by vitamin D3 in the intestine. Zinc, manganese and vitamin D are important for bone metabolism and brain health. Future examination of a possible role for supplementation or chelation of zinc and manganese, alongside vitamin D3 administration, will further our understanding of its potential benefit in the treatment of specific illnesses, such as osteoporosis and Parkinson's disease. PMID:27107558

  2. Vitamin D3 transactivates the zinc and manganese transporter SLC30A10 via the Vitamin D receptor.

    PubMed

    Claro da Silva, Tatiana; Hiller, Christian; Gai, Zhibo; Kullak-Ublick, Gerd A

    2016-10-01

    competition EMSA revealed binding of select sequences, namely, nt -1623/-1588 and nt -1758/-1723 relative to the transcription start site, to VDR-containing nuclear extracts. In conclusion, we have shown that vitamin D3 transactivates the SLC30A10 gene in a VDR-dependent manner, resulting in increased ZnT10 protein expression. Because SLC30A10 is highly expressed in the small intestine, it is possible that the control of zinc and manganese systemic levels is regulated by vitamin D3 in the intestine. Zinc, manganese and vitamin D are important for bone metabolism and brain health. Future examination of a possible role for supplementation or chelation of zinc and manganese, alongside vitamin D3 administration, will further our understanding of its potential benefit in the treatment of specific illnesses, such as osteoporosis and Parkinson's disease.

  3. Pumpkin seed extract: Cell growth inhibition of hyperplastic and cancer cells, independent of steroid hormone receptors.

    PubMed

    Medjakovic, Svjetlana; Hobiger, Stefanie; Ardjomand-Woelkart, Karin; Bucar, Franz; Jungbauer, Alois

    2016-04-01

    Pumpkin seeds have been known in folk medicine as remedy for kidney, bladder and prostate disorders since centuries. Nevertheless, pumpkin research provides insufficient data to back up traditional beliefs of ethnomedical practice. The bioactivity of a hydro-ethanolic extract of pumpkin seeds from the Styrian pumpkin, Cucurbita pepo L. subsp. pepo var. styriaca, was investigated. As pumpkin seed extracts are standardized to cucurbitin, this compound was also tested. Transactivational activity was evaluated for human androgen receptor, estrogen receptor and progesterone receptor with in vitro yeast assays. Cell viability tests with prostate cancer cells, breast cancer cells, colorectal adenocarcinoma cells and a hyperplastic cell line from benign prostate hyperplasia tissue were performed. As model for non-hyperplastic cells, effects on cell viability were tested with a human dermal fibroblast cell line (HDF-5). No transactivational activity was found for human androgen receptor, estrogen receptor and progesterone receptor, for both, extract and cucurbitin. A cell growth inhibition of ~40-50% was observed for all cell lines, with the exception of HDF-5, which showed with ~20% much lower cell growth inhibition. Given the receptor status of some cell lines, a steroid-hormone receptor independent growth inhibiting effect can be assumed. The cell growth inhibition for fast growing cells together with the cell growth inhibition of prostate-, breast- and colon cancer cells corroborates the ethnomedical use of pumpkin seeds for a treatment of benign prostate hyperplasia. Moreover, due to the lack of androgenic activity, pumpkin seed applications can be regarded as safe for the prostate. PMID:26976217

  4. Structural and functional characterization of a complex between the acidic transactivation domain of EBNA2 and the Tfb1/p62 subunit of TFIIH.

    PubMed

    Chabot, Philippe R; Raiola, Luca; Lussier-Price, Mathieu; Morse, Thomas; Arseneault, Genevieve; Archambault, Jacques; Omichinski, James G

    2014-03-01

    Infection with the Epstein-Barr virus (EBV) can lead to a number of human diseases including Hodgkin's and Burkitt's lymphomas. The development of these EBV-linked diseases is associated with the presence of nine viral latent proteins, including the nuclear antigen 2 (EBNA2). The EBNA2 protein plays a crucial role in EBV infection through its ability to activate transcription of both host and viral genes. As part of this function, EBNA2 associates with several host transcriptional regulatory proteins, including the Tfb1/p62 (yeast/human) subunit of the general transcription factor IIH (TFIIH) and the histone acetyltransferase CBP(CREB-binding protein)/p300, through interactions with its C-terminal transactivation domain (TAD). In this manuscript, we examine the interaction of the acidic TAD of EBNA2 (residues 431-487) with the Tfb1/p62 subunit of TFIIH and CBP/p300 using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimeter (ITC) and transactivation studies in yeast. NMR studies show that the TAD of EBNA2 binds to the pleckstrin homology (PH) domain of Tfb1 (Tfb1PH) and that residues 448-471 (EBNA2₄₄₈₋₄₇₁) are necessary and sufficient for this interaction. NMR structural characterization of a Tfb1PH-EBNA2₄₄₈₋₄₇₁ complex demonstrates that the intrinsically disordered TAD of EBNA2 forms a 9-residue α-helix in complex with Tfb1PH. Within this helix, three hydrophobic amino acids (Trp458, Ile461 and Phe462) make a series of important interactions with Tfb1PH and their importance is validated in ITC and transactivation studies using mutants of EBNA2. In addition, NMR studies indicate that the same region of EBNA2 is also required for binding to the KIX domain of CBP/p300. This study provides an atomic level description of interactions involving the TAD of EBNA2 with target host proteins. In addition, comparison of the Tfb1PH-EBNA2₄₄₈₋₄₇₁ complex with structures of the TAD of p53 and VP16 bound to Tfb1

  5. Structural and Functional Characterization of a Complex between the Acidic Transactivation Domain of EBNA2 and the Tfb1/p62 Subunit of TFIIH

    PubMed Central

    Lussier-Price, Mathieu; Morse, Thomas; Arseneault, Genevieve; Archambault, Jacques; Omichinski, James G.

    2014-01-01

    Infection with the Epstein-Barr virus (EBV) can lead to a number of human diseases including Hodgkin's and Burkitt's lymphomas. The development of these EBV-linked diseases is associated with the presence of nine viral latent proteins, including the nuclear antigen 2 (EBNA2). The EBNA2 protein plays a crucial role in EBV infection through its ability to activate transcription of both host and viral genes. As part of this function, EBNA2 associates with several host transcriptional regulatory proteins, including the Tfb1/p62 (yeast/human) subunit of the general transcription factor IIH (TFIIH) and the histone acetyltransferase CBP(CREB-binding protein)/p300, through interactions with its C-terminal transactivation domain (TAD). In this manuscript, we examine the interaction of the acidic TAD of EBNA2 (residues 431–487) with the Tfb1/p62 subunit of TFIIH and CBP/p300 using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimeter (ITC) and transactivation studies in yeast. NMR studies show that the TAD of EBNA2 binds to the pleckstrin homology (PH) domain of Tfb1 (Tfb1PH) and that residues 448–471 (EBNA2448–471) are necessary and sufficient for this interaction. NMR structural characterization of a Tfb1PH-EBNA2448–471 complex demonstrates that the intrinsically disordered TAD of EBNA2 forms a 9-residue α-helix in complex with Tfb1PH. Within this helix, three hydrophobic amino acids (Trp458, Ile461 and Phe462) make a series of important interactions with Tfb1PH and their importance is validated in ITC and transactivation studies using mutants of EBNA2. In addition, NMR studies indicate that the same region of EBNA2 is also required for binding to the KIX domain of CBP/p300. This study provides an atomic level description of interactions involving the TAD of EBNA2 with target host proteins. In addition, comparison of the Tfb1PH-EBNA2448–471 complex with structures of the TAD of p53 and VP16 bound to Tfb1PH highlights the versatility of

  6. Structural and functional characterization of a complex between the acidic transactivation domain of EBNA2 and the Tfb1/p62 subunit of TFIIH.

    PubMed

    Chabot, Philippe R; Raiola, Luca; Lussier-Price, Mathieu; Morse, Thomas; Arseneault, Genevieve; Archambault, Jacques; Omichinski, James G

    2014-03-01

    Infection with the Epstein-Barr virus (EBV) can lead to a number of human diseases including Hodgkin's and Burkitt's lymphomas. The development of these EBV-linked diseases is associated with the presence of nine viral latent proteins, including the nuclear antigen 2 (EBNA2). The EBNA2 protein plays a crucial role in EBV infection through its ability to activate transcription of both host and viral genes. As part of this function, EBNA2 associates with several host transcriptional regulatory proteins, including the Tfb1/p62 (yeast/human) subunit of the general transcription factor IIH (TFIIH) and the histone acetyltransferase CBP(CREB-binding protein)/p300, through interactions with its C-terminal transactivation domain (TAD). In this manuscript, we examine the interaction of the acidic TAD of EBNA2 (residues 431-487) with the Tfb1/p62 subunit of TFIIH and CBP/p300 using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimeter (ITC) and transactivation studies in yeast. NMR studies show that the TAD of EBNA2 binds to the pleckstrin homology (PH) domain of Tfb1 (Tfb1PH) and that residues 448-471 (EBNA2₄₄₈₋₄₇₁) are necessary and sufficient for this interaction. NMR structural characterization of a Tfb1PH-EBNA2₄₄₈₋₄₇₁ complex demonstrates that the intrinsically disordered TAD of EBNA2 forms a 9-residue α-helix in complex with Tfb1PH. Within this helix, three hydrophobic amino acids (Trp458, Ile461 and Phe462) make a series of important interactions with Tfb1PH and their importance is validated in ITC and transactivation studies using mutants of EBNA2. In addition, NMR studies indicate that the same region of EBNA2 is also required for binding to the KIX domain of CBP/p300. This study provides an atomic level description of interactions involving the TAD of EBNA2 with target host proteins. In addition, comparison of the Tfb1PH-EBNA2₄₄₈₋₄₇₁ complex with structures of the TAD of p53 and VP16 bound to Tfb1

  7. Epstein-Barr virus nuclear protein 2 transactivation of the latent membrane protein 1 promoter is mediated by J kappa and PU.1.

    PubMed Central

    Johannsen, E; Koh, E; Mosialos, G; Tong, X; Kieff, E; Grossman, S R

    1995-01-01

    Expression of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) oncogene is regulated by the EBV nuclear protein 2 (EBNA-2) transactivator. EBNA-2 is known to interact with the cellular DNA-binding protein J kappa and is recruited to promoters containing the GTGGGAA J kappa recognition sequence. The minimal EBNA-2-responsive LMP-1 promoter includes one J kappa-binding site, and we now show that mutation of that site, such that J kappa cannot bind, reduces EBNA-2 responsiveness by 60%. To identify other factors which interact with the LMP-1 EBNA-2 response element (E2RE), a -236/-145 minimal E2RE was used as a probe in an electrophoretic mobility shift assay. The previously characterized factors J kappa, PU.1, and AML1 bind to the LMP-1 E2RE, along with six other unidentified factors (LBF2 to LBF7). Binding sites were mapped for each factor. LBF4 is B- and T-cell specific and recognizes the PU.1 GGAA core sequence as shown by methylation interference. LBF4 has a molecular mass of 105 kDa and is probably unrelated to PU.1. LBF2 was found only in epithelial cell lines, whereas LBF3, LBF5, LBF6, and LBF7 were not cell type specific. Mutations of the AML1- or LBF4-binding sites had no effect on EBNA-2 transactivation, whereas mutation of the PU.1-binding site completely eliminated EBNA-2 responses. A gst-EBNA-2 fusion protein specifically depleted PU.1 from nuclear extracts and bound in vitro translated PU.1, providing biochemical evidence for a direct EBNA-2-PU.1 interaction. Thus, EBNA-2 transactivation of the LMP-1 promoter is dependent on interaction with at least two distinct sequence-specific DNA-binding proteins, J kappa and PU.1. LBF3, LBF5, LBF6, or LBF7 may also be involved, since their binding sites also contribute to EBNA-2 responsiveness. PMID:7983717

  8. Inhibition of human immunodeficiency virus type 1 transcription and replication by DNA sequence-selective plant lignans.

    PubMed

    Gnabre, J N; Brady, J N; Clanton, D J; Ito, Y; Dittmer, J; Bates, R B; Huang, R C

    1995-11-21

    A plant lignan, 3'-O-methyl nordihydroguaiaretic acid (3'-O-methyl NDGA, denoted Malachi 4:5-6 or Mal.4; molecular weigth 316), was isolated from Larrea tridentata and found to be able to inhibit human immunodeficiency virus (HIV) Tat-regulated transactivation in vivo, induce protection of lymphoblastoid CEM-SS cells from HIV (strain IIIB) killing, and suppress the replication of five HIV-1 strains (WM, MN, VS, JR-CSF, and IIIB) in mitogen-stimulated peripheral blood mononuclear cells, all in a dose-dependent manner. Mal.4 inhibits both basal transcription and Tat-regulated transactivation in vitro. The target of Mal.4 has been localized to nucleotides -87 to -40 of the HIV long terminal repeat. Mal.4 directly and specifically interferes with the binding of Sp1 to Sp1 sites in the HIV long terminal repeat. By inhibiting proviral expression, Mal.4 may be able to interrupt the life cycles of both wild-type and reverse transcriptase or protease mutant viruses in HIV-infected patients. PMID:7479972

  9. HIV-1 TAT Inhibits Microglial Phagocytosis of Aβ Peptide

    PubMed Central

    Giunta, Brian; Zhou, Yuyan; Hou, Huayan; Rrapo, Elona; Fernandez, Francisco; Tan, Jun

    2008-01-01

    Human immunodeficiency virus (HIV)-associated dementia (HAD) is a subcortical neuropsychiatric syndrome that has increased in prevalence in the era of highly active antiretroviral therapy (HAART). Several studies demonstrated increased amyloidosis in brains of HIV patients and suggested that there may be a significant number of long-term HIV survivors with co-morbid Alzheimer's disease (AD) in the future. We show HIV-1 Tat protein inhibits microglial uptake of Aβ1-42 peptide, a process that is enhanced by interferon-gamma (IFN-γ) and rescued by the STAT1 inhibitor (-)-epigallocatechin-3-gallate (EGCG). It is hypothesized that reduced Aβ uptake occurs through IFN-γ mediated STAT1 activation. This process promotes a switch from a phagocytic to an antigen presenting phenotype in microglia through activation of class II transactivator (CIITA). Additionally, we show that HIV-1 Tat significantly disrupts apolipoprotein-3 (Apo-E3) promoted microglial Aβ uptake. As Tat has been shown to directly interact with the low density lipoprotein (LRP) receptor and thus inhibit the uptake of its ligands including apolipoprotein E4 (Apo-E4) and Aβ peptide in neurons, we further hypothesize that a similar inhibition of LRP may occur in microglia. Future studies will be required to fully characterize the mechanisms underlying IFN-γ enhancement of HIV-1 Tats disruption of microglial phagocytosis of Aβ and Apo-E3. PMID:18784813

  10. Interaction of Epstein-Barr Virus BZLF1 C-Terminal Tail Structure and Core Zipper Is Required for DNA Replication but Not for Promoter Transactivation

    PubMed Central

    McDonald, Carol M.; Petosa, Carlo; Farrell, Paul J.

    2009-01-01

    The Epstein-Barr virus (EBV) protein BZLF1 contains a bZIP DNA binding domain in which C-terminal tail residues fold back against a zipper region that forms a coiled coil and mediates dimerization. Point mutagenesis in the zipper region reveals the importance of individual residues within the 208SSENDRLR215 sequence that is conserved in C/EBP for transactivation and EBV DNA replication. The restoration of BZLF1 DNA replication activity by the complementation of two deleterious mutations (S208E and D236K) indicates that the interaction of the C-terminal tail and the core zipper is required for DNA replication, identifying a functional role for this structural feature unique to BZLF1. PMID:19144704

  11. Pur-1, a zinc-finger protein that binds to purine-rich sequences, transactivates an insulin promoter in heterologous cells.

    PubMed Central

    Kennedy, G C; Rutter, W J

    1992-01-01

    Purine-rich stretches of nucleotides (GAGA boxes) are often found just upstream of transcription start sites in many genes, including insulin. Mutational analysis suggests that the GAGA box plays an important role in transcription of the rat insulin I gene. We identify here at least four different proteins that bind specifically to the insulin GAGA box. Using a GAGA oligonucleotide, we have isolated a cDNA encoding a sequence-specific protein from a HIT (hamster insulinoma cell line) lambda gt11 library. This protein, which we designate Pur-1 (for purine binding), binds to the GAGA boxes of the rat insulin I and II genes and the human islet amyloid polypeptide gene. Pur-1 is a potent transactivator in both pancreatic and nonpancreatic cells. Furthermore, Pur-1 is able to activate an intact insulin promoter in HeLa cells, where it is normally inactive. Images PMID:1454839

  12. Activation of the human keratinocyte B1 bradykinin receptor induces expression and secretion of metalloproteases 2 and 9 by transactivation of epidermal growth factor receptor.

    PubMed

    Matus, Carola E; Ehrenfeld, Pamela; Pavicic, Francisca; González, Carlos B; Concha, Miguel; Bhoola, Kanti D; Burgos, Rafael A; Figueroa, Carlos D

    2016-09-01

    The B1 bradykinin receptor (BDKRB1) is a component of the kinin cascade localized in the human skin. Some of the effects produced by stimulation of BDKRB1 depend on transactivation of epidermal growth factor receptor (EGFR), but the mechanisms involved in this process have not been clarified yet. The primary purpose of this study was to determine the effect of a BDKRB1 agonist on wound healing in a mouse model and the migration and secretion of metalloproteases 2 and 9 from human HaCaT keratinocytes and delineate the signalling pathways that triggered their secretion. Although stimulation of BDKRB1 induces weak chemotactic migration of keratinocytes and wound closure in an in vitro scratch-wound assay, the BDKRB1 agonist improved wound closure in a mouse model. BDKRB1 stimulation triggers synthesis and secretion of both metalloproteases, effects that depend on the activity of EGFR and subsequent phosphorylation of ERK1/2 and p38 mitogen-activated protein kinases and PI3K/Akt. In the mouse model, immunoreactivity for both gelatinases was concentrated around wound borders. EGFR transactivation by BDKRB1 agonist involves Src kinases family and ADAM17. In addition to extracellular matrix degradation, metalloproteases 2 and 9 regulate cell migration and differentiation, cell functions that are associated with the role of BDKRB1 in keratinocyte differentiation. Considering that BDKRB1 is up-regulated by inflammation and/or by cytokines that are abundant in the inflammatory milieu, more stable BDKRB1 agonists may be of therapeutic value to modulate wound healing.

  13. Phosphorylation within the transactivation domain of adenovirus E1A protein by mitogen-activated protein kinase regulates expression of early region 4.

    PubMed Central

    Whalen, S G; Marcellus, R C; Whalen, A; Ahn, N G; Ricciardi, R P; Branton, P E

    1997-01-01

    A critical role of the 289-residue (289R) E1A protein of human adenovirus type 5 during productive infection is to transactivate expression of all early viral transcription. Sequences within and proximal to conserved region 3 (CR3) promote expression of these viral genes through interactions with a variety of transcription factors requiring the zinc binding motif in CR3 and in some cases a region at the carboxy-terminal end of CR3, including residues 183 to 188. It is known that 3',5' cyclic AMP (cAMP) reduces the level of phosphorylation of the 289R E1A protein through the activation of protein phosphatase 2A by the E4orf4 protein. This study was designed to identify the E1A phosphorylation sites affected by E4orf4 expression and to determine their importance in regulation of E1A activity. We report here that two previously unidentified sites at Ser-185 and Ser-188 are the targets for decreased phosphorylation in response to cAMP. At least one of these sites, presumably Ser-185, is phosphorylated in vitro by purified mitogen-activated protein kinase (MAPK), and both are hyperphosphorylated in cells which express a constitutively active form of MAPK kinase. Analysis of E1A-mediated transactivation activity indicated that elevated phosphorylation at these sites increased expression of the E4 promoter but not that of E3. We have recently shown that one or more E4 products induce cell death due to p53-independent apoptosis, and thus it seems likely that one role of the E4orf4 protein is to limit production of toxic E4 products by limiting expression of the E4 promoter. PMID:9094626

  14. Signaling from the Human Melanocortin 1 Receptor to ERK1 and ERK2 Mitogen-Activated Protein Kinases Involves Transactivation of cKIT

    PubMed Central

    Herraiz, Cecilia; Journé, Fabrice; Abdel-Malek, Zalfa; Ghanem, Ghanem; Jiménez-Cervantes, Celia; García-Borrón, José C.

    2011-01-01

    Melanocortin 1 receptor (MC1R), a Gs protein-coupled receptor expressed in melanocytes, is a major determinant of skin pigmentation, phototype and cancer risk. Upon stimulation by αMSH, MC1R triggers the cAMP and ERK1/ERK2 MAPK pathways. In mouse melanocytes, ERK activation by αMSH binding to Mc1r depends on cAMP, and melanocytes are considered a paradigm for cAMP-dependent ERK activation. However, human MC1R variants associated with red hair, fair skin [red hair color (RHC) phenotype], and increased skin cancer risk display reduced cAMP signaling but activate ERKs as efficiently as wild type in heterologous cells, suggesting independent signaling to ERKs and cAMP in human melanocytes. We show that MC1R signaling activated the ERK pathway in normal human melanocytes and melanoma cells expressing physiological levels of endogenous RHC variants. ERK activation was comparable for wild-type and mutant MC1R and was independent on cAMP because it was neither triggered by stimulation of cAMP synthesis with forskolin nor blocked by the adenylyl cyclase inhibitor 2′,5′-dideoxyadenosine. Stimulation of MC1R with αMSH did not lead to protein kinase C activation and ERK activation was unaffected by protein kinase C inhibitors. Conversely, pharmacological interference, small interfering RNA studies, expression profiles, and functional reconstitution experiments showed that αMSH-induced ERK activation resulted from Src tyrosine kinase-mediated transactivation of the stem cell factor receptor, a receptor tyrosine kinase essential for proliferation, differentiation, and survival of melanocyte precursors, thus demonstrating a functional link between the stem cell factor receptor and MC1R. Moreover, this transactivation phenomenon is unique because it is unaffected by natural mutations impairing canonical MC1R signaling through the cAMP pathway. PMID:21084381

  15. Krüppel-Like Factor 6 Expression Changes during Trophoblast Syncytialization and Transactivates ßhCG and PSG Placental Genes

    PubMed Central

    Racca, Ana C.; Camolotto, Soledad A.; Ridano, Magali E.; Bocco, José L.; Genti-Raimondi, Susana; Panzetta-Dutari, Graciela M.

    2011-01-01

    Background Krüppel-like factor-6 (KLF6) is a widely expressed member of the Sp1/KLF family of transcriptional regulators involved in differentiation, cell cycle control and proliferation in several cell systems. Even though the highest expression level of KLF6 has been detected in human and mice placenta, its function in trophoblast physiology is still unknown. Methodology/Principal Findings Herein, we explored KLF6 expression and sub-cellular distribution in human trophoblast cells differentiating into the syncytial pathway, and its role in the regulation of genes associated with placental development and pregnancy maintenance. Confocal immunofluorescence microscopy demonstrated that KLF6 is expressed throughout human cytotrophoblast differentiation showing no evident modifications in its nuclear and cytoplasmic localization pattern. KLF6 transcript and protein peaked early during the syncytialization process as determined by qRT-PCR and western blot assays. Overexpression of KLF6 in trophoblast-derived JEG-3 cells showed a preferential nuclear signal correlating with enhanced expression of human β-chorionic gonadotropin (βhCG) and pregnancy-specific glycoprotein (PSG) genes. Moreover, KLF6 transactivated βhCG5, PSG5 and PSG3 gene promoters. Deletion of KLF6 Zn-finger DNA binding domain or mutation of the consensus KLF6 binding site abolished transactivation of the PSG5 promoter. Conclusions/Significance Results are consistent with KLF6 playing a role as transcriptional regulator of relevant genes for placental differentiation and physiology such as βhCG and PSG, in agreement with an early and transient increase of KLF6 expression during trophoblast syncytialization. PMID:21799854

  16. Transactivation of a human cytomegalovirus early promoter by gene products from the immediate-early gene IE2 and augmentation by IE1: mutational analysis of the viral proteins.

    PubMed Central

    Malone, C L; Vesole, D H; Stinski, M F

    1990-01-01

    Expression from a human cytomegalovirus early promoter (E1.7) has been shown to be activated in trans by the IE2 gene products (C.-P. Chang, C. L. Malone, and M. F. Stinski, J. Virol. 63:281-290, 1989). Using wild-type and mutant viral proteins, we have defined the protein regions required for transactivation of the E1.7 promoter in IE2 and for augmentation of transactivation in the IE1 protein. Two regions of the IE2 proteins were found to be essential for transactivation. One near the amino terminus is within 52 amino acids encoded by exon 3. The second comprises the carboxyl-terminal 85 amino acids encoded by exon 5. The IE2 protein encoded by an mRNA which lacks the intron within exon 5 and the IE2 protein encoded by exon 5 had no activity for transactivation of the E1.7 promoter. Although the IE1 gene product alone had no effect on this early viral promoter, maximal early promoter activity was detected when both IE1 and IE2 gene products were present. The IE1 protein positively regulated its enhancer-containing promoter-regulatory region. The IE1 protein alone increased the steady-state level of IE2 mRNA; therefore, IE1 and IE2 are synergistic for expression from the E1.7 promoter. Like the IE2 proteins, the IE1 protein requires for activity 52 amino acids encoded by exon 3. IE1 also requires amino acids encoded by exon 4. Since the IE1 and IE2 proteins have 85 amino acids in common at the amino-terminal end encoded by exons 2 and 3, the difference between these specific transactivators resides in their carboxyl-terminal amino acids encoded by exons 4 and 5, respectively. Images PMID:2157038

  17. Cobaltous chloride and hypoxia inhibit aryl hydrocarbon receptor-mediated responses in breast cancer cells

    SciTech Connect

    Khan, Shaheen; Liu Shengxi; Stoner, Matthew; Safe, Stephen

    2007-08-15

    The aryl hydrocarbon receptor (AhR) is expressed in estrogen receptor (ER)-positive ZR-75 breast cancer cells. Treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1A1 protein and mRNA levels and also activates inhibitory AhR-ER{alpha} crosstalk associated with hormone-induced reporter gene expression. In ZR-75 cells grown under hypoxia, induction of these AhR-mediated responses by TCDD was significantly inhibited. This was not accompanied by decreased nuclear AhR levels or decreased interaction of the AhR complex with the CYP1A1 gene promoter as determined in a chromatin immunoprecipitation assay. Hypoxia-induced loss of Ah-responsiveness was not associated with induction of hypoxia-inducible factor-1{alpha} or other factors that sequester the AhR nuclear translocation (Arnt) protein, and overexpression of Arnt under hypoxia did not restore Ah-responsiveness. The p65 subunit of NF{kappa}B which inhibits AhR-mediated transactivation was not induced by hypoxia and was primarily cytosolic in ZR-75 cells grown under hypoxic and normoxic conditions. In ZR-75 cells maintained under hypoxic conditions for 24 h, BRCA1 (an enhancer of AhR-mediated transactivation in breast cancer cells) was significantly decreased and this contributed to loss of Ah-responsiveness. In cells grown under hypoxia for 6 h, BRCA1 was not decreased, but induction of CYP1A1 by TCDD was significantly decreased. Cotreatment of ZR-75 cells with TCDD plus the protein synthesis inhibitor cycloheximide for 6 h enhanced CYP1A1 expression in cells grown under hypoxia and normoxia. These results suggest that hypoxia rapidly induces protein(s) that inhibit Ah-responsiveness and these may be similar to constitutively expressed inhibitors of Ah-responsiveness (under normoxia) that are also inhibited by cycloheximide.

  18. Resveratrol inhibits LXRα-dependent hepatic lipogenesis through novel antioxidant Sestrin2 gene induction

    SciTech Connect

    Jin, So Hee; Yang, Ji Hye; Shin, Bo Yeon; Seo, Kyuhwa; Shin, Sang Mi; Cho, Il Je; Ki, Sung Hwan

    2013-08-15

    Liver X receptor-α (LXRα), a member of the nuclear receptor superfamily of ligand-activated transcription factors, regulates de novo fatty acid synthesis that leads to stimulate hepatic steatosis. Although, resveratrol has beneficial effects on metabolic disease, it is not known whether resveratrol affects LXRα-dependent lipogenic gene expression. This study investigated the effect of resveratrol in LXRα-mediated lipogenesis and the underlying molecular mechanism. Resveratrol inhibited the ability of LXRα to activate sterol regulatory element binding protein-1c (SREBP-1c) and thereby inhibited target gene expression in hepatocytes. Moreover, resveratrol decreased LXRα–RXRα DNA binding activity and LXRE-luciferase transactivation. Resveratrol is known to activate Sirtuin 1 (Sirt1) and AMP-activated protein kinase (AMPK), although its precise mechanism of action remains controversial. We found that the ability of resveratrol to repress T0901317-induced SREBP-1c expression was not dependent on AMPK and Sirt1. It is well established that hepatic steatosis is associated with antioxidant and redox signaling. Our data showing that expression of Sestrin2 (Sesn2), which is a novel antioxidant gene, was significantly down-regulated in the livers of high-fat diet-fed mice. Moreover, resveratrol up-regulated Sesn2 expression, but not Sesn1 and Sesn3. Sesn2 overexpression repressed LXRα-activated SREBP-1c expression and LXRE-luciferase activity. Finally, Sesn2 knockdown using siRNA abolished the effect of resveratrol in LXRα-induced FAS luciferase gene transactivation. We conclude that resveratrol affects Sesn2 gene induction and contributes to the inhibition of LXRα-mediated hepatic lipogenesis. - Highlights: • We investigated the effect of resveratrol in LXRα-mediated lipogenesis. • Resveratrol attenuated the ability of the LXRα-mediated lipogenic gene expression. • Resveratrol’s effects on T090-induced lipogenesis is not dependent on Sirt1 or AMPK.

  19. Heat Shock Enhances the Expression of the Human T Cell Leukemia Virus Type-I (HTLV-I) Trans-Activator (Tax) Antigen in Human HTLV-I Infected Primary and Cultured T Cells

    PubMed Central

    Kunihiro, Marie; Fujii, Hideki; Miyagi, Takuya; Takahashi, Yoshiaki; Tanaka, Reiko; Fukushima, Takuya; Ansari, Aftab A.; Tanaka, Yuetsu

    2016-01-01

    The environmental factors that lead to the reactivation of human T cell leukemia virus type-1 (HTLV-I) in latently infected T cells in vivo remain unknown. It has been previously shown that heat shock (HS) is a potent inducer of HTLV-I viral protein expression in long-term cultured cell lines. However, the precise HTLV-I protein(s) and mechanisms by which HS induces its effect remain ill-defined. We initiated these studies by first monitoring the levels of the trans-activator (Tax) protein induced by exposure of the HTLV-I infected cell line to HS. HS treatment at 43 °C for 30 min for 24 h led to marked increases in the level of Tax antigen expression in all HTLV-I-infected T cell lines tested including a number of HTLV-I-naturally infected T cell lines. HS also increased the expression of functional HTLV-I envelope gp46 antigen, as shown by increased syncytium formation activity. Interestingly, the enhancing effect of HS was partially inhibited by the addition of the heat shock protein 70 (HSP70)-inhibitor pifithlin-μ (PFT). In contrast, the HSP 70-inducer zerumbone (ZER) enhanced Tax expression in the absence of HS. These data suggest that HSP 70 is at least partially involved in HS-mediated stimulation of Tax expression. As expected, HS resulted in enhanced expression of the Tax-inducible host antigens, such as CD83 and OX40. Finally, we confirmed that HS enhanced the levels of Tax and gp46 antigen expression in primary human CD4+ T cells isolated from HTLV-I-infected humanized NOD/SCID/γc null (NOG) mice and HTLV-I carriers. In summary, the data presented herein indicate that HS is one of the environmental factors involved in the reactivation of HTLV-I in vivo via enhanced Tax expression, which may favor HTLV-I expansion in vivo. PMID:27409630

  20. Heat Shock Enhances the Expression of the Human T Cell Leukemia Virus Type-I (HTLV-I) Trans-Activator (Tax) Antigen in Human HTLV-I Infected Primary and Cultured T Cells.

    PubMed

    Kunihiro, Marie; Fujii, Hideki; Miyagi, Takuya; Takahashi, Yoshiaki; Tanaka, Reiko; Fukushima, Takuya; Ansari, Aftab A; Tanaka, Yuetsu

    2016-07-11

    The environmental factors that lead to the reactivation of human T cell leukemia virus type-1 (HTLV-I) in latently infected T cells in vivo remain unknown. It has been previously shown that heat shock (HS) is a potent inducer of HTLV-I viral protein expression in long-term cultured cell lines. However, the precise HTLV-I protein(s) and mechanisms by which HS induces its effect remain ill-defined. We initiated these studies by first monitoring the levels of the trans-activator (Tax) protein induced by exposure of the HTLV-I infected cell line to HS. HS treatment at 43 °C for 30 min for 24 h led to marked increases in the level of Tax antigen expression in all HTLV-I-infected T cell lines tested including a number of HTLV-I-naturally infected T cell lines. HS also increased the expression of functional HTLV-I envelope gp46 antigen, as shown by increased syncytium formation activity. Interestingly, the enhancing effect of HS was partially inhibited by the addition of the heat shock protein 70 (HSP70)-inhibitor pifithlin-μ (PFT). In contrast, the HSP 70-inducer zerumbone (ZER) enhanced Tax expression in the absence of HS. These data suggest that HSP 70 is at least partially involved in HS-mediated stimulation of Tax expression. As expected, HS resulted in enhanced expression of the Tax-inducible host antigens, such as CD83 and OX40. Finally, we confirmed that HS enhanced the levels of Tax and gp46 antigen expression in primary human CD4⁺ T cells isolated from HTLV-I-infected humanized NOD/SCID/γc null (NOG) mice and HTLV-I carriers. In summary, the data presented herein indicate that HS is one of the environmental factors involved in the reactivation of HTLV-I in vivo via enhanced Tax expression, which may favor HTLV-I expansion in vivo.

  1. Heat Shock Enhances the Expression of the Human T Cell Leukemia Virus Type-I (HTLV-I) Trans-Activator (Tax) Antigen in Human HTLV-I Infected Primary and Cultured T Cells.

    PubMed

    Kunihiro, Marie; Fujii, Hideki; Miyagi, Takuya; Takahashi, Yoshiaki; Tanaka, Reiko; Fukushima, Takuya; Ansari, Aftab A; Tanaka, Yuetsu

    2016-01-01

    The environmental factors that lead to the reactivation of human T cell leukemia virus type-1 (HTLV-I) in latently infected T cells in vivo remain unknown. It has been previously shown that heat shock (HS) is a potent inducer of HTLV-I viral protein expression in long-term cultured cell lines. However, the precise HTLV-I protein(s) and mechanisms by which HS induces its effect remain ill-defined. We initiated these studies by first monitoring the levels of the trans-activator (Tax) protein induced by exposure of the HTLV-I infected cell line to HS. HS treatment at 43 °C for 30 min for 24 h led to marked increases in the level of Tax antigen expression in all HTLV-I-infected T cell lines tested including a number of HTLV-I-naturally infected T cell lines. HS also increased the expression of functional HTLV-I envelope gp46 antigen, as shown by increased syncytium formation activity. Interestingly, the enhancing effect of HS was partially inhibited by the addition of the heat shock protein 70 (HSP70)-inhibitor pifithlin-μ (PFT). In contrast, the HSP 70-inducer zerumbone (ZER) enhanced Tax expression in the absence of HS. These data suggest that HSP 70 is at least partially involved in HS-mediated stimulation of Tax expression. As expected, HS resulted in enhanced expression of the Tax-inducible host antigens, such as CD83 and OX40. Finally, we confirmed that HS enhanced the levels of Tax and gp46 antigen expression in primary human CD4⁺ T cells isolated from HTLV-I-infected humanized NOD/SCID/γc null (NOG) mice and HTLV-I carriers. In summary, the data presented herein indicate that HS is one of the environmental factors involved in the reactivation of HTLV-I in vivo via enhanced Tax expression, which may favor HTLV-I expansion in vivo. PMID:27409630

  2. Ligand-Mediated cis-Inhibition of Receptor Signaling in the Self-Incompatibility Response of the Brassicaceae1[OPEN

    PubMed Central

    Tantikanjana, Titima; Nasrallah, June B.

    2015-01-01

    The inhibition of self-pollination in self-incompatible Brassicaceae is based on allele-specific trans-activation of the highly polymorphic S-locus receptor kinase (SRK), which is displayed at the surface of stigma epidermal cells, by its even more polymorphic pollen coat-localized ligand, the S-locus cysteine-rich (SCR) protein. In an attempt to achieve constitutive activation of SRK and thus facilitate analysis of self-incompatibility (SI) signaling, we coexpressed an Arabidopsis lyrata SCR variant with its cognate SRK receptor in the stigma epidermal cells of Arabidopsis (Arabidopsis thaliana) plants belonging to the C24 accession, in which expression of SRK and SCR had been shown to exhibit a robust SI response. Contrary to expectation, however, coexpression of SRK and SCR was found to inhibit SRK-mediated signaling and to disrupt the SI response. This phenomenon, called cis-inhibition, is well documented in metazoans but has not as yet been reported for plant receptor kinases. We demonstrate that cis-inhibition of SRK, like its trans-activation, is based on allele-specific interaction between receptor and ligand. We also show that stigma-expressed SCR causes entrapment of its SRK receptor in the endoplasmic reticulum, thus disrupting the proper targeting of SRK to the plasma membrane, where the receptor would be available for productive interaction with its pollen coat-derived SCR ligand. Although based on an artificial cis-inhibition system, the results suggest novel strategies of pollination control for the generation of hybrid cultivars and large-scale seed production from hybrid plants in Brassicaceae seed crops and, more generally, for inhibiting cell surface receptor function and manipulating signaling pathways in plants. PMID:26269543

  3. ZAP inhibits murine gammaherpesvirus 68 ORF64 expression and is antagonized by RTA.

    PubMed

    Xuan, Yifang; Gong, Danyang; Qi, Jing; Han, Chuanhui; Deng, Hongyu; Gao, Guangxia

    2013-03-01

    Zinc finger antiviral protein (ZAP) is an interferon-inducible host antiviral factor that specifically inhibits the replication of certain viruses, including HIV-1 and Ebola virus. ZAP functions as a dimer formed through intermolecular interactions of its N-terminal tails. ZAP binds directly to specific viral mRNAs and inhibits their expression by repressing translation and/or promoting degradation of the target mRNA. ZAP is not a universal antiviral factor, since some viruses grow normally in ZAP-expressing cells. It is not fully understood what determines whether a virus is susceptible to ZAP. We explored the interaction between ZAP and murine gammaherpesvirus 68 (MHV-68), whose life cycle has latent and lytic phases. We previously reported that ZAP inhibits the expression of M2, which is expressed mainly in the latent phase, and regulates MHV-68 latency in cultured cells. Here, we report that ZAP inhibits the expression of ORF64, a tegument protein that is expressed in the lytic phase and is essential for lytic replication. MHV-68 infection induced ZAP expression. However, ZAP did not inhibit lytic replication of MHV-68. We provide evidence showing that the antiviral activity of ZAP is antagonized by MHV-68 RTA, a critical viral transactivator expressed in the lytic phase. We further show that RTA inhibits the antiviral activity of ZAP by disrupting the N-terminal intermolecular interaction of ZAP. Our results provide an example of how a virus can escape ZAP-mediated immunity. PMID:23255809

  4. MYD88-independent growth and survival effects of Sp1 transactivation in Waldenström macroglobulinemia

    PubMed Central

    Fulciniti, Mariateresa; Amodio, Nicola; Bandi, Rajya Lakshmi; Munshi, Mansa; Yang, Guang; Xu, Lian; Hunter, Zachary; Tassone, Pierfrancesco; Anderson, Kenneth C.; Treon, Steven P.

    2014-01-01

    Sp1 transcription factor controls a pleiotropic group of genes and its aberrant activation has been reported in a number of malignancies, including multiple myeloma. In this study, we investigate and report its aberrant activation in Waldenström macroglobulinemia (WM). Both loss of and gain of Sp1 function studies have highlighted a potential oncogenic role of Sp1 in WM. We have further investigated the effect of a small molecule inhibitor, terameprocol (TMP), targeting Sp1 activity in WM. Treatment with TMP inhibited the growth and survival and impaired nuclear factor-κB and signal transducer and activator of transcription activity in WM cells. We next investigated and observed that TMP treatment induced further inhibition of WM cells in MYD88 knockdown WM cells. Moreover, we observed that Bruton’s tyrosine kinase, a downstream target of MYD88 signaling pathway, is transcriptionally regulated by Sp1 in WM cells. The combined use of TMP with Bruton’s tyrosine kinase or interleukin-1 receptor-associated kinase 1 and 4 inhibitors resulted in a significant and synergistic dose-dependent antiproliferative effect in MYD88-L265P–expressing WM cells. In summary, these results demonstrate Sp1 as an important transcription factor that regulates proliferation and survival of WM cells independent of MYD88 pathway activation, and provide preclinical rationale for clinical development of TMP in WM alone or in combination with inhibitors of MYD88 pathway. PMID:24622324

  5. Inhibition of androgen receptor (AR) function by the reproductive orphan nuclear receptor DAX-1.

    PubMed

    Holter, Elin; Kotaja, Noora; Mäkela, Sari; Strauss, Leena; Kietz, Silke; Jänne, Olli A; Gustafsson, Jan-Ake; Palvimo, Jorma J; Treuter, Eckardt

    2002-03-01

    DAX-1 (NROB1) is an atypical member of the nuclear receptor family that is predominantly expressed in mammalian reproductive tissues. While a receptor function of DAX-1 remains enigmatic, previous work has indicated that DAX-1 inhibits the activity of the orphan receptor steroidogenic factor 1 and the estrogen receptors (ERs), presumably via direct occupation of the coactivator-binding surface and subsequent recruitment of additional corepressors. In vivo evidence points at a particular role of DAX-1 for the development and maintenance of male reproductive functions. In this study, we have identified the androgen receptor (AR) NR3C4 as a novel target for DAX-1. We show that DAX-1 potently inhibits ligand-dependent transcriptional activation as well as the interaction between the N- and C-terminal activation domains of AR. We provide evidence for direct interactions of the two receptors that involve the N-terminal repeat domain of DAX-1 and the C-terminal ligand-binding and activation domain of AR. Moreover, DAX-1, known to shuttle between the cytoplasm and the nucleus, is capable of relocalizing AR in both cellular compartments, suggesting that intracellular tethering is associated with DAX-1 inhibition. These results implicate novel inhibitory mechanisms of DAX-1 action with particular relevance for the modulation of androgen-dependent gene transcription in the male reproductive system. PMID:11875111

  6. Estrogen Receptor β Activation Rapidly Modulates Male Sexual Motivation through the Transactivation of Metabotropic Glutamate Receptor 1a.

    PubMed

    Seredynski, Aurore L; Balthazart, Jacques; Ball, Gregory F; Cornil, Charlotte A

    2015-09-23

    In addition to the transcriptional activity of their liganded nuclear receptors, estrogens, such as estradiol (E2), modulate cell functions, and consequently physiology and behavior, within minutes through membrane-initiated events. The membrane-associated receptors (mERs) underlying the acute effects of estrogens on behavior have mostly been documented in females where active estrogens are thought to be of ovarian origin. We determined here, by acute intracerebroventricular injections of specific agonists and antagonists, the type(s) of mERs that modulate rapid effects of brain-derived estrogens on sexual motivation in male Japanese quail. Brain aromatase blockade acutely inhibited sexual motivation. Diarylpropionitrile (DPN), an estrogen receptor β (ERβ)-specific agonist, and to a lesser extent 17α-estradiol, possibly acting through ER-X, prevented this effect. In contrast, drugs targeting ERα (PPT and MPP), GPR30 (G1 and G15), and the Gq-mER (STX) did not affect sexual motivation. The mGluR1a antagonist LY367385 significantly inhibited sexual motivation but mGluR2/3 and mGluR5 antagonists were ineffective. LY367385 also blocked the behavioral restoration induced by E2 or DPN, providing functional evidence that ERβ interacts with metabotropic glutamate receptor 1a (mGluR1a) signaling to acutely regulate male sexual motivation. Together these results show that ERβ plays a key role in sexual behavior regulation and the recently uncovered cooperation between mERs and mGluRs is functional in males where it mediates the acute effects of estrogens produced centrally in response to social stimuli. The presence of an ER-mGluR interaction in birds suggests that this mechanism emerged relatively early in vertebrate history and is well conserved. Significance statement: The membrane-associated receptors underlying the acute effects of estrogens on behavior have mostly been documented in females, where active estrogens are thought to be of ovarian origin. Using acute

  7. Src Is a Potential Therapeutic Target in Endocrine-Resistant Breast Cancer Exhibiting Low Estrogen Receptor-Mediated Transactivation

    PubMed Central

    Pancholi, Sunil; Nikitorowicz-Buniak, Joanna; Simigdala, Nikiana; Dowsett, Mitch; Johnston, Stephen R.; Martin, Lesley-Ann

    2016-01-01

    Despite the effectiveness of endocrine therapies in estrogen receptor positive (ER+) breast cancer, approximately 40% of patients relapse. Previously, we identified the Focal-adhesion kinase canonical pathway as a major contributor of resistance to estrogen deprivation and cellular-sarcoma kinase (c-src) as a dominant gene in this pathway. Dasatinib, a pan-src inhibitor, has recently been used in clinical trials to treat ER+ patients but has shown mixed success. In the following study, using isogenic cell line models, we provide a potential explanation for these findings and suggest a sub-group that may benefit. A panel of isogenic cell lines modelling resistance to aromatase inhibitors (LTED) and tamoxifen (TAMR) were assessed for response to dasatinib ± endocrine therapy. Dasatinib caused a dose-dependent decrease in proliferation in MCF7-TAMR cells and resensitized them to tamoxifen and fulvestrant but not in HCC1428-TAMR. In contrast, in estrogen-deprived conditions, dasatinib increased the proliferation rate of parental-MCF7 cells and had no effect on MCF7-LTED or HCC1428-LTED. Treatment with dasatinib caused a decrease in src-phosphorylation and inhibition of downstream pathways, including AKT and ERK1/2 in all cell lines tested, but only the MCF7-TAMR showed a concomitant decrease in markers of cell cycle progression. Inhibition of src also caused a significant decrease in cell migration in both MCF7-LTED and MCF7-TAMR cells. Finally, we showed that, in MCF7-TAMR cells, in contrast to tamoxifen sensitive cell lines, ER is expressed throughout the cell rather than being restricted to the nucleus and that treatment with dasatinib resulted in nuclear shuttling of ER, which was associated with an increase in ER-mediated transcription. These data suggest that src has differential effects in endocrine-resistant cell lines, particularly in tamoxifen resistant models, with low ER genomic activity, providing further evidence of the importance of patient selection

  8. A poliovirus 2A(pro) mutant unable to cleave 3CD shows inefficient viral protein synthesis and transactivation defects.

    PubMed Central

    Ventoso, I; Carrasco, L

    1995-01-01

    Four poliovirus mutants with modifications of tyrosine 88 in 2A(pro) were generated and introduced into the cloned poliovirus genome. Mutants Y88P and Y88L were nonviable, mutant Y88F showed a wild-type (WT) phenotype, and mutant Y88S showed a delayed cytopathic effect and formed small plaques in HeLa cells. Growth of Y88S in HeLa cells was restricted, giving rise to about 20% of the PFU production of the WT poliovirus. The 2A (Y88S) mutant synthesized significantly lower levels of viral proteins in HeLa cells than did the WT poliovirus, while the kinetics of p220 cleavage were identical for both viruses. Strikingly, the 2A (Y88S) mutant was unable to cleave 3CD, as shown by analysis of poliovirus proteins labeled with [35S]methionine or immunoblotted with a specific anti-3C serum. The ability of the Y88S mutant to form infectious virus and cleave 3CD can be complemented by the WT poliovirus. Synthesis of viral RNA was diminished in the Y88S mutant but less than the inhibition of translation of viral RNA. Experiments in which guanidine was used to inhibit poliovirus RNA synthesis suggest that the primary defect of the Y88S mutant virus is at the level of poliovirus RNA translation, while viral genome replication is much less affected. Transfection of HeLa cells infected with the WT poliovirus with a luciferase mRNA containing the poliovirus 5' untranslated sequence gives rise to a severalfold increase in luciferase activity. This enhanced translation of leader-luc mRNA was not observed when the transfected cells were infected with the 2A (Y88S) mutant. Moreover, cotransfection with mRNA encoding WT poliovirus 2A(pro) enhanced translation of leader-luc mRNA. This enhancement was much lower upon transfection with mRNA encoding 2A(Y88S), 2A(Y88L), or 2A(Y88P). These findings support the view that 2A(pro) itself, rather than the 3C' and/or 3D' products, is necessary for efficient translation of poliovirus RNA in HeLa cells. PMID:7666528

  9. The central acidic domain of MDM2 is critical in inhibition of retinoblastoma-mediated suppression of E2F and cell growth.

    PubMed

    Sdek, Patima; Ying, Haoqiang; Zheng, Hongwu; Margulis, Alexander; Tang, Xiaoren; Tian, Kui; Xiao, Zhi-Xiong Jim

    2004-12-17

    Retinoblastoma (Rb) protein is a paradigm of tumor suppressors. Inactivation of Rb plays a critical role in the development of human malignancies. MDM2, an oncogene frequently found amplified and overexpressed in a variety of human tumors and cancers, directly interacts and inhibits the p53 tumor suppressor protein. In addition, MDM2 has been shown to stimulate E2F transactivation activity and promote S-phase entry independent of p53, yet the mechanism of which is still not fully understood. In this study, we demonstrate that MDM2 specifically binds to Rb C-pocket and that the central acidic domain of MDM2 is essential for Rb interaction. In addition, we show that overexpression of MDM2 reduces Rb-E2F complexes in vivo. Moreover, the ectopic expression of the wild type MDM2, but not mutant MDM2 defective in Rb interaction, stimulates E2F transactivation activity and inhibits Rb growth suppression function. Taken together, these results suggest that MDM2-mediated inhibition of Rb likely contributes to MDM2 oncogenic activity. PMID:15485814

  10. Inhibition of pregnane X receptor pathway contributes to the cell growth inhibition and apoptosis of anticancer agents in ovarian cancer cells.

    PubMed

    Masuyama, Hisashi; Nakamura, Keiichiro; Nobumoto, Etsuko; Hiramatsu, Yuji

    2016-09-01

    Epithelial ovarian cancer remains the most devastating gynecologic cancer with drug resistance and rapid recurrence. Pregnane X receptor (PXR) is a nuclear receptor that affects drug metabolism/efflux and drug-drug interaction through control of multiple drug resistance 1 (MDR1), which implies a major role in multidrug resistance, and other genes. We examined whether the inhibition of PXR-mediated pathway using siRNA interference and an antagonist for PXR could influence the paclitaxel and cisplatin cytotoxicity in ovarian cancer cells. PXR agonists, phthalate and pregnenolone had significant positive effects on cytochrome P450 (CYP) 3A4 expression and PXR-mediated transcription through the CYP3A4 promoter, whereas MDR1 expression and PXR-mediated transcription though the MDR1 promoter were significantly increased in the presence of paclitaxel or cisplatin. Downregulation of PXR suppressed the augmented MDR1 expression and PXR-mediated transcription by PXR ligands, and significantly enhanced cell growth inhibition and apoptosis in the presence of paclitaxel or cisplatin. Additionally, ketoconazole, a PXR antagonist, suppressed the augmented MDR1 expression and PXR-mediated transactivation by paclitaxel and cisplatin, and enhanced cell growth inhibition and apoptosis in their presence. In conclusion, inhibition of PXR-mediated pathways could be a novel means of augmenting sensitivity, or overcoming resistance to anticancer agents for ovarian cancer. PMID:27572875

  11. Copper depletion inhibits CoCl2-induced aggressive phenotype of MCF-7 cells via downregulation of HIF-1 and inhibition of Snail/Twist-mediated epithelial-mesenchymal transition.

    PubMed

    Li, Shun; Zhang, Jing; Yang, Hong; Wu, Chunhui; Dang, Xitong; Liu, Yiyao

    2015-01-01

    Copper, a strictly regulated trace element, is essential for many physiological processes including angiogenesis. Dysregulated angiogenesis has been associated with increased copper in tumors, and thus copper chelators have been used to inhibit tumor angiogenesis. However, it remains unclear whether copper has any effect on epithelial-mesenchymal transition (EMT). Using CoCl2-induced EMT of human breast carcinoma MCF-7 cells, we found that TEPA, a copper chelator, inhibited EMT-like cell morphology and cytoskeleton arrangement triggered by CoCl2; decreased the expression of vimentin and fibronectin, markers typical of EMT; inhibited HIF-1 activation and HIF1-α accumulation in nuclear; and down-regulated the expression of hypoxia-associated transcription factors, Snail and Twist1. Moreover, knockdown copper transport protein, Ctr1, also inhibited CoCl2-induced EMT and reversed the mesenchymal phenotype. In EMT6 xenograft mouse models, TEPA administration inhibited the tumor growth and increased mice survival. Immunohistochemical analysis of the xenograft further demonstrated that TEPA administration significantly inhibited tumor angiogenesis, down-regulated hypoxia-induced transcription factors, Snail and Twist1, leading to decreased transactivation of EMT-associated marker genes, vimentin and fibronectin. These results indicate that TEPA inhibits CoCl2-induced EMT most likely via HIF1-α-Snail/Twist signaling pathway, and copper depletion may be exploited as a therapeutic for breast cancer. PMID:26174737

  12. Copper depletion inhibits CoCl2-induced aggressive phenotype of MCF-7 cells via downregulation of HIF-1 and inhibition of Snail/Twist-mediated epithelial-mesenchymal transition.

    PubMed

    Li, Shun; Zhang, Jing; Yang, Hong; Wu, Chunhui; Dang, Xitong; Liu, Yiyao

    2015-07-15

    Copper, a strictly regulated trace element, is essential for many physiological processes including angiogenesis. Dysregulated angiogenesis has been associated with increased copper in tumors, and thus copper chelators have been used to inhibit tumor angiogenesis. However, it remains unclear whether copper has any effect on epithelial-mesenchymal transition (EMT). Using CoCl2-induced EMT of human breast carcinoma MCF-7 cells, we found that TEPA, a copper chelator, inhibited EMT-like cell morphology and cytoskeleton arrangement triggered by CoCl2; decreased the expression of vimentin and fibronectin, markers typical of EMT; inhibited HIF-1 activation and HIF1-α accumulation in nuclear; and down-regulated the expression of hypoxia-associated transcription factors, Snail and Twist1. Moreover, knockdown copper transport protein, Ctr1, also inhibited CoCl2-induced EMT and reversed the mesenchymal phenotype. In EMT6 xenograft mouse models, TEPA administration inhibited the tumor growth and increased mice survival. Immunohistochemical analysis of the xenograft further demonstrated that TEPA administration significantly inhibited tumor angiogenesis, down-regulated hypoxia-induced transcription factors, Snail and Twist1, leading to decreased transactivation of EMT-associated marker genes, vimentin and fibronectin. These results indicate that TEPA inhibits CoCl2-induced EMT most likely via HIF1-α-Snail/Twist signaling pathway, and copper depletion may be exploited as a therapeutic for breast cancer.

  13. Role of protein kinase A in tax transactivation of the human T-cell leukemia virus type I long terminal repeat.

    PubMed Central

    Kadison, P; Poteat, H T; Klein, K M; Faller, D V

    1990-01-01

    The human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR) is inducible both by the retroviral tax gene product and by cyclic AMP in the murine thymoma S49 cell line. The cis-acting sequences that control transcriptional induction by tax and by cyclic AMP are in close proximity within the HTLV-I promoter. By using a protein kinase A (PKA)-deficient S49 mutant cell line, the response of the viral promoter to cyclic AMP was shown to depend on PKA, whereas the response to tax did not require the activity of this enzyme. Transactivation of the HTLV-I LTR by tax, however, decreased in PKA-deficient and adenylate cyclase-deficient cells. The evidence presented supports largely independent mechanisms of promoter induction by cyclic AMP and tax but also suggests a role for PKA-mediated phosphorylation in the regulation of HTLV-I LTR-driven gene expression by tax. Images PMID:2157876

  14. The class II transactivator (CIITA) is regulated by post-translational modification cross-talk between ERK1/2 phosphorylation, mono-ubiquitination and Lys63 ubiquitination.

    PubMed

    Morgan, Julie E; Shanderson, Ronald L; Boyd, Nathaniel H; Cacan, Ercan; Greer, Susanna F

    2015-06-19

    The class II transactivator (CIITA) is known as the master regulator for the major histocompatibility class II (MHC II) molecules. CIITA is dynamically regulated through a series of intricate post-translational modifications (PTMs). CIITA's role is to initiate transcription of MHC II genes, which are responsible for presenting extracellular antigen to CD4(+) T-cells. In the present study, we identified extracellular signal-regulated kinase (ERK)1/2 as the kinase responsible for phosphorylating the regulatory site, Ser(280), which leads to increased levels of mono-ubiquitination and an overall increase in MHC II activity. Further, we identify that CIITA is also modified by Lys(63)-linked ubiquitination. Lys(63) ubiquitinated CIITA is concentrated in the cytoplasm and following activation of ERK1/2, CIITA phosphorylation occurs and Lys=ubiquitinated CIITA translocates to the nucleus. CIITA ubiquitination and phosphorylation perfectly demonstrates how CIITA location and activity is regulated through PTM cross-talk. Identifying CIITA PTMs and understanding how they mediate CIITA regulation is necessary due to the critical role CIITA has in the initiation of the adaptive immune response.

  15. CBF mediates adenovirus Ela trans-activation by interaction at the C-terminal promoter targeting domain of conserved region 3.

    PubMed

    Agoff, S N; Wu, B

    1994-12-01

    Genetic and biochemical evidence suggest that conserved region 3 (CR3) of the adenovirus Ela polypeptide can provide two distinct and separable functions: an N-terminal transcriptional activation region and a C-terminal promoter targeting region. It is thought that the promoter targeting region of Ela CR3 interacts with promoter-specific transcription factors, thereby bringing the activation region of Ela CR3 in proximity of the promoter. Here we report that CBF, a CCAAT-box-binding factor that regulates hsp70 gene expression and mediates Ela trans-activation in vivo, interacts with the promoter targeting region of Ela CR3 in vitro. Point mutations in Ela CR3 that are defective in stimulating transcription from the hsp70 promoter are also defective in stimulating transcription directed by a synthetic activator, GAL-CBF, composed of the DNA-binding domain of yeast GAL4 fused to CBF. These mutations fall into two classes with respect to their abilities to interact with CBF in vitro. Mutations in the transcriptional activation region of Ela CR3 do not affect binding to CBF, but mutation of the promoter targeting region of Ela CR3 prevents association with CBF in vitro.

  16. Collaborative interaction of Oct-2 with Oct-1 in transactivation of lactogenic hormones-induced β-casein gene expression in mammary epithelial cells.

    PubMed

    Qian, Xi; Zhao, Feng-Qi

    2014-08-01

    Octamer-binding transcription factor-1 (Oct-1) is found to mediate lactogenic hormones (prolactin and glucocorticoids, HP)-induced β-casein gene expression in mammary alveolar secretory epithelial cells (MECs). The mammary gland also expresses Oct-2 isoform. In this study, we show that Oct-2 is also involved in HP-induced β-casein expression. Oct-2 endogenously binds to the β-casein promoter in MECs, and HP induce Oct-2 binding activity via mechanisms other than increasing Oct-2 expression or inducing Oct-2 translocation to the nucleus. Oct-2 transactivates HP-induced β-casein gene expression and this function is exchangeable with Oct-1. In MECs, Oct-2 is found to physically interact with Oct-1 regardless of HP treatment. However, HP induce physical interactions of Oct-2 with both signal transducer and activator of transcription 5 (STAT5) and glucocorticoid receptor (GR). These results provided biochemical evidence that Oct-2 may form a heteromer with Oct-1 in induction of β-casein gene expression by HP in MECs.

  17. The high affinity ligand binding conformation of the nuclear 1,25-dihydroxyvitamin D3 receptor is functionally linked to the transactivation domain 2 (AF-2).

    PubMed Central

    Nayeri, S; Kahlen, J P; Carlberg, C

    1996-01-01

    The nuclear receptor for 1,25-dihydroxyvitamin D3 (VD), VDR, is a transcription factor that mediates all genomic actions of the hormone. The activation of VDR by ligand induces a conformational change within its ligand binding domain (LBD). Due to the lack of a crystal structure analysis, biochemical methods have to be applied in order to investigate the details of this receptor-ligand interaction. The limited protease digestion assay can be used as a tool for the determination of a functional dissociation constant (K(df)) of VDR with any potential ligand. This method provided with the natural hormone VD two protease-resistant fragments of the VDR LBD and with the 20-epi conformation of VD, known as MC1288, even an additional fragment of intermediate size. These fragments were interpreted as different receptor conformations and their decreasing size was found to be associated with decreasing ligand binding affinity. A critical amino acid for VDR's high ligand binding conformation has been identified by C-terminal receptor truncations and point mutations as phenylalanine 422. This amino acid appears to directly contact the ligand and belongs to the ligand-inducible activation function-2 (AF-2) domain. Moreover, functional assays supported the observation that high affinity ligand binding is directly linked to transactivation function. PMID:8948643

  18. Ghrelin promotes intestinal epithelial cell proliferation through PI3K/Akt pathway and EGFR trans-activation both converging to ERK 1/2 phosphorylation.

    PubMed

    Waseem, Talat; Duxbury, Mark; Ashley, Stanley W; Robinson, Malcolm K

    2014-02-01

    Little is known about ghrelin's effects on intestinal epithelial cells even though it is known to be a mitogen for a variety of other cell types. Because ghrelin is released in close proximity to the proliferative compartment of the intestinal tract, we hypothesized that ghrelin may have potent pro-proliferative effect on intestinal epithelial cells as well. To test this hypothesis, we characterized the effects of ghrelin on FHs74Int and Caco-2 intestinal epithelial cell lines in vitro. We found that ghrelin has potent dose dependent proliferative effects in both cell lines through a yet to be characterized G protein coupled growth hormone secretagogue receptor (GHS-R) subtype. Consistent with above findings, cell cycle flowcytometric analyses demonstrated that ghrelin shifts cells from the G1 to S phase and thereby promotes cell cycle progression. Further characterization of subcellular events, suggested that ghrelin mediates its pro-proliferative effect through Adenylate cyclase (AC)-independent epidermal growth factor receptor (EGFR) trans-activation and PI3K-Akt phosphorylation. Both these pathways converge to stimulate MAPK, ERK 1/2 downstream. The role of ghrelin in states where intestinal mucosal injury and rapid mucosal repair occur warrants further investigation.

  19. The C-terminal domain of the nuclear factor I-B2 isoform is glycosylated and transactivates the WAP gene in the JEG-3 cells

    SciTech Connect

    Mukhopadhyay, Sudit S. . E-mail: suditmukhopadhy@yahoo.com; Rosen, Jeffrey M. . E-mail: jrosen@bcm.tmc.edu

    2007-07-06

    The transcription factor nuclear factor I (NFI) has been shown previously both in vivo and in vitro to be involved in the cooperative regulation of whey acidic protein (WAP) gene transcription along with the glucocorticoid receptor and STAT5. In addition, one of the specific NFI isoforms, NFI-B2, was demonstrated in transient co-transfection experiments in JEG cells, which lack endogenous NFI, to be preferentially involved in the cooperative regulation of WAP gene expression. A comparison of the DNA-binding specificities of the different NFI isoforms only partially explained their differential ability to activate the WAP gene transcription. Here, we analyzed the transactivation regions of two NFI isoforms by making chimeric proteins between the NFI-A and B isoforms. Though, their DNA-binding specificities were not altered as compared to the corresponding wild-type transcription factors, the C-terminal region of the NFI-B isoform was shown to preferentially activate WAP gene transcription in cooperation with GR and STAT5 in transient co-transfection assays in JEG-3 cells. Furthermore, determination of serine and threonine-specific glycosylation (O-linked N-acetylglucosamine) of the C-terminus of the NFI-B isoform suggested that the secondary modification by O-GlcNAc might play a role in the cooperative regulation of WAP gene transcription by NFI-B2 and STAT5.

  20. Development of a Fish Cell Biosensor System for Genotoxicity Detection Based on DNA Damage-Induced Trans-Activation of p21 Gene Expression

    PubMed Central

    Geng, Deyu; Zhang, Zhixia; Guo, Huarong

    2012-01-01

    p21CIP1/WAF1 is a p53-target gene in response to cellular DNA damage. Here we report the development of a fish cell biosensor system for high throughput genotoxicity detection of new drugs, by stably integrating two reporter plasmids of pGL3-p21-luc (human p21 promoter linked to firefly luciferase) and pRL-CMV-luc (CMV promoter linked to Renilla luciferase) into marine flatfish flounder gill (FG) cells, referred to as p21FGLuc. Initial validation of this genotoxicity biosensor system showed that p21FGLuc cells had a wild-type p53 signaling pathway and responded positively to the challenge of both directly acting genotoxic agents (bleomycin and mitomycin C) and indirectly acting genotoxic agents (cyclophosphamide with metabolic activation), but negatively to cyclophosphamide without metabolic activation and the non-genotoxic agents ethanol and D-mannitol, thus confirming a high specificity and sensitivity, fast and stable response to genotoxic agents for this easily maintained fish cell biosensor system. This system was especially useful in the genotoxicity detection of Di(2-ethylhexyl) phthalate (DEHP), a rodent carcinogen, but negatively reported in most non-mammalian in vitro mutation assays, by providing a strong indication of genotoxicity for DEHP. A limitation for this biosensor system was that it might give false positive results in response to sodium butyrate and any other agents, which can trans-activate the p21 gene in a p53-independent manner. PMID:25585933

  1. G9a is transactivated by C/EBPβ to facilitate mitotic clonal expansion during 3T3-L1 preadipocyte differentiation.

    PubMed

    Li, Shu-Fen; Guo, Liang; Qian, Shu-Wen; Liu, Yuan; Zhang, You-You; Zhang, Zhi-Chun; Zhao, Yue; Shou, Jian-Yong; Tang, Qi-Qun; Li, Xi

    2013-05-01

    In 3T3-L1 preadipocyte differentiation, the CCAAT/enhancer-binding protein-β (C/EBPβ) is an important early transcription factor that activates cell cycle genes during mitotic clonal expansion (MCE), sequentially activating peroxisome proliferator-activated receptor-γ (PPARγ) and C/EBPα during terminal differentiation. Although C/EBPβ acquires its DNA binding activity via dual phosphorylation at about 12-16 h postinduction, the expression of PPARγ and C/EBPα is not induced until 36-72 h. The delayed expression of PPARγ and C/EBPα ensures the progression of MCE, but the mechanism responsible for the delay remains elusive. We provide evidence that G9a, a major euchromatic methyltransferase, is transactivated by C/EBPβ and represses PPARγ and C/EBPα through H3K9 dimethylation of their promoters during MCE. Inhibitor- or siRNA-mediated G9a downregulation modestly enhances PPARγ and C/EBPα expression and adipogenesis in 3T3-L1 preadipocytes. Conversely, forced expression of G9a impairs the accumulation of triglycerides. Thus, this study elucidates an epigenetic mechanism for the delayed expression of PPARγ and C/EBPα.

  2. Analysis of p53 transactivation domain mutants reveals Acad11 as a metabolic target important for p53 pro-survival function

    PubMed Central

    Jiang, Dadi; LaGory, Edward L.; Brož, Daniela Kenzelmann; Bieging, Kathryn T.; Brady, Colleen A.; Link, Nichole; Abrams, John M.; Giaccia, Amato J.; Attardi, Laura D.

    2015-01-01

    SUMMARY The p53 tumor suppressor plays a key role in maintaining cellular integrity. In response to diverse stress signals, p53 can trigger apoptosis to eliminate damaged cells or cell-cycle arrest to enable cells to cope with stress and survive. However, the transcriptional networks underlying p53 pro-survival function are incompletely understood. Here, we show that in oncogenic-Ras-expressing cells, p53 promotes oxidative phosphorylation (OXPHOS) and cell survival upon glucose starvation. Analysis of p53 transcriptional activation domain mutants reveals that these responses depend on p53 transactivation function. Using gene expression profiling and ChIP-seq analysis, we identify several p53-inducible fatty acid metabolism-related genes. One such gene, Acad11, encoding a protein involved in fatty acid oxidation, is required for efficient OXPHOS and cell survival upon glucose starvation. This study provides new mechanistic insight into the pro-survival function of p53 and suggests that targeting this pathway may provide a strategy for therapeutic intervention based on metabolic perturbation. PMID:25704813

  3. Stromal cell-derived factor-1{alpha} (SDF-1{alpha}/CXCL12) stimulates ovarian cancer cell growth through the EGF receptor transactivation

    SciTech Connect

    Porcile, Carola; Bajetto, Adriana . E-mail: bajetto@cba.unige.it; Barbieri, Federica; Barbero, Simone; Bonavia, Rudy; Biglieri, Marianna; Pirani, Paolo; Florio, Tullio . E-mail: florio@cba.unige.it; Schettini, Gennaro

    2005-08-15

    Ovarian cancer (OC) is the leading cause of death in gynecologic diseases in which there is evidence for a complex chemokine network. Chemokines are a family of proteins that play an important role in tumor progression influencing cell proliferation, angiogenic/angiostatic processes, cell migration and metastasis, and, finally, regulating the immune cells recruitment into the tumor mass. We previously demonstrated that astrocytes and glioblastoma cells express both the chemokine receptor CXCR4 and its ligand stromal cell-derived factor-1 (SDF-1), and that SDF-1{alpha} treatment induced cell proliferation, supporting the hypothesis that chemokines may play an important role in tumor cells' growth in vitro. In the present study, we report that CXCR4 and SDF-1 are expressed in OC cell lines. We demonstrate that SDF-1{alpha} induces a dose-dependent proliferation in OC cells, by the specific interaction with CXCR4 and a biphasic activation of ERK1/2 and Akt kinases. Our results further indicate that CXCR4 activation induces EGF receptor (EGFR) phosphorylation that in turn was linked to the downstream intracellular kinases activation, ERK1/2 and Akt. In addition, we provide evidence for cytoplasmic tyrosine kinase (c-Src) involvement in the SDF-1/CXCR4-EGFR transactivation. These results suggest a possible important 'cross-talk' between SDF-1/CXCR4 and EGFR intracellular pathways that may link signals of cell proliferation in ovarian cancer.

  4. The histone acetyltransferase domains of CREB-binding protein (CBP) and p300/CBP-associated factor are not necessary for cooperativity with the class II transactivator.

    PubMed

    Harton, J A; Zika, E; Ting, J P

    2001-10-19

    The class II transactivator (CIITA) is a transcriptional co-activator regulating the constitutive and interferon-gamma-inducible expression of class II major histocompatibility complex (MHC) and related genes. Promoter remodeling occurs following CIITA induction, suggesting the involvement of chromatin remodeling factors. Transcription of numerous genes requires the histone acetyltransferase (HAT) activities of CREB-binding protein (CBP), p300, and/or p300/CBP-associated factor (pCAF). These co-activators cooperate with CIITA and are hypothesized to promote class II major histocompatibility complex transcription through their HAT activity. To directly test this, we used HAT-defective CBP and pCAF. We demonstrate that cooperation between CIITA and CBP is independent of CBP HAT activity. Further, although pCAF enhances CIITA-mediated transcription, pCAF HAT domain dependence appears contingent upon the concentration of available CIITA. When HAT-defective CBP and pCAF are both present, cooperativity with CIITA is maintained. Consistent with a recent report, we show that nuclear localization of CIITA is enhanced by lysine 144, an in vitro target of pCAF-mediated HAT. Yet we find that neither mutation of lysine 144 nor deletion of residues 132-209 affects transcriptional cooperation with CBP or pCAF. Thus, acetylation of this residue may not be the primary mechanism for pCAF/CBP cooperation with CIITA. In conclusion, the HAT activities of the co-activators are not necessary for cooperation with CIITA.

  5. Whole-genome analysis of genetic recombination of hepatitis delta virus: molecular domain in delta antigen determining trans-activating efficiency.

    PubMed

    Chao, Mei; Lin, Chia-Chi; Lin, Feng-Ming; Li, Hsin-Pai; Iang, Shan-Bei

    2015-12-01

    Hepatitis delta virus (HDV) is the only animal RNA virus that has an unbranched rod-like genome with ribozyme activity and is replicated by host RNA polymerase. HDV RNA recombination was previously demonstrated in patients and in cultured cells by analysis of a region corresponding to the C terminus of the delta antigen (HDAg), the only viral-encoded protein. Here, a whole-genome recombination map of HDV was constructed using an experimental system in which two HDV-1 sequences were co-transfected into cultured cells and the recombinants were analysed by sequencing of cloned reverse transcription-PCR products. Fifty homologous recombinants with 60 crossovers mapping to 22 junctions were identified from 200 analysed clones. Small HDAg chimeras harbouring a junction newly detected in the recombination map were then constructed. The results further indicated that the genome-replication level of HDV was sensitive to the sixth amino acid within the N-terminal 22 aa of HDAg. Therefore, the recombination map established in this study provided a tool for not only understanding HDV RNA recombination, but also elucidating the related mechanisms, such as molecular elements responsible for the trans-activation levels of the small HDAg.

  6. Transactivation of the p21 promoter by BRCA1 splice variants in mammary epithelial cells: evidence for both common and distinct activities of wildtype and mutant forms.

    PubMed

    Lu, M; Arrick, B A

    2000-12-14

    We have evaluated the transcriptional activation of a human p21 promoter reporter construct by transfection of BRCA1 expression constructs into tumorigenic and nontumorigenic human breast cell lines. Two cell lines with wildtype p53 (MCF-7 and MCF10A) demonstrated transcriptional activation of the p21 promoter by full-length BRCA1 (BRCA1L) as well as by two splice variants that lack most of exon 11 (BRCA1S and BRCA1S-9,10). In contrast, two cell lines with mutant p53 (MDA-231 and HCC1937) were inactive. Co-transfection of BRCA1L with BRCA1S or BRCA1S-9,10 exhibited synergistic p21 promoter activation, due to augmented expression of the cytomegalovirus promoter-based BRCA1 expression constructs. We examined the transcriptional activity of two known sequence alterations in BRCA1, one that results in a carboxy-terminal truncation of BRCA1 and is clearly pathogenic, and the other a missense mutation that is suspected of predisposing to cancer. Although both mutations have been shown to be defective in some assays of transactivation, we observed both mutations to be fully active in activation of the p21 promoter when incorporated in the full-length BRCA1L. In contrast, these mutations rendered BRCA1S inactive. These observations indicate that such transcriptional assays cannot serve as the basis for a functional appraisal of BRCA1 sequence alterations encountered in the course of genetic testing.

  7. Macrophage migration inhibitory factor interacts with HBx and inhibits its apoptotic activity

    SciTech Connect

    Zhang Shimeng; Lin Ruxian; Zhou Zhe; Wen Siyuan; Lin Li; Chen Suhong; Shan Yajun; Cong Yuwen; Wang Shengqi . E-mail: sqwang@nic.bmi.ac.cn

    2006-04-07

    HBx, a transcriptional transactivating protein of hepatitis B virus (HBV), is required for viral infection and has been implicated in virus-mediated liver oncogenesis. However, the precise molecular mechanism remains largely elusive. We used the yeast two-hybrid system to identify that HBx interacts with MIF directly. Macrophage migration inhibitory factor (MIF) is implicated in the regulation of inflammation, cell growth, and even tumor formation. The interaction between HBx and MIF was verified with co-immunoprecipitation, GST pull-down, and cellular colocalization. The expression of MIF was up-regulated in HBV particle producing cell 2.2.15 compared with HepG2 cell. Both HBx and MIF cause HepG2 cell G /G{sub 1} phase arrest, proliferation inhibition, and apoptosis. However, MIF can counteract the apoptotic effect of HBx. These results may provide evidence to explain the link between HBV infection and hepatocellular carcinoma.

  8. The dual action of poly(ADP-ribose) polymerase -1 (PARP-1) inhibition in HIV-1 infection: HIV-1 LTR inhibition and diminution in Rho GTPase activity

    PubMed Central

    Rom, Slava; Reichenbach, Nancy L.; Dykstra, Holly; Persidsky, Yuri

    2015-01-01

    Multifactorial mechanisms comprising countless cellular factors and virus-encoded transactivators regulate the transcription of HIV-1 (HIV). Since poly(ADP-ribose) polymerase 1 (PARP-1) regulates numerous genes through its interaction with various transcription factors, inhibition of PARP-1 has surfaced recently as a powerful anti-inflammatory tool. We suggest a novel tactic to diminish HIV replication via PARP-1 inhibition in an in vitro model system, exploiting human primary monocyte-derived macrophages (MDM). PARP-1 inhibition was capable to lessen HIV replication in MDM by 60–80% after 7 days infection. Tat, tumor necrosis factor α (TNFα), and phorbol 12-myristate 13-acetate (PMA) are known triggers of the Long Terminal Repeat (LTR), which can switch virus replication. Tat overexpression in MDM transfected with an LTR reporter plasmid resulted in a 4.2-fold increase in LTR activation; PARP inhibition caused 70% reduction of LTR activity. LTR activity, which increased 3-fold after PMA or TNFα treatment, was reduced by PARP inhibition (by 85–95%). PARP inhibition in MDM exhibited 90% diminution in NFκB activity (known to mediate TNFα- and PMA-induced HIV LTR activation). Cytoskeleton rearrangements are important in effective HIV-1 infection. PARP inactivation reduced actin cytoskeleton rearrangements by affecting Rho GTPase machinery. These discoveries suggest that inactivation of PARP suppresses HIV replication in MDM by via attenuation of LTR activation, NFκB suppression and its effects on the cytoskeleton. PARP appears to be essential for HIV replication and its inhibition may provide an effective approach to management of HIV infection. PMID:26379653

  9. Autocrine TGFbeta signaling mediates vitamin D3 analog-induced growth inhibition in breast cells.

    PubMed

    Yang, L; Yang, J; Venkateswarlu, S; Ko, T; Brattain, M G

    2001-09-01

    In this study, we address whether TGFbeta signaling mediates vitamin D3 analog-induced growth inhibition in nonmalignant and malignant breast cells. Normal mammary epithelial cells (184), immortalized nonmalignant mammary epithelial cells (184A1 and MCF10A), and breast cancer cells (early passage MCF7: MCF7E) were sensitive to the inhibitory effects of vitamin D3 analogs (EB1089 and MC1288) while late passage MCF7 breast cancer (MCF7L) cells were relatively resistant. A similar pattern of sensitivity to TGFbeta was observed with these cells. Thus, the sensitivity to the vitamin D3 analogs correlated with the sensitivity to TGFbeta. MCF7L TGFbetaRII-transfected cells, which have autocrine TGFbeta activity, were more sensitive to EB1089 than MCF7L cells. TGFbeta neutralizing antibody was found to block the inhibitory effects of these analogs. These results are consistent with the idea that autocrine TGFbeta signaling mediates the anti-proliferative effects of the vitamin D3 analogs in these cells. The expression of TGFbeta isoforms and/or TGFbeta receptors was induced by the analogs in the vitamin D3 and TGFbeta sensitive cells. Vitamin D3 analogs did not induce TGFbeta or TGFbeta receptor expression in the resistant MCF7L cells. Therefore, EB1089 induces autocrine TGFbeta activity through increasing expression of TGFbeta isoforms and/or TGFbeta receptors. In addition, EB1089 induced nuclear VDR protein levels in the sensitive 184A1 cells but not in the resistant MCF7L cells. 184A1 cells were more sensitive to EB1089-induced VDR-dependent transactivation than MCF7L cells as measured by a luciferase reporter construct containing the VDRE, indicating a defect of VDR signaling in MCF7L cells. Smad3, a TGFbeta signaling mediator, coactivated VDR-dependent transactivation in 184A1 cells but not in MCF7L cells. These results indicate that Smad3 coactivates VDR to further enhance TGFbeta signaling and vitamin D3 signaling in the sensitive 184A1 cells. The results also

  10. Corrosion inhibiting organic coatings

    SciTech Connect

    Sasson, E.

    1984-10-16

    A corrosion inhibiting coating comprises a mixture of waxes, petroleum jelly, a hardener and a solvent. In particular, a corrosion inhibiting coating comprises candelilla wax, carnauba wax, microcrystalline waxes, white petrolatum, an oleoresin, lanolin and a solvent.

  11. Human dominant-negative class II transactivator transgenic pigs - effect on the human anti-pig T-cell immune response and immune status.

    PubMed

    Hara, Hidetaka; Witt, William; Crossley, Tanner; Long, Cassandra; Isse, Kumiko; Fan, Liming; Phelps, Carol J; Ayares, David; Cooper, David K C; Dai, Yifan; Starzl, Thomas E

    2013-09-01

    Swine leucocyte antigen (SLA) class II molecules on porcine (p) cells play a crucial role in xenotransplantation as activators of recipient human CD4(+) T cells. A human dominant-negative mutant class II transactivator (CIITA-DN) transgene under a CAG promoter with an endothelium-specific Tie2 enhancer was constructed. CIITA-DN transgenic pigs were produced by nuclear transfer/embryo transfer. CIITA-DN pig cells were evaluated for expression of SLA class II with/without activation, and the human CD4(+) T-cell response to cells from CIITA-DN and wild-type (WT) pigs was compared. Lymphocyte subset numbers and T-cell function in CIITA-DN pigs were compared with those in WT pigs. The expression of SLA class II on antigen-presenting cells from CIITA-DN pigs was significantly reduced (40-50% reduction compared with WT; P < 0·01), and was completely suppressed on aortic endothelial cells (AECs) even after activation (100% suppression; P < 0·01). The human CD4(+) T-cell response to CIITA-DN pAECs was significantly weaker than to WT pAECs (60-80% suppression; P < 0·01). Although there was a significantly lower frequency of CD4(+) cells in the PBMCs from CIITA-DN (20%) than from WT (30%) pigs (P < 0·01), T-cell proliferation was similar, suggesting no significant immunological compromise. Organs and cells from CIITA-DN pigs should be partially protected from the human cellular immune response.

  12. The HNF-4/HNF-1α transactivation cascade regulates gene activity and chromatin structure of the human serine protease inhibitor gene cluster at 14q32.1

    PubMed Central

    Rollini, Pierre; Fournier, R. E. K.

    1999-01-01

    Hepatocyte-specific expression of the α1-antitrypsin (α1AT) gene requires the activities of two liver-enriched transactivators, hepatocyte nuclear factors 1α and 4 (HNF-1α and HNF-4). The α1AT gene maps to a region of human chromosome 14q32.1 that includes a related serine protease inhibitor (serpin) gene encoding corticosteroid-binding globulin (CBG), and the chromatin organization of this ≈130-kb region, as defined by DNase I-hypersensitive sites, has been described. Microcell transfer of human chromosome 14 from fibroblasts to rat hepatoma cells results in activation of α1AT and CBG transcription and chromatin reorganization of the entire locus. To assess the roles of HNF-1α and HNF-4 in gene activation and chromatin remodeling, we transferred human chromosome 14 from fibroblasts to rat hepatoma cell variants that are deficient in expression of HNF-1α and HNF-4. The variant cells failed to activate either α1AT or CBG transcription, and chromatin remodeling failed to occur. However, α1AT and CBG transcription could be rescued by transfecting the cells with expression plasmids encoding HNF-1α or HNF-4. In these transfectants, the chromatin structure of the entire α1AT/CBG locus was reorganized to an expressing cell-typical state. Thus, HNF-1α and HNF-4 control both chromatin structure and gene activity of two cell-specific genes within the serpin gene cluster at 14q32.1. PMID:10468604

  13. Inhibitory effects of omega-3 fatty acids on injury-induced epidermal growth factor receptor transactivation contribute to delayed wound healing.

    PubMed

    Turk, Harmony F; Monk, Jennifer M; Fan, Yang-Yi; Callaway, Evelyn S; Weeks, Brad; Chapkin, Robert S

    2013-05-01

    Epidermal growth factor receptor (EGFR)-mediated signaling is required for optimal intestinal wound healing. Since n-3 polyunsaturated fatty acids (PUFA), specifically docosahexaenoic acid (DHA), alter EGFR signaling and suppress downstream activation of key signaling pathways, we hypothesized that DHA would be detrimental to the process of intestinal wound healing. Using a mouse immortalized colonocyte model, DHA uniquely reduced EGFR ligand-induced receptor activation, whereas DHA and its metabolic precursor eicosapentaenoic acid (EPA) reduced wound-induced EGFR transactivation compared with control (no fatty acid or linoleic acid). Under wounding conditions, the suppression of EGFR activation was associated with a reduction in downstream activation of cytoskeletal remodeling proteins (PLCγ1, Rac1, and Cdc42). Subsequently, DHA and EPA reduced cell migration in response to wounding. Mice were fed a corn oil-, DHA-, or EPA-enriched diet prior to intestinal wounding (2.5% dextran sodium sulfate for 5 days followed by termination after 0, 3, or 6 days of recovery). Mortality was increased in EPA-fed mice and colonic histological injury scores were increased in EPA- and DHA-fed mice compared with corn oil-fed (control) mice. Although kinetics of colonic EGFR activation and downstream signaling (PLCγ1, Rac1, and Cdc42) were delayed by both n-3 PUFA, colonic repair was increased in EPA- relative to DHA-fed mice. These results indicate that, during the early response to intestinal wounding, DHA and EPA uniquely delay the activation of key wound-healing processes in the colon. This effect is mediated, at least in part, via suppression of EGFR-mediated signaling and downstream cytoskeletal remodeling.

  14. MHC class II transactivator represses human IL-4 gene transcription by interruption of promoter binding with CBP/p300, STAT6 and NFAT1 via histone hypoacetylation

    PubMed Central

    Zhou, Xiaorong; Jiang, Yang; Lu, Liming; Ding, Qing; Jiao, Zhijun; Zhou, Yun; Xin, Lijun; Chou, Kuang-Yen

    2007-01-01

    In addition to its property of enhancing major histocompatibility complex (MHC) class II expression, the class II transactivator (CIITA) was recently demonstrated to be involved in T helper type 1/type 2 (Th1/Th2) differentiation by regulating interleukin-4 (IL-4) gene transcription. There was however, controversy regarding whether CIITA promotes or suppresses IL-4 expression in the experiments with transgenic mice. To clarify the discrepancy by using simpler experimental systems, human Jurkat T cells that express IL-4 but not interferon-γ, even if stimulated with phorbol 12-myristate 13-acetate plus ionomycin, were used for CIITA transfection. Significant suppression of IL-4 gene expression was demonstrated. Simultaneously, histones H3 and H4 in the IL-4 promoter were hypoacetylated. The suppression could be totally reversed by the histone deacetylatase inhibitor trichostatin A. Furthermore, the IL-4 expression was determined in primarily established human Th1/Th2 cells to which CIITA small interference RNA (siRNA) had been introduced. A substantially increased level of IL-4 was recorded in the CIITA siRNA-transfected Th1 cells, which was in parallel with significantly enhanced acetylation in histone H3 of the IL-4 promoter. Chromatin immunoprecipitation analysis indicated that CIITA abrogated the binding of coactivator CBP/p300 and transcription factors STAT6/NFAT1 to IL-4 promoter in the CIITA-transfected cells. In conclusion, CIITA was active in the repression of transcription activation of human IL-4 gene in both the T-cell line and the primary human CD4 T cells by preventing transcription factors from binding to IL-4 promoter through histone hypoacetylation. Our data confirm a potential significant role of CIITA in controlling Th1/Th2 differentiation via modulation of IL-4 gene activation. PMID:17645498

  15. NF-Y binding is required for transactivation of neuronal aromatic L-amino acid decarboxylase gene promoter by the POU-domain protein Brn-2.

    PubMed

    Dugast, C; Weber, M J

    2001-04-18

    We have previously characterized binding sites for the NF-Y transcription factor (-71/-52) and Brn-2 POU-domain protein (-92/-71) in the neuronal promoter of the human aromatic L-amino acid decarboxylase gene [Mol. Brain Res. 56 (1998) 227]. We have now explored the functional role of these binding sites in transfected SK-N-BE neuroblastoma cells. Mutations of the NF-Y site that abolish binding depressed expression of a luciferase reporter gene up to 25-fold. The overexpression of a dominant negative mutant of NF-YA subunit depressed expression by 60%. Promoter activity was increased by the overexpression of Brn-2. Mutations or deletion of the binding site of Brn-2 did not suppress transcriptional activation by overexpressed Brn-2, while promoters defective in NF-Y binding were not transactivated by Brn-2. A GST-pulldown experiment showed that recombinant human Brn-2 protein weakly interacts with recombinant NF-Y outside of DNA. Cooperative binding of recombinant NF-Y and GST--Brn-2 proteins on the neuronal promoter was evidenced by an electrophoretic mobility shift assay. The POU-domain of Brn-2 was sufficient for such interaction. The results thus suggest that the activation of the neuronal promoter of the aromatic L-amino acid decarboxylase gene requires a direct interaction between the ubiquitous NF-Y factor and a cell-specific POU-domain protein. The NF-Y, but not the Brn-2 binding site, is essential for the recruitment of the NF-Y/Brn-2 complex on the promoter. PMID:11311976

  16. Differential activation of the 21-base-pair enhancer element of human T-cell leukemia virus type I by its own trans-activator and cyclic AMP.

    PubMed Central

    Nakamura, M; Niki, M; Ohtani, K; Sugamura, K

    1989-01-01

    A transcriptional trans-acting factor p40tax of human T-cell leukemia virus type I (HTLV-I) functions as an inducer for expression of HTLV-I provirus via activation of the enhancer in the long terminal repeat of HTLV-I. In addition to p40tax and a tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, we report here that forskolin, an activator of adenyl cyclase, also induces function of the HTLV-I enhancer. Experiments with mutants of the HTLV-I enhancer revealed that TPA-induced activation was not mediated by solely a 21-base-pair (bp) sequence that is repeated three times in the enhancer, whereas the 21-bp enhancer element can act as a sufficient cis-acting sequence for activation by both p40tax and forskolin. In addition, we found that nuclear factor(s) like the cyclic AMP-responsive element (CRE) binding factor could bind to the HTLV-I 21-bp enhancer element. However, a difference was found in sequences required for activation by p40tax and forskolin. A CRE related sequence present in the 21-bp enhancer element was enough for forskolin-induced activation. On the other hand, p40tax required a much longer sequence that is overlapping but not identical to the CRE related sequence, suggesting that the forskolin-induced cyclic AMP pathway may be partly involved in, but not sufficient for p40tax-mediating trans-activation of the HTLV-I enhancer. Images PMID:2548156

  17. Identification of paired immunoglobulin-like type 2 receptor α as hepatitis B virus DNA polymerase transactivated protein 1 interacting proteins.

    PubMed

    Lun, Yong-Zhi; Chi, Qing; Wang, Xue-Lei; Wang, Fang; Sui, Wen

    2014-02-01

    Hepatitis B Virus (HBV) DNA polymerase transactivated protein 1 (HBVDNAPTP1) is a novel protein transfected by HBV DNA polymerase, which has been screened by a suppression subtractive hybridization technique. In the present study, a yeast two-hybrid system was used to screen the proteins interacting with HBVDNAPTP1 in leukocytes in order to investigate the biological function of HBVDNAPTP1. The HBVDNAPTP1 coding sequence was cloned into a pGEM-T vector. Subsequent to sequencing, the HBVDNAPTP1 was subcloned into the bait plasmid pGBKT7 and transformed into yeast AH109. Western blotting confirmed the presence of HBVDNAPTP1 expression in the AH109 yeast strains. The transformed yeast AH109 cells were mated with Y187 yeast cells containing the leucocyte cDNA library pACT2 plasmids in 2X yeast extract peptone D-glucose adenine (YPDA) medium. For selection and screening, diploid yeast was plated on synthetic dropout medium (SD/-Trp-Leu-His-Ade) containing X-α-gal. Following sequencing and the verification of the open reading frames of positive colonies, four different proteins were obtained. To further confirm the interaction between HBVDNAPTP1 and the screened proteins, paired immunoglobulin-like type 2 receptor α (PILRA), one of the positive colonies, was cloned. The glutathione S-transferase pull-down in vitro assay and a co-immunoprecipitation in vivo assay were used to examine the interaction between HBVDNAPTP1 and PILRA, respectively. HBVDNAPTP1 may be involved in the negative regulation of the PILRA‑mediated Janus-activated kinase/signal tranducer and activator of transcription signaling pathway, and exert a positive effect on the initiation of monocyte apoptosis. These results contribute our knowledge of the biological functions of HBVDNAPTP1 and provide novel data to aid in the further analysis of the regulatory mechanism of this protein.

  18. The human papillomavirus type 16 E7 gene product interacts with and trans-activates the AP1 family of transcription factors.

    PubMed Central

    Antinore, M J; Birrer, M J; Patel, D; Nader, L; McCance, D J

    1996-01-01

    The E7 gene product of human papillomavirus type 16 (HPV16) binds to the retinoblastoma gene product (pRb) and dissociates pRb-E2F complexes. However, the observation that the ability of E7 to bind pRb is not required for the HPV16-induced immortalization of primary keratinocytes prompted a search for other cellular factors bound by E7. Using a glutathione-S-transferase (GST) fusion protein system, we show that E7 complexes with AP1 transcription factors including c-Jun, JunB, JunD and c-Fos. The ability of E7 to complex with c-Jun in vivo is demonstrated by co-immunoprecipitation and the yeast two-hybrid system. An analysis of E7 point mutants in the GST system indicates that the E7 zinc-finger motif, but not the pRb binding domain, is involved in these interactions. Using c-Jun deletion mutants, E7 binding maps between amino acids 224 and 286 of c-Jun. E7 trans-activates c-Jun-induced transcription from a Jun responsive promoter, and this activity correlates with the ability of E7 mutants to bind Jun proteins. Finally, a transcriptionally inactive c-Jun deletion, which can bind E7, interferes with the E7-induced transformation of rat embryo fibroblasts in cooperation with an activated ras, indicating that the Jun-E7 interaction is physiologically relevant and that Jun factors may be targeted in the E7 transformation pathway. Images PMID:8617242

  19. Structures of KIX domain of CBP in complex with two FOXO3a transactivation domains reveal promiscuity and plasticity in coactivator recruitment.

    PubMed

    Wang, Feng; Marshall, Christopher B; Yamamoto, Kazuo; Li, Guang-Yao; Gasmi-Seabrook, Geneviève M C; Okada, Hitoshi; Mak, Tak W; Ikura, Mitsuhiko

    2012-04-17

    Forkhead box class O 3a (FOXO3a) is a transcription factor and tumor suppressor linked to longevity that determines cell fate through activating transcription of cell differentiation, survival, and apoptotic genes. Recruitment of the coactivator CBP/p300 is a crucial step in transcription, and we revealed that in addition to conserved region 3 (CR3) of FOXO3a, the C-terminal segment of CR2 (CR2C) binds CBP/p300 and contributes to transcriptional activity. CR2C and CR3 of FOXO3a interact with the KIX domain of CBP/p300 at both "MLL" and "c-Myb" binding sites simultaneously. A FOXO3a CR2C-CR3 peptide in complex with KIX exists in equilibrium between two equally populated conformational states, one of which has CR2C bound to the MLL site and CR3 bound to the c-Myb site, whereas in the other, CR2C and CR3 bind the c-Myb and MLL sites, respectively. This promiscuous interaction between FOXO3a and CBP/p300 is further supported by additional binding sites on CBP/p300, namely, the TAZ1 and TAZ2 domains. In functional studies, our structure-guided mutagenesis showed that both CR2C and CR3 are involved in the activation of certain endogenous FOXO3a target genes. Further, phosphorylation of S626, a known AMP-dependent protein kinase target in CR3, increased affinity for CBP/p300 and the phosphomimetic mutation enhanced transactivation of luciferase. These findings underscore the significance of promiscuous multivalent interactions and posttranslational modification in the recruitment of transcriptional coactivators, which may allow transcription factors to adapt to various gene-specific genomic and chromatin structures and respond to cell signals. PMID:22474372

  20. α6 Integrin Transactivates Insulin-like Growth Factor Receptor-1 (IGF-1R) to Regulate Caspase-3-mediated Lens Epithelial Cell Differentiation Initiation*

    PubMed Central

    Basu, Subhasree; Rajakaruna, Suren; De Arcangelis, Adèle; Zhang, Liping; Georges-Labouesse, Elisabeth; Menko, A. Sue

    2014-01-01

    The canonical mitochondrial death pathway was first discovered for its role in signaling apoptosis. It has since been found to have a requisite function in differentiation initiation in many cell types including the lens through low level activation of the caspase-3 protease. The ability of this pathway to function as a molecular switch in lens differentiation depends on the concurrent induction of survival molecules in the Bcl-2 and IAP families, induced downstream of an IGF-1R/NFκB coordinate survival signal, to regulate caspase-3 activity. Here we investigated whether α6 integrin signals upstream to this IGF-1R-mediated survival-linked differentiation signal. Our findings show that IGF-1R is recruited to and activated specifically in α6 integrin receptor signaling complexes in the lens equatorial region, where lens epithelial cells initiate their differentiation program. In studies with both α6 integrin knock-out mice lenses and primary lens cell cultures following α6 integrin siRNA knockdown, we show that IGF-1R activation is dependent on α6 integrin and that this transactivation requires Src kinase activity. In addition, without α6 integrin, activation and expression of NFκB was diminished, and expression of Bcl-2 and IAP family members were down-regulated, resulting in high levels of caspase-3 activation. As a result, a number of hallmarks of lens differentiation failed to be induced; including nuclear translocation of Prox1 in the differentiation initiation zone and apoptosis was promoted. We conclude that α6 integrin is an essential upstream regulator of the IGF-1R survival pathway that regulates the activity level of caspase-3 for it to signal differentiation initiation of lens epithelial cells. PMID:24381169

  1. Activated human T cells accomplish MHC class II expression through T cell-specific occupation of class II transactivator promoter III.

    PubMed

    Holling, Tjadine M; van der Stoep, Nienke; Quinten, Edwin; van den Elsen, Peter J

    2002-01-15

    Activated human T cells express HLA-DR, HLA-DQ, and HLA-DP on their surface, but the regulation and functioning of MHC class II molecules in T lymphocytes are poorly understood. Because the MHC class II transactivator (CIITA) is essential for MHC class II expression, we have investigated transcriptional activation of CIITA in activated T cells. In this study, we show that in human activated CD4(+) T cells, CIITA promoter III (CIITA-PIII) drives the expression of CIITA. The in vivo genomic footprint analysis revealed activated T cell-specific occupation of CIITA-PIII. Subsequent EMSA analysis of several promoter regions showed differences in banding pattern among activated T cells, naive T cells, primary B cells, and Raji B cells. Activating response element (ARE)-1 is shown to interact with the acute myeloid leukemia 2 transcription factor in nuclear extracts derived from both T and B cells. Interestingly, the acute myeloid leukemia 3 transcription factor was bound in nuclear extracts of T cells only. The ARE-2 sequence is able to bind CREB/activating transcription factor family members in both T and B cells. In addition, a yet unidentified Ets family member was found to interact with site C in activated T cells, whereas in B cells site C was bound by PU.1 and Pip/IFN regulatory factor 4/IFN consensus sequence binding protein for activated T cells. In Jurkat T cells, both ARE-1 and ARE-2 are crucial for CIITA-PIII activity, similar to Raji B cells. The differential banding pattern in in vivo genomic footprinting and transcription factor binding at the ARE-1 and site C between T cells and B cells probably reflects differences in CIITA-PIII activation pathways employed by these cell types. PMID:11777970

  2. Transactivation of epidermal growth factor receptor in vascular and renal systems in rats with experimental hyperleptinemia: role in leptin-induced hypertension.

    PubMed

    Jamroz-Wiśniewska, Anna; Wójcicka, Grazyna; Łowicka, Ewelina; Ksiazek, Marta; Bełtowski, Jerzy

    2008-04-15

    We examined the role of epidermal growth factor (EGF) receptor in the pathogenesis of leptin-induced hypertension in the rat. Leptin, administered in increasing doses (0.1-0.5 mg/kg/day) for 10 days, increased phosphorylation levels of non-receptor tyrosine kinase, c-Src, EGF receptor and extracellular signal-regulated kinases (ERK) in aorta and kidney, which was accompanied by the increase in plasma concentration and urinary excretion of isoprostanes and H2O2. Blood pressure and renal Na+,K+-ATPase activity were higher, whereas urinary sodium excretion was lower in animals receiving leptin. The effects of leptin on renal Na+,K+-ATPase, natriuresis and blood pressure were abolished by NADPH oxidase inhibitor, apocynin, Src kinase inhibitor, PP2, EGF receptor inhibitor, AG1478, protein farnesyltransferase inhibitor, manumycin A, and ERK inhibitor, PD98059. In contrast, inhibitors of insulin-like growth factor-1 and platelet-derived growth factor receptors, AG1024 and AG1295, respectively, only slightly reduced ERK phosphorylation and had no effect on blood pressure in rats receiving leptin. These data indicate that: (1) experimental hyperleptinemia is associated with oxidative stress and c-Src-dependent transactivation of the EGF receptor, which stimulates ERK in vascular wall and the kidney, (2) overactivity of EGF receptor-ERK pathway contributes to leptin-induced hypertension by stimulating renal Na+,K+-ATPase and reducing sodium excretion, (3) inhibitors of c-Src, EGF receptor and ERK may be considered as a novel therapy for hypertension associated with hyperleptinemia, e.g. in patients with obesity and metabolic syndrome.

  3. Transcriptional regulation of the human cystathionine beta-synthase -1b basal promoter: synergistic transactivation by transcription factors NF-Y and Sp1/Sp3.

    PubMed Central

    Ge, Y; Konrad, M A; Matherly, L H; Taub, J W

    2001-01-01

    Cystathionine beta-synthase (CBS) catalyses the condensation of serine and homocysteine to form cystathionine, an intermediate step in the synthesis of cysteine. Human CBS encodes five distinct 5' non-coding exons, the most frequent termed CBS -1a and CBS -1b, each transcribed from its own unique GC-rich TATA-less promoter. The minimal transcriptional region (-3792 to -3667) of the CBS -1b promoter was defined by 5'- and 3'-deletions, and transient transfections of reporter gene constructs in HepG2 cells, characterized by CBS transcription exclusively from the -1b promoter. Included in this 125 bp region are 3 GC-boxes (termed GC-a, GC-b and GC-c), an inverted CAAT-box and an E-box. By gel-shift and supershift assays, binding of specificity protein (Sp)1 and Sp3 to the GC-box elements, upstream stimulatory factor 1 (USF-1) to the E-box, and both nuclear factor (NF)-Y and an NF-1-like factor to the CAAT box could be demonstrated. By transient trans fections and reporter gene assays in HepG2 and Drosophila SL2 cells, a functional interplay was indicated between NF-Y binding to the CAAT-box, or between USF-1 binding to the E-box, and Sp1/Sp3 binding to the GC-box elements. In SL2 cells, NF-Y and Sp1/Sp3 were synergistic. Furthermore, both Sp1 and the long Sp3 isoform transactivated the CBS -1b minimal promoter; however, the short Sp3 isoforms were potent repressors. These results may explain the cell- or tissue-specific regulation of CBS transcription, and clarify the bases for alterations in CBS gene expression in human disease and Down's syndrome. PMID:11415440

  4. Curcumin inhibits HIV-1 by promoting Tat protein degradation

    PubMed Central

    Ali, Amjad; Banerjea, Akhil C.

    2016-01-01

    HIV-1 Tat is an intrinsically unfolded protein playing a pivotal role in viral replication by associating with TAR region of viral LTR. Unfolded proteins are degraded by 20S proteasome in an ubiquitin independent manner. Curcumin is known to activate 20S proteasome and promotes the degradation of intrinsically unfolded p53 tumor suppressor protein. Since HIV-1 Tat protein is largerly unfolded, we hypothesized that Tat may also be targeted through this pathway. Curcumin treated Tat transfected HEK-293T cells showed a dose and time dependent degradation of Tat protein. Contrary to this HIV-1 Gag which is a properly folded protein, remained unaffected with curcumin. Semi-quantitative RT-PCR analysis showed that curcumin treatment did not affect Tat gene transcription. Curcumin increased the rate of Tat protein degradation as shown by cycloheximide (CHX) chase assay. Degradation of the Tat protein is accomplished through proteasomal pathway as proteasomal inhibitor MG132 blocked Tat degradation. Curcumin also decreased Tat mediated LTR promoter transactivation and inhibited virus production from HIV-1 infected cells. Taken together our study reveals a novel observation that curcumin causes potent degradation of Tat which may be one of the major mechanisms behind its anti HIV activity. PMID:27283735

  5. Curcumin inhibits HIV-1 by promoting Tat protein degradation.

    PubMed

    Ali, Amjad; Banerjea, Akhil C

    2016-01-01

    HIV-1 Tat is an intrinsically unfolded protein playing a pivotal role in viral replication by associating with TAR region of viral LTR. Unfolded proteins are degraded by 20S proteasome in an ubiquitin independent manner. Curcumin is known to activate 20S proteasome and promotes the degradation of intrinsically unfolded p53 tumor suppressor protein. Since HIV-1 Tat protein is largerly unfolded, we hypothesized that Tat may also be targeted through this pathway. Curcumin treated Tat transfected HEK-293T cells showed a dose and time dependent degradation of Tat protein. Contrary to this HIV-1 Gag which is a properly folded protein, remained unaffected with curcumin. Semi-quantitative RT-PCR analysis showed that curcumin treatment did not affect Tat gene transcription. Curcumin increased the rate of Tat protein degradation as shown by cycloheximide (CHX) chase assay. Degradation of the Tat protein is accomplished through proteasomal pathway as proteasomal inhibitor MG132 blocked Tat degradation. Curcumin also decreased Tat mediated LTR promoter transactivation and inhibited virus production from HIV-1 infected cells. Taken together our study reveals a novel observation that curcumin causes potent degradation of Tat which may be one of the major mechanisms behind its anti HIV activity. PMID:27283735

  6. TLN-4601, a novel anticancer agent, inhibits Ras signaling post Ras prenylation and before MEK activation.

    PubMed

    Boufaied, Nadia; Wioland, My-Anh; Falardeau, Pierre; Gourdeau, Henriette

    2010-06-01

    TLN-4601 is a structurally novel farnesylated dibenzodiazepinone discovered through DECIPHER, Thallion's proprietary drug discovery platform. The compound was shown to have a broad cytotoxic activity (low micromol/l) when tested in the NCI 60 tumor cell line panel and has shown in-vivo antitumor activity in several xenograft models. Related to its farnesylated moiety, the effect of TLN-4601 on Ras mitogen-activated protein kinase signaling was assessed. Downstream Ras signaling events, Raf-1, MEK, and ERK1/2 phosphorylation in MCF7 cells were evaluated by western blot analysis. TLN-4601 prevented epidermal growth factor-induced phosphorylation of Raf-1, MEK, and ERK1/2. This effect was time-dependent and dose-dependent with complete inhibition of protein phosphorylation within 4-6 h at 10 micromol/l. The inhibition of Ras signaling was not mediated by the inhibition of protein prenylation, documented by the lack of effect TLN-4601 on the prenylation of HDJ2 (specific substrate of farnesyltransferase), RAP1A (specific substrate of geranylgeranyl transferase-1), or Ras. As TLN-4601 did not inhibit EGFR, Raf-1, MEK or ERK1/2 kinase activities, the inhibitory effect of TLN-4601 on Ras signaling is not mediated by direct kinase inhibition. Using an Elk-1 trans-activation reporter assay, we found that TLN-4601 inhibits the MEK/ERK pathway at the level of Raf-1. Interestingly, TLN-4601 induces Raf-1 proteasomal-dependent degradation. These data indicate that TLN-4601 may inhibit the Ras-mitogen-activated protein kinase-signaling pathway by depleting the Raf-1 protein.

  7. Retinoic acid receptor alpha mediates growth inhibition by retinoids in rat pancreatic carcinoma DSL-6A/C1 cells.

    PubMed

    Brembeck, F H; Kaiser, A; Detjen, K; Hotz, H; Foitzik, T; Buhr, H J; Riecken, E O; Rosewicz, S

    1998-11-01

    During carcinogenesis, pancreatic acinar cells can dedifferentiate into ductal adenocarcinoma of the pancreas. DSL-6A/C1 cells represent an in vitro model of this carcinogenic sequence. This study was designed to examine the effects of retinoids on cell growth in DSL-6A/C1 cells and to characterize further the molecular mechanisms underlying the antiproliferative actions of retinoids. Treatment of DSL-6A/C1 cells with retinoids results in a time- and dose-dependent inhibition of cell growth, paralleled by a retinoid-mediated transactivation of a pTK::betaRAREx2-luciferase reporter construct transiently transfected into DSL-6A/C1 cells. Retinoid receptor expression was evaluated by reverse transcriptase polymerase chain reaction (RT-PCR) using subtype-specific primers and demonstrated expression of retinoic acid receptor alpha (RAR-alpha), RAR-beta and retinoid X receptor alpha (RXR-alpha). Using a panel of receptor subtype-specific agonists, the RAR-alpha specific agonist Ro 40-6055 was the most potent retinoid in terms of growth inhibition. Furthermore, all-trans-retinoic acid-mediated growth inhibition and transactivation was completely blocked by the RAR-alpha-specific antagonist Ro 41-5253. In summary, the RAR-alpha subtype predominantly mediates the antiproliferative effects of retinoids in DSL-6A/C1 cells. Furthermore, this cell system provides a feasible tool to study the molecular mechanisms underlying the growth inhibitory effects of retinoids in ductal pancreatic carcinoma cells derived from a primary acinar cell phenotype.

  8. CP-31398 inhibits the growth of p53-mutated liver cancer cells in vitro and in vivo.

    PubMed

    He, Xing-Xing; Zhang, Yu-Nan; Yan, Jun-Wei; Yan, Jing-Jun; Wu, Qian; Song, Yu-Hu

    2016-01-01

    The tumor suppressor p53 is one of the most frequently mutated genes in hepatocellular carcinoma (HCC). Previous studies demonstrated that CP-31398 restored the native conformation of mutant p53 and trans-activated p53 downstream genes in tumor cells. However, the research on the application of CP-31398 to liver cancer has not been reported. Here, we investigated the effects of CP-31398 on the phenotype of HCC cells carrying p53 mutation. The effects of CP-31398 on the characteristic of p53-mutated HCC cells were evaluated through analyzing cell cycle, cell apoptosis, cell proliferation, and the expression of p53 downstream genes. In tumor xenografts developed by PLC/PRF/5 cells, the inhibition of tumor growth by CP-31398 was analyzed through gross morphology, growth curve, and the expression of p53-related genes. Firstly, we demonstrated that CP-31398 inhibited the growth of p53-mutated liver cancer cells in a dose-dependent and p53-dependent manner. Then, further study showed that CP-31398 re-activated wild-type p53 function in p53-mutated HCC cells, which resulted in inhibitive response of cell proliferation and an induction of cell-cycle arrest and apoptosis. Finally, in vivo data confirmed that CP-31398 blocked the growth of xenografts tumors through transactivation of p53-responsive downstream molecules. Our results demonstrated that CP-31398 induced desired phenotypic change of p53-mutated HCC cells in vitro and in vivo, which revealed that CP-31398 would be developed as a therapeutic candidate for HCC carrying p53 mutation.

  9. The Rel/NF-κB pathway and transcription of immediate early genes in T cell activation are inhibited by microgravity

    PubMed Central

    Chang, Tammy T.; Walther, Isabelle; Li, Chai-Fei; Boonyaratanakornkit, Jim; Galleri, Grazia; Meloni, Maria Antonia; Pippia, Proto; Cogoli, Augusto; Hughes-Fulford, Millie

    2012-01-01

    This study tested the hypothesis that transcription of immediate early genes is inhibited in T cells activated in μg. Immunosuppression during spaceflight is a major barrier to safe, long-term human space habitation and travel. The goals of these experiments were to prove that μg was the cause of impaired T cell activation during spaceflight, as well as understand the mechanisms controlling early T cell activation. T cells from four human donors were stimulated with Con A and anti-CD28 on board the ISS. An on-board centrifuge was used to generate a 1g simultaneous control to isolate the effects of μg from other variables of spaceflight. Microarray expression analysis after 1.5 h of activation demonstrated that μg- and 1g-activated T cells had distinct patterns of global gene expression and identified 47 genes that were significantly, differentially down-regulated in μg. Importantly, several key immediate early genes were inhibited in μg. In particular, transactivation of Rel/NF-κB, CREB, and SRF gene targets were down-regulated. Expression of cREL gene targets were significantly inhibited, and transcription of cREL itself was reduced significantly in μg and upon anti-CD3/anti-CD28 stimulation in simulated μg. Analysis of gene connectivity indicated that the TNF pathway is a major early downstream effector pathway inhibited in μg and may lead to ineffective proinflammatory host defenses against infectious pathogens during spaceflight. Results from these experiments indicate that μg was the causative factor for impaired T cell activation during spaceflight by inhibiting transactivation of key immediate early genes. PMID:22750545

  10. African Swine Fever Virus Blocks the Host Cell Antiviral Inflammatory Response through a Direct Inhibition of PKC-θ-Mediated p300 Transactivation▿

    PubMed Central

    Granja, Aitor G.; Sánchez, Elena G.; Sabina, Prado; Fresno, Manuel; Revilla, Yolanda

    2009-01-01

    During a viral infection, reprogramming of the host cell gene expression pattern is required to establish an adequate antiviral response. The transcriptional coactivators p300 and CREB binding protein (CBP) play a central role in this regulation by promoting the assembly of transcription enhancer complexes to specific promoters of immune and proinflammatory genes. Here we show that the protein A238L encoded by African swine fever virus counteracts the host cell inflammatory response through the control of p300 transactivation during the viral infection. We demonstrate that A238L inhibits the expression of the inflammatory regulators cyclooxygenase-2 (COX-2) and tumor necrosis factor alpha (TNF-α) by preventing the recruitment of p300 to the enhanceosomes formed on their promoters. Furthermore, we report that A238L inhibits p300 activity during the viral infection and that its amino-terminal transactivation domain is essential in the A238L-mediated inhibition of the inflammatory response. Importantly, we found that the residue serine 384 of p300 is required for the viral protein to accomplish its inhibitory function and that ectopically expressed PKC-θ completely reverts this inhibition, thus indicating that this signaling pathway is disrupted by A238L during the viral infection. Furthermore, we show here that A238L does not affect PKC-θ enzymatic activity, but the molecular mechanism of this viral inhibition relies on the lack of interaction between PKC-θ and p300. These findings shed new light on how viruses alter the host cell antiviral gene expression pattern through the blockade of the p300 activity, which represents a new and sophisticated viral mechanism to evade the inflammatory and immune defense responses. PMID:19004945

  11. The Rel/NF-κB pathway and transcription of immediate early genes in T cell activation are inhibited by microgravity.

    PubMed

    Chang, Tammy T; Walther, Isabelle; Li, Chai-Fei; Boonyaratanakornkit, Jim; Galleri, Grazia; Meloni, Maria Antonia; Pippia, Proto; Cogoli, Augusto; Hughes-Fulford, Millie

    2012-12-01

    This study tested the hypothesis that transcription of immediate early genes is inhibited in T cells activated in μg. Immunosuppression during spaceflight is a major barrier to safe, long-term human space habitation and travel. The goals of these experiments were to prove that μg was the cause of impaired T cell activation during spaceflight, as well as understand the mechanisms controlling early T cell activation. T cells from four human donors were stimulated with Con A and anti-CD28 on board the ISS. An on-board centrifuge was used to generate a 1g simultaneous control to isolate the effects of μg from other variables of spaceflight. Microarray expression analysis after 1.5 h of activation demonstrated that μg- and 1g-activated T cells had distinct patterns of global gene expression and identified 47 genes that were significantly, differentially down-regulated in μg. Importantly, several key immediate early genes were inhibited in μg. In particular, transactivation of Rel/NF-κB, CREB, and SRF gene targets were down-regulated. Expression of cREL gene targets were significantly inhibited, and transcription of cREL itself was reduced significantly in μg and upon anti-CD3/anti-CD28 stimulation in simulated μg. Analysis of gene connectivity indicated that the TNF pathway is a major early downstream effector pathway inhibited in μg and may lead to ineffective proinflammatory host defenses against infectious pathogens during spaceflight. Results from these experiments indicate that μg was the causative factor for impaired T cell activation during spaceflight by inhibiting transactivation of key immediate early genes.

  12. Protein and DNA elements involved in transactivation of the promoter of the bovine herpesvirus (BHV) 1 IE-1 transcription unit by the BHV alpha gene trans-inducing factor.

    PubMed Central

    Misra, V; Bratanich, A C; Carpenter, D; O'Hare, P

    1994-01-01

    In herpes simplex virus (HSV)-infected cells, the transcription of immediate-early (alpha) genes is regulated by a virion component, the alpha gene trans-inducing factor (alpha TIF). This protein forms a complex with cellular factors and TAATGARAT motifs present in one or more copies in the promoters of all alpha genes. We have characterized the bovine herpesvirus 1 (BHV-1) homolog of this protein. Like its HSV counterpart, the BHV alpha TIF was synthesized in the later stages of infection and could be demonstrated to be a component of purified virions. In transient expression assays, BHV alpha TIF was a strong transactivator and stimulated the activity of IE-1, the major BHV-1 alpha gene promoter, with an efficiency comparable to that of HSV alpha TIF. This stimulation was largely dependent on a TAATGAGCT sequence present in a single copy in IE-1, and BHV alpha TIF, in conjunction with cellular factors, formed a complex with oligonucleotides containing this sequence. Despite these similarities between the two alpha TIFs, our preliminary observations suggest that the proteins may activate transcription by different mechanisms. Although BHV alpha TIF strongly transactivated IE-1, it differed from its HSV counterpart in that the carboxyl terminus of BHV alpha TIF, when fused to the DNA-binding domain of GAL4, was a relatively poor stimulator of a promoter containing GAL4-binding sites. Also unlike HSV alpha TIF, removal of the carboxyl terminus of BHV alpha TIF reduced but did not eliminate the ability of the protein to transactivate IE-1. These results are discussed in view of the structural similarities and differences among the alpha TIFs of alphaherpes-viruses. Images PMID:8035488

  13. Residues R{sup 199}H{sup 200} of prototype foamy virus transactivator Bel1 contribute to its binding with LTR and IP promoters but not its nuclear localization

    SciTech Connect

    Ma, Qinglin; Tan, Juan; Cui, Xiaoxu; Luo, Di; Yu, Miao; Liang, Chen; Qiao, Wentao

    2014-01-20

    Prototype foamy virus encodes a transactivator called Bel1 that enhances viral gene transcription and is essential for PFV replication. Nuclear localization of Bel1 has been reported to rely on two proximal basic motifs R{sup 199}H{sup 200} and R{sup 221}R{sup 222}R{sup 223} that likely function together as a bipartite nuclear localization signal. In this study, we report that mutating R{sup 221}R{sup 222}R{sup 223}, but not R{sup 199}H{sup 200}, relocates Bel1 from the nucleus to the cytoplasm, suggesting an essential role for R{sup 221}R{sup 222}R{sup 223} in the nuclear localization of Bel1. Although not affecting the nuclear localization of Bel1, mutating R{sup 199}H{sup 200} disables Bel1 from transactivating PFV promoters. Results of EMSA reveal that the R{sup 199}H{sup 200} residues are vital for the binding of Bel1 to viral promoter DNA. Moreover, mutating R{sup 199}H{sup 200} in Bel1 impairs PFV replication to a much greater extent than mutating R{sup 221}R{sup 222}R{sup 223}. Collectively, our findings suggest that R{sup 199}H{sup 200} directly participate in Bel1 binding to viral promoter DNA and are indispensible for Bel1 transactivation activity. - Highlights: • The R{sup 221}R{sup 222}R{sup 223} residues are essential for the nuclear localization of Bel1. • Although not affecting the nuclear localization of Bel1, mutating R{sup 199}H{sup 200} disables Bel1 from transactivating PFV promoters. • The R{sup 199}H{sup 200} residues directly participate in Bel1 binding to viral promoter DNA. • Mutating R{sup 199}H{sup 200} in Bel1 impairs PFV replication to a much greater extent than mutating R{sup 221}R{sup 222}R{sup 223}.

  14. Reversible cell cycle inhibition and premature aging features imposed by conditional expression of p16Ink4a

    PubMed Central

    Boquoi, Amelie; Arora, Sanjeevani; Chen, Tina; Litwin, Sam; Koh, James; Enders, Greg H

    2015-01-01

    The cyclin-dependent kinase (Cdk) inhibitor p16Ink4a (p16) is a canonical mediator of cellular senescence and accumulates in aging tissues, where it constrains proliferation of some progenitor cells. However, whether p16 induction in tissues is sufficient to inhibit cell proliferation, mediate senescence, and/or impose aging features has remained unclear. To address these issues, we generated transgenic mice that permit conditional p16 expression. Broad induction at weaning inhibited proliferation of intestinal transit-amplifying and Lgr5+ stem cells and rapidly imposed features of aging, including hair loss, skin wrinkling, reduced body weight and subcutaneous fat, an increased myeloid fraction in peripheral blood, poor dentition, and cataracts. Aging features were observed with multiple combinations of p16 transgenes and transactivators and were largely abrogated by a germline Cdk4 R24C mutation, confirming that they reflect Cdk inhibition. Senescence markers were not found, and de-induction of p16, even after weeks of sustained expression, allowed rapid recovery of intestinal cell proliferation and reversal of aging features in most mice. These results suggest that p16-mediated inhibition of Cdk activity is sufficient to inhibit cell proliferation and impose aging features in somatic tissues of mammals and that at least some of these aging features are reversible. PMID:25481981

  15. Reversible cell cycle inhibition and premature aging features imposed by conditional expression of p16Ink4a.

    PubMed

    Boquoi, Amelie; Arora, Sanjeevani; Chen, Tina; Litwin, Sam; Koh, James; Enders, Greg H

    2015-02-01

    The cyclin-dependent kinase (Cdk) inhibitor p16(Ink4a) (p16) is a canonical mediator of cellular senescence and accumulates in aging tissues, where it constrains proliferation of some progenitor cells. However, whether p16 induction in tissues is sufficient to inhibit cell proliferation, mediate senescence, and/or impose aging features has remained unclear. To address these issues, we generated transgenic mice that permit conditional p16 expression. Broad induction at weaning inhibited proliferation of intestinal transit-amplifying and Lgr5+ stem cells and rapidly imposed features of aging, including hair loss, skin wrinkling, reduced body weight and subcutaneous fat, an increased myeloid fraction in peripheral blood, poor dentition, and cataracts. Aging features were observed with multiple combinations of p16 transgenes and transactivators and were largely abrogated by a germline Cdk4 R24C mutation, confirming that they reflect Cdk inhibition. Senescence markers were not found, and de-induction of p16, even after weeks of sustained expression, allowed rapid recovery of intestinal cell proliferation and reversal of aging features in most mice. These results suggest that p16-mediated inhibition of Cdk activity is sufficient to inhibit cell proliferation and impose aging features in somatic tissues of mammals and that at least some of these aging features are reversible. PMID:25481981

  16. Two phenylalanines in the C-terminus of Epstein-Barr virus Rta protein reciprocally modulate its DNA binding and transactivation function

    SciTech Connect

    Chen, L.-W.; Raghavan, Vineetha; Chang, Pey-Jium; Shedd, Duane; Heston, Lee; Delecluse, Henri-Jacques; Miller, George

    2009-04-10

    The Rta (R transactivator) protein plays an essential role in the Epstein-Barr viral (EBV) lytic cascade. Rta activates viral gene expression by several mechanisms including direct and indirect binding to target viral promoters, synergy with EBV ZEBRA protein, and stimulation of cellular signaling pathways. We previously found that Rta proteins with C-terminal truncations of 30 aa were markedly enhanced in their capacity to bind DNA (Chen, L.W., Chang, P.J., Delecluse, H.J., and Miller, G., (2005). Marked variation in response of consensus binding elements for the Rta protein of Epstein-Barr virus. J. Virol. 79(15), 9635-9650.). Here we show that two phenylalanines (F600 and F605) in the C-terminus of Rta play a crucial role in mediating this DNA binding inhibitory function. Amino acids 555 to 605 of Rta constitute a functional DNA binding inhibitory sequence (DBIS) that markedly decreased DNA binding when transferred to a minimal DNA binding domain of Rta (aa 1-350). Alanine substitution mutants, F600A/F605A, abolished activity of the DBIS. F600 and F605 are located in the transcriptional activation domain of Rta. Alanine substitutions, F600A/F605A, decreased transcriptional activation by Rta protein, whereas aromatic substitutions, such as F600Y/F605Y or F600W/F605W, partially restored transcriptional activation. Full-length Rta protein with F600A/F605A mutations were enhanced in DNA binding compared to wild-type, whereas Rta proteins with F600Y/F605Y or F600W/F605W substitutions were, like wild-type Rta, relatively poor DNA binders. GAL4 (1-147)/Rta (416-605) fusion proteins with F600A/F605A mutations were diminished in transcriptional activation, relative to GAL4/Rta chimeras without such mutations. The results suggest that, in the context of a larger DBIS, F600 and F605 play a role in the reciprocal regulation of DNA binding and transcriptional activation by Rta. Regulation of DNA binding by Rta is likely to be important in controlling its different modes of

  17. Secreted phospholipase A2-IIA-induced a phenotype of activated microglia in BV-2 cells requires epidermal growth factor receptor transactivation and proHB-EGF shedding

    PubMed Central

    2012-01-01

    inhibitor (TAPI-1), and a HB-EGF neutralizing antibody abrogated the phenotype of activated microglia induced by the sPLA2-IIA. Conclusion These results support the hypothesis that sPLA2-IIA may act as a potent modulator of microglial functions through its ability to induce EGFR transactivation and HB-EGF release. Accordingly, pharmacological modulation of EGFR might be a useful tool for treating neuroinflammatory diseases characterized by sPLA2-IIA accumulation. PMID:22747893

  18. The p53 activation domain binds the TATA box-binding polypeptide in Holo-TFIID, and a neighboring p53 domain inhibits transcription.

    PubMed Central

    Liu, X; Miller, C W; Koeffler, P H; Berk, A J

    1993-01-01

    Antioncogene product p53 is a transcriptional transactivator. To investigate how p53 stimulates transcription, we examined the interaction of p53 with general transcription factors in vitro. We found that p53 binds directly to the human TATA box-binding polypeptide (TBP). We also observed a direct interaction between p53 and purified holo-TFIID, a complex composed of TBP and a group of TBP-associated polypeptides known as TAFs. The p53 binding domain on TBP was mapped to the conserved region of TBP, including residues 220 to 271. The TBP binding domain on p53 was mapped to the p53 activation domain between residues 20 and 57. To analyze the significance of the p53-TBP interaction in p53 transactivation, we compared the ability of Gal4-p53 fusion proteins to bind to TBP in vitro and to activate transcription in transient transfection assays. Fusion proteins which bound to TBP activated transcription, and those that did not bind to TBP did not activate transcription to a detectable level, suggesting that a direct interaction between TBP and p53 is required for p53 transactivation. We also found that inclusion of residues 93 to 160 of p53 in a Gal4-p53 fusion repressed transcriptional activation 100-fold. Consequently, this region of p53 inhibits transcriptional activation by the minimal p53 activation domain. Highest levels of activation were observed with sequences 1 to 92 of p53 fused to Gal4, even though this construct bound to TBP in vitro with an affinity similar to that of other Gal4-p53 fusion proteins. We conclude that TBP binding is necessary for p53 transcriptional activation and that p53 sequences outside the TBP binding domain modulate the level of activation. Images PMID:8497252

  19. Prolactin inhibits a major tumor-suppressive function of wild type BRCA1.

    PubMed

    Chen, Kuan-Hui Ethan; Walker, Ameae M

    2016-06-01

    Even though mutations in the tumor suppressor, BRCA1, markedly increase the risk of breast and ovarian cancer, most breast and ovarian cancers express wild type BRCA1. An important question is therefore how the tumor-suppressive function of normal BRCA1 is overcome during development of most cancers. Because prolactin promotes these and other cancers, we investigated the hypothesis that prolactin interferes with the ability of BRCA1 to inhibit the cell cycle. Examining six different cancer cell lines with wild type BRCA1, and making use of both prolactin and the growth-inhibiting selective prolactin receptor modulator, S179D PRL, we demonstrate that prolactin activation of Stat5 results in the formation of a complex between phospho-Stat5 and BRCA1. Formation of this complex does not interfere with nuclear translocation or binding of BRCA1 to the p21 promoter, but does interfere with the ability of BRCA1 to transactivate the p21 promoter. Overexpression of a dominant-negative Stat5 in prolactin-stimulated cells resulted in increased p21 expression. We conclude that prolactin inhibits a major tumor-suppressive function of BRCA1 by interfering with BRCA1's upregulation of expression of the cell cycle inhibitor, p21.

  20. COUP-TFII inhibits NFkappaB activation in endocrine-resistant breast cancer cells

    PubMed Central

    Litchfield, Lacey M.; Appana, Savitri N.; Datta, Susmita; Klinge, Carolyn M.

    2016-01-01

    Reduced COUP-TFII expression contributes to endocrine resistance in breast cancer cells. Endocrine-resistant breast cancer cells have higher NFkappa B (NFκB) activity and target gene expression. The goal of this study was to determine if COUP-TFII modulates NFκB activity. Endocrine-resistant LCC9 cells with low endogenous COUP-TFII displayed ~5-fold higher basal NFκB activity than parental endocrine-sensitive MCF-7 breast cancer cells. Transient transfection of LCC9 cells with COUP-TFII inhibited NFκB activation and reduced NFκB target gene expression. COUP-TFII and NFκB were inversely correlated in breast cancer patient samples. Endogenous COUP-TFII coimmunoprecipitated with NFκB subunits RelB and NFκB1 in MCF-7 cells. COUP-TFII inhibited NFκB-DNA binding in vitro and impaired coactivator induced NFκB transactivation. LCC9 cells were growth-inhibited by an NFκB inhibitor and 4-hydroxytamoxifen compared to MCF-7 cells. Together these data indicate a novel role for COUP-TFII in suppression of NFκB activity and explain, in part, why decreased COUP-TFII expression results in an endocrine-resistant phenotype. PMID:24141032

  1. Inhibition of ERK Oscillations by Ionizing Radiation and Reactive Oxygen Species

    SciTech Connect

    Shankaran, Harish; Chrisler, William B; Sontag, Ryan L; Weber, Thomas J

    2010-12-28

    The shuttling of activated protein kinases between the cytoplasm and nucleus is an essential feature of normal growth factor signaling cascades. Here we demonstrate that transforming growth factor alpha (TGFα) induces oscillations in extracellular signal regulated kinase (ERK) cytoplasmic-nuclear translocations in human keratinocytes. TGFα-dependent ERK oscillations mediated through the epidermal growth factor receptor (EGFR) are inhibited by low dose X-irradiation (10 cGy) and low concentrations of hydrogen peroxide (0.32–3.26 µM H2O2) used as a model reactive oxygen species (ROS). A fluorescent indicator dye (H2-DCFDA) was used to measure cellular ROS levels following X-irradiation, 12-O-tetradecanoyl phorbol-13-acetate (TPA) and H2O2. X-irradiation did not generate significant ROS production while 0.32 µM H2O2 and TPA induced significant increases in ROS levels with H2O2 > TPA. TPA alone induced transactivation of the EGFR but did not induce ERK oscillations. TPA as a cotreatment did not inhibit TGFα-stimulated ERK oscillations but qualitatively altered TGFα-dependent ERK oscillation characteristics (amplitude, time-period). Collectively, these observations demonstrate that TGFα-induced ERK oscillations are inhibited by ionizing radiation/ROS and perturbed by epigenetic carcinogen in human keratinocytes. © 2010 Wiley-Liss, Inc.

  2. MYBPH inhibits NM IIA assembly via direct interaction with NMHC IIA and reduces cell motility

    SciTech Connect

    Hosono, Yasuyuki; Usukura, Jiro; Yamaguchi, Tomoya; Yanagisawa, Kiyoshi; Suzuki, Motoshi; Takahashi, Takashi

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer MYBPH inhibits NMHC IIA assembly and cell motility. Black-Right-Pointing-Pointer MYBPH interacts to assembly-competent NM IIA. Black-Right-Pointing-Pointer MYBPH inhibits RLC and NMHC IIA, independent components of NM IIA. -- Abstract: Actomyosin filament assembly is a critical step in tumor cell migration. We previously found that myosin binding protein H (MYBPH) is directly transactivated by the TTF-1 lineage-survival oncogene in lung adenocarcinomas and inhibits phosphorylation of the myosin regulatory light chain (RLC) of non-muscle myosin IIA (NM IIA) via direct interaction with Rho kinase 1 (ROCK1). Here, we report that MYBPH also directly interacts with an additional molecule, non-muscle myosin heavy chain IIA (NMHC IIA), which was found to occur between MYBPH and the rod portion of NMHC IIA. MYBPH inhibited NMHC IIA assembly and reduced cell motility. Conversely, siMYBPH-induced increased motility was partially, yet significantly, suppressed by blebbistatin, a non-muscle myosin II inhibitor, while more profound effects were attained by combined treatment with siROCK1 and blebbistatin. Electron microscopy observations showed well-ordered paracrystals of NMHC IIA reflecting an assembled state, which were significantly less frequently observed in the presence of MYBPH. Furthermore, an in vitro sedimentation assay showed that a greater amount of NMHC IIA was in an unassembled state in the presence of MYBPH. Interestingly, treatment with a ROCK inhibitor that impairs transition of NM IIA from an assembly-incompetent to assembly-competent state reduced the interaction between MYBPH and NMHC IIA, suggesting that MYBPH has higher affinity to assembly-competent NM IIA. These results suggest that MYBPH inhibits RLC and NMHC IIA, independent components of NM IIA, and negatively regulates actomyosin organization at 2 distinct steps, resulting in firm inhibition of NM IIA assembly.

  3. Ajoene, a stable garlic by-product, inhibits high fat diet-induced hepatic steatosis and oxidative injury through LKB1-dependent AMPK activation.

    PubMed

    Han, Chang Yeob; Ki, Sung Hwan; Kim, Young Woo; Noh, Kyoung; Lee, Da Yeon; Kang, Bomi; Ryu, Jae-Ha; Jeon, Raok; Kim, Eun Hyun; Hwang, Se Jin; Kim, Sang Geon

    2011-01-15

    Hepatic steatosis, a hepatic component of metabolic syndrome, is common and may progress to steatohepatitis and cirrhosis. The liver X receptor-α (LXRα)-sterol regulatory element binding protein-1c (SREBP-1c) pathway plays a key role in hepatic steatosis. This study investigated the potential of ajoene, a stable garlic by-product, to inhibit high fat diet (HFD)-induced hepatic steatosis and the underlying mechanism. Ajoene treatment attenuated fat accumulation and induction of lipogenic genes in the liver of HFD-fed mice. Blood biochemical analyses and histopathologic examinations showed that ajoene prevented liver injury with the inhibition of oxidative stress, as evidenced by thiobarbituric acid reactive substances formation and nitrotyrosinylation. Moreover, ajoene treatment inhibited LXRα agonist (T0901317)-mediated SREBP-1c activation, and transactivation of the lipogenic target genes in hepatocytes. Ajoene was found to activate AMP-activated protein kinase (AMPK) via LKB1, responsible for the inhibition of p70 ribosomal S6 kinase-1 (S6K1). The ability of ajoene to repress T0901317-induced SREBP-1c expression was antagonized by inhibition of AMPK or activation of S6K1, supporting the role of these kinases in the antisteatotic effect. Our results demonstrate that ajoene has an effect of activating AMPK through LKB1 and inhibit S6K1 activity, contributing to the prevention of SREBP-1c-mediated hepatic lipogenesis via the inhibition of LXRα activity.

  4. Saccadic Inhibition in Reading

    ERIC Educational Resources Information Center

    Reingold, Eyal M.; Stampe, Dave M.

    2004-01-01

    In 5 experiments, participants read text that was briefly replaced by a transient image for 33 ms at random intervals. A decrease in saccadic frequency, referred to as saccadic inhibition, occurred as early as 60-70 ms following the onset of abrupt changes in visual input. It was demonstrated that the saccadic inhibition was influenced by the…

  5. Inhibition of selectin binding

    DOEpatents

    Nagy, Jon O.; Spevak, Wayne R.; Dasgupta, Falguni; Bertozzi, Caroline

    1999-01-01

    This invention provides compositions for inhibiting the binding between two cells, one expressing P- or L-selectin on the surface and the other expressing the corresponding ligand. A covalently crosslinked lipid composition is prepared having saccharides and acidic group on separate lipids. The composition is then interposed between the cells so as to inhibit binding. Inhibition can be achieved at an effective oligosaccharide concentration as low as 10.sup.6 fold below that of the free saccharide. Since selectins are involved in recruiting cells to sites of injury, these composition scan be used to palliate certain inflammatory and immunological conditions.

  6. Inhibition of selectin binding

    DOEpatents

    Nagy, Jon O.; Spevak, Wayne R.; Dasgupta, Falguni; Bertozzi, Caroline

    2001-10-09

    This invention provides compositions for inhibiting the binding between two cells, one expressing P- or L-selectin on the surface and the other expressing the corresponding ligand. A covalently crosslinked lipid composition is prepared having saccharides and acidic group on separate lipids. The composition is then interposed between the cells so as to inhibit binding. Inhibition can be achieved at an effective oligosaccharide concentration as low as 10.sup.6 fold below that of the free saccharide. Since selectins are involved in recruiting cells to sites of injury, these composition scan be used to palliate certain inflammatory and immunological conditions.

  7. Inhibition of selectin binding

    DOEpatents

    Nagy, Jon O.; Spevak, Wayne R.; Dasgupta, Falguni; Bertozzi, Carolyn

    1999-10-05

    This invention provides a system for inhibiting the binding between two cells, one expressing P- or L-selectin on the surface and the other expressing the corresponding ligand. A covalently crosslinked lipid composition is prepared having saccharides and acidic group on separate lipids. The composition is then interposed between the cells so as to inhibit binding. Inhibition can be achieved at an effective oligosaccharide concentration as low as 10.sup.6 fold below that of the free saccharide. Since selectins are involved in recruiting cells to sites of injury, this system can be used to palliate certain inflammatory and immunological conditions.

  8. NBBS isolated from Pygeum africanum bark exhibits androgen antagonistic activity, inhibits AR nuclear translocation and prostate cancer cell growth.

    PubMed

    Papaioannou, Maria; Schleich, Sonja; Roell, Daniela; Schubert, Undine; Tanner, Tamzin; Claessens, Frank; Matusch, Rudolf; Baniahmad, Aria

    2010-12-01

    Extracts from Pygeum africanum are used in the treatment of prostatitis, benign prostatic hyperplasia (BPH) and prostate cancer (PCa). The ligand-activated human androgen receptor (AR) is known to control the growth of the prostate gland. Inhibition of human AR is therefore a major goal in treatment of patients. Here, we characterize the compound N-butylbenzene-sulfonamide (NBBS) isolated from P. africanum as a specific AR antagonist. This antihormonal activity inhibits AR- and progesterone receptor- (PR) mediated transactivation, but not the related human glucocorticoid receptor (GR) or the estrogen receptors (ERα or ERβ). Importantly, NBBS inhibits both endogenous PSA expression and growth of human PCa cells. Mechanistically, NBBS binds to AR and inhibits its translocation to the cell nucleus. Furthermore, using a battery of chemically synthesized derivatives of NBBS we revealed important structural aspects for androgen antagonism and have identified more potent AR antagonistic compounds. Our data suggest that NBBS is one of the active compounds of P. africanum bark and may serve as a naturally occurring, novel therapeutic agent for treatment of prostatic diseases. Thus, NBBS and its derivatives may serve as novel chemical platform for treatment prostatitis, BPH and PCa.

  9. AOP description: Acetylcholinesterase inhibition

    EPA Science Inventory

    This adverse outcome pathway (AOP) leverages existing knowledge in the open literature to describe the linkage between inhibition of acetylcholinesterase (AChE) and the subsequent mortality resulting from impacts at cholinergic receptors. The AOP takes a chemical category approa...

  10. Androgen Receptor Exon 1 Mutation Causes Androgen Insensitivity by Creating Phosphorylation Site and Inhibiting Melanoma Antigen-A11 Activation of NH2- and Carboxyl-terminal Interaction-dependent Transactivation*

    PubMed Central

    Lagarde, William H.; Blackwelder, Amanda J.; Minges, John T.; Hnat, Andrew T.; French, Frank S.; Wilson, Elizabeth M.

    2012-01-01

    Naturally occurring germ line mutations in the X-linked human androgen receptor (AR) gene cause incomplete masculinization of the external genitalia by disrupting AR function in males with androgen insensitivity syndrome. Almost all AR missense mutations that cause androgen insensitivity syndrome are located in the highly structured DNA and ligand binding domains. In this report we investigate the functional defect associated with an AR exon 1 missense mutation, R405S, that caused partial androgen insensitivity. The 46,XX heterozygous maternal carrier had a wild-type Arg-405 CGC allele but transmitted an AGC mutant allele coding for Ser-405. At birth, the 46,XY proband had a bifid scrotum, hypospadias, and micropenis consistent with clinical stage 3 partial androgen insensitivity. Androgen-dependent transcriptional activity of AR-R405S expressed in CV1 cells was less than wild-type AR and refractory in androgen-dependent AR NH2- and carboxyl interaction transcription assays that depend on the coregulator effects of melanoma antigen-A11. This mutation created a Ser-405 phosphorylation site evident by the gel migration of an AR-R405S NH2-terminal fragment as a double band that converted to the wild-type single band after treatment with λ-phosphatase. Detrimental effects of the R405S mutation were related to the proximity of the AR WXXLF motif 433WHTLF437 required for melanoma antigen-A11 and p300 to stimulate transcriptional activity associated with the AR NH2- and carboxyl-terminal interaction. We conclude that the coregulator effects of melanoma antigen-A11 on the AR NH2- and carboxyl-terminal interaction amplify the androgen-dependent transcriptional response to p300 required for normal human male sex development in utero. PMID:22334658

  11. JAZ mediates G1 cell cycle arrest by interacting with and inhibiting E2F1

    PubMed Central

    Yang, Mingli; Wu, Song; Jia, Jinghua

    2011-01-01

    We discovered and reported JAZ as a unique dsRNA binding zinc finger protein that functions as a direct, positive regulator of p53 transcriptional activity to mediate G1 cell cycle arrest in a mechanism involving upregulation of the p53 target gene, p21. We now find that JAZ can also negatively regulate the cell cycle in a novel, p53-independent mechanism resulting from the direct interaction with E2F1, a key intermediate in regulating cell proliferation and tumor suppression. JAZ associates with E2F1's central DNA binding/dimerization region and its C-terminal transactivation domain. Functionally, JAZ represses E2F1 transcriptional activity in association with repression of cyclin A expression and inhibition of G1/S transition. This mechanism involves JAZ-mediated inhibition of E2F1's specific DNA binding activity. JAZ directly binds E2F1 in vitro in a dsRNA-independent manner, and JAZ's dsRNA binding ZF domains, which are necessary for localizing JAZ to the nucleus, are required for repression of transcriptional activity in vivo. Importantly for specificity, siRNA-mediated “knockdown” of endogenous JAZ increases E2F transcriptional activity and releases cells from G1 arrest, indicating a necessary role for JAZ in this transition. Although JAZ can directly inhibit E2F1 activity independently of p53, if functional p53 is expressed, JAZ may exert a more potent inhibition of cell cycle following growth factor withdrawal. Therefore, JAZ plays a dual role in cell cycle regulation by both repressing E2F1 transcriptional activity and activating p53 to facilitate efficient growth arrest in response to cellular stress, which may potentially be exploited therapeutically for tumor growth inhibition. PMID:21715977

  12. Characterization of the inhibition mechanism of HIV-1 nucleocapsid protein chaperone activities by methylated oligoribonucleotides.

    PubMed

    Avilov, Sergiy V; Boudier, Christian; Gottikh, Marina; Darlix, Jean-Luc; Mély, Yves

    2012-02-01

    Since currently available therapies against HIV/AIDS still show important drawbacks, the development of novel anti-HIV treatments is a key issue. We recently characterized methylated oligoribonucleotides (mONs) that extensively inhibit HIV-1 replication in primary T cells at nanomolar concentrations. The mONs were shown to target both HIV-1 reverse transcriptase (RT) and the nucleocapsid protein (NC), which is an essential partner of RT during viral DNA synthesis. To further understand the mechanism of such mONs, we studied by isothermal titration calorimetry and fluorescence-based techniques their NC binding properties and ability to inhibit the nucleic acid chaperone properties of NC. Notably, we investigated the ability of mONs to inhibit the NC-induced destabilization of the HIV-1 cTAR (complementary DNA sequence to TAR [transactivation response element]) stem-loop and the NC-promoted cTAR annealing to its complementary sequence, required at the early stage of HIV-1 viral DNA synthesis. Moreover, we compared the activity of the mONs to that of a number of modified and nonmodified oligonucleotides. Results show that the mONs inhibit NC by a competitive mechanism whereby the mONs tightly bind the NC peptide, mainly through nonelectrostatic interactions with the hydrophobic platform at the top of the NC zinc fingers. Taken together, these results favor the notion that the mONs impair the process of the RT-directed viral DNA synthesis by sequestering NC molecules, thus preventing the chaperoning of viral DNA synthesis by NC. These findings contribute to the understanding of the molecular basis for NC inhibition by mONs, which could be used for the rational design of antiretroviral compounds targeting HIV-1 NC protein.

  13. Method for inhibiting corrosion

    SciTech Connect

    Wu, Y.; Stapp, P. R.

    1985-12-03

    A composition comprising the reaction adduct or neutralized product resulting from the reaction of a maleic anhydride and an oil containing a polynuclear aromatic compound is provided which, when applied to a metal surface, forms a corrosion-inhibiting film thereon. The composition is particularly useful in the treatment of down-hole metal surfaces in oil and gas wells to inhibit the corrosion of the metal.

  14. Farnesoid X receptor inhibits tamoxifen-resistant MCF-7 breast cancer cell growth through downregulation of HER2 expression.

    PubMed

    Giordano, C; Catalano, S; Panza, S; Vizza, D; Barone, I; Bonofiglio, D; Gelsomino, L; Rizza, P; Fuqua, S A W; Andò, S

    2011-09-29

    Tamoxifen (Tam) treatment is a first-line endocrine therapy for estrogen receptor-α-positive breast cancer patients. Unfortunately, resistance frequently occurs and is often related with overexpression of the membrane tyrosine kinase receptor HER2. This is the rationale behind combined treatments with endocrine therapy and novel inhibitors that reduce HER2 expression and signaling and thus inhibit Tam-resistant breast cancer cell growth. In this study, we show that activation of farnesoid X receptor (FXR), by the primary bile acid chenodeoxycholic acid (CDCA) or the synthetic agonist GW4064, inhibited growth of Tam-resistant breast cancer cells (termed MCF-7 TR1), which was used as an in vitro model of acquired Tam resistance. Our results demonstrate that CDCA treatment significantly reduced both anchorage-dependent and anchorage-independent epidermal growth factor (EGF)-induced growth in MCF-7 TR1 cells. Furthermore, results from western blot analysis and real-time reverse transcription-PCR revealed that CDCA treatment reduced HER2 expression and inhibited EGF-mediated HER2 and p42/44 mitogen-activated protein kinase (MAPK) phosphorylation in these Tam-resistant breast cancer cells. Transient transfection experiments, using a vector containing the human HER2 promoter region, showed that CDCA treatment downregulated basal HER2 promoter activity. This occurred through an inhibition of nuclear factor-κB transcription factor binding to its specific responsive element located in the HER2 promoter region as revealed by mutagenesis studies, electrophoretic mobility shift assay and chromatin immunoprecipitation analysis. Collectively, these data suggest that FXR ligand-dependent activity, blocking HER2/MAPK signaling, may overcome anti-estrogen resistance in human breast cancer cells and could represent a new therapeutic tool to treat breast cancer patients that develop resistance.

  15. Anthocyanidins inhibit activator protein 1 activity and cell transformation: structure-activity relationship and molecular mechanisms.

    PubMed

    Hou, De-Xing; Kai, Keiko; Li, Jian-Jian; Lin, Shigang; Terahara, Norihiko; Wakamatsu, Mika; Fujii, Makoto; Young, Mattew R; Colburn, Nancy

    2004-01-01

    Anthocyanins are the chemical components that give the intense color to many fruits and vegetables, such as blueberries, red cabbages and purple sweet potatoes. Extensive studies have indicated that anthocyanins have strong antioxidant activities. To investigate the mechanism of anthocyanidins as an anticancer food source, six kinds of anthocyanidins representing the aglycons of most anthocyanins, were used to examine their effects on tumor promotion in mouse JB6 cells, a validated model for screening cancer chemopreventive agents and elucidating the molecular mechanisms. Of the six anthocyanins tested, only those with an ortho-dihydroxyphenyl structure on the B-ring suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell transformation and activator protein-1 transactivation, suggesting that the ortho-dihydroxyphenyl may contribute to the inhibitory action. Delphinidin, but not peonidin, blocked the phosphorylation of protein kinases in the extracellular signal-regulated protein kinase (ERK) pathway at early times and the c-Jun N-terminal kinase (JNK) signaling pathway at later times. p38 kinase was not inhibited by delphinidin. Furthermore, two mitogen-activated protein kinase (MAPK) specific inhibitors (SP600125 for JNK and UO126 for ERK) could specifically block the activation of JNK and ERK and cell transformation. Those results demonstrate that anthocyanidins contribute to the inhibition of tumorigenesis by blocking activation of the MAPK pathway. These findings provide the first molecular basis for the anticarcinogenic action of anthocyanidins. PMID:14514663

  16. Galvanic zinc-copper microparticles inhibit melanogenesis via multiple pigmentary pathways.

    PubMed

    Won, Yen-Kim; Lin, Connie B; Seiberg, Miri; Chen, Nannan; Hu, Yaping; Rossetti, Dianne; Saliou, Claude; Loy, Chong-Jin

    2014-01-01

    The endogenous electrical field of human skin plays an important role in many skin functions. However, the biological effects and mechanism of action of externally applied electrical stimulation on skin remain unclear. Recent study showed that galvanic zinc-copper microparticles produce electrical stimulation and reduce inflammatory and immune responses in intact skin, suggesting the important role of electrical stimulation in non-wounded skin. The objective of this study is to investigate the biological effect of galvanic zinc-copper microparticles on skin pigmentation. Our findings showed that galvanic zinc-copper microparticles inhibited melanogenesis in a human melanoma cell line (MNT-1), human keratinocytes and melanoma cells co-cultures, and in pigmented epidermal equivalents. Treatment of galvanic zinc-copper microparticles inhibited melanogenesis by reducing the promoter transactivation of tyrosinase and tyrosinase-related protein-1 in human melanoma cells. In a co-culture Transwell system of keratinocytes and melanoma cells, galvanic zinc-copper microparticles reduced melanin production via downregulation of endothelin-1 secretion from keratinocytes and reduced tyrosinase gene expression in melanoma cells. In addition, exposure of pigmented epidermal equivalents to galvanic zinc-copper microparticles resulted in reduced melanin deposition. In conclusion, our data demonstrated for the first time that galvanic zinc-copper microparticles reduced melanogenesis in melanoma cells and melanin deposition in pigmented epidermal equivalents by affecting multiple pigmentary pathways. PMID:23700242

  17. Galvanic zinc-copper microparticles inhibit melanogenesis via multiple pigmentary pathways.

    PubMed

    Won, Yen-Kim; Lin, Connie B; Seiberg, Miri; Chen, Nannan; Hu, Yaping; Rossetti, Dianne; Saliou, Claude; Loy, Chong-Jin

    2014-01-01

    The endogenous electrical field of human skin plays an important role in many skin functions. However, the biological effects and mechanism of action of externally applied electrical stimulation on skin remain unclear. Recent study showed that galvanic zinc-copper microparticles produce electrical stimulation and reduce inflammatory and immune responses in intact skin, suggesting the important role of electrical stimulation in non-wounded skin. The objective of this study is to investigate the biological effect of galvanic zinc-copper microparticles on skin pigmentation. Our findings showed that galvanic zinc-copper microparticles inhibited melanogenesis in a human melanoma cell line (MNT-1), human keratinocytes and melanoma cells co-cultures, and in pigmented epidermal equivalents. Treatment of galvanic zinc-copper microparticles inhibited melanogenesis by reducing the promoter transactivation of tyrosinase and tyrosinase-related protein-1 in human melanoma cells. In a co-culture Transwell system of keratinocytes and melanoma cells, galvanic zinc-copper microparticles reduced melanin production via downregulation of endothelin-1 secretion from keratinocytes and reduced tyrosinase gene expression in melanoma cells. In addition, exposure of pigmented epidermal equivalents to galvanic zinc-copper microparticles resulted in reduced melanin deposition. In conclusion, our data demonstrated for the first time that galvanic zinc-copper microparticles reduced melanogenesis in melanoma cells and melanin deposition in pigmented epidermal equivalents by affecting multiple pigmentary pathways.

  18. BRCA1 and its phosphorylation involved in caffeine-inhibitable event upstream of G2 checkpoint

    NASA Astrophysics Data System (ADS)

    Li, Ning; Zhang, Hong; Wang, Yanling; Hao, Jifang

    2010-07-01

    Caffeine, which specifically inhibits ATM/ATR kinases, efficiently abrogates the ionizing radiation (IR)-induced G2 arrest and increases the sensitivity of various tumor cells to IR. Mechanisms for the effect of caffeine remain to be elucidated. As a target of ATM/ATR kinases, BRCA1 becomes activated and phosphorylated in response to IR. Thus, in this work, we investigated the possible role of BRCA1 in the effect of caffeine on G2 checkpoint and observed how BRCA1 phosphorylation was regulated in this process. For these purposes, the BRCA1 protein level and the phosphorylation states were analyzed by Western blotting by using an antibody against BRCA1 and phospho-specific antibodies against Ser-1423 and Ser-1524 residues in cells exposed to a combination of IR and caffeine. The results showed that caffeine down-regulated IR-induced BRCA1 expression and specifically abolished BRCA1 phosphorylation of Ser-1524, which was followed by an override of G2 arrest by caffeine. In addition, the ability of BRCA1 to transactivate p21 may be required for MCF-7 but not necessary for Hela response to caffeine. These data suggest that BRCA1 may be a potential target of caffeine. BRCA1 and its phosphorylation are most likely to be involved in the caffeine-inhibitable event upstream of G2 arrest.

  19. Pharmacologic efficacy of PU.1 inhibition by heterocyclic dications: a mechanistic analysis

    PubMed Central

    Stephens, Dominique C.; Kim, Hye Mi; Kumar, Arvind; Farahat, Abdelbasset A.; Boykin, David W.; K. Poon, Gregory M.

    2016-01-01

    Heterocyclic dications are receiving increasing attention as targeted inhibitors of transcription factors. While many dications act as purely competitive inhibitors, some fail to displace protein efficiently at drug concentrations expected to saturate their DNA target. To achieve a mechanistic understanding of these non-competitive effects, we used a combination of dications, which are intrinsically fluorescent and spectrally-separated fluorescently labeled DNA to dissect complex interactions in multi-component drug/DNA/protein systems. Specifically, we interrogated site-specific binding by the transcription factor PU.1 and its perturbation by DB270, a furan-bisbenzimidazole-diamidine that strongly targets PU.1 binding sites yet poorly inhibits PU.1/DNA complexes. By titrating DB270 and/or cyanine-labeled DNA with protein or unlabeled DNA, and following the changes in their fluorescence polarization, we found direct evidence that DB270 bound protein independently of their mutual affinities for sequence-specific DNA. Each of the three species competed for the other two, and this interplay of mutually dependent equilibria abrogated DB270's inhibitory activity, which was substantively restored under conditions that attenuated DB270/PU.1 binding. PU.1 binding was consistent with DB270's poor inhibitory efficacy of PU.1 in vivo, while its isosteric selenophene analog (DB1976), which did not bind PU.1 and strongly inhibited the PU.1/DNA complex in vitro, fully antagonized PU.1-dependent transactivation in vivo. PMID:27079976

  20. Pharmacologic efficacy of PU.1 inhibition by heterocyclic dications: a mechanistic analysis.

    PubMed

    Stephens, Dominique C; Kim, Hye Mi; Kumar, Arvind; Farahat, Abdelbasset A; Boykin, David W; K Poon, Gregory M

    2016-05-19

    Heterocyclic dications are receiving increasing attention as targeted inhibitors of transcription factors. While many dications act as purely competitive inhibitors, some fail to displace protein efficiently at drug concentrations expected to saturate their DNA target. To achieve a mechanistic understanding of these non-competitive effects, we used a combination of dications, which are intrinsically fluorescent and spectrally-separated fluorescently labeled DNA to dissect complex interactions in multi-component drug/DNA/protein systems. Specifically, we interrogated site-specific binding by the transcription factor PU.1 and its perturbation by DB270, a furan-bisbenzimidazole-diamidine that strongly targets PU.1 binding sites yet poorly inhibits PU.1/DNA complexes. By titrating DB270 and/or cyanine-labeled DNA with protein or unlabeled DNA, and following the changes in their fluorescence polarization, we found direct evidence that DB270 bound protein independently of their mutual affinities for sequence-specific DNA. Each of the three species competed for the other two, and this interplay of mutually dependent equilibria abrogated DB270's inhibitory activity, which was substantively restored under conditions that attenuated DB270/PU.1 binding. PU.1 binding was consistent with DB270's poor inhibitory efficacy of PU.1 in vivo, while its isosteric selenophene analog (DB1976), which did not bind PU.1 and strongly inhibited the PU.1/DNA complex in vitro, fully antagonized PU.1-dependent transactivation in vivo.

  1. E2A Antagonizes PU.1 Activity through Inhibition of DNA Binding.

    PubMed

    Rogers, Jason H; Owens, Kristin S; Kurkewich, Jeffrey; Klopfenstein, Nathan; Iyer, Sangeeta R; Simon, M Celeste; Dahl, Richard

    2016-01-01

    Antagonistic interactions between transcription factors contribute to cell fate decisions made by multipotent hematopoietic progenitor cells. Concentration of the transcription factor PU.1 affects myeloid/lymphoid development with high levels of PU.1 directing myeloid cell fate acquisition at the expense of B cell differentiation. High levels of PU.1 may be required for myelopoiesis in order to overcome inhibition of its activity by transcription factors that promote B cell development. The B cell transcription factors, E2A and EBF, are necessary for commitment of multipotential progenitors and lymphoid primed multipotential progenitors to lymphocytes. In this report we hypothesized that factors required for early B cell commitment would bind to PU.1 and antagonize its ability to induce myeloid differentiation. We investigated whether E2A and/or EBF associate with PU.1. We observed that the E2A component, E47, but not EBF, directly binds to PU.1. Additionally E47 represses PU.1-dependent transactivation of the MCSFR promoter through antagonizing PU.1's ability to bind to DNA. Exogenous E47 expression in hematopoietic cells inhibits myeloid differentiation. Our data suggest that E2A antagonism of PU.1 activity contributes to its ability to commit multipotential hematopoietic progenitors to the lymphoid lineages.

  2. Anthocyanidins inhibit activator protein 1 activity and cell transformation: structure-activity relationship and molecular mechanisms.

    PubMed

    Hou, De-Xing; Kai, Keiko; Li, Jian-Jian; Lin, Shigang; Terahara, Norihiko; Wakamatsu, Mika; Fujii, Makoto; Young, Mattew R; Colburn, Nancy

    2004-01-01

    Anthocyanins are the chemical components that give the intense color to many fruits and vegetables, such as blueberries, red cabbages and purple sweet potatoes. Extensive studies have indicated that anthocyanins have strong antioxidant activities. To investigate the mechanism of anthocyanidins as an anticancer food source, six kinds of anthocyanidins representing the aglycons of most anthocyanins, were used to examine their effects on tumor promotion in mouse JB6 cells, a validated model for screening cancer chemopreventive agents and elucidating the molecular mechanisms. Of the six anthocyanins tested, only those with an ortho-dihydroxyphenyl structure on the B-ring suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell transformation and activator protein-1 transactivation, suggesting that the ortho-dihydroxyphenyl may contribute to the inhibitory action. Delphinidin, but not peonidin, blocked the phosphorylation of protein kinases in the extracellular signal-regulated protein kinase (ERK) pathway at early times and the c-Jun N-terminal kinase (JNK) signaling pathway at later times. p38 kinase was not inhibited by delphinidin. Furthermore, two mitogen-activated protein kinase (MAPK) specific inhibitors (SP600125 for JNK and UO126 for ERK) could specifically block the activation of JNK and ERK and cell transformation. Those results demonstrate that anthocyanidins contribute to the inhibition of tumorigenesis by blocking activation of the MAPK pathway. These findings provide the first molecular basis for the anticarcinogenic action of anthocyanidins.

  3. Inhibition of Axl improves the targeted therapy against ALK-mutated neuroblastoma

    SciTech Connect

    Xu, Fei; Li, Hongling; Sun, Yong

    2014-11-28

    Highlights: • First reported Axl is co-expressed with ALK in neuroblastoma tissues and cell lines. • Axl activation promotes cell growth and impairs the efficiency of ALK inhibitor. • Further found silence of Axl leads to increased sensitivity to ALK inhibitors. • Axl inhibitor promotes the efficiency of targeted therapy in vitro and in vivo. • Axl activation should be considered in the clinical application of ALK inhibitors. - Abstract: Neuroblastoma (NB) patients harboring mutated ALK can be expected to potentially benefit from targeted therapy based on ALK tyrosine kinase inhibitor (TKI), such as crizotinib and ceritinib. However, the effect of the treatment varies with different individuals, although with the same genic changes. Axl receptor tyrosine kinase is expressed in a variety of human cancers, but little data are reported in NB, particularly in which carrying mutated ALK. In this study, we focus on the roles of Axl in ALK-mutated NB for investigating rational therapeutic strategy. We found that Axl is expressed in ALK-positive NB tissues and cell lines, and could be effectively activated by its ligand GAS6. Ligand-dependent Axl activation obviously rescued crizotinib-mediated suppression of cell proliferation in ALK-mutated NB cells. Genetic inhibition of Axl with specific small interfering RNA markedly increased the sensitivity of cells to ALK-TKIs. Furthermore, a small-molecule inhibitor of Axl significantly enhanced ALK-targeted therapy, as an increased frequency of apoptosis was observed in NB cells co-expressing ALK and Axl. Taken together, our results demonstrated that activation of Axl could lead to insensitivity to ALK inhibitors, and dual inhibition of ALK and Axl might be a potential therapeutic strategy against ALK-mutated NB.

  4. p-HPEA-EDA, a phenolic compound of virgin olive oil, activates AMP-activated protein kinase to inhibit carcinogenesis.

    PubMed

    Khanal, Prem; Oh, Won-Keun; Yun, Hyo Jeong; Namgoong, Gwang Mo; Ahn, Sang-Gun; Kwon, Seong-Min; Choi, Hoo-Kyun; Choi, Hong Seok

    2011-04-01

    Phenolic constituents of virgin olive oil are reported to have antitumor activity. However, the underlying molecular mechanisms and specific target proteins of virgin olive oil remain to be elucidated. Here, we report that dialdehydic form of decarboxymethyl ligstroside aglycone (p-HPEA-EDA), a phenolic compound of virgin olive oil, inhibits tumor promoter-induced cell transformation in JB6 Cl41 cells and suppress cyclooxygenase-2 (COX-2) and tumorigenicity by adenosine monophosphate-activated protein kinase (AMPK) activation in HT-29 cells. p-HPEA-EDA inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced phosphorylation of extracellular signal-regulated kinases 1/2 and p90RSK in JB6 Cl41 cells, resulting in the inhibition of cell proliferation, activator protein-1 transactivation and cell transformation promoted by TPA. Moreover, p-HPEA-EDA strongly inhibited the cell viability and COX-2 expression by activation of AMPK activity in HT-29 cells, resulted from depletion of intracellular adenosine triphosphate. p-HPEA-EDA-induced activation of caspase-3 and poly-adenosine diphosphate-ribose polymerase, phosphorylation of p53 (Ser15) and DNA fragmentation in HT-29 cells, leading to apoptosis. Importantly, p-HPEA-EDA suppressed the colony formation of HT-29 cells in soft agar. In contrast, Compound C, an AMPK inhibitor, and Z-DEVD-FMK, a caspase-3 inhibitor, blocked the p-HPEA-EDA-inhibited colony formation in HT-29 cells. In vivo chorioallantoic membrane assay also showed that p-HPEA-EDA-inhibited tumorigenicity of HT-29 cells. These findings revealed that targeted activation of AMPK and inhibition of COX-2 expression by p-HPEA-EDA contribute to the chemopreventive and chemotherapeutic potential of virgin olive oil against colon cancer cells. PMID:21216846

  5. Brown Pine Leaf Extract and Its Active Component Trans-Communic Acid Inhibit UVB-Induced MMP-1 Expression by Targeting PI3K.

    PubMed

    Huh, Won Bum; Kim, Jong-Eun; Kang, Young-Gyu; Park, Gaeun; Lim, Tae-gyu; Kwon, Jung Yeon; Song, Da Som; Jeong, Eun Hee; Lee, Charles C; Son, Joe Eun; Seo, Sang Gwon; Lee, Eunjung; Kim, Jong Rhan; Lee, Chang Yong; Park, Jun Seong; Lee, Ki Won

    2015-01-01

    Japanese red pine (Pinus densiflora) is widely present in China, Japan, and Korea. Its green pine leaves have traditionally been used as a food as well as a coloring agent. After being shed, pine leaves change their color from green to brown within two years, and although the brown pine leaves are abundantly available, their value has not been closely assessed. In this study, we investigated the potential anti-photoaging properties of brown pine leaves for skin. Brown pine leaf extract (BPLE) inhibited UVB-induced matrix metalloproteinase-1 (MMP-1) expression to a greater extent than pine leaf extract (PLE) in human keratinocytes and a human skin equivalent model. HPLC analysis revealed that the quantity of trans-communic acid (TCA) and dehydroabietic acid (DAA) significantly increases when the pine leaf color changes from green to brown. BPLE and TCA elicited reductions in UVB-induced MMP-1 mRNA expression and activator protein-1 (AP-1) transactivation by reducing DNA binding activity of phospho-c-Jun, c-fos and Fra-1. BPLE and TCA also inhibited UVB-induced Akt phosphorylation, but not mitogen activated protein kinase (MAPK), known regulators of AP-1 transactivation. We additionally found that BPLE and TCA inhibited phosphoinositide 3-kinase (PI3K), the upstream kinase of Akt, in vitro. In summary, both BPLE and its active component TCA exhibit protective effects against UVB-induced skin aging. Taken together, these findings underline the potential for BPLE and TCA to be utilized as anti-wrinkling agents and cosmetic ingredients, as they suppress UVB-induced MMP-1 expression.

  6. Brown Pine Leaf Extract and Its Active Component Trans-Communic Acid Inhibit UVB-Induced MMP-1 Expression by Targeting PI3K

    PubMed Central

    Park, Gaeun; Lim, Tae-gyu; Kwon, Jung Yeon; Song, Da Som; Jeong, Eun Hee; Lee, Charles C.; Son, Joe Eun; Seo, Sang Gwon; Lee, Eunjung; Kim, Jong Rhan; Lee, Chang Yong; Park, Jun Seong; Lee, Ki Won

    2015-01-01

    Japanese red pine (Pinus densiflora) is widely present in China, Japan, and Korea. Its green pine leaves have traditionally been used as a food as well as a coloring agent. After being shed, pine leaves change their color from green to brown within two years, and although the brown pine leaves are abundantly available, their value has not been closely assessed. In this study, we investigated the potential anti-photoaging properties of brown pine leaves for skin. Brown pine leaf extract (BPLE) inhibited UVB-induced matrix metalloproteinase-1 (MMP-1) expression to a greater extent than pine leaf extract (PLE) in human keratinocytes and a human skin equivalent model. HPLC analysis revealed that the quantity of trans-communic acid (TCA) and dehydroabietic acid (DAA) significantly increases when the pine leaf color changes from green to brown. BPLE and TCA elicited reductions in UVB-induced MMP-1 mRNA expression and activator protein-1 (AP-1) transactivation by reducing DNA binding activity of phospho-c-Jun, c-fos and Fra-1. BPLE and TCA also inhibited UVB-induced Akt phosphorylation, but not mitogen activated protein kinase (MAPK), known regulators of AP-1 transactivation. We additionally found that BPLE and TCA inhibited phosphoinositide 3-kinase (PI3K), the upstream kinase of Akt, in vitro. In summary, both BPLE and its active component TCA exhibit protective effects against UVB-induced skin aging. Taken together, these findings underline the potential for BPLE and TCA to be utilized as anti-wrinkling agents and cosmetic ingredients, as they suppress UVB-induced MMP-1 expression. PMID:26066652

  7. RAR agonists stimulate SOX9 gene expression in breast cancer cell lines: evidence for a role in retinoid-mediated growth inhibition.

    PubMed

    Afonja, Olubunmi; Raaka, Bruce M; Huang, Ambrose; Das, Sharmistha; Zhao, Xinyu; Helmer, Elizabeth; Juste, Dominique; Samuels, Herbert H

    2002-11-01

    Retinoic acid receptors (RARs) are ligand-dependent transcription factors which are members of the steroid/thyroid hormone receptor gene family. RAR-agonists inhibit the proliferation of many human breast cancer cell lines, particularly those whose growth is stimulated by estradiol (E2) or growth factors. PCR-amplified subtractive hybridization was used to identify candidate retinoid-regulated genes that may be involved in growth inhibition. One candidate gene identified was SOX9, a member of the high mobility group (HMG) box gene family of transcription factors. SOX9 gene expression is rapidly stimulated by RAR-agonists in T-47D cells and other retinoid-inhibited breast cancer cell lines. In support of this finding, a database search indicates that SOX9 is expressed as an EST in breast tumor cells. SOX9 is known to be expressed in chondrocytes where it regulates the transcription of type II collagen and in testes where it plays a role in male sexual differentiation. RAR pan-agonists and the RARalpha-selective agonist Am580, but not RXR agonists, stimulate the expression of SOX9 in a wide variety of retinoid-inhibited breast cancer cell lines. RAR-agonists did not stimulate SOX9 in breast cancer cell lines which were not growth inhibited by retinoids. Expression of SOX9 in T-47D cells leads to cycle changes similar to those found with RAR-agonists while expression of a dominant negative form of SOX9 blocks RA-mediated cell cycle changes, suggesting a role for SOX9 in retinoid-mediated growth inhibition.

  8. In brown adipocytes, adrenergically induced β{sub 1}-/β{sub 3}-(G{sub s})-, α{sub 2}-(G{sub i})- and α{sub 1}-(G{sub q})-signalling to Erk1/2 activation is not mediated via EGF receptor transactivation

    SciTech Connect

    Wang, Yanling; Fälting, Johanna M.; Mattsson, Charlotte L.; Holmström, Therése E.; Nedergaard, Jan

    2013-10-15

    Brown adipose tissue is unusual in that the neurotransmitter norepinephrine influences cell destiny in ways generally associated with effects of classical growth factors: regulation of cell proliferation, of apoptosis, and progression of differentiation. The norepinephrine effects are mediated through G-protein-coupled receptors; further mediation of such stimulation to e.g. Erk1/2 activation is in cell biology in general accepted to occur through transactivation of the EGF receptor (by external or internal pathways). We have examined here the significance of such transactivation in brown adipocytes. Stimulation of mature brown adipocytes with cirazoline (α{sub 1}-adrenoceptor coupled via G{sub q}), clonidine (α{sub 2} via G{sub i}) or CL316243 (β{sub 3} via G{sub s}) or via β{sub 1}-receptors significantly activated Erk1/2. Pretreatment with the EGF receptor kinase inhibitor AG1478 had, remarkably, no significant effect on Erk1/2 activation induced by any of these adrenergic agonists (although it fully abolished EGF-induced Erk1/2 activation), demonstrating absence of EGF receptor-mediated transactivation. Results with brown preadipocytes (cells in more proliferative states) were not qualitatively different. Joint stimulation of all adrenoceptors with norepinephrine did not result in synergism on Erk1/2 activation. AG1478 action on EGF-stimulated Erk1/2 phosphorylation showed a sharp concentration–response relationship (IC{sub 50} 0.3 µM); a minor apparent effect of AG1478 on norepinephrine-stimulated Erk1/2 phosphorylation showed nonspecific kinetics, implying caution in interpretation of partial effects of AG1478 as reported in other systems. Transactivation of the EGF receptor is clearly not a universal prerequisite for coupling of G-protein coupled receptors to Erk1/2 signalling cascades. - Highlights: • In brown adipocytes, norepinephrine regulates proliferation, apoptosis, differentiation. • EGF receptor transactivation is supposed to mediate GPCR

  9. A novel point mutation in the ligand-binding domain (LBD) of the human glucocorticoid receptor (hGR) causing generalized glucocorticoid resistance: the importance of the C terminus of hGR LBD in conferring transactivational activity.

    PubMed

    Charmandari, Evangelia; Raji, Annaswamy; Kino, Tomoshige; Ichijo, Takamasa; Tiulpakov, Anatoly; Zachman, Keith; Chrousos, George P

    2005-06-01

    Glucocorticoid resistance is a rare, familial or sporadic condition characterized by partial end-organ insensitivity to glucocorticoids. The clinical spectrum of the condition is broad, ranging from completely asymptomatic to severe hyperandrogenism and/or mineralocorticoid excess. The molecular basis of glucocorticoid resistance has been ascribed to mutations in the human glucocorticoid receptor-alpha (hGRalpha) gene, which impair one or more of the molecular mechanisms of GR action, thus altering tissue sensitivity to glucocorticoids. We identified a new case of generalized glucocorticoid resistance in a young woman who presented with a long-standing history of fatigue, anxiety, hyperandrogenism, and hypertension. The disease was caused by a novel, heterozygous mutation (T-->C) at nucleotide position 2318 (exon 9) of the hGRalpha gene, which resulted in substitution of leucine by proline at amino acid position 773 in the ligand-binding domain of the receptor. We systematically investigated the molecular mechanisms through which the natural hGRalphaL773P mutant impaired glucocorticoid signal transduction. Compared with the wild-type hGRalpha, hGRalphaL773P demonstrated a 2-fold reduction in the ability to transactivate the glucocorticoid-inducible mouse mammary tumor virus promoter, exerted a dominant negative effect on the wild-type receptor, had a 2.6-fold reduction in the affinity for ligand, showed delayed nuclear translocation (30 vs. 12 min), and, although it preserved its ability to bind to DNA, displayed an abnormal interaction with the GR-interacting protein 1 coactivator in vitro. We conclude that the carboxyl terminus of the ligand-binding domain of hGRalpha is extremely important in conferring transactivational activity by altering multiple functions of this composite transcription factor. PMID:15769988

  10. Addiction of lung cancer cells to GOF p53 is promoted by up-regulation of epidermal growth factor receptor through multiple contacts with p53 transactivation domain and promoter

    PubMed Central

    Vaughan, Catherine A.; Pearsall, Isabella; Singh, Shilpa; Windle, Brad; Deb, Swati P.; Grossman, Steven R.; Yeudall, W. Andrew; Deb, Sumitra

    2016-01-01

    Human lung cancers harboring gain-of-function (GOF) p53 alleles express higher levels of the epidermal growth factor receptor (EGFR). We demonstrate that a number of GOF p53 alleles directly upregulate EGFR. Knock-down of p53 in lung cancer cells lowers EGFR expression and reduces tumorigenicity and other GOF p53 properties. However, addiction of lung cancer cells to GOF p53 can be compensated by overexpressing EGFR, suggesting that EGFR plays a critical role in addiction. Chromatin immunoprecipitation (ChIP) using lung cancer cells expressing GOF p53 alleles showed that GOF p53 localized to the EGFR promoter. The sequence where GOF p53 is found to interact by ChIP seq can act as a GOF p53 response element. The presence of GOF p53 on the EGFR promoter increased histone H3 acetylation, indicating a mechanism whereby GOF p53 enhances chromatin opening for improved access to transcription factors (TFs). ChIP and ChIP-re-ChIP with p53, Sp1 and CBP histone acetylase (HAT) antibodies revealed docking of GOF p53 on Sp1, leading to increased binding of Sp1 and CBP to the EGFR promoter. Up-regulation of EGFR can occur via GOF p53 contact at other novel sites in the EGFR promoter even when TAD-I is inactivated; these sites are used by both intact and TAD-I mutated GOF p53 and might reflect redundancy in GOF p53 mechanisms for EGFR transactivation. Thus, the oncogenic action of GOF p53 in lung cancer is highly dependent on transactivation of the EGFR promoter via a novel transcriptional mechanism involving coordinated interactions of TFs, HATs and GOF p53. PMID:26820293

  11. Cancer/Testis Antigen PAGE4, a Regulator of c-Jun Transactivation, Is Phosphorylated by Homeodomain-Interacting Protein Kinase 1, a Component of the Stress-Response Pathway

    PubMed Central

    2015-01-01

    Prostate-associated gene 4 (PAGE4) is a cancer/testis antigen that is typically restricted to the testicular germ cells but is aberrantly expressed in cancer. Furthermore, PAGE4 is developmentally regulated with dynamic expression patterns in the developing prostate and is also a stress-response protein that is upregulated in response to cellular stress. PAGE4 interacts with c-Jun, which is activated by the stress-response kinase JNK1, and plays an important role in the development and pathology of the prostate gland. Here, we have identified homeodomain-interacting protein kinase 1 (HIPK1), also a component of the stress-response pathway, as a kinase that phosphorylates PAGE4 at T51. We show that phosphorylation of PAGE4 is critical for its transcriptional activity since mutating this T residue abolishes its ability to potentiate c-Jun transactivation. In vitro single molecule FRET indicates phosphorylation results in compaction of (still) intrinsically disordered PAGE4. Interestingly, however, while our previous observations indicated that the wild-type nonphosphorylated PAGE4 protein interacted with c-Jun [RajagopalanK. et al. (2014) Biochim, Biophys. Acta1842, 154−16324263171], here we show that phosphorylation of PAGE4 weakens its interaction with c-Jun in vitro. These data suggest that phosphorylation induces conformational changes in natively disordered PAGE4 resulting in its decreased affinity for c-Jun to promote interaction of c-Jun with another, unidentified, partner. Alternatively, phosphorylated PAGE4 may induce transcription of a novel partner, which then potentiates c-Jun transactivation. Regardless, the present results clearly implicate PAGE4 as a component of the stress-response pathway and uncover a novel link between components of this pathway and prostatic development and disease. PMID:24559171

  12. Efficient translation of distal cistrons of a polycistronic mRNA of a plant pararetrovirus requires a compatible interaction between the mRNA 3' end and the proteinaceous trans-activator.

    PubMed

    Edskes, H K; Kiernan, J M; Shepherd, R J

    1996-10-15

    Caulimoviruses, a type of plant pararetrovirus, employ a highly unusual mechanism to express the multiple cistrons of their pregenomic RNA. It involves translation of a polycistronic mRNA utilizing cis-acting viral RNA sequences and a transacting virus-encoded protein (P6). In addition to its role in polycistronic translation, the translational trans-activator protein P6 also activates its own expression from a monocistronic subgenomic RNA. Using Nicotiana Edwardsonii cell suspension protoplasts, we analyzed the ability of P6 proteins from three different caulimoviruses to activate viral RNA-based reporter constructs. Cis-acting elements present in figwort mosaic caulimovirus (FMV) are functional not only in the presence of the cognate P6 activator protein, but also in the presence of the heterologous activators from cauliflower mosaic caulimovirus (CaMV) and peanut chlorotic streak caulimovirus (PCISV). However, when 3' cis-acting elements essential for efficient polycistronic expression of FMV are replaced by their counterparts from PCISV, reporter gene expression is only observed in the presence of PCISV P6. Derepression of monocistronic reporter constructs tailed with FMV or CaMV 3' proximal sequences is less efficient in the presence of PCISV P6 than with either FMV or CaMV P6, but more efficient when the constructs contain a cognate PCISV 3' cis-element. Efficient expression of polycistronic and monocistronic caulimovirus mRNAs in plant cells thus requires compatible interactions between P6, a translational trans-activator, and its cognate cis-element at the 3' end of the mRNA.

  13. Identification of functional domains of the IR2 protein of equine herpesvirus 1 required for inhibition of viral gene expression and replication

    SciTech Connect

    Kim, Seong K. Kim, Seongman; Dai Gan; Zhang Yunfei; Ahn, Byung C.; O'Callaghan, Dennis J.

    2011-09-01

    The equine herpesvirus 1 (EHV-1) negative regulatory IR2 protein (IR2P), an early 1,165-amino acid (aa) truncated form of the 1487-aa immediate-early protein (IEP), lacks the trans-activation domain essential for IEP activation functions but retains domains for binding DNA, TFIIB, and TBP and the nuclear localization signal. IR2P mutants of the N-terminal region which lack either DNA-binding activity or TFIIB-binding activity were unable to down-regulate EHV-1 promoters. In EHV-1-infected cells expressing full-length IR2P, transcription and protein expression of viral regulatory IE, early EICP0, IR4, and UL5, and late ETIF genes were dramatically inhibited. Viral DNA levels were reduced to 2.1% of control infected cells, but were vey weakly affected in cells that express the N-terminal 706 residues of IR2P. These results suggest that IR2P function requires the two N-terminal domains for binding DNA and TFIIB as well as the C-terminal residues 707 to 1116 containing the TBP-binding domain. - Highlights: > We examine the functional domains of IR2P that mediates negative regulation. > IR2P inhibits at the transcriptional level. > DNA-binding mutant or TFIIB-binding mutant fails to inhibit. > C-terminal aa 707 to 1116 are required for full inhibition. > Inhibition requires the DNA-binding domain, TFIIB-binding domain, and C-terminus.

  14. Zinc Inhibits Hedgehog Autoprocessing

    PubMed Central

    Xie, Jian; Owen, Timothy; Xia, Ke; Singh, Ajay Vikram; Tou, Emiley; Li, Lingyun; Arduini, Brigitte; Li, Hongmin; Wan, Leo Q.; Callahan, Brian; Wang, Chunyu

    2015-01-01

    Zinc is an essential trace element with wide-ranging biological functions, whereas the Hedgehog (Hh) signaling pathway plays crucial roles in both development and disease. Here we show that there is a mechanistic link between zinc and Hh signaling. The upstream activator of Hh signaling, the Hh ligand, originates from Hh autoprocessing, which converts the Hh precursor protein to the Hh ligand. In an in vitro Hh autoprocessing assay we show that zinc inhibits Hh autoprocessing with a Ki of 2 μm. We then demonstrate that zinc inhibits Hh autoprocessing in a cellular environment with experiments in primary rat astrocyte culture. Solution NMR reveals that zinc binds the active site residues of the Hh autoprocessing domain to inhibit autoprocessing, and isothermal titration calorimetry provided the thermodynamics of the binding. In normal physiology, zinc likely acts as a negative regulator of Hh autoprocessing and inhibits the generation of Hh ligand and Hh signaling. In many diseases, zinc deficiency and elevated level of Hh ligand co-exist, including prostate cancer, lung cancer, ovarian cancer, and autism. Our data suggest a causal relationship between zinc deficiency and the overproduction of Hh ligand. PMID:25787080

  15. Nitric oxide inhibition strategies

    PubMed Central

    Wong, Vivian (Wai Chong); Lerner, Ethan

    2015-01-01

    Nitric oxide is involved in many physiologic processes. There are efforts, described elsewhere in this volume, to deliver nitric oxide to tissues as a therapy. Nitric oxide also contributes to pathophysiologic processes. Inhibiting nitric oxide or its production can thus also be of therapeutic benefit. This article addresses such inhibitory strategies. PMID:26634146

  16. Overexpression of Mxi1 inhibits the induction of the human ornithine decarboxylase gene by the Myc/Max protein complex.

    PubMed

    Wu, S; Peña, A; Korcz, A; Soprano, D R; Soprano, K J

    1996-02-01

    We have previously shown that the Myc/Max protein complex plays a role in the growth-associated expression of the human ornithine decarboxylase gene. Mxi1 and Mad, novel Max-associated proteins have been identified and shown to form heterodimers with Max which bind efficiently to the Myc/Max consensus recognition sequence, CACGTG, in vitro. However, formation of Max/Mxi1 or Max/Mad heterodimers results in a reduction in Myc/Max dependent transcriptional activation of reporter plasmid constructs containing the consensus element. In light of the evidence that ODC is transcriptionally regulated in vitro and in vivo by the Myc/Max protein complex and the potential role of Mxi1 and Mad as antagonists of Myc transactivation activity, we set out to determine if one of these Max associated proteins, Mxi1, could affect the regulation of ODC expression by Myc/Max and if this regulation was correlated to growth status. Our results show that overexpression of Mxi1 does in fact inhibit ODC gene expression in a dose-dependent manner both in vivo and in vitro. In addition, evidence is presented which shows that levels of Mxi1 are up-regulated during long term quiescence and down-regulated following growth stimulation by serum. These results suggest that alterations in the levels of Max-associated proteins such as Mxi1 can modulate critical levels of functional Myc/Max protein complexes. This can alter transcriptional transactivation of Myc-regulated targets and as a consequence affect levels of genes essential for initiation and/or maintenance of growth.

  17. Mutation of androgen receptor N-terminal phosphorylation site Tyr-267 leads to inhibition of nuclear translocation and DNA binding.

    PubMed

    Karaca, Mehmet; Liu, Yuanbo; Zhang, Zhentao; De Silva, Dinuka; Parker, Joel S; Earp, H Shelton; Whang, Young E

    2015-01-01

    Reactivation of androgen receptor (AR) may drive recurrent prostate cancer in castrate patients. Ack1 tyrosine kinase is overexpressed in prostate cancer and promotes castrate resistant xenograft tumor growth and enhances androgen target gene expression and AR recruitment to enhancers. Ack1 phosphorylates AR at Tyr-267 and possibly Tyr-363, both in the N-terminal transactivation domain. In this study, the role of these phosphorylation sites was investigated by characterizing the phosphorylation site mutants in the context of full length and truncated AR lacking the ligand-binding domain. Y267F and Y363F mutants showed decreased transactivation of reporters. Expression of wild type full length and truncated AR in LNCaP cells increased cell proliferation in androgen-depleted conditions and increased colony formation. However, the Y267F mutant of full length and truncated AR was defective in stimulating cell proliferation. The Y363F mutant was less severely affected than the Y267F mutant. The full length AR Y267F mutant was defective in nuclear translocation induced by androgen or Ack1 kinase. The truncated AR was constitutively localized to the nucleus. Chromatin immunoprecipitation analysis showed that it was recruited to the target enhancers without androgen. The truncated Y267F AR mutant did not exhibit constitutive nuclear localization and androgen enhancer binding activity. These results support the concept that phosphorylation of Tyr-267, and to a lesser extent Tyr-363, is required for AR nuclear translocation and recruitment and DNA binding and provide a rationale for development of novel approaches to inhibit AR activity.

  18. Mutations which affect the inhibition of protein phosphatase 2A by simian virus 40 small-t antigen in vitro decrease viral transformation.

    PubMed Central

    Mungre, S; Enderle, K; Turk, B; Porrás, A; Wu, Y Q; Mumby, M C; Rundell, K

    1994-01-01

    Three independent point mutations within residues 97 to 103 of the simian virus 40-small-t antigen (small-t) greatly reduced the ability of purified small-t to inhibit protein phosphatase 2A in vitro. These mutations affected the interaction of small-t antigen with the protein phosphatase 2A A subunit translated in vitro, and a peptide from the region identified by these mutations released the A subunit from immune complexes. When introduced into virus, the mutations eliminated the ability of small-t to enhance viral transformation of growth-arrested rat F111 cells. In contrast, the mutant small-t antigens were unimpaired in the transactivation of the adenovirus E2 promoter, an activity which was reduced by a double mutation in small-t residues 43 and 45. Images PMID:8107228

  19. The naturally occurring biflavonoid, ochnaflavone, inhibits LPS-induced iNOS expression, which is mediated by ERK1/2 via NF-kappaB regulation, in RAW264.7 cells.

    PubMed

    Suh, Seok-Jong; Chung, Tae-Wook; Son, Min-Jung; Kim, Sung-Hoon; Moon, Tae Chul; Son, Kun Ho; Kim, Hyun Pyo; Chang, Hyeun Wook; Kim, Cheorl-Ho

    2006-03-15

    Ochnaflavone (OC), a naturally occurring biflavonoid with anti-inflammatory activity [S.J. Lee, J.H. Choi, H.W. Chang, S.S. Kang, H.P. Kim. Life Sci. 57(6), 1995, 551-558], was isolated from Lonicera japonica and its effects on inducible nitric oxide synthase (iNOS) gene expression was examined in RAW264.7 cells. U0126, an inhibitor of the extracellular signal-regulated kinase (ERK), significantly down-regulated lipopolysaccharide (LPS)-induced iNOS expression and promoter activity. Transactivation of LPS-stimulated NF-kappaB was inhibited by U0126. These results suggest that the transcription factor NF-kappaB is involved in ERK-mediated iNOS regulation and that activation of the Ras/ERK pathway contributes to the induction of iNOS expression in RAW264.7 cells in response to LPS. OC treatment inhibited the production of nitric oxide in a concentration-dependent manner and also blocked the LPS-induced expression of iNOS. These inhibitory effects were associated with reduced ERK1/2 activity. OC inhibited the phosphorylation of c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase. The findings herein show that the inhibition of LPS-induced ERK1/2 activation may be a contributing factor to the main mechanisms by which OC inhibits RAW264.7. To clarify the mechanistic basis for its ability to inhibit iNOS induction, we examined the effect of OC on the transactivation of the iNOS gene by luciferase reporter activity using the -1588 flanking region. OC potently suppressed reporter gene activity. We also report here, for the first time, that LPS-induced iNOS expression was abolished by OC in RAW264.7 cells through by blocking the inhibition of transcription factor NF-kappaB binding activities. These activities are associated with the down-regulation of inhibitor kappaB (IkappaB) kinase (IKK) activity by OC (6 microM), thus inhibiting LPS-induced phosphorylation as well as the degradation of IkappaBalpha. These findings suggest that the inhibition of LPS

  20. Phosphorylation of farnesoid X receptor by protein kinase C promotes its transcriptional activity.

    PubMed

    Gineste, Romain; Sirvent, Audrey; Paumelle, Réjane; Helleboid, Stéphane; Aquilina, Alexis; Darteil, Raphaël; Hum, Dean W; Fruchart, Jean-Charles; Staels, Bart

    2008-11-01

    The farnesoid X receptor (FXR, NR1H4) belongs to the nuclear receptor superfamily and is activated by bile acids such as chenodeoxycholic acid, or synthetic ligands such as GW4064. FXR is implicated in the regulation of bile acid, lipid, and carbohydrate metabolism. Posttranslational modifications regulating its activity have not been investigated yet. Here, we demonstrate that calcium-dependent protein kinase C (PKC) inhibition impairs ligand-mediated regulation of FXR target genes. Moreover, in a transactivation assay, we show that FXR transcriptional activity is modulated by PKC. Furthermore, phorbol 12-myristate 13-acetate , a PKC activator, induces the phosphorylation of endogenous FXR in HepG2 cells and PKCalpha phosphorylates in vitro FXR in its DNA-binding domain on S135 and S154. Mutation of S135 and S154 to alanine residues reduces in cell FXR phosphorylation. In contrast to wild-type FXR, mutant FXRS135AS154A displays an impaired PKCalpha-induced transactivation and a decreased ligand-dependent FXR transactivation. Finally, phosphorylation of FXR by PKC promotes the recruitment of peroxisomal proliferator-activated receptor gamma coactivator 1alpha. In conclusion, these findings show that the phosphorylation of FXR induced by PKCalpha directly modulates the ability of agonists to activate FXR.

  1. PPARα blocks glucocorticoid receptor α-mediated transactivation but cooperates with the activated glucocorticoid receptor α for transrepression on NF-κB

    PubMed Central

    Bougarne, Nadia; Paumelle, Réjane; Caron, Sandrine; Hennuyer, Nathalie; Mansouri, Roxane; Gervois, Philippe; Staels, Bart; Haegeman, Guy; De Bosscher, Karolien

    2009-01-01

    Glucocorticoid receptor α (GRα) and peroxisome proliferator-activated receptor α (PPARα) are transcription factors with clinically important immune-modulating properties. Either receptor can inhibit cytokine gene expression, mainly through interference with nuclear factor κB (NF-κB)-driven gene expression. The present work aimed to investigate a functional cross-talk between PPARα- and GRα-mediated signaling pathways. Simultaneous activation of PPARα and GRα dose-dependently enhances transrepression of NF-κB-driven gene expression and additively represses cytokine production. In sharp contrast and quite unexpectedly, PPARα agonists inhibit the expression of classical glucocorticoid response element (GRE)-driven genes in a PPARα-dependent manner, as demonstrated by experiments using PPARα wild-type and knockout mice. The underlying mechanism for this transcriptional antagonism relies on a PPARα-mediated interference with the recruitment of GRα, and concomitantly of RNA polymerase II, to GRE-driven gene promoters. Finally, the biological relevance of this phenomenon is underscored by the observation that treatment with the PPARα agonist fenofibrate prevents glucocorticoid-induced hyperinsulinemia of mice fed a high-fat diet. Taken together, PPARα negatively interferes with GRE-mediated GRα activity while potentiating its antiinflammatory effects, thus providing a rationale for combination therapy in chronic inflammatory disorders. PMID:19376972

  2. Transactivation of lifeguard (LFG) by Akt-/LEF-1 pathway in MCF-7 and MDA-MB 231 human breast cancer cells.

    PubMed

    Bucan, Vesna; Adili, Mehran Y; Choi, Claudia Y U; Eddy, Mau-Thek; Vogt, Peter M; Reimers, Kerstin

    2010-07-01

    Lifeguard (LFG) has been identified as a molecule that uniquely inhibits death mediated by Fas. The molecular function of human LFG and its regulation in carcinogenesis is uncertain. In our study, we investigated the potential regulation of LFG expression by Akt/LEF-1 pathway. The Glycogen synthase kinase-3 (GSK3) can be regulated by different signaling pathways including those mediated by protein kinase Akt. Inhibition of GSK3beta subunits activity results in the stabilisation of the beta-catenin protein and its accumulation in the nucleus, where it associates with members of the TCF/LEF-1 family of transcription factors to mediate gene transcription. In Western blots, RT-PCR and by small interfering RNA directed against LEF-1, we demonstrated that LFG expression correlates with GSK3beta and LEF-1 activation. Moreover, we showed that LFG mRNA was down-regulated after transfection with siRNA against LEF-1 in MDA-MB-231 cells. Our results therefore identify LFG as a target of the Akt/LEF-1 pathway in MDA-MB-231 breast tumour cells, a regulation which could play a key role in breast tumour progression.

  3. Substrate inhibition of transketolase.

    PubMed

    Solovjeva, Olga N; Kovina, Marina V; Kochetov, German A

    2016-03-01

    We studied the influence of the acceptor substrate of transketolase on the activity of the enzyme in the presence of reductants. Ribose-5-phosphate in the presence of cyanoborohydride decreased the transketolase catalytic activity. The inhibition is caused by the loss of catalytic function of the coenzyme-thiamine diphosphate. Similar inhibitory effect was observed in the presence of NADPH. This could indicate its possible regulatory role not only towards transketolase, but also towards the pentose phosphate pathway of carbohydrate metabolism overall, taking into account the fact that it inhibits not only transketolase but also another enzyme of the pentose phosphate pathway--glucose 6-phosphate dehydrogenase [Eggleston L.V., Krebs H.A. Regulation of the pentose phosphate cycle, Biochem. J. 138 (1974) 425-435]. PMID:26708478

  4. FELINE TRITRICHOMONAS FOETUS ADHERE TO INTESTINAL EPITHELIUM BY RECEPTOR-LIGAND-DEPENDENT MECHANISMS

    PubMed Central

    Tolbert, M.K.; Stauffer, S.H.; Gookin, J.L.

    2013-01-01

    Tritrichomonas foetus (TF) is a protozoan that infects the feline ileum and colon resulting in chronic diarrhea. Up to 30% of young purebred cats are infected with TF and the infection is recognized as pandemic. Only a single drug, characterized by a narrow margin of safety and emerging development of resistance, is effective for treatment. While the venereal pathogenicity of bovine TF is attributed to adherence to uterovaginal epithelium, the pathogenesis of diarrhea in feline TF infection is unknown. The aim of this study was to establish an in vitro model of feline TF adhesion to intestinal epithelium. Confluent monolayers of porcine intestinal epithelial cells (IPEC-J2) were infected with axenic cultures of feline TF that were labeled with [3H] thymidine or CFSE and harvested at log-phase. The effect of multiplicity and duration of infection, viability of TF, binding competition, formalin fixation and cytoskeletal inhibitors on adherence of feline TF to IPEC-J2 monolayers was quantified by liquid scintillation counting and immunofluorescence. [3H] thymidine and CFSE-labeled TF reproducibly adhered to IPEC-J2 monolayers. Clinical isolates of feline TF adhered to the intestinal epithelium in significantly greater numbers than Pentatrichomonas hominis, the latter of which is a presumably nonpathogenic trichomonad. Adhesion of TF required viable trophozoites but was independent of cytoskeletal activity. Based on saturation and competition binding experiments, adherence of feline TF to the epithelium occurred via specific receptor-ligand interactions. The developed model provides a valuable resource for assessing pathogenic mechanisms of feline TF and developing novel pharmacologic therapies for blocking the adhesion of feline TF to the intestinal epithelium. PMID:23182300

  5. Ligand-dependent dynamics of the active-site lid in bacterial dimethylarginine dimethylaminohydrolase.

    PubMed

    Rasheed, Masooma; Richter, Christine; Chisty, Liisa T; Kirkpatrick, John; Blackledge, Martin; Webb, Martin R; Driscoll, Paul C

    2014-02-18

    The dimethylarginine dimethylaminohydrolase (DDAH) enzyme family has been the subject of substantial investigation as a potential therapeutic target for the regulation of vascular tension. DDAH enzymes catalyze the conversion of asymmetric N(η),N(η)-dimethylarginine (ADMA) to l-citrulline. Here the influence of substrate and product binding on the dynamic flexibility of DDAH from Pseudomonas aeruginosa (PaDDAH) has been assessed. A combination of heteronuclear NMR spectroscopy, static and time-resolved fluorescence measurements, and atomistic molecular dynamics simulations was employed. A monodisperse monomeric variant of the wild-type enzyme binds the reaction product l-citrulline with a low millimolar dissociation constant. A second variant, engineered to be catalytically inactive by substitution of the nucleophilic Cys249 residue with serine, can still convert the substrate ADMA to products very slowly. This PaDDAH variant also binds l-citrulline, but with a low micromolar dissociation constant. NMR and molecular dynamics simulations indicate that the active site "lid", formed by residues Gly17-Asp27, exhibits a high degree of internal motion on the picosecond-to-nanosecond time scale. This suggests that the lid is open in the apo state and allows substrate access to the active site that is otherwise buried. l-Citrulline binding to both protein variants is accompanied by an ordering of the lid. Modification of PaDDAH with a coumarin fluorescence reporter allowed measurement of the kinetic mechanism of the PaDDAH reaction. A combination of NMR and kinetic data shows that the catalytic turnover of the enzyme is not limited by release of the l-citrulline product. The potential to develop the coumarin-PaDDAH adduct as an l-citrulline sensor is discussed. PMID:24484052

  6. Igf2 ligand dependency of Pten(+/-) developmental and tumour phenotypes in the mouse.

    PubMed

    Church, D N; Phillips, B R; Stuckey, D J; Barnes, D J; Buffa, F M; Manek, S; Clarke, K; Harris, A L; Carter, E J; Hassan, A B

    2012-08-01

    The tumour suppressor PTEN is a key negative regulator of the PI3K-Akt pathway, and is frequently either reduced or lost in human tumours. Murine genetic studies have confirmed that reduction of Pten promotes tumourigenesis in multiple organs, and demonstrated dependency of tumour development on the activation of downstream components such as Akt. Insulin-like growth factors (IGFs) act via IGF1R to activate the PI3K-Akt pathway, and are commonly upregulated in cancer. A context-dependent interplay between IGFs and PTEN exists in normal tissue and tumours; increased IGF2 ligand supply induces Pten expression creating an autoregulatory negative feedback loop, whereas complete loss of PTEN may either cooperate with IGF overexpression in tumour promotion, or result in desensitisation to IGF ligand. However, it remains unknown whether neoplasia associated with Pten loss is dependent on upstream IGF ligand supply in vivo. We evaluated this by generation of Pten(+/-) mice with differing allelic dosage of Igf2, an imprinted gene encoding the potent embryonic and tumour growth factor Igf2. We show that biallelic Igf2 supply potentiates a previously unreported Pten(+/-) placental phenotype and results in strain-dependent cardiac hyperplasia and neonatal lethality. Importantly, we also show that the effects of Pten loss in vivo are modified by Igf2 supply, as lack of Igf2 results in extended survival and delayed tumour development while biallelic supply is associated with reduced lifespan and accelerated neoplasia in females. Furthermore, we demonstrate that reduction of PTEN protein to heterozygote levels in human MCF7 cells is associated with increased proliferation in response to IGF2, and does not result in desensitisation to IGF2 signalling. These data indicate that the effects of Pten loss at heterozygote levels commonly observed in human tumours are modified by Igf2 ligand, and emphasise the importance of the evaluation of upstream pathways in tumours with Pten loss. PMID:22120709

  7. Structural basis for ligand-dependent dimerization of phenylalanine hydroxylase regulatory domain

    PubMed Central

    Patel, Dipali; Kopec, Jolanta; Fitzpatrick, Fiona; McCorvie, Thomas J.; Yue, Wyatt W.

    2016-01-01

    The multi-domain enzyme phenylalanine hydroxylase (PAH) catalyzes the hydroxylation of dietary I-phenylalanine (Phe) to I-tyrosine. Inherited mutations that result in PAH enzyme deficiency are the genetic cause of the autosomal recessive disorder phenylketonuria. Phe is the substrate for the PAH active site, but also an allosteric ligand that increases enzyme activity. Phe has been proposed to bind, in addition to the catalytic domain, a site at the PAH N-terminal regulatory domain (PAH-RD), to activate the enzyme via an unclear mechanism. Here we report the crystal structure of human PAH-RD bound with Phe at 1.8 Å resolution, revealing a homodimer of ACT folds with Phe bound at the dimer interface. This work delivers the structural evidence to support previous solution studies that a binding site exists in the RD for Phe, and that Phe binding results in dimerization of PAH-RD. Consistent with our structural observation, a disease-associated PAH mutant impaired in Phe binding disrupts the monomer:dimer equilibrium of PAH-RD. Our data therefore support an emerging model of PAH allosteric regulation, whereby Phe binds to PAH-RD and mediates the dimerization of regulatory modules that would bring about conformational changes to activate the enzyme. PMID:27049649

  8. Dipyridylamide ligand dependent dimensionality in luminescent zinc 2,4-pyridinedicarboxylate coordination complexes

    NASA Astrophysics Data System (ADS)

    Wudkewych, Megan J.; LaDuca, Robert L.

    2016-09-01

    Zinc nitrate, 2,4-pyridinedicarboxylic acid (2,4-pdcH2), and a hydrogen-bonding capable dipyridylamide ligand were combined in aqueous solution and subjected to hydrothermal reaction conditions. Three new crystalline coordination complexes were generated; their dimensionality depends crucially on the dipyridylamide length and geometric disposition of the pyridyl nitrogen donors. The three new phases were structurally characterized via single-crystal X-ray diffraction. {[H23-pina][Zn(2,4-pdc)2(H2O)2]·H2O} (1, 3-pina = 3-pyridylisonicotinamide) is a salt with protonated dipyridylamide cations and coordination complex anions. {[Zn2(2,4-pdc)2(H2O)4(3-pna)]·3H2O}n (2, 3-pna = 3-pyridylnicotinamide) shows a system of two-fold interpenetrated ruffled (6,3) coordination polymer layers. {[Zn(2,4-pdc)(H2O)2(3-pmna)]n (3, 3-pmna = 3-pyridylmethylnicotinamide) manifests a simple 1D chain topology. Luminescence was observed for two of the zinc complexes; this behavior is attributed to π-π* or π-n molecular orbital transitions. Thermal decomposition properties of the new phases are also probed.

  9. Inhibition of cancer cell epithelial mesenchymal transition by normal fibroblasts via production of 5-methoxytryptophan

    PubMed Central

    Chiang, Li-Yi; Chen, Hua-Ling; Kuo, Cheng-Chin; Wu, Kenneth K.

    2016-01-01

    We reported previously that human fibroblasts release 5-methoxytryptophan (5-MTP) which inhibits cancer cell COX-2 overexpression and suppresses cancer cell migration and metastasis. To determine whether fibroblasts block cancer cell epithelial mesenchymal transition (EMT) via 5-MTP, we evaluated the effect of Hs68 fibroblasts (HsFb) on A549 cancer cell EMT in a two-chamber system. Co-incubation of A549 with HsFb prevented TGF-β1-induced reduction of E-cadherin and increase in Snail and N-cadherin. Transfection of HsFb with tryptophan hydroxylase-1 siRNA, which inhibited tryptophan hydroxylase-1 protein expression and 5-MTP release in HsFb abrogated the effect of HsFb on A549 EMT. Direct addition of pure 5-MTP to cultured A549 cells followed by TGF-β1 prevented TGF-β1-induced reduction of E-cadherin, and elevation of Snail, vimentin and matrix metalloproteinase 9. Administration of 5-MTP to a murine xenograft tumor model reduced vimentin protein expression in the tumor tissues compared to vehicle control which was correlated with reduction of metastasis in the 5-MTP treated mice. Our experimental data suggest that 5-MTP exerted its anti-EMT actions through inhibition of p38 MAPK activation, p65/p50 NF-κB nuclear translocation and transactivation without the involvement of COX-2 or p300 histone acetyltransferase. Our findings indicate that fibroblasts release a tryptophan metabolite, 5-MTP, to reduce cancer cell EMT, migration, invasion and metastasis. PMID:27145282

  10. PTEN mutation and epidermal growth factor receptor activation regulate vascular endothelial growth factor (VEGF) mRNA expression in human glioblastoma cells by transactivating the proximal VEGF promoter.

    PubMed

    Pore, Nabendu; Liu, Shuang; Haas-Kogan, Daphne A; O'Rourke, Donald M; Maity, Amit

    2003-01-01

    Our previous work showed that, compared with parental U87MG human glioblastoma cells, vascular endothelial growth factor (VEGF) mRNA levels are decreased in U87/T691, a derivative line in which epidermal growth factor receptor (EGFR) signaling is inhibited by introduction of a truncated p185(Neu) protein (A. Maity et al., Cancer Res., 60: 5879-5886, 2000). The effect of EGFR activation on VEGF was mediated at the level of transcription via a phosphatidylinositol 3'-kinase (PI3K)-dependent pathway. In the current study we investigated the effect of PTEN, a negative regulator of PI3K signaling commonly mutated in glioblastoma cells, on VEGF expression. Several glioblastoma cell lines containing mutant PTEN, including U87MG, U87/T691, and U251MG, were infected with adenovirus expressing wild-type PTEN. This led to a decrease in the levels of both VEGF mRNA and phosphorylated Akt, a marker for PI3K activation. Treatment of U87MG cells with LY294002, a PI3K inhibitor, or cotransfection with a vector expressing wild-type PTEN decreased VEGF promoter activity using reporters containing either 1.5 kb of the promoter or a fragment extending from -88 to +54 bp. Activity of the -88/+54 VEGF promoter was down-regulated by dominant negative Akt and up-regulated by constitutively active myristoylated Akt. Introduction of wild-type PTEN and pharmacological inhibition of EGFR decreased VEGF mRNA expression and VEGF promoter activity in U87MG cells to a greater extent that did either manipulation by itself. Therefore, in human glioblastoma cells, PTEN mutation can cooperate with EGFR activation to increase VEGF mRNA levels by transcriptionally up-regulating the proximal VEGF promoter via the PI3K/Akt pathway.

  11. Nuclear Factor Kappa B Activation and Peroxisome Proliferator-activated Receptor Transactivational Effects of Chemical Components of the Roots of Polygonum multiflorum

    PubMed Central

    Sun, Ya Nan; Li, Wei; Song, Seok Bean; Yan, Xi Tao; Yang, Seo Young; Kim, Young Ho

    2016-01-01

    Background: Polygonum multiflorum is well-known as “Heshouwu” in traditional Chinese herbal medicine. In Northeast Asia, it is often used as a tonic to prevent premature aging of the kidney and liver, tendons, and bones and strengthening of the lower back and knees. Objective: To research the anti-inflammatory activities of components from P. multiflorum. Materials and Methods: The compounds were isolated by a combination of silica gel and YMC R-18 column chromatography, and their structures were identified by analysis of spectroscopic data (1D, 2D-nuclear magnetic resonance, and mass spectrometry). The anti-inflammatory activities of the isolated compounds 1−15 were evaluated by luciferase reporter gene assays. Results: Fifteen compounds (1–15) were isolated from the roots of P. multiflorum. Compounds 1−5 and 14−15 significantly inhibited tumor necrosis factor-α-induced nuclear factor kappa B-luciferase activity, with IC50 values of 24.16-37.56 μM. Compounds 1−5 also greatly enhanced peroxisome proliferator-activated receptors transcriptional activity with EC50 values of 18.26−31.45 μM. Conclusion: The anthraquinone derivatives were the active components from the roots of P. multiflorum as an inhibitor on inflammation-related factors in human hepatoma cells. Therefore, we suggest that the roots of P. multiflorum can be used to treat natural inflammatory diseases. SUMMARY This study presented that fifteen compounds (1-15) isolated from the roots of Polygonum multiflrum exert signifiant anti inflmmatory effects by inhibiting TNF α induced NF κB activation and PPARs transcription. Abbreviation used: NF κB: Nuclear factor kappa B, PPARs: Peroxisome proliferator activated receptors, PPREs: Peroxisome proliferator response elements, TNF α: Tumor necrosis factor α, ESI-MS: Electrospray ionization mass spectrometry, HepG2: Human hepatoma cells PMID:27019559

  12. Chlorogenic acid inhibits hypoxia-induced pulmonary artery smooth muscle cells proliferation via c-Src and Shc/Grb2/ERK2 signaling pathway.

    PubMed

    Li, Qun-Yi; Zhu, Ying-Feng; Zhang, Meng; Chen, Li; Zhang, Zhen; Du, Yong-Li; Ren, Guo-Qiang; Tang, Jian-Min; Zhong, Ming-Kang; Shi, Xiao-Jin

    2015-03-15

    Chlorogenic acid (CGA), abundant in coffee and particular fruits, can modulate hypertension and vascular dysfunction. Hypoxia-induced pulmonary artery smooth muscle cells (PASMCs) proliferation has been tightly linked to vascular remodeling in pulmonary arterial hypertension (PAH). Thus, the present study was designed to investigate the effect of CGA on hypoxia-induced proliferation in cultured rat PASMCs. The data showed that CGA potently inhibited PASMCs proliferation and DNA synthesis induced by hypoxia. These inhibitory effects were associated with G1 cell cycle arrest and down-regulation of cell cycle proteins. Treatment with CGA reduced hypoxia-induced hypoxia inducible factor 1α (HIF-1α) expression and trans-activation. Furthermore, hypoxia-evoked c-Src phosphorylation was inhibited by CGA. In vitro ELISA-based tyrosine kinase assay indicated that CGA was a direct inhibitor of c-Src. Moreover, CGA attenuated physical co-association of c-Src/Shc/Grb2 and ERK2 phosphorylation in PASMCs. These results suggest that CGA inhibits hypoxia-induced proliferation in PASMCs via regulating c-Src-mediated signaling pathway. In vivo investigation showed that chronic CGA treatment inhibits monocrotaline-induced PAH in rats. These findings presented here highlight the possible therapeutic use of CGA in hypoxia-related PAH. PMID:25666384

  13. Profiles of antioxidant/electrophile response element (ARE/EpRE) nuclear protein binding and c-Ha-ras transactivation in vascular smooth muscle cells treated with oxidative metabolites of benzo[a]pyrene.

    PubMed

    Miller, K P; Chen, Y H; Hastings, V L; Bral, C M; Ramos, K S

    2000-11-01

    Activation of nuclear protein binding to the antioxidant/electrophile response element (ARE/EpRE) by benzo[a]pyrene (BaP) in vascular smooth muscle cells (vSMCs) is associated with transcriptional deregulation of c-Ha-ras. This response may be mediated by oxidative intermediates of BaP generated during the course of cellular metabolism. To test this hypothesis, the profile of ARE/EpRE protein binding and transactivation elicited by BaP was compared with that of 3-hydroxy BaP (3-OH BaP) (0.03 to 3.0 microM), BaP 7,8-dihydrodiol (BaP 7,8-diol) (0.03 to 3.0 microM), BaP 3,6-quinone (BaP 3,6-Q) (0.0003 to 3.0 microM), and H(2)O(2) (25 to 100 microM). Specific protein binding to the consensus c-Ha-ras ARE/EpRE was observed in vSMCs treated with all BaP metabolites at concentrations considerably lower than those required for the parent compound. H(2)O(2), a by-product of BaP 3,6-Q redox cycling, also increased binding to the ARE/EpRE. Treatment of vSMCs with oxidative BaP metabolites or H(2)O(2) transactivated the c-Ha-ras promoter in all instances, but the response was consistently half of the maximal induction elicited by BaP. Similar proteins cross-linked specifically to the consensus c-Ha-ras ARE/EpRE sequence in cells treated with BaP or its oxidative intermediates. The protein binding profile in the c-Ha-ras promoter was similar to that in the NADPH:quinone reductase gene (NQO(1)) and the glutathione S-transferase Ya gene (GSTYa) promoters, but the relative abundance of individual complexes was promoter-specific. We conclude that oxidative intermediates of BaP mediate activation of nuclear protein binding to ARE/EpRE and contribute to transcriptional de-regulation of c-Ha-ras in vSMCs.

  14. The equine herpesvirus-1 IR3 gene that lies antisense to the sole immediate-early (IE) gene is trans-activated by the IE protein, and is poorly expressed to a protein

    SciTech Connect

    Ahn, Byung Chul; Breitenbach, Jonathan E.; Kim, Seong K.; O'Callaghan, Dennis J. . E-mail: docall@lsuhsc.edu

    2007-06-20

    The unique IR3 gene of equine herpesvirus 1 (EHV-1) is expressed as a late 1.0-kb transcript. Previous studies confirmed the IR3 transcription initiation site and tentatively identified other cis-acting elements specific to IR3 such as a TATA box, a 443 base pair 5'untranslated region (UTR), a 285 base pair open reading frame (ORF), and a poly adenylation (A) signal [Holden, V.R., Harty, R.N., Yalamanchili, R.R., O'Callaghan, D.J., 1992. The IR3 gene of equine herpesvirus type 1: a unique gene regulated by sequences within the intron of the immediate-early gene. DNA Seq. 3, 143-152]. Transient transfection assays revealed that the IR3 promoter is strongly trans-activated by the IE protein (IEP) and that coexpression of the IEP with the early EICP0 and IR4 regulatory proteins results in maximal trans-activation of the IR3 promoter. Gel shift assays revealed that the IEP directly binds to the IR3 promoter region. Western blot analysis showed that the IR3 protein produced in E. coli was detected by antibodies to IR3 synthetic peptides; however, the IR3 protein was not detected in EHV-1 infected cell extracts by these same anti-IR3 antibodies, even though the IR3 transcript was detected by northern blot. These findings suggest that the IR3 may not be expressed to a protein. Expression of an IR3/GFP fusion gene was not observed, but expression of a GFP/IR3 fusion gene was detected by fluorescent microscopy. In further attempts to detect the IR3/GFP fusion protein using anti-GFP antibody, western blot analysis showed that the IR3/GFP fusion protein was not detected in vivo. Interestingly, a truncated form of the GFP/IR3 protein was synthesized from the GFP/IR3 fusion gene. However, GFP/IR3 and IR3/GFP fusion proteins of the predicted sizes were synthesized by in vitro coupled transcription and translation of the fusion genes, suggesting poor expression of the IR3 protein in vivo. The possible role of the IR3 transcript in EHV-1 infection is discussed.

  15. 2-Methoxyestradiol inhibits progesterone-dependent tissue factor expression and activity in breast cancer cells.

    PubMed

    Quezada, Marisol; Diaz, Jorge; Henriquez, Soledad; Bravo, Maria Loreto; Aranda, Evelyn; Oliva, Barbara; Villalon, Manuel; Kato, Sumie; Cuello, Mauricio A; Brosens, Jan J; Lange, Carol A; Owen, Gareth I

    2010-06-01

    2-Methoxyestradiol (2ME) is an endogenous metabolite of 17β-estradiol with antiangiogenic and antitumor properties, although its mechanisms of action remain unclear. Progestins in hormone replacement therapy increase the risk of breast cancer. Progesterone also enhances the procoagulant activity and invasive potential of progesterone receptor (PR)-positive breast cancer cell lines, an effect largely mediated by induction of tissue factor (TF), the cellular activator of the coagulation cascade. Here we show that 2ME abrogates the induction TF expression in progesterone-treated breast cancer cells via a mechanism that does not involve the estrogen receptor. Instead, we demonstrate that by selectively antagonizing ERK1/2 signaling in breast cancer cells, 2ME limits the transactivation potential of ligand-bound PR and inhibits the expression of endogenous progesterone targets, such as TF and signal transducer and activator of transcription 5. We further demonstrate that 2ME can alter the phosphorylation status of PR. Thus, 2ME prevents progesterone-dependent increase in breast cancer cell invasiveness and procoagulant activity by uncoupling PR from the ERK1/2 signal transduction pathway.

  16. Spi-B inhibits human plasma cell differentiation by repressing BLIMP1 and XBP-1 expression.

    PubMed

    Schmidlin, Heike; Diehl, Sean A; Nagasawa, Maho; Scheeren, Ferenc A; Schotte, Remko; Uittenbogaart, Christel H; Spits, Hergen; Blom, Bianca

    2008-09-01

    The terminal differentiation of B cells into antibody-secreting plasma cells is tightly regulated by a complex network of transcription factors. Here we evaluated the role of the Ets factor Spi-B during terminal differentiation of human B cells. All mature tonsil and peripheral blood B-cell subsets expressed Spi-B, with the exception of plasma cells. Overexpression of Spi-B in CD19(+) B cells inhibited, similar to the known inhibitor BCL-6, the expression of plasma cell-associated surface markers and transcription factors as well as immunoglobulin production, ie, in vitro plasma cell differentiation. The arrest in B-cell differentiation enforced by Spi-B was independent of the transactivation domain, but dependent on the Ets-domain. By chromatin immunoprecipitation and assays using an inducible Spi-B construct BLIMP1 and XBP-1 were identified as direct target genes of Spi-B mediated repression. We propose a novel role for Spi-B in maintenance of germinal center and memory B cells by direct repression of major plasma cell factors and thereby plasma cell differentiation.

  17. Multi-ligand poly(L-lactic-co-glycolic acid) nanoparticles inhibit activation of endothelial cells.

    PubMed

    Xu, Hao; Kona, Soujanya; Su, Lee-Chun; Tsai, Yi-Ting; Dong, Jing-Fei; Brilakis, Emmanouil S; Tang, Liping; Banerjee, Subhash; Nguyen, Kytai T

    2013-08-01

    Endothelial cell (EC) activation and inflammation is a key step in the initiation and progression of many cardiovascular diseases. Targeted delivery of therapeutic reagents to inflamed EC using nanoparticles is challenging as nanoparticles do not arrest on EC efficiently under high shear stress. In this study, we developed a novel polymeric platelet-mimicking nanoparticle for strong particle adhesion onto ECs and enhanced particle internalization by ECs. This nanoparticle was encapsulated with dexamethasone as the anti-inflammatory drug, and conjugated with polyethylene glycol, glycoprotein 1b, and trans-activating transcriptional peptide. The multi-ligand nanoparticle showed significantly greater adhesion on P-selectin, von Willebrand Factor, than the unmodified particles, and activated EC in vitro under both static and flow conditions. Treatment of injured rat carotid arteries with these multi-ligand nanoparticles suppressed neointimal stenosis more than unconjugated nanoparticles did. These results indicate that this novel multi-ligand nanoparticle is efficient to target inflamed EC and inhibit inflammation and subsequent stenosis.

  18. Skp2 inhibits osteogenesis by promoting ubiquitin-proteasome degradation of Runx2.

    PubMed

    Thacker, Gatha; Kumar, Yogesh; Khan, Mohd Parvez; Shukla, Nidhi; Kapoor, Isha; Kanaujiya, Jitendra Kumar; Lochab, Savita; Ahmed, Shakil; Sanyal, Sabyasachi; Chattopadhyay, Naibedya; Trivedi, Arun Kumar

    2016-04-01

    Osteogenic transcription factor Runx2 is essential for osteoblast differentiation. The activity of Runx2 is tightly regulated at transcriptional as well as post-translational level. However, regulation of Runx2 stability by ubiquitin mediated proteasomal degradation by E3 ubiquitin ligases is little-known. Here, for the first time we demonstrate that Skp2, an SCF family E3 ubiquitin ligase negatively targets Runx2 by promoting its polyubiquitination and proteasome dependent degradation. Co-immunoprecipitation studies revealed that Skp2 physically interacts with Runx2 both in a heterologous as well as physiologically relevant system. Functional consequences of Runx2-Skp2 physical interaction were then assessed by promoter reporter assay. We show that Skp2-mediated downregulation of Runx2 led to reduced Runx2 transactivation and osteoblast differentiation. On the contrary, inhibition of Skp2 restored Runx2 levels and promoted osteoblast differentiation. We further show that Skp2 and Runx2 proteins are co-expressed and show inverse relation in vivo such as in lactating, ovariectomized and estrogen-treated ovariectomized animals. Together, these data demonstrate that Skp2 targets Runx2 for ubiquitin mediated degradation and hence negatively regulate osteogenesis. Therefore, the present study provides a plausible therapeutic target for osteoporosis or cleidocranial dysplasia caused by the heterozygous mutation of Runx2 gene. PMID:26778333

  19. Influenza A Virus NS1 Protein Inhibits the NLRP3 Inflammasome

    PubMed Central

    Cheong, Woo-Chang; Kang, Hye-Ri; Yoon, Hyunyee; Kang, Suk-Jo; Ting, Jenny P.-Y.; Song, Moon Jung

    2015-01-01

    The inflammasome is a molecular platform that stimulates the activation of caspase-1 and the processing of pro-interleukin (IL)-1β and pro-IL-18 for secretion. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) protein is activated by diverse molecules and pathogens, leading to the formation of the NLRP3 inflammasome. Recent studies showed that the NLRP3 inflammasome mediates innate immunity against influenza A virus (IAV) infection. In this study, we investigated the function of the IAV non-structural protein 1 (NS1) in the modulation of NLRP3 inflammasome. We found that NS1 proteins derived from both highly pathogenic and low pathogenic strains efficiently decreased secretion of IL-1β and IL-18 from THP-1 cells treated with LPS and ATP. NS1 overexpression significantly impaired the transcription of proinflammatory cytokines by inhibiting transactivation of the nuclear factor-κB (NF-κB), a major transcription activator. Furthermore, NS1 physically interacted with endogenous NLRP3 and activation of the NLRP3 inflammasome was abrogated in NS1-expressing THP-1 cells. These findings suggest that NS1 downregulates NLRP3 inflammasome activation by targeting NLRP3 as well as NF-κB, leading to a reduction in the levels of inflammatory cytokines as a viral immune evasion strategy. PMID:25978411

  20. Fisetin induces Sirt1 expression while inhibiting early adipogenesis in 3T3-L1 cells.

    PubMed

    Kim, Sang Chon; Kim, Yoo Hoon; Son, Sung Wook; Moon, Eun-Yi; Pyo, Suhkneung; Um, Sung Hee

    2015-11-27

    Fisetin (3,7,3',4'-tetrahydroxyflavone) is a naturally found flavonol in many fruits and vegetables and is known to have anti-aging, anti-cancer and anti-viral effects. However, the effects of fisetin on early adipocyte differentiation and the epigenetic regulator controlling adipogenic transcription factors remain unclear. Here, we show that fisetin inhibits lipid accumulation and suppresses the expression of PPARγ in 3T3-L1 cells. Fisetin suppressed early stages of preadipocyte differentiation, and induced expression of Sirt1. Depletion of Sirt1 abolished the inhibitory effects of fisetin on intracellular lipid accumulation and on PPARγ expression. Mechanistically, fisetin facilitated Sirt1-mediated deacetylation of PPARγ and FoxO1, and enhanced the association of Sirt1 with the PPARγ promoter, leading to suppression of PPARγ transcriptional activity, thereby repressing adipogenesis. Lowering Sirt1 levels reversed the effects of fisetin on deacetylation of PPARγ and increased PPARγ transactivation. Collectively, our results suggest the effects of fisetin in increasing Sirt1 expression and in epigenetic control of early adipogenesis.

  1. Beneficial bacteria inhibit cachexia

    PubMed Central

    Varian, Bernard J.; Goureshetti, Sravya; Poutahidis, Theofilos; Lakritz, Jessica R.; Levkovich, Tatiana; Kwok, Caitlin; Teliousis, Konstantinos; Ibrahim, Yassin M.; Mirabal, Sheyla; Erdman, Susan E.

    2016-01-01

    Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny. PMID:26933816

  2. Beneficial bacteria inhibit cachexia.

    PubMed

    Varian, Bernard J; Goureshetti, Sravya; Poutahidis, Theofilos; Lakritz, Jessica R; Levkovich, Tatiana; Kwok, Caitlin; Teliousis, Konstantinos; Ibrahim, Yassin M; Mirabal, Sheyla; Erdman, Susan E

    2016-03-15

    Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny. PMID:26933816

  3. Pharmacological Inhibition of FTO

    PubMed Central

    McMurray, Fiona; Demetriades, Marina; Aik, WeiShen; Merkestein, Myrte; Kramer, Holger; Andrew, Daniel S.; Scudamore, Cheryl L.; Hough, Tertius A.; Wells, Sara; Ashcroft, Frances M.; McDonough, Michael A.; Schofield, Christopher J.; Cox, Roger D.

    2015-01-01

    In 2007, a genome wide association study identified a SNP in intron one of the gene encoding human FTO that was associated with increased body mass index. Homozygous risk allele carriers are on average three kg heavier than those homozygous for the protective allele. FTO is a DNA/RNA demethylase, however, how this function affects body weight, if at all, is unknown. Here we aimed to pharmacologically inhibit FTO to examine the effect of its demethylase function in vitro and in vivo as a first step in evaluating the therapeutic potential of FTO. We showed that IOX3, a known inhibitor of the HIF prolyl hydroxylases, decreased protein expression of FTO (in C2C12 cells) and reduced maximal respiration rate in vitro. However, FTO protein levels were not significantly altered by treatment of mice with IOX3 at 60 mg/kg every two days. This treatment did not affect body weight, or RER, but did significantly reduce bone mineral density and content and alter adipose tissue distribution. Future compounds designed to selectively inhibit FTO’s demethylase activity could be therapeutically useful for the treatment of obesity. PMID:25830347

  4. Development and pre-validation of an in vitro transactivation assay for detection of (anti)androgenic potential compounds using 22Rv1/MMTV cells.

    PubMed

    Sun, Seunghan; Park, Eun-Jung; Choi, Yun-Ho; Lee, Hee-Seok; Ahn, Byung Yoon; Dong, Mi-Sook

    2016-04-01

    The endocrine-disrupting effects of androgenic signaling play crucial roles in several androgen-related diseases. In attempting to develop an in vitro cell line to be used in androgen receptor (AR)-mediated reporter gene assays, we developed a stable 22Rv1/MMTV cell line, which is a human prostate cancer cell line that endogenously expresses functional AR, to evaluate AR-mediated transcriptional activation (TA). Using 22Rv1/MMTV cells, we established and optimized a test protocol for the AR-TA assay and validated the proposed assay using 20 compounds recommended by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM). All the performance parameters for agonist and antagonist assays were 91-100% comparable between the 22Rv1/MMTV assay and the ICCVAM report. In conclusion, the AR-TA assay using 22Rv1/MMTV cells might be a quick and relatively inexpensive method for screening large numbers of chemicals for their potential to activate or inhibit AR-mediated gene transcription. PMID:26867867

  5. A plant alkaloid, veratridine, potentiates cancer chemosensitivity by UBXN2A-dependent inhibition of an oncoprotein, mortalin-2

    PubMed Central

    Abdullah, Ammara; Sane, Sanam; Branick, Kate A.; Freeling, Jessica L.; Wang, Hongmin; Zhang, Dong; Rezvani, Khosrow

    2015-01-01

    Veratridine (VTD), an alkaloid derived from the Liliaceae plant shows anti-tumor effects; however, its molecular targets have not been thoroughly studied. Using a high-throughput drug screen, we found that VTD enhances transactivation of UBXN2A, resulting in upregulation of UBXN2A in the cytoplasm, where UBXN2A binds and inhibits the oncoprotein mortalin-2 (mot-2). VTD-treated cancer cells undergo cell death in UBXN2A- and mot-2-dependent manners. The cytotoxic function of VTD is grade-dependent, and the combined treatment with a sub-optimal dose of the standard chemotherapy, 5-Fluorouracil (5-FU) and etoposide, demonstrated a synergistic effect, resulting in higher therapeutic efficacy. VTD influences the CD44+ stem cells, possibly through UBXN2A-dependent inhibition of mot-2. The VTD-dependent expression of UBXN2A is a potential candidate for designing novel strategies for colon cancer treatment because: 1) In 50% of colon cancer patients, UBXN2A protein levels in tumor tissues are significantly lower than those in the adjacent normal tissues. 2) Cytoplasmic expression of the mot-2 protein is very low in non-cancerous cells; thus, VTD can produce tumor-specific toxicity while normal cells remain intact. 3) Finally, VTD or its modified analogs offer a valuable adjuvant chemotherapy strategy to improve the efficacy of 5-FU-based chemotherapy for colon cancer patients harboring WT-p53. PMID:26188124

  6. ASPP2 controls epithelial plasticity and inhibits metastasis through β-catenin-dependent regulation of ZEB1.

    PubMed

    Wang, Yihua; Bu, Fangfang; Royer, Christophe; Serres, Sébastien; Larkin, James R; Soto, Manuel Sarmiento; Sibson, Nicola R; Salter, Victoria; Fritzsche, Florian; Turnquist, Casmir; Koch, Sofia; Zak, Jaroslav; Zhong, Shan; Wu, Guobin; Liang, Anmin; Olofsen, Patricia A; Moch, Holger; Hancock, David C; Downward, Julian; Goldin, Robert D; Zhao, Jian; Tong, Xin; Guo, Yajun; Lu, Xin

    2014-11-01

    Epithelial to mesenchymal transition (EMT), and the reverse mesenchymal to epithelial transition (MET), are known examples of epithelial plasticity that are important in kidney development and cancer metastasis. Here we identify ASPP2, a haploinsufficient tumour suppressor, p53 activator and PAR3 binding partner, as a molecular switch of MET and EMT. ASPP2 contributes to MET in mouse kidney in vivo. Mechanistically, ASPP2 induces MET through its PAR3-binding amino-terminus, independently of p53 binding. ASPP2 prevents β-catenin from transactivating ZEB1, directly by forming an ASPP2-β-catenin-E-cadherin ternary complex and indirectly by inhibiting β-catenin's N-terminal phosphorylation to stabilize the β-catenin-E-cadherin complex. ASPP2 limits the pro-invasive property of oncogenic RAS and inhibits tumour metastasis in vivo. Reduced ASPP2 expression results in EMT, and is associated with poor survival in hepatocellular carcinoma and breast cancer patients. Hence, ASPP2 is a key regulator of epithelial plasticity that connects cell polarity to the suppression of WNT signalling, EMT and tumour metastasis.

  7. Metformin inhibits hepatocellular glucose, lipid and cholesterol biosynthetic pathways by transcriptionally suppressing steroid receptor coactivator 2 (SRC-2)

    PubMed Central

    Madsen, Andre; Bozickovic, Olivera; Bjune, Jan-Inge; Mellgren, Gunnar; Sagen, Jørn V.

    2015-01-01

    The ability of the anti-diabetic drug metformin to inhibit anabolic processes including gluconeogenesis and lipogenesis is partly attributable to activation of the AMP-activated protein kinase (AMPK) pathway. The p160 steroid receptor coactivator 2 (SRC-2) is a key regulator of cellular metabolism and drives expression of the gluconeogenic enzyme glucose-6-phosphatase (G6Pc). Here, we uncovered a role for SRC-2 in the metabolic reprogramming imposed by metformin. In FaO cells, metformin dose-dependently reduced mRNA expression of SRC-2. Microarray analysis of metformin-treated cells revealed an overrepresentation of downregulated genes involved in biosynthesis of lipids and cholesterol. Several metformin-regulated genes including fatty acid synthase (FASN) were validated as transcriptional targets of SRC-2 with promoters characterized by sterol regulatory element (SRE) binding protein (SREBP) recognition sequences. Transactivation assays of the FASN promoter confirmed that SRC-2 is a coactivator of SREBP-1. By suppressing SRC-2 at the transcriptional level, metformin impeded recruitment of SRC-2 and RNA polymerase II to the G6Pc promoter and to SREs of mutual SRC-2/SREBP-1 target gene promoters. Hepatocellular fat accretion was reduced by metformin or knock-down of both SRC-2 and SREBP-1. Accordingly we propose that metformin inhibits glucose and lipid biosynthesis partly by downregulating SRC-2 gene expression. PMID:26548416

  8. Metformin inhibits hepatocellular glucose, lipid and cholesterol biosynthetic pathways by transcriptionally suppressing steroid receptor coactivator 2 (SRC-2).

    PubMed

    Madsen, Andre; Bozickovic, Olivera; Bjune, Jan-Inge; Mellgren, Gunnar; Sagen, Jørn V

    2015-01-01

    The ability of the anti-diabetic drug metformin to inhibit anabolic processes including gluconeogenesis and lipogenesis is partly attributable to activation of the AMP-activated protein kinase (AMPK) pathway. The p160 steroid receptor coactivator 2 (SRC-2) is a key regulator of cellular metabolism and drives expression of the gluconeogenic enzyme glucose-6-phosphatase (G6Pc). Here, we uncovered a role for SRC-2 in the metabolic reprogramming imposed by metformin. In FaO cells, metformin dose-dependently reduced mRNA expression of SRC-2. Microarray analysis of metformin-treated cells revealed an overrepresentation of downregulated genes involved in biosynthesis of lipids and cholesterol. Several metformin-regulated genes including fatty acid synthase (FASN) were validated as transcriptional targets of SRC-2 with promoters characterized by sterol regulatory element (SRE) binding protein (SREBP) recognition sequences. Transactivation assays of the FASN promoter confirmed that SRC-2 is a coactivator of SREBP-1. By suppressing SRC-2 at the transcriptional level, metformin impeded recruitment of SRC-2 and RNA polymerase II to the G6Pc promoter and to SREs of mutual SRC-2/SREBP-1 target gene promoters. Hepatocellular fat accretion was reduced by metformin or knock-down of both SRC-2 and SREBP-1. Accordingly we propose that metformin inhibits glucose and lipid biosynthesis partly by downregulating SRC-2 gene expression. PMID:26548416

  9. p53-dependent but ATM-independent inhibition of DNA synthesis and G2 arrest in cadmium-treated human fibroblasts

    SciTech Connect

    Cao Feng |; Zhou Tong; Simpson, Dennis; Zhou Yingchun; Boyer, Jayne; Chen Bo |; Jin Taiyi; Cordeiro-Stone, Marila; Kaufmann, William . E-mail: wkarlk@med.unc.edu

    2007-01-15

    This study focused on the activation of cell cycle checkpoint responses in diploid human fibroblasts that were treated with cadmium chloride and the potential roles of ATM and p53 signaling pathways in cadmium-induced responses. The alkaline comet assay indicated that cadmium caused a dose-dependent increase in DNA damage. Cells that were rendered p53-defective by expression of a dominant-negative p53 allele or knockdown of p53 mRNA were more resistant to cadmium-induced inactivation of colony formation than normal and ataxia telangiectasia (AT) cells. Synchronized fibroblasts in S were more sensitive to cadmium toxicity than cells in G1, suggesting that cadmium may target some element of DNA replication. Cadmium produced a dose- and time-dependent inhibition of DNA synthesis. An immediate inhibition was associated with severe delay in progression through S phase and a delayed inhibition seen 24 h after treatment was associated with accumulation of cells in G2. AT and normal cells displayed similar patterns of inhibition of DNA synthesis and G2 delay after treatment with cadmium, while p53-defective cells displayed significantly less of the delayed inhibition of DNA synthesis and accumulation in G2 post-treatment. Total p53 protein and ser15-phosphorylated p53 were induced by cadmium in normal and AT cells. The p53 transactivation target Gadd45{alpha} was induced in both p53-effective and p53-defective cells after 4 h cadmium treatment, and this was associated with an acute inhibition of mitosis. Cadmium produced a very unusual pattern of toxicity in human fibroblasts, inhibiting DNA replication and inducing p53-dependent growth arrest but without induction of p21{sup Cip1/Waf1} or activation of Chk1.

  10. Protein transduction domain of transactivating transcriptional activator fused to outer membrane protein K of Vibrio parahaemolyticus to vaccinate marbled eels (Anguilla marmorata) confers protection against mortality caused by V. parahaemolyticus

    PubMed Central

    Wang, Hang; Yang, Wei; Shen, Guoying; Zhang, Jianting; Lv, Wei; Ji, Binfeng; Meng, Chun

    2015-01-01

    Although immersion and oral vaccination are the most practical methods for fish farmers, their applications are very limited due to low immune stimulation effect. We used the protein transduction domain (PTD) of transactivating transcriptional factor (TAT) derived from HIV TAT protein to increase the delivery efficiency of aquatic protein vaccines. Vibrio parahaemolyticus outer membrane protein K (ompK), a reported vaccine candidate for the prevention of V. parahaemolyticus infection, was fused with TAT-PTD expressed in Escherichia coli. We found that PTD-ompK fusion protein effectively penetrated into marbled eel bodies. Analysis of ompK antibody titres demonstrated that immersion vaccination with PTD-ompK was superior to ompK alone and induced robust immune stimulation in marbled eels. Both active and passive protection analyses against immersive challenge with V. parahaemolyticus strains demonstrated that marbled eels immunized with PTD-ompK survived significantly longer than those immunized with ompK alone. Our results indicated that TAT-PTD could be served as is an efficient delivery system for aquatic immersion vaccinations against various infectious diseases commonly seen in aquatic farm industry. PMID:25919337

  11. Limitations of angiotensin inhibition.

    PubMed

    Nobakht, Niloofar; Kamgar, Mohammad; Rastogi, Anjay; Schrier, Robert W

    2011-06-01

    Angiotensin-converting-enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs) have beneficial effects in patients with cardiovascular disease and in those with diabetes-related and diabetes-independent chronic kidney diseases. These beneficial effects are independent of the antihypertensive properties of these drugs. However, ACE inhibitors, ARBs, and combinations of agents in these two classes are limited in the extent to which they inhibit the activity of the renin-angiotensin-aldosterone system (RAAS). Angiotensin breakthrough and aldosterone breakthrough may be important mechanisms involved in limiting the effects of ACE inhibitors and ARBs. Whether direct renin inhibitors will overcome some of the limitations of ACE-inhibitor and ARB therapy by blocking the deleterious effects of the RAAS remains to be proven. This important area is, however, in need of further investigation.

  12. Checkpoint inhibition in meningiomas.

    PubMed

    Bi, Wenya Linda; Wu, Winona W; Santagata, Sandro; Reardon, David A; Dunn, Ian F

    2016-06-01

    Meningiomas are increasingly appreciated to share similar features with other intra-axial central nervous system neoplasms as well as systemic cancers. Immune checkpoint inhibition has emerged as a promising therapy in a number of cancers, with durable responses of years in a subset of patients. Several lines of evidence support a role for immune-based therapeutic strategies in the management of meningiomas, especially high-grade subtypes. Meningiomas frequently originate juxtaposed to venous sinuses, where an anatomic conduit for lymphatic drainage resides. Multiple populations of immune cells have been observed in meningiomas. PD-1/PD-L1 mediated immunosuppression has been implicated in high-grade meningiomas, with association between PD-L1 expression with negative prognostic outcome. These data point to the promise of future combinatorial therapeutic strategies in meningioma. PMID:27197540

  13. Firefly luciferase inhibition.

    PubMed

    Leitão, João M M; Esteves da Silva, Joaquim C G

    2010-10-01

    Firefly luciferase (Luc) is the most studied of the luciferase enzymes and the mechanism and kinetics of the reactions catalyzed by this enzyme have been relatively well characterized. Luc catalyzes the bioluminescent reaction involving firefly luciferin (D-LH(2)), adenosine triphosphate (ATP), magnesium ion and molecular oxygen with the formation of an electronically excited species (oxyluciferin), inorganic pyrophosphate (PPi), carbon dioxide and adenosine monophosphate (AMP). Luc also catalyzes other non-luminescent reactions, which can interfere with the light production mechanism. Following electronic relaxation, the excited oxyluciferin emits radiation in the visible region of the electromagnetic spectrum (550-570 nm). Among the various possible compounds, several classes of inhibitory substances interfere with the activity of this enzyme: here, we consider substrate-related compounds, intermediates or products of the Luc catalyzed reactions, in addition to anesthetics and, fatty acids. This review summarizes the main inhibitors of Luc and the corresponding inhibition kinetic parameters.

  14. Curcumin inhibits srebp-2 expression in activated hepatic stellate cells in vitro by reducing the activity of specificity protein-1.

    PubMed

    Kang, Qiaohua; Chen, Anping

    2009-12-01

    Elevated levels of cholesterol/low-density lipoprotein (LDL) are a risk factor for the development of nonalcoholic steatohepatitis and its associated hepatic fibrosis. However, underlying mechanisms remain elusive. We previously reported that curcumin induced gene expression of peroxisome proliferator-activated receptor (PPAR)-gamma and stimulated its activity, leading to the inhibition of the activation of hepatic stellate cells (HSCs), the major effector cells during hepatic fibrogenesis. We recently showed that curcumin suppressed gene expression of LDL receptor in activated HSCs in vitro by repressing gene expression of the transcription factor sterol regulatory element binding protein-2 (SREBP-2), leading to the reduction in the level of intracellular cholesterol in HSCs and to the attenuation of the stimulatory effects of LDL on HSCs activation. The current study aimed at exploring molecular mechanisms by which curcumin inhibits srebp-2 expression in HSCs. Promoter deletion assays, mutagenesis assays, and EMSAs localize a specificity protein-1 (SP-1) binding GC-box in the srebp-2 promoter, which is responsible for enhancing the promoter activity and responding to curcumin in HSCs. Curcumin suppresses gene expression of SP-1 and reduces its trans-activation activity, which are mediated by the activation of PPARgamma. The inhibitory effect of curcumin on SP-1 binding to the GC-box is confirmed by chromatin immuno-precipitation. In summary, our results demonstrate that curcumin inhibits srebp-2 expression in cultured HSCs by activating PPARgamma and reducing the SP-1 activity, leading to the repression of ldlr expression. These results provide novel insights into molecular mechanisms by which curcumin inhibits LDL-induced HSC activation.

  15. Inhibition of human insulin gene transcription and MafA transcriptional activity by the dual leucine zipper kinase

    PubMed Central

    Stahnke, Marie-Jeannette; Dickel, Corinna; Schröder, Sabine; Kaiser, Diana; Blume, Roland; Stein, Roland; Pouponnot, Celio; Oetjen, Elke

    2016-01-01

    Insulin biosynthesis is an essential β-cell function and inappropriate insulin secretion and biosynthesis contribute to the pathogenesis of diabetes mellitus type 2. Previous studies showed that the dual leucine zipper kinase (DLK) induces β-cell apoptosis. Since β-cell dysfunction precedes β-cell loss, in the present study the effect of DLK on insulin gene transcription was investigated in the HIT-T15 β-cell line. Downregulation of endogenous DLK increased whereas overexpression of DLK decreased human insulin gene transcription. 5′- and 3′-deletion human insulin promoter analyses resulted in the identification of a DLK responsive element that mapped to the DNA binding-site for the β-cell specific transcription factor MafA. Overexpression of DLK wild-type but not its kinase-dead mutant inhibited MafA transcriptional activity conferred by its transactivation domain. Furthermore, in the non-β-cell line JEG DLK inhibited MafA overexpression-induced human insulin promoter activity. Overexpression of MafA and DLK or its kinase-dead mutant into JEG cells revealed that DLK but not its mutant reduced MafA protein content. Inhibition of the down-stream DLK kinase c-Jun N-terminal kinase (JNK) by SP600125 attenuated DLK-induced MafA loss. Furthermore, mutation of the serine 65 to alanine, shown to confer MafA protein stability, increased MafA-dependent insulin gene transcription and prevented DLK-induced MafA loss in JEG cells. These data suggest that DLK by activating JNK triggers the phosphorylation and degradation of MafA thereby attenuating insulin gene transcription. Given the importance of MafA for β-cell function, the inhibition of DLK might preserve β-cell function and ultimately retard the development of diabetes mellitus type 2. PMID:24726898

  16. The Unfolded Protein Response and the Phosphorylations of Activating Transcription Factor 2 in the trans-Activation of il23a Promoter Produced by β-Glucans*

    PubMed Central

    Rodríguez, Mario; Domingo, Esther; Alonso, Sara; Frade, Javier García; Eiros, José; Crespo, Mariano Sánchez; Fernández, Nieves

    2014-01-01

    Current views on the control of IL-23 production focus on the regulation of il23a, the gene encoding IL-23 p19, by NF-κB in combination with other transcription factors. C/EBP homologous protein (CHOP), X2-Box-binding protein 1 (XBP1), activator protein 1 (AP1), SMAD, CCAAT/enhancer-binding protein (C/EBPβ), and cAMP-response element-binding protein (CREB) have been involved in response to LPS, but no data are available regarding the mechanism triggered by the fungal mimic and β-glucan-containing stimulus zymosan, which produces IL-23 and to a low extent the related cytokine IL-12 p70. Zymosan induced the mobilization of CHOP from the nuclear fractions to phagocytic vesicles. Hypha-forming Candida also induced the nuclear disappearance of CHOP. Assay of transcription factor binding to the il23a promoter showed an increase of Thr(P)-71–Thr(P)-69-activating transcription factor 2 (ATF2) binding in response to zymosan. PKC and PKA/mitogen- and stress-activated kinase inhibitors down-regulated Thr(P)-71–ATF2 binding to the il23a promoter and il23a mRNA expression. Consistent with the current concept of complementary phosphorylations on N-terminal Thr-71 and Thr-69 of ATF2 by ERK and p38 MAPK, MEK, and p38 MAPK inhibitors blunted Thr(P)-69–ATF2 binding. Knockdown of atf2 mRNA with siRNA correlated with inhibition of il23a mRNA, but it did not affect the expression of il12/23b and il10 mRNA. These data indicate the following: (i) zymosan decreases nuclear proapoptotic CHOP, most likely by promoting its accumulation in phagocytic vesicles; (ii) zymosan-induced il23a mRNA expression is best explained through coordinated κB- and ATF2-dependent transcription; and (iii) il23a expression relies on complementary phosphorylation of ATF2 on Thr-69 and Thr-71 dependent on PKC and MAPK activities. PMID:24982422

  17. The aryl hydrocarbon receptor and estrogen receptor alpha differentially modulate nuclear factor erythroid-2-related factor 2 transactivation in MCF-7 breast cancer cells

    SciTech Connect

    Lo, Raymond; Matthews, Jason

    2013-07-15

    Nuclear factor erythroid-2-related factor 2 (NRF2; NFE2L2) plays an important role in mediating cellular protection against reactive oxygen species. NRF2 signaling is positively modulated by the aryl hydrocarbon receptor (AHR) but inhibited by estrogen receptor alpha (ERα). In this study we investigated the crosstalk among NRF2, AHR and ERα in MCF-7 breast cancer cells treated with the NRF2 activator sulforaphane (SFN), a dual AHR and ERα activator, 3,3′-diindolylmethane (DIM), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 17β-estradiol (E2). SFN-dependent increases in NADPH-dependent oxidoreductase 1 (NQO1) and heme oxygenase I (HMOX1) mRNA levels were significantly reduced after co-treatment with E2. E2-dependent repression of NQO1 and HMOX1 was associated with increased ERα but reduced p300 recruitment and reduced histone H3 acetylation at both genes. In contrast, DIM + SFN or TCDD + SFN induced NQO1 and HMOX1 mRNA expression to levels higher than SFN alone, which was prevented by RNAi-mediated knockdown of AHR. DIM + SFN but not TCDD + SFN also induced recruitment of ERα to NQO1 and HMOX1. However, the presence of AHR at NQO1 and HMOX1 restored p300 recruitment and histone H3 acetylation, thereby reversing the ERα-dependent repression of NRF2. Taken together, our study provides further evidence of functional interplay among NRF2, AHR and ERα signaling pathways through altered p300 recruitment to NRF2-regulated target genes. - Highlights: • We examined crosstalk among ERα, AHR, and NRF2 in MCF-7 breast cancer cells. • AHR enhanced the mRNA expression levels of two NRF2 target genes – HMOX1 and NQO1. • ERα repressed HMOX1 and NQO1 expression via decreased histone acetylation. • AHR prevented ERα-dependent repression of HMOX1 and NQO1.

  18. E-cadherin inhibits nuclear accumulation of Nrf2: implications for chemoresistance of cancer cells.

    PubMed

    Kim, Won Dong; Kim, Young Woo; Cho, Il Je; Lee, Chang Ho; Kim, Sang Geon

    2012-03-01

    Nrf2 has an anti-carcinogenic effect. However, an increase in Nrf2 activity is also implicated in cancer chemoresistance. A switch from E-cadherin to N-cadherin affects the transdifferentiation and metastasis of cancer cells. In view of the key role of this switch in cancer malignancy, we investigated the regulatory effect of E-cadherin on Nrf2. In HEK293 cells, overexpression of E-cadherin inhibited the nuclear accumulation of Nrf2, and prevented Nrf2-dependent gene induction. GST pull-down and immunocytochemical assays verified the interaction between E-cadherin and Nrf2: E-cadherin bound the C-terminus of Nrf2, but not its N-terminus, which comprises the Neh2 domain responsible for phosphorylation of Ser40. Our finding that the mutation of Ser40 to alanine in Nrf2 did not affect the ability of E-cadherin to bind Nrf2 and repress target gene transactivation suggests that E-cadherin might not disturb the phosphorylation. Studies using mutant constructs of E-cadherin suggested that the β-catenin-binding domain contributes to the inhibitory effect of E-cadherin on Nrf2. Consistently, knockdown of β-catenin attenuated not only the effect of E-cadherin binding to Nrf2, but also Keap1-dependent ubiquitylation of Nrf2, and thereby increased Nrf2 activity, supporting the involvement of β-catenin in the interactions. Collectively, E-cadherin recruits Nrf2 through β-catenin, and assists the function of Keap1 for the inhibition of nuclear localization and transcriptional activity of Nrf2. In HepG2 cells, the loss of E-cadherin by either siRNA knockdown or treatment with TGFβ1 enhanced the constitutive or inducible activity of Nrf2, implying that chemoresistance of cancer cells upon the loss of E-cadherin might be associated with Nrf2. PMID:22302998

  19. TDP-43 Inhibits NF-κB Activity by Blocking p65 Nuclear Translocation

    PubMed Central

    Zhu, Jingyan; Cynader, Max S.; Jia, William

    2015-01-01

    TDP-43 (TAR DNA binding protein 43) is a heterogeneous nuclear ribonucleoprotein (hnRNP) that has been found to play an important role in neurodegenerative diseases. TDP-43’s involvement in nuclear factor-kappaB pathways has been reported in both neurons and microglial cells. The NF-κB pathway targets hundreds of genes, many of which are involved in inflammation, immunity and cancer. p50/p65 (p50/RelA) heterodimers, as the major Rel complex in the NF-κB family, are induced by diverse external physiological stimuli and modulate transcriptional activity in almost all cell types. Both p65 and TDP-43 translocation occur through the classic nuclear transportation system. In this study, we report that TDP-43 overexpression prevents TNF-α induced p65 nuclear translocation in a dose dependent manner, and that this further inhibits p65 transactivation activity. The inhibition by TDP-43 does not occur through preventing IκB degradation but probably by competing for the nuclear transporter-importin α3 (KPNA4). This competition is dependent on the presence of the nuclear localization signal (NLS) in TDP-43. Silencing TDP-43 using a specific siRNA also increased p65 nuclear localization upon TNF-α stimulation, suggesting that endogenous TDP-43 may be a default suppressor of the NF-κB pathway. Our results indicate that TDP-43 may play an important role in regulating the levels of NF-κB activity by controlling the nuclear translocation of p65. PMID:26571498