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1

The Arabidopsis Basic\\/Helix-Loop-Helix Transcription Factor Family  

Microsoft Academic Search

The basic\\/helix-loop-helix (bHLH) proteins are a superfamily of transcription factors that bind as dimers to specific DNA tar- get sites and that have been well characterized in nonplant eukaryotes as important regulatory components in diverse bio- logical processes. Based on evidence that the bHLH protein PIF3 is a direct phytochrome reaction partner in the photore- ceptor's signaling network, we have

Gabriela Toledo-Ortiz; Enamul Huq; Peter H. Quail

2003-01-01

2

Various modes of basic helix-loop-helix protein-mediated regulation of murine leukemia virus transcription in lymphoid cell lines.  

PubMed Central

The transcriptionally regulatory regions of the lymphomagenic Akv and SL3-3 murine leukemia retroviruses (MLVs) contain two types of E-box consensus motifs, CAGATG. One type, EA/S, is located in the upstream promoter region, and the other, E(gre), is located in a tandem repeat with enhancer properties. We have examined the requirements of the individual E-boxes in MLV transcriptional regulation. In lymphoid cell lines only, the E(gre)-binding protein complexes included ALF1 or HEB and E2A basic helix-loop-helix proteins. Ectopic ALF1 and E2A proteins required intact E(gre) motifs for mediating transcriptional activation. ALF1 transactivated transcription of Akv MLV through the two E(gre) motifs equally, whereas E2A protein required the promoter-proximal E(gre) motif. In T- and B-cell lines, the E(gre) motifs were of major importance for Akv MLV transcriptional activity, while the EA/S motif had some effect. In contrast, neither E(gre) nor EA/S motifs contributed pronouncedly to Akv MLV transcription in NIH 3T3 cells lacking DNA-binding ALF1 or HEB and E2A proteins. The Id1 protein was found to repress ALF1 activity in vitro and in vivo. Moreover, ectopic Id1 repressed E(gre)-directed but not EA/S-directed MLV transcription in lymphoid cell lines. In conclusion, E(gre) motifs and interacting basic helix-loop-helix proteins are important determinants for MLV transcriptional activity in lymphocytic cell lines.

Nielsen, A L; N?rby, P L; Pedersen, F S; J?rgensen, P

1996-01-01

3

Target Specificities of Drosophila Enhancer of split Basic Helix-Loop-Helix Proteins  

PubMed Central

Seven Enhancer of split genes in Drosophila melanogaster encode basic-helix-loop-helix transcription factors which are components of the Notch signalling pathway. They are expressed in response to Notch activation and mediate some effects of the pathway by regulating the expression of target genes. Here we have determined that the optimal DNA binding site for the Enhancer of split proteins is a palindromic 12-bp sequence, 5?-TGGCACGTG(C/T)(C/T)A-3?, which contains an E-box core (CACGTG). This site is recognized by all of the individual Enhancer of split basic helix-loop-helix proteins, consistent with their ability to regulate similar target genes in vivo. We demonstrate that the 3 bp flanking the E-box core are intrinsic to DNA recognition by these proteins and that the Enhancer of split and proneural proteins can compete for binding on specific DNA sequences. Furthermore, the regulation conferred on a reporter gene in Drosophila by three closely related sequences demonstrates that even subtle sequence changes within an E box or flanking bases have dramatic consequences on the overall repertoire of proteins that can bind in vivo.

Jennings, Barbara H.; Tyler, David M.; Bray, Sarah J.

1999-01-01

4

The Basic Helix-Loop-Helix Transcription Factor Family in the Honey Bee, Apis mellifera  

PubMed Central

The basic helix-loop-helix (bHLH) transcription factors play important roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in a dozen of organisms including fruit fly, mouse and human. In this study, we identified 51 bHLH sequences in silico in the honey bee, Apis mellifera L. (Hymenoptera: Apidae), genome. Phylogenetic analyses revealed that they belong to 38 bHLH families with 21, 11, 9, 1, 8 and 1 members in high-order groups A, B, C, D, E and F, respectively. Using phylogenetic analyses, all of the 51 bHLH sequences were assigned to their corresponding families. Genes that encode ASCb, NeuroD, Oligo, Delilah, MyoRb, Figa and Mad were not found in the honey bee genome. The present study provides useful background information for future studies using the honey bee as a model system for insect development.

Wang, Yong; Chen, Keping; Yao, Qin; Wang, Wenbing; Zhu, Zhi

2008-01-01

5

The Basic Helix-Loop-Helix Transcription Factor PIF5 Acts on Ethylene Biosynthesis and Phytochrome Signaling by Distinct Mechanisms  

Technology Transfer Automated Retrieval System (TEKTRAN)

HYTOCHROME-INTERACTING FACTOR5 (PIF5), a basic helix-loop-helix transcription factor, interacts specifically with the photoactivated form of phytochrome B (phyB). Here, we report that dark-grown Arabidopsis thaliana seedlings overexpressing PIF5 (PIF5-OX) exhibit exaggerated apical hooks and short h...

6

A genome-wide survey on basic helix-loop-helix transcription factors in giant panda.  

PubMed

The giant panda (Ailuropoda melanoleuca) is a critically endangered mammalian species. Studies on functions of regulatory proteins involved in developmental processes would facilitate understanding of specific behavior in giant panda. The basic helix-loop-helix (bHLH) proteins play essential roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in over 20 organisms, including fruit fly, zebrafish, mouse and human. Our present study identified 107 bHLH family members being encoded in giant panda genome. Phylogenetic analyses revealed that they belong to 44 bHLH families with 46, 25, 15, 4, 11 and 3 members in group A, B, C, D, E and F, respectively, while the remaining 3 members were assigned into "orphan". Compared to mouse, the giant panda does not encode seven bHLH proteins namely Beta3a, Mesp2, Sclerax, S-Myc, Hes5 (or Hes6), EBF4 and Orphan 1. These results provide useful background information for future studies on structure and function of bHLH proteins in the regulation of giant panda development. PMID:22096504

Dang, Chunwang; Wang, Yong; Zhang, Debao; Yao, Qin; Chen, Keping

2011-11-09

7

A Genome-Wide Survey on Basic Helix-Loop-Helix Transcription Factors in Giant Panda  

PubMed Central

The giant panda (Ailuropoda melanoleuca) is a critically endangered mammalian species. Studies on functions of regulatory proteins involved in developmental processes would facilitate understanding of specific behavior in giant panda. The basic helix-loop-helix (bHLH) proteins play essential roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in over 20 organisms, including fruit fly, zebrafish, mouse and human. Our present study identified 107 bHLH family members being encoded in giant panda genome. Phylogenetic analyses revealed that they belong to 44 bHLH families with 46, 25, 15, 4, 11 and 3 members in group A, B, C, D, E and F, respectively, while the remaining 3 members were assigned into “orphan”. Compared to mouse, the giant panda does not encode seven bHLH proteins namely Beta3a, Mesp2, Sclerax, S-Myc, Hes5 (or Hes6), EBF4 and Orphan 1. These results provide useful background information for future studies on structure and function of bHLH proteins in the regulation of giant panda development.

Dang, Chunwang; Wang, Yong; Zhang, Debao; Yao, Qin; Chen, Keping

2011-01-01

8

Basic helix-loop-helix transcription factors and enteroendocrine cell differentiation.  

PubMed

For over 30 years it has been known that enteroendocrine cells derive from common precursor cells in the intestinal crypts. Until recently little was understood about the events that result in commitment to endocrine differentiation or the eventual segregation of over 10 different hormone-expressing cell types in the gastrointestinal tract. Enteroendocrine cells arise from pluripotent intestinal stem cells. Differentiation of enteroendocrine cells is controlled by the sequential expression of three basic helix-loop-helix transcription factors, Math1, Neurogenin 3 (Neurog3) and NeuroD. Math1 expression is required for specification and segregation of the intestinal secretory lineage (Paneth, goblet,and enteroendocrine cells) from the absorptive enterocyte lineage. Neurog3 expression represents the earliest stage of enteroendocrine differentiation and in its absence enteroendocrine cells fail to develop. Subsequent expression of NeuroD appears to represent a later stage of differentiation for maturing enteroendocrine cells. Enteroendocrine cell fate is inhibited by the Notch signalling pathway, which appears to inhibit both Math1 and Neurog3. Understanding enteroendocrine cell differentiation will become increasingly important for identifying potential future targets for common diseases such as diabetes and obesity. PMID:21824251

Li, H J; Ray, S K; Singh, N K; Johnston, B; Leiter, A B

2011-10-01

9

Basic helix-loop-helix transcription factors and regulation of alkaloid biosynthesis.  

PubMed

Transcription factors of the basic Helix-Loop-Helix (bHLH) family play a central role in cell proliferation, determination, and differentiation. In plants, the regulatory functions of bHLHs in phenylpropanoid biosynthesis have been well established with regard to other interacting-proteins; i.e., MYB and WD40 repeat proteins. On the other hand, those in alkaloid biosynthesis are greatly limited due to the limited distribution of alkaloids in plant species. Recently, several groups have reported the regulatory functions of bHLH in alkaloid biosynthesis: novel CjbHLH1 in isoquinoline alkaloid biosynthesis in Coptis japonica, and Jasmonate-inducible MYC2-type bHLHs in nicotine-alkaloid biosynthesis in Nicotiana plants and indole alkaloid biosynthesis in Catharanthus roseus. We report here the JA-inducibility of CjbHLH1 and discuss the similarity and differences of non-MYC2-resemblant CjbHLH1 and MYC2-type bHLHs in nicotine and indole alkaloid biosynthesis. PMID:22067108

Yamada, Yasuyuki; Koyama, Tomotsugu; Sato, Fumihiko

2011-11-01

10

Basic helix-loop-helix transcription factors and regulation of alkaloid biosynthesis  

PubMed Central

Transcription factors of the basic Helix-Loop-Helix (bHLH) family play a central role in cell proliferation, determination, and differentiation. In plants, the regulatory functions of bHLHs in phenylpropanoid biosynthesis have been well established with regard to other interacting-proteins; i.e., MYB and WD40 repeat proteins. On the other hand, those in alkaloid biosynthesis are greatly limited due to the limited distribution of alkaloids in plant species. Recently, several groups have reported the regulatory functions of bHLH in alkaloid biosynthesis: novel CjbHLH1 in isoquinoline alkaloid biosynthesis in Coptis japonica, and Jasmonate-inducible MYC2-type bHLHs in nicotine-alkaloid biosynthesis in Nicotiana plants and indole alkaloid biosynthesis in Catharanthus roseus. We report here the JA-inducibility of CjbHLH1 and discuss the similarity and differences of non-MYC2-resemblant CjbHLH1 and MYC2-type bHLHs in nicotine and indole alkaloid biosynthesis.

Yamada, Yasuyuki; Koyama, Tomotsugu; Sato, Fumihiko

2011-01-01

11

The Basic Helix-Loop-Helix Transcription Factor Family in the Pea Aphid, Acyrthosiphon pisum  

PubMed Central

The basic helix-loop-helix (bHLH) proteins play essential roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in over 20 organisms, including fruit fly, zebrafish, and human. This study identified 54 bHLH family members in the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), genome. Phylogenetic analyses revealed that they belong to 37 bHLH families with 21, 13, 9, 1, 9, and 1 members in group A, B, C, D, E, and F, respectively. Through in-group phylogenetic analyses, all of the identified A. pisum bHLH members were assigned into their correspondent bHLH families with confidence, among which 51 were defined according to phylogenetic analyses with orthologs from Drosophila melanogaster Meigen (Diptera: Drosophilidae), and 3 of them were defined according to phylogenetic analyses with orthologs from Bombyx mori L. (Lepidoptera: Bombycidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Analyses on genomic coding regions revealed that the number and average length of introns in A. pisum bHLH motifs are higher than those in other insects. The present study provides useful background information for future studies on structure and function of bHLH proteins in the regulation of A. pisum development.

Dang, Chun-Wang; Wang, Yong; Chen, Ke-Ping; Yao, Qing; Zhang, De-Bao; Guo, Min

2011-01-01

12

The basic helix-loop-helix transcription factor Hand1 regulates mouse development as a homodimer.  

PubMed

Hand1 is a basic helix-loop-helix transcription factor that is essential for development of the placenta, yolk sac and heart during mouse development. While Hand1 is essential for trophoblast giant cell (TGC) differentiation, its potential heterodimer partners are not co-expressed in TGCs. To test the hypothesis that Hand1 functions as homodimer, we generated knock-in mice in which the Hand1 gene was altered to encode a tethered homodimer (TH). Some Hand1(TH/-) conceptuses in which the only form of Hand1 is Hand1(TH) are viable and fertile, indicating that homodimer Hand1 is sufficient for mouse survival. ~2/3 of Hand1(TH/-) and all Hand1(TH/TH) mice died in utero and displayed severe placental defects and variable cardial and cranial-facial abnormalities, indicating a dosage-dependent effect of Hand1(TH). Meanwhile, expression of the Hand1(TH) protein did not have negative effects on viability or fertility in all Hand1(TH/+) mice. These data imply that Hand1 homodimer plays a dominant role during development and its expression dosage is critical for survival, whereas Hand1 heterodimers can be either dispensable or play a regulatory role to modulate the activity of Hand1 homodimer in vivo. PMID:23911935

Hu, Dong; Scott, Ian C; Snider, Fran; Geary-Joo, Colleen; Zhao, Xiang; Simmons, David G; Cross, James C

2013-08-01

13

A Triantagonistic Basic Helix-Loop-Helix System Regulates Cell Elongation in Arabidopsis[W][OA  

PubMed Central

In plants, basic helix-loop-helix (bHLH) transcription factors play important roles in the control of cell elongation. Two bHLH proteins, PACLOBTRAZOL RESISTANCE1 (PRE1) and Arabidopsis ILI1 binding bHLH1 (IBH1), antagonistically regulate cell elongation in response to brassinosteroid and gibberellin signaling, but the detailed molecular mechanisms by which these factors regulate cell elongation remain unclear. Here, we identify the bHLH transcriptional activators for cell elongation (ACEs) and demonstrate that PRE1, IBH1, and the ACEs constitute a triantagonistic bHLH system that competitively regulates cell elongation. In this system, the ACE bHLH transcription factors directly activate the expression of enzyme genes for cell elongation by interacting with their promoter regions. IBH1 negatively regulates cell elongation by interacting with the ACEs and thus interfering with their DNA binding. PRE1 interacts with IBH1 and counteracts the ability of IBH1 to affect ACEs. Therefore, PRE1 restores the transcriptional activity of ACEs, resulting in induction of cell elongation. The balance of triantagonistic bHLH proteins, ACEs, IBH1, and PRE1, might be important for determination of the size of plant cells. The expression of IBH1 and PRE1 is regulated by brassinosteroid, gibberellins, and developmental phase dependent factors, indicating that two phytohormones and phase-dependent signals are integrated by this triantagonistic bHLH system.

Ikeda, Miho; Fujiwara, Sumire; Mitsuda, Nobutaka; Ohme-Takagi, Masaru

2012-01-01

14

Differentiation of Arabidopsis guard cells: analysis of the networks incorporating the basic helix-loop-helix transcription factor, FAMA.  

PubMed

Nearly all extant land plants possess stomata, the epidermal structures that mediate gas exchange between the plant and the environment. The developmental pathways, cell division patterns, and molecules employed in the generation of these structures are simple examples of processes used in many developmental contexts. One specific module is a set of "master regulator" basic helix-loop-helix transcription factors that regulate individual consecutive steps in stomatal development. Here, we profile transcriptional changes in response to inducible expression of Arabidopsis (Arabidopsis thaliana) FAMA, a basic helix-loop-helix protein whose actions during the final stage in stomatal development regulate both cell division and cell fate. Genes identified by microarray and candidate approaches were then further analyzed to test specific hypothesis about the activity of FAMA, the shape of its regulatory network, and to create a new set of stomata-specific or stomata-enriched reporters. PMID:21245191

Hachez, Charles; Ohashi-Ito, Kyoko; Dong, Juan; Bergmann, Dominique C

2011-01-18

15

Id2 Promotes Apoptosis by a Novel Mechanism Independent of Dimerization to Basic Helix-Loop-Helix Factors  

Microsoft Academic Search

Members of the helix-loop-helix (HLH) family of Id proteins have demonstrated roles in the regulation of differentiation and cell proliferation. Id proteins inhibit differentiation by HLH-mediated heterodimerization with basic HLH transcription factors. This blocks their sequence-specific binding to DNA and activation of target genes that are often expressed in a tissue-specific manner. Id proteins can also act as positive regulators

MONICA FLORIO; MARIA-CLEMENCIA HERNANDEZ; HUI YANG; HUI-KUO SHU; JOHN L. CLEVELAND; MARK A. ISRAEL

1998-01-01

16

Nhlh1 , a basic helix-loop-helix transcription factor, is very tightly linked to the mouse looptail ( Lp ) mutation  

Microsoft Academic Search

Looptail (Lp) is a mutation on the distal portion of mouse Chromosome (Chr) 1 that affects neurulation in mouse and is phenotypically expressed by appearance of an open neural tube along the entire antero-posterior axis of the embryo (craniorachischisis). Nhlh1, a member of the basic helix-loop-helix family of transcription factors, is expressed in the developing neural tube in structures affected

A. Mullick; N. Groulx; D. Trasler; P. Gros

1995-01-01

17

Conversion of Xenopus Ectoderm into Neurons by NeuroD, a Basic Helix-Loop- Helix Protein  

Microsoft Academic Search

Basic helix-loop-helix (bHLH) proteins are instrumental in determining cell type during development. A bHLH protein, termed NeuroD, for neurogenic differentiation, has now been identified as a differentiation factor for neurogenesis because (i) it is expressed transiently in a subset of neurons in the central and peripheral nervous systems at the time of their terminal differentiation into mature neurons and (ii)

Jacqueline E. Lee; Stanley M. Hollenberg; Lauren Snider; David L. Turner; Naomi Lipnick; Harold Weintraub

1995-01-01

18

Oxidative stress drives disulfide bond formation between basic helix-loop-helix transcription factors.  

PubMed

Basic helix-loop-helix (bHLH) transcription factors including Twist1 and E2a proteins regulate essential processes. These factors bind DNA as homo- or heterodimers and the choice of binding partners determines their functional output. To investigate potential regulators of bHLH dimerization, cells were exposed to the oxidative agent hydrogen peroxide (H(2)O(2)). Western blot analysis in the presence or absence of reducing agents, revealed that H(2)O(2) induces the rapid formation of an intermolecular disulfide bond between Twist1 homodimers and Twist/E2a proteins heterodimers. The disulfide bond is first observed between Twist1 homodimers at 25 mM H(2)O(2) and between Twist1 heterodimers at 75 mM H(2)O(2). This response is dependent upon cell density as H(2)O(2) did not induce disulfide bridge formation between bHLH proteins in cells seeded at high density. In the presence of E proteins, the formation of Twist1/E2a proteins heterodimers is favored over Twist1 homodimers, identifying an oxidative stimulus as an important factor in modulating binding partner specificity. We further demonstrated that a cysteine residue located at the C-terminus of Twist1 and E2a proteins is involved in this response. Disulfide bond formation between Twist1 homodimers significantly reduced its ability to interact with two of its binding partners, Runx2 and HDAC4, indicating that disulfide dimerization in response to H(2)O(2) has functional significance. These data support the conclusion that disulfide bond formation in response to an oxidative stimulus contributes to Twist1 homo- and heterodimerization and raises the possibility that the redox status of a cell may represent an important step in bHLH transcriptional regulation. PMID:19950203

Danciu, Theodora E; Whitman, Malcolm

2010-02-01

19

The HAND1 Basic Helix-Loop-Helix Transcription Factor Regulates Trophoblast Differentiation via Multiple Mechanisms  

PubMed Central

The basic helix-loop-helix (bHLH) transcription factor genes Hand1 and Mash2 are essential for placental development in mice. Hand1 promotes differentiation of trophoblast giant cells, whereas Mash2 is required for the maintenance of giant cell precursors, and its overexpression prevents giant cell differentiation. We found that Hand1 expression and Mash2 expression overlap in the ectoplacental cone and spongiotrophoblast, layers of the placenta that contain the giant cell precursors, indicating that the antagonistic activities of Hand1 and Mash2 must be coordinated. MASH2 and HAND1 both heterodimerize with E factors, bHLH proteins that are the DNA-binding partners for most class B bHLH factors and which are also expressed in the ectoplacental cone and spongiotrophoblast. In vitro, HAND1 could antagonize MASH2 function by competing for E-factor binding. However, the Hand1 mutant phenotype cannot be solely explained by ectopic activity of MASH2, as the Hand1 mutant phenotype was not altered by further mutation of Mash2. Interestingly, expression of E-factor genes (ITF2 and ALF1) was down-regulated in the trophoblast lineage prior to giant cell differentiation. Therefore, suppression of MASH2 function, required to allow giant cell differentiation, may occur in vivo by loss of its E-factor partner due to loss of its expression and/or competition from HAND1. In giant cells, where E-factor expression was not detected, HAND1 presumably associates with a different bHLH partner. This may account for the distinct functions of HAND1 in giant cells and their precursors. We conclude that development of the trophoblast lineage is regulated by the interacting functions of HAND1, MASH2, and their cofactors.

Scott, Ian C.; Anson-Cartwright, Lynn; Riley, Paul; Reda, Danny; Cross, James C.

2000-01-01

20

The HAND1 basic helix-loop-helix transcription factor regulates trophoblast differentiation via multiple mechanisms.  

PubMed

The basic helix-loop-helix (bHLH) transcription factor genes Hand1 and Mash2 are essential for placental development in mice. Hand1 promotes differentiation of trophoblast giant cells, whereas Mash2 is required for the maintenance of giant cell precursors, and its overexpression prevents giant cell differentiation. We found that Hand1 expression and Mash2 expression overlap in the ectoplacental cone and spongiotrophoblast, layers of the placenta that contain the giant cell precursors, indicating that the antagonistic activities of Hand1 and Mash2 must be coordinated. MASH2 and HAND1 both heterodimerize with E factors, bHLH proteins that are the DNA-binding partners for most class B bHLH factors and which are also expressed in the ectoplacental cone and spongiotrophoblast. In vitro, HAND1 could antagonize MASH2 function by competing for E-factor binding. However, the Hand1 mutant phenotype cannot be solely explained by ectopic activity of MASH2, as the Hand1 mutant phenotype was not altered by further mutation of Mash2. Interestingly, expression of E-factor genes (ITF2 and ALF1) was down-regulated in the trophoblast lineage prior to giant cell differentiation. Therefore, suppression of MASH2 function, required to allow giant cell differentiation, may occur in vivo by loss of its E-factor partner due to loss of its expression and/or competition from HAND1. In giant cells, where E-factor expression was not detected, HAND1 presumably associates with a different bHLH partner. This may account for the distinct functions of HAND1 in giant cells and their precursors. We conclude that development of the trophoblast lineage is regulated by the interacting functions of HAND1, MASH2, and their cofactors. PMID:10611232

Scott, I C; Anson-Cartwright, L; Riley, P; Reda, D; Cross, J C

2000-01-01

21

The PAX6 gene is activated by the basic helix-loop-helix transcription factor NeuroD/BETA2.  

PubMed Central

PAX6 is a transcription factor that plays an important role during pancreatic morphogenesis. The aim of the present study is to identify the upstream activator(s) of the PAX6 gene possibly involved in the early stages of pancreatic differentiation. Recently, individual elements regulating PAX6 gene activity in the pancreas have been identified in a 1100 bp Spe / Hin cII fragment 4.6 kb upstream of exon 0. Preliminary sequence analysis of this region revealed some potential DNA-binding sites (E boxes) specific for the binding of basic helix-loop-helix transcription factors. By using electrophoretic mobility shift assays, we demonstrated that both nuclear protein extracts from insulin-secreting RINm5F cells and in vitro -translated NeuroD/BETA2 can bind specifically to these E boxes. Furthermore, by transient transfection experiments we demonstrated that the expression of basic helix-loop-helix transcription factor NeuroD/BETA2 can induce activation of the PAX6 promoter in the NIH-3T3 cell line. Thus we show that NeuroD/BETA2 is involved in the activation of the expression of PAX6 through E boxes in the PAX6 promoter localized in a 1.1 kb sequence within the 4.6 kb untranslated region upstream of exon 0.

Marsich, Eleonora; Vetere, Amedeo; Di Piazza, Matteo; Tell, Gianluca; Paoletti, Sergio

2003-01-01

22

Requirement for the basic helix-loop-helix transcription factor Dec2 in initial TH2 lineage commitment  

PubMed Central

How naïve CD4+ T cells commit to the T helper type 2 (TH2) lineage is poorly understood. Here we show that the basic helix-loop-helix transcription factor Dec2 is selectively expressed in TH2 cells. CD4+ T cells from Dec2-deficient mice exhibits defective TH2 differentiation in vitro and in vivo in an asthma model and in response to challenge with a parasite antigen. Dec2 promotes interleukin 4 (IL-4), IL-5 and IL-13 expression during early TH2 differentiation, and directly binds to and activates transcription of the Junb and Gata3 genes. As GATA3 induces Dec2 expression, these findings also indicate a feed-forward regulatory circuit during TH2 differentiation.

Yang, Xuexian O.; Angkasekwinai, Pornpimon; Zhu, Jinfang; Peng, Juan; Liu, Zhiduo; Nurieva, Roza; Liu, Xikui; Chung, Yeonseok; Chang, Seon Hee; Sun, Bing; Dong, Chen

2009-01-01

23

Specific Protein-Protein Interaction between Basic Helix-Loop-Helix Transcription Factors and Homeoproteins of the Pitx Family  

PubMed Central

Homeoproteins and basic helix-loop-helix (bHLH) transcription factors are known for their critical role in development and cellular differentiation. The pituitary pro-opiomelanocortin (POMC) gene is a target for factors of both families. Indeed, pituitary-specific transcription of POMC depends on the action of the homeodomain-containing transcription factor Pitx1 and of bHLH heterodimers containing NeuroD1. We now show lineage-restricted expression of NeuroD1 in pituitary corticotroph cells and a direct physical interaction between bHLH heterodimers and Pitx1 that results in transcriptional synergism. The interaction between the bHLH and homeodomains is restricted to ubiquitous (class A) bHLH and to the Pitx subfamily. Since bHLH heterodimers interact with Pitx factors through their ubiquitous moiety, this mechanism may be implicated in other developmental processes involving bHLH factors, such as neurogenesis and myogenesis.

Poulin, Gino; Lebel, Melanie; Chamberland, Michel; Paradis, Francois W.; Drouin, Jacques

2000-01-01

24

Characterization of the transcriptional activity of the basic helix-loop-helix (bHLH) transcription factor Atoh8.  

PubMed

The atonal-related Neurogenin/NeuroD family of basic helix-loop-helix (bHLH) transcription factors comprises potent inducers of neuronal and endocrine differentiation programs in the nervous and digestive system. Atonal homolog 8 (Atoh8) displays high similarity in the bHLH domain with NeuroD proteins. Yet, available evidences indicate that Atoh8 has distinctive features including a ubiquitous expression pattern in embryonic tissues and the ability to inhibit differentiation. To gain insights into Atoh8 function, we aimed at identifying Atoh8 targets and investigated the effects of Atoh8 on global gene expression patterns in pancreatic mPAC cells, a model of bHLH-dependent endocrine differentiation. Our data reveal that Atoh8 is a weak transcriptional activator and does not exhibit proendocrine activity. Conversely, it blocks the induction of a reduced group of gene targets of the atonal-related proendocrine factor Neurogenin3. We show that Atoh8 lacks a transactivation domain and possesses intrinsic repressor activity that depends on a conserved Proline-rich domain. Atoh8 binds the ubiquitous E protein E47 and its ability to repress transcription may partly result from its ability to inhibit E47/E47 and Neurogenin3/E47 dimer activities. These results reveal distinctive transcriptional properties of Atoh8 within the atonal-related bHLH family that may be associated with the acquisition of new biological functions. PMID:23938248

Ejarque, Miriam; Altirriba, Jordi; Gomis, Ramon; Gasa, Rosa

2013-08-09

25

The basic helix-loop-helix leucine zipper transcription factor Mitf is conserved in Drosophila and functions in eye development.  

PubMed Central

The MITF protein is a member of the MYC family of basic helix-loop-helix leucine zipper (bHLH-Zip) transcription factors and is most closely related to the TFE3, TFEC, and TFEB proteins. In the mouse, MITF is required for the development of several different cell types, including the retinal pigment epithelial (RPE) cells of the eye. In Mitf mutant mice, the presumptive RPE cells hyperproliferate, abnormally express the retinal transcriptional regulator Pax6, and form an ectopic neural retina. Here we report the structure of the Mitf gene in Drosophila and demonstrate expression during embryonic development and in the eye-antennal imaginal disc. In vitro, transcriptional regulation by Drosophila Mitf, like its mouse counterpart, is modified by the Eyeless (Drosophila Pax6) transcription factor. In vivo, targeted expression of wild-type or dominant-negative Drosophila Mitf results in developmental abnormalities reminiscent of Mitf function in mouse eye development. Our results suggest that the Mitf gene is the original member of the Mitf-Tfe subfamily of bHLH-Zip proteins and that its developmental function is at least partially conserved between vertebrates and invertebrates. These findings further support the common origin of the vertebrate and invertebrate eyes.

Hallsson, Jon H; Haflidadottir, Benedikta S; Stivers, Chad; Odenwald, Ward; Arnheiter, Heinz; Pignoni, Francesca; Steingrimsson, Eirikur

2004-01-01

26

anthocyanin1 of Petunia Encodes a Basic Helix-Loop-Helix Protein That Directly Activates Transcription of Structural Anthocyanin Genes  

PubMed Central

The petunia loci anthocyanin1 (an1), an2, an4, and an11 are required for the transcription of anthocyanin biosynthetic genes in floral organs. The an2 and an11 loci were recently cloned and shown to encode a MYB-domain transcriptional activator and a cytosolic WD40 protein, respectively. Here, we report the isolation of an1 by transposon tagging. an1 encodes a new member of the basic helix-loop-helix family of transcription factors that is functionally and evolutionarily distinct from JAF13, the apparent petunia ortholog of maize RED1 and snapdragon DELILA. We provide genetic evidence that the transcription factors encoded by an1, an2, and an4 operate in an unexpectedly complex regulatory hierarchy. In leaves, ectopic expression of AN2 induces an1 expression, whereas in anthers, an1 expression depends on an4, encoding (or controlling) a MYB protein that is paralogous to AN2. Experiments with transgenic plants expressing a post-translationally controlled AN1–GLUCOCORTICOID RECEPTOR fusion protein indicated that independent of protein synthesis, AN1 directly activates the expression of the dfrA gene encoding the enzyme dihydroflavonol 4-reductase and of Pmyb27 encoding a MYB-domain protein of unknown function.

Spelt, Cornelis; Quattrocchio, Francesca; Mol, Joseph N. M.; Koes, Ronald

2000-01-01

27

The basic helix loop helix transcription factor Twist1 is a novel regulator of ATF4 in osteoblasts  

PubMed Central

Parathyroid hormone (PTH) is an essential regulator of endochondral bone formation and an important anabolic agent for the reversal of bone loss. PTH mediates its functions in part by regulating binding of the bone-related activating transcription factor 4 (ATF4) to the osteoblast-specific gene, osteocalcin. The basic helix-loop-helix (bHLH) factors Twist1 and Twist2 also regulate osteocalcin transcription in part through the interaction of the C-terminal “box” domain in these factors and Runx2. In this study, we discovered a novel function of PTH: its ability to dramatically decrease Twist1 transcription. Since ATF4 is a major regulator of the PTH response in osteoblasts, we assessed the mutual regulation between these factors and determined that Twist proteins and ATF4 physically interact in a manner that affects ATF4 DNA binding function. We mapped the interaction domain of Twist proteins to the C-terminal “box” domain and of ATF4, to the N-terminus. Furthermore, we demonstrate that Twist1 overexpression in osteoblasts attenuates ATF4 binding to the osteocalcin promoter in response to PTH. This study thus identifies Twist proteins as novel inhibitory binding partners of ATF4 and explores the functional significance of this interaction.

Danciu, Theodora E.; Li, Yan; Koh, Amy; Xiao, Guozhi; McCauley, Laurie K.; Franceschi, Renny T.

2011-01-01

28

The basic helix loop helix transcription factor Twist1 is a novel regulator of ATF4 in osteoblasts.  

PubMed

Parathyroid hormone (PTH) is an essential regulator of endochondral bone formation and an important anabolic agent for the reversal of bone loss. PTH mediates its functions in part by regulating binding of the bone-related activating transcription factor 4 (ATF4) to the osteoblast-specific gene, osteocalcin. The basic helix-loop-helix (bHLH) factors Twist1 and Twist2 also regulate osteocalcin transcription in part through the interaction of the C-terminal "box" domain in these factors and Runx2. In this study, we discovered a novel function of PTH: its ability to dramatically decrease Twist1 transcription. Since ATF4 is a major regulator of the PTH response in osteoblasts, we assessed the mutual regulation between these factors and determined that Twist proteins and ATF4 physically interact in a manner that affects ATF4 DNA binding function. We mapped the interaction domain of Twist proteins to the C-terminal "box" domain and of ATF4, to the N-terminus. Furthermore, we demonstrate that Twist1 overexpression in osteoblasts attenuates ATF4 binding to the osteocalcin promoter in response to PTH. This study thus identifies Twist proteins as novel inhibitory binding partners of ATF4 and explores the functional significance of this interaction. PMID:21866569

Danciu, Theodora E; Li, Yan; Koh, Amy; Xiao, Guozhi; McCauley, Laurie K; Franceschi, Renny T

2012-01-01

29

Neuronal basic helix-loop-helix proteins Neurod2/6 regulate cortical commissure formation before midline interactions.  

PubMed

Establishment of long-range fiber tracts by neocortical projection neurons is fundamental for higher brain functions. The molecular control of axon tract formation, however, is still poorly understood. Here, we have identified basic helix-loop-helix (bHLH) transcription factors Neurod2 and Neurod6 as key regulators of fasciculation and targeted axogenesis in the mouse neocortex. In Neurod2/6 double-mutant mice, callosal axons lack expression of the cell adhesion molecule Contactin2, defasciculate in the subventricular zone, and fail to grow toward the midline without forming Probst bundles. Instead, mutant axons overexpress Robo1 and follow random trajectories into the ipsilateral cortex. In contrast to long-range axogenesis, generation and maintenance of pyramidal neurons and initial axon outgrowth are grossly normal, suggesting that these processes are under distinct transcriptional control. Our findings define a new stage in corpus callosum development and demonstrate that neocortical projection neurons require transcriptional specification by neuronal bHLH proteins to execute an intrinsic program of remote connectivity. PMID:23303943

Bormuth, Ingo; Yan, Kuo; Yonemasu, Tomoko; Gummert, Maike; Zhang, Mingyue; Wichert, Sven; Grishina, Olga; Pieper, Alexander; Zhang, Weiqi; Goebbels, Sandra; Tarabykin, Victor; Nave, Klaus-Armin; Schwab, Markus H

2013-01-01

30

P/CAF-mediated acetylation regulates the function of the basic helix-loop-helix transcription factor TAL1/SCL  

PubMed Central

The basic helix–loop–helix transcription factor TAL1 (or SCL) is a critical regulator of hematopoietic and vascular development and is misexpressed in the majority of patients with T-cell acute lymphoblastic leukemia. We found previously that TAL1 could interact with transcriptional co-activator and co-repressor complexes possessing histone acetyltransferase and deacetylase activities, respectively. Here, we report that TAL1 is subject to acetylation in vivo and can be acetylated by p300 and the p300/CBP-associated factor P/CAF in vitro. P/CAF-mediated acetylation, which mapped to a lysine-rich motif in the loop region, increased TAL1 binding to DNA while selectively inhibiting its interaction with the transcriptional co-repressor mSin3A. Furthermore, P/CAF protein, TAL1–P/CAF interaction and TAL1 acetylation increased significantly in murine erythroleukemia cells induced to differentiate in culture, while enforced expression of an acetylation-defective P/CAF mutant inhibited endogenous TAL1 acetylation, TAL1 DNA-binding activity, TAL1-directed transcription and terminal differentiation of these cells. These results reveal a novel mechanism by which TAL1 activity is regulated and implicate acetylation of this transcription factor in promotion of erythroid differentiation.

Huang, Suming; Qiu, Yi; Shi, Yubin; Xu, Zhixiong; Brandt, Stephen J.

2000-01-01

31

Selective utilization of basic helix-loop-helix-leucine zipper proteins at the immunoglobulin heavy-chain enhancer.  

PubMed Central

The microE3 E box within the immunoglobulin heavy-chain (IgH) enhancer binds several proteins of the basic helix-loop-helix-leucine zipper (bHLHzip) class, including TFE3, USF1, and Max. Both TFE3 and USF have been described as transcriptional activators, and so we investigated their possible roles in activating the IgH enhancer in vivo. Although TFE3 activated various enhancer-based reporters, both USF1 and Max effectively inhibited transcription. Inhibition by USF correlated with the lack of a strong activation domain and was the result of the protein neutralizing the microE3 site. The effects of dominant-negative derivatives of TFE3 and USF1 confirmed that TFE3, or a TFE3-like protein, is the primary cellular bHLHzip protein that activates the IgH enhancer. In addition to providing a physiological role for TFE3, our results call into question the traditional view of USF1 as an obligate transcriptional activator.

Carter, R S; Ordentlich, P; Kadesch, T

1997-01-01

32

The basic helix-loop-helix transcription factor Mist1 functions as a transcriptional repressor of myoD.  

PubMed Central

A good model system to examine aspects of positive and negative transcriptional regulation is the muscle-specific regulatory factor, MyoD, which is a basic helix-loop-helix (bHLH) transcription factor. Although MyoD has the ability to induce skeletal muscle terminal differentiation in a variety of non-muscle cell types, MyoD activity itself is highly regulated through protein-protein interactions involving several different co-factors. Here we describe the characterization of a novel bHLH protein, Mist1, and how it influences MyoD function. We show that Mist1 accumulates in myogenic stem cells (myoblasts) and then decreases as myoblasts differentiate into myotubes. Mist1 functions as a negative regulator of MyoD activity, preventing muscle differentiation and the concomitant expression of muscle-specific genes. Mist1-induced inhibition occurs through a combination of mechanisms, including the formation of inactive MyoD-Mist1 heterodimers and occupancy of specific E-box target sites by Mist1 homodimers. Mist1 lacks a classic transcription activation domain and instead possesses an N-terminal repressor region capable of inhibiting heterologous activators. Thus, Mist1 may represent a new class of repressor molecules that play a role in controlling the transcriptional activity of MyoD, ensuring that expanding myoblast populations remain undifferentiated during early embryonic muscle formation.

Lemercier, C; To, R Q; Carrasco, R A; Konieczny, S F

1998-01-01

33

Differentiation of Arabidopsis Guard Cells: Analysis of the Networks Incorporating the Basic Helix-Loop-Helix Transcription Factor, FAMA1[C][W][OA  

PubMed Central

Nearly all extant land plants possess stomata, the epidermal structures that mediate gas exchange between the plant and the environment. The developmental pathways, cell division patterns, and molecules employed in the generation of these structures are simple examples of processes used in many developmental contexts. One specific module is a set of “master regulator” basic helix-loop-helix transcription factors that regulate individual consecutive steps in stomatal development. Here, we profile transcriptional changes in response to inducible expression of Arabidopsis (Arabidopsis thaliana) FAMA, a basic helix-loop-helix protein whose actions during the final stage in stomatal development regulate both cell division and cell fate. Genes identified by microarray and candidate approaches were then further analyzed to test specific hypothesis about the activity of FAMA, the shape of its regulatory network, and to create a new set of stomata-specific or stomata-enriched reporters.

Hachez, Charles; Ohashi-Ito, Kyoko; Dong, Juan; Bergmann, Dominique C.

2011-01-01

34

PIAS1 Activates the Expression of Smooth Muscle Cell Differentiation Marker Genes by Interacting with Serum Response Factor and Class I Basic Helix-Loop-Helix Proteins  

Microsoft Academic Search

Although a critical component of vascular disease is modulation of the differentiated state of vascular smooth muscle cells (SMC), the mechanisms governing SMC differentiation are relatively poorly understood. We have previously shown that E-boxes and the ubiquitously expressed class I basic helix-loop-helix (bHLH) proteins, including E2-2 and E12, are important in regulation of the SMC differentiation marker gene, the SM

Keiko Kawai-Kowase; Meena S. Kumar; Mark H. Hoofnagle; Tadashi Yoshida; Gary K. Owens

2005-01-01

35

Hey Basic Helix-Loop-Helix Transcription Factors Are Repressors of GATA4 and GATA6 and Restrict Expression of the GATA Target Gene ANF in Fetal Hearts  

Microsoft Academic Search

The Hey basic helix-loop-helix transcription factors are downstream effectors of Notch signaling in the cardiovascular system. Mice lacking Hey2 develop cardiac hypertrophy, often associated with congenital heart defects, whereas combined Hey1\\/Hey2 deficiency leads to severe vascular defects and embryonic lethality around embryonic day E9.5. The molecular basis of these disorders is poorly understood, however, since target genes of Hey transcription

Andreas Fischer; Jurgen Klattig; Burkhard Kneitz; Holger Diez; Manfred Maier; Bettina Holtmann; Christoph Englert; Manfred Gessler

2005-01-01

36

Multiple Roles of Ligand in Transforming the Dioxin Receptor to an Active Basic Helix-Loop-Helix\\/PAS Transcription Factor Complex with the Nuclear Protein Arnt  

Microsoft Academic Search

The dioxin receptor is a ligand-activated transcription factor belonging to an emerging class of basic helix-loop-helix\\/PAS proteins which show interaction with the molecular chaperone hsp90 in their latent states and require heterodimerization with a general cofactor, Arnt, to form active DNA binding complexes. Upon binding of polycyclic aromatic hydrocarbons typified by dioxin, the dioxin receptor translocates from the cytoplasm to

MICHAEL J. LEES; MURRAY L. WHITELAW

1999-01-01

37

Targeting the Microphthalmia Basic Helix-Loop-Helix-Leucine Zipper Transcription Factor to a Subset of E-Box Elements In Vitro and In Vivo  

Microsoft Academic Search

The development of melanocytes, which are pigment-producing cells responsible for skin, hair, and eye color, is absolutely dependent on the action of the microphthalmia basic helix-loop-helix-leucine zipper (bHLH-LZ) transcription factor (Mi); mice lacking a functional Mi protein are entirely devoid of pigment cells. Mi has been shown to activate transcription of the tyrosinase, TRP-1, TRP-2, and QNR-71 genes through specific

I. AKSAN; C. R. GODING

1998-01-01

38

SREBP-2, a Second Basic-Helix-Loop-Helix-Leucine Zipper Protein that Stimulates Transcription by Binding to a Sterol Regulatory Element  

Microsoft Academic Search

We report the cDNA cloning of SREBP-2, the second member of a family of basic-helix-loop-helix-leucine zipper (bHLH-Zip) transcription factors that recognize sterol regulatory element 1 (SRE-1). SRE-1, a conditional enhancer in the promoters for the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A synthase genes, increases transcription in the absence of sterols and is inactivated when sterols accumulate. Human SREBP-2 contains

Xianxin Hua; Chieko Yokoyama; Jian Wu; Michael R. Briggs; Michael S. Brown; Joseph L. Goldstein; Xiaodong Wang

1993-01-01

39

Conservation of Lotus and Arabidopsis Basic Helix-Loop-Helix Proteins Reveals New Players in Root Hair Development1(W)(OA)  

Microsoft Academic Search

Basic helix-loop-helix (bHLH) proteins constitute a large family of transcriptional regulators in plants. Although they have been shown to play important roles in a wide variety of developmental processes, relatively few have been functionally characterized. Here, we describe the map-based cloning of the Lotus japonicus ROOTHAIRLESS1 (LjRHL1) locus. Deleterious mutations in this locus prevent root hair development, which also aborts

Bogumil Karas; Lisa Amyot; Christopher Johansen; Shusei Sato; Satoshi Tabata; Masayoshi Kawaguchi; Krzysztof Szczyglowski

40

Nhlh1, a basic helix-loop-helix transcription factor, is very tightly linked to the mouse looptail (Lp) mutation.  

PubMed

Looptail (Lp) is a mutation on the distal portion of mouse Chromosome (Chr) 1 that affects neurulation in mouse and is phenotypically expressed by appearance of an open neural tube along the entire antero-posterior axis of the embryo (craniorachischisis). Nhlh1, a member of the basic helix-loop-helix family of transcription factors, is expressed in the developing neural tube in structures affected by the Lp mutation and has been regionally assigned to the distal part of mouse Chr 1. Using a large panel of looptail animals from an (Lp/+ x SWR/J)F1 x SWR/J segregating backcross progeny, we have determined that Nhlh1 maps very close to Lp, with no recombinant detected in 500 informative animals tested; both map within a 0.6-cM segment defined as D1Mit113/Apoa2/Fcer1 gamma-(0.4 cM)-Nhlh1/Lp-(0.2 cM)-Fcer1 alpha/D1Mit149/Spna1. Nucleotide sequencing of Nhlh1 cDNA clones from wild type (WT) and Lp/Lp embryos failed to identify sequence alterations associated with the mutant phenotype. Southern hybridization of genomic DNA from WT and Lp/Lp embryos failed to identify specific rearrangements at or near the Nhlh1 locus, and Northern RNA blotting and RT-PCR evaluation of Nhlh1 mRNA expression indicated that both the levels and types of Nhlh1 mRNAs produced in WT and Lp/Lp embryos were indistinguishable. These studies suggest that Nhlh1 and Lp are not allelic. Nevertheless, Nhlh1 is the Chr 1 marker most tightly linked to Lp identified to date and can, therefore, be used as an excellent entry probe to clone the Lp region. PMID:8563167

Mullick, A; Groulx, N; Trasler, D; Gros, P

1995-10-01

41

Role of the basic helix-loop-helix protein ITF2 in the hormonal regulation of Sertoli cell differentiation.  

PubMed

Sertoli cells are a post-mitotic terminally differentiated cell population that forms the seminiferous tubules in the adult testis and provides the microenvironment and structural support for developing germ cells. During pubertal development, Sertoli cells are responsive to follicle-stimulating hormone (FSH) to promote the expression of differentiated gene products. The basic helix-loop-helix (bHLH) and inhibitors of differentiation (Id) transcription factors are involved in the differentiation of a variety of cell lineages during development. Both bHLH and Id transcription factors have been identified in Sertoli cells. A yeast two-hybrid screen was conducted using a rat Sertoli cell cDNA library to identify bHLH dimerization partners for the Id1 transcription factor. The ubiquitous bHLH protein ITF2 (i.e., E2-2) was identified as one of the interacting partners. The current study investigates the expression and function of ITF2 in Sertoli cells. ITF2 was found to be ubiquitously expressed in all testicular cell types including germ cells, peritubular myoid cells, and Sertoli cells. Stimulation of cultured Sertoli cells with FSH or dibutryl cAMP resulted in a transient decrease in expression of ITF2 mRNA levels followed by a rise in expression with FSH treatment. ITF2 expression was at its highest in mid-pubertal 20-day-old rat Sertoli cells. ITF2 was found to directly bind to negative acting Id HLH proteins and positive acting bHLH proteins such as scleraxis. Transient overexpression of ITF2 protein in cultured Sertoli cells stimulated transferrin promoter activity, which is a marker of Sertoli cell differentiation. Co-transfections of ITF2 and Id proteins sequestered the inhibitory effects of the Id family of proteins. Observations suggest ITF2 can enhance FSH actions through suppressing the inhibitory actions of the Id family of proteins and increasing the actions of stimulatory bHLH proteins (i.e., scleraxis) in Sertoli cells. PMID:16425294

Muir, Terla; Sadler-Riggleman, Ingrid; Stevens, Jeffrey D; Skinner, Michael K

2006-04-01

42

Classification and evolutionary analysis of the basic helix-loop-helix gene family in the green anole lizard, Anolis carolinensis.  

PubMed

Helix-loop-helix (bHLH) proteins play essential regulatory roles in a variety of biological processes. These highly conserved proteins form a large transcription factor superfamily, and are commonly identified in large numbers within animal, plant, and fungal genomes. The bHLH domain has been well studied in many animal species, but has not yet been characterized in non-avian reptiles. In this study, we identified 102 putative bHLH genes in the genome of the green anole lizard, Anolis carolinensis. Based on phylogenetic analysis, these genes were classified into 43 families, with 43, 24, 16, 3, 10, and 3 members assigned into groups A, B, C, D, E, and F, respectively, and 3 members categorized as "orphans". Within-group evolutionary relationships inferred from the phylogenetic analysis were consistent with highly conserved patterns observed for introns and additional domains. Results from phylogenetic analysis of the H/E(spl) family suggest that genome and tandem gene duplications have contributed to this family's expansion. Our classification and evolutionary analysis has provided insights into the evolutionary diversification of animal bHLH genes, and should aid future studies on bHLH protein regulation of key growth and developmental processes. PMID:23756994

Liu, Ake; Wang, Yong; Zhang, Debao; Wang, Xuhua; Song, Huifang; Dang, Chunwang; Yao, Qin; Chen, Keping

2013-06-12

43

Identification and characterization of the zebrafish pharyngeal arch-specific enhancer for the basic helix-loop-helix transcription factor Hand2  

PubMed Central

The development of the vertebrate jaw relies on a network of transcription factors that patterns the dorsal-ventral axis of the pharyngeal arches. Recent findings in both mouse and zebrafish illustrate that the basic-helix-loop-helix transcription factor, Hand2, is crucial in this patterning process. While Hand2 has functionally similar roles in these two species, little is known about the regulatory sequences controlling hand2 expression in zebrafish. Using bioinformatics and Tol2-mediated transgenesis, we have generated zebrafish transgenic reporter lines in which either the mouse or zebrafish arch-specific hand2 enhancer direct expression of a fluorescent reporter. We find that both the mouse and zebrafish enhancers drive early reporter expression in a hand2-specific pattern in the ventral pharyngeal arches of zebrafish embryos. These lines provide useful tools to follow ventral arch cells during vertebrate jaw development while also allowing dissection of hand2 transcriptional regulation during this process.

Ikle, Jennifer M.; Artinger, Kristin B.; Clouthier, David E.

2013-01-01

44

A novel target recognition revealed by calmodulin in complex with the basic helix-loop-helix transcription factor SEF2-1/E2-2  

PubMed Central

Calmodulin is the predominant intracellular receptor for Ca2+ signals, mediating the regulation of numerous cellular processes. It can inhibit the DNA binding of basic helix–loop–helix transcription factors by a direct interaction of a novel type. To structurally characterize this novel calmodulin-target interaction, we decided to study the complex of calmodulin with a dimeric peptide corresponding to the DNA-binding domains of the dimeric basic helix–loop–helix transcription factor SEF2-1 (SEF2-1mp) using NMR. Here, we report that the stoichiometry of the calmodulin:SEF2-1mp complex is one dimeric peptide binding two calmodulin molecules. We also report the 1H, 13C, and 15N resonance assignments and the secondary structure of calmodulin in this for NMR large (?38 kD) complex, as well as the 1H assignments and secondary structure of SEF2-1mp. In addition, we determined the amide proton exchange rates of calmodulin and measured intermolecular calmodulin:SEF2-1mp and calmodulin:calmodulin NOE contacts. The isotope-filtered experiments show a large number of SEF2-1mp to calmodulin NOE contacts indicating that a tight complex is formed, which is confirmed by an intermolecular calmodulin:calmodulin NOE contact. The secondary structure and amide proton exchange data show that the binding does not occur via the classical wraparound binding mode. Instead, the data indicate that calmodulin interacts with SEF2-1mp in a more open conformation, although the hydrophobic surfaces of the N- and C-terminal domains still form the main interaction sites. Interactions involving charged residues are also identified in agreement with the known relatively high sensitivity of the binding to ionic strength. Finally, the peptide does not form an ?-helix as in the classical wraparound binding mode.

Larsson, Goran; Schleucher, Jurgen; Onions, Jacqueline; Hermann, Stefan; Grundstrom, Thoman; Wijmenga, Sybren S.

2001-01-01

45

A novel target recognition revealed by calmodulin in complex with the basic helix--loop--helix transcription factor SEF2-1/E2-2.  

PubMed

Calmodulin is the predominant intracellular receptor for Ca(2+) signals, mediating the regulation of numerous cellular processes. It can inhibit the DNA binding of basic helix--loop--helix transcription factors by a direct interaction of a novel type. To structurally characterize this novel calmodulin-target interaction, we decided to study the complex of calmodulin with a dimeric peptide corresponding to the DNA-binding domains of the dimeric basic helix-loop-helix transcription factor SEF2-1 (SEF2-1mp) using NMR. Here, we report that the stoichiometry of the calmodulin:SEF2-1mp complex is one dimeric peptide binding two calmodulin molecules. We also report the 1H, 13C, and 15N resonance assignments and the secondary structure of calmodulin in this for NMR large (approximately 38 kD) complex, as well as the 1H assignments and secondary structure of SEF2-1mp. In addition, we determined the amide proton exchange rates of calmodulin and measured intermolecular calmodulin:SEF2-1mp and calmodulin:calmodulin NOE contacts. The isotope-filtered experiments show a large number of SEF2-1mp to calmodulin NOE contacts indicating that a tight complex is formed, which is confirmed by an intermolecular calmodulin:calmodulin NOE contact. The secondary structure and amide proton exchange data show that the binding does not occur via the classical wraparound binding mode. Instead, the data indicate that calmodulin interacts with SEF2-1mp in a more open conformation, although the hydrophobic surfaces of the N- and C-terminal domains still form the main interaction sites. Interactions involving charged residues are also identified in agreement with the known relatively high sensitivity of the binding to ionic strength. Finally, the peptide does not form an alpha-helix as in the classical wraparound binding mode. PMID:11266605

Larsson, G; Schleucher, J; Onions, J; Hermann, S; Grundström, T; Wijmenga, S S

2001-01-01

46

The basic domain of myogenic basic helix-loop-helix (bHLH) proteins is the novel target for direct inhibition by another bHLH protein, Twist.  

PubMed Central

In vertebrates, the basic helix-loop-helix (bHLH) protein Twist may be involved in the negative regulation of cellular determination and in the differentiation of several lineages, including myogenesis, osteogenesis, and neurogenesis. Although it has been shown that mouse twist (M-Twist) (i) sequesters E proteins, thus preventing formation of myogenic E protein-MyoD complexes and (ii) inhibits the MEF2 transcription factor, a cofactor of myogenic bHLH proteins, overexpression of E proteins and MEF2 failed to rescue the inhibitory effects of M-Twist on MyoD. We report here that M-Twist physically interacts with the myogenic bHLH proteins in vitro and in vivo and that this interaction is required for the inhibition of MyoD by M-Twist. In contrast to the conventional HLH-HLH domain interaction formed in the MyoD/E12 heterodimer, this novel type of interaction uses the basic domains of the two proteins. While the MyoD HLH domain without the basic domain failed to interact with M-Twist, a MyoD peptide containing only the basic and helix 1 regions was sufficient to interact with M-Twist, suggesting that the basic domain contacts M-Twist. The replacement of three arginine residues by alanines in the M-Twist basic domain was sufficient to abolish both the binding and inhibition of MyoD by M-Twist, while the domain retained other M-Twist functions such as heterodimerization with an E protein and inhibition of MEF2 transactivation. These findings demonstrate that M-Twist interacts with MyoD through the basic domains, thereby inhibiting MyoD.

Hamamori, Y; Wu, H Y; Sartorelli, V; Kedes, L

1997-01-01

47

Regulation of Id1 and its association with basic helix-loop-helix proteins during nerve growth factor-induced differentiation of PC12 cells.  

PubMed Central

Cell differentiation in the nervous system is dictated by specific patterns of gene expression. We have investigated the role of helix-loop-helix (HLH) proteins during differentiation of PC12 pheochromocytoma cells in response to nerve growth factor. Gel mobility shift assays using PC12 cell nuclear extracts demonstrated that active basic HLH complexes exist throughout differentiation. Addition of exogeneous Id1 protein, a negative regulator of basic HLH proteins, disrupted specific complexes formed by PC12 cell nuclear extracts on a CANNTG consensus oligonucleotide. To identify possible novel basic HLH proteins in these complexes, a glutathione S-transferase-Id1 fusion protein was used to screen a PC12 cell cDNA expression library. A single clone representing the rat E2-2 gene was identified. Sequential immunoprecipitations with antibodies to each HLH protein revealed an association between Id1 and E2-2 that could be detected in both untreated and nerve growth factor-treated PC12 cell lysates. These experiments define a new HLH interaction between Id1 and E2-2 in neuronal cells and suggest that neuronal differentiation may be regulated by HLH proteins in a distinctive manner.

Einarson, M B; Chao, M V

1995-01-01

48

Identification and characterization of a putative basic helix-loop-helix (bHLH) transcription factor interacting with calcineurin in C. elegans.  

PubMed

Calcineurin is a Ca(2+)/Calmodulin activated Ser/Thr phosphatase that is well conserved from yeast to human. It is composed of catalytic subunit A (CnA) and regulatory subunit B (CnB). C. elegans homolog of CnA and CnB has been annotated to tax-6 and cnb-1, respectively and in vivo function of both genes has been intensively studied. In C. elegans, calcineurin play roles in various signaling pathways such as fertility, movement, body size regulation and serotonin-mediated egg laying. In order to understand additional signaling pathway(s) in which calcineurin functions, we screened for binding proteins of TAX-6 and found a novel binding protein, HLH-11. The HLH-11, a member of basic helix-loop-helix (bHLH) proteins, is a putative counterpart of human AP4 transcription factor. Previously bHLH transcription factors have been implicated to regulate many developmental processes such as cell proliferation and differentiation, sex determination and myogenesis. However, the in vivo function of hlh-11 is largely unknown. Here, we show that hlh-11 is expressed in pharynx, intestine, nerve cords, anal depressor and vuvla muscles where calcineurin is also expressed. Mutant analyses reveal that hlh-11 may have role(s) in regulating body size and reproduction. More interestingly, genetic epistasis suggests that hlh-11 may function to regulate serotonin-mediated egg laying at the downstream of tax-6. PMID:19855932

Lee, Soo-Ung; Song, Hyun-Ok; Lee, Wonhae; Singaravelu, Gunasekaran; Yu, Jae-Ran; Park, Woo-Yoon

2009-10-21

49

Sequence and function of basic helix-loop-helix proteins required for stomatal development in Arabidopsis are deeply conserved in land plants.  

PubMed

Stomata are a broadly conserved feature of land plants with a crucial role regulating transpiration and gas exchange between the plant and atmosphere. Stereotyped cell divisions within a specialized cell lineage of the epidermis generate stomata and define the pattern of their distribution. The behavior of the stomatal lineage varies in its detail among different plant groups, but general features include asymmetric cell divisions and an immediate precursor (the guard mother cell [GMC]) that divides symmetrically to form the pair of cells that will differentiate into the guard cells. In Arabidopsis, the closely related basic helix-loop-helix (bHLH) subgroup Ia transcription factors SPEECHLESS, MUTE, and FAMA promote asymmetric divisions, the acquisition of GMC identity and guard cell differentiation, respectively. Genome sequence data indicate that these key positive regulators of stomatal development are broadly conserved among land plants. While orthologies can be established among individual family members within the angiosperms, more distantly related groups contain subgroup Ia bHLHs of unclear affinity. We demonstrate group Ia members from the moss Physcomitrella patens can partially complement MUTE and FAMA and recapitulate gain of function phenotypes of group Ia genes in multiple steps in the stomatal lineage in Arabidopsis. Our data are consistent with a mechanism whereby a multifunctional transcription factor underwent duplication followed by specialization to provide the three (now nonoverlapping) functions of the angiosperm stomatal bHLHs. PMID:21410874

MacAlister, Cora A; Bergmann, Dominique C

50

Arabidopsis Basic Helix-Loop-Helix Transcription Factors MYC2, MYC3, and MYC4 Regulate Glucosinolate Biosynthesis, Insect Performance, and Feeding Behavior.  

PubMed

Arabidopsis thaliana plants fend off insect attack by constitutive and inducible production of toxic metabolites, such as glucosinolates (GSs). A triple mutant lacking MYC2, MYC3, and MYC4, three basic helix-loop-helix transcription factors that are known to additively control jasmonate-related defense responses, was shown to have a highly reduced expression of GS biosynthesis genes. The myc2 myc3 myc4 (myc234) triple mutant was almost completely devoid of GS and was extremely susceptible to the generalist herbivore Spodoptera littoralis. On the contrary, the specialist Pieris brassicae was unaffected by the presence of GS and preferred to feed on wild-type plants. In addition, lack of GS in myc234 drastically modified S. littoralis feeding behavior. Surprisingly, the expression of MYB factors known to regulate GS biosynthesis genes was not altered in myc234, suggesting that MYC2/MYC3/MYC4 are necessary for direct transcriptional activation of GS biosynthesis genes. To support this, chromatin immunoprecipitation analysis showed that MYC2 binds directly to the promoter of several GS biosynthesis genes in vivo. Furthermore, yeast two-hybrid and pull-down experiments indicated that MYC2/MYC3/MYC4 interact directly with GS-related MYBs. This specific MYC-MYB interaction plays a crucial role in the regulation of defense secondary metabolite production and underlines the importance of GS in shaping plant interactions with adapted and nonadapted herbivores. PMID:23943862

Schweizer, Fabian; Fernández-Calvo, Patricia; Zander, Mark; Diez-Diaz, Monica; Fonseca, Sandra; Glauser, Gaétan; Lewsey, Mathew G; Ecker, Joseph R; Solano, Roberto; Reymond, Philippe

2013-08-13

51

The role of an E box binding basic helix loop helix protein in the cardiac muscle-specific expression of the rat cytochrome oxidase subunit VIII gene.  

PubMed

We have characterized the rat gene for muscle-specific cytochrome oxidase VIII (COX VIII(H)) and mapped the distal promoter region responsible for transcription activation in C2C12 skeletal myocytes and H9C2 cardiomyocytes. In both cell types, the promoter elements responding to the induced differentiation of myocytes map to two E boxes, designated as E1 and E2 boxes with a core sequence of CAGCTG. Gel mobility shift analysis showed that both E1 and E2 box motifs form complexes with nuclear extracts from H9C2 cardiomyocytes that were supershifted with monoclonal antibody to E2A but not with antibody to myo-D. Extracts from induced and uninduced H9C2 cardiomyocytes yielded different gel mobility patterns and also different E2A antibody supershifts suggesting a difference in the DNA-bound protein complexes cross-reacting with the E2A antibody. Transcriptional activity of the promoter construct containing intact E boxes was inhibited by coexpression with Id in differentiated H9C2 cardiomyocytes. Our results show the involvement of an E box binding basic helix loop helix protein in the cardiac muscle-specific regulation of the COX VIII(H) promoter. PMID:8939982

Lenka, N; Basu, A; Mullick, J; Avadhani, N G

1996-11-22

52

The p48 DNA-binding subunit of transcription factor PTF1 is a new exocrine pancreas-specific basic helix-loop-helix protein.  

PubMed Central

We report the isolation of cDNA for the p48 DNA-binding subunit of the heterooligomeric transcription factor PTF1. A sequence analysis of the cDNA demonstrates that p48 is a new member of the family of basic helix-loop-helix (bHLH) transcription factors. The p48 bHLH domain shows striking amino acid sequence similarity with the bHLH domain of proteins that act as developmental regulators, including the twist gene product, myogenic factors and proteins involved in hematopoietic differentiation. We show that reduced p48 synthesis correlates with a diminished expression of genes encoding exocrine pancreas-specific functions. The synthesis of p48 mRNAs, and therefore also the protein, is restricted to cells of the exocrine pancreas in the adult and to the pancreatic primordium in the embryo. Thus the pancreas-specific DNA-binding activity of PTF1 originates from the synthesis of at least one cell-specific component rather than from a cell-specific assembly of more widely distributed proteins. Images

Krapp, A; Knofler, M; Frutiger, S; Hughes, G J; Hagenbuchle, O; Wellauer, P K

1996-01-01

53

Elevated endogenous expression of the dominant negative basic helix-loop-helix protein ID1 correlates with significant centrosome abnormalities in human tumor cells  

PubMed Central

Background ID proteins are dominant negative inhibitors of basic helix-loop-helix transcription factors that have multiple functions during development and cellular differentiation. Ectopic (over-)expression of ID1 extends the lifespan of primary human epithelial cells. High expression levels of ID1 have been detected in multiple human malignancies, and in some have been correlated with unfavorable clinical prognosis. ID1 protein is localized at the centrosomes and forced (over-)expression of ID1 results in errors during centrosome duplication. Results Here we analyzed the steady state expression levels of the four ID-proteins in 18 tumor cell lines and assessed the number of centrosome abnormalities. While expression of ID1, ID2, and ID3 was detected, we failed to detect protein expression of ID4. Expression of ID1 correlated with increased supernumerary centrosomes in most cell lines analyzed. Conclusions This is the first report that shows that not only ectopic expression in tissue culture but endogenous levels of ID1 modulate centrosome numbers. Thus, our findings support the hypothesis that ID1 interferes with centrosome homeostasis, most likely contributing to genomic instability and associated tumor aggressiveness.

2010-01-01

54

Targeted Disruption of NeuroD, a Proneural Basic Helix-Loop-Helix Factor, Impairs Distal Lung Formation and Neuroendocrine Morphology in the Neonatal Lung*S?  

PubMed Central

Despite the importance of airspace integrity in vertebrate gas exchange, the molecular pathways that instruct distal lung formation are poorly understood. Recently, we found that fibrillin-1 deficiency in mice impairs alveolar formation and recapitulates the pulmonary features of human Marfan syndrome. To further elucidate effectors involved in distal lung formation, we performed expression profiling analysis comparing the fibrillin-1-deficient and wild-type developing lung. NeuroD, a basic helix-loop-helix transcription factor, fulfilled the expression criteria for a candidate mediator of distal lung development. We investigated its role in murine lung development using genetically targeted NeuroD-deficient mice. We found that NeuroD deficiency results in both impaired alveolar septation and altered morphology of the pulmonary neuroendocrine cells. NeuroD-deficient mice had enlarged alveoli associated with reduced epithelial proliferation in the airway and airspace compartments during development. Additionally, the neuroendocrine compartment in these mice manifested an increased number of neuroepithelial bodies but a reduced number of solitary pulmonary neuroendocrine cells in the neonatal lung. Overexpression of NeuroD in a murine lung epithelial cell line conferred a neuroendocrine phenotype characterized by the induction of neuroendocrine markers as well as increased proliferation. These results support an unanticipated role for NeuroD in the regulation of pulmonary neuroendocrine and alveolar morphogenesis and suggest an intimate connection between the neuroendocrine compartment and distal lung development.

Neptune, Enid R.; Podowski, Megan; Calvi, Carla; Cho, Jang-Hyeon; Garcia, Joe G. N.; Tuder, Rubin; Linnoila, R. Ilona; Tsai, Ming-Jer; Dietz, Harry C.

2008-01-01

55

An-1 encodes a basic helix-loop-helix protein that regulates awn development, grain size, and grain number in rice.  

PubMed

Long awns are important for seed dispersal in wild rice (Oryza rufipogon), but are absent in cultivated rice (Oryza sativa). The genetic mechanism involved in loss-of-awn in cultivated rice remains unknown. We report here the molecular cloning of a major quantitative trait locus, An-1, which regulates long awn formation in O. rufipogon. An-1 encodes a basic helix-loop-helix protein, which regulates cell division. The nearly-isogenic line (NIL-An-1) carrying a wild allele An-1 in the genetic background of the awnless indica Guangluai4 produces long awns and longer grains, but significantly fewer grains per panicle compared with Guangluai4. Transgenic studies confirmed that An-1 positively regulates awn elongation, but negatively regulates grain number per panicle. Genetic variations in the An-1 locus were found to be associated with awn loss in cultivated rice. Population genetic analysis of wild and cultivated rice showed a significant reduction in nucleotide diversity of the An-1 locus in rice cultivars, suggesting that the An-1 locus was a major target for artificial selection. Thus, we propose that awn loss was favored and strongly selected by humans, as genetic variations at the An-1 locus that cause awn loss would increase grain numbers and subsequently improve grain yield in cultivated rice. PMID:24076974

Luo, Jianghong; Liu, Hui; Zhou, Taoying; Gu, Benguo; Huang, Xuehui; Shangguan, Yingying; Zhu, Jingjie; Li, Yan; Zhao, Yan; Wang, Yongchun; Zhao, Qiang; Wang, Ahong; Wang, Ziqun; Sang, Tao; Wang, Zixuan; Han, Bin

2013-09-27

56

Involvement of a Nuclear-Encoded Basic Helix-Loop-Helix Protein in Transcription of the Light-Responsive Promoter of psbD1  

PubMed Central

In the chloroplast psbD light-responsive promoter (LRP), a highly conserved sequence exists upstream from the bacterial ?10/?35 elements. Multiple sequence-specific DNA binding proteins are predicted to bind to the conserved sequence as transcription factors. Using yeast one-hybrid screening of an Arabidopsis cDNA library, a possible DNA binding protein of the psbD LRP upstream sequence was identified. The protein, designated PTF1, is a novel protein of 355 amino acids (estimated molecular weight of 39.6) that contains a basic helix-loop-helix DNA binding motif in the predicted N-terminal region of the mature protein. Transient expression assay of PTF1-GFP fusion protein showed that PTF1 was localized in chloroplasts. Using the modified DNA sequence in the one-hybrid system, the ACC repeat was shown to be essential for PTF1 binding. The rate of psbD LRP mRNA accumulation was reduced in a T-DNA-inserted Arabidopsis ptf1 mutant. Compared with wild-type plants, the mutant had pale green cotyledons and its growth was inhibited under short-day conditions. These results suggest that PTF1 is a trans-acting factor of the psbD LRP.

Baba, Kyoko; Nakano, Takeshi; Yamagishi, Kazutoshi; Yoshida, Shigeo

2001-01-01

57

MondoA, a novel basic helix-loop-helix-leucine zipper transcriptional activator that constitutes a positive branch of a max-like network.  

PubMed

Max is a common dimerization partner for a family of transcription factors (Myc, Mad [or Mxi]), and Mnt [or Rox] proteins) that regulate cell growth, proliferation, and apoptosis. We recently characterized a novel Max-like protein, Mlx, which interacts with Mad1 and Mad4. Here we describe the cloning and functional characterization of a new family of basic helix-loop-helix-leucine zipper heterodimeric partners for Mlx termed the Mondo family. MondoA forms homodimers weakly and does not interact with Max or members of the Myc or Mad families. MondoA and Mlx associate in vivo, and surprisingly, they are localized primarily to the cytoplasm of cultured mammalian cells. Treatment of cells with the nuclear export inhibitor leptomycin B results in the nuclear accumulation of MondoA and Mlx, demonstrating that they shuttle between the cytoplasmic and nuclear compartments rather than having exclusively cytoplasmic localization. MondoA preferentially forms heterodimers with Mlx, and this heterocomplex can bind to, and activate transcription from, CACGTG E-boxes when targeted to the nucleus via a heterologous nuclear localization signal. The amino termini of the Mondo proteins are highly conserved among family members and contain separable and autonomous cytoplasmic localization and transcription activation domains. Therefore, Mlx can mediate transcriptional repression in conjunction with the Mad family and can mediate transcriptional activation via the Mondo family. We propose that Mlx, like Max, functions as the center of a transcription factor network. PMID:11073985

Billin, A N; Eilers, A L; Coulter, K L; Logan, J S; Ayer, D E

2000-12-01

58

Embryonic expression of mSharp-1/mDEC2, which encodes a basic helix-loop-helix transcription factor.  

PubMed

We describe the expression pattern of mouse Sharp-1 (mSharp-1), a member of the basic helix-loop-helix (bHLH) family of transcription factors. mSharp-1 belongs to the Hairy/Enhancer of Split (E(Spl)) subfamily of bHLH factors that are key targets of the Notch signaling pathway and exhibits the highest sequence identity with Stra13. RNA in situ hybridization analysis from embryonic day 7.5 (E7.5) to E16.5 revealed specific expression of mSharp-1 in several developing organs during mouse embryogenesis. In early stage embryos (E8.5-E12.5), mSharp-1 is expressed in specific dorsal regions of the developing brain, the heart, the developing eye and olfactory system, as well as in the limb buds. At later stages (E12.5-E16.5), mSharp-1 is also expressed in the liver, prevertebrae, and the developing adrenal and thyroid glands. The diversity of its expression pattern suggests that mSharp-1 may regulate the differentiation of several cell types during vertebrate development. PMID:12175508

Azmi, Sameena; Taneja, Reshma

2002-06-01

59

Molecular characterization of cold-responsive basic helix-loop-helix transcription factors MabHLHs that interact with MaICE1 in banana fruit.  

PubMed

Basic helix-loop-helix (bHLH) transcription factors (TFs) are ubiquitously involved in the response of higher plants to various abiotic stresses. However, little is known about bHLH TFs involved in the cold stress response in economically important fruits. Here, five novel full-length bHLH genes, designated as MabHLH1-MabHLH5, were isolated and characterized from banana fruit. Gene expression profiles revealed that MabHLH1/2/4 were induced by cold stress and methyl jasmonate (MeJA) treatment. Transient assays in tobacco BY2 protoplasts showed that MabHLH1/2/4 promoters were activated by cold stress and MeJA treatments. Moreover, protein-protein interaction analysis demonstrated that MabHLH1/2/4 not only physically interacted with each other to form hetero-dimers in the nucleus, but also interacted with an important upstream component of cold signaling MaICE1, with different interaction domains at their N-terminus. These results indicate that banana fruit cold-responsive MabHLHs may form a big protein complex in the nucleus with MaICE1. Taken together, our findings advance our understanding of the possible involvement of bHLH TFs in the regulatory network of ICE-CBF cold signaling pathway. PMID:23955147

Peng, Huan-Huan; Shan, Wei; Kuang, Jian-Fei; Lu, Wang-Jin; Chen, Jian-Ye

2013-08-17

60

Regulatory switch enforced by basic helix-loop-helix and ACT-domain mediated dimerizations of the maize transcription factor R.  

PubMed

The maize R2R3-MYB regulator C1 cooperates with the basic helix-loop-helix (bHLH) factor R to activate the expression of anthocyanin biosynthetic genes coordinately. As is the case for other bHLH factors, R harbors several protein-protein interaction domains. Here we show that not the classical but rather a briefly extended R bHLH region forms homodimers that bind canonical G-box DNA motifs. This bHLH DNA-binding activity is abolished if the C-terminal ACT (aspartokinase, chorismate, and TyrA) domain is licensed to homodimerize. Then the bHLH remains in the monomeric form, allowing it to interact with R-interacting factor 1 (RIF1). In this configuration, the R-RIF1 complex is recruited to the promoters of a subset of anthocyanin biosynthetic genes, such as A1, through the interaction with its MYB partner C1. If, however, the ACT domain remains monomeric, the bHLH region dimerizes and binds to G-boxes present in several anthocyanin genes, such as Bz1. Our results provide a mechanism by which a dimerization domain in a bHLH factor behaves as a switch that permits distinct configurations of a regulatory complex to be tethered to different promoters. Such a combinatorial gene regulatory framework provides one mechanism by which genes lacking obviously conserved cis-regulatory elements are regulated coordinately. PMID:22778424

Kong, Que; Pattanaik, Sitakanta; Feller, Antje; Werkman, Joshua R; Chai, Chenglin; Wang, Yongqin; Grotewold, Erich; Yuan, Ling

2012-07-09

61

Arabidopsis Basic Helix-Loop-Helix Transcription Factors MYC2, MYC3, and MYC4 Regulate Glucosinolate Biosynthesis, Insect Performance, and Feeding Behavior[W][OPEN  

PubMed Central

Arabidopsis thaliana plants fend off insect attack by constitutive and inducible production of toxic metabolites, such as glucosinolates (GSs). A triple mutant lacking MYC2, MYC3, and MYC4, three basic helix-loop-helix transcription factors that are known to additively control jasmonate-related defense responses, was shown to have a highly reduced expression of GS biosynthesis genes. The myc2 myc3 myc4 (myc234) triple mutant was almost completely devoid of GS and was extremely susceptible to the generalist herbivore Spodoptera littoralis. On the contrary, the specialist Pieris brassicae was unaffected by the presence of GS and preferred to feed on wild-type plants. In addition, lack of GS in myc234 drastically modified S. littoralis feeding behavior. Surprisingly, the expression of MYB factors known to regulate GS biosynthesis genes was not altered in myc234, suggesting that MYC2/MYC3/MYC4 are necessary for direct transcriptional activation of GS biosynthesis genes. To support this, chromatin immunoprecipitation analysis showed that MYC2 binds directly to the promoter of several GS biosynthesis genes in vivo. Furthermore, yeast two-hybrid and pull-down experiments indicated that MYC2/MYC3/MYC4 interact directly with GS-related MYBs. This specific MYC–MYB interaction plays a crucial role in the regulation of defense secondary metabolite production and underlines the importance of GS in shaping plant interactions with adapted and nonadapted herbivores.

Schweizer, Fabian; Fernandez-Calvo, Patricia; Zander, Mark; Diez-Diaz, Monica; Fonseca, Sandra; Glauser, Gaetan; Lewsey, Mathew G.; Ecker, Joseph R.; Solano, Roberto; Reymond, Philippe

2013-01-01

62

B-lymphocyte development is regulated by the combined dosage of three basic helix-loop-helix genes, E2A, E2-2, and HEB.  

PubMed Central

B-lymphocyte development requires the basic helix-loop-helix proteins encoded by the E2A gene. In this study, the control mechanism of E2A was further explored by disruption of the E2A-related genes, E2-2 and HEB. In contrast to E2A, E2-2 and HEB are not essential for the establishment of the B-cell lineage. However, both E2-2 and HEB are required for the generation of the normal numbers of pro-B cells in mouse embryos. Breeding tests among mice carrying different mutations revealed that E2-2 and HEB interact with E2A in many developmental processes including generation of B cells. Specifically, mice transheterozygous for any two mutations of these three genes produced fewer pro-B cells than the singly heterozygous littermates. This study indicates that B-cell development is dependent not only on an essential function provided by the E2A gene but also on a combined dosage set by E2A, E2-2, and HEB.

Zhuang, Y; Cheng, P; Weintraub, H

1996-01-01

63

Antagonistic basic helix-loop-helix/bZIP transcription factors form transcriptional modules that integrate light and reactive oxygen species signaling in Arabidopsis.  

PubMed

The critical developmental switch from heterotrophic to autotrophic growth of plants involves light signaling transduction and the production of reactive oxygen species (ROS). ROS function as signaling molecules that regulate multiple developmental processes, including cell death. However, the relationship between light and ROS signaling remains unclear. Here, we identify transcriptional modules composed of the basic helix-loop-helix and bZIP transcription factors PHYTOCHROME-INTERACTING FACTOR1 (PIF1), PIF3, ELONGATED HYPOCOTYL5 (HY5), and HY5 HOMOLOGY (HYH) that bridge light and ROS signaling to regulate cell death and photooxidative response. We show that pif mutants release more singlet oxygen and exhibit more extensive cell death than the wild type during Arabidopsis thaliana deetiolation. Genome-wide expression profiling indicates that PIF1 represses numerous ROS and stress-related genes. Molecular and biochemical analyses reveal that PIF1/PIF3 and HY5/HYH physically interact and coordinately regulate the expression of five ROS-responsive genes by directly binding to their promoters. Furthermore, PIF1/PIF3 and HY5/HYH function antagonistically during the seedling greening process. In addition, phytochromes, cryptochromes, and CONSTITUTIVE PHOTOMORPHOGENIC1 act upstream to regulate ROS signaling. Together, this study reveals that the PIF1/PIF3-HY5/HYH transcriptional modules mediate crosstalk between light and ROS signaling and sheds light on a new mechanism by which plants adapt to the light environments. PMID:23645630

Chen, Dongqin; Xu, Gang; Tang, Weijiang; Jing, Yanjun; Ji, Qiang; Fei, Zhangjun; Lin, Rongcheng

2013-05-03

64

PTF1 Is an Organ-Specific and Notch-Independent Basic Helix-Loop-Helix Complex Containing the Mammalian Suppressor of Hairless (RBP-J) or Its Paralogue, RBP-L  

Microsoft Academic Search

PTF1 is a trimeric transcription factor essential to the development of the pancreas and to the maintenance of the differentiated state of the adult exocrine pancreas. It comprises a dimer of P48\\/PTF1a (a pancreas and neural restricted basic helix-loop-helix (bHLH) protein) and a class A bHLH protein, together with a third protein that we show can be either the mammalian

Thomas M. Beres; Toshihiko Masui; Galvin H. Swift; Ling Shi; R. Michael Henke; Raymond J. MacDonald

2006-01-01

65

MicroRNA-212 Post-Transcriptionally Regulates Oocyte-Specific Basic-Helix-Loop-Helix Transcription Factor, Factor in the Germline Alpha (FIGLA), during Bovine Early Embryogenesis.  

PubMed

Factor in the germline alpha (FIGLA) is an oocyte-specific basic helix-loop-helix transcription factor essential for primordial follicle formation and expression of many genes required for folliculogenesis, fertilization and early embryonic survival. Here we report the characterization of bovine FIGLA gene and its regulation during early embryogenesis. Bovine FIGLA mRNA expression is restricted to gonads and is detected in fetal ovaries harvested as early as 90 days of gestation. FIGLA mRNA and protein are abundant in germinal vesicle and metaphase II stage oocytes, as well as in embryos from pronuclear to eight-cell stage but barely detectable at morula and blastocyst stages, suggesting that FIGLA might be a maternal effect gene. Recent studies in zebrafish and mice have highlighted the importance of non-coding small RNAs (microRNAs) as key regulatory molecules targeting maternal mRNAs for degradation during embryonic development. We hypothesized that FIGLA, as a maternal transcript, is regulated by microRNAs during early embryogenesis. Computational predictions identified a potential microRNA recognition element (MRE) for miR-212 in the 3' UTR of the bovine FIGLA mRNA. Bovine miR-212 is expressed in oocytes and tends to increase in four-cell and eight-cell stage embryos followed by a decline at morula and blastocyst stages. Transient transfection and reporter assays revealed that miR-212 represses the expression of FIGLA in a MRE dependent manner. In addition, ectopic expression of miR-212 mimic in bovine early embryos dramatically reduced the expression of FIGLA protein. Collectively, our results demonstrate that FIGLA is temporally regulated during bovine early embryogenesis and miR-212 is an important negative regulator of FIGLA during the maternal to zygotic transition in bovine embryos. PMID:24086699

Tripurani, Swamy K; Wee, Gabbine; Lee, Kyung-Bon; Smith, George W; Wang, Lei; Jianboyao

2013-09-27

66

The cold-induced basic helix-loop-helix transcription factor gene MdCIbHLH1 encodes an ICE-like protein in apple  

PubMed Central

Background Plant growth is greatly affected by low temperatures, and the expression of a number of genes is induced by cold stress. Although many genes in the cold signaling pathway have been identified in Arabidopsis, little is known about the transcription factors involved in the cold stress response in apple. Results Here, we show that the apple bHLH (basic helix-loop-helix) gene MdCIbHLH1 (Cold-Induced bHLH1), which encodes an ICE-like protein, was noticeably induced in response to cold stress. The MdCIbHLH1 protein specifically bound to the MYC recognition sequences in the AtCBF3 promoter, and MdCIbHLH1 overexpression enhanced cold tolerance in transgenic Arabidopsis. In addition, the MdCIbHLH1 protein bound to the promoters of MdCBF2 and favorably contributed to cold tolerance in transgenic apple plants by upregulating the expression of MdCBF2 through the CBF (C-repeat-binding factor) pathway. Our findings indicate that MdCIbHLH1 functions in stress tolerance in different species. For example, ectopic MdCIbHLH1 expression conferred enhanced chilling tolerance in transgenic tobacco. Finally, we observed that cold induces the degradation of the MdCIbHLH1 protein in apple and that this degradation was potentially mediated by ubiquitination and sumoylation. Conclusions Based on these findings, MdCIbHLH1 encodes a transcription factor that is important for the cold tolerance response in apple.

2012-01-01

67

SclR, a Basic Helix-Loop-Helix Transcription Factor, Regulates Hyphal Morphology and Promotes Sclerotial Formation in Aspergillus oryzae ? †  

PubMed Central

Most known basic-region helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors often involved in the control of growth and differentiation. Therefore, inappropriate expression of genes encoding bHLH proteins is frequently associated with developmental dysfunction. In our previously reported study, a novel bHLH protein-encoding gene (AO090011000215) of Aspergillus oryzae was identified. The gene-disrupted strain was found to produce dense conidia, but sparse sclerotia, relative to the parent strain. Here, to further analyze its function, we generated an overexpressing strain using the A. oryzae amyB gene promoter. Genetic overexpression led to a large number of initial hyphal aggregations and then the formation of mature sclerotia; it was therefore designated sclR (sclerotium regulator). At the same time, the sclR-overexpressing strain also displayed both delayed and decreased conidiation. Scanning electron microscopy indicated that the aerial hyphae of the sclR-overexpressing strain were extremely branched and intertwined with each other. In the generation of the SclR-enhanced green fluorescent protein (EGFP) expression strain, the SclR-EGFP protein fusion was conditionally detected in the nuclei. In addition, the loss of sclR function led to rapid protein degradation and cell lysis in dextrin-polypeptone-yeast extract liquid medium. Taken together, these observations indicate that SclR plays an important role in hyphal morphology, asexual conidiospore formation, and the promotion of sclerotial production, even retaining normal cell function, at least in submerged liquid culture.

Jin, Feng Jie; Takahashi, Tadashi; Matsushima, Ken-ichiro; Hara, Seiichi; Shinohara, Yasutomo; Maruyama, Jun-ichi; Kitamoto, Katsuhiko; Koyama, Yasuji

2011-01-01

68

SclR, a basic helix-loop-helix transcription factor, regulates hyphal morphology and promotes sclerotial formation in Aspergillus oryzae.  

PubMed

Most known basic-region helix-loop-helix (bHLH) proteins belong to a superfamily of transcription factors often involved in the control of growth and differentiation. Therefore, inappropriate expression of genes encoding bHLH proteins is frequently associated with developmental dysfunction. In our previously reported study, a novel bHLH protein-encoding gene (AO090011000215) of Aspergillus oryzae was identified. The gene-disrupted strain was found to produce dense conidia, but sparse sclerotia, relative to the parent strain. Here, to further analyze its function, we generated an overexpressing strain using the A. oryzae amyB gene promoter. Genetic overexpression led to a large number of initial hyphal aggregations and then the formation of mature sclerotia; it was therefore designated sclR (sclerotium regulator). At the same time, the sclR-overexpressing strain also displayed both delayed and decreased conidiation. Scanning electron microscopy indicated that the aerial hyphae of the sclR-overexpressing strain were extremely branched and intertwined with each other. In the generation of the SclR-enhanced green fluorescent protein (EGFP) expression strain, the SclR-EGFP protein fusion was conditionally detected in the nuclei. In addition, the loss of sclR function led to rapid protein degradation and cell lysis in dextrin-polypeptone-yeast extract liquid medium. Taken together, these observations indicate that SclR plays an important role in hyphal morphology, asexual conidiospore formation, and the promotion of sclerotial production, even retaining normal cell function, at least in submerged liquid culture. PMID:21551246

Jin, Feng Jie; Takahashi, Tadashi; Matsushima, Ken-ichiro; Hara, Seiichi; Shinohara, Yasutomo; Maruyama, Jun-ichi; Kitamoto, Katsuhiko; Koyama, Yasuji

2011-05-06

69

Obligate Heterodimerization of Arabidopsis Phytochromes C and E and Interaction with the PIF3 Basic Helix-Loop-Helix Transcription Factor[W  

PubMed Central

Phytochromes are dimeric chromoproteins that regulate plant responses to red (R) and far-red (FR) light. The Arabidopsis thaliana genome encodes five phytochrome apoproteins: type I phyA mediates responses to FR, and type II phyB–phyE mediate shade avoidance and classical R/FR-reversible responses. In this study, we describe the complete in vivo complement of homodimeric and heterodimeric type II phytochromes. Unexpectedly, phyC and phyE do not homodimerize and are present in seedlings only as heterodimers with phyB and phyD. Roles in light regulation of hypocotyl length, leaf area, and flowering time are demonstrated for heterodimeric phytochromes containing phyC or phyE. Heterodimers of phyC and chromophoreless phyB are inactive, indicating that phyC subunits require spectrally intact dimer partners to be active themselves. Consistent with the obligate heterodimerization of phyC and phyE, phyC is made unstable by removal of its phyB binding partner, and overexpression of phyE results in accumulation of phyE monomers. Following a pulse of red light, phyA, phyB, phyC, and phyD interact in vivo with the PHYTOCHROME INTERACTING FACTOR3 basic helix-loop-helix transcription factor, and this interaction is FR reversible. Therefore, most or all of the type I and type II phytochromes, including heterodimeric forms, appear to function through PIF-mediated pathways. These findings link an unanticipated diversity of plant R/FR photoreceptor structures to established phytochrome signaling mechanisms.

Clack, Ted; Shokry, Ahmed; Moffet, Matt; Liu, Peng; Faul, Michael; Sharrock, Robert A.

2009-01-01

70

Intermolecular recognition revealed by the complex structure of human CLOCK-BMAL1 basic helix-loop-helix domains with E-box DNA.  

PubMed

CLOCK (circadian locomotor output cycles kaput) and BMAL1 (brain and muscle ARNT-like 1) are both transcription factors of the circadian core loop in mammals. Recently published mouse CLOCK-BMAL1 bHLH (basic helix-loop-helix)-PAS (period-ARNT-single-minded) complex structure sheds light on the mechanism for heterodimer formation, but the structural details of the protein-DNA recognition mechanisms remain elusive. Here we have elucidated the crystal structure of human CLOCK-BMAL1 bHLH domains bound to a canonical E-box DNA. We demonstrate that CLOCK and BMAL1 bHLH domains can be mutually selected, and that hydrogen-bonding networks mediate their E-box recognition. We identified a hydrophobic contact between BMAL1 Ile80 and a flanking thymine nucleotide, suggesting that CLOCK-BMAL1 actually reads 7-bp DNA and not the previously believed 6-bp DNA. To find potential non-canonical E-boxes that could be recognized by CLOCK-BMAL1, we constructed systematic single-nucleotide mutations on the E-box and measured their relevant affinities. We defined two non-canonical E-box patterns with high affinities, AACGTGA and CATGTGA, in which the flanking A7-T7' base pair is indispensable for recognition. These results will help us to identify functional CLOCK-BMAL1-binding sites in vivo and to search for clock-controlled genes. Furthermore, we assessed the inhibitory role of potential phosphorylation sites in bHLH regions. We found that the phospho-mimicking mutation on BMAL1 Ser78 could efficiently block DNA binding as well as abolish normal circadian oscillation in cells. We propose that BMAL1 Ser78 should be a key residue mediating input signal-regulated transcriptional inhibition for external cues to entrain the circadian clock by kinase cascade. PMID:23229515

Wang, Zixi; Wu, Yaling; Li, Lanfen; Su, Xiao-Dong

2012-12-11

71

MicroRNA-212 Post-Transcriptionally Regulates Oocyte-Specific Basic-Helix-Loop-Helix Transcription Factor, Factor in the Germline Alpha (FIGLA), during Bovine Early Embryogenesis  

PubMed Central

Factor in the germline alpha (FIGLA) is an oocyte-specific basic helix-loop-helix transcription factor essential for primordial follicle formation and expression of many genes required for folliculogenesis, fertilization and early embryonic survival. Here we report the characterization of bovine FIGLA gene and its regulation during early embryogenesis. Bovine FIGLA mRNA expression is restricted to gonads and is detected in fetal ovaries harvested as early as 90 days of gestation. FIGLA mRNA and protein are abundant in germinal vesicle and metaphase II stage oocytes, as well as in embryos from pronuclear to eight-cell stage but barely detectable at morula and blastocyst stages, suggesting that FIGLA might be a maternal effect gene. Recent studies in zebrafish and mice have highlighted the importance of non-coding small RNAs (microRNAs) as key regulatory molecules targeting maternal mRNAs for degradation during embryonic development. We hypothesized that FIGLA, as a maternal transcript, is regulated by microRNAs during early embryogenesis. Computational predictions identified a potential microRNA recognition element (MRE) for miR-212 in the 3’ UTR of the bovine FIGLA mRNA. Bovine miR-212 is expressed in oocytes and tends to increase in four-cell and eight-cell stage embryos followed by a decline at morula and blastocyst stages. Transient transfection and reporter assays revealed that miR-212 represses the expression of FIGLA in a MRE dependent manner. In addition, ectopic expression of miR-212 mimic in bovine early embryos dramatically reduced the expression of FIGLA protein. Collectively, our results demonstrate that FIGLA is temporally regulated during bovine early embryogenesis and miR-212 is an important negative regulator of FIGLA during the maternal to zygotic transition in bovine embryos.

Tripurani, Swamy K.; Wee, Gabbine; Lee, Kyung-Bon; Smith, George W.; Wang, Lei; JianboYao

2013-01-01

72

Human Hand1 basic helix-loop-helix (bHLH) protein: extra-embryonic expression pattern, interaction partners and identification of its transcriptional repressor domains.  

PubMed Central

The basic helix-loop-helix (bHLH) transcription factor, Hand1, plays an important role in the development of the murine extra-embryonic trophoblast cell lineage. In the present study, we have analysed the expression of Hand1 in human extra-embryonic cell types and determined its binding specificity and transcriptional activity upon interaction with different class A bHLH factors. Northern blotting and in situ hybridization showed that Hand1 mRNA is specifically expressed in amnion cells at different stages of gestation. Accordingly, we demonstrate that the protein is exclusively produced in the amniotic epithelium in vivo and in purified amnion cells in vitro using a novel polyclonal Hand1 antiserum. Reverse transcriptase-PCR and immunohistochemical staining of blastocysts revealed the production of Hand1 mRNA and polypeptide in the trophectodermal cell layer. In the presence of E12/E47, Hand1 stimulated the transcription of luciferase reporters harbouring degenerate E-boxes, suggesting that E-proteins are potential dimerization partners in trophoblastic tumour and amnion cells. In contrast, Hand1 diminished E12/E47-dependent transcription of reporters containing perfect E-boxes by inhibiting the interaction of Hand1/E-protein heterodimers with the palindromic cognate sequence. Furthermore, we show that Hand1 down-regulated GAL-E12-dependent reporter expression, indicating that the protein can also act directly as a transcriptional repressor. Mutational analyses of GAL-Hand1 suggested that two protein regions located within its N-terminal portion mainly confer the repressing activity. In conclusion, human Hand1 may play an important role in the differentiation of the amniotic membrane and the pre-implanting trophoblast. Furthermore, the data suggest that Hand1 can act as a repressor by two independent mechanisms; sequestration of class A bHLH factors from E-boxes and inhibition of their transcriptional activity.

Knofler, Martin; Meinhardt, Gudrun; Bauer, Sandra; Loregger, Thomas; Vasicek, Richard; Bloor, Debra J; Kimber, Susan J; Husslein, Peter

2002-01-01

73

Functional Diversity of Human Basic Helix-Loop-Helix Transcription Factor TCF4 Isoforms Generated by Alternative 5? Exon Usage and Splicing  

PubMed Central

Background Transcription factor 4 (TCF4 alias ITF2, E2-2, ME2 or SEF2) is a ubiquitous class A basic helix-loop-helix protein that binds to E-box DNA sequences (CANNTG). While involved in the development and functioning of many different cell types, recent studies point to important roles for TCF4 in the nervous system. Specifically, human TCF4 gene is implicated in susceptibility to schizophrenia and TCF4 haploinsufficiency is the cause of the Pitt-Hopkins mental retardation syndrome. However, the structure, expression and coding potential of the human TCF4 gene have not been described in detail. Principal Findings In the present study we used human tissue samples to characterize human TCF4 gene structure and TCF4 expression at mRNA and protein level. We report that although widely expressed, human TCF4 mRNA expression is particularly high in the brain. We demonstrate that usage of numerous 5? exons of the human TCF4 gene potentially yields in TCF4 protein isoforms with 18 different N-termini. In addition, the diversity of isoforms is increased by alternative splicing of several internal exons. For functional characterization of TCF4 isoforms, we overexpressed individual isoforms in cultured human cells. Our analysis revealed that subcellular distribution of TCF4 isoforms is differentially regulated: Some isoforms contain a bipartite nuclear localization signal and are exclusively nuclear, whereas distribution of other isoforms relies on heterodimerization partners. Furthermore, the ability of different TCF4 isoforms to regulate E-box controlled reporter gene transcription is varied depending on whether one or both of the two TCF4 transcription activation domains are present in the protein. Both TCF4 activation domains are able to activate transcription independently, but act synergistically in combination. Conclusions Altogether, in this study we have described the inter-tissue variability of TCF4 expression in human and provided evidence about the functional diversity of the alternative TCF4 protein isoforms.

Sepp, Mari; Kannike, Kaja; Eesmaa, Ave; Urb, Mari; Timmusk, Tonis

2011-01-01

74

Id2 promotes the invasive growth of MCF7 and SKOV-3 cells by a novel mechanism independent of dimerization to basic helix-loop-helix factors  

Microsoft Academic Search

BACKGROUND: Inhibitor of differentiation 2 (Id2) is a critical factor for cell proliferation and differentiation in normal vertebrate development. Most of the biological function of Id2 has been ascribed to its helix-loop-helix motif. Overexpression of Id2 is frequently observed in various human tumors, but its role for invasion potential in tumor cells is dispute. We aimed to reveal the role

Yuanguang Meng; Chenglei Gu; Zhiqiang Wu; Yali Zhao; Yiling Si; Xiaobing Fu; Weidong Han

2009-01-01

75

Mutations in TCF4, encoding a class I basic helix-loop-helix transcription factor, are responsible for Pitt-Hopkins syndrome, a severe epileptic encephalopathy associated with autonomic dysfunction.  

PubMed

Pitt-Hopkins syndrome (PHS) is a rare syndromic encephalopathy characterized by daily bouts of hyperventilation and a facial gestalt. We report a 1.8-Mb de novo microdeletion on chromosome 18q21.1, identified by array-comparative genomic hybridization in one patient with PHS. We subsequently identified two de novo heterozygous missense mutations of a conserved amino acid in the basic region of the TCF4 gene in three additional subjects with PHS. These findings demonstrate that TCF4 anomalies are responsible for PHS and provide the first evidence of a human disorder related to class I basic helix-loop-helix transcription-factor defects (also known as "E proteins"). Moreover, our data may shed new light on the normal processes underlying autonomic nervous system development and maintenance of an appropriate ventilatory neuronal circuitry. PMID:17436254

Amiel, Jeanne; Rio, Marlene; de Pontual, Loic; Redon, Richard; Malan, Valerie; Boddaert, Nathalie; Plouin, Perrine; Carter, Nigel P; Lyonnet, Stanislas; Munnich, Arnold; Colleaux, Laurence

2007-03-23

76

Mutations in TCF4, Encoding a Class I Basic Helix-Loop-Helix Transcription Factor, Are Responsible for Pitt-Hopkins Syndrome, a Severe Epileptic Encephalopathy Associated with Autonomic Dysfunction  

PubMed Central

Pitt-Hopkins syndrome (PHS) is a rare syndromic encephalopathy characterized by daily bouts of hyperventilation and a facial gestalt. We report a 1.8-Mb de novo microdeletion on chromosome 18q21.1, identified by array–comparative genomic hybridization in one patient with PHS. We subsequently identified two de novo heterozygous missense mutations of a conserved amino acid in the basic region of the TCF4 gene in three additional subjects with PHS. These findings demonstrate that TCF4 anomalies are responsible for PHS and provide the first evidence of a human disorder related to class I basic helix-loop-helix transcription-factor defects (also known as “E proteins”). Moreover, our data may shed new light on the normal processes underlying autonomic nervous system development and maintenance of an appropriate ventilatory neuronal circuitry.

Amiel, Jeanne; Rio, Marlene; Pontual, Loic de; Redon, Richard; Malan, Valerie; Boddaert, Nathalie; Plouin, Perrine; Carter, Nigel P.; Lyonnet, Stanislas; Munnich, Arnold; Colleaux, Laurence

2007-01-01

77

Identification and characterization of a putative basic helix-loop-helix transcription factor involved in the early stage of conidiophore development in Aspergillus oryzae.  

PubMed

The helix-loop-helix (HLH) family of transcriptional factors is a key player in a wide range of developmental processes. HLH proteins form homo- and/or heterodimers with other HLH proteins and bind to E-box motifs. The regulation and functions of these proteins can be complex due to their bifunctional roles as activators and repressors of gene transcription. In this study, we isolated and characterized a novel predicted bHLH protein-encoding gene, AO090023000902, designated ecdR (early conidiophore development regulator), in Aspergillus oryzae. The ecdR gene disruptant produced very few conidia. Conversely, the overexpression of ecdR resulted in the formation of a large number of conidia at an early stage, suggesting that the EcdR protein is required for early asexual development. Additionally, when serially diluted conidia were spread-cultivated onto malt agar medium, we found that conidial number of the control strain depended on the cultivated conidium density, while the ecdR-overexpressing strain showed no significant change in conidiation. These phenotypes of ecdR-disruptant and ecdR-overexpressing strains are partially similar to those of the sclR-overexpressing strain and sclR-disruptant, respectively. Yeast two-hybrid assays and sclR, ecdR-double deletion experiment indicated that EcdR plays a major role in conidiation, and SclR represses this function by competitively interacting with EcdR in A. oryzae. PMID:22008745

Jin, Feng Jie; Nishida, Michiyo; Hara, Seiichi; Koyama, Yasuji

2011-10-10

78

The neurogenic basic helix-loop-helix transcription factor NeuroD6 enhances mitochondrial biogenesis and bioenergetics to confer tolerance of neuronal PC12-NeuroD6 cells to the mitochondrial stressor rotenone.  

PubMed

The fundamental question of how and which neuronal specific transcription factors tailor mitochondrial biogenesis and bioenergetics to the need of developing neuronal cells has remained largely unexplored. In this study, we report that the neurogenic basic helix-loop-helix transcription factor NeuroD6 possesses mitochondrial biogenic properties by amplifying the mitochondrial DNA content and TFAM expression levels, a key regulator for mitochondrial biogenesis. NeuroD6-mediated increase in mitochondrial biogenesis in the neuronal progenitor-like PC12-NEUROD6 cells is concomitant with enhanced mitochondrial bioenergetic functions, including increased expression levels of specific subunits of respiratory complexes of the electron transport chain, elevated mitochondrial membrane potential and ATP levels produced by oxidative phosphorylation. Thus, NeuroD6 augments the bioenergetic capacity of PC12-NEUROD6 cells to generate an energetic reserve, which confers tolerance to the mitochondrial stressor, rotenone. We found that NeuroD6 induces an adaptive bioenergetic response throughout rotenone treatment involving maintenance of the mitochondrial membrane potential and ATP levels in conjunction with preservation of the actin network. In conclusion, our results support the concept that NeuroD6 plays an integrative role in regulating and coordinating the onset of neuronal differentiation with acquisition of adequate mitochondrial mass and energetic capacity to ensure energy demanding events, such as cytoskeletal remodeling, plasmalemmal expansion, and growth cone formation. PMID:22814253

Baxter, Kristin Kathleen; Uittenbogaard, Martine; Chiaramello, Anne

2012-07-16

79

Caught Red-Handed: Rc Encodes a Basic Helix-Loop-Helix Protein Conditioning Red Pericarp in RiceW? 111111111111111111111111 100000000000000000000001 100001111000000001000001 100010000100000010100001 100100000010000010100001 101000000001000100010001 101000000001000100010001 101000000001001111111001 101000000001001000001001 100100000010001000001001 100010000100010000000101 100001111000010000000101 100000000000000000000001 111111111111111111111111  

PubMed Central

Rc is a domestication-related gene required for red pericarp in rice (Oryza sativa). The red grain color is ubiquitous among the wild ancestors of O. sativa, in which it is closely associated with seed shattering and dormancy. Rc encodes a basic helix-loop-helix (bHLH) protein that was fine-mapped to an 18.5-kb region on rice chromosome 7 using a cross between Oryza rufipogon (red pericarp) and O. sativa cv Jefferson (white pericarp). Sequencing of the alleles from both mapping parents as well as from two independent genetic stocks of Rc revealed that the dominant red allele differed from the recessive white allele by a 14-bp deletion within exon 6 that knocked out the bHLH domain of the protein. A premature stop codon was identified in the second mutant stock that had a light red pericarp. RT-PCR experiments confirmed that the Rc gene was expressed in both red- and white-grained rice but that a shortened transcript was present in white varieties. Phylogenetic analysis, supported by comparative mapping in rice and maize (Zea mays), showed that Rc, a positive regulator of proanthocyanidin, is orthologous with INTENSIFIER1, a negative regulator of anthocyanin production in maize, and is not in the same clade as rice bHLH anthocyanin regulators.

Sweeney, Megan T.; Thomson, Michael J.; Pfeil, Bernard E.; McCouch, Susan

2006-01-01

80

Overlapping Expression of Early B-Cell Factor and Basic Helix-Loop-Helix Proteins as a Mechanism To Dictate B-Lineage-Specific Activity of the ?5 Promoter  

PubMed Central

The basic helix-loop-helix (bHLH) transcription factors are a large group of proteins suggested to control key events in the development of B lymphocytes as well as of other cellular lineages. To examine how bHLH proteins activate a B-lineage-specific promoter, I investigated the ability of E47, E12, Heb, E2-2, and MyoD to activate the ?5 surrogate light chain promoter. Comparison of the functional capacity of the E2A-encoded E47 and E12 proteins indicated that even though both were able to activate the ?5 promoter and act in synergy with early B-cell factor (EBF), E47 displayed a higher functional activity than E12. An ability to act in synergy with EBF was also observed for Heb, E2-2, and MyoD, suggesting that these factors were functionally redundant in this regard. Mapping of functional domains in EBF and E47 revealed that the dimerization and DNA binding domains mediated the synergistic activity. Electrophoretic mobility shift assay analysis using the 5? part of the ?5 promoter revealed formation of template-dependent heteromeric complexes between EBF and E47, suggesting that the synergistic mechanism involves cooperative binding to DNA. These findings propose a unique molecular function for E47 and provide overlapping expression with EBF as a molecular mechanism to direct B-cell-specific target gene activation by bHLH proteins.

Sigvardsson, Mikael

2000-01-01

81

Backbone dynamics of a symmetric calmodulin dimer in complex with the calmodulin-binding domain of the basic-helix-loop-helix transcription factor SEF2-1/E2-2: a highly dynamic complex.  

PubMed

Calmodulin (CaM) interacts specifically as a dimer with some dimeric basic-Helix-Loop-Helix (bHLH) transcription factors via a novel high affinity binding mode. Here we report a study of the backbone dynamics by (15)N-spin relaxation on the CaM dimer in complex with a dimeric peptide that mimics the CaM binding region of the bHLH transcription factor SEF2-1. The relaxation data were measured at multiple magnetic fields, and analyzed in a model-free manner using in-house written software designed to detect nanosecond internal motion. Besides picosecond motions, all residues also experience internal motion with an effective correlation time of approximately 2.5 ns with squared order parameter (S(2)) of approximately 0.75. Hydrodynamic calculations suggest that this can be attributed to motions of the N- and C-terminal domains of the CaM dimer in the complex. Moreover, residues with significant exchange broadening are found. They are clustered in the CaM:SEF2-1mp binding interface, the CaM:CaM dimer interface, and in the flexible helix connecting the CaM N- and C-terminal domains, and have similar exchange times (approximately 50 micros), suggesting a cooperative mechanism probably caused by protein:protein interactions. The dynamic features presented here support the conclusion that the conformationally heterogeneous bHLH mimicking peptide trapped inside the CaM dimer exchanges between different binding sites on both nanosecond and microsecond timescales. Nature has thus found a way to specifically recognize a relatively ill-fitting target. This novel mode of target-specific binding, which neither belongs to lock-and-key nor induced-fit binding, is characterized by dimerization and continuous exchange between multiple flexible binding alternatives. PMID:15894636

Larsson, Göran; Schleucher, Jürgen; Onions, Jacqueline; Hermann, Stefan; Grundström, Thomas; Wijmenga, Sybren S

2005-05-13

82

Backbone Dynamics of a Symmetric Calmodulin Dimer in Complex with the Calmodulin-Binding Domain of the Basic-Helix-Loop-Helix Transcription Factor SEF2-1/E2-2: A Highly Dynamic Complex  

PubMed Central

Calmodulin (CaM) interacts specifically as a dimer with some dimeric basic-Helix-Loop-Helix (bHLH) transcription factors via a novel high affinity binding mode. Here we report a study of the backbone dynamics by 15N-spin relaxation on the CaM dimer in complex with a dimeric peptide that mimics the CaM binding region of the bHLH transcription factor SEF2-1. The relaxation data were measured at multiple magnetic fields, and analyzed in a model-free manner using in-house written software designed to detect nanosecond internal motion. Besides picosecond motions, all residues also experience internal motion with an effective correlation time of ?2.5 ns with squared order parameter (S2) of ?0.75. Hydrodynamic calculations suggest that this can be attributed to motions of the N- and C-terminal domains of the CaM dimer in the complex. Moreover, residues with significant exchange broadening are found. They are clustered in the CaM:SEF2-1mp binding interface, the CaM:CaM dimer interface, and in the flexible helix connecting the CaM N- and C-terminal domains, and have similar exchange times (?50 ?s), suggesting a cooperative mechanism probably caused by protein:protein interactions. The dynamic features presented here support the conclusion that the conformationally heterogeneous bHLH mimicking peptide trapped inside the CaM dimer exchanges between different binding sites on both nanosecond and microsecond timescales. Nature has thus found a way to specifically recognize a relatively ill-fitting target. This novel mode of target-specific binding, which neither belongs to lock-and-key nor induced-fit binding, is characterized by dimerization and continuous exchange between multiple flexible binding alternatives.

Larsson, Goran; Schleucher, Jurgen; Onions, Jacqueline; Hermann, Stefan; Grundstrom, Thomas; Wijmenga, Sybren S.

2005-01-01

83

The basic helix-loop-helix transcription factor CrMYC2 controls the jasmonate-responsive expression of the ORCA genes that regulate alkaloid biosynthesis in Catharanthus roseus.  

PubMed

Jasmonates are plant signalling molecules that play key roles in defence against insects and certain pathogens, among others by controlling the biosynthesis of protective secondary metabolites. In Catharanthus roseus, the AP2/ERF-domain transcription factor ORCA3 controls the jasmonate-responsive expression of several genes encoding enzymes involved in terpenoid indole alkaloid biosynthesis. ORCA3 gene expression is itself induced by jasmonate. The ORCA3 promoter contains an autonomous jasmonate-responsive element (JRE) composed of a quantitative sequence responsible for the high level of expression and a qualitative sequence that acts as an on/off switch in response to methyl-jasmonate (MeJA). Here, we identify the basic helix-loop-helix (bHLH) transcription factor CrMYC2 as the major activator of MeJA-responsive ORCA3 gene expression. The CrMYC2 gene is an immediate-early jasmonate-responsive gene. CrMYC2 binds to the qualitative sequence in the ORCA3 JRE in?vitro, and transactivates reporter gene expression via this sequence in transient assays. Knock-down of the CrMYC2 expression level via RNA interference caused a strong reduction in the level of MeJA-responsive ORCA3 mRNA accumulation. In addition, MeJA-responsive expression of the related transcription factor gene ORCA2 was significantly reduced. Our results show that MeJA-responsive expression of alkaloid biosynthesis genes in C. roseus is controlled by a transcription factor cascade consisting of the bHLH protein CrMYC2 regulating ORCA gene expression, and the AP2/ERF-domain transcription factors ORCA2 and ORCA3, which in turn regulate a subset of alkaloid biosynthesis genes. PMID:21401746

Zhang, Hongtao; Hedhili, Sabah; Montiel, Grégory; Zhang, Yanxia; Chatel, Guillaume; Pré, Martial; Gantet, Pascal; Memelink, Johan

2011-04-26

84

Helix-Loop-Helix Protein p8, a Transcriptional Regulator Required for Cardiomyocyte Hypertrophy and Cardiac Fibroblast Matrix Metalloprotease Induction  

Microsoft Academic Search

Cardiomyocyte hypertrophy and extracellular matrix remodeling, primarily mediated by inflammatory cytokine-stimulated cardiac fibroblasts, are critical cellular events in cardiac pathology. The molecular com- ponents governing these processes remain nebulous, and few genes have been linked to both hypertrophy and matrix remodeling. Here we show that p8, a small stress-inducible basic helix-loop-helix protein, is required for endothelin- and -adrenergic agonist-induced cardiomyocyte

Sandro Goruppi; Richard D. Patten; Thomas Force; John M. Kyriakis

2007-01-01

85

The helix-loop-helix extramacrochaetae protein is required for proper specification of many cell types in the Drosophila embryo.  

PubMed

The Drosophila Extramacrochaetae protein antagonizes the proneural function of the Achaete and Scute proteins in the generation of the adult fly sensory organs. Extra-macrochaetae sequesters these basic-region-helix-loop-helix transcription factors as heterodimers inefficient for binding to DNA. We show that, during embryonic development, the extramacrochaetae gene is expressed in complex patterns that comprise derivatives of the three embryonic layers. Expression of extramacrochaetae often precedes and accompanies morphogenetic movements. It also occurs at regions of specialized cell-cell contact and/or cell recognition, like the epidermal part of the muscle attachment sites and the differentiating CNS. The insufficiency of extramacrochaetae affects most tissues where it is expressed. The defects suggest faulty specification of different cell types and result in impairment of processes as diverse as cell proliferation and commitment, cell adhesion and cell recognition. If Extramacrochaetae participates in cell specification by dimerizing with basic-region-helix-loop-helix proteins, the variety of defects and tissues affected by the insufficiency of extramacrochaetae suggests that helix-loop-helix proteins are involved in many embryonic developmental processes. PMID:7956831

Cubas, P; Modolell, J; Ruiz-Gómez, M

1994-09-01

86

Expression of a chimeric helix-loop-helix gene, Id-SCL, in K562 human leukemic cells is associated with nuclear segmentation.  

PubMed Central

We have designed a chimeric gene, Id-SCL, in which the 3' helix-loop-helix encoding portion of the presumptive oncogene SCL/tal is joined to the 5' coding portion of Id, an inhibitory helix-loop-helix gene. The predicted protein product of this chimeric gene contains the helix-loop-helix dimerization domain of SCL/tal, but, lacking a basic DNA binding domain, is predicted to have the inhibitory function of the Id product. Expression of the Id-SCL fusion gene in stably transfected K562 cells reproducibly resulted in nuclear segmentation and depressed growth rates; both of these phenotypic effects demonstrated a dosage dependence on the levels of Id-SCL mRNA and protein expressed in the various clones. Electron microscopy of cells expressing high levels of Id-SCL mRNA showed a significant increase in cytoplasmic perinuclear thin filaments and diminution of marginal heterochromatin in the nuclei. No other changes in hematopoietic differentiation status were observed in association with Id-SCL expression. Expression of intact Id and SCL/tal genes, as well as deletion mutants of Id and SCL/tal, independently transfected into K562 cells, indicated that the nuclear segmentation effect is dependent on the presence of a protein possessing a helix-loop-helix domain but lacking a basic domain. Our studies suggest that the balance of transcriptional inhibitory and stimulatory helix-loop-helix proteins in cells may be important determinants of proliferation and of structural organization within cells. Images Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 Figure 11

Goldfarb, A. N.; Wolf, M. L.; Greenberg, J. M.

1992-01-01

87

Class A Helix-Loop-Helix Proteins Are Positive Regulators of Several Cyclin-dependent Kinase Inhibitors’ Promoter Activity and Negatively Affect Cell Growth  

Microsoft Academic Search

ABSTRACT The class A of basic helix-loop-helix (bHLH) proteins are ubiquitously expressed transcription factors playing a pivotal role in the regulation of cell growth and differentiation. We determined that enforced expression of all four different mammalian members of this family, E12, E47, E2-2, and HEB, suppresses the cell colony-forming efficiency of several cell lines. To gain insights into the mechanisms

Alfredo Pagliuca; Pasquale Gallo; Pasquale De Luca; Luigi Lani

88

Dimerization of Sterol Regulatory Element-Binding Protein 2 via the Helix-Loop-Helix-Leucine Zipper Domain Is a Prerequisite for Its Nuclear Localization Mediated by Importin  

Microsoft Academic Search

The sterol regulatory element-binding protein 2 (SREBP-2), a transcription factor of the basic helix-loop- helix-leucine zipper (bHLH-Zip) family, is synthesized in the form of a membrane-attached precursor mole- cule. When cells are deprived of sterols, a two-step proteolytic processing releases the transcriptionally active N-terminal segment of SREBP-2, thereby allowing it to enter the nucleus. In previous studies, we showed that

EMI NAGOSHI; YOSHIHIRO YONEDA

2001-01-01

89

Helix-loop-helix transcription factors mediate activation and repression of the p75LNGFR gene.  

PubMed Central

Sequence analysis of rat and human low-affinity nerve growth factor receptor p75LNGFR gene promoter regions revealed a single E-box cis-acting element, located upstream of the major transcription start sites. Deletion analysis of the E-box sequence demonstrated that it significantly contributes to p75LNGFR promoter activity. This E box has a dual function; it mediates either activation or repression of the p75LNGFR promoter activity, depending on the interacting transcription factors. We showed that the two isoforms of the class A basic helix-loop-helix (bHLH) transcription factor ME1 (ME1a and ME1b), the murine homolog of the human HEB transcription factor, specifically repress p75LNGFR promoter activity. This repression can be released by coexpression of the HLH Id2 transcriptional regulator. In vitro analyses demonstrated that ME1a forms a stable complex with the p75LNGFR E box and likely competes with activating E-box-binding proteins. By using ME1a-overexpressing PC12 cells, we showed that the endogenous p75LNGFR gene is a target of ME1a repression. Together, these data demonstrate that the p75LNGFR E box and the interacting bHLH transcription factors are involved in the regulation of p75LNGFR gene expression. These results also show that class A bHLH transcription factors can repress and Id-like negative regulators can stimulate gene expression.

Chiaramello, A; Neuman, K; Palm, K; Metsis, M; Neuman, T

1995-01-01

90

Identifying Novel Helix-Loop-Helix Genes in Caenorhabditis elegans through a Classroom Demonstration of Functional Genomics  

PubMed Central

A 14-week, undergraduate-level Genetics and Population Biology course at Morgan State University was modified to include a demonstration of functional genomics in the research laboratory. Students performed a rudimentary sequence analysis of the Caenorhabditis elegans genome and further characterized three sequences that were predicted to encode helix–loop–helix proteins. Students then used reverse transcription–polymerase chain reaction to determine which of the three genes is normally expressed in C. elegans. At the end of this laboratory activity, students were 1) to demonstrate a rudimentary knowledge of bioinformatics, including the ability to differentiate between “having” a gene and “expressing” a gene, and 2) to understand basic approaches to functional genomics, including one specific technique for assaying for gene expression. It was also anticipated that students would increase their skills at effectively communicating their research activities through written and/or oral presentation. This article describes the laboratory activity and the assessment of the effectiveness of the activity.

Griffin, Vernetta; McMiller, Tracee; Jones, Erika; Johnson, Casonya M.

2003-01-01

91

Suppression of Chondrogenesis by Id Helix-Loop-Helix Proteins in Murine Embryonic Orofacial Tissue  

PubMed Central

Inhibitors of differentiation (Id) proteins are helix-loop-helix (HLH) transcription factors lacking a DNA binding domain. Id proteins modulate cell proliferation, apoptosis, and differentiation in embryonic/fetal tissue. Perturbation of any of these processes in cells of the developing orofacial region results in orofacial anomalies. Chondrogenesis, a process integral to normal orofacial ontogenesis, is known to be modulated, in part, by Id proteins. In the present study, the mRNA and protein expression patterns of Id1, Id2, Id3 and Id4 were examined in developing murine orofacial tissue in vivo, as well as in murine embryonic maxillary mesenchymal cells in vitro. The functional role of Ids during chondrogenesis was also explored in vitro. Results reveal that cells derived from developing murine orofacial tissue: (1) express Id1, Id2, Id3 and Id4 mRNAs and proteins on each of gestational days 12-14, (2) express all four Id proteins in a developmentally regulated manner, (3) undergo chondrogenesis and express genes encoding various chondrogenic marker proteins (e.g. Runx2, Type X collagen, Sox9) when cultured under micromass conditions, and (4) can have their chondrogenic potential regulated via alteration of Id protein function through overexpression of a basic HLH factor. In summary, results from the current report reveal for the first time, the expression of all four Id proteins in cells derived from developing murine orofacial tissue, and demonstrate a functional role for the Ids in regulating the ability of these cells to undergo chondrogenesis.

Mukhopadhyay, Partha; Rezzoug, Francine; Webb, Cynthia L.; Pisano, M. Michele; Greene, Robert M.

2009-01-01

92

Common Regulation of Growth Arrest and Differentiation of Osteoblasts by Helix-Loop-Helix Factors  

PubMed Central

Cellular differentiation entails the coordination of cell cycle arrest and tissue-specific gene expression. We investigated the involvement of basic helix-loop-helix (bHLH) factors in differentiation of osteoblasts using the human osteoblastic cell line MG63. Serum starvation induced growth arrest at G1 phase, accompanied by expression of cyclin-dependent kinase inhibitor p21WAF1/Cip1. Reporter assays with the p21 gene promoter demonstrated that the combination of E2A (E12 or E47) and coactivator CBP was responsible for p21 induction independent of p53. Twist inhibited E2A-CBP-dependent activation of the exogenous and endogenous p21 promoters. Ids similarly inhibited the exogenously transfected p21 promoter; however less antagonistic effect on the endogenous p21 promoter was observed. Twist was predominantly present in nuclei in MG63 cells growing in complete medium, while it localized mainly in the cytoplasm after serum starvation. The fibroblast growth factor receptor 3 gene (FGFR3), which generates signals leading to differentiation of osteoblasts, was found to be controlled by the same transcriptional regulation as the p21 gene. E2A and Twist influenced alkaline phosphatase expression, a consensus marker of osteoblast differentiation. Expression of E2A and FGFR3 was seen at the location of osteoblast differentiation in the calvaria of mouse embryos, implicating bHLH molecules in physiological osteoblast differentiation. These results demonstrate that a common regulatory system is involved in at least two distinct steps in osteoblastic differentiation. Our results also provide the molecular basis of Saethre-Chotzen syndrome, caused by mutations of the TWIST and FGFR3 genes.

Funato, Noriko; Ohtani, Kiyoshi; Ohyama, Kimie; Kuroda, Takayuki; Nakamura, Masataka

2001-01-01

93

Multiple oligomeric states regulate the DNA binding of helix-loop-helix peptides.  

PubMed Central

To study the protein-protein interactions that allow Id, a negative regulator of cell differentiation, to inhibit the DNA-binding activities of MyoD and E47, we have synthesized peptides corresponding to the helix-loop-helix domains of MyoD, E47, and Id. We show that Id preferentially inhibits the sequence-specific DNA-binding activity of MyoD, a muscle-specific protein, as compared to E47, a more ubiquitous protein. The Id helix-loop-helix domain itself forms stable tetramers, and its inhibitory activity arises from the formation of a heterotetrameric structure with MyoD. The formation of this higher order complex provides a general mechanism by which inhibitory proteins can generate sufficient interaction free energy to overcome the large DNA-binding free energy of dimeric DNA-binding proteins. Images Fig. 2 Fig. 3

Fairman, R; Beran-Steed, R K; Anthony-Cahill, S J; Lear, J D; Stafford, W F; DeGrado, W F; Benfield, P A; Brenner, S L

1993-01-01

94

Regulation of TCF ETS-domain transcription factors by helix-loop-helix motifs  

Microsoft Academic Search

DNA binding by the ternary complex factor (TCF) subfamily of ETS-domain transcription factors is tightly regulated by intramolecular and intermolecu- lar interactions. The helix-loop-helix (HLH)-contain- ing Id proteins are trans-acting negative regulators of DNA binding by the TCFs. In the TCF, SAP-2\\/Net\\/ ERP, intramolecular inhibition of DNA binding is promoted by the cis-acting NID region that also con- tains an

Julie Stinson; Toshiaki Inoue; Paula Yates; Anne Clancy; John D. Norton; Andrew D. Sharrocks

2003-01-01

95

Transcription of the dominant-negative helix-loop-helix protein Id1 is regulated by a protein complex containing the immediate-early response gene Egr-1.  

PubMed Central

The expression of Id1, a helix-loop-helix protein which inhibits the activity of basic helix-loop-helix transcription factors, is down-regulated during cellular differentiation and cell cycle withdrawal both in tissue culture models and in mouse embryos. In order to study the mechanism of control of Idl expression, we have isolated a 210-bp enhancer element in the upstream region of the Id1 gene whose activity recapitulates Id1 expression in C2C12 muscle cells and C3H10T1/2 fibroblasts: i.e., this element is active in proliferating cells in the presence of serum and completely inactivated upon mitogen depletion, cell cycle withdrawal, and (in the case of C2C12) induced myoblast differentiation. Using linker-scanning mutations and site-directed mutagenesis in transient transfection experiments, we have identified two functional elements within the 210-bp enhancer which are required for proper serum responsiveness. One element (A) contains a consensus Egr-1 binding site and additional flanking sequences required for optimal activity, and the other element (B) fits no known consensus. Gel shift experiments demonstrate that the protein complex binding to the A site contains Egr-1 and other proteins. This complex as well as a protein complex that binds to the B site is lost within 24 h of serum depletion, correlating with the down-regulation of Id1 expression. On the basis of these findings, we propose that the regulation of the Id1 response to serum is mediated in part by the early response gene Egr-1 and as such provides a signaling link between the early-growth-response transcription factors and dominant-negative helix-loop-helix proteins.

Tournay, O; Benezra, R

1996-01-01

96

Decoding Hematopoietic Specificity in the Helix-Loop-Helix Domain of the Transcription Factor SCL/Tal-1  

PubMed Central

The helix-loop-helix (HLH) domain is employed by many transcription factors that control cell fate choice in multiple developmental settings. Previously, we demonstrated that the HLH domain of the class II basic HLH (bHLH) protein SCL/Tal-1 is critical for hematopoietic specification. We have now identified residues in this domain that are essential for restoring hematopoietic development to SCL?/? embryonic stem cells and sufficient to convert a muscle-specific HLH domain to one able to rescue hematopoiesis. Most of these critical residues are distributed in the loop of SCL, with one in helix 2. This is in contrast to the case for MyoD, the prototype of class II bHLH proteins, where the loop seems to serve mainly as a linker between the two helices. Among the identified residues, some promote heterodimerization with the bHLH partners of SCL (E12/E47), while others, unimportant for this property, are still crucial for the biological function of SCL. Importantly, the residue in helix 2 specifically promotes interaction with a known partner of SCL, the LIM-only protein LMO2, a finding that strengthens genetic evidence that these proteins interact. Our data highlight the functional complexity of bHLH proteins, provide mechanistic insight into SCL function, and strongly support the existence of an active SCL/LMO2-containing multiprotein complex in early hematopoietic cells.

Schlaeger, Thorsten M.; Schuh, Anna; Flitter, Simon; Fisher, Andreas; Mikkola, Hanna; Orkin, Stuart H.; Vyas, Paresh; Porcher, Catherine

2004-01-01

97

Role of Helix-Loop-Helix Proteins during Differentiation of Erythroid Cells ?  

PubMed Central

Helix-loop-helix (HLH) proteins play a profound role in the process of development and cellular differentiation. Among the HLH proteins expressed in differentiating erythroid cells are the ubiquitous proteins Myc, USF1, USF2, and TFII-I, as well as the hematopoiesis-specific transcription factor Tal1/SCL. All of these HLH proteins exhibit distinct functions during the differentiation of erythroid cells. For example, Myc stimulates the proliferation of erythroid progenitor cells, while the USF proteins and Tal1 regulate genes that specify the differentiated phenotype. This minireview summarizes the known activities of Myc, USF, TFII-I, and Tal11/SCL and discusses how they may function sequentially, cooperatively, or antagonistically in regulating expression programs during the differentiation of erythroid cells.

Anantharaman, Archana; Lin, I-Ju; Barrow, Joeva; Liang, Shermi Y.; Masannat, Jude; Strouboulis, John; Huang, Suming; Bungert, Jorg

2011-01-01

98

Regulation of TCF ETS-domain transcription factors by helix-loop-helix motifs  

PubMed Central

DNA binding by the ternary complex factor (TCF) subfamily of ETS-domain transcription factors is tightly regulated by intramolecular and intermolecular interactions. The helix–loop–helix (HLH)-containing Id proteins are trans-acting negative regulators of DNA binding by the TCFs. In the TCF, SAP-2/Net/ERP, intramolecular inhibition of DNA binding is promoted by the cis-acting NID region that also contains an HLH-like motif. The NID also acts as a transcriptional repression domain. Here, we have studied the role of HLH motifs in regulating DNA binding and transcription by the TCF protein SAP-1 and how Cdk-mediated phosphorylation affects the inhibitory activity of the Id proteins towards the TCFs. We demonstrate that the NID region of SAP-1 is an autoinhibitory motif that acts to inhibit DNA binding and also functions as a transcription repression domain. This region can be functionally replaced by fusion of Id proteins to SAP-1, whereby the Id moiety then acts to repress DNA binding in cis. Phosphorylation of the Ids by cyclin–Cdk complexes results in reduction in protein–protein interactions between the Ids and TCFs and relief of their DNA-binding inhibitory activity. In revealing distinct mechanisms through which HLH motifs modulate the activity of TCFs, our results therefore provide further insight into the role of HLH motifs in regulating TCF function and how the inhibitory properties of the trans-acting Id HLH proteins are themselves regulated by phosphorylation.

Stinson, Julie; Inoue, Toshiaki; Yates, Paula; Clancy, Anne; Norton, John D.; Sharrocks, Andrew D.

2003-01-01

99

A novel conotoxin framework with a helix-loop-helix (Cs alpha/alpha) fold.  

PubMed

Venomous predatory animals, such as snakes, spiders, scorpions, sea anemones, and cone snails, produce a variety of highly stable cystine-constrained peptide scaffolds as part of their neurochemical strategy for capturing prey. Here we report a new family of four-cystine, three-loop conotoxins (designated framework 14). Three peptides of this family (flf14a-c) were isolated from the venom of Conus floridanus floridensis, and one (vil14a) was isolated from the venom of Conus villepinii, two worm-hunting Western Atlantic cone snail species. The primary structure for these peptides was determined using Edman degradation sequencing, and their cystine pairing was assessed by limited hydrolysis with a combination of CNBr and chymotrypsin under nonreducing, nonalkylating conditions in combination with MALDI-TOF MS analysis of the resulting peptidic fragments. CD spectra and nanoNMR spectroscopy of these conotoxins directly isolated from the cone snails revealed a highly helical secondary structure for the four conotoxins. Sequence-specific nanoNMR analysis at room temperature revealed a well-defined helix-loop-helix tertiary structure that resembles that of the Cs alpha/alpha scorpion toxins kappa-hefutoxin, kappa-KTx1.3, and Om-toxins, which adopt a stable three-dimensional fold where the two alpha-helices are linked by the two disulfide bridges. One of these conotoxins (vil14a) has a Lys/Tyr dyad, separated by approximately 6A, which is a conserved structural feature in K(+) channel blockers. The presence of this framework in scorpions and in cone snails indicates a common molecular imprint in the venom of apparently unrelated predatory animals and suggests a common ancestral genetic origin. PMID:16331958

Möller, Carolina; Rahmankhah, Sanaz; Lauer-Fields, Janelle; Bubis, Jose; Fields, Gregg B; Marí, Frank

2005-12-13

100

The Helix-Loop-Helix Factors Id3 and E47 are Novel Regulators of Adiponectin  

PubMed Central

Adiponectin is an adipocyte-derived cytokine with beneficial effects on insulin sensitivity and the development of atherosclerosis. Id3 is a helix-loop-helix (HLH) factor that binds to E-proteins such as E47 and inhibits their binding to DNA. While the bHLH factor SREBP-1c is a known activator of adiponectin transcription, this study provides the first evidence of a role for Id3 and E47 in adiponectin expression. Decreased Id3 in differentiating adipocytes correlates with increased adiponectin expression and forced expression of Id3 inhibits adiponectin expression. Moreover, Id3 null mice have increased adiponectin expression in visceral fat tissue and in serum. We demonstrate that E47 potentiates SREBP-1c-mediated adiponectin promoter activation and that Id3 can dose-dependently inhibit this action via interaction with E47. Mutation of a consensus E47 binding site results in nearly complete loss of promoter activation. Further, we demonstrate E47 binding to the endogenous adiponectin promoter both in vitro and in vivo by ChIP analysis. Binding is not detected in undifferentiated cells which express Id3 but peaks during differentiation in parallel with Id3 decline. This promoter binding can be completely abolished by the overexpression of Id3 and is enhanced in adipose tissue null for Id3. These data establish Id3 and E47 as novel regulators of SREBP-1c-mediated adiponectin expression in differentiating adipocytes and provide evidence that Id3 regulates adiponectin expression in vivo.

Doran, Amanda C.; Meller, Nahum; Cutchins, Alexis; Deliri, Hamid; Slayton, R. Parker; Oldham, Stephanie N.; Kim, Jae B.; Keller, Susanna R.; McNamara, Coleen A.

2009-01-01

101

Molecular cloning of ID4, a novel dominant negative helix-loop-helix human gene on chromosome 6p21.3-p22  

SciTech Connect

Transcription factors containing a basic helix-loop-helix (bHLH) motif regulate the expression of tissue-specific genes in a number of mammalian and insect systems. DNA-binding activity of the bHLH proteins is dependent upon formation of homo- and/or heterodimers. Dominant negative HLH proteins (Id-related genes) also contain the HLH-dimerization domain but lack the DNA-binding basic domain. Consequently, Id proteins inhibit binding to DNA and transcriptional transactivation by heterodimerization with bHLH proteins. The authors report here the cDNA sequence of a novel human HLH gene (HGMW-approved symbol ID4) that lacks the basic domain. ID4 is differentially expressed in adult organs in four mRNA molecules, which are presumably a result of differential splicing and/or alternative usage of the polyadenylation sites. Transfection experiments indicated that enforced expression of Id-4H protein inhibits the trans-activation of the muscle creatine kinase E-box enhancer by MyoD. Finally, the authors localized the ID4 gene to the chromosome 6p21-p22 region. 18 refs., 4 figs.

Pagliuca, A.; Bartoli, P.C.; Saccone, S. [Universita Federico II, Naples (Italy)] [and others

1995-05-01

102

Mutually exclusive expression of a helix-loop-helix gene and N-myc in human neuroblastomas and in normal development.  

PubMed Central

We have isolated a novel human gene encoding a helix-loop-helix (HLH) protein by molecularly cloning chromosome 1p36-specific CpG islands. The gene termed heir-1 was localized to the neuroblastoma consensus deletion at 1p36.2-p36.12. Its predicted protein is 95.8% identical to the mouse HLH462 protein and has clear homology to the mouse Id and Drosophila emc proteins. Heir-1 does not encode a basic DNA binding domain as found in basic HLH proteins. The gene is expressed specifically at high abundance in adult lung, kidney and adrenal medulla, but not in adult brain. Despite prominent heir-1 expression in adrenal medulla, which is a prime target for neuroblastomas, 10 out of 12 neuroblastoma-derived cell lines revealed very low levels of heir-1 mRNA. Low heir-1 expression was generally found in tumor cell lines with N-myc overexpression, whereas the two cell lines displaying high heir-1 levels did not overexpress N-myc. Mutually exclusive expression of both genes was also found by in situ hybridization in developing mouse tissues, particularly in the forebrain neuroectoderm. We conclude that heir-1 expression is reduced specifically in the majority of neuroblastomas and suggest an inverse correlation between heir-1 and N-myc expression in neuroblastoma tumors and in embryonic development. Images

Ellmeier, W; Aguzzi, A; Kleiner, E; Kurzbauer, R; Weith, A

1992-01-01

103

Disruption of alpha beta but not of gamma delta T cell development by overexpression of the helix-loop-helix protein Id3 in committed T cell progenitors.  

PubMed Central

Enforced expression of Id3, which has the capacity to inhibit many basic helix-loop-helix (bHLH) transcription factors, in human CD34(+) hematopoietic progenitor cells that have not undergone T cell receptor (TCR) gene rearrangements inhibits development of the transduced cells into TCRalpha beta and gamma delta cells in a fetal thymic organ culture (FTOC). Here we document that overexpression of Id3, in progenitors that have initiated TCR gene rearrangements (pre-T cells), inhibits development into TCRalpha beta but not into TCRgamma delta T cells. Furthermore, Id3 impedes expression of recombination activating genes and downregulates pre-Talpha mRNA. These observations suggest possible mechanisms by which Id3 overexpression can differentially affect development of pre-T cells into TCRalpha beta and gamma delta cells. We also observed that cell surface CD4(-)CD8(-)CD3(-) cells with rearranged TCR genes developed from Id3-transduced but not from control-transduced pre-T cells in an FTOC. These cells had properties of both natural killer (NK) and pre-T cells. These findings suggest that bHLH factors are required to control T cell development after the T/NK developmental checkpoint.

Blom, B; Heemskerk, M H; Verschuren, M C; van Dongen, J J; Stegmann, A P; Bakker, A Q; Couwenberg, F; Res, P C; Spits, H

1999-01-01

104

Inhibition of T Cell and Promotion of Natural Killer Cell Development by the Dominant Negative Helix Loop Helix Factor Id3  

PubMed Central

Bipotential T/natural killer (NK) progenitor cells are present in the human thymus. Despite their bipotential capacity, these progenitors develop predominantly to T cells in the thymus. The mechanisms controlling this developmental choice are unknown. Here we present evidence that a member(s) of the family of basic helix loop helix (bHLH) transcription factors determines lineage specification of NK/T cell progenitors. The natural dominant negative HLH factor Id3, which blocks transcriptional activity of a number of known bHLH factors, was expressed in CD34+ progenitor cells by retrovirus-mediated gene transfer. Constitutive expression of Id3 completely blocks development of CD34+ cells into T cells in a fetal thymic organ culture (FTOC). In contrast, development into NK cells in an FTOC is enhanced. Thus, the activity of a bHLH transcription factor is necessary for T lineage differentiation of bipotential precursors, in the absence of which a default pathway leading to NK cell development is chosen. Our results identify a molecular switch for lineage specification in early lymphoid precursors of humans.

Heemskerk, Mirjam H.M.; Blom, Bianca; Nolan, Garry; Stegmann, Alexander P.A.; Bakker, Arjen Q.; Weijer, Kees; Res, Pieter C.M.; Spits, Hergen

1997-01-01

105

The Basic Helix-Loop-Helix Factor Hand2 Regulates Autonomic Nervous System Development  

PubMed Central

Mammalian autonomic nervous system (ANS) development requires the combinatorial action of a number of transcription factors, which include Mash1, Phox2b and GATA3. Here we show that the bHLH transcription factor, Hand2 (dHAND), is expressed concurrently with Mash1 during sympathetic nervous system (SNS) development and that the expression of Hand2 is not dependent on Mash1. This suggests that these two bHLH factors work in parallel during SNS development. We also show that ectopic expression of Hand2 activates the neuronal program and promotes the acquisition of a phenotype corresponding to peripheral neurons including neurons of the SNS lineage in P19 embryonic carcinoma cells. We propose that Hand2 works in parallel with other members of the transcriptional network to regulate ANS developmental but can ectopically activate the program by a cross-regulatory mechanism that includes the activation of Mash1. We show that this function is dependent on its interaction with the histone acetyltransferase p300/CBP, indicating that Hand2 functions to promote ANS development as part of larger transcriptional complex.

Morikawa, Yuka; Dai, Yan-Shan; Hao, Jianming; Bonin, Christopher; Hwang, Sunny; Cserjesi, Peter

2008-01-01

106

The basic helix-loop-helix transcription factor scleraxis regulates fibroblast collagen synthesis.  

PubMed

The transcription factor scleraxis has been implicated in regulating the development of collagen-rich tissues such as tendons and cardiac valves, but its role in general collagen synthesis in the heart is unknown. Scleraxis expression in cardiac fibroblasts was examined, and its ability to regulate gene expression of collagen I alpha 2, the predominant cardiac collagen isoform, was assayed. Using real-time PCR, we demonstrate here that scleraxis mRNA is up-regulated by the profibrotic agonist TGF-beta(1) in rat cardiac myofibroblasts, and that phenoconversion of fibroblasts to myofibroblasts similarly increases scleraxis expression. Over-expression of scleraxis in NIH-3T3 or primary rat cardiac fibroblasts by adenoviral gene delivery is sufficient to significantly increase collagen I alpha 2 gene expression. Using luciferase reporter assays, we demonstrate that scleraxis transactivates the human collagen I alpha 2 promoter in a DNA- and protein-binding dependent manner. Intriguingly, examination of infarcted rat hearts reveals a nearly four-fold increase in scleraxis expression in the infarct scar, but not in non-infarcted tissue. These data support a novel and previously unknown role for scleraxis in the regulation of collagen gene expression in the heart, including in post-infarct scar formation. PMID:19362560

Espira, Leon; Lamoureux, Lise; Jones, Stephen C; Gerard, Robert D; Dixon, Ian M C; Czubryt, Michael P

2009-04-10

107

The basic helix–loop–helix transcription factor scleraxis regulates fibroblast collagen synthesis  

Microsoft Academic Search

The transcription factor scleraxis has been implicated in regulating the development of collagen-rich tissues such as tendons and cardiac valves, but its role in general collagen synthesis in the heart is unknown. Scleraxis expression in cardiac fibroblasts was examined, and its ability to regulate gene expression of collagen I?2, the predominant cardiac collagen isoform, was assayed. Using real-time PCR, we

Leon Espira; Lise Lamoureux; Stephen C. Jones; Robert D. Gerard; Ian M. C. Dixon; Michael P. Czubryt

2009-01-01

108

Seven Genes of the Enhancer of Split Complex of Drosophila Melanogaster Encode Helix-Loop-Helix Proteins  

PubMed Central

Enhancer of split [E(spl)] is one of the neurogenic loci of Drosophila and, as such, is required for normal segregation of neural and epidermal cell progenitors. Genetic observations indicate that the E(spl) locus is in fact a gene complex comprising a cluster of related genes and that other genes of the region are also required for normal early neurogenesis. Three of the genes of the complex were known to encode helix-loop-helix (HLH) proteins and to be transcribed in nearly identical patterns. Here, we show that four other genes in the vicinity also encode HLH proteins and, during neuroblast segregation, three of them are expressed in the same pattern. We show by germ-line transformation that these three genes are also necessary to allow epidermal development of the neuroectodermal cells.

Knust, E.; Schrons, H.; Grawe, F.; Campos-Ortega, J. A.

1992-01-01

109

Helix-loop-helix proteins LYL1 and E2a form heterodimeric complexes with distinctive DNA-binding properties in hematolymphoid cells.  

PubMed Central

LYL1 is a basic helix-loop-helix (HLH) protein that was originally discovered because of its translocation into the beta T-cell receptor locus in an acute lymphoblastic leukemia. LYL1 is expressed in many hematolymphoid cells, with the notable exceptions of thymocytes and T cells. Using the yeast two-hybrid system to screen a cDNA library constructed from B cells, we identified the E-box-binding proteins E12 and E47 as potential lymphoid dimerization partners for LYL1. The interaction of LYL1 with E2a proteins was further characterized in vitro and shown to require the HLH motifs of both proteins. Immunoprecipitation analyses showed that in T-ALL and other cell lines, endogenous LYL1 exists in a complex with E2a proteins. A preferred DNA-binding sequence, 5'-AACAGATG(T/g)T-3', for the LYL1-E2a heterodimer was determined by PCR-assisted site selection. Endogenous protein complexes containing both LYL1 and E2a bound this sequence in various LYL1-expressing cell lines and could distinguish between the LYL1 consensus and muE2 sites. These data demonstrate that E2a proteins serve as dimerization partners for the basic HLH protein LYL1 to form complexes with distinctive DNA-binding properties and support the hypothesis that the leukemic properties of the LYL1 and TAL subfamily of HLH proteins could be mediated by recognition of a common set of target genes as heterodimeric complexes with class I HLH proteins.

Miyamoto, A; Cui, X; Naumovski, L; Cleary, M L

1996-01-01

110

BETA3, a novel helix-loop-helix protein, can act as a negative regulator of BETA2 and MyoD-responsive genes.  

PubMed Central

Using degenerate PCR cloning we have identified a novel basic helix-loop-helix (bHLH) transcription factor, BETA3, from a hamster insulin tumor (HIT) cell cDNA library. Sequence analysis revealed that this factor belongs to the class B bHLH family and has the highest degree of homology with another bHLH transcription factor recently isolated in our laboratory, BETA2 (neuroD) (J. E. Lee, S. M. Hollenberg, L. Snider, D. L. Turner, N. Lipnick, and H. Weintraub, Science 268:836-844, 1995; F. J. Naya, C. M. M. Stellrecht, and M.-J. Tsai, Genes Dev. 8:1009-1019, 1995). BETA2 is a brain- and pancreatic-islet-specific bHLH transcription factor and is largely responsible for the tissue-specific expression of the insulin gene. BETA3 was found to be tissue restricted, with the highest levels of expression in HIT, lung, kidney, and brain cells. Surprisingly, despite the homology between BETA2 and BETA3 and its intact basic region, BETA3 is unable to bind the insulin E box in bandshift analysis as a homodimer or as a heterodimer with the class A bHLH factors E12, E47, or BETA1. Instead, BETA3 inhibited both the E47 homodimer and the E47/BETA2 heterodimer binding to the insulin E box. In addition, BETA3 greatly repressed the BETA2/E47 induction of the insulin enhancer in HIT cells as well as the MyoD/E47 induction of a muscle-specific E box in the myoblast cell line C2C12. In contrast, expression of BETA3 had no significant effect on the GAL4-VP16 transcriptional activity. Immunoprecipitation analysis demonstrates that the mechanism of repression is via direct protein-protein interaction, presumably by heterodimerization between BETA3 and class A bHLH factors.

Peyton, M; Stellrecht, C M; Naya, F J; Huang, H P; Samora, P J; Tsai, M J

1996-01-01

111

The expression and roles of inhibitor of DNA binding helix-loop-helix proteins in the developing and adult mouse retina.  

PubMed

Inhibitor of DNA binding (Id) proteins bind to and inhibit the function of basic helix-loop-helix (bHLH) transcription factors including those that regulate retinal development. However, little is known about the role of Id proteins in the growth and differentiation of the retina during development. The purpose of this study is to observe the expression of Id proteins in the developing and adult mouse retinas as the first step in investigating the functions of Id family members in the eye. The expression of Id1-4 was examined by real-time PCR, Western blot, and immunohistochemistry in wild-type and Id1/Id3 double-knockout mice. Id1-4 genes and proteins showed high expression levels in the retina at embryonic and early postnatal stages, whereas declined in the adult. Expression of Id proteins was observed in the inner neuroblastic layer (NBL) at embryonic (E) day 13.5 through 16.5. Id4 expression began at E18.5. By E18.5 and postnatal day 1, the expression of Id1-4 exhibited distinct yet overlapping patterns in the ganglion cell layer and inner part of NBL. In the adult, Ids were expressed in retinal ganglion cells, amacrine cells, bipolar cells, and horizontal cells. No Id expression was found in Müller cells. Id1 and Id3 double-knockout mice (Id1(-/-)/Id3(-/-)) showed smaller retinal size compared to wild-type or heterozygous littermates. However, histological analyses in Id1 and Id3 single-knockout retinas revealed no obvious defects in developmental phenotype. Our results indicate that the expression of the Id family may play an important role in regulating retinal progenitor cell proliferation and differentiation. PMID:21145943

Du, Y; Yip, H K

2010-12-09

112

The helix-loop-helix transcription factor SEF-2 regulates the activity of a novel initiator element in the promoter of the human somatostatin receptor II gene.  

PubMed Central

The effects of somatostatin hormones are mediated by a family of five different seven-helix transmembrane spanning receptors (SSTR1-5). The expression of the five different SSTR subtypes displays a complex temporal- and tissue-specific pattern. To investigate the molecular mechanisms controlling the different expression patterns of the SSTRs, we cloned the 5'-flanking region of the human SSTR2 gene. Characterization of the SSTR2 promoter resulted in the identification of a novel initiator element (SSTR2inr). Transcriptional activity of the SSTR2inr is dependent on the presence of a binding site (E-box) for basic helix-loop-helix (bHLH) transcription factors. By screening a mouse brain cDNA expression library we isolated a cDNA coding for the bHLH transcription factor SEF-2. SEF-2 binds to the E-box present in the SSTR2inr, both in vitro and in vivo and activates transcription from the SSTR2inr. A single point mutation within the E-box eliminates binding of SEF-2 and results in a complete loss of transcriptional activity of the SSTR2inr. Furthermore, DNA binding studies demonstrate that the basal transcription factor TFIIB can be tethered to the SSTR2inr through physical interaction with SEF-2. In summary, the SSTR2inr represents a novel type of initiator element that confers gene expression in the absence of a TATA-box or binding sites for other known initiator factors, like YY-1 or USF. Images

Pscherer, A; Dorflinger, U; Kirfel, J; Gawlas, K; Ruschoff, J; Buettner, R; Schule, R

1996-01-01

113

HEB, a helix-loop-helix protein related to E2A and ITF2 that can modulate the DNA-binding ability of myogenic regulatory factors.  

PubMed

Proteins containing the basic-helix-loop-helix (B-HLH) domain have been shown to be important in regulating cellular differentiation. We have isolated a cDNA for a human B-HLH factor, denoted HEB, that shares nearly complete identity in the B-HLH domain with the immunoglobulin enhancer binding proteins encoded by the E2A and ITF2 genes (E proteins). Functional characterization of the protein expressed from this cDNA indicates that HEB is a third member of the E-protein class of B-HLH factors. HEB mRNA was found to be expressed in several tissues and cell types, including skeletal muscle, thymus, and a B-cell line. HEB, ITF2, and the E12 product of the E2A gene all bound to a similar spectrum of E-box sequences as homo-oligomers. All three factors also formed hetero-oligomers with myogenin, and the DNA-binding specificity and binding off-rates (dissociation rates) were modulated after hetero-oligomerization. Both homo- and hetero-oligomers of these proteins were able to distinguish between very closely related E-box sequences. In addition, HEB was shown to form hetero-oligomers with the E12 and ITF2 proteins. Finally, HEB was able to activate gene expression. These data demonstrate that HEB shares characteristics with other E proteins and show that HEB can interact with members of both the myogenic regulatory class and the E-protein class of B-HLH factors. HEB is therefore likely to play an important role in regulating lineage-specific gene expression. PMID:1312219

Hu, J S; Olson, E N; Kingston, R E

1992-03-01

114

Id helix-loop-helix proteins inhibit nucleoprotein complex formation by the TCF ETS-domain transcription factors.  

PubMed Central

The Id subfamily of helix-loop-helix (HLH) proteins plays a fundamental role in the regulation of cellular proliferation and differentiation. Id proteins are thought to inhibit differentiation mainly through interaction with other HLH proteins and by blocking their DNA-binding activity. Members of the ternary complex factor (TCF) subfamily of ETS-domain proteins have key functions in regulating immediate-early gene expression in response to mitogenic stimulation. TCFs form DNA-bound complexes with the serum response factor (SRF) and are direct targets of MAP kinase (MAPK) signal transduction cascades. In this study we demonstrate functional interactions between Id proteins and TCFs. Ids bind to the ETS DNA-binding domain and disrupt the formation of DNA-bound complexes between TCFs and SRF on the c-fos serum response element (SRE). Inhibition occurs by disrupting protein-DNA interactions with the TCF component of this complex. In vivo, the Id proteins cause down-regulation of the transcriptional activity mediated by the TCFs and thereby block MAPK signalling to SREs. Therefore, our results demonstrate a novel facet of Id function in the coordination of mitogenic signalling and cell cycle entry.

Yates, P R; Atherton, G T; Deed, R W; Norton, J D; Sharrocks, A D

1999-01-01

115

Molecular cloning and chromosomal localization of the murine homolog of the human helix-loop-helix gene SCL.  

PubMed Central

The human SCL gene is a member of the family of genes that encode the helix-loop-helix (HLH) class of DNA-binding proteins. A murine SCL cDNA was isolated from a normal macrophage cDNA library by using HLH-specific oligonucleotides as hybridization probes. The coding region is 987 base pairs and encodes a predicted protein of 34 kDa. The nucleotide sequence of the coding region shows 88% identity to the human SCL gene, and the amino acid sequence is 94% identical. The HLH motif and upstream hydrophilic region are entirely conserved in the murine and human proteins. The identity between the mouse and human sequences was less marked in the 5' and 3' untranslated regions. Two murine SCL transcripts that differ in the 3' noncoding region have been detected in fetal liver and various cell lines. Variation was also observed in the 5' untranslated region. Interestingly, immediately downstream of the protein-termination codon, both the human SCL sequence and the murine homolog share an E-box element--the suggested target site for DNA binding of HLH proteins. The murine SCL homolog was mapped to the central part of chromosome 4. Images

Begley, C G; Visvader, J; Green, A R; Aplan, P D; Metcalf, D; Kirsch, I R; Gough, N M

1991-01-01

116

An Activation Domain of the Helix-Loop-Helix Transcription Factor E2A Shows Cell Type Preference In Vivo in Microinjected Zebra Fish Embryos  

Microsoft Academic Search

The E2A protein is a mammalian transcription factor of the helix-loop-helix family which is implicated in cell-specific gene expression in several cell lineages. Mouse E2A contains two independent transcription activation domains, ADI and ADII; whereas ADI functions effectively in a variety of cultured cell lines, ADII showspreferentialactivityinpancreaticbetacells.Toanalyzethispreferentialactivityinaninvivosetting,we adapted a system involving transient gene expression in microinjected zebra fish embryos. Fertilized

FRANCESCO ARGENTON; YOAV ARAVA; AMI ARONHEIM; ANDMICHAEL D. WALKER

1996-01-01

117

Oligomerization Mediated by a Helix-Loop-Helix-Like Domain of Baculovirus IE1 Is Required for Early Promoter Transactivation  

PubMed Central

IE1 is a principal transcriptional regulator of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Transactivation by IE1 is stimulated when early viral promoters are cis linked to homologous-region (hr) enhancer sequences of AcMNPV. This transcriptional enhancement is correlated with the binding of IE1 as a dimer to the 28-bp palindromic repeats comprising the hr enhancer. To define the role of homophilic interactions in IE1 transactivation, we have mapped the IE1 domains required for oligomerization. We report here that IE1 oligomerizes by a mechanism independent of enhancer binding, as demonstrated by in vitro pull-down assays using fusions of IE1 (582 residues) to the C terminus of glutathione S-transferase. In vivo oligomerization of IE1 was verified by immunoprecipitation of IE1 complexes from extracts of plasmid-transfected SF21 cells. Analyses of a series of site-directed IE1 insertion mutations indicated that a helix-loop-helix (HLH)-like domain extending from residue 543 to residue 568 is the primary determinant of oligomerization. Replacement of residues within the hydrophobic face of the putative dimerization domain disrupted IE1 homophilic interactions and caused loss of IE1 transactivation of hr-dependent promoters in plasmid transfection assays. Thus, oligomerization is required for IE1 transcriptional stimulation. HLH mutations also reduced IE1 stability and abrogated transactivation of non-hr-dependent promoters. These data support a model wherein IE1 oligomerizes prior to DNA binding to facilitate proper interaction with the symmetrical recognition sites within the hr enhancer and thereby promote the transcription of early viral genes.

Olson, Victoria A.; Wetter, Justin A.; Friesen, Paul D.

2001-01-01

118

TAL2, a helix-loop-helix gene activated by the (7; 9)(q34; q32) translocation in human T-cell leukemia  

SciTech Connect

Tumor-specific alteration of the TAL1 gene occurs in almost 25% of patients with T-cell acute lymphoblastic leukemia (T-ALL). The authors now report the identification of TAL2, a distinct gene that was isolated on the basis of its sequence homology with TAL1. The TAL2 gene is located 33 kilobase pairs from the chromosome 9 breakpoint of t(7;9)(q34;q32), a recurring translocation specifically associated with T-ALL. As a consequence of t(7;9)(q34;q32), TAL2 is juxtaposed with sequences from the T-cell receptor {beta}-chain gene on chromosome 7. TAL2 sequences are actively transcribed in SUP-T3, a T-ALL cell line that harbors the t(7;9)(q34;q32). The TAL2 gene product includes a helix-loop-helix protein dimerization and DNA binding domain that is especially homologous to those encoded by the TAL1 and LYL1 protooncogenes. Hence, TAL2, TAL1, and LYL1 constitute a discrete subgroup of helix-loop-helix proteins, each of which can potentially contribute to the development of T-ALL.

Ying Xia; Brown, L.; Yang, C.Y.; Tsan, J.T.; Baer, R.J. (Univ. of Texas, Dallas (United States)); Siciliano, M.J. (Univ. of Texas, Houston (United States)); Espinosa, R. III; Le Beau, M.M. (Univ. of Chicago, IL (United States))

1991-12-15

119

Basic Helix-Loop-Helix Transcription Factor Twist1 Inhibits Transactivator Function of Master Chondrogenic Regulator Sox9*  

PubMed Central

Canonical Wnt signaling strongly inhibits chondrogenesis. Previously, we identified Twist1 as a critical downstream mediator of Wnt in repression of chondrocyte differentiation. However, the mechanistic basis for the antichondrogenic activity of Twist1 has not heretofore been established. Here, we show that Twist1 suppresses cartilage development by directly inhibiting the transcriptional activity of Sox9, the master regulator of chondrogenesis. Twist1, through its carboxyl-terminal Twist-box, binds to the Sox9 high mobility group DNA-binding domain, inhibiting Sox9 transactivation potential. In chondrocyte precursor cells, Twist1, in a Twist-box-dependent manner, inhibits Sox9-dependent activation of chondrocyte marker gene expression by blocking Sox9-enhancer DNA association. These findings identify Twist1 as an inhibitor of Sox9 and further suggest that the balance between Twist1 and Sox9 may determine the earliest steps of chondrogenesis.

Gu, Shoujun; Boyer, Thomas G.; Naski, Michael C.

2012-01-01

120

Basic helix-loop-helix transcriptional factor MyoR regulates BMP-7 in acute kidney injury.  

PubMed

MyoR was originally identified as a transcriptional repressor in embryonic skeletal muscle precursors, but its function in adult kidney has not been clarified. In this study, we tried to clarify the functional role of MyoR using MyoR(-/-) mice. Cisplatin induced a significantly higher degree of severe renal dysfunction, tubular injury, and mortality in MyoR(-/-) mice than in wild-type mice. The injection of cisplatin significantly increased the number of apoptotic cells in the kidney tissues of MyoR(-/-) mice, compared with that in wild-type mice. To clarify the mechanism of severe cisplatin-induced damage and apoptosis in MyoR(-/-) mice, we focused on the p53 signaling pathway and bone morphogenic protein-7 (BMP-7). Treatment with cisplatin significantly activated p53 signaling in cultured renal proximal tubular epithelial cells (RTECs) in both wild-type and MyoR(-/-) mice, but no significant difference between the groups was observed. The injection of cisplatin significantly increased the expression of BMP-7 in the kidney tissues of wild-type mice, but no increase was observed in the MyoR(-/-) mice. Treatment with cisplatin significantly increased the expression of BMP-7 in cultured RTECs from wild-type mice but not in those from MyoR(-/-) mice. Moreover, treatment with recombinant BMP-7 rescued the cisplatin-induced apoptosis in RTECs from MyoR(-/-) mice. Taken together, our results demonstrate a new protective role of MyoR in adult kidneys that acts through the regulation of BMP-7. PMID:23515721

Kamiura, Nozomu; Hirahashi, Junichi; Matsuzaki, Yumi; Idei, Mana; Takase, Osamu; Fujita, Toshiro; Takato, Tsuyoshi; Hishikawa, Keiichi

2013-03-20

121

A Divalent Ion Is Crucial in the Structure and Dominant-Negative Function of ID Proteins, a Class of Helix-Loop-Helix Transcription Regulators  

PubMed Central

Inhibitors of DNA binding and differentiation (ID) proteins, a dominant-negative group of helix-loop-helix (HLH) transcription regulators, are well-characterized key players in cellular fate determination during development in mammals as well as Drosophila. Although not oncogenes themselves, their upregulation by various oncogenic proteins (such as Ras, Myc) and their inhibitory effects on cell cycle proteins (such as pRb) hint at their possible roles in tumorigenesis. Furthermore, their potency as inhibitors of cellular differentiation, through their heterodimerization with subsequent inactivation of the ubiquitous E proteins, suggest possible novel roles in engineering induced pluripotent stem cells (iPSCs). We present the high-resolution 2.1Å crystal structure of ID2 (HLH domain), coupled with novel biochemical insights in the presence of a divalent ion, possibly calcium (Ca2+), in the loop of ID proteins, which appear to be crucial for the structure and activity of ID proteins. These new insights will pave the way for new rational drug designs, in addition to current synthetic peptide options, against this potent player in tumorigenesis as well as more efficient ways for stem cells reprogramming.

Palasingam, Paaventhan; Kolatkar, Prasanna R.

2012-01-01

122

Expression of the helix-loop-helix protein inhibitor of DNA binding-1 (ID-1) is activated by all-trans retinoic acid in normal human keratinocytes  

SciTech Connect

The ID (inhibitor of differentiation or DNA binding) helix-loop-helix proteins are important mediators of cellular differentiation and proliferation in a variety of cell types through regulation of gene expression. Overexpression of the ID proteins in normal human keratinocytes results in extension of culture lifespan, indicating that these proteins are important for epidermal differentiation. Our hypothesis is that the ID proteins are targets of the retinoic acid signaling pathway in keratinocytes. Retinoids, vitamin A analogues, are powerful regulators of cell growth and differentiation and are widely used in the prevention and treatment of a variety of cancers in humans. Furthermore, retinoic acid is necessary for the maintenance of epithelial differentiation and demonstrates an inhibitory action on skin carcinogenesis. We examined the effect of all-trans retinoic acid on expression of ID-1, -2, -3, and -4 in normal human keratinocytes and found that exposure of these cells to all-trans retinoic acid causes an increase in both ID-1 and ID-3 gene expression. Furthermore, our data show that this increase is mediated by increased transcription involving several cis-acting elements in the distal portion of the promoter, including a CREB-binding site, an Egr1 element, and an YY1 site. These data demonstrate that the ID proteins are direct targets of the retinoic acid signaling pathway. Given the importance of the ID proteins to epidermal differentiation, these results suggest that IDs may be mediating some of the effects of all-trans retinoic acid in normal human keratinocytes.

Villano, C.M. [Department of Biochemistry and Microbiology, 76 Lipman Drive, Rutgers, State University of NJ, New Brunswick, NJ 08901 (United States); White, L.A. [Department of Biochemistry and Microbiology, 76 Lipman Drive, Rutgers, State University of NJ, New Brunswick, NJ 08901 (United States)]. E-mail: lawhite@aesop.rutgers.edu

2006-08-01

123

Cloning and characterization of MN, a human tumor-associated protein with a domain homologous to carbonic anhydrase and a putative helix-loop-helix DNA binding segment.  

PubMed

MN is a transmembrane glycoprotein that has been detected in HeLa cells and in some human carcinomas. The expression of MN protein in HeLa cells is regulated by cell density. In HeLa x fibroblast cell hybrids its expression correlates with tumorigenicity. Using a specific monoclonal antibody we have identified a cDNA clone coding for MN. Analysis of the deduced amino acid sequence revealed strong structural homology between the central region of the MN protein and carbonic anhydrases (CA). MN sequence retains the conserved zinc-binding site as well as the enzyme's active center. In accord with these findings, MN protein from HeLa cells was found to bind zinc and to have carbonic anhydrase activity. The N-terminal region of MN shares some similarity with DNA binding proteins of the helix-loop-helix (HLH) family, and the protein was found to have affinity for DNA by DNA-cellulose chromatography. The region between the CA-like domain and the putative HLH domain is rich in imperfect repeats of serine, proline, glycine and acidic residues with few hydrophobic amino acids, resembling thus an activation region of transcription factors. The fact that MN protein is detectable in several types of human carcinomas, but not in corresponding non-cancerous tissues, suggests its possible role in neoplasia. In addition, the analysis of biological consequences of MN expression of NIH3T3 cells provides the evidence in favour of MN protein involvement in control of cell proliferation and transformation. PMID:8084592

Pastorek, J; Pastoreková, S; Callebaut, I; Mornon, J P; Zelník, V; Opavský, R; Zat'ovicová, M; Liao, S; Portetelle, D; Stanbridge, E J

1994-10-01

124

A cell-penetrating peptide suppresses the hypoxia inducible factor-1 function by binding to the helix-loop-helix domain of the aryl hydrocarbon receptor nuclear translocator.  

PubMed

The heterodimeric hypoxia inducible factor-1 (HIF-1) complex is composed of the hypoxia inducible factor-1 alpha (HIF-1?) and the aryl hydrocarbon receptor nuclear translocator (ARNT). Activation of the HIF-1 function is essential for tumor growth and metastasis. We previously showed that transfection of a plasmid containing an ARNT-interacting peptide (Ainp1) cDNA suppresses the HIF-1 signaling in Hep3B cells. Here we generated TAT fusion of the Ainp1 peptide (6His-TAT-Ainp1) to determine whether and how the Ainp1 peptide suppresses the HIF-1 function. The bacterially expressed 6His-TAT-Ainp1 was purified under denatured condition and then refolded by limited dialysis. The refolded 6His-TAT-Ainp1 interacts with the helix-loop-helix (HLH) domain of ARNT in a similar fashion as the native 6His-Ainp1. 6His-TAT-Ainp1 colocalizes with ARNT in the nucleus of HeLa and Hep3B cells after protein transduction. The transduced protein reaches the maximum intracellular levels within 2 h while remains detectable up to 96 h in HeLa cells. At 2 ?M concentration, 6His-TAT-Ainp1 is not cytotoxic in HeLa cells but suppresses the cobalt chloride-activated, hypoxia responsive enhancer-driven luciferase expression in a dose-dependent manner. In addition, it decreases the cobalt chloride-dependent induction of the HIF-1 target genes at both the message (vascular endothelial growth factor and aldolase C) and protein (carbonic anhydrase IX and glucose transporter 1) levels. The protein levels of HIF-1? and ARNT are not altered in the presence of 6His-TAT-Ainp1. In summary, we provided evidence to support that the Ainp1 peptide directly suppresses the HIF-1 function by interacting with the ARNT HLH domain, and in turn interfering with the heterodimerization of HIF-1? and ARNT. PMID:23454269

Wang, Yu; Thompson, John D; Chan, William K

2013-02-27

125

Sumoylation of the basic helix-loop-helix transcription factor sharp-1 regulates recruitment of the histone methyltransferase G9a and function in myogenesis.  

PubMed

Sumoylation is an important post-translational modification that alters the activity of many transcription factors. However, the mechanisms that link sumoylation to alterations in chromatin structure, which culminate in tissue specific gene expression, are not fully understood. In this study, we demonstrate that SUMO modification of the transcription factor Sharp-1 is required for its full transcriptional repression activity and function as an inhibitor of skeletal muscle differentiation. Sharp-1 is modified by sumoylation at two conserved lysine residues 240 and 255. Mutation of these SUMO acceptor sites in Sharp-1 does not impact its subcellular localization but attenuates its ability to act as a transcriptional repressor and inhibit myogenic differentiation. Consistently, co-expression of the SUMO protease SENP1 with wild type Sharp-1 abrogates Sharp-1-dependent inhibition of myogenesis. Interestingly, sumoylation acts as a signal for recruitment of the co-repressor G9a. Thus, enrichment of G9a, and histone H3 lysine 9 dimethylation (H3K9me2), a signature of G9a activity, is dramatically reduced at muscle promoters in cells expressing sumoylation-defective Sharp-1. Our findings demonstrate how sumoylation of Sharp-1 exerts an impact on chromatin structure and transcriptional repression of muscle gene expression through recruitment of G9a. PMID:23637228

Wang, Yaju; Shankar, Shilpa Rani; Kher, Devaki; Ling, Belinda Mei Tze; Taneja, Reshma

2013-04-30

126

Proneural Basic Helix-Loop-Helix Proteins and Epidermal Growth Factor Receptor Signaling Coordinately Regulate Cell Type Specification and cdk Inhibitor Expression during Development  

Microsoft Academic Search

Received 8 September 2006\\/Returned for modification 27 December 2006\\/Accepted 3 February 2007 Cell differentiation and cell cycle exit are coordinately regulated during development; however, the molecular logic underlying this regulation is not known. The Drosophila cdk inhibitor Dacapo (Dap) is one of the key cell cycle regulators that exhibit dynamic expression during development and contribute to the developmental regulation of

Madina J. Sukhanova; Dilip K. Deb; Gabriel M. Gordon; Miho Tanaka Matakatsu; Wei Du

2007-01-01

127

Developmental and evolutionary aspects of the basic helix–loop–helix transcription factors Atonal-like 1 and Achaete-scute homolog 2 in the jellyfish  

Microsoft Academic Search

The close functional link of nerve and muscle cells in neuromuscular units has led to the hypothesis of a common evolutionary origin of both cell types. Jellyfish are well suited to evaluate this theory since they represent the most basal extant organisms featuring both striated muscle and a nervous system. Here we describe the structure and expression of two novel

Katja Seipel; Nathalie Yanze; Volker Schmid

2004-01-01

128

Induction of Early B Cell Factor (EBF) and Multiple B Lineage Genes by the Basic Helix-Loop-Helix Transcription Factor E12  

PubMed Central

The transcription factors encoded by the E2A and early B cell factor (EBF) genes are required for the proper development of B lymphocytes. However, the absence of B lineage cells in E2A- and EBF-deficient mice has made it difficult to determine the function or relationship between these proteins. We report the identification of a novel model system in which the role of E2A and EBF in the regulation of multiple B lineage traits can be studied. We found that the conversion of 70Z/3 pre-B lymphocytes to cells with a macrophage-like phenotype is associated with the loss of E2A and EBF. Moreover, we show that ectopic expression of the E2A protein E12 in this macrophage line results in the induction of many B lineage genes, including EBF, IL7R?, ?5, and Rag-1, and the ability to induce ? light chain in response to mitogen. Activation of EBF may be one of the critical functions of E12 in regulating the B lineage phenotype since expression of EBF alone leads to the activation of a subset of E12-inducible traits. Our data demonstrate that, in the context of this macrophage line, E12 induces expression of EBF and together these transcription factors coordinately regulate numerous B lineage–associated genes.

Kee, Barbara L.; Murre, Cornelis

1998-01-01

129

A novel basic region\\/helix-loop-helix protein binds to a G-box motif CACGTG of the bean seed storage protein ?- phaseolin gene  

Microsoft Academic Search

Expression of the bean seed storage protein ?-phaseolin is under strict developmental control primarily at the level of transcription. A G-box motif CACGTG has been shown to be a major positive cis-acting element of the ?-phaseolin gene and to be recognized by a DNA binding protein from bean seed nuclei. To understand the molecular nature of the G-box-binding protein, we

Yasushi Kawagoe; Norimoto Murai

1996-01-01

130

Transcription Enhancer Factor 1 Interacts with a Basic Helix-Loop- Helix Zipper Protein, Max, for Positive Regulation of Cardiac a-Myosin Heavy-Chain Gene Expression  

Microsoft Academic Search

The M-CAT binding factor transcription enhancer factor 1 (TEF-1) has been implicated in the regulation of several cardiac and skeletal muscle genes. Previously, we identified an E-box-M-CAT hybrid (EM) motif that is responsible for the basal and cyclic AMP-inducible expression of the rat cardiac a-myosin heavy chain (a-MHC) gene in cardiac myocytes. In this study, we report that two factors,

MAHESH P. GUPTA; CHIRAG S. AMIN; MADHU GUPTA; NISSIM HAY; RADOVAN ZAK

1997-01-01

131

Regeneration of Transgenic Skeletal Muscles with Altered Timing of Expression of the Basic Helix-Loop-Helix Muscle Regulatory Factor MRF4  

PubMed Central

In regenerating muscle cells, muscle regulatory factor (MRF) 4 is normally the last of the four MRFs to be expressed. To analyze how the timing of MRF4 expression affects muscle regeneration, we compared regeneration after local freeze injury of muscles from wild-type mice with muscles from transgenic mice in which MRF4 expression was under control of an ?1.6-kb fragment of the myogenin promoter. Three days after injury, masseter and tibialis anterior (TA) muscles in wild-type mice expressed little or no MRF4 mRNA; whereas these muscles in transgenic mice expressed abundant MRF4 mRNA from both the transgene and the endogenous gene. Thus, MRF4 up-regulation was accelerated in transgenic compared to wild-type regenerating muscles, and expression of the transgene appeared to activate, perhaps indirectly, expression of the endogenous MRF4 gene. At 11 days after injury, regeneration, as measured by cross-sectional area and density of regenerated fibers, was significantly impaired in transgenic TA compared to wild-type TA, whereas at 19 days after injury both transgenic and TA muscle fibers had fully recovered to preinjury values. Regeneration of masseter muscles, which normally regenerate much less completely than TA muscles, was unaffected by the transgene. Thus, the timing of MRF4 up-regulation, as well as additional muscle-specific factors, can determine the progress of muscle regeneration.

Pavlath, Grace K.; Dominov, Janice A.; Kegley, Kristy M.; Miller, Jeffrey Boone

2003-01-01

132

Specificity for the Hairy/enhancer of split basic helix-loop-helix (bHLH) proteins maps outside the bHLH domain and suggests two separable modes of transcriptional repression  

SciTech Connect

This report investigates transcriptional repressors in Drosophila melanogaster and their function in and effect on developmental processes such as sex determination. Details on the mechanism of function of these transcriptional repressors are also discussed. 50 refs., 3 figs., 4 tabs.

Dawson, S.R.; Turner, D.L.; Weintraub, H.; Parkhurst, S.M. [Fred Hutchinson Cancer Research Center, Seattle, WA (United States)

1995-12-01

133

Establishment of Distinct MyoD, E2A, and Twist DNA Binding Specificities by Different Basic Region-DNA Conformations  

Microsoft Academic Search

Basic helix-loop-helix (bHLH) proteins perform a wide variety of biological functions. Most bHLH proteins recognize the consensus DNA sequence CAN NTG (the E-box consensus sequence is underlined) but acquire further functional specificity by preferring distinct internal and flanking bases. In addition, induction of myogenesis by MyoD-related bHLH proteins depends on myogenic basic region (BR) and BR-HLH junction residues that are

THIPHAPHONE KOPHENGNAVONG; JENNIFER E. MICHNOWICZ; T. KEITH BLACKWELL

2000-01-01

134

Helix-Loop-Helix Transcription Factors Mediate Activation and Repression of thep75LNFRGene  

Microsoft Academic Search

Sequence analysis of rat and human low-affinity nerve growth factor receptor p75LNGFR gene promoter regions revealed a single E-box cis-acting element, located upstream of the major transcription start sites. Deletion analysis of the E-box sequence demonstrated that it significantly contributes top75LNGFRpromoter activity. This E box has a dual function; it mediates either activation or repression of thep75LNGFRpromoter activity, depending on

ANNE CHIARAMELLO; KULLIKI NEUMAN; KAIA PALM; MADIS METSIS; ANDTOOMAS NEUMAN

1995-01-01

135

Rbms3, an RNA-binding protein, mediates the expression of Ptf1a by binding to its 3'UTR during mouse pancreas development.  

PubMed

The development of the pancreas is a complicated process that is regulated on several levels. Pancreas transcription factor 1, alpha subunit (Ptf1a), also known as p48, is a pancreas-specific basic helix-loop-helix transcription factor that is critical for both exocrine pancreas development and maintenance of acinar cell differentiation. Based on a differential screening assay, we identified Rbms3, a gene encoding a glycine-rich RNA-binding protein, to be specifically expressed in the neural tube and the pancreatic rudiment of e10.5 embryos. The presence of Rbms3 in the early developing pancreas suggests that specific post-transcriptional regulation mechanisms play an important role in controlling pancreas development. In this study, we show that Rbms3 binds to the 3'UTR of Ptf1a mRNA, but not the 3'UTR of Pdx1, which is another pancreatic transcription factor. The ectopic expression of Rbms3 stimulates the translation of a reporter gene carrying the Ptf1a 3'UTR. In addition, when Rbms3 expression is suppressed in the AR42J-B13 pancreatic exocrine cell line, the expression of Ptf1a is also down-regulated. These results suggest that binding of Rbms3 to the 3'UTR of Ptf1a regulates the production of the Ptf1a protein and, thereby, indirectly regulates the expression of the Ptf1a downstream target genes. PMID:22372950

Lu, Chung-Kuang; Lai, Yi-Chyi; Chen, Hau-Ren; Chiang, Ming-Ko

2012-02-28

136

Identifying Novel Helix-Loop-Helix Genes in "Caenorhabditis elegans" through a Classroom Demonstration of Functional Genomics  

ERIC Educational Resources Information Center

A 14-week, undergraduate-level Genetics and Population Biology course at Morgan State University was modified to include a demonstration of functional genomics in the research laboratory. Students performed a rudimentary sequence analysis of the "Caenorhabditis elegans" genome and further characterized three sequences that were predicted to encode…

Griffin, Vernetta; McMiller, Tracee; Jones, Erika; Johnson, Casonya M.

2003-01-01

137

BASIC PENTACYSTEINE Proteins Mediate MADS Domain Complex Binding to the DNA for Tissue-Specific Expression of Target Genes in Arabidopsis[W  

PubMed Central

BASIC PENTACYSTEINE (BPC) transcription factors have been identified in a large variety of plant species. In Arabidopsis thaliana there are seven BPC genes, which, except for BPC5, are expressed ubiquitously. BPC genes are functionally redundant in a wide range of developmental processes. Recently, we reported that BPC1 binds to guanine and adenine (GA)–rich consensus sequences in the SEEDSTICK (STK) promoter in vitro and induces conformational changes. Here we show by chromatin immunoprecipitation experiments that in vivo BPCs also bind to the consensus boxes, and when these were mutated, expression from the STK promoter was derepressed, resulting in ectopic expression in the inflorescence. We also reveal that SHORT VEGETATIVE PHASE (SVP) is a direct regulator of STK. SVP is a floral meristem identity gene belonging to the MADS box gene family. The SVP-APETALA1 (AP1) dimer recruits the SEUSS (SEU)-LEUNIG (LUG) transcriptional cosuppressor to repress floral homeotic gene expression in the floral meristem. Interestingly, we found that GA consensus sequences in the STK promoter to which BPCs bind are essential for recruitment of the corepressor complex to this promoter. Our data suggest that we have identified a new regulatory mechanism controlling plant gene expression that is probably generally used, when considering BPCs’ wide expression profile and the frequent presence of consensus binding sites in plant promoters.

Simonini, Sara; Roig-Villanova, Irma; Gregis, Veronica; Colombo, Bilitis; Colombo, Lucia; Kater, Martin M.

2012-01-01

138

Glucose and other insulin secretagogues induce, rather than inhibit, expression of Id1 and Id3 in pancreatic islet beta cells  

Microsoft Academic Search

Aims\\/hypothesis. Basic helix loop helix transcription factors regulate insulin gene transcription. Therefore, molecules that regulate their\\u000a function should affect insulin production and secretion. As Id proteins inhibit basic helix loop helix function, it is important\\u000a to determine whether they are expressed in beta cells and if insulin secretagogues regulate their expression. Methods. Human islets or insulinoma cells were cultured in

B. M. Wice; E. Bernal-Mizrachi; M. A. Permutt

2001-01-01

139

p204 Protein Overcomes the Inhibition of Core Binding Factor ?-1-mediated Osteogenic Differentiation by Id Helix-Loop-Helix Proteins  

PubMed Central

Id proteins play important roles in osteogenic differentiation; however, the molecular mechanism remains unknown. In this study, we established that inhibitor of differentiation (Id) proteins, including Id1, Id2, and Id3, associate with core binding factor ?-1 (Cbfa1) to cause diminished transcription of the alkaline phosphatase (ALP) and osteocalcin (OCL) gene, leading to less ALP activity and osteocalcin (OCL) production. Id acts by inhibiting the sequence-specific binding of Cbfa1 to DNA and by decreasing the expression of Cbfa1 in cells undergoing osteogenic differentiation. p204, an interferon-inducible protein that interacts with both Cbfa1 and Id2, overcame the Id2-mediated inhibition of Cbfa1-induced ALP activity and OCL production. We show that 1) p204 disturbed the binding of Id2 to Cbfa1 and enabled Cbfa1 to bind to the promoters of its target genes and 2) that p204 promoted the translocation from nucleus to the cytoplasm and accelerated the degradation of Id2 by ubiquitin–proteasome pathway during osteogenesis. Nucleus export signal (NES) of p204 is required for the p204-enhanced cytoplasmic translocation and degradation of Id2, because a p204 mutant lacking NES lost these activities. Together, Cbfa1, p204, and Id proteins form a regulatory circuit and act in concert to regulate osteoblast differentiation.

Luan, Yi; Yu, Xiu-Ping; Yang, Ning; Frenkel, Sally; Chen, Lin

2008-01-01

140

A smallest 6 kda metalloprotease, mini-matrilysin, in living world: a revolutionary conserved zinc-dependent proteolytic domain- helix-loop-helix catalytic zinc binding domain (ZBD)  

PubMed Central

Background The Aim of this study is to study the minimum zinc dependent metalloprotease catalytic folding motif, helix B Met loop-helix C, with proteolytic catalytic activities in metzincin super family. The metzincin super family share a catalytic domain consisting of a twisted five-stranded ? sheet and three long ? helices (A, B and C). The catalytic zinc is at the bottom of the cleft and is ligated by three His residues in the consensus sequence motif, HEXXHXXGXXH, which is located in helix B and part of the adjacent Met turn region. An interesting question is - what is the minimum portion of the enzyme that still possesses catalytic and inhibitor recognition?” Methods We have expressed a 60-residue truncated form of matrilysin which retains only the helix B-Met turn-helix C region and deletes helix A and the five-stranded ? sheet which form the upper portion of the active cleft. This is only 1/4 of the full catalytic domain. The E. coli derived 6?kDa MMP-7 ZBD fragments were purified and refolded. The proteolytic activities were analyzed by Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2 peptide assay and CM-transferrin zymography analysis. SC44463, BB94 and Phosphoramidon were computationally docked into the 3day structure of the human MMP7 ZBD and TAD and thermolysin using the docking program GOLD. Results This minimal 6?kDa matrilysin has been refolded and shown to have proteolytic activity in the Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2 peptide assay. Triton X-100 and heparin are important factors in the refolding environment for this mini-enzyme matrilysin. This minienzyme has the proteolytic activity towards peptide substrate, but the hexamer and octamer of the mini MMP-7 complex demonstrates the CM-transferrin proteolytic activities in zymographic analysis. Peptide digestion is inhibited by SC44463, specific MMP7 inhibitors, but not phosphorimadon. Interestingly, the mini MMP-7 can be processed by autolysis and producing?~?6?~?7?kDa fragments. Thus, many of the functions of the enzyme are retained indicating that the helix B-Met loop-helix C is the minimal functional “domain” found to date for the matrixin family. Conclusions The helix B-Met loop-helix C folding conserved in metalloprotease metzincin super family is able to facilitate proteolytic catalysis for specific substrate and inhibitor recognition. The autolysis processing and producing 6?kDa mini MMP-7 is the smallest metalloprotease in living world.

2012-01-01

141

Upregulation of Id2, an oncogenic helix-loop-helix protein, is mediated by the chimeric EWS\\/ets protein in Ewing sarcoma  

Microsoft Academic Search

The chromosomal translocation specifically linked to the Ewing sarcoma family results in the generation of fusion proteins comprising the amino terminal portion of EWS and the DNA-binding domain of ets transcription factors. The EWS\\/ets chimeric proteins act as aberrant transcription factors leading to tumorigenic processes. We searched for genes specifically activated in Ewing sarcoma cells but not in other tumor

Mariko Fukuma; Hajime Okita; Jun-ichi Hata; Akihiro Umezawa

2003-01-01

142

Kaposi's Sarcoma-Associated Herpesvirus Latency-Associated Nuclear Antigen Induces Expression of the Helix-Loop-Helix Protein Id1 in Human Endothelial Cells  

Microsoft Academic Search

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) (also known as human herpesvirus 8) is a gamma-2 herpesvirus believed to be the etiologic agent responsible for KS. The pathogenesis of this potentially life- threatening neoplasm is complex and unclear, and it is currently unknown how KSHV causes KS. Id (named for inhibitor of DNA binding or inhibitor of differentiation) proteins were identified in

Jun Tang; Gabriel M. Gordon; Maike G. Muller; Madhu Dahiya; Kimberly E. Foreman

2003-01-01

143

Autoregulated Expression of the YeastINO2andINO4 Helix-Loop-Helix Activator Genes Effects Cooperative Regulation on Their Target Genes  

Microsoft Academic Search

In the yeast Saccharomyces cerevisiae, the phospholipid biosynthetic genes are highly regulated at the transcriptional level in response to the phospholipid precursors inositol and choline. In the absence of inositol and choline (derepressing), the products of theINO2andINO4genes form a heteromeric complex which binds to a 10-bp element, upstream activation sequence INO (UASINO), in the promoters of the phospholipid biosynthetic genes

BRIAN P. ASHBURNER; ANDJOHN M. LOPES

1995-01-01

144

Multiscale Simulation of Protein Mediated Membrane Remodeling  

PubMed Central

Proteins interacting with membranes can result in substantial membrane deformations and curvatures. This effect is known in its broadest terms as membrane remodeling. This review article will survey current multiscale simulation methodologies that have been employed to examine protein-mediated membrane remodeling.

Ayton, Gary S.; Voth, Gregory A.

2009-01-01

145

The NEUROD gene maps to human chromosome 2q32 and mouse chromosome 2  

SciTech Connect

The Neurod gene is a basic-helix-loop-helix gene that regulates neurogenesis and is identical to the hamster beta2 gene that was cloned as a regulator of insulin transcription. Here we report the cloning of human NEUROD and mapping of the gene to human chromosome 2q32 and to mouse chromosome 2. 12 refs., 1 fig.

Tamimi, R.; Dyer-Montgomery, K.; Hernandez, R.; Tapscott, S.J. [Fred Hutchinson Cancer Research Center, Seattle, WA (United States)] [and others

1996-06-15

146

NEUROD2 and NEUROD3 genes map to human chromosomes 17q12 and 5q23-q31 and mouse chromosomes 11 and 13, respectively  

SciTech Connect

NEUROD2 and NEUROD3 are transcription factors involved in neurogenesis that are related to the basic helix-loop-helix protein NEUROD. NEUROD2 maps to human chromosome 17q12 and mouse chromosome 11. NEUROD3 maps to human chromosome 5q23-q31 and mouse chromosome 13. 16 refs., 2 figs.

Tamimi, R.M.; Montgomery-Dyer, K.; Tapscott, S.J. [Fred Hutchinson Cancer Research Center, Seattle, WA (United States)] [and others

1997-03-01

147

Phytochrome Induces Rapid PIF5 Phosphorylation and Degradation in Response to Red-Light Activation  

Technology Transfer Automated Retrieval System (TEKTRAN)

The phytochrome (phy) family of sensory photoreceptors (phyA–phyE in Arabidopsis thaliana) induces changes in target-gene expression upon light-induced translocation to the nucleus, where certain members interact with selected members of the constitutively nuclear basic helix-loop-helix transcriptio...

148

Sense organ identity in the Drosophila antenna is specified by the expression of the proneural gene atonal  

Microsoft Academic Search

We have shown that the basic helix–loop–helix transcription factor Atonal is sufficient for specification of one of the three subsets of olfactory sense organs on the Drosophila antenna. Misexpression of Atonal in all sensory precursors in the antennal disc results in their conversion to coeloconic sensilla. The mechanism by which specific sense organ fate is triggered remains unclear. We have

Dhanisha Jhaveri; Anindya Sen; G. Venugopala Reddy; Veronica Rodrigues

2000-01-01

149

GENOMIC CHARACTERIZATION OF A NOVEL PAIR OF ID GENES IN THE RAINBOW TROUT (ONCORHYNCHUS MYKISS)  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Id (Inhibitors of DNA Binding/Differentiation) proteins represent a family of dominant negative regulators of the basic helix-loop-helix transcription factors whose activities result in delayed cell differentiation and prolonged proliferation. A pair of expressed sequence tag clones with homolo...

150

Cannabidiol as a novel inhibitor of Id1 gene expression in aggressive breast cancer cells  

Microsoft Academic Search

Invasion and metastasis of aggressive breast cancer cells is the final and fatal step during cancer progression, and is the least understood genetically. Clinically, there are still limited therapeutic interventions for aggressive and meta- static breast cancers available. Clearly, effective and non- toxic therapies are urgently required. Id-1, an inhibitor of basic helix-loop-helix transcription factors, has recently been shown to

Sean D. McAllister; Rigel T. Christian; Maxx P. Horowitz; Amaia Garcia; Pierre-Yves Desprez

2007-01-01

151

Endothelial PAS Domain Protein 1 Gene Promotes Angiogenesis Through the Transactivation of Both Vascular Endothelial Growth Factor and Its Receptor, Flt1  

Microsoft Academic Search

Abstract—Endothelial PAS domain,protein 1 (EPAS1) is a basic-helix–loophelix\\/PAS domain,transcription factor that is expressed preferentially in vascular endothelial cells. EPAS1 shares high homology,with hypoxia-inducible factor-1 (HIF-1) and is reported to transactivate vascular endothelial growth factor (VEGF), fetal liver kinase-1 (Flk-1), and

Norihiko Takeda; Koji Maemura; Yasushi Imai; Tomohiro Harada; Daiji Kawanami; Takefumi Nojiri; Ichiro Manabe; Ryozo Nagai

2010-01-01

152

IDENTIFICATION AND EXPRESSION PROFILE OF THE ID GENE FAMILY IN RAINBOW TROUT (ONCORHYNCHUS MYKISS)  

Technology Transfer Automated Retrieval System (TEKTRAN)

The ID proteins are negative regulators of basic helix-loop-helix transcription factors. The role of these proteins in regulating mammalian growth and development has generated interest in them as candidate genes for affecting aquaculture production traits. We report the identification and charact...

153

The microphthalmia transcription factor and the related helix- loop-helix zipper factors TFE-3 and TFE-C collaborate to activate the tartrate-resistant acid phosphatase promoter  

Microsoft Academic Search

The microphthalmia transcription fac- tor (MITF) regulates different target genes in sev- eral distinct cell types, including osteoclasts. The role of the closely related factors TFE3 and TFEC in MITF action was studied. The TFE3 and TFEC proteins were expressed in osteoclast-like cells, and both could be immunoprecipitated in a com- plex with MITF. In transient transfection assays, TFE3 and

Kim C. Mansky; Sabine Sulzbacher; Georgia Purdom; Lori Nelsen; David A. Hume; Michael Rehli; Michael C. Ostrowski

154

Determinants of Myogenic Specificity within MyoD Are Required for Noncanonical E Box Binding  

Microsoft Academic Search

The MyoD family of basic helix-loop-helix (bHLH) transcription factors has the remarkable ability to induce myogenesis in vitro and in vivo. This myogenic specificity has been mapped to two amino acids in the basic domain, an alanine and threonine, referred to as the myogenic code. These essential determinants of myogenic specificity are conserved in all MyoD family members from worms

Analeah B. Heidt; Anabel Rojas; Ian S. Harris; Brian L. Black

2007-01-01

155

Induction of motor neuron differentiation by transduction of Olig2 protein.  

PubMed

Olig2 protein, a member of the basic helix-loop-helix transcription factor family, was introduced into the mouse embryonic carcinoma cell line P19 for induction of motor neuron differentiation. We show that Olig2 protein has the ability to permeate the cell membrane without the addition of a protein transduction domain (PTD), similar to other basic helix-loop-helix transcription factors such as MyoD and NeuroD2. Motor neuron differentiation was evaluated for the elongation of neurites and the expression of choline acetyltransferase (ChAT) mRNA, a differentiation marker of motor neurons. By addition of Olig2 protein, motor neuron differentiation was induced in P19 cells. PMID:23022191

Mie, Masayasu; Kaneko, Mami; Henmi, Fumiaki; Kobatake, Eiry

2012-09-26

156

Protein-mediated surface structuring in biomembranes.  

PubMed

The lipids and proteins of biomembranes exhibit highly dissimilar conformations, geometrical shapes, amphipathicity, and thermodynamic properties which constrain their two-dimensional molecular packing, electrostatics, and interaction preferences. This causes inevitable development of large local tensions that frequently relax into phase or compositional immiscibility along lateral and transverse planes of the membrane. On the other hand, these effects constitute the very codes that mediate molecular and structural changes determining and controlling the possibilities for enzymatic activity, apposition and recombination in biomembranes. The presence of proteins constitutes a major perturbing factor for the membrane sculpturing both in terms of its surface topography and dynamics. We will focus on some results from our group within this context and summarize some recent evidence for the active involvement of extrinsic (myelin basic protein), integral (Folch-Lees proteolipid protein) and amphitropic (c-Fos and c-Jun) proteins, as well as a membrane-active amphitropic phosphohydrolytic enzyme (neutral sphingomyelinase), in the process of lateral segregation and dynamics of phase domains, sculpturing of the surface topography, and the bi-directional modulation of the membrane biochemical reactivity. PMID:16302088

Maggio, B; Rosetti, C M; Borioli, G A; Fanani, M L; Del Boca, M

2005-11-09

157

Hey1, a Mediator of Notch Signaling, Is an Androgen Receptor Corepressor  

Microsoft Academic Search

Hey1 is a member of the basic helix-loop-helix-Orange family of transcriptional repressors that mediate Notch signaling. Here we show that transcription from androgen-dependent target genes is inhibited by Hey1 and that expression of a constitutively active form of Notch is capable of repressing transactivation by the endogenous androgen receptor (AR). Our results indicate that Hey1 functions as a corepressor for

Borja Belandia; Sue M. Powell; J. M. Garcia-Pedrero; Marjorie M. Walker; Charlotte L. Bevan; Malcolm G. Parker

2005-01-01

158

NeuroD-null mice are deaf due to a severe loss of the inner ear sensory neurons during development  

Microsoft Academic Search

A key factor in the genetically programmed development of the nervous system is the death of massive numbers of neurons. Therefore, genetic mechanisms governing cell survival are of fundamental importance to developmental neuroscience. We report that inner ear sensory neurons are dependent on a basic helix-loop-helix transcription factor called NeuroD for survival during differentiation. Mice lacking NeuroD protein exhibit no

Woo-Young Kim; Bernd Fritzsch; Amanda Serls; Leigh Anne Bakel; Eric J. Huang; Louis F. Reichardt; Daniel S. Barth; Jacqueline E. Lee

2001-01-01

159

Proprioceptor Pathway Development Is Dependent on MATH1  

Microsoft Academic Search

The proprioceptive system provides continuous positional information on the limbs and body to the thalamus, cortex, pontine nucleus, and cerebellum. We showed previously that the basic helix-loop-helix transcription factor Math1 is essential for the development of certain components of the proprioceptive pathway, including inner-ear hair cells, cerebellar granule neurons, and the pontine nuclei. Here, we demonstrate that Math1 null embryos

Nessan A. Bermingham; Bassem A. Hassan; Vincent Y. Wang; Michael Fernandez; Sandro Banfi; Hugo J. Bellen; Bernd Fritzsch; Huda Y. Zoghbi

2001-01-01

160

Regulation of the MiTF\\/TFE bHLH-LZ transcription factors through restricted spatial expression and alternative splicing of functional domains  

Microsoft Academic Search

The MiTF\\/TFE (MiT) family of basic helix-loop-helix leucine zipper transcription factors is composed of four closely related members, MiTF, TFE3, TFEB and TFEC, which can bind target DNA both as homo- or heterodimers. Using real-time RT-PCR, we have analyzed the relative expression levels of the four members in a broad range of human tissues, and found that their ratio of

Roland P. Kuiper; Marga Schepens; J. Thijssen; E. F. P. M. Schoenmakers

2004-01-01

161

TWIST inactivation reduces CBFA1\\/RUNX2 expression and DNA binding to the osteocalcin promoter in osteoblasts  

Microsoft Academic Search

The Saethre–Chotzen (SC) syndrome is characterized by increased osteogenesis and premature fusion of cranial sutures, resulting from mutations in TWIST, a basic helix–loop–helix transcription factor. The molecular target genes for Twist in osteoblasts are however unknown. We report here that TWIST haploinsufficiency in mutant osteoblasts reduces mRNA and protein levels for CBFA1\\/RUNX2, a specific osteoblast transcription factor, during both osteoblast

Malika Yousfi; Françoise Lasmoles; Brigitt Kern; Pierre J Marie

2002-01-01

162

Liver X receptors (LXR? and LXR?) are potent regulators for hepatic Dec1 expression  

Microsoft Academic Search

DEC1 (BHLHB2\\/Stra13\\/Sharp2)—a basic helix-loop-helix transcription factor—is known to be involved in various biological phenomena including clock systems and metabolism. In the clock systems, Dec1 expression is dominantly up-regulated by CLOCK : BMAL1 heterodimer, and it exhibits circadian rhythm in the suprachiasmatic nucleus (SCN)—the central circadian pacemaker— and other peripheral tissues. Recent studies have shown that the strong circadian rhythmicity of

Mitsuhide Noshiro; Emiko Usui; Takeshi Kawamoto; Fuyuki Sato; Ayumu Nakashima; Taichi Ueshima; Kiyomasa Honda; Katsumi Fujimoto; Sato Honma; Ken-ichi Honma; Makoto Makishima; Yukio Kato

2009-01-01

163

Drosophila Myc is Oncogenic in Mammalian Cells and Plays a Role in the Diminutive Phenotype  

Microsoft Academic Search

Biochemical and biological activities of Myc oncoproteins are highly dependent upon their association with another basic region helix--loop--helix\\/leucine zipper (bHLH\\/LZ) protein, Max. Our previous observation that the DNA-binding\\/dimerization region of Max is absolutely conserved throughout vertebrate evolution provided the basis for a yeast two-hybrid interaction screen that led to the isolation of the Drosophila Myc (dMyc1) protein. Structural conservation in

Nicole Schreiber-Agus; David Stein; Ken Chen; Jason S. Goltz; Leslie Stevens; Ronald A. Depinho

1997-01-01

164

MondoA-Mlx Heterodimers Are Candidate Sensors of Cellular Energy Status: Mitochondrial Localization and Direct Regulation of Glycolysis  

Microsoft Academic Search

Transcription factors can be sequestered at specific organelles and translocate to the nucleus in response to changes in organellar homeostasis. MondoA is a basic helix-loop-helix leucine zipper transcriptional activator similar to Myc in function. However, unlike Myc, MondoA and its binding partner Mlx localize to the cytoplasm, suggesting tight regulation of their nuclear function. We show here that endogenous MondoA

Christopher L. Sans; Daniel J. Satterwhite; Carrie A. Stoltzman; Kevin T. Breen; Donald E. Ayer

2006-01-01

165

WBSCR14, a gene mapping to the Williams-Beuren syndrome deleted region, is a new member of the Mlx transcription factor network  

Microsoft Academic Search

Williams-Beuren syndrome (WBS) is a develop- mental disorder associated with haploinsufficiency of multiple genes at 7q11.23. Here, we report the functional characterization of WBS critical region gene 14 (WBSCR14), a gene contained in the WBS commonly deleted region. It encodes a basic-helix- loop-helix leucine zipper (bHLHZip) transcription factor of the Myc\\/Max\\/Mad superfamily. WBSCR14 is expressed in multiple tissues, including regions

Stefano Cairo; Giuseppe Merla; Fabrizia Urbinati; Andrea Ballabio; Alexandre Reymond

2001-01-01

166

Achaete-scute homolog-1 linked to remodeling and preneoplasia of pulmonary epithelium  

Microsoft Academic Search

The basic helix–loop–helix protein achaete-scute homolog-1 (ASH1) is involved in lung neuroendocrine (NE) differentiation and tumor promotion in SV40 transgenic mice. Constitutive expression of human ASH-1 (hASH1) in mouse lung results in hyperplasia and remodeling that mimics bronchiolization of alveoli (BOA), a potentially premalignant lesion of human lung carcinomas. We now show that this is due to sustained cellular proliferation

Xiao-Yang Wang; El Habib Dakir; Xu Naizhen; Sandra M Jensen-Taubman; Francesco J DeMayo; R Ilona Linnoila

2007-01-01

167

ITF-2, a downstream target of the Wnt\\/TCF pathway, is activated in human cancers with ?-catenin defects and promotes neoplastic transformation  

Microsoft Academic Search

In many cancers, inactivation of the adenomatous polyposis coli (APC) or Axin tumor suppressor proteins or activating mutations in ?-catenin lead to elevated ?-catenin levels, enhanced binding of ?-catenin to T cell factor (TCF) proteins, and increased expression of TCF-regulated genes. We found that the gene for the basic helix-loop-helix transcription factor ITF-2 (immunoglobulin transcription factor-2) was activated in rat

Frank T. Kolligs; Marvin T. Nieman; Ira Winer; Gang Hu; David Van Mater; Ying Feng; Ian M. Smith; Rong Wu; Yali Zhai; Kathleen R. Cho; Eric R. Fearon

2002-01-01

168

ASH1 Gene Is a Specific Therapeutic Target for Lung Cancers with Neuroendocrine Features  

Microsoft Academic Search

Lung cancers with neuroendocrine features are usually aggressive, although the underlying molecular mechanisms largely remain to be determined. The basic helix-loop-helix protein, achaete-scute complex-like 1\\/achaete-scute homo- logue 1 (ASH1), is expressed in normal fetal pulmonary neuroendocrine cells and lung cancers with neuroendocrine elements and is suggested to be involved in lung carcinogen- esis. In the present study, we show inhibition

Hirotaka Osada; Yoshio Tatematsu; Yasushi Yatabe; Yoshitsugu Horio; Takashi Takahashi

169

Studies on the transcriptional regulation of the proneural phox2a gene during neural crest cell development  

Microsoft Academic Search

Neural crest cells (NCCs) differentiate as neurons, glia, melanocytes, and craniofacial-mesenchymal derivatives. This study emphasizes NCCs of the embryonic trunk region, differentiating as melanocytes, sensory neurons, and sympathoadrenal (SA) cells. cAMP and bone morphogenic proteins (BMPs) are crucial signaling molecules for SA cell development. BMPs induce basic helix-loop-helix (bHLH) transcription factor ASH1, inducing homeodomain (HD) transcription factor Phox2a, required for

Chutamas Benjanirut

2005-01-01

170

Roles of Achaete-Scute Homologue 1 in DKK1 and E-cadherin Repression and Neuroendocrine Differentiation in Lung Cancer  

Microsoft Academic Search

The proneural basic-helix-loop-helix protein achaete-scute homologue 1 (ASH1) is expressed in a very limited spectrum of normal and cancerous cells in a lineage-specific manner, including normal pulmonary neuroendocrine cells and lung cancer cells with neuroendocrine features.Our previous results indicated that ASH1 may play a crucial role in the growth and survival of lung cancers with neuroendocrine features, which prompted us

Hirotaka Osada; Shuta Tomida; Yasushi Yatabe; Yoshio Tatematsu; Toshiyuki Takeuchi; Hideki Murakami; Yutaka Kondo; Yoshitaka Sekido; Takashi Takahashi

2008-01-01

171

SHARP1\\/DEC2 inhibits adipogenic differentiation by regulating the activity of C\\/EBP  

Microsoft Academic Search

SHARP1, a basic helix–loop–helix transcription factor, is expressed in many cell types; however, the mechanisms by which it regulates cellular differentiation remain largely unknown. Here, we show that SHARP1 negatively regulates adipogenesis. Although expression of the early marker CCAAT\\/enhancer binding protein ? (C\\/EBP?) is not altered, its crucial downstream targets C\\/EBP? and peroxisome proliferator-activated receptor ? (PPAR?) are downregulated by

Neriman Tuba Gulbagci; Li Li; Belinda Ling; Suma Gopinadhan; Martin Walsh; Moritz Rossner; Klaus-Armin Nave; Reshma Taneja

2008-01-01

172

Twist1 Directly Regulates Genes That Promote Cell Proliferation and Migration in Developing Heart Valves  

Microsoft Academic Search

Twist1, a basic helix-loop-helix transcription factor, is expressed in mesenchymal precursor populations during embryogenesis and in metastatic cancer cells. In the developing heart, Twist1 is highly expressed in endocardial cushion (ECC) valve mesenchymal cells and is down regulated during valve differentiation and remodeling. Previous studies demonstrated that Twist1 promotes cell proliferation, migration, and expression of primitive extracellular matrix (ECM) molecules

Mary P. Lee; Katherine E. Yutzey

2011-01-01

173

An absence of Twist1 results in aberrant cardiac neural crest morphogenesis  

Microsoft Academic Search

The basic helix–loop–helix transcription factor Twist1 plays an essential role in mesenchymal cell populations during embryonic development and in pathological disease. Remodeling of the cardiac outflow tract (OFT) into the functionally separate aortic arch and pulmonary trunk is dependent upon the dynamic, coordinated contribution of multiple mesenchymal cell populations. Here, we report that Twist1?\\/? mice exhibit OFTs that contain amorphic

Joshua W. Vincentz; Ralston M. Barnes; Rhonda Rodgers; Beth A. Firulli; Simon J. Conway; Anthony B. Firulli

2008-01-01

174

Neurogenin 1 mediates erythropoietin enhanced differentiation of adult neural progenitor cells  

Microsoft Academic Search

Proneuronal basic helix–loop–helix (bHLH) transcription factor, neurogenin 1 (Ngn1), regulates neuronal differentiation during development of the cerebral cortex. Akt mediates proneuronal bHLH protein function to promote neuronal differentiation. Here, we show that recombinant human erythropoietin (rhEPO) significantly increased Akt activity and Ngn1 mRNA levels in neural progenitor cells derived from the subventricular zone (SVZ) of adult rat, which was coincident

Lei Wang; Zheng G Zhang; Rui L Zhang; Zhong X Jiao; Ying Wang; S Pourabdollah-Nejad D; Yvonne LeTourneau; Sara R Gregg; Michael Chopp

2006-01-01

175

Metastasis-induction and apoptosis-protection by TWIST in gastric cancer cells  

Microsoft Academic Search

TWIST, a basic helix-loop-helix transcription factor, has been recently reported to play an important role in tumorigenesis\\u000a of human cancer through converting the early stage tumors into invasive malignancies. Upregulation of TWIST is often found\\u000a in cancer patients, especially those with shorter survival period and poor response to chemotherapy. Here we studied the functions\\u000a of TWIST on regulating migration rate,

Mei-yan Feng; Kuan Wang; Hong-tao Song; Hong-wei Yu; Yu Qin; Qing-tao Shi; Jing-shu Geng

2009-01-01

176

Characterization of hey bHLH genes in teleost fish  

Microsoft Academic Search

Hairy-related basic helix-loop-helix (bHLH) transcription factors are targets of Delta-Notch signaling and represent essential components for a number of cell fate decisions during vertebrate embryogenesis. Hey genes encode a subfamily of hairy-related proteins that have been implicated in processes like somitogenesis, blood vessel and heart development. We have identified and characterized hey genes in three teleost fish lineages using degenerate

Christoph Winkler; Harun Elmasri; Barbara Klamt; Jean-Nicolas Volff; Manfred Gessler

2003-01-01

177

Zebrafish orthopedia (otp) is required for isotocin cell development  

Microsoft Academic Search

Several behavioral and physiological processes such as social, sexual, and maternal behaviors, learning and memory, and parturition\\u000a are influenced by the neurohypophysial peptide oxytocin. Studies in knockout mice have identified four transcriptional regulatory\\u000a genes that are required for oxytocin neuronal development in the hypothalamus. These are the basic helix-loop-helix PAS genes\\u000a Single-minded 1 (Sim1) and Arylhydrocarbon receptor nuclear translocator 2

Jennifer L. Eaton; Eric Glasgow

2007-01-01

178

Significance of Twist expression and its association with E-cadherin in esophageal squamous cell carcinoma  

Microsoft Academic Search

BACKGROUND: Twist is a basic helix-loop-helix (bHLH) transcriptional factor that has been identified to play an important role in epithelial-mesenchymal transition (EMT)-mediated metastasis through the regulation of E-cadherin expression. However, few authors have examined the expression of Twist and E-cadherin and their prognostic value in patients with esophageal squamous cell carcinoma (ESCC). The purpose of this study is to evaluate

Ken Sasaki; Shoji Natsugoe; Sumiya Ishigami; Masataka Matsumoto; Hiroshi Okumura; Tetsuro Setoyama; Yasuto Uchikado; Yoshiaki Kita; Kiyokazu Tamotsu; Akihiko Sakamoto; Tetsuhiro Owaki; Takashi Aikou

2009-01-01

179

Daughterless dictates Twist activity in a context-dependent manner during somatic myogenesis  

Microsoft Academic Search

Somatic myogenesis in Drosophila relies on the reiterative activity of the basic helix–loop–helix transcriptional regulator, Twist (Twi). How Twi directs multiple cell fate decisions over the course of mesoderm and muscle development is unclear. Previous work has shown that Twi is regulated by its dimerization partner: Twi homodimers activate genes necessary for somatic myogenesis, whereas Twi\\/Daughterless (Da) heterodimers lead to

Ming-Ching Wong; Irinka Castanon; Mary K. Baylies

2008-01-01

180

Upregulation of Twist in Gastric Carcinoma Associated with Tumor Invasion and Poor Prognosis  

Microsoft Academic Search

Tumor invasion and metastasis are the most common causes of death in gastric carcinoma. Twist, a transcription factor of the\\u000a basic helix-loop-helix class, reportedly regulates cancer metastasis and induces epithelial-mesenchymal transition (EMT).\\u000a We evaluated the expression of Twist and its effect on cell migration in gastric carcinoma (GC). Twist expression was detected\\u000a by real-time quantitative RT-PCR in gastric tumor tissue,

Guo-Qing Ru; Hui-Ju Wang; Wen-Jun Xu; Zhong-Sheng Zhao

2011-01-01

181

Twist Expression Predicts Poor Clinical Outcome of Patients with Clear Cell Carcinoma of the Ovary  

Microsoft Academic Search

Objectives: Twist is a highly conserved basic helix-loop-helix transcription factor that regulates the expression of E-cadherin and promotes the epithelial-mesenchymal transition, which is critical for tumor infiltration. We examined the distribution and expression of this molecule in clear cell carcinoma of the ovary (CCC) to elucidate their clinical significance. Methods: Paraffin sections from CCC tissues (n = 27) were immunostained

Hiroaki Kajiyama; Satoyo Hosono; Mikio Terauchi; Kiyosumi Shibata; Kazuhiko Ino; Eiko Yamamoto; Seiji Nomura; Akihiro Nawa; Fumitaka Kikkawa; M. Singh; S. Prasad

2006-01-01

182

Twist expression promotes migration and invasion in hepatocellular carcinoma  

Microsoft Academic Search

BACKGROUND: Twist, a transcription factor of the basic helix-loop-helix class, is reported to regulate cancer metastasis. It is known to induce epithelial-mesenchymal transition (EMT). In this study, we evaluated the expression of twist and its effect on cell migration in hepatocellular carcinoma (HCC). METHODS: We examined twist expression using immunohistochemistry in 20 tissue samples of hepatocellular carcinoma, and assessed twist

Noriyuki Matsuo; Hidenori Shiraha; Tatsuya Fujikawa; Nobuyuki Takaoka; Naoki Ueda; Shigetomi Tanaka; Shinichi Nishina; Yutaka Nakanishi; Masayuki Uemura; Akinobu Takaki; Shinichiro Nakamura; Yoshiyuki Kobayashi; Kazuhiro Nouso; Takahito Yagi; Kazuhide Yamamoto

2009-01-01

183

Negative Regulation of atonal in Proneural Cluster Formation of Drosophila R8 Photoreceptors  

Microsoft Academic Search

atonal (ato) encodes a basic helix-loop-helix protein and is required for the specification of R8 photoreceptor cells in Drosophila. In the eye imaginal discs, expression of Ato protein is initially in a dorsoventral stripe of cells anterior to the morphogenetic furrow (MF). In the MF, this stripe expression is resolved into regularly spaced clusters of Ato-positive cells, the proneural clusters,

Chien-Kuo Chen; Cheng-Ting Chien

1999-01-01

184

Evolutionary conservation of sequence and expression of the bHLH protein Atonal suggests a conserved role in neurogenesis  

Microsoft Academic Search

atonal is a Drosophila proneural gene that belongs to the family of basic helix-loop-helix (bHLH)- containing proteins. It is expressed in the chordotonal organs and photoreceptor cells, and flies that lack Atonal protein are ataxic and blind. Here we report the cloning of atonal homologs from red flour beetle, puffer fish, chicken, mouse, and human. The bHLH domain is conserved

Nissim Ben-Arie; Alanna E. McCall; Scott Berkman; Gregor Eichele; Hugo J. Bellen; Huda Y. Zoghbi

1996-01-01

185

Evolution of proneural atonal expression during distinct regulatory phases in the developing Drosophila eye  

Microsoft Academic Search

Background Receptors of the Notch family affect the determination of many cell types. In the Drosophila eye, Notch antagonises the basic helix–loop–helix (bHLH) protein atonal, which is required for R8 photoreceptor determination. Similar antagonism between Notch and proneural bHLH proteins regulates most neural cell determination, however, it is uncertain whether the mechanisms are similar in all cases. Here, we have

Nicholas E. Baker; Sung Yu; Doreen Han

1996-01-01

186

Genetic Mapping of Four Mouse bHLH Genes Related to DrosophilaProneural Gene atonal  

Microsoft Academic Search

It has been shown that mammalian neurogenesis is partly controlled by multiple basic helix–loop–helix (bHLH) genes, as inDrosophila.Recently, mouse homologs ofDrosophila atonal,a proneural gene encoding a bHLH protein required for chordotonal organ and photoreceptor development, have been characterized to obtain further insights into the molecular nature of mammalian neurogenesis. Here, to assess their potential involvement in genetic neural disorders, we

Fumiaki Isaka; Chikara Shimizu; Shigetada Nakanishi; Ryoichiro Kageyama

1996-01-01

187

Atonal homolog 1 Is a Tumor Suppressor Gene  

Microsoft Academic Search

Colon cancer accounts for more than 10% of all cancer deaths annually. Our genetic evidence from Drosophila and previous in vitro studies of mammalian Atonal homolog 1 (Atoh1, also called Math1 or Hath1) suggest an anti- oncogenic function for the Atonal group of proneural basic helix-loop-helix transcription factors. We asked whether mouse Atoh1 and human ATOH1 act as tumor suppressor

Wouter Bossuyt; Avedis Kazanjian; Natalie De Geest; Sofie Van Kelst; Gert De Hertogh; Karel Geboes; Greg P. Boivin; Judith Luciani; Francois Fuks; Marinee Chuah; Thierry VandenDriessche; Peter Marynen; Jan Cools; Noah F. Shroyer; Bassem A. Hassan

2009-01-01

188

E-box mutations in the RAPSN promoter region in eight cases with congenital myasthenic syndrome  

Microsoft Academic Search

Myogenic determination factors are basic helix-loop-helix proteins that govern specification and differentiation of muscle cells, and bind to the E-box consensus sequence CANNTG in promoter regions of muscle-specific genes. No E-box mutation has been reported to date. RAPSN encodes rapsyn, a 43 kDa postsynaptic peripheral membrane protein that clusters the nicotinic acetylcholine receptor at the motor endplate. Transcriptional regulation mechanisms

Kinji Ohno; Menachem Sadeh; Ilan Blatt; Joan M. Brengman; Andrew G. Engel

2003-01-01

189

TFE3 transcriptionally activates hepatic IRS-2, participates in insulin signaling and ameliorates diabetes  

Microsoft Academic Search

Using an expression cloning strategy, we have identified TFE3, a basic helix-loop-helix protein, as a transactivator of metabolic genes that are regulated through an E-box in their promoters. Adenovirus-mediated expression of TFE3 in hepatocytes in culture and in vivo strongly activated expression of IRS-2 and Akt and enhanced phosphorylation of insulin-signaling kinases such as Akt, glycogen synthase kinase 3? and

Yoshimi Nakagawa; Tomohiro Yoshikawa; Tomohiro Ide; Mariko Tamura; Mika Furusawa; Takashi Yamamoto; Noriyuki Inoue; Takashi Matsuzaka; Akimitsu Takahashi; Alyssa H Hasty; Hiroaki Suzuki; Hirohito Sone; Hideo Toyoshima; Naoya Yahagi; Nobuhiro Yamada; Hitoshi Shimano

2005-01-01

190

The bHLH Protein, MUTE, Controls Differentiation of Stomata and the Hydathode Pore in Arabidopsis  

Microsoft Academic Search

Stomata are turgor-driven epidermal valves on the surface of plants that allow for efficient gas and water exchange between the plant and its environment. The Arabidopsis thaliana basic helix-loop-helix (bHLH) protein, MUTE, is a master regulator of stomatal differentiation where it is required for progression through the stomatal lineage and the differentiation of stomata. The genetic control of stomatal spacing

Lynn Jo Pillitteri; Naomi L. Bogenschutz; Keiko U. Torii

2008-01-01

191

The bHLH\\/Per-Arnt-Sim transcription factor SIM2 regulates muscle transcript myomesin2 via a novel, non-canonical E-box sequence  

Microsoft Academic Search

Despite a growing number of descriptive studies that show Single-minded 2 (Sim2) is not only essential for murine survival, but also upregulated in colon, prostate and pancreatic tumours, there is a lack of direct target genes identified for this basic helix-loop-helix\\/PAS transcription factor. We have performed a set of microarray experiments aimed at identifying genes that are differentially regulated by

Susan Woods; Alexandra Farrall; Carl Procko; Murray L. Whitelaw

2008-01-01

192

Regulation of Skeletal Muscle Sarcomere Integrity and Postnatal Muscle Function by Mef2c  

Microsoft Academic Search

Myocyte enhancer factor 2 (MEF2) transcription factors cooperate with the MyoD family of basic helix- loop-helix (bHLH) transcription factors to drive skeletal muscle development during embryogenesis, but little is known about the potential functions of MEF2 factors in postnatal skeletal muscle. Here we show that skeletal muscle-specific deletion of Mef2c in mice results in disorganized myofibers and perinatal lethality. In

Matthew J. Potthoff; Michael A. Arnold; John McAnally; James A. Richardson; Rhonda Bassel-Duby; Eric N. Olson

2007-01-01

193

Degradation of Id2 by the anaphase-promoting complex couples cell cycle exit and axonal growth  

Microsoft Academic Search

In the developing nervous system, Id2 (inhibitor of DNA binding 2, also known as inhibitor of differentiation 2) enhances cell proliferation, promotes tumour progression and inhibits the activity of neurogenic basic helix-loop-helix (bHLH) transcription factors. The anaphase promoting complex\\/cyclosome and its activator Cdh1 (APC\\/CCdh1) restrains axonal growth but the targets of APC\\/CCdh1 in neurons are unknown. Id2 and other members

Anna Lasorella; Judith Stegmüller; Daniele Guardavaccaro; Guangchao Liu; Maria S. Carro; Gerson Rothschild; Luis de La Torre-Ubieta; Michele Pagano; Azad Bonni; Antonio Iavarone

2006-01-01

194

Multiple phosphorylation events control mitotic degradation of the muscle transcription factor Myf5  

Microsoft Academic Search

BACKGROUND: The two myogenic regulatory factors Myf5 and MyoD are basic helix-loop-helix muscle transcription factors undergoing differential cell cycle dependent proteolysis in proliferating myoblasts. This regulated degradation results in the striking expression of these two factors at distinct phases of the cell cycle, and suggests that their precise and alternated disappearance is an important feature of myoblasts, maybe connected to

Christine Doucet; Gustavo J Gutierrez; Catherine Lindon; Thierry Lorca; Gwendaline Lledo; Christian Pinset; Olivier Coux

2005-01-01

195

Centromere promoter factors (CPF1) of the yeasts Saccharomyces cerevisiae and Kluyveromyces lactis are functionally exchangeable, despite low overall homology  

Microsoft Academic Search

The KlCPF1 gene, coding for the centromere and promoter factor CPF1 from Kluyveromyces lactis, has been cloned by functional complementation of the methionine auxotrophic phenotype of a Saccharomyces cerevisiae mutant lacking ScCPF1. The amino-acid sequences of both CPF1 proteins show a relatively-low overall identity (31%), but a highly-homologous C-terminal domain (86%). This region constitutes the DNA-binding domain with basic-helix-loop-helix and

Wietse Mulder; Aaron A. Winkler; Inge H. J. M. Scholten; Ben J. M. Zonneveld; Johannes H. Winde; H. Yde Steensma; Leslie A. Grivell

1994-01-01

196

Pathways mediating the effects of cannabidiol on the reduction of breast cancer cell proliferation, invasion, and metastasis  

Microsoft Academic Search

Invasion and metastasis of aggressive breast cancer cells are the final and fatal steps during cancer progression. Clinically,\\u000a there are still limited therapeutic interventions for aggressive and metastatic breast cancers available. Therefore, effective,\\u000a targeted, and non-toxic therapies are urgently required. Id-1, an inhibitor of basic helix-loop-helix transcription factors,\\u000a has recently been shown to be a key regulator of the metastatic

Sean D. McAllister; Ryuichi Murase; Rigel T. Christian; Darryl Lau; Anne J. Zielinski; Juanita Allison; Carolina Almanza; Arash Pakdel; Jasmine Lee; Chandani Limbad; Yong Liu; Robert J. Debs; Dan H. Moore; Pierre-Yves Desprez

2011-01-01

197

Twist2 Controls Myeloid Lineage Development and Function  

Microsoft Academic Search

Basic helix-loop-helix (bHLH) transcription factors play critical roles in lymphoid and erythroid development; however, little is known about their role in myeloid lineage development. In this study, we identify the bHLH transcription factor Twist-2 as a key negative regulator of myeloid lineage development, as manifested by marked increases in mature myeloid populations of macrophages, neutrophils, and basophils in Twist-2–deficient mice.

Andrew B Sharabi; Melissa Aldrich; Drazen Sosic; Eric N Olson; Alan D Friedman; Sung-Hyung Lee; Si-Yi Chen

2008-01-01

198

Iron assimilation and transcription factor controlled synthesis of riboflavin in plants  

Microsoft Academic Search

Iron homeostasis is vital for many cellular processes and requires a precise regulation. Several iron efficient plants respond\\u000a to iron starvation with the excretion of riboflavin and other flavins. Basic helix–loop–helix transcription factors (TF) are\\u000a involved in the regulation of many developmental processes, including iron assimilation. Here we describe the isolation and\\u000a characterisation of two Arabidopsis bHLH TF genes, which

A. Vorwieger; C. Gryczka; A. Czihal; D. Douchkov; J. Tiedemann; H.-P. Mock; M. Jakoby; B. Weisshaar; I. Saalbach; H. Bäumlein

2007-01-01

199

Lyl1 interacts with CREB1 and alters expression of CREB1 target genes  

Microsoft Academic Search

The basic helix-loop-helix (bHLH) transcription factor family contains key regulators of cellular proliferation and differentiation as well as the suspected oncoproteins Tal1 and Lyl1. Tal1 and Lyl1 are aberrantly over-expressed in leukemia as a result of chromosomal translocations, or other genetic or epigenetic events. Protein-protein and protein-DNA interactions described so far are mediated by their highly homologous bHLH domains, while

Serban San-Marina; YouQi Han; Fernando Suarez Saiz; Michael R. Trus; Mark D. Minden

2008-01-01

200

Mechanisms of neuroendocrine differentiation in pulmonary neuroendocrine cells and small cell carcinoma  

Microsoft Academic Search

We review the significance of a network of proneural basic helix-loop-helix (bHLH) factors. Immunohistochemically, pulmonary\\u000a neuroendocrine cells (PNECs) are positive for Mash1, one of the activator bHLHs, and non-PNECs such as Clara cells are positive\\u000a for Hes1, one of the repressor bHLHs. Since mice deficient for the Mash1 gene do not possess PNEC and mice deficient for the Hes1 gene

Takaaki Ito; Naoko Udaka; Kohji Okudela; Takuya Yazawa; Hitoshi Kitamura

2003-01-01

201

Unexpected diversity of aryl hydrocarbon receptors in non-mammalian vertebrates: insights from comparative genomics  

Microsoft Academic Search

Ligand-activated receptors are well-known targets of environmental chemicals that disrupt endocrine signaling. Genomic approaches are providing new opportunities to understand the comparative biology and molecular evolution of these receptors. One example of this is the aryl hydrocarbon receptor (AHR), a basic-helix-loop-helix (bHLH)-Per-Arnt-Sim (PAS) transcription factor through which planar aromatic hydrocarbons cause altered gene expression and toxicity. In contrast to humans

Mark E. Hahn; Sibel I. Karchner; Brad R. Evans; Diana G. Franks; Rebeka R. Merson; Joy M. Lapseritis

2006-01-01

202

The myoD Gene Family: Nodal Point During Specification of the Muscle Cell Lineage  

Microsoft Academic Search

The myoD gene converts many differentiated cell types into muscle. MyoD is a member of the basic-helix-loophelix family of proteins; this 68-amino acid domain in MyoD is necessary and sufficient for myogenesis. MyoD binds cooperatively to muscle-specific enhancers and activates transcription. The helix-loop-helix motif is responsible for dimerization, and, depending on its dimerization partner, MyoD activity can be controlled. MyoD

Harold Weintraub; Robert Davis; Stephen Tapscott; Matthew Thayer; Michael Krause; Robert Benezra; T. Keith Blackwell; David Turner; Ralph Rupp; Stanley Hollenberg; Yuan Zhuang; Andrew Lassar

1991-01-01

203

Glucose-Mediated Transactivation of Carbohydrate Response Element-Binding Protein Requires Cooperative Actions from Mondo Conserved Regions and Essential Trans-Acting Factor 14-3-3  

Microsoft Academic Search

Carbohydrate response element-binding protein (ChREBP) is a basic helix-loop-helix\\/leucine zipper transcription factor that binds to the carbohydrate response element in the promoter of certain lipo- genic and glycolytic genes. High glucose can acti- vate ChREBP by releasing an intramolecular inhi- bition within the glucose-sensing module (GSM) that occurs in low glucose. We report here that the glucose response of GSM

Ming V. Li; Weiqin Chen; Naravat Poungvarin; Minako Imamura; Lawrence Chan

2008-01-01

204

Expression of the inhibitor of DNA-binding (ID)-1 protein as an angiogenic mediator in tumour advancement of uterine cervical cancers  

Microsoft Academic Search

The ID protein, an inhibitor of basic helix-loop-helix (HLH) transcription factors, has been involved in multiple cellular processes. To investigate the association between tumour advancement and ID expressions of uterine cervical cancers, the levels of ID-1, ID-2 and ID-3 mRNAs were determined by real-time reverse transcription-polymerase chain reaction and the histoscore with the localisation of ID-1 was determined by immunohistochemistry

M K Maw; J Fujimoto; T Tamaya

2008-01-01

205

Heterozygous myogenic factor 6 mutation associated with myopathy and severe course of Becker muscular dystrophy  

Microsoft Academic Search

Myogenic factors (MYF) belong to the basic helix-loop-helix (bHLH) transcription factor family and regulate myogenesis and muscle regeneration. The physiological importance of both functions was demonstrated in homozygous Myf knockout mice and mdx mice. Myf5 and Myod are predominantly expressed in proliferating myoblasts while Myf4 and Myf6 are involved in differentiation of myotubes. In a boy with myopathy and an

Birgit Kerst; Detlev Mennerich; Markus Schuelke; Gisela Stoltenburg-Didinger; Arpad von Moers; Reinhart Gossrau; Frank K. H van Landeghem; Astrid Speer; Thomas Braun; Christoph Hübner

2000-01-01

206

Glucocorticoid-enhanced expression of dioxin target genes through regulation of the rat aryl hydrocarbon receptor  

Microsoft Academic Search

The aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR) are ligand-activated transcription factors and members of the basic helix-loop-helix Period-aryl hydrocarbon nuclear translocator-single minded and nuclear hormone receptor superfamilies, respectively. Besides their individual role as acti- vators of specific gene transcription, also interplay between both transcription factors can be an important mechanism of regula- tion. In this study, we report

Edwin Sonneveld; Arjen Jonas; Onno C. Meijer; Abraham Brouwer; Bart van der Burg

2007-01-01

207

DNA Binding Specificities and Pairing Rules of the Ah Receptor, ARNT, and SIM Proteins  

Microsoft Academic Search

The Ah receptor (AHR), the Ah receptor nuclear trans- locator protein (ARNT), and single-minded protein (SIM) are members of the basic helix-loop-helix-PAS (bHLH-PAS) family of regulatory proteins. In this study, we examine the DNA half-site recognition and pairing rules for these proteins using oligonucleotide selection- amplification and coprecipitation protocols. Oligonu- cleotide selection-amplification revealed that a variety of bHLH-PAS protein combinations

W. K. Chan; Christopher A. Bradfield

1995-01-01

208

Hypoxia-inducible factor-1? induces Twist expression in tubular epithelial cells subjected to hypoxia, leading to epithelial-to-mesenchymal transition  

Microsoft Academic Search

Epithelial-to-mesenchymal transition (EMT) induced by chronic hypoxia is one of the critical causes of renal fibrosis. Twist, a basic helix-loop-helix transcription factor, is believed to be important in promoting EMT. We found that the expression of Twist was increased in human tubule cell lines (HK-2 and HKC) grown under hypoxic conditions. This was accompanied by reduced expression of the epithelial

Shiren Sun; Xiaoxuan Ning; Yanqi Zhang; Yuanyuan Lu; Yongzhan Nie; Shuang Han; Lili Liu; Rui Du; Lin Xia; Lijie He; Daiming Fan

2009-01-01

209

Suppression of hypoxia-induced HIF-1? accumulation by VEGFR inhibitors: Different profiles of AAL993 versus SU5416 and KRN633  

Microsoft Academic Search

The hypoxia-inducible factor (HIF) is a heterodimeric basic helix-loop-helix transcriptional factor and the activated HIF plays pivotal roles in various pathological conditions, including inflammation and cancer. HIF-1? overexpression has been observed in many common human cancers, including brain, breast, colon, lung, ovary, and prostate, and HIF-mediated genes, such as vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), and

Hyun Seung Ban; Masaharu Uno; Hiroyuki Nakamura

2010-01-01

210

Inducible Expression of Endothelial PAS Domain Protein1 by Hypoxia in Human Lung Adenocarcinoma A549 Cells Role of Src Family Kinases-dependent Pathway  

Microsoft Academic Search

Hypoxia is a potent inducer of tumor angiogenesis, the pro- cess of which is mostly mediated by induction of vascular en- dothelial growth factor (VEGF). In this study, we investigated the effect of hypoxia on the expression of hypoxia-inducible factor-1 ? (HIF-1 ? ) and endothelial PAS domain protein-1 (EPAS1). These two similar but distinct basic helix-loop-helix- PAS proteins have

Mahito Sato; Toru Tanaka; Toshitaka Maeno; Yoshichika Sando; Tatsuo Suga; Yuri Maeno; Hiroko Sato; Ryozo Nagai; Masahiko Kurabayashi

211

Cloning of Hypoxia-Inducible Factor 1? cDNA from Chick Embryonic Ventricular Myocytes  

Microsoft Academic Search

Hypoxia-inducible factor 1 (HIF-1) is composed of HIF-1? and arylhydocarbon nuclear receptor translocator (ARNT), which belong to the basic-helix-loop-helix-Per\\/ARNT\\/Sim (bHLH-PAS) family of transcription factors. HIF plays key roles in oxygen homeostasis and embryonic cardiovascular development. In this study, we have cloned cDNAs encoding the chick HIF-1? from cultured embryonic ventricular myocytes (CEVM) and then examined its expression in various embryonic

Toshiyuki Takahashi; Yasuyuki Sugishita; Takefumi Nojiri; Tatsuya Shimizu; Atsushi Yao; Koh-ichiro Kinugawa; Kazumasa Harada; Ryozo Nagai

2001-01-01

212

Molecular mechanisms for morphogenesis of the central nervous system in mammals  

Microsoft Academic Search

The mammalian central nervous system (CNS) is a highly organized structure. In the beginning of CNS development, neural precursor\\/stem\\u000a cells are dividing in the neuroepithelium. After a while, these precursors gradually start to differentiate into neurons and\\u000a glial cells. Various factors are involved in the proliferation and differentiation of neural precursors. Recent studies have\\u000a demonstrated that the basic helix-loop-helix (bHLH)

Makoto Ishibashi

2004-01-01

213

MASH1 maintains competence for BMP2-induced neuronal differentiation in post-migratory neural crest cells  

Microsoft Academic Search

Background: The interplay between growth factors and transcription factors in vertebrate neurogenesis is poorly understood. MASH1 is a basic helix–loop–helix (bHLH) transcription factor that is essential for autonomic neurogenesis. Bone morphogenetic protein (BMP) 2, and its relative BMP4, have been shown to induce expression of MASH1 and to promote autonomic neuronal differentiation in neural crest stem cells. The relationship between

Liching Lo; Lukas Sommer; David J. Anderson

1997-01-01

214

The leukemic oncogene tal-2 is expressed in the developing mouse brain  

Microsoft Academic Search

tal-1 (T-cell acute leukemia-1; also known as SCL) and tal-2 genes belong to a family of basic helix–loop–helix transcription factors and were originally isolated from the breakpoints of chromosomal translocations in human T-cell leukemia cell lines. tal-1 is expressed not only in hematopoietic cells but also in several endothelial structures and the central nervous system during development. On the other

Seiichi Mori; Seiichi Sugawara; Takayuki Kikuchi; Masahiro Tanji; Osamu Narumi; Anastassia Stoykova; Shin-Ichi Nishikawa; Yoshifumi Yokota

1999-01-01

215

Maintaining cholesterol homeostasis: Sterol regulatory element-binding proteins  

Microsoft Academic Search

The molecular mechanism of how hepatocytes maintain cholesterol homeostasis has become much more transparent with the discovery of sterol regulatory element binding proteins (SREBPs) in recent years. These membrane proteins are members of the basic helix-loop-helix-leucine zipper (bHLH- Zip) family of transcription factors. They activate the expression of at least 30 genes involved in the synthesis of cholesterol and lipids.

Lutz W. Weber; Meinrad Boll; Andreas Stampfl

2004-01-01

216

Spatial Distribution and Function of Sterol Regulatory Element-Binding Protein 1a and 2 Homo and Heterodimers by In Vivo Two-Photon Imaging and Spectroscopy Fluorescence Resonance Energy Transfer  

Microsoft Academic Search

Sterol regulatory element-binding proteins (SREBPs) are a subfamily of basic helix-loop-helix-leucine zipper proteins that regulate lipid metabolism. We show novel evidence of the in vivo occurrence and sub- nuclear spatial localization of both exogenously expressed SREBP-1a and -2 homodimers and heterodimers obtained by two-photon imaging and spectroscopy fluorescence resonance energy transfer. SREBP-1a ho- modimers localize diffusely in the nucleus, whereas

Aikaterini Zoumi; Shrimati Datta; Lih-Huei L. Liaw; Cristen J. Wu; Gopi Manthripragada; Timothy F. Osborne; Vickie J. LaMorte

2005-01-01

217

Cardiac hypertrophy in chronically anemic fetal sheep: Increased vascularization is associated with increased myocardial expression of vascular endothelial growth factor and hypoxia-inducible factor 1  

Microsoft Academic Search

OBJECTIVE: Our purpose was to determine whether the increase in fetal cardiac mass and cardiac output in chronic anemia is accompanied by changes in capillary density or size or changes in levels of vascular endothelial growth factor and hypoxia-inducible factor 1, a basic helix-loop-helix transcription factor that has previously been shown to activate vascular endothelial growth factor gene transcription when

Carolyn Martin; Aimee Y. Yu; Bing-Hua Jiang; Lowell Davis; Dwight Kimberly; A. Roger Hohimer; Gregg L. Semenza

1998-01-01

218

Expression ofSox transcription factors in the developing mouse pancreas  

Microsoft Academic Search

Previous work has identified members of the homeodomain and basic helix-loop-helix families of transcription factors as critical determinants of mammalian pancreatic development. Here, we describe the identification of HMG-box transcription factors of the Sox gene family in the mouse pancreas. We detected transcripts for Sox11, Sox4, Sox13, Sox5, Sox9, Sox8, Sox10, Sox7, Sox17, Sox18, Sox15, and Sox30 in embryonic pancreas

Oleg Lioubinski; Michael Wegner; Maike Sander

2003-01-01

219

Ectopic scute induces Drosophila ommatidia development without R8 founder photoreceptors  

Microsoft Academic Search

During development of the Drosophila peripheral nervous system, different proneural genes encoding basic helix-loop-helix transcription factors are required for different sensory organs to form. atonal (ato) is the proneural gene required for chordotonal organs and R8 photoreceptors, whereas the achaete-scute complex contains proneural genes for external sensory organs such as the macrochaetae, large sensory bristles. Whereas ectopic ato expression induces

Yan Sun; Lily Yeh Jan; Yuh Nung Jan

2000-01-01

220

Transcriptional Link between Blood and Bone: the Stem Cell Leukemia Gene and Its +19 Stem Cell Enhancer Are Active in Bone Cells  

Microsoft Academic Search

Blood and vascular cells are generated during early embryogenesis from a common precursor, the heman- gioblast. The stem cell leukemia gene (SCL\\/tal 1) encodes a basic helix-loop-helix transcription factor that is essential for the normal development of blood progenitors and blood vessels. We have previously characterized a panel of SCL enhancers including the 19 element, which directs expression to hematopoietic

John E. Pimanda; Lev Silberstein; Massimo Dominici; Benjamin Dekel; Mark Bowen; Scott Oldham; Asha Kallianpur; Stephen J. Brandt; David Tannahill; Berthold Gottgens; Anthony R. Green

2006-01-01

221

The transcription factor EPAS-1\\/hypoxia-inducible factor 2 plays an important role in vascular remodeling  

Microsoft Academic Search

We have studied the role of the basic helix-loop-helix-PAS transcription factor EPAS-1\\/hypoxia-inducible factor 2 in vascular development by gene targeting. In ICR\\/129 Sv outbred background, more than half of the mutants displayed varying degrees of vascular disorganization, typically in the yolk sac, and died in utero between embryonic day (E)9.5 and E13.5. In mutant embryos directly derived from EPAS-1\\/ embryonic

Jun Peng; Liyong Zhang; Linsay Drysdale; Guo-Hua Fong

2000-01-01

222

Cortical Thinning and Hydrocephalus in Mice Lacking the Immunoglobulin Superfamily Member CDO  

Microsoft Academic Search

CDO is a cell surface immunoglobulin superfamily member that positively regulates myogenic differentiation in vitro and in vivo and signals to posttranslationally activate myogenic basic helix-loop-helix (bHLH) transcription factors. The Cdo gene is also expressed in the dorsal aspect and midline structures of the developing central nervous system, and mice lacking CDO on the C57BL\\/6 background display holoprosencephaly with 80%

Wei Zhang; Min-Jeong Yi; Xiaoping Chen; Francesca Cole; Robert S. Krauss; Jong-Sun Kang

2006-01-01

223

Anthocyanini of petunia controls pigment synthesis, vacuolar pH, and seed coat development by genetically distinct mechanisms  

Microsoft Academic Search

ANTHOCYANIN1 (AN1) of petunia is a transcription factor of the basic helix-loop-helix (bHLH) family that is required for the synthesis of anthocyanin pigments. Here, we show that AN1 controls additional aspects of cell differentiation: the acidification of vacuoles in petal cells, and the size and morphology of cells in the seed coat epidermis. We identified an1 alleles, formerly known as

Cornelis Spelt; Francesca Quattrocchio; Joseph Mol; Ronald Koes

2002-01-01

224

Molecular characterization and developmental expression of the aryl hydrocarbon receptor from the chick embryo  

Microsoft Academic Search

The aryl hydrocarbon receptor (AhR) was cloned from the chick embryo and its function and developmental expression characterized. Chicken AhR cDNA coded for 858 amino acid protein and 396 bp of 3? UTR. The basic helix–loop–helix domain exhibited 87–100% amino acid identity to avian, mammalian, and amphibian AhR, and 69–74% to piscine AhR. The PAS (Per-ARNT-Sim) region was slightly less

Mary K Walker; Scott E Heid; Susan M Smith; Hollie I Swanson

2000-01-01

225

Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer  

Microsoft Academic Search

Sensory hair cells in the mammalian cochlea convert mechanical stimuli into electrical impulses that subserve audition. Loss of hair cells and their innervating neurons is the most frequent cause of hearing impairment. Atonal homologue 1 (encoded by Atoh1, also known as Math1) is a basic helix-loop-helix transcription factor required for hair-cell development, and its misexpression in vitro and in vivo

Samuel P. Gubbels; David W. Woessner; John C. Mitchell; Anthony J. Ricci; John V. Brigande

2008-01-01

226

The bHLH Gene Hes1 as a Repressor of the Neuronal Commitment of CNS Stem Cells  

Microsoft Academic Search

Hes1 is one of the basic helix-loop-helix transcription factors that regulate mammalian CNS development, and its loss- and gain-of-function phenotypes indicate that it negatively regu- lates neuronal differentiation. Here we report that Hes1 2\\/2 mice expressed both early (TuJ1 and Hu) and late (MAP2 and Neurofilament) neuronal markers prematurely, and that there were approximately twice the normal number of neurons

Yuki Nakamura; Shin-ichi Sakakibara; Takaki Miyata; Masaharu Ogawa; Takuya Shimazaki; Samuel Weiss; Ryoichiro Kageyama; Hideyuki Okano

2000-01-01

227

Launching the T-cell-lineage developmental programme  

Microsoft Academic Search

Multipotent blood progenitor cells enter the thymus and begin a protracted differentiation process in which they gradually acquire T-cell characteristics while shedding their legacy of developmental plasticity. Notch signalling and basic helix-loop-helix E-protein transcription factors collaborate repeatedly to trigger and sustain this process throughout the period leading up to T-cell lineage commitment. Nevertheless, the process is discontinuous with separately regulated

Jonathan E. Moore; Mary A. Yui; Ellen V. Rothenberg

2008-01-01

228

Defects in the cerebella of conditional Neurod1 null mice correlate with effective Tg(Atoh1-cre) recombination and granule cell requirements for Neurod1 for differentiation  

Microsoft Academic Search

Neurod1 is a crucial basic helix-loop-helix gene for most cerebellar granule cells and mediates the differentiation of these cells\\u000a downstream of Atoh1-mediated proliferation of the precursors. In Neurod1 null mice, granule cells die throughout the posterior two thirds of the cerebellar cortex during development. However, Neurod1 is also necessary for pancreatic ?-cell development, and therefore Neurod1 null mice are diabetic,

Ning Pan; Israt Jahan; Jacqueline E. Lee; Bernd Fritzsch

2009-01-01

229

Studies of the SIM1 gene in relation to human obesity and obesity-related traits  

Microsoft Academic Search

Objective:The single-minded 1 (SIM1) is a basic helix–loop–helix transcription factor, which plays a critical role in the development of the paraventricular nucleus (PVN) of the hypothalamus. SIM1-deficient mice have a hypocellular PVN and are severely obese with increased food intake.Design:We examined whether variants in the SIM1 gene might be associated with severe early-onset obesity in humans. Two hundred and seventy-seven

C-C C Hung; J Luan; M Sims; J M Keogh; C Hall; N J Wareham; S O'Rahilly; I S Farooqi

2007-01-01

230

bHLH proteins encoded by the Enhancer of split complex of Drosophila negatively interfere with transcriptional activation mediated by proneural genes  

Microsoft Academic Search

TheEnhancer of split complex [E(SPL)-C] ofDrosophila participates in the control of cell fate choice by uncommitted neuroectodermal cells in the embryo. It encodes seven proteins that belong to the basic helix-loop-helix (bHLH) family, six of which are expressed in very similar patterns in the neuroectoderm. Here we describe experiments aimed at unravelling the molecular basis of their function. We found

Nadja Oellers; Michaela Dehio; Elisabeth Knust

1994-01-01

231

Normal and disease-related biological functions of Twist1 and underlying molecular mechanisms  

Microsoft Academic Search

This article reviews the molecular structure, expression pattern, physiological function, pathological roles and molecular mechanisms of Twist1 in development, genetic disease and cancer. Twist1 is a basic helix-loop-helix domain-containing transcription factor. It forms homo- or hetero-dimers in order to bind the Nde1 E-box element and activate or repress its target genes. During development, Twist1 is essential for mesoderm specification and

Qian Qin; Young Xu; Tao He; Chunlin Qin; Jianming Xu

2012-01-01

232

Hairy Transcriptional Repression Targets and Cofactor Recruitment in Drosophila  

Microsoft Academic Search

Members of the widely conserved Hairy\\/Enhancer of split family of basic Helix-Loop-Helix repressors are essential for proper Drosophila and vertebrate development and are misregulated in many cancers. While a major step forward in understanding the molecular mechanism(s) surrounding Hairy-mediated repression was made with the identification of Groucho, Drosophila C-terminal binding protein (dCtBP), and Drosophila silent information regulator 2 (dSir2) as

Daniella Bianchi-Frias; Amir Orian; Jeffrey J Delrow; Julio Vazquez; Alicia E Rosales-Nieves; Susan M Parkhurst

2004-01-01

233

Arabidopsis CRY2 and ZTL mediate blue-light regulation of the transcription factor CIB1 by distinct mechanisms.  

PubMed

Plants possess multiple photoreceptors to mediate light regulation of growth and development, but it is not well understood how different photoreceptors coordinate their actions to jointly regulate developmental responses, such as flowering time. In Arabidopsis, the photoexcited cryptochrome 2 interacts with the transcription factor CRYPTOCHROME-INTERACTING basic helix-loop-helix 1 (CIB1) to activate transcription and floral initiation. We show that the CIB1 protein expression is regulated by blue light; CIB1 is highly expressed in plants exposed to blue light, but levels of the CIB1 protein decreases in the absence of blue light. We demonstrate that CIB1 is degraded by the 26S proteasome and that blue light suppresses CIB1 degradation. Surprisingly, although cryptochrome 2 physically interacts with CIB1 in response to blue light, it is not the photoreceptor mediating blue-light suppression of CIB1 degradation. Instead, two of the three light-oxygen-voltage (LOV)-domain photoreceptors, ZEITLUPE and LOV KELCH PROTEIN 2, but not FLAVIN-BINDING KELCH REPEAT 1, are required for the function and blue-light suppression of degradation of CIB1. These results support the hypothesis that the evolutionarily unrelated blue-light receptors, cryptochrome and LOV-domain F-box proteins, mediate blue-light regulation of the same transcription factor by distinct mechanisms. PMID:24101505

Liu, Hongtao; Wang, Qin; Liu, Yawen; Zhao, Xiaoying; Imaizumi, Takato; Somers, David E; Tobin, Elaine M; Lin, Chentao

2013-10-07

234

Protein Mediators of Sterol Transport Across Intestinal Brush Border Membrane  

PubMed Central

Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease.

Brown, J. Mark; Yu, Liqing

2012-01-01

235

Morphology, Biophysical Properties and Protein-Mediated Fusion of Archaeosomes  

PubMed Central

As variance from standard phospholipids of eubacteria and eukaryotes, archaebacterial diether phospholipids contain branched alcohol chains (phytanol) linked to glycerol exclusively with ether bonds. Giant vesicles (GVs) constituted of different species of archaebacterial diether phospholipids and glycolipids (archaeosomes) were prepared by electroformation and observed under a phase contrast and/or fluorescence microscope. Archaebacterial lipids and different mixtures of archaebacterial and standard lipids formed GVs which were analysed for size, yield and ability to adhere to each other due to the mediating effects of certain plasma proteins. GVs constituted of different proportions of archaeal or standard phosphatidylcholine were compared. In nonarchaebacterial GVs (in form of multilamellar lipid vesicles, MLVs) the main transition was detected at Tm?=?34. 2°C with an enthalpy of ?H?=?0.68 kcal/mol, whereas in archaebacterial GVs (MLVs) we did not observe the main phase transition in the range between 10 and 70°C. GVs constituted of archaebacterial lipids were subject to attractive interaction mediated by beta 2 glycoprotein I and by heparin. The adhesion constant of beta 2 glycoprotein I – mediated adhesion determined from adhesion angle between adhered GVs was in the range of 10?8 J/m2. In the course of protein mediated adhesion, lateral segregation of the membrane components and presence of thin tubular membranous structures were observed. The ability of archaebacterial diether lipids to combine with standard lipids in bilayers and their compatibility with adhesion-mediating molecules offer further evidence that archaebacterial lipids are appropriate for the design of drug carriers.

Sustar, Vid; Zelko, Jasna; Lopalco, Patrizia; Lobasso, Simona; Ota, Ajda; Ulrih, Natasa Poklar; Corcelli, Angela; Kralj-Iglic, Veronika

2012-01-01

236

Functional analysis of a calcium-binding transcription factor involved in plant salt stress signaling  

Microsoft Academic Search

Calcium is known to serve as a secondary messenger to mediate salt stress signaling pathway. We found a calcium-binding basic\\/helix-loop-helix-type transcription factor (AtNIG1) as a salt stress-responsive gene by using the suppression subtractive hybridization. The AtNIG1 was targeted into nucleus and bound to 45Ca2+, suggesting that AtNIG1 is a nuclear calcium-binding protein. In addition, AtNIG1 bound specifically to the E-box-DNA

Jiyoung Kim; Ho-Young Kim

2006-01-01

237

XATH-1,a Vertebrate Homolog of Drosophila atonal,Induces Neuronal Differentiation within Ectodermal Progenitors  

Microsoft Academic Search

XATH-1,a basic\\/helix-loop-helix transcription factor and a homolog ofDrosophila atonaland mammalianMATH-1,is expressed specifically in the dorsal hindbrain duringXenopusneural development. In order to investigate the role ofXATH-1in the neuronal differentiation process, we have examined the effects ofXATH-1overexpression duringXenopusdevelopment.XATH-1induces the expression of neuronal differentiation markers, such asN-tubulin,within the neural plate as well as within nonneural ectodermal progenitor populations, resulting in the appearance of

Peter Kim; Amy W. Helms; Jane E. Johnson; Kathryn Zimmerman

1997-01-01

238

ETS-Core Binding Factor: a Common Composite Motif in Antigen Receptor Gene Enhancers  

Microsoft Academic Search

A tripartite domain of the murine immunoglobulin m heavy-chain enhancer contains the mA and mB ele- ments that bind ETS proteins and the mE3 element that binds leucine zipper-containing basic helix-loop-helix (bHLH-zip) factors. Analysis of the corresponding region of the human m enhancer revealed high conservation of the mA and mB motifs but a striking absence of the mE3 element.

BATU ERMAN; MARTA CORTES; BARBARA S. NIKOLAJCZYK; NANCY A. SPECK; RANJAN SEN

239

A Role of the Aryl Hydrocarbon Receptor in Attenuation of Colitis  

Microsoft Academic Search

Background and Aims  The aryl hydrocarbon receptor (AhR), which is a member of the basic helix-loop-helix\\/Per-Arnt-Sim homology superfamily, plays\\u000a an important role in multiple biological functions, and AhR knockout (AhR KO) animals suffer from a variety of organ disorders\\u000a including a decline in the efficacy of their immune system. In addition, AhR activation is known to aid the maintenance of\\u000a homeostasis

Keisuke FurumatsuShin; Shin Nishiumi; Yuki Kawano; Makoto Ooi; Tomoo Yoshie; Yuuki Shiomi; Hiromu Kutsumi; Hitoshi Ashida; Yoshiaki Fujii-Kuriyama; Takeshi Azuma; Masaru Yoshida

240

Proteins mediating intra- and intercellular transport of lipids and lipid-modified proteins  

Microsoft Academic Search

Proteins mediating intra- and intercellular transport of lipids and lipid-modified proteins In this thesis, I studied the intra- and intercellular transport of lipidic molecules, in particular glycosphingolipids and lipid-modified proteins. The first part focuses on the intracellular transport of glycosphingolipids. They are thought to fulfill a multitude of biological functions, because they display a high diversity in their head group,

S. Neumann

2008-01-01

241

Basic Stamp  

NSDL National Science Digital Library

This site from Parallax, Inc. gives some information about basic stamp microcontrollers. A Basic-Stamp microcontroller is a single-board computer. Parallax makes a variety of controllers; the BASIC Stamp II uses a PIC16C57microchip.

2012-10-12

242

Protein-Mediated Molecular Bridging: A Key Mechanism in Biopolymer Organization  

Microsoft Academic Search

Protein-mediated bridging is ubiquitous and essential for shaping cellular structures in all organisms. Here we dissect this mechanism for a model system: the Histone-like Nucleoid-Structuring protein (H-NS). We present data from two complementary single-molecule assays that probe the H-NS-DNA interaction: a dynamic optical-trap-driven unzipping assay and an equilibrium H-NS-mediated DNA looping scanning force microscopy imaging assay. To quantitatively analyze and

Paul A. Wiggins; Remus Th. Dame; Maarten C. Noom; Gijs J. L. Wuite

2009-01-01

243

Implications of G-Protein-Mediated Ca2+ Channel Inhibition for Neurotransmitter Release and Facilitation  

Microsoft Academic Search

G-protein-mediated inhibition of Ca2+ current is ubiquitous in neurons, and in synaptic terminals it can lead to a reduction in transmitter release (presynaptic inhibition). This type of Ca2+ current inhibition can often be relieved by prepulse depolarization, so the disinhibition of Ca2+ current can combine with Ca2+-dependent mechanisms for activity-induced synaptic facilitation to amplify this form of short-term plasticity. We

Richard Bertram; Matthew Behan

1999-01-01

244

Achaete-scute homologue-1 (ASH1) stimulates migration of lung cancer cells through Cdk5/p35 pathway.  

PubMed

Our previous data suggested that the human basic helix-loop-helix transcription factor achaete-scute homologue-1 (hASH1) may stimulate both proliferation and migration in the lung. In the CNS, cyclin-dependent kinase 5 (Cdk5) and its activator p35 are important for neuronal migration that is regulated by basic helix-loop-helix transcription factors. Cdk5/p35 may also play a role in carcinogenesis. In this study, we found that the neuronal activator p35 was commonly expressed in primary human lung cancers. Cdk5 and p35 were also expressed by several human lung cancer cell lines and coupled with migration and invasion. When the kinase activity was inhibited by the Cdk5 inhibitor roscovitine or dominant-negative (dn) Cdk5, the migration of lung cancer cells was reduced. In neuroendocrine cells expressing hASH1, such as a pulmonary carcinoid cell line, knocking down the gene expression by short hairpin RNA reduced the levels of Cdk5/p35, nuclear p35 protein, and migration. Furthermore, expression of hASH1 in lung adenocarcinoma cells normally lacking hASH1 increased p35/Cdk5 activity and enhanced cellular migration. We were also able to show that p35 was a direct target for hASH1. In conclusion, induction of Cdk5 activity is a novel mechanism through which hASH1 may regulate migration in lung carcinogenesis. PMID:22696682

Demelash, Abeba; Rudrabhatla, Parvathi; Pant, Harish C; Wang, Xiaoyang; Amin, Niranjana D; McWhite, Claire D; Naizhen, Xu; Linnoila, R Ilona

2012-06-13

245

Achaete-scute homologue-1 (ASH1) stimulates migration of lung cancer cells through Cdk5/p35 pathway  

PubMed Central

Our previous data suggested that the human basic helix–loop–helix transcription factor achaete-scute homologue-1 (hASH1) may stimulate both proliferation and migration in the lung. In the CNS, cyclin-dependent kinase 5 (Cdk5) and its activator p35 are important for neuronal migration that is regulated by basic helix–loop–helix transcription factors. Cdk5/p35 may also play a role in carcinogenesis. In this study, we found that the neuronal activator p35 was commonly expressed in primary human lung cancers. Cdk5 and p35 were also expressed by several human lung cancer cell lines and coupled with migration and invasion. When the kinase activity was inhibited by the Cdk5 inhibitor roscovitine or dominant-negative (dn) Cdk5, the migration of lung cancer cells was reduced. In neuroendocrine cells expressing hASH1, such as a pulmonary carcinoid cell line, knocking down the gene expression by short hairpin RNA reduced the levels of Cdk5/p35, nuclear p35 protein, and migration. Furthermore, expression of hASH1 in lung adenocarcinoma cells normally lacking hASH1 increased p35/Cdk5 activity and enhanced cellular migration. We were also able to show that p35 was a direct target for hASH1. In conclusion, induction of Cdk5 activity is a novel mechanism through which hASH1 may regulate migration in lung carcinogenesis.

Demelash, Abeba; Rudrabhatla, Parvathi; Pant, Harish C.; Wang, Xiaoyang; Amin, Niranjana D.; McWhite, Claire D.; Naizhen, Xu; Linnoila, R. Ilona

2012-01-01

246

Mutations in SOHLH1 gene associate with nonobstructive azoospermia.  

PubMed

In a previous study, we found SOHLH1 (spermatogenesis and oogenesis-specific basic helix-loop-helix 1) as the first testis-specific basic helix-loop-helix transcription factor essential for spermatogonial differentiation. SOHLH1 therefore represents an excellent candidate gene for testicular failure such as nonobstructive azoospermia (NOA). We analyzed whether there were mutations in the SOHLH1 gene in 96 Korean patients with NOA. The sequence analysis discovered three novel variations: one intronic variant (c.346-1G>A), and two nonsynonymous exonic variants (c.91T>C and c.529C>A) with known single nucleotide polymorphisms (SNPs), which included six intronic variants, two synonymous, and two nonsynonymous variants. We examined the consequences of mutations in SOHLH1 using in vivo and in vitro assays. Analysis of transcripts from minigenes carrying the c.346-1G>A revealed that splicing site variation leads to the partial deletion at a cryptic splicing site within exon 4. This deletion results in SOHLH1 with a truncated bHLH domain. Transient transfection assay showed that the SOHLH1 mutant with the truncated domain disrupted the transcriptional activity of KIT promoter, whereas two missense mutations harboring either p.Arg37Gln or p.Pro269Ser did not have a significant effect on its transactivation. Our findings indicate that a splice-acceptor site mutation that probably causes a nonfunctional SOHLH1 protein results in nonobstructive azoospermia by the lack of normal spermatogenesis. PMID:20506135

Choi, Youngsok; Jeon, Sanghyun; Choi, Mikyung; Lee, Min-ho; Park, Miseon; Lee, Dong Ryul; Jun, Kyu-Yeon; Kwon, Youngjoo; Lee, Ok-Hee; Song, Seung-Hun; Kim, Ji-Young; Lee, Kyung-Ah; Yoon, Tae Ki; Rajkovic, Aleksandar; Shim, Sung Han

2010-07-01

247

Hypoxia-inducible factor-1alpha induces Twist expression in tubular epithelial cells subjected to hypoxia, leading to epithelial-to-mesenchymal transition.  

PubMed

Epithelial-to-mesenchymal transition (EMT) induced by chronic hypoxia is one of the critical causes of renal fibrosis. Twist, a basic helix-loop-helix transcription factor, is believed to be important in promoting EMT. We found that the expression of Twist was increased in human tubule cell lines (HK-2 and HKC) grown under hypoxic conditions. This was accompanied by reduced expression of the epithelial markers E-cadherin and ZO-1 and enhanced expression of the mesenchymal markers vimentin and alpha-smooth muscle actin. When Twist was overexpressed in these cells it induced a mesenchymal phenotype, whereas its knockdown by short interfering RNA (siRNA) effectively reversed hypoxia-induced EMT. We showed that transfection with siRNA to hypoxia-inducible factor-1alpha (HIF-1alpha), another basic helix-loop-helix transcription factor, reduced Twist expression. Twist promoters contain HIF1-alpha-binding sites and transfection of reporter constructs using the promoter showed increased transcription in cells subjected to hypoxia. Electrophoretic mobility shift and chromatin immunoprecipitation assays identified the presence of a functional HIF-1alpha-binding site within the proximal Twist gene promoter. In an in vivo assay using the rat remnant kidney we found that both Twist and HIF-1alpha were overexpressed in tubular epithelial cells showing EMT. These studies suggest that HIF-1alpha induces Twist expression in hypoxic tubular cells and that this plays a role in EMT during renal fibrogenesis. PMID:19279556

Sun, Shiren; Ning, Xiaoxuan; Zhang, Yanqi; Lu, Yuanyuan; Nie, Yongzhan; Han, Shuang; Liu, Lili; Du, Rui; Xia, Lin; He, Lijie; Fan, Daiming

2009-03-11

248

Involvement of ITF2 in the transcriptional regulation of melanogenic genes.  

PubMed

In response to agouti signal protein, melanocytes switch from producing eumelanin to pheomelanin concomitant with the down-regulation of melanogenic gene transcription. We previously reported that a ubiquitous basic helix-loop-helix transcription factor, known as ITF2, is up-regulated during this switch, and we now report that treatment of melanocytes with melanocyte-stimulating hormone down-regulates expression of ITF2. To more fully characterize the involvement of ITF2 in regulating melanogenic gene transcription, ITF2 sense or antisense constructs were introduced into melan-a melanocytes. Gene and protein expression analyses and luciferase reporter assays using promoters from melanogenic genes showed that up-regulation of ITF2 suppressed melanogenic gene expression as well as the expression of Mitf, a melanocyte-specific transcription factor. In addition, stable ITF2 sense transfectants had significant reductions in pigmentation and a less dendritic phenotype compared with mock transfectants. In contrast, ITF2 antisense-transfected melanocytes were more pigmented and more dendritic. These results demonstrate that up-regulation of ITF2 during the pheomelanin switch is functionally significant and reveal that differential expression of a ubiquitous basic helix-loop-helix transcription factor can modulate expression of melanogenic genes and the differentiation of melanocytes. PMID:11382753

Furumura, M; Potterf, S B; Toyofuku, K; Matsunaga, J; Muller, J; Hearing, V J

2001-05-29

249

Menopause Basics  

MedlinePLUS

... Complimentary Materials Media Award Recipients Media Policy NAMS Advertisements NAMS in the News Press Releases Press Room Assistance Society Overview FAQs: Menopause Basics Home > For Women > Expert Answers > FAQs: Menopause Basics Do you have ...

250

Body Basics  

MedlinePLUS

... Vaccine: How Many Doses? Connect With Us: Social Media Pregnant? Your Baby's Growth About Body Basics KidsHealth > Parents > General Health > Body Basics > About Body Basics Print A A A Text Size Remember the biology class you had in high school? Well, even if you do, lots of new ...

251

Cdk2-dependent phosphorylation of Id2 modulates activity of E2A-related transcription factors.  

PubMed Central

The helix-loop-helix (HLH) protein Id2 is thought to affect the balance between cell growth and differentiation by negatively regulating the function of basic-helix-loop-helix (bHLH) transcription factors. Id2 acts by forming heterodimers that are unable to bind to specific (E-box) DNA sequences. Here we show that this activity can be overcome by phosphorylation of a serine residue within a consensus target site for cyclin-dependent kinases (Cdks). In vitro, Id2 can be phosphorylated by either cyclin E-Cdk2 or cyclin A-Cdk2 but not by cyclin D-dependent kinases. Analogous phosphorylation occurs in serum-stimulated human diploid fibroblasts at a time in late G1 consistent with the appearance of active cyclin E-Cdk2. The phosphorylation of Id2 in these cells correlates with the restoration of a distinct E-box-dependent DNA-binding complex, suggesting that the levels of this complex are modulated by both the abundance and phosphorylation status of Id2. These data provide a link between cyclin-dependent kinases and bHLH transcription factors that may be critical for the regulation of cell proliferation and differentiation.

Hara, E; Hall, M; Peters, G

1997-01-01

252

Protein-mediated molecular bridging: a key mechanism in biopolymer organization.  

PubMed

Protein-mediated bridging is ubiquitous and essential for shaping cellular structures in all organisms. Here we dissect this mechanism for a model system: the Histone-like Nucleoid-Structuring protein (H-NS). We present data from two complementary single-molecule assays that probe the H-NS-DNA interaction: a dynamic optical-trap-driven unzipping assay and an equilibrium H-NS-mediated DNA looping scanning force microscopy imaging assay. To quantitatively analyze and compare these assays, we employ what we consider a novel theoretical framework that describes the bridging motif. The interplay between the experiments and our theoretical model not only infers the effective interaction free energy, the bridging conformation and the duplex-duplex spacing, but also reveals a second, unresolved, cis-binding mode that challenges our current understanding of the role of bridging proteins in chromatin structure. We expect that this theoretical framework for describing protein-mediated bridging will be applicable to proteins acting in chromatin and cytoskeletal organization. PMID:19804731

Wiggins, Paul A; Dame, Remus Th; Noom, Maarten C; Wuite, Gijs J L

2009-10-01

253

Protein-Mediated Molecular Bridging: A Key Mechanism in Biopolymer Organization  

PubMed Central

Abstract Protein-mediated bridging is ubiquitous and essential for shaping cellular structures in all organisms. Here we dissect this mechanism for a model system: the Histone-like Nucleoid-Structuring protein (H-NS). We present data from two complementary single-molecule assays that probe the H-NS-DNA interaction: a dynamic optical-trap-driven unzipping assay and an equilibrium H-NS-mediated DNA looping scanning force microscopy imaging assay. To quantitatively analyze and compare these assays, we employ what we consider a novel theoretical framework that describes the bridging motif. The interplay between the experiments and our theoretical model not only infers the effective interaction free energy, the bridging conformation and the duplex-duplex spacing, but also reveals a second, unresolved, cis-binding mode that challenges our current understanding of the role of bridging proteins in chromatin structure. We expect that this theoretical framework for describing protein-mediated bridging will be applicable to proteins acting in chromatin and cytoskeletal organization.

Wiggins, Paul A.; Dame, Remus Th.; Noom, Maarten C.; Wuite, Gijs J.L.

2009-01-01

254

Mechanisms and Regulation of Protein-Mediated Cellular Fatty Acid Uptake: Molecular, Biochemical, and Physiological Evidence  

NSDL National Science Digital Library

In recent years, there has been considerable debate as to whether fatty acid is transported into cells or diffuses rapidly into the cell. It now appears that this debate is less strident, as it has been acknowledged recently that evidence supporting passive diffusion as the main mechanism for fatty acid uptake is apparently in error, since "previous reports for rapid flip-flop were based on an incorrect interpretation of the measurements" (79), Because of this (79) and other experiments (78), it has been concluded that "the lipid bilayer portion of biological membranes may present a significant barrier to transport of FFA across cell membranes" (36) and that "flip-flop is the rate limiting step for FFA transport across lipid vesicles" (78). Furthermore, "this implies that at least certain biological membranes may require protein-mediated transporters to catalyze the flip-flop step" (78). Since we (13, 27ÃÂ29, 73, 97, 98, 100) and others (32, 45, 54) have previously provided considerable support for the protein-mediated entry of long-chain fatty acids into the cell, especially in metabolically important tissues such as heart and skeletal muscle, we concur with these recent conclusions (36, 78, 79) that (membrane-associated) proteins are involved in cellular fatty acid uptake.

2007-02-01

255

BASIC Programming.  

ERIC Educational Resources Information Center

Designed for use by both secondary- and postsecondary-level business teachers, this curriculum guide consists of 10 units of instructional materials dealing with Beginners All-Purpose Symbol Instruction Code (BASIC) programing. Topics of the individual lessons are numbering BASIC programs and using the PRINT, END, and REM statements; system…

Jennings, Carol Ann

256

Fluoridation Basics  

MedlinePLUS

... to... Añadir en... Favorites Delicious Digg Google Bookmarks Fluoridation Basics On this Page Fluoridation Beginnings Benefits of ... surfaces and prevents cavities from continuing to form. Fluoridation Beginnings In the 1930s, dental scientists documented that ...

257

HaloTag protein-mediated specific labeling of living cells with quantum dots  

SciTech Connect

Quantum dots emerge as an attractive alternative to small molecule fluorophores as fluorescent tags for in vivo cell labeling and imaging. This communication presents a method for specific labeling of live cells using quantum dots. The labeling is mediated by HaloTag protein expressed at the cell surface which forms a stable covalent adduct with its ligand (HaloTag ligand). The labeling can be performed in one single step with quantum dot conjugates that are functionalized with HaloTag ligand, or in two steps with biotinylated HaloTag ligand first and followed by streptavidin coated quantum dots. Live cell fluorescence imaging indicates that the labeling is specific and takes place at the cell surface. This HaloTag protein-mediated cell labeling method should facilitate the application of quantum dots for live cell imaging.

So, Min-kyung; Yao Hequan [Biophysics, Cancer Biology, and Molecular Imaging Programs, Department of Radiology, Stanford University School of Medicine, 1201 Welch Road, P093, Mail code 5484, Stanford, CA 94305 (United States); Rao Jianghong [Biophysics, Cancer Biology, and Molecular Imaging Programs, Department of Radiology, Stanford University School of Medicine, 1201 Welch Road, P093, Mail code 5484, Stanford, CA 94305 (United States)], E-mail: jrao@stanford.edu

2008-09-26

258

Small Protein-Mediated Quorum Sensing in a Gram-Negative Bacterium  

PubMed Central

The rice XA21 pattern recognition receptor binds a type I secreted sulfated peptide, called axYS22, derived from the Ax21 (activator of XA21-mediated immunity) protein. The conservation of Ax21 in all sequenced Xanthomonas spp. and closely related genera suggests that Ax21 serves a key biological function. Here we show that the predicted N-terminal sequence of Ax21 is cleaved prior to secretion outside the cell and that mature Ax21 serves as a quorum sensing (QS) factor in Xanthomonas oryzae pv. oryzae. Ax21-mediated QS controls motility, biofilm formation and virulence. We provide genetic evidence that the Xoo RaxH histidine kinase serves as the bacterial receptor for Ax21. This work establishes a critical role for small protein-mediated QS in a Gram-negative bacterium.

Sharma, Manoj; Bahar, Ofir; Bower, Zachary; Ronald, Pamela C.

2011-01-01

259

A conserved motif in Argonaute-interacting proteins mediates functional interactions through the Argonaute PIWI domain.  

PubMed

Argonaute (Ago) proteins mediate silencing of nucleic acid targets by small RNAs. In fission yeast, Ago1, Tas3 and Chp1 assemble into a RITS complex, which silences transcription near centromeres. Here we describe a repetitive motif within Tas3, termed the 'Argonaute hook', that is conserved from yeast to humans and binds Ago proteins through their PIWI domains in vitro and in vivo. Site-directed mutation of key residues in the motif disrupts Ago binding and heterochromatic silencing in vivo. Unexpectedly, a PIWI domain pocket that binds the 5' end of the short interfering RNA guide strand is required for direct binding of the Ago hook. Moreover, wild-type but not mutant Ago hook peptides derepress microRNA-mediated translational silencing of a target messenger RNA. Proteins containing the conserved Ago hook may thus be important regulatory components of effector complexes in RNA interference. PMID:17891150

Till, Susanne; Lejeune, Erwan; Thermann, Rolf; Bortfeld, Miriam; Hothorn, Michael; Enderle, Daniel; Heinrich, Constanze; Hentze, Matthias W; Ladurner, Andreas G

2007-09-23

260

Dispersion Basics  

NSDL National Science Digital Library

In this Webcast, Dr. Timothy Spangler (Director of the COMET Program and a former air quality consultant) provides a brief overview of the basics of atmospheric dispersion and how dispersion is modeled, particularly for accidental releases of hazardous materials. The lecture is presented in six sections and covers the effects of stability, turbulence, plume rise, and wind. Basic dispersion models are discussed, along with a brief summary of models used in special situations and factors that complicate their use.

Spangler, Tim

2002-11-01

261

DOS basics  

SciTech Connect

DOS is an acronym for Disk Operating System. It is actually a set of programs that allows you to control your personal computer. DOS offers the capabilities to create and manage files; organize and maintain information placed on disks; use application programs such as WordPerfect, Lotus 123, Excel, Windows, etc. In addition, DOS provides the basic utilities needed to copy files from one area to another, delete files and list files. The latest version of DOS also offers more advanced features that include hard disk compression and memory management. Basic DOS commands are discussed.

O`Connor, P.

1994-09-01

262

Long-chain fatty acid transport in bacteria andyeast. Paradigms for defining the mechanism underlying this protein-mediated process  

Microsoft Academic Search

Protein-mediated transport of exogenous long-chain fatty acids across the membrane has been defined in a number of different systems. Central to understanding the mechanism underlying this process is the development of the appropriate experimental systems which can be manipulated using the tools of molecular genetics. Escherichia coli and Saccharomyces cerevisiae are ideally suited as model systems to study this process

Concetta C. DiRusso; Paul N. Black

1999-01-01

263

Basic Skills.  

ERIC Educational Resources Information Center

These four articles focus on developing basic reading, science, and job search skills: "Reading Program for Vocational Classes" by Augustus Luparelli; "Why Teach Employability Skills?" by Larry Siefferman; "Improving Vocabulary and Reading Skills" by Edythe Conway; and "Science in Everyday Life" by Virginia Eleazer and George Carney. (SK)

Luparelli, Augustus N.; And Others

1981-01-01

264

Basic hydrodynamics  

Microsoft Academic Search

Basic hydrodynamic studies in turbomachinery and hydrodynamic drag reduction have been conducted. In the turbomachinery thrust area, the overall objective is to develop an improved understanding of the complex three-dimensional flows typical of incompressible rotor and stator flows; this effort has been primarily computational in nature. The second thrust area is axisymmetric turbulent flow drag reduction through microbubble injections. The

G. C. Lauchle

1991-01-01

265

Contour Basics  

NSDL National Science Digital Library

Contour Basics is an exercise designed to introduce students to contour plots. The Contour Activity is a great on-line resource that starts slowly and increases in difficulty. It teaches students basic techniques for generating contours, introduces students to the subtleties of generating contour plots with sparse data, provides many opportunities for students to assess their own progress and understanding and has complete on-line drawing capabilities. The exercise is geared toward atmospheric and oceanic sciences but is beneficial for all geoscience students. In addition to the exercise, this site includes information on teaching materials, teaching notes and tips, assessment suggestions and additional references. This activity is part of the Starting Point Collection: http://serc.carleton.edu/introgeo/

Whittaker, Tom; Ackerman, Steve; Mackay, R. M.

2011-04-27

266

Basic Immunology  

NSDL National Science Digital Library

Some individuals might blanch at the idea of a "basic" immunology overview, but Professor Vladimir V. Klimov provides just such a resource on this site. As the homepage notes, the site is designed to assist undergraduate students learning about the basics of immunology through essays, images, animations, quizzes, case histories, and external links. Visitors can begin by looking over the "Table of Contents" area, which includes seven complete chapters of information. These chapters include "The Immune Responses", "Effector Activity", and "Functional Organization of the Immune System". While some of the materials on the site require a paid subscription, there's enough free material here to get students on their way to learning more about this field of study.

Klimov, Vladimir V.

267

Rhizobium nod factor signaling. Evidence for a g protein-mediated transduction mechanism  

PubMed Central

Rhizobium nodulation (Nod) factors are lipochitooligosaccharide signals that elicit key symbiotic developmental responses in the host legume root. In this study, we have investigated Nod factor signal transduction in the Medicago root epidermis by using a pharmacological approach in conjunction with transgenic plants expressing the Nod factor-responsive reporter construct pMtENOD12-GUS. Evidence for the participation of heterotrimeric G proteins in Nod factor signaling has come from three complementary observations: (1) the amphiphilic peptides mastoparan and Mas7, known G protein agonists, are able to mimic Nod factor-induced epidermal MtENOD12 expression; (2) growth of plants in nodulation-inhibiting conditions (10 mM NH4NO3) leads to a dramatic reduction in both Nod factor- and mastoparan-elicited gene expression; and (3) bacterial pertussis toxin, a well-characterized G protein antagonist, blocks the activities of both the Nod factor and mastoparan. In addition, we have found that antagonists that interfere with phospholipase C activity (neomycin and U73122) and Ca2+ influx/release (EGTA, La3+, and ruthenium red) block Nod factor/mastoparan activity. Taken together, these results are consistent with a Nod factor signal transduction mechanism involving G protein mediation coupled to the activation of both phosphoinositide and Ca2+ second messenger pathways.

Pingret, JL; Journet, EP; Barker, DG

1998-01-01

268

A cycling cis-Golgi protein mediates endosome-to-Golgi traffic.  

PubMed

Toxins can invade cells by using a direct endosome-to-Golgi endocytic pathway that bypasses late endosomes/prelysosomes. This is also a route used by endogenous proteins, including GPP130, which is an integral membrane protein retrieved via the bypass pathway from endosomes to its steady-state location in the cis-Golgi. An RNA interference-based test revealed that GPP130 was required for efficient exit of Shiga toxin B-fragment from endosomes en route to the Golgi apparatus. Furthermore, two proteins whose Golgi targeting depends on endosome-to-Golgi retrieval in the bypass pathway accumulated in early/recycling endosomes in the absence of GPP130. GPP130 activity seemed specific to bypass pathway trafficking because the targeting of other tested proteins, including those retrieved to the Golgi via the more conventional late endosome route, was unaltered. Thus, a distally cycling Golgi protein mediates exit from endosomes and thereby underlies Shiga toxin invasion and retrieval-based targeting of other cycling Golgi proteins. PMID:15331763

Natarajan, Rajalaxmi; Linstedt, Adam D

2004-08-25

269

A Cycling cis-Golgi Protein Mediates Endosome-to-Golgi Traffic  

PubMed Central

Toxins can invade cells by using a direct endosome-to-Golgi endocytic pathway that bypasses late endosomes/prelysosomes. This is also a route used by endogenous proteins, including GPP130, which is an integral membrane protein retrieved via the bypass pathway from endosomes to its steady-state location in the cis-Golgi. An RNA interference-based test revealed that GPP130 was required for efficient exit of Shiga toxin B-fragment from endosomes en route to the Golgi apparatus. Furthermore, two proteins whose Golgi targeting depends on endosome-to-Golgi retrieval in the bypass pathway accumulated in early/recycling endosomes in the absence of GPP130. GPP130 activity seemed specific to bypass pathway trafficking because the targeting of other tested proteins, including those retrieved to the Golgi via the more conventional late endosome route, was unaltered. Thus, a distally cycling Golgi protein mediates exit from endosomes and thereby underlies Shiga toxin invasion and retrieval-based targeting of other cycling Golgi proteins.

Natarajan, Rajalaxmi; Linstedt, Adam D.

2004-01-01

270

Effect of supercoiling on formation of protein-mediated DNA loops.  

PubMed

DNA loop formation is one of several mechanisms used by organisms to regulate genes. The free energy of forming a loop is an important factor in determining whether the associated gene is switched on or off. In this paper we use an elastic rod model of DNA to determine the free energy of forming short (50-100 basepair), protein mediated DNA loops. Superhelical stress in the DNA of living cells is a critical factor determining the energetics of loop formation, and we explicitly account for it in our calculations. The repressor protein itself is regarded as a rigid coupler; its geometry enters the problem through the boundary conditions it applies on the DNA. We show that a theory with these ingredients is sufficient to explain certain features observed in modulation of in vivo gene activity as a function of the distance between operator sites for the lac repressor. We also use our theory to make quantitative predictions for the dependence of looping on superhelical stress, which may be testable both in vivo and in single-molecule experiments such as the tethered particle assay and the magnetic bead assay. PMID:17280096

Purohit, P K; Nelson, P C

2006-12-21

271

Disruption of protein-mediated DNA looping by tension in the substrate DNA.  

PubMed

Protein-mediated DNA looping is important in a variety of biological processes, including gene regulation and genetic transformation. Although the biochemistry of loop formation is well established, the mechanics of loop closure in a constrained cellular environment has received less attention. Recent single molecule measurements show that mechanical constraints have a significant impact on DNA looping and motivate the need for a more comprehensive characterization of the effects of tension. By modeling DNA as a wormlike chain, we calculate how continuous stretching of the substrate DNA affects the loop formation probability. We find that when the loop size is >100 bp, a tension of 500 fN can increase the time required for loop closure by two orders of magnitude. This force is small compared to the piconewton forces that are associated with RNA polymerases and other molecular motors, indicating that intracellular mechanical forces might affect transcriptional regulation. In contrast to existing theory, we find that for loops <200 bp, the effect of tension is partly dependent on the relative orientation of the DNA-binding domains in the linker protein. Our results provide perspective on recent DNA looping experiments and suggestions for future micromechanical studies. PMID:15653717

Blumberg, Seth; Tkachenko, Alexei V; Meiners, Jens-Christian

2005-01-14

272

Group B Streptococcus suppression of phagocyte functions by protein-mediated engagement of human Siglec-5  

PubMed Central

Group B Streptococcus (GBS) is a leading cause of invasive bacterial infections in human newborns. A key GBS virulence factor is its capsular polysaccharide (CPS), displaying terminal sialic acid (Sia) residues which block deposition and activation of complement on the bacterial surface. We recently demonstrated that GBS Sia can bind human CD33-related Sia-recognizing immunoglobulin (Ig) superfamily lectins (hCD33rSiglecs), a family of inhibitory receptors expressed on the surface of leukocytes. We report the unexpected discovery that certain GBS strains may bind one such receptor, hSiglec-5, in a Sia-independent manner, via the cell wall–anchored ? protein, resulting in recruitment of SHP protein tyrosine phosphatases. Using a panel of WT and mutant GBS strains together with Siglec-expressing cells and soluble Siglec-Fc chimeras, we show that GBS ? protein binding to Siglec-5 functions to impair human leukocyte phagocytosis, oxidative burst, and extracellular trap production, promoting bacterial survival. We conclude that protein-mediated functional engagement of an inhibitory host lectin receptor promotes bacterial innate immune evasion.

Carlin, Aaron F.; Chang, Yung-Chi; Areschoug, Thomas; Lindahl, Gunnar; Hurtado-Ziola, Nancy; King, Charles C.

2009-01-01

273

Direct Simulation of Protein-Mediated Vesicle Fusion: Lung Surfactant Protein B  

PubMed Central

We simulated spontaneous fusion of small unilamellar vesicles mediated by lung surfactant protein B (SP-B) using the MARTINI force field. An SP-B monomer triggers fusion events by anchoring two vesicles and facilitating the formation of a lipid bridge between the proximal leaflets. Once a lipid bridge is formed, fusion proceeds via a previously described stalk – hemifusion diaphragm – pore-opening pathway. In the absence of protein, fusion of vesicles was not observed in either unbiased simulations or upon application of a restraining potential to maintain the vesicles in close proximity. The shape of SP-B appears to enable it to bind to two vesicles at once, forcing their proximity, and to facilitate the initial transfer of lipids to form a high-energy hemifusion intermediate. Our results may provide insight into more general mechanisms of protein-mediated membrane fusion, and a possible role of SP-B in the secretory pathway and transfer of lung surfactant to the gas exchange interface.

Baoukina, Svetlana; Tieleman, D. Peter

2010-01-01

274

Direct simulation of protein-mediated vesicle fusion: lung surfactant protein B.  

PubMed

We simulated spontaneous fusion of small unilamellar vesicles mediated by lung surfactant protein B (SP-B) using the MARTINI force field. An SP-B monomer triggers fusion events by anchoring two vesicles and facilitating the formation of a lipid bridge between the proximal leaflets. Once a lipid bridge is formed, fusion proceeds via a previously described stalk - hemifusion diaphragm - pore-opening pathway. In the absence of protein, fusion of vesicles was not observed in either unbiased simulations or upon application of a restraining potential to maintain the vesicles in close proximity. The shape of SP-B appears to enable it to bind to two vesicles at once, forcing their proximity, and to facilitate the initial transfer of lipids to form a high-energy hemifusion intermediate. Our results may provide insight into more general mechanisms of protein-mediated membrane fusion, and a possible role of SP-B in the secretory pathway and transfer of lung surfactant to the gas exchange interface. PMID:20923647

Baoukina, Svetlana; Tieleman, D Peter

2010-10-01

275

Refractive-Index-Based Screening of Membrane-Protein-Mediated Transfer across Biological Membranes  

PubMed Central

Abstract Numerous membrane-transport proteins are major drug targets, and therefore a key ingredient in pharmaceutical development is the availability of reliable, efficient tools for membrane transport characterization and inhibition. Here, we present the use of evanescent-wave sensing for screening of membrane-protein-mediated transport across lipid bilayer membranes. This method is based on a direct recording of the temporal variations in the refractive index that occur upon a transfer-dependent change in the solute concentration inside liposomes associated to a surface plasmon resonance (SPR) active sensor surface. The applicability of the method is demonstrated by a functional study of the aquaglyceroporin PfAQP from the malaria parasite Plasmodium falciparum. Assays of the temperature dependence of facilitated diffusion of sugar alcohols on a single set of PfAQP-reconstituted liposomes reveal that the activation energies for facilitated diffusion of xylitol and sorbitol are the same as that previously measured for glycerol transport in the aquaglyceroporin of Escherichia coli (5 kcal/mole). These findings indicate that the aquaglyceroporin selectivity filter does not discriminate sugar alcohols based on their length, and that the extra energy cost of dehydration of larger sugar alcohols, upon entering the pore, is compensated for by additional hydrogen-bond interactions within the aquaglyceroporin pore.

Branden, Magnus; Tabaei, Seyed R.; Fischer, Gerhard; Neutze, Richard; Hook, Fredrik

2010-01-01

276

Procontractile G protein-mediated signaling pathways antagonistically regulate smooth muscle differentiation in vascular remodeling.  

PubMed

Vascular smooth muscle (Sm) cells (VSMCs) are highly plastic. Their differentiation state can be regulated by serum response factor (SRF), which activates genes involved in Sm differentiation and proliferation by recruiting cofactors, such as members of the myocardin family and ternary complex factors (TCFs), respectively. However, the extracellular cues and upstream signaling mechanisms regulating SRF-dependent VSMC differentiation under in vivo conditions are poorly understood. In this study, we show that the procontractile signaling pathways mediated by the G proteins G(12)/G(13) and G(q)/G(11) antagonistically regulate VSMC plasticity in different models of vascular remodeling. In mice lacking G?(12)/G?(13) or their effector, the RhoGEF protein LARG, RhoA-dependent SRF-regulation was blocked and down-regulation of VSMC differentiation marker genes was enhanced. This was accompanied by an excessive vascular remodeling and exacerbation of atherosclerosis. In contrast, Sm-specific G?(q)/G?(11) deficiency blocked activation of extracellular signal-regulated kinase 1/2 and the TCF Elk-1, resulting in a reduced VSMC dedifferentiation in response to flow cessation or vascular injury. These data show that the balanced activity of both G protein-mediated pathways in VSMCs is required for an appropriate vessel remodeling response in vascular diseases and suggest new approaches to modulate Sm differentiation in vascular pathologies. PMID:23129751

Althoff, Till F; Albarrán Juárez, Julián; Troidl, Kerstin; Tang, Cong; Wang, Shengpeng; Wirth, Angela; Takefuji, Mikito; Wettschureck, Nina; Offermanns, Stefan

2012-11-05

277

Protein-mediated efficient synergistic "antenna effect" in a ternary system in D?O medium.  

PubMed

A ternary system consisting of a protein, catechin (either + or - epimer), and Tb(III) in suitable aqueous buffer medium at physiological pH (= 6.8) has been shown to exhibit highly efficient "antenna effect". Steady state and time-resolved emission studies of each component in the binary complexes (protein with Tb(III) and (+)- or (-)-catechin with Tb(III)) and the ternary systems along with the molecular docking studies reveal that the efficient sensitization could be ascribed to the effective shielding of microenvironment of Tb(III) from O-H oscillator and increased Tb-C (+/-) interaction in the ternary systems in aqueous medium. The ternary system exhibits protein-mediated efficient antenna effect in D(2)O medium due to synergistic ET from both the lowest ??* triplet state of Trp residue in protein and that of catechin apart from protection of the Tb(III) environment from matrix vibration. The simple system consisting of (+)- or (-)-catechin and Tb(III) in D(2)O buffer at pH 6.8 has been prescribed to be a useful biosensor. PMID:22812923

Ghorai, Shyamal Kr; Samanta, Swarna Kamal; Mukherjee, Manini; Ghosh, Sanjib

2012-08-03

278

Groundwater Basics  

NSDL National Science Digital Library

The basic information and terms covered on this site are associated with groundwater, including aquifers (confined and unconfined), saturation zones, the water table, impermeable layers, the water cycle (hydrologic cycle), discharge, and recharge. There is a list of groundwater facts and diagrams of two types of aquifers along with a typical groundwater system. Information on contamination includes how groundwater is contaminated, what the effects are, how it can be prevented, and how it can be restored. There is also a list of things one can do about contamination.

279

Basically Acids  

NSDL National Science Digital Library

Students learn the basics of acid/base chemistry in a fun, interactive way by studying instances of acid/base chemistry found in popular films such as Harry Potter and the Prisoner of Azkaban and National Treasure. Students learn what acids, bases and indicators are and how they can be used, including invisible ink. They also learn how engineers use acids and bases every day to better our quality of life. Students' interest is piqued by the use of popular culture in the classroom.

University Of Houston

280

GPS Basics  

NSDL National Science Digital Library

The Federal Aviation Administration maintains the graphically impressive Global Positioning System (GPS) Basics Web site. From the history of the global positioning system and how it works to governmental policy that controls its use, this site does a good job of explaining all facets of what GPS is about without being overly technical. Interested visitors can explore some of the other links that cover satellite navigation topics as well, such as GPS programs; a library of documents, fact sheets, press releases, and news; frequently asked questions; links; and more. Anyone interested in mapping, navigation, or similar subjects will enjoy exploring the interesting information provided on this well designed site.

281

Three different actions of phenylglyoxal on band 3 protein-mediated anion transport across the red blood cell membrane  

Microsoft Academic Search

Phenylglyoxalation of the red blood cell membrane leads to three superimposed effects on band 3 protein-mediated anion equilibrium exchange as measured by means of radiosulfate: (1) a shift of the curve relating transport activity to pH towards lower pH values, possibly in combination with an increase of the maximal transport activity. This is accompanied by effect (2), the abolishment of

E. M Gärtner; K Liebold; B Legrum; H Fasold; H Passow

1997-01-01

282

Probability of the site juxtaposition determines the rate of protein-mediated DNA looping.  

PubMed

Numerous biological processes are regulated by DNA elements that communicate with their targets over a distance via formation of protein-bridged DNA loops. One of the first questions arising in studies of DNA looping is whether the rate of loop formation is limited by diffusion of the DNA sites. We addressed this question by comparing the in vitro measured rates of transcription initiation in the NtrC-glnAp2 enhancer-dependent transcription initiation system with predictions of two different theoretical models. The promoter and enhancer were in a 7.6-kb plasmid and separated by 2.5 kb. The measurements were performed for different values of the plasmid superhelix density, from 0 to -0.07. Earlier theoretical analysis, based on the Monte Carlo simulation of DNA conformations, showed that if the rate of loop formation is determined by the equilibrium probability of juxtaposition of the DNA sites, the rate should be approximately 100 times higher in supercoiled than in relaxed DNA. On the other hand, Brownian dynamics simulation showed that if the rate of loop formation is limited by the site diffusion, it should be nearly independent of DNA supercoiling. We found that efficiency of the transcription initiation increases by nearly two orders of magnitude as a result of the corresponding increase of the template supercoiling. This clearly shows that the rate of bridging in the enhancer-promoter system is not limited by diffusion of the DNA sites to one another. We argue that this conclusion derived for the specific system is likely to be valid for the great majority of biological processes involving protein-mediated DNA looping. PMID:17573434

Polikanov, Yury S; Bondarenko, Vladimir A; Tchernaenko, Vladimir; Jiang, Yong I; Lutter, Leonard C; Vologodskii, Alexander; Studitsky, Vasily M

2007-06-15

283

TAL1/SCL relieves the E2-2-mediated repression of VEGFR2 promoter activity.  

PubMed

The basic helix-loop-helix (bHLH) protein TAL1/SCL is essential for embryonic-vascular development. TAL1/SCL regulates the activation of endothelial cells by binding directly or indirectly to DNA sequences in critical target genes. We recently demonstrated that E-box protein E2-2 blocks endothelial cell activation via perturbation of VEGFR2 promoter activity. Herein, we report that TAL1/SCL interacts with E2-2 and inhibits E2-2-mediated effects on reporter activity. Mutational analysis revealed that the HLH domain of TAL1/SCL, but not its basic region, is required for interaction with E2-2. Importantly, TAL1/SCL relieves the E2-2-mediated repression of VEGFR2 reporter activity in endothelial cells. Our data elaborate on the bHLH protein interactions that regulate endothelial cell activation. PMID:19029143

Tanaka, Aya; Itoh, Fumiko; Itoh, Susumu; Kato, Mitsuyasu

2008-11-23

284

Hey1, a Mediator of Notch Signaling, Is an Androgen Receptor Corepressor  

PubMed Central

Hey1 is a member of the basic helix-loop-helix-Orange family of transcriptional repressors that mediate Notch signaling. Here we show that transcription from androgen-dependent target genes is inhibited by Hey1 and that expression of a constitutively active form of Notch is capable of repressing transactivation by the endogenous androgen receptor (AR). Our results indicate that Hey1 functions as a corepressor for AF1 in the AR, providing a mechanism for cross talk between Notch and androgen-signaling pathways. Hey1 colocalizes with AR in the epithelia of patients with benign prostatic hyperplasia, where it is found in both the cytoplasm and the nucleus. In marked contrast, we demonstrate that Hey1 is excluded from the nucleus in most human prostate cancers, raising the possibility that an abnormal Hey1 subcellular distribution may have a role in the aberrant hormonal responses observed in prostate cancer.

Belandia, Borja; Powell, Sue M.; Garcia-Pedrero, Juana M.; Walker, Marjorie M.; Bevan, Charlotte L.; Parker, Malcolm G.

2005-01-01

285

NOTCH Signaling and ATOH1 in Colorectal Cancers  

PubMed Central

The Notch receptor signaling pathway regulates expression of the basic helix-loop-helix transcription factor ATOH1 (Math1/Hath1) to determine cell fate in the intestine. In differentiating intestinal stem cells, high levels of Notch activity specify absorptive enterocyte/colonocyte differentiation, whereas high ATOH1 activity specifies secretory (goblet, enteroendocrine, and Paneth) cell differentiation. In colorectal cancer, ATOH1 is a tumor suppressor that is silenced in most tumors, while Notch is oncogenic and often highly active in human tumors. In other gastrointestinal malignancies with features of intestinal metaplasia, such as esophageal and gastric cancers, the Notch-ATOH1 pathway becomes activated. In cancers and preneoplastic tissues that retain the ability to activate ATOH1, therapeutic targeting of this pathway can be achieved by inhibiting Notch activity (with Notch-targeting antibodies or small-molecule inhibitors of ?-secretase). Thus, targeting the Notch-ATOH1 pathway represents a novel approach to differentiation therapy in gastrointestinal cancers.

2011-01-01

286

Regulation of Rxfp2 (Lgr8) expression in the mouse fetal kidney by the transcription factor Pod1 (Tcf 21).  

PubMed

Rxfp2 is present in putative mesangial cells at embryonic stage 18 (E18) in the rat kidney, suggesting that insulin-like peptide 3 is involved in glomerulogenesis. One of the main regulatory factors in glomerulogenesis is the basic helix-loop-helix transcription factor Pod1. Therefore, we examined the expression of Rxfp2 relative to Pod1 in the fetal and neonatal mouse kidney and tested the hypothesis that Rxfp2 is a downstream target of Pod1. Rxfp2 gene expression in the neonatal kidney was highest at E14 and E16 but decreased significantly at E18. This was not correlated with increased Pod1 expression. However, there was a significant increase in Rxfp2 expression in the kidneys of Pod1(-/-) mice at E18. These data suggest that Pod1 may negatively regulate Rxfp2 expression in the developing glomerulus to promote cell proliferation. PMID:19416211

Familari, Mary; Vu, Duc; Parry, Laura J

2009-04-01

287

Id: A Target of BMP Signaling  

NSDL National Science Digital Library

Cytokines of the transforming growth factor-β (TGF-β) superfamily transduce their signals by activating receptor-regulated Smads (R-Smads). Distinct R-Smads or combinations of R-Smads are activated by TGF-β, activin, or bone morphogenetic proteins (BMPs). R-Smads activated by BMPs induce expression of Id proteins, which act as inhibitors of differentiation and stimulators of cell growth by inhibiting the function of basic helix-loop-helix transcription factors. In endothelial cells, TGF-β binds to two distinct type I receptor serine-threonine kinases, ALK-5 and ALK-1; the latter activates the same R-Smads that are activated by BMP and induces synthesis of Id (inhibitor of differentation or inhibitor of DNA binding) proteins. Growing evidence suggests that Id proteins may play crucial roles in angiogenesis, neurogenesis, and osteogenesis and act as key molecules in regulating biological responses induced by BMPs and TGF-β.

Kohei Miyazono (University of Tokyo;Department of Molecular Pathology, Graduate School of Medicine REV); Keiji Miyazawa (University of Tokyo;Department of Molecular Pathology, Graduate School of Medicine REV)

2002-09-24

288

Dynamic expression and essential functions of Hes7 in somite segmentation  

PubMed Central

The basic helix–loop–helix (bHLH) gene Hes7, a putative Notch effector, encodes a transcriptional repressor. Here, we found that Hes7 expression oscillates in 2-h cycles in the presomitic mesoderm (PSM). In Hes7-null mice, somites are not properly segmented and their anterior–posterior polarity is disrupted. As a result, the somite derivatives such as vertebrae and ribs are severely disorganized. Although expression of Notch and its ligands is not affected significantly, the oscillator and Notch modulator lunatic fringe is expressed continuously throughout the mutant PSM. These results indicate that Hes7 controls the cyclic expression of lunatic fringe and is essential for coordinated somite segmentation.

Bessho, Yasumasa; Sakata, Ryoichi; Komatsu, Suguru; Shiota, Kohei; Yamada, Shuichi; Kageyama, Ryoichiro

2001-01-01

289

Stra13 regulates satellite cell activation by antagonizing Notch signaling  

PubMed Central

Satellite cells play a critical role in skeletal muscle regeneration in response to injury. Notch signaling is vital for satellite cell activation and myogenic precursor cell expansion but inhibits myogenic differentiation. Thus, precise spatial and temporal regulation of Notch activity is necessary for efficient muscle regeneration. We report that the basic helix-loop-helix transcription factor Stra13 modulates Notch signaling in regenerating muscle. Upon injury, Stra13?/? mice exhibit increased cellular proliferation, elevated Notch signaling, a striking regeneration defect characterized by degenerated myotubes, increased mononuclear cells, and fibrosis. Stra13?/? primary myoblasts also exhibit enhanced Notch activity, increased proliferation, and defective differentiation. Inhibition of Notch signaling ex vivo and in vivo ameliorates the phenotype of Stra13?/? mutants. We demonstrate in vitro that Stra13 antagonizes Notch activity and reverses the Notch-imposed inhibition of myogenesis. Thus, Stra13 plays an important role in postnatal myogenesis by attenuating Notch signaling to reduce myoblast proliferation and promote myogenic differentiation.

Sun, Hong; Li, Li; Vercherat, Cecile; Gulbagci, Neriman Tuba; Acharjee, Sujata; Li, Jiali; Chung, Teng-Kai; Thin, Tin Htwe; Taneja, Reshma

2007-01-01

290

Stress-responsive gene ICE1 from Vitis amurensis increases cold tolerance in tobacco.  

PubMed

We report the identification of the inducer of CBF expression 1 (ICE1) from Vitis amurensis, an upstream transcription factor that regulates the transcription of CBF-like genes. The structure of the basic helix-loop-helix domain of VaICE1 is closely related to that of ICE1 in woody plants. This gene is strongly induced in leaves, roots, stems, and petioles by cold temperature. With longer duration of exposure to cold treatments, the expression patterns of organs exhibit differences, which are not observed in normal condition. Transgenic tobacco over-expressing VaICE1 has higher chilling tolerance and survival ability by improving the activities of superoxide dismutase, peroxidase, and catalase, as well as the chlorophyll yield. PMID:23968929

Dong, Chang; Zhang, Zhen; Ren, Junpeng; Qin, Yang; Huang, Jinfeng; Wang, Yan; Cai, Binhua; Wang, Bailin; Tao, Jianmin

2013-08-06

291

PIFs: pivotal components in a cellular signaling hub  

PubMed Central

A small subset of basic helix–loop–helix transcription factors called PIFs [phytochrome (phy)-interacting factors] act to repress seed germination, promote seedling skotomorphogenesis and promote shade-avoidance through regulated expression of over a thousand genes. Light-activated phy molecules directly reverse these activities by inducing rapid degradation of the PIF proteins. Here, we review recent advances in dissecting this signaling pathway and examine emerging evidence that indicates that other pathways also converge to regulate PIF activity, including the gibberellin pathway, the circadian clock and high temperature. The PIFs thus have broader roles than previously appreciated, functioning as a cellular signaling hub that integrates multiple signals to orchestrate regulation of the transcriptional network that drives multiple facets of downstream morphogenesis. The relative contributions of the individual PIFs to this spectrum of regulatory functions ranges from quantitatively redundant to qualitatively distinct.

Leivar, Pablo; Quail, Peter H.

2010-01-01

292

The conserved WRPW motif of Hes6 mediates proteasomal degradation  

SciTech Connect

Hes6 belongs to a subfamily of basic helix-loop-helix transcription factors that includes Drosophila Hairy and Enhancer of split genes. Like other members of the family, Hes6 features the WRPW motif which is consisted just of four amino acids at its C-terminus. Here, we show that WRPW motif deletion mutant protein is substantially stabilized in comparison to the full length protein and that the enhanced stability is due to its resistance to proteasomal degradation. The WRPW motif also appears to be sufficient for acceleration of proteolysis as its fusion to two heterologous proteins, the green fluorescent protein (GFP) of Aequoria victoria and Gal4 DNA binding domain of Saccharomyces cerevisiae, significantly destabilized the proteins. These findings demonstrate a novel function of this conserved motif as a degradation signal and raise the possibility of utilizing it for controlling the level of ectopically expressed gene products.

Kang, Seon Ah [Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, 11-1 Daehyun-dong, Seodaemun-gu, Seoul 120-750 (Korea, Republic of); Seol, Jae Hong [Seoul National University School of Biological Sciences, San 56-1, Shillim-dong, Kwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Jaesang [Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, 11-1 Daehyun-dong, Seodaemun-gu, Seoul 120-750 (Korea, Republic of)]. E-mail: jkim1964@ewha.ac.kr

2005-06-24

293

A leech homolog of twist: evidence for its inheritance as a maternal mRNA.  

PubMed

In the development of leeches such as Helobdella robusta, mesodermal and ectodermal fates segregate to cells DM and DNOPQ, respectively, at fourth cleavage. As one step in identifying genes that may act in mesoderm determination, we have cloned the H. robusta homolog to the Drosophila gene twist. This homolog, designated Hro-twi, exhibits high (> 90%) amino acid identity with other twist-class genes within its basic-helix loop-helix (b-HLH) DNA binding motif and dimerization domain. Like twist, Hro-twi contains CAX-rich stretches: three stretches 5' to the b-HLH and one located 3' of the b-HLH motif. RT-PCR analysis suggests that Hro-twi is present throughout development, beginning as a maternal transcript in the oocyte. PMID:9358036

Soto, J G; Nelson, B H; Weisblat, D A

1997-10-15

294

Nuclear localized protein-1 (Nulp1) increases cell death of human osteosarcoma cells and binds the X-linked inhibitor of apoptosis protein  

SciTech Connect

Nuclear localized protein-1 (Nulp1) is a recently identified gene expressed in mouse and human tissues particularly during embryonic development. Nulp1 belongs to the family of basic helix-loop-helix (bHLH) proteins that are important in development. The precise function of Nulp1 in cells is however not known. We observed that overexpression of Nulp1 induces a large increase in cell death of human osteosarcoma Saos2 cells with DNA fragmentation. In mouse N2A neuroblastoma cells Nulp1 affected cell proliferation and sensitized cells towards death induced by staurosporine. Staining using a novel antibody localized Nulp1 mainly to the cell nucleus and to some extent to the cytoplasm. Nulp1 binds the X-linked inhibitor of apoptosis protein (XIAP) and this interaction was increased during cell death. These results indicate that Nulp1 plays a role in cell death control and may influence tumor growth.

Steen, Hakan [Department of Neuroscience, Uppsala University, Biomedical Centre, Box 587, Husargatan 3, SE-75123 Uppsala (Sweden); Lindholm, Dan [Department of Neuroscience, Uppsala University, Biomedical Centre, Box 587, Husargatan 3, SE-75123 Uppsala (Sweden); Minerva Institute for Medical Research, Biomedicum Helsinki, Helsinki (Finland)], E-mail: dan.lindholm@neuro.uu.se

2008-02-08

295

Three redundant brassinosteroid early response genes encode putative bHLH transcription factors required for normal growth.  

PubMed Central

Brassinosteroids (BRs) are a class of polyhydroxylated steroids that are important regulators of plant growth and development. We have identified three closely related basic helix-loop-helix (bHLH) transcription factors, BEE1, BEE2, and BEE3, as products of early response genes required for full BR response. Comparison of the phenotypes of plants that overexpress BEE1 with bee1 bee2 bee3 triple-knockout mutant plants suggests that BEE1, BEE2, and BEE3 are functionally redundant positive regulators of BR signaling. Expression of BEE1, BEE2, and BEE3 is also regulated by other hormones, notably abscisic acid (ABA), a known antagonist of BR signaling. Reduced ABA response in plants overexpressing BEE1 suggests that BEE proteins may function as signaling intermediates in multiple pathways.

Friedrichsen, Danielle M; Nemhauser, Jennifer; Muramitsu, Takamichi; Maloof, Julin N; Alonso, Jose; Ecker, Joseph R; Furuya, Masaki; Chory, Joanne

2002-01-01

296

The nuclear hormone receptor coactivator SRC-1 is a specific target of p300.  

PubMed Central

p300 and its family member, CREB-binding protein (CBP), function as key transcriptional coactivators by virtue of their interaction with the activated forms of certain transcription factors. In a search for additional cellular targets of p300/CBP, a protein-protein cloning strategy, surprisingly identified SRC-1, a coactivator involved in nuclear hormone receptor transcriptional activity, as a p300/CBP interactive protein. p300 and SRC-1 interact, specifically, in vitro and they also form complexes in vivo. Moreover, we show that SRC-1 encodes a new member of the basic helix-loop-helix-PAS domain family and that it physically interacts with the retinoic acid receptor in response to hormone binding. Together, these results implicate p300 as a component of the retinoic acid signaling pathway, operating, in part, through specific interaction with a nuclear hormone receptor coactivator, SRC-1. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4

Yao, T P; Ku, G; Zhou, N; Scully, R; Livingston, D M

1996-01-01

297

Establishing the transcriptional programme for blood: the SCL stem cell enhancer is regulated by a multiprotein complex containing Ets and GATA factors  

PubMed Central

Stem cells are a central feature of metazoan biology. Haematopoietic stem cells (HSCs) represent the best-characterized example of this phenomenon, but the molecular mechanisms responsible for their formation remain obscure. The stem cell leukaemia (SCL) gene encodes a basic helix–loop–helix (bHLH) transcription factor with an essential role in specifying HSCs. Here we have addressed the transcriptional hierarchy responsible for HSC formation by characterizing an SCL 3? enhancer that targets expression to HSCs and endothelium and their bipotential precursors, the haemangioblast. We have identified three critical motifs, which are essential for enhancer function and bind GATA-2, Fli-1 and Elf-1 in vivo. Our results suggest that these transcription factors are key components of an enhanceosome responsible for activating SCL transcription and establishing the transcriptional programme required for HSC formation.

Gottgens, Berthold; Nastos, Aristotelis; Kinston, Sarah; Piltz, Sandie; Delabesse, Eric C.M.; Stanley, Maureen; Sanchez, Maria-Jose; Ciau-Uitz, Aldo; Patient, Roger; Green, Anthony R.

2002-01-01

298

Programmed cell death and context dependent activation of the EGF pathway regulate gliogenesis in the Drosophila olfactory system.  

PubMed

In the Drosophila antenna, sensory lineages selected by the basic helix-loop-helix transcription factor Atonal are gliogenic while those specified by the related protein Amos are not. What are the mechanisms that cause the two lineages to act differentially? We found that ectopic expression of the Baculovirus inhibitor of apoptosis protein (p35) rescues glial cells from the Amos-derived lineages, suggesting that precursors are removed by programmed cell death. In the wildtype, glial precursors express the extracellular-signal regulated kinase transiently, and antagonism of Epidermal Growth Factor (EGF) pathway signaling compromises their development. We suggest that all sensory lineages on the antenna are competent to produce glia but only those specified by Atonal respond to EGF signaling and survive. These results underscore the importance of developmental context of cell lineages in their responses to non-autonomous signaling in the choice between survival and death. PMID:14706701

Sen, Anindya; Kuruvilla, Daniel; Pinto, Ludwin; Sarin, Apurva; Rodrigues, Veronica

2004-01-01

299

Binding of carbon nanotube to BMP receptor 2 enhances cell differentiation and inhibits apoptosis via regulating bHLH transcription factors  

PubMed Central

Biomaterials that can drive stem cells to an appropriate differentiation level and decrease apoptosis of transplanted cells are needed in regenerative medicine. Nanomaterials are promising novel materials for such applications. Here we reported that carboxylated multiwalled carbon nanotube (MWCNT 1) promotes myogenic differentiation of mouse myoblast cells and inhibits cell apoptosis under the differentiation conditions by regulating basic helix-loop-helix transcription factors. MWCNT 1 attenuates bone morphogenetic protein receptor (BMPR) signaling activity by binding to BMPR2 and attenuating the phosphorylation of BMPR1. This molecular understanding allowed us to tune stem cell differentiation to various levels by chemical modifications, demonstrating human control of biological activities of nanoparticles and opening an avenue for potential applications of nanomaterials in regenerative medicine.

Zhang, Y; Mu, Q; Zhou, H; Vrijens, K; Roussel, M F; Jiang, G; Yan, B

2012-01-01

300

Mutated ?-catenin evades a microRNA-dependent regulatory loop  

PubMed Central

hsa-mir-483 is located within intron 2 of the IGF2 gene. We have previously shown oncogenic features of miR-483-3p through cooperation with IGF2 or by independently targeting the proapoptotic gene BBC3/PUMA. Here we demonstrate that expression of miR-483 can be induced independently of IGF2 by the oncoprotein ?-catenin through an interaction with the basic helix–loop–helix protein upstream stimulatory transcription factor 1. We also show that ?-catenin itself is a target of miR-483-3p, triggering a negative regulatory loop that becomes ineffective in cells harboring an activating mutation of ?-catenin. These results provide insights into the complex regulation of the IGF2/miR-483 locus, revealing players in the ?-catenin pathway.

Veronese, Angelo; Visone, Rosa; Consiglio, Jessica; Acunzo, Mario; Lupini, Laura; Kim, Taewan; Ferracin, Manuela; Lovat, Francesca; Miotto, Elena; Balatti, Veronica; D'Abundo, Lucilla; Gramantieri, Laura; Bolondi, Luigi; Pekarsky, Yuri; Perrotti, Danilo; Negrini, Massimo; Croce, Carlo M.

2011-01-01

301

THE UPS AND DOWNS OF MYC BIOLOGY  

PubMed Central

Summary The basic helix-loop-helix protein Myc is a renowned transcription factor controlling disparate aspects of cell physiology that, together, allow efficient proliferation of somatic cells. This ability, together with the observation that its deregulated expression occurs in the majority of human cancers, suggests that Myc could be a good therapeutic target. However, several aspects of Myc biology remain elusive: what is the major difference between oncogenic and physiological Myc? How does oncogenic Myc evade the intrinsic tumor surveillance pathways provided by evolution? If Myc inhibition were even possible, what would be the consequences for the homeostasis of normal proliferating tissues versus the fate of cancer cells? Here we summarize the latest works addressing these issues.

Soucek, Laura; Evan, Gerard I.

2009-01-01

302

Identification and characterization of a twist ortholog in the polychaete annelid Platynereis dumerilii reveals mesodermal expression of Pdu-twist.  

PubMed

The basic helix-loop-helix transcription factor twist plays a key role during mesoderm development in Bilateria. In this study, we identified a twist ortholog in the polychaete annelid Platynereis dumerilii and analyze its expression during larval development, postlarval growth up to the adult stage, and caudal regeneration after amputation of posterior segments. At late larval stages, Pdu-twist is expressed in the mesodermal anlagen and in developing muscles. During adulthood and caudal regeneration, Pdu-twist is expressed in the posterior growth zone, in mesodermal cells within the newly forming segments and budding parapodia. Our results indicate that Pdu-twist is involved in mesoderm formation during larval development, posterior growth, and caudal regeneration. PMID:23817621

Pfeifer, Kathrin; Schaub, Christoph; Wolfstetter, Georg; Dorresteijn, Adriaan

2013-07-02

303

Network Theory Inspired Analysis of Time-Resolved Expression Data Reveals Key Players Guiding P. patens Stem Cell Development  

PubMed Central

Transcription factors (TFs) often trigger developmental decisions, yet, their transcripts are often only moderately regulated and thus not easily detected by conventional statistics on expression data. Here we present a method that allows to determine such genes based on trajectory analysis of time-resolved transcriptome data. As a proof of principle, we have analysed apical stem cells of filamentous moss (P. patens) protonemata that develop from leaflets upon their detachment from the plant. By our novel correlation analysis of the post detachment transcriptome kinetics we predict five out of 1,058 TFs to be involved in the signaling leading to the establishment of pluripotency. Among the predicted regulators is the basic helix loop helix TF PpRSL1, which we show to be involved in the establishment of apical stem cells in P. patens. Our methodology is expected to aid analysis of key players of developmental decisions in complex plant and animal systems.

Busch, Hauke; Boerries, Melanie; Rensing, Stefan A.

2013-01-01

304

Role of inhibitor of DNA binding-1 protein is related to angiogenesis in the tumor advancement of uterine endometrial cancers  

PubMed Central

The inhibitor of DNA binding (ID)-1 protein, an inhibitor of basic helix-loop-helix transcription factors, has been found to be involved in multiple cellular functions. In the present study, ID-1 histoscores and mRNA levels were both significantly (p<0.05) increased in uterine endometrial cancers according to clinical stage, histological grade and depth of myometrial invasion. Furthermore, the 60-month survival rate of the 25 patients with high ID-1 was poor (52%), while that of the other 25 patients with low ID-1 was significantly higher (80%) (p<0.05). ID-1 histoscores and mRNA levels significantly (p<0.0001) correlated with microvessel counts in uterine endometrial cancers. Therefore, ID-1 acts on tumor advancement via angiogenic activity and can be considered a candidate prognostic indicator in uterine endometrial cancers.

MAW, MIN KHINE; FUJIMOTO, JIRO; TAMAYA, TERUHIKO

2010-01-01

305

Feedback regulation of NEUROG2 activity by MTGR1 is required for progression of neurogenesis  

PubMed Central

The sequential steps of neurogenesis are characterized by highly choreographed changes in transcription factor activity. In contrast to the well-studied mechanisms of transcription factor activation during neurogenesis, much less is understood regarding how such activity is terminated. We previously showed that MTGR1, a member of the MTG family of transcriptional repressors, is strongly induced by a proneural basic helix-loop-helix transcription factor, NEUROG2 in developing nervous system. In this study, we describe a novel feedback regulation of NEUROG2 activity by MTGR1. We show that MTGR1 physically interacts with NEUROG2 and represses transcriptional activity of NEUROG2. MTGR1 also prevents DNA binding of the NEUROG2/E47 complex. In addition, we provide evidence that proper termination of NEUROG2 activity by MTGR1 is necessary for normal progression of neurogenesis in the developing spinal cord. These results highlight the importance of feedback regulation of proneural gene activity in neurodevelopment.

Aaker, Joshua D.; Patineau, Andrea L.; Yang, Hyun-jin; Ewart, David T.; Gong, Wuming; Li, Tongbin; Nakagawa, Yasushi; McLoon, Steven C.; Koyano-Nakagawa, Naoko

2009-01-01

306

The role of BETA2/NeuroD1 in the development of the nervous system.  

PubMed

BETA2/NeuroD1 is a member of the basic helix-loop-helix (bHLH) transcription factor family, which has been shown to play a major role in development of the nervous system and formation of the endocrine system. Gain-of-function studies have indicated that BETA2/NeuroD1 is important for the neurogenesis of Xenopus embryos and several neurogenic cell lines. Disruption of the gene encoding BETA2/NeuroD1 leads to severe abnormalities of the developing mouse central nervous system as well as the peripheral nervous system. The focus of this article is on the recent progress in understanding the role of BETA2/NeuroD1 in the development of the nervous system. PMID:15247487

Cho, Jang-Hyeon; Tsai, Ming-Jer

2004-08-01

307

HEB and E2A function as SMAD/FOXH1 cofactors  

PubMed Central

Nodal signaling, mediated through SMAD transcription factors, is necessary for pluripotency maintenance and endoderm commitment. We identified a new motif, termed SMAD complex-associated (SCA), that is bound by SMAD2/3/4 and FOXH1 in human embryonic stem cells (hESCs) and derived endoderm. We demonstrate that two basic helix–loop–helix (bHLH) proteins—HEB and E2A—bind the SCA motif at regions overlapping SMAD2/3 and FOXH1. Furthermore, we show that HEB and E2A associate with SMAD2/3 and FOXH1, suggesting they form a complex at critical target regions. This association is biologically important, as E2A is critical for mesendoderm specification, gastrulation, and Nodal signal transduction in Xenopus tropicalis embryos. Taken together, E proteins are novel Nodal signaling cofactors that associate with SMAD2/3 and FOXH1 and are necessary for mesendoderm differentiation.

Yoon, Se-Jin; Wills, Andrea E.; Chuong, Edward; Gupta, Rakhi; Baker, Julie C.

2011-01-01

308

Regulation of Plasmodesmatal Permeability and Stomatal Patterning by the Glycosyltransferase-Like Protein KOBITO11[W][OA  

PubMed Central

The differentiation of stomata provides a convenient model for studying pattern formation in plant tissues. Stomata formation is induced by a set of basic helix-loop-helix transcription factors and inhibited by a signal transduction pathway initiated by TOO MANY MOUTHS (TMM) and ERECTA family (ERf) receptors. The formation of a proper stomata pattern is also dependent upon the restriction of symplastic movement of basic helix-loop-helix transcription factors into neighboring cells, especially in the backgrounds where the function of the TMM/ERf signaling pathway is compromised. Here, we describe a novel mutant of KOBITO1 in Arabidopsis (Arabidopsis thaliana). The kob1-3 mutation leads to the formation of stomata clusters in the erl1 erl2 background but not in the wild type. Cell-to-cell mobility assays demonstrated an increase in intercellular protein trafficking in kob1-3, including increased diffusion of SPEECHLESS, suggesting that the formation of stomata clusters is due to an escape of cell fate-specifying factors from stomatal lineage cells. While plasmodesmatal permeability is increased in kob1-3, we did not detect drastic changes in callose accumulation at the neck regions of the plasmodesmata. Previously, KOBITO1 has been proposed to function in cellulose biosynthesis. Our data demonstrate that disruption of cellulose biosynthesis in the erl1 erl2 background does not lead to the formation of stomata clusters, indicating that cellulose biosynthesis is not a major determining factor for regulating plasmodesmatal permeability. Analysis of KOBITO1 structure suggests that it is a glycosyltransferase-like protein. KOBITO1 might be involved in a carbohydrate metabolic pathway that is essential for both cellulose biosynthesis and the regulation of plasmodesmatal permeability.

Kong, Danyu; Karve, Rucha; Willet, Alaina; Chen, Ming-Kun; Oden, Jennifer; Shpak, Elena D.

2012-01-01

309

P/CAF rescues the Bhlhe40-mediated repression of MyoD transactivation.  

PubMed

Previously, we found that MRFs (myogenic regulatory factors) regulated the expression of PGC-1alpha (peroxisome-proliferator-activated receptor gamma co-activator 1alpha) by targeting a short region, from nt -49 to +2 adjacent to the transcription initiation site, that contained two E-boxes. However, only the E2-box had significant affinity for MRFs, and the E1-box was predicted to be the target of Bhlhe40 (basic helix-loop-helix family, member e40, also known as Stra13, Bhlhb2, DEC1 and Sharp2), a transcriptional repressor implicated in the regulation of several physiological processes. In the present study, by using EMSA (electrophoresis mobility-shift assay), we confirmed that Bhlhe40 targeted the E1-box and formed a complex with the basic helix-loop-helix transcription factor MyoD (myogenic differentiation factor D) on the PGC-1alpha core promoter. We demonstrate that Bhlhe40 binds to the promoters of PGC-1alpha and myogenic genes in vivo and that Bhlhe40 represses the MyoD-mediated transactivation of these promoters. Furthermore, we found that this repression could be relieved by P/CAF (p300/CBP-associated factor) in a dose-dependent manner, but not by CBP [CREB (cAMP-response-element-binding protein)-binding protein]. Bhlhe40 interacted with P/CAF and this interaction disrupted the interaction between P/CAF and MyoD. These results suggest that Bhlhe40 functions as a repressor of MyoD by binding to adjacent E-boxes and sequestering P/CAF from MyoD. PMID:19522704

Hsiao, Sheng P; Huang, Kai M; Chang, Hsin Y; Chen, Shen L

2009-08-13

310

Characterization of msim, a murine homologue of the Drosophila sim transcription factor  

SciTech Connect

Mutations in the Drosophila single-minded (sim) gene result in loss of precursor cells that give rise to midline cells of the embryonic central nervous system. During the course of an exon-trapping strategy aimed at identifying transcripts that contribute to the etiology and pathophysiology of Down syndrome, we identified a human exon from the Down syndrome, we identified a human exon from the Down syndrome critical region showing significantly homology to the Drosophila sim gene. Using a cross-hybridization approach, we have isolated a murine homolog of Drosophila sim gene, which we designated msim. Nucleotide and predicted amino acid sequence analyses of msim cDNA clones indicate the this gene encodes a member of the basic-helix-loop-helix class of transcription factors. The murine and Drosophila proteins share 88% residues within the basic-helix-loop helix domain, with an overall homology of 92%. In addition, the N-terminal domain of MSIM contains two PAS dimerization motifs also featured in the Drosophila sim gene product, as well as a small number of other transcription factors. Northern blot analysis of adult murine tissues revealed that the msim gene produces a single mRNA species of {approximately}4 kb expressed in a small number of tissues, with the highest levels in the kidneys and lower levels present in skeletal muscle, lung, testis, brain, and heart. In situ hybridization experiments demonstrate that msim is also expressed in early fetal development in the central nervous system and in cartilage primordia. The characteristics of the msim gene are consistent with its putative function as a transcriptional regulator. 51 refs., 6 figs., 1 tab.

Moffett, P.; Reece, M.; Pelletier, J. [McGill Univ., Quebec (Canada)] [and others

1996-07-01

311

Potential Roles of Arnt2 in Zebrafish Larval Development  

PubMed Central

Abstract The aryl hydrocarbon receptor nuclear translocator (ARNT) is a basic helix-loop-helix–PAS heterodimeric transcription factor that dimerizes with other basic helix-loop-helix–PAS proteins to mediate biological responses. The function of ARNT2 is poorly understood. Here we provide an initial characterization of the zebrafish arnt2 null (arnt2?/?) mutant to identify functions of Arnt2 during development. Arnt2?/? mutant zebrafish develop normally until 120 hours postfertilization (hpf) when morphological changes and functional deficits occur. The C-start escape response initiated by either touch or startle stimuli is absent in the mutants. Brain ventricle size is markedly increased at 120 hpf. Heart ventricles are enlarged, with decreased ventricle wall thickness. A cardiac arrhythmia, characterized by missing beats, is also observed in the mutants. This is associated with bradycardia in arnt2?/? larvae. Dilated liver sinusoids merge abnormally to form an extensive, labyrinth-like network of vascular channels. External appearance of arnt2?/? larvae at 120 hpf is indistinguishable from wild type except that the swim bladder is not inflated. The arnt2?/? mutants are not debilitated when phenotypic effects are first detected at 120 hpf that culminate in mortality, 4 days later around 216 hpf. Gross morphological assessment of the development of forebrain, midbrain, and hindbrain regions, neuromasts and Mauthner neurons, inner ear semicircular canals and otoliths, primary motor neurons, trigeminal ganglia, and trunk skeletal muscles, before or when the arnt2?/? phenotype was observed, failed to demonstrate a difference from wild type. The only effect in arnt2?/? larvae that occurred before 120 hpf was a decrease in expression of sim1, an Arnt2 dimerization partner, in the hypothalamus and ventral thalamus at 72 hpf. Further research is needed to determine if the primary functions of Arnt2 occur during the larval stage, when the phenotype is observed, or earlier in development.

Hill, Adrian J.; Heiden, Tisha C. King; Heideman, Warren

2009-01-01

312

Myogenin and MEF2 function synergistically to activate the MRF4 promoter during myogenesis.  

PubMed Central

The basic helix-loop-helix muscle regulatory factor (MRF) gene family encodes four distinct muscle-specific transcription factors known as MyoD, myogenin, Myf-5, and MRF4. These proteins represent key regulatory factors that control many aspects of skeletal myogenesis. Although the MRFs often exhibit overlapping functional activities, their distinct expression patterns during embryogenesis suggest that each protein plays a unique role in controlling aspects of muscle development. As a first step in determining how MRF4 gene expression is developmentally regulated, we examined the ability of the MRF4 gene to be expressed in a muscle-specific fashion in vitro. Our studies show that the proximal MRF4 promoter contains sufficient information to direct muscle-specific expression. Located within the proximal promoter are a single MEF2 site and E box that are required for maximum MRF4 expression. Mutation of the MEF2 site or E box severely impairs the ability of this promoter to produce a muscle-specific response. In addition, the MEF2 site and E box function in concert to synergistically activate the MRF4 gene in nonmuscle cells coexpressing MEF2 and myogenin proteins. Thus, the MRF4 promoter is regulated by the MEF2 and basic helix-loop-helix MRF protein family through a cross-regulatory circuitry. Surprisingly, the MRF4 promoter itself is not transactivated by MRF4, suggesting that this MRF gene is not subject to an autoregulatory pathway as previously implied by other studies. Understanding the molecular mechanisms regulating expression of each MRF gene is central to fully understanding how these factors control developmental events.

Naidu, P S; Ludolph, D C; To, R Q; Hinterberger, T J; Konieczny, S F

1995-01-01

313

Casein kinase II increases the transcriptional activities of MRF4 and MyoD independently of their direct phosphorylation.  

PubMed Central

The myogenic regulatory factors (MRFs) are a subclass of a much larger group of basic helix-loop-helix transcription factors which includes members of the E protein such as E47, E2-2, and HEB. Although the MRFs are unique in their ability to confer a myogenic phenotype on nonmuscle cells, they require E protein partners to form a MRF-E protein heterodimer, which represents the functional myogenesis-inducing complex. The mechanisms controlling homodimer and heterodimer formation in vivo remain largely unknown, although it is likely that posttranslational modification of one or both basic helix-loop-helix partners is critical to this regulatory event. In this respect, MyoD and MRF4, both members of the MRF family, exist in vivo as phosphoproteins and contains multiple consensus phosphorylation sites, including sites for casein kinase II (CKII) phosphorylation. In this study, we demonstrate that overexpression of CKII increases the transcriptional activities of MRF4 and MyoD in vivo. Interestingly, mutation of the individual CKII sites within MRF4 and MyoF does not alter the ability of CKII to enhance MRF transcriptional activity, suggesting that the effect of CKII expression on the MRFs is indirect. Given that the MRFs require dimerization with E protein partners to activate muscle-specific transcription, the effects of CKII expression on E protein function also were examined. Our studies show that E47 serves as an in vitro substrate for CKII and that CKII-phosphorylated E-47 proteins no longer bind to DNA. These observations were confirmed by in vivo experiments showing that overexpressing of CKII produces a dramatic reduction in E47 homodimer-directed transcription. We conclude from these studies that CKII may act as a positive regulator of myogenesis by preventing E protein homodimers from binding to muscle gene regulatory elements.

Johnson, S E; Wang, X; Hardy, S; Taparowsky, E J; Konieczny, S F

1996-01-01

314

Lysophosphatidic acid prevents apoptosis in fibroblasts via G(i)-protein-mediated activation of mitogen-activated protein kinase.  

PubMed Central

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid with multiple biological functions. In the present study, we demonstrate that, besides its mitogenic activity, LPA is a potent survival factor, preventing serum-deprivation-induced apoptosis in fibroblasts and other cell types. Both the proliferative effect and survival activity of LPA are sensitive to the action of pertussis toxin (PTX), indicating that both processes are mediated by G(i) protein(s). We therefore focused on the role of G(i)-protein-mediated signalling events in the promotion of cell survival by LPA. In addition to activation of mitogen-activated protein kinase (MAPK), LPA stimulates a modest PTX-sensitive phosphorylation/activation of the serine/threonine kinase Akt, a survival mediator downstream of phosphoinositide 3-kinase (PI3K). Inhibition of PI3K with LY 294002 or wortmannin resulted in a marked inhibition of LPA-induced DNA synthesis, and yet the survival activity of LPA decreased by only 20-30%, suggesting a limited input of the PI3K-Akt cascade in LPA-induced cell survival. In contrast, inhibition of MAPK activation by the MEK-1 inhibitor, PD 98059, blocked both the proliferative and survival effects of LPA. These results indicate that LPA promotes cell survival largely via G(i)-protein-mediated activation of ERK1/ERK2, or other PD 98059-sensitive member(s) of the MAPK family.

Fang, X; Yu, S; LaPushin, R; Lu, Y; Furui, T; Penn, L Z; Stokoe, D; Erickson, J R; Bast, R C; Mills, G B

2000-01-01

315

Functional characterization of PAS and HES family bHLH transcription factors during the metamorphosis of the red flour beetle, Tribolium castaneum  

PubMed Central

The basic helix-loop-helix transcription factors are present in animals, plants and fungi and play important roles in the control of cellular proliferation, tissue differentiation, development and detoxification. Although insect genomes contain more than 50 Helix-Loop-Helix transcription factors, the functions of only a few are known. RNAi has become a widely used tool to knockdown the expression to analyze the function of genes. As RNAi works well in Tribolium castaneum, we utilized this insect and RNAi to determine functions of 19 bHLH transcription factors belonging to PAS and HES families during the larval stages of the red flour beetle, T. castaneum. We searched the genome sequence of T. castaneum and identified 53 bHLH genes. Phylogenetic analyses classified these 53 genes into ten families; PAS, HES, Myc/USF, Hand, Mesp, Shout, p48, NeuroD/Neurogenin, Atonal and AS-C. In RNAi studies, knocking-down the expression of seven members of the PAS and HES families affected the growth and development of T. castaneum. An inability to grow to reach critical weight to undergo metamorphosis, failure to complete larval-pupal or pupal-adult ecdysis and abnormal wing development are among the most common phenotypes observed in RNAi insects. Among the bHLH transcription factors studied, the steroid receptor coactivator (SRC) showed the most severe phenotypes. Knock-down in the expression of the gene coding for SRC caused growth arrest by affecting the regulation of lipid metabolism. These studies demonstrate the power of RNAi for functional characterization of members of the multigene families in this model insect.

Bitra, Kavita; Tan, Anjiang; Dowling, Ashley; Palli, Subba R.

2009-01-01

316

Citrus tristeza virus p23: a unique protein mediating key virus-host interactions.  

PubMed

The large RNA genome of Citrus tristeza virus (CTV; ca. 20 kb) contains 12 open reading frames, with the 3'-terminal one corresponding to a protein of 209 amino acids (p23) that is expressed from an abundant subgenomic RNA. p23, an RNA-binding protein with a putative zinc-finger domain and some basic motifs, is unique to CTV because no homologs have been found in other closteroviruses, including the type species of the genus Beet yellows virus (despite both viruses having many homologous genes). Consequently, p23 might have evolved for the specific interaction of CTV with its citrus hosts. From a functional perspective p23 has been involved in many roles: (i) regulation of the asymmetrical accumulation of CTV RNA strands, (ii) induction of the seedling yellows syndrome in sour orange and grapefruit, (iii) intracellular suppression of RNA silencing, (iv) elicitation of CTV-like symptoms when expressed ectopically as a transgene in several Citrus spp., and (v) enhancement of systemic infection (and virus accumulation) in sour orange and CTV release from the phloem in p23-expressing transgenic sweet and sour orange. Moreover, transformation of Mexican lime with intron-hairpin constructs designed for the co-inactivation of p23 and the two other CTV silencing suppressors results in complete resistance against the homologous virus. From a cellular point of view, recent data indicate that p23 accumulates preferentially in the nucleolus, being the first closterovirus protein with such a subcellular localization, as well as in plasmodesmata. These major accumulation sites most likely determine some of the functional roles of p23. PMID:23653624

Flores, Ricardo; Ruiz-Ruiz, Susana; Soler, Nuria; Sánchez-Navarro, Jesús; Fagoaga, Carmen; López, Carmelo; Navarro, Luis; Moreno, Pedro; Peña, Leandro

2013-05-03

317

Citrus tristeza virus p23: a unique protein mediating key virus-host interactions  

PubMed Central

The large RNA genome of Citrus tristeza virus (CTV; ca. 20 kb) contains 12 open reading frames, with the 3?-terminal one corresponding to a protein of 209 amino acids (p23) that is expressed from an abundant subgenomic RNA. p23, an RNA-binding protein with a putative zinc-finger domain and some basic motifs, is unique to CTV because no homologs have been found in other closteroviruses, including the type species of the genus Beet yellows virus (despite both viruses having many homologous genes). Consequently, p23 might have evolved for the specific interaction of CTV with its citrus hosts. From a functional perspective p23 has been involved in many roles: (i) regulation of the asymmetrical accumulation of CTV RNA strands, (ii) induction of the seedling yellows syndrome in sour orange and grapefruit, (iii) intracellular suppression of RNA silencing, (iv) elicitation of CTV-like symptoms when expressed ectopically as a transgene in several Citrus spp., and (v) enhancement of systemic infection (and virus accumulation) in sour orange and CTV release from the phloem in p23-expressing transgenic sweet and sour orange. Moreover, transformation of Mexican lime with intron-hairpin constructs designed for the co-inactivation of p23 and the two other CTV silencing suppressors results in complete resistance against the homologous virus. From a cellular point of view, recent data indicate that p23 accumulates preferentially in the nucleolus, being the first closterovirus protein with such a subcellular localization, as well as in plasmodesmata. These major accumulation sites most likely determine some of the functional roles of p23.

Flores, Ricardo; Ruiz-Ruiz, Susana; Soler, Nuria; Sanchez-Navarro, Jesus; Fagoaga, Carmen; Lopez, Carmelo; Navarro, Luis; Moreno, Pedro; Pena, Leandro

2013-01-01

318

A novel loop-loop recognition motif in the yeast ribosomal protein L30 autoregulatory RNA complex  

Microsoft Academic Search

The yeast Saccharomyces cerevisiae ribosomal protein L30 negatively autoregulates its production by binding to a helix-loop-helix structure formed in its pre-mRNA and its mRNA. A three-dimensional solution structure of the L30 protein in complex with its regulatory RNA has been solved using NMR spectroscopy. In the complex, the helix-loop-helix RNA adopts a sharply bent conformation at the internal loop region.

Hongyuan Mao; Susan A. White; James R. Williamson

1999-01-01

319

STAT2 Is a Primary Target for Measles Virus V Protein-Mediated Alpha/Beta Interferon Signaling Inhibition?  

PubMed Central

Measles virus, a member of the Morbillivirus family, infects millions of people each year despite the availability of effective vaccines. The V protein of measles virus is an important virulence factor that can interfere with host innate immunity by inactivating alpha/beta interferon (IFN-?/?) and IFN-? signaling through protein interactions with signal transducer and activator of transcription proteins STAT1 and STAT2. Here we demonstrate that although STAT1 interference results from protein interactions within a V protein N-terminal region encompassed by amino acids 110 to 130, detection of STAT1 interaction and IFN-? signaling inhibition requires the presence of cellular STAT2. Cell-specific variability in STAT1 interference was observed to correlate with V protein expression level. A more direct target for measles virus V protein-mediated IFN-?/? evasion is STAT2. Results indicate that the widely conserved C-terminal zinc finger domain of measles virus V protein is both necessary and sufficient to bind STAT2 and disrupt IFN-?/? signal transduction. Mutagenesis and molecular modeling define a contact surface for STAT2 association that includes aspartic acid residue 248 as critical for STAT2 interference and IFN antiviral immune suppression. These findings clearly define the molecular determinants for measles virus IFN evasion and validate specific targets as candidates for therapeutic intervention.

Ramachandran, Aparna; Parisien, Jean-Patrick; Horvath, Curt M.

2008-01-01

320

Basics of SCI Rehabilitation  

MedlinePLUS Videos and Cool Tools

Experts \\ The Basics of SCI Rehabilitation Topics Adult Injuries Spinal Cord Injury 101 The Basics of SCI Rehabilitation Preventing Pressure Sores Transition from Hospital to Home Spasticity, Physical Therapy- ...

321

Basic Chemistry Review  

NSDL National Science Digital Library

This assignment reviews basic of chemistry for students who should have had 2 introductory semesters of basic chemistry prior to enrolling in the Fundamental of Water Quality course for which the assignment is used. Assignment reviews basic equation balancing and questions about valence and concentration conversion that students will confront regularly in any geochemistry course.

Meixner, Thomas

322

Basic Construction Course Syllabus  

NSDL National Science Digital Library

This course syllabus provides an outline of a basic construction course. Students in this course learned "basic residential construction techniques with an emphasis on framing." The syllabus includes a basic course description and information on some class projects. This document may be downloaded in PDF file format.

Dickover, Jon

2011-12-07

323

Basic Cake Decorating Workbook.  

ERIC Educational Resources Information Center

|Included in this student workbook for basic cake decorating are the following: (1) Drawings of steps in a basic way to ice a layer cake, how to make a paper cone, various sizes of flower nails, various sizes and types of tin pastry tubes, and special rose tubes; (2) recipes for basic decorating icings (buttercream, rose paste, and royal icing);…

Bogdany, Mel

324

Phosphatase is responsible for run down, and probably G protein- mediated inhibition of inwardly rectifying K+ currents in guinea pig chromaffin cells  

Microsoft Academic Search

The mechanism of G protein-mediated inhibition of an inwardly rectifying K + current (IIR) in adrenal chromaffin cells was investigated using the whole-cell version of the patch clamp technique. In case of recording with use of ATP-containing patch solution, the IXR was well maintained; otherwise, it ran down within 15 min. This run down was not prevented by replacement with

M. Inoue; I. IMANAGA

1995-01-01

325

Investigation of cell adhesion to silica nanoparticle-decorated surfaces and the associated protein-mediated mechanisms  

NASA Astrophysics Data System (ADS)

Nanostructured materials have shown promise to improve the interface between prosthetic devices and living cells, tissues, and organs through the ability to evoke cell type-specific and size-selective functions from various cell types of in vivo importance. However, the underlying molecular level mechanisms responsible for enhancement of select cell functions on these materials are not fully understood. Silica particles of either 4, 20, or 100 nm diameters were successfully coated onto native-oxide coated silicon substrates in the range of 0 to 100% coverage by particles. The materials formulated and fabricated for the present study provide a controlled and characterized set of substrates needed for investigation of the effects of nanoscale features on the adsorption and conformation of proteins, and subsequent functions of mammalian cells that are critical to the clinical efficacy of biomaterials. The size of nanoscale surface features constituted by silica nanoparticles on native oxide-coated silicon pieces affected the adhesion of rat calvarial osteoblasts and rat skin fibroblasts differently. It was also demonstrated, for the first time, that a threshold density of nanoscale surface features is necessary to elicit size-selective, and cell type-specific, adhesion from osteoblasts or fibroblasts. Adsorption of fibronectin and vitronectin onto native oxide-coated silicon surfaces decorated with either 4, 20, or 100 nm diameter silica particles at either 25, 45, or 80% surface coverage was quantified and examined by scanning electron microscopy. Circular dichroism spectroscopy provided evidence that the secondary structures of fibronectin in the presence of either 4 or 20 nm diameter particles were similar, but fibronectin exhibited decreased beta sheet content and increased unordered structure in the presence of 100 nm particles. The secondary structure of vitronectin in the presence of silica particles exhibited similar levels of structure loss for all particle sizes examined. For the first time, this study offers insight into a molecular mechanism that is linked to nanostructured material surface feature size through quantified changes in protein structure and cell adhesion behavior. These results provide an explanation of the molecular level events occurring on nanostructured material surfaces that contribute to protein-mediated size-selective and cell type-specific responses of various cell types.

Ballard, Jake D.

326

BASIC for numerical quadrature  

Microsoft Academic Search

Although I have been involved in the development of programs for numerical evaluation of integrals for a number of years, it was only recently that I became aware of the importance of providing such tools in BASIC. I admit to having had a built-in predjudice against people using BASIC. To me it seemed that these people were either solving trivial

David K. Kahaner

1981-01-01

327

Basic Science Training Program.  

ERIC Educational Resources Information Center

These six learning modules were developed for Lake Michigan College's Basic Science Training Program, a workshop to develop good study skills while reviewing basic science. The first module, which was designed to provide students with the necessary skills to study efficiently, covers the following topics: time management; an overview of a study…

Brummel, Clete

328

Basic Science Training Program.  

ERIC Educational Resources Information Center

|These six learning modules were developed for Lake Michigan College's Basic Science Training Program, a workshop to develop good study skills while reviewing basic science. The first module, which was designed to provide students with the necessary skills to study efficiently, covers the following topics: time management; an overview of a study…

Brummel, Clete

329

Understanding Basic Mechanics: Workbook  

NSDL National Science Digital Library

This workbook is designed to be used with the Understanding Basic Mechanics textbook in an introductory calculus-based physics course for science or engineering students. The text presents the basic subject matter, facilitating reference, while the workbook is used to ensure students have understood the reading, can interpret it appropriately, and can apply it to diverse situations.

Reif, Frederick

2006-07-22

330

Basic Electronics I.  

ERIC Educational Resources Information Center

Designed for use in basic electronics programs, this curriculum guide is comprised of twenty-nine units of instruction in five major content areas: Orientation, Basic Principles of Electricity/Electronics, Fundamentals of Direct Current, Fundamentals of Alternating Current, and Applying for a Job. Each instructional unit includes some or all of…

Robertson, L. Paul

331

Improving CAI in BASIC.  

ERIC Educational Resources Information Center

This booklet is designed to help users understand the skills and concepts needed to develop effective computer assisted instruction (CAI) programs in any computer language and to polish and extend BASIC language programming skills. It assumes some idea of CAI and some BASIC programming (but not fluency), and can be used for self-study, in a…

Burrowes, Sharon; Burrowes, Ted

332

Basic Electronics I.  

ERIC Educational Resources Information Center

|Designed for use in basic electronics programs, this curriculum guide is comprised of twenty-nine units of instruction in five major content areas: Orientation, Basic Principles of Electricity/Electronics, Fundamentals of Direct Current, Fundamentals of Alternating Current, and Applying for a Job. Each instructional unit includes some or all of…

Robertson, L. Paul

333

Basic Multiple Regression  

NSDL National Science Digital Library

This page will perform basic multiple regression analysis for the case where there are several independent predictor variables, X1, X2, etc., and one dependent or criterion variable, Y. Requires import of data from a spreadsheet.

Lowry, Richard, 1940-

2008-06-25

334

Body Basics Library  

MedlinePLUS

... this medical library to find out about basic human anatomy, how it all functions, and what happens when things go wrong. Blood Bones, Muscles, and Joints Brain and Nervous System Digestive System ...

335

Basics of Online Searching.  

National Technical Information Service (NTIS)

Intended to teach the principles of interactive bibliographic searching to those with little or no prior experience, this textbook explains the basic elements of online information retrieval and compares the major database search systems. Its chapters add...

C. T. Wiley . A. Cochrane

1981-01-01

336

Ed's Basic Histology Gallery  

NSDL National Science Digital Library

This website introduces the basic concepts of histology. The site is organized by different anatomical structures and provides a tutorial, histology slices and quiz for students for each structure presented.

2010-03-02

337

Basic Agency Manual.  

National Technical Information Service (NTIS)

A basic reference manual is presented for use by all members of the Alliance for Regional Community Health, Inc. (ARCH) board, committees, task forces, advisory groups, and staff. Divided into four major sections, this guide encompasses orientation, organ...

1975-01-01

338

Understanding Basic Mechanics  

NSDL National Science Digital Library

This text is designed for an introductory calculus-based physics course for science or engineering students. Combined with its workbook, it forms a coherent introduction to basic mechanics. The text presents the basic subject matter, facilitating reference and review, while the workbook actively engages students in their learning to ensure that they have understood the reading, can interpret it appropriately, and can apply it to diverse situations.

Reif, Frederick

2006-07-22

339

Basic Principles of Ultrasound  

NSDL National Science Digital Library

Created by a team of medical professionals and health-care specialists, the main Echo Web site contains a wide range of resources dealing primarily with diagnostic ultrasounds, sonography, and the field of echocardiography. One of the most helpful of these resources is the Basic Principles of Ultrasound online course, which is available here at no cost. The course itself is divided into six different sections, along with a bibliography and FAQ area. Visitors can use the online course to learn about the basic principles of ultrasound, the basic science behind related devices and instruments, and the ways to use these devices safely. Instructors might also do well to use this website in conjunction with lectures on the subject, or as away to give students an additional resource to consult at their leisure.

2004-01-01

340

Myf5 is a novel early axonal marker in the mouse brain and is subjected to post-transcriptional regulation in neurons.  

PubMed

Myf5 is a key basic Helix-Loop-Helix transcription factor capable of converting many non-muscle cells into muscle. Together with MyoD it is essential for initiating the skeletal muscle programme in the embryo. We previously identified unexpected restricted domains of Myf5 transcription in the embryonic mouse brain, first revealed by Myf5-nlacZ(+/)(-) embryos (Tajbakhsh, S. and Buckingham, M. (1995) Development 121, 4077-4083). We have now further characterized these Myf5 expressing neurons. Retrograde labeling with diI, and the use of a transgenic mouse line expressing lacZ under the control of Myf5 regulatory sequences, show that Myf5 transcription provides a novel axonal marker of the medial longitudinal fasciculus (mlf) and the mammillotegmental tract (mtt), the earliest longitudinal tracts to be established in the embryonic mouse brain. Tracts projecting caudally from the developing olfactory system are also labelled. nlacZ and lacZ expression persist in the adult brain, in a few ventral domains such as the mammillary bodies of the hypothalamus and the interpeduncular nucleus, potentially derived from the embryonic structures where the Myf5 gene is transcribed. To investigate the role of Myf5 in the brain, we monitored Myf5 protein accumulation by immunofluorescence and immunoblotting in neurons transcribing the gene. Although Myf5 was detected in muscle myotomal cells, it was absent in neurons. This would account for the lack of myogenic conversion in brain structures and the absence of a neural phenotype in homozygous null mutants. RT-PCR experiments show that the splicing of Myf5 primary transcripts occurs correctly in neurons, suggesting that the lack of Myf5 protein accumulation is due to regulation at the level of mRNA translation or protein stability. In the embryonic neuroepithelium, Myf5 is transcribed in differentiated neurons after the expression of neural basic Helix-Loop-Helix transcription factors. The signalling molecules Wnt1 and Sonic hedgehog, implicated in the activation of Myf5 in myogenic progenitor cells in the somite, are also produced in the viscinity of the Myf5 expression domain in the mesencephalon. We show that cells expressing Wnt1 can activate neuronal Myf5-nlacZ gene expression in dissected head explants isolated from E9.5 embryos. Furthermore, the gene encoding the basic Helix-Loop-Helix transcription factor mSim1 is expressed in adjacent cells in both the somite and the brain, suggesting that signalling molecules necessary for the activation of mSim1 as well as Myf5 are present at these different sites in the embryo. This phenomenon may be widespread and it remains to be seen how many other potentially potent regulatory genes, in addition to Myf5, when activated do not accumulate protein at inappropriate sites in the embryo. PMID:10603349

Daubas, P; Tajbakhsh, S; Hadchouel, J; Primig, M; Buckingham, M

2000-01-01

341

Excel 1 - The Basics  

NSDL National Science Digital Library

Spreadsheets are used to keep track of numbers and other data in an organized fashion. It is kind of like a big calculator. In this lesson you will learn the basics of Microsoft\\'s spreadsheet program, Excel. The tutorial link below will take you through the very basics of Excel. You will start with an Overview of what Excel is and what kinds of documents it is used to create. Watch the video from the link on the right hand side of the screen. ...

Brewer, Mrs.

2006-11-25

342

Flattening basic blocks.  

SciTech Connect

The application of cross country elimination strategies requires access to the computational graph or at least subgraphs for certain scopes, e.g. a basic block. Under the presence of aliased variables the construction of these (sub)graphs encounters ambiguities. We propose an algorithm to construct ambiguity free subgraphs.

Utke, J.; Mathematics and Computer Science

2006-01-01

343

Basic Nuclear Physics.  

ERIC Educational Resources Information Center

|Basic concepts of nuclear structures, radiation, nuclear reactions, and health physics are presented in this text, prepared for naval officers. Applications to the area of nuclear power are described in connection with pressurized water reactors, experimental boiling water reactors, homogeneous reactor experiments, and experimental breeder…

Bureau of Naval Personnel, Washington, DC.

344

Basic Electronics II.  

ERIC Educational Resources Information Center

|Designed for use in basic electronics programs, this curriculum guide is comprised of 15 units of instruction. Unit titles are Review of the Nature of Matter and the P-N Junction, Rectifiers, Filters, Special Semiconductor Diodes, Bipolar-Junction Diodes, Bipolar Transistor Circuits, Transistor Amplifiers, Operational Amplifiers, Logic Devices,…

Willison, Neal A.; Shelton, James K.

345

Foundations of basic geometry  

Microsoft Academic Search

The basic notions of length, area and volume were not alien to the prehistoric civilizations. The pyramids, palaces and great\\u000a baths built more than 4000 years ago provide ample evidence. We begin our investigation of geometry with a discussion of areas\\u000a of simple geometric objects.

Jasbir S. Chahal

2006-01-01

346

Basic Drafting: Book Two.  

ERIC Educational Resources Information Center

|The second of a two-book course in drafting, this manual consists of 12 topics in the following units: sketching techniques, geometric constructions, orthographic views, dimensioning procedures, basic tolerancing, auxiliary views, sectional views, inking tools and techniques, axonometrics, oblique, perspective, and computer-aided drafting.…

Davis, Ronald; And Others

347

HIV/AIDS Basics  

MedlinePLUS

Home HIV/AIDS Basics Before we can stop any epidemic, we first have to recognize the magnitude of the disease. ... the facts: HIV/AIDS 101 Video What is HIV/AIDS? You need javascript enabled to view this content ...

348

Basic Skills Assessment  

ERIC Educational Resources Information Center

|After surveying 1,827 students in their final year at eighty randomly selected two-year and four-year public and private institutions, American Institutes for Research (2006) reported that approximately 30 percent of students in two-year institutions and nearly 20 percent of students in four-year institutions have only basic quantitative…

Yin, Alexander C.; Volkwein, J. Fredericks

2010-01-01

349

Basic Electricity. Part 1.  

ERIC Educational Resources Information Center

A primarily illustrated introduction to the basics of electricity is presented in this guide, the first of a set of four designed for the student interested in a vocation in electrical work. This guide is intended for the first-year student and provides mostly diagrams with accompanying defintions/information in three units, each covering one of…

Kilmer, Donald C.

350

FULA BASIC COURSE.  

ERIC Educational Resources Information Center

|THIS BEGINNING COURSE IS AN INTRODUCTION TO FULA (KNOWN VARIOUSLY AS FULANI, FUL, PEUL, OR PHEUL), A NIGER-CONGO LANGUAGE SPOKEN THROUGHOUT THE GRASSLAND AREAS OF WEST AFRICA FROM THE ATLANTIC TO CAMEROUN. THE TEXT IS ONE OF A SERIES OF SHORT BASIC COURSES IN SELECTED AFRICAN LANGUAGES BEING PREPARED BY THE FOREIGN SERVICE INSTITUTE. IT IS…

SWIFT, LLOYD B.; AND OTHERS

351

Basic Pneumatics. Instructor's Guide.  

ERIC Educational Resources Information Center

|This instructor's guide is designed for use by industrial vocational teachers in teaching a course on basic pneumatics. Covered in the individual units are the following topics: an introduction to pneumatics (including the operation of a service station hoist); fundamentals and physical laws; air compressors (positive displacement compressors;…

Fessehaye, Michael

352

Focus on Basics, 1997.  

ERIC Educational Resources Information Center

Together, these four newsletters contain 36 articles devoted to adult literacy research and practice and the relationship between them. The following articles are included: "A Productive Partnership" (Richard J. Murnane, Bob Bickerton); "Welcome to 'Focus on Basics'" (Barbara Garner); "Applying Research on the Last Frontier" (Karen Backlund, Kathy…

Focus on Basics, 1997

1997-01-01

353

GPS Receiver Basics  

NSDL National Science Digital Library

Students familiarize themselves â through trial and error â with the basics of GPS receiver operation. They view a receiver's satellite visibility screen as they walk in various directions and monitor their progress on the receiver's map. Students may enter waypoints and use the GPS information to guide them back to specific locations.

Integrated Teaching And Learning Program

354

Lippincott Basic Reading Program.  

ERIC Educational Resources Information Center

This program, included in "Effective Reading Programs...," serves 459 students in grades 1-3 at 15 elementary schools. The program employs a diagnostic-prescriptive approach to instruction in a nongraded setting through the use of the Lippincott Basic Reading program. When a child enters the program, he is introduced to a decoding process that…

Monterey Peninsula Unified School District, Monterey, CA.

355

Czech Basic Course: Folklore.  

ERIC Educational Resources Information Center

This booklet is designed for use in the advanced phase of the Defense Language Institute's "Basic Course" in Czech. It is used in the advanced phase as a part of cultural background information. Reading selections, with vocabulary lists, include: (1) ethnography; (2) incantations and spells; (3) proverbs, sayings, and weather lore; (4) fairy tales…

Defense Language Inst., Washington, DC.

356

Focus on Basics, 1998.  

ERIC Educational Resources Information Center

This volume contains the four 1998 quarterly issues of this newsletter that present best practices, current research on adult learning and literacy, and information on how research is used by adult basic education teachers, counselors, program administrators, and policy makers. The following are among the major articles included: "Power, Literacy,…

Focus on Basics, 1998

1998-01-01

357

Basics of solar energy  

Microsoft Academic Search

Basic data related to solar energy are summarized, including mass, radius, average density, and average surface temperature of the sun, as well as definitions of the common terminology. Equations are given for the calculation of the solar declination and the length of the day.

A. A. M. Sayigh

1979-01-01

358

Basic Engineer Equipment Mechanic.  

ERIC Educational Resources Information Center

|This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the skills needed by basic engineer equipment mechanics. Addressed in the four individual units of the course are the following topics: mechanics and their tools (mechanics, hand tools, and…

Marine Corps Inst., Washington, DC.

359

Projectable Basic Electronics Kit.  

ERIC Educational Resources Information Center

|Outlines advantages derived from constructing and using a Projectable Basic Electronics Kit and provides: (1) list of components; (2) diagrams of 10 finished components (resistor; capacitor; diode; switch; bulb; transistor; meter; variable capacitor; coil; connecting terminal); and (3) diode and transistor activities. (JN)|

H'ng, John; And Others

1982-01-01

360

Cloud Physics: The Basics  

NSDL National Science Digital Library

This website from the Oklahoma Weather Modification Program encourages students to initiate a debate on the controversy surrounding the issue of inducing or enhancing precipitation. The exercise describes the two basic tenets of cloud seeding: the Static Phase Hypothesis and the Dynamic Phase Hypothesis. Also provided are links to a weather and climate glossary and further information about clouds and precipitation.

Klatt, Michael L.

2008-01-14

361

Basics of Cell Culture  

NSDL National Science Digital Library

These manuals are used in the Stem Cell Culture Course at City College of San Francisco. This course is about general mammalian cell culture techniques but includes a laboratory exercise using stem cells (takes 3 weeks to complete). The course is taught to high school students but the materials are also used for college students. Laboratory exercises provide instruction in basic techniques of routine cell culture using common cell lines before progressing to differentiation of mouse embryonic stem cells. Photographs and explanations of common equipment (laminar flow hood, inverted microscope, etc.) and reagents are provided. Laboratory exercises include the following: Basic Aseptic Technique; Media Preparation; Plating cells from frozen stock; Cell counting and plating; Survival assay (UV); Live Cell Identification; Transfection; Freezing cells; Stem cell differentiation. A student lab manual and an instructor manual are provided.

Afshar, Golnar

2012-03-12

362

Basic Nanotechnology Processes  

NSDL National Science Digital Library

The National Center for Nanotechnology Applications and Career Knowledge (NACK) Center is an organization committed to supporting twoâÂÂyear degree programs in micro and nanotechnology. The center offers online educational material for curriculum enhancement in this subject field. One of these courses focuses on basic nanotechnology processes. The material is a âÂÂhands-on introduction to the processing involved in âÂÂtop downâÂÂ, âÂÂbottom upâÂÂ, and hybrid nanofabrication.â Downloadable features include topics such as introductions to basic pattern transfer, wet etching and uses of plasmas in processing. Additionally, resources on chemical vapor and physical deposition are available in this unit. The site requires a free log-in for access to the material.

2010-03-05

363

Basic plasma physics II  

Microsoft Academic Search

The basic physics of classical ideal plasmas is presented in reviews of recent theoretical and experimental investigations, with an emphasis on nonlinear interactions violating the assumptions of weak turbulence. Topics examined include Kolmogorov spectra, parametric instabilities in magnetoactive plasmas, collapse and self-focusing of Langmuir waves, collective dissipation and transport, spontaneous reconnection of magnetic-field lines in a collisionless plasma, collective-beam\\/plasma interaction,

A. A. Galeev; R. N. Sudan

1984-01-01

364

Weather Basics: Local Circulation  

NSDL National Science Digital Library

This resource explains the basic forces behind atmospheric circulation on a local scale. Topics include phenomena that help to drive circulation, such as solar heating, gravity, pressure, the coriolis effect, and friction. Two types of local circulation patterns are also discussed: mountain and valley breezes; and land and sea breezes. Photos and diagrams are provided to augment the written discussion, and links to related websites are also included.

2005-03-10

365

Basics of Space Flight  

NSDL National Science Digital Library

This training module was designed to help the user identify and grasp basic concepts associated with space travel and deep space missions. Separate sections deal with topics such as the physical environment of space (solar system, gravity, orbital mechanics), flight projects (mission concepts, system requirements, design, onboard systems and instruments), and flight operations (launch, cruise, encounter). Links to related topics are embedded in the text.

366

Basics of Developing Questionnaires  

NSDL National Science Digital Library

Whether developing questions for questionnaires or interviews or focus groups, there are certain guidelines that help to ensure that respondents provide information that is useful and can later be analyzed. This resource offers advice on developing questions for interviews or focus groups. It contains basics conducting the interviews, providing directions to respondents as well as guidelines for composing the content and wording of the questionnaire. This resource is aimed for use in workshops/conferences and is intended for novice evaluators.

Mcnamara, Carter

367

Basic Liquid Chromatography  

NSDL National Science Digital Library

The online textbook, Basic Liquid Chromatography, is provided by Dr. Yuri Kazakevich and Dr. Harold McNair of Seton Hall University. For those needing review or an introduction to the subject, the well designed and easily read document contains a wealth of information. Sections include an introduction, instrumentation, detectors, theory, adsorbents, reversed phase, gel permeation chromatography, column selection, pH effect, and even an online short course.

McNair, Harold Monroe, 1933-.; Kazakevich, Yuri.

1996-01-01

368

Population: Basic Statistics  

NSDL National Science Digital Library

This lesson reinforces the idea that Earth's population, including the population of the United States, is gowing at a dramatic rate. It discusses some of the basics of demography, the study of population and its changes, and introduces key terms used to describe a population. The lesson inlcudes an activity in which students use an online reference to look up some population statistics and answer questions related to them.

Rhinehart, Ken; Pratte, John

369

Risk communication basics  

SciTech Connect

In low-trust, high-concern situations, 50% of your credibility comes from perceived empathy and caring, demonstrated in the first 30 s you come in contact with someone. There is no second chance for a first impression. These and other principles contained in this paper provide you with a basic level of understanding of risk communication. The principles identified are time-tested caveats and will assist you in effectively communicating technical information.

Corrado, P.G. [Lawrence Livermore National Laboratory, CA (United States)

1995-12-31

370

The Basics of MRI  

NSDL National Science Digital Library

The Basics of MRI is a hypertextbook by Dr. Joseph Hornak of the Rochester Institute of Technology that focuses on the mathematics and physics of magnetic resonance imaging. "Exponential Functions," "Differentials and Integrals," and "Coordinate Transformation" are just a few of the mathematical topics discussed. The physics behind MRI is broken down into the following chapters: "Spin Physics," "NMR Spectroscopy," "Fourier Transforms," "Imaging Principles," and "Fourier Transform Imaging Principles." Hornak has also included a multitude of information on imaging techniques, presentation, and hardware. Those concerned with what occurs during a MRI exam, rather than the math and physics of MRI, will want to consult the chapter entitled "Your MRI Exam."

Hornak, Joseph P.

1996-01-01

371

Basic immunology: a primer.  

PubMed

This article is intended to bring practicing physicians up to date on the current state of knowledge regarding the basic components and processes of the immune system. It discusses the role of the immune system and the importance of self-tolerance and describes the main cellular and noncellular entities involved in the immune response. It also details immune processes such as the lymphocyte selection process leading to self tolerance; antigen processing and presentation; cell signaling, activation, and co-stimulation; and the actions of cytokines and other signaling molecules. PMID:15191067

Helm, Thomas

2004-05-01

372

Atomic Basic Blocks  

NASA Astrophysics Data System (ADS)

Die Entscheidung, einen zeit- bzw. ereignisgesteuerten Ansatz für ein Echtzeitsystem zu verwenden, ist schwierig und sehr weitreichend. Weitreichend vor allem deshalb, weil diese beiden Ansätze mit äußerst unterschiedlichen Kontrollflussabstraktionen verknüpft sind, die eine spätere Migration zum anderen Paradigma sehr schwer oder gar unmöglich machen. Wir schlagen daher die Verwendung einer Zwischendarstellung vor, die unabhängig von der jeweils verwendeten Kontrollflussabstraktion ist. Für diesen Zweck verwenden wir auf Basisblöcken basierende Atomic Basic Blocks (ABB) und bauen darauf ein Werkzeug, den Real-Time Systems Compiler (RTSC) auf, der die Migration zwischen zeit- und ereignisgesteuerten Systemen unterstützt.

Scheler, Fabian; Mitzlaff, Martin; Schröder-Preikschat, Wolfgang

373

Understanding Basic Mechanics  

NASA Astrophysics Data System (ADS)

An extremely lucid introduction to physics and reasoning methods containing a judicious selection and sequencing of material that enables students to learn without being overwhelmed and acquire important knowledge for future work. Provides detailed instruction of a problem-solving strategy for both quantitative and qualitative problems. Consists of two closely coordinated parts--the text is designed to present basic subject matter as well as facilitate reference and review; the workbook ensures that students have understood what they have read, can interpret it and apply the information to diverse situations.

Reif, Frederick

1995-01-01

374

Understanding Basic Mechanics , Workbook  

NASA Astrophysics Data System (ADS)

An extremely lucid introduction to physics and reasoning methods containing a judicious selection and sequencing of material that enables students to learn without being overwhelmed and acquire important knowledge for future work. Provides detailed instruction of a problem-solving strategy for both quantitative and qualitative problems. Consists of two closely coordinated parts--the text is designed to present basic subject matter as well as facilitate reference and review; the workbook ensures that students have understood what they have read, can interpret it and apply the information to diverse situations.

Reif, Frederick

1995-01-01

375

Electrostatic Interactions between Capsid and Scaffolding Proteins Mediate the Structural Polymorphism of a Double-stranded RNA Virus*  

PubMed Central

Capsid proteins that adopt distinct conformations constitute a paradigm of the structural polymorphism of macromolecular assemblies. We show the molecular basis of the flexibility mechanism of VP2, the capsid protein of the double-stranded RNA virus infectious bursal disease virus. The initial assembly, a procapsid-like structure, is built by the protein precursor pVP2 and requires VP3, the other infectious bursal disease virus major structural protein, which acts as a scaffold. The pVP2 C-terminal region, which is proteolyzed during virus maturation, contains an amphipathic ?-helix that acts as a molecular switch. In the absence of VP3, efficient virus-like particle assembly occurs when the structural unit is a VP2-based chimeric protein with an N-terminal-fused His6 tag. The His tag has a positively charged N terminus and a negatively charged C terminus, both important for virion-like structure assembly. The charge distributions of the VP3 C terminus and His tag are similar. We tested whether the His tag emulates the role of VP3 and found that the presence of a VP3 C-terminal peptide in VP2-based chimeric proteins resulted in the assembly of virus-like particles. We analyzed the electrostatic interactions between these two charged morphogenetic peptides, in which a single residue was mutated to impede the predicted interaction, followed by a compensatory double mutation to rescue electrostatic interactions. The effects of these mutations were monitored by following the virus-like and/or virus-related assemblies. Our results suggest that the basic face of the pVP2 amphipathic ?-helix interacts with the acidic region of the VP3 C terminus and that this interaction is essential for VP2 acquisition of competent conformations for capsid assembly.

Saugar, Irene; Irigoyen, Nerea; Luque, Daniel; Carrascosa, Jose L.; Rodriguez, Jose F.; Caston, Jose R.

2010-01-01

376

Determinants of myogenic specificity within MyoD are required for noncanonical E box binding.  

PubMed

The MyoD family of basic helix-loop-helix (bHLH) transcription factors has the remarkable ability to induce myogenesis in vitro and in vivo. This myogenic specificity has been mapped to two amino acids in the basic domain, an alanine and threonine, referred to as the myogenic code. These essential determinants of myogenic specificity are conserved in all MyoD family members from worms to humans, yet their function in myogenesis is unclear. Induction of the muscle transcriptional program requires that MyoD be able to locate and stably bind to sequences present in the promoter regions of critical muscle genes. Recent studies have shown that MyoD binds to noncanonical E boxes in the myogenin gene, a critical locus required for myogenesis, through interactions with resident heterodimers of the HOX-TALE transcription factors Pbx1A and Meis1. In the present study, we show that the myogenic code is required for MyoD to bind to noncanonical E boxes in the myogenin promoter and for the formation of a tetrameric complex with Pbx/Meis. We also show that these essential determinants of myogenesis are sufficient to confer noncanonical E box binding to the E12 basic domain. Thus, these data show that noncanonical E box binding correlates with myogenic potential, and we speculate that the myogenic code residues in MyoD function as myogenic determinants via their role in noncanonical E box binding and recognition. PMID:17562853

Heidt, Analeah B; Rojas, Anabel; Harris, Ian S; Black, Brian L

2007-06-11

377

Basics of AC Motors  

NSDL National Science Digital Library

This course is one of the quickStep series offered by Siemens in AC Motors. These are FREE on-line industrial knowledge building tutorials. quickSTEPs are a great start for industry novices moving into technical jobs or staff in operational support rolls. They can also be very effectively used as out of class assignments for review or to build fundamental skills. Each course includes: an online tutorial organized as a number of units, lessons with self check quiz questions, a glossary of terms, a self-check final exam with scoring, an extensive downloadable PDF study guide. This course covers: motor basics, NEMA motors, Siemens motorr, final exam, a glossary, plus a 116 page study guide.

2008-11-26

378

Basics of Circuit Breakers  

NSDL National Science Digital Library

This course is one of the quickStep series offered by Siemens in Circuit Breakers. These are FREE on-line industrial knowledge building tutorials. quickSTEPs are a great start for industry novices moving into technical jobs or staff in operational support rolls. They can also be very effectively used as out of class assignments for review or to build fundamental skills. Each course includes: an online tutorial organized as a number of units, lessons with self check quiz questions, a glossary of terms, a self-check final exam with scoring, an extensive downloadable PDF study guide. This course offers: basic concepts, breakers part one, breakers part two, a final exam, a glossary and an 88 page study guide.

2008-11-06

379

Basic AC Theory  

NSDL National Science Digital Library

reated by Tony R. Kuphaldt with help from Harvey Lew, Duane Damiano, Mark D. Zarella, John Symonds, and Jason Starck, this chapter of All About Circuit's second volume on Alternating Current describes the basic theory and principles at work. The chapter is divided into six sections: What is alternating current?, AC waveforms, Measurements of AC magnitude, Simple AC circuit calculations, AC phase, and Principles of radio. Each section has clear illustrations and a concise, bulleted review of what was covered at the end. There is also a link to the All About Circuits forums, where contributors and other visitors discuss the material presented. This is an excellent resource for educators in physics and electronic engineering classrooms to introduce lessons or units on alternating current.

Kuphaldt, Tony R.

2008-07-15

380

Basic and Clinical Neurosciences  

NSDL National Science Digital Library

Columbia University's College of Physicians and Surgeons has been a leader in medical education for over a century, and this website is provided as public service for those in the field of medicine and neuroscience. The website provides a series of lectures and videos that provide a "comprehensive and concise review of the neurosciences." It's best to start by reading the executive summary, and then click on over to the "Topics and Speakers" area. Here visitors can look over several dozen lectures that include "Basic Mechanisms of Pain", "Molecular Genetics", and "Neurobiology of Schizophrenia". The lectures are all of very high quality, and visitors who are seeking additional information should look through the "References and Resources" area for external links to relevant medical organizations, research institutes, and academic departments.

381

Basic Concepts of Electricity  

NSDL National Science Digital Library

All About Circuits is a website that âÂÂprovides a series of online textbooks covering electricity and electronics.â Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students, teachers, and anyone who is interested in learning more about electronics. This particular section, Basic Concepts of Electricity, is the first chapter in Volume I. Topics covered in this chapter include: static electricity, conductors, insulators, electron flow, electric circuits, voltage, current, and resistance. Diagrams and detailed descriptions of concepts are included throughout the chapter to provide users with a comprehensive lesson. Visitors to the site are also encouraged to discuss concepts and topics using the All About Circuits discussion forums (registration with the site is required to post materials).

Kuphaldt, Tony R.

2008-07-04

382

Joint Infection (Beyond the Basics)  

MedlinePLUS

... The Basics) Patient information: Septic arthritis (The Basics) Pseudomonas aeruginosa skin, soft tissue, and bone infections Septic arthritis ... Clinical manifestations and diagnosis of prosthetic joint infections Pseudomonas aeruginosa skin, soft tissue, and bone infections Septic arthritis ...

383

Synergistic interactions of lipids and myelin basic protein  

NASA Astrophysics Data System (ADS)

This report describes force measurements and atomic force microscope imaging of lipid-protein interactions that determine the structure of a model membrane system that closely mimics the myelin sheath. Our results suggest that noncovalent, mainly electrostatic and hydrophobic, interactions are responsible for the multilamellar structure and stability of myelin. We find that myelin basic protein acts as a lipid coupler between two apposed bilayers and as a lipid "hole-filler," effectively preventing defect holes from developing. From our protein-mediated-adhesion and force-distance measurements, we develop a simple quantitative model that gives a reasonably accurate picture of the molecular mechanism and adhesion of bilayer-bridging proteins by means of noncovalent interactions. The results and model indicate that optimum myelin adhesion and stability depend on the difference between, rather than the product of, the opposite charges on the lipid bilayers and myelin basic protein, as well as on the repulsive forces associated with membrane fluidity, and that small changes in any of these parameters away from the synergistically optimum values can lead to large changes in the adhesion or even its total elimination. Our results also show that the often-asked question of which membrane species, the lipids or the proteins, are the "important ones" may be misplaced. Both components work synergistically to provide the adhesion and overall structure. A better appreciation of the mechanism of this synergy may allow for a better understanding of stacked and especially myelin membrane structures and may lead to better treatments for demyelinating diseases such as multiple sclerosis. lipid-protein interactions | myelin membrane structure | membrane adhesion | membrane regeneration/healing | demyelinating diseases

Hu, Yufang; Doudevski, Ivo; Wood, Denise; Moscarello, Mario; Husted, Cynthia; Genain, Claude; Zasadzinski, Joseph A.; Israelachvili, Jacob

2004-09-01

384

A chimeric enhancer-of-split transcriptional activator drives neural development and achaete-scute expression.  

PubMed Central

Drosophila melanogaster neurogenesis requires the opposing activities of two sets of basic helix-loop-helix (bHLH) proteins: proneural proteins, which confer on cells the ability to become neural precursors, and the Enhancer-of-split [E(spl)] proteins, which restrict such potential as part of the lateral inhibition process. Here, we test if E(spl) proteins function as promoter-bound repressors by examining the effects on neurogenesis of an E(spl) derivative containing a heterologous transcriptional activation domain [E(spl) m7Act (m7Act)]. In contrast to the wild-type E(spl) proteins, m7Act efficiently induces neural development, indicating that it binds to and activates target genes normally repressed by E(spl). Mutations in the basic domain disrupt m7Act activity, suggesting that its effects are mediated through direct DNA binding. m7Act causes ectopic transcription of the proneural achaete and scute genes. Our results support a model in which E(spl) proteins normally regulate neurogenesis by direct repression of genes at the top of the neural determination pathway.

Jimenez, G; Ish-Horowicz, D

1997-01-01

385

DNA bending by bHLH charge variants  

PubMed Central

We wish to understand the role of electrostatics in DNA stiffness and bending. The DNA charge collapse model suggests that mutual electrostatic repulsions between neighboring phosphates significantly contribute to DNA stiffness. According to this model, placement of fixed charges near the negatively charged DNA surface should induce bending through asymmetric reduction or enhancement of these inter-phosphate repulsive forces. We have reported previously that charged variants of the elongated basic-leucine zipper (bZIP) domain of Gcn4p bend DNA in a manner consistent with this charge collapse model. To extend this result to a more globular protein, we present an investigation of the dimeric basic-helix–loop–helix (bHLH) domain of Pho4p. The 62 amino acid bHLH domain has been modified to position charged amino acid residues near one face of the DNA double helix. As observed for bZIP charge variants, DNA bending toward appended cations (away from the protein:DNA interface) is observed. However, unlike bZIP proteins, DNA is not bent away from bHLH anionic charges. This finding can be explained by the structure of the more globular bHLH domain which, in contrast to bZIP proteins, makes extensive DNA contacts along the binding face.

McDonald, Robert J.; Kahn, Jason D.; Maher, L. James

2006-01-01

386

Proneural genes in neocortical development.  

PubMed

Neurons, astrocytes and oligodendrocytes arise from CNS progenitor cells at defined times and locations during development, with transcription factors serving as key determinants of these different neural cell fates. An emerging theme is that the transcription factors that specify CNS cell fates function in a context-dependent manner, regulated by post-translational modifications and epigenetic alterations that partition the genome (and hence target genes) into active or silent domains. Here we profile the critical roles of the proneural genes, which encode basic-helix-loop-helix (bHLH) transcription factors, in specifying neural cell identities in the developing neocortex. In particular, we focus on the proneural genes Neurogenin 1 (Neurog1), Neurog2 and Achaete scute-like 1 (Ascl1), which are each expressed in a distinct fashion in the progenitor cell pools that give rise to all of the neuronal and glial cell types of the mature neocortex. Notably, while the basic functions of these proneural genes have been elucidated, it is becoming increasingly evident that tight regulatory controls dictate when, where and how they function. Current efforts to better understand how proneural gene function is regulated will not only improve our understanding of neocortical development, but are also critical to the future development of regenerative therapies for the treatment of neuronal degeneration or disease. PMID:23999125

Wilkinson, G; Dennis, D; Schuurmans, C

2013-08-30

387

Three transcription factors, HFR1, LAF1 and HY5, regulate largely independent signaling pathways downstream of phytochrome A.  

PubMed

Among signaling components downstream of phytochrome A (phyA), HY5, HFR1 and LAF1 are transcription factors that regulate expression of phyA-responsive genes. Previous work has shown that FHY1/FHL distribute phyA signals directly to HFR1 and LAF1, both of which regulate largely independent pathways, but the relationship of HY5 to these two factors was unclear. Here, we investigated the genetic relationship among the genes encoding these three transcription factors, HY5, HFR1 and LAF1. Analyses of double and triple mutants showed that HY5, a basic leucine zipper (bZIP) factor, HFR1, a basic helix-loop-helix (bHLH) factor, and LAF1, a Myb factor, independently transmit phyA signals downstream. We showed that HY5 but not its homolog, HYH, could interact with HFR1 and LAF1; on the other hand, FHY1 and its homolog, FHL did not interact with HY5 or HYH. Together, our results suggest that HY5 transmits phyA signals through an FHY1/FHL-independent pathway but it may also modulate FHY1/FHL signal through its interaction with HFR1 and LAF1. PMID:23503597

Jang, In-Cheol; Henriques, Rossana; Chua, Nam-Hai

2013-03-15

388

Phosphorylation inhibits DNA-binding of alternatively spliced aryl hydrocarbon receptor nuclear translocator  

SciTech Connect

The basic helix-loop-helix/PER-ARNT-SIM homology (bHLH/PAS) transcription factor ARNT (aryl hydrocarbon receptor nuclear translocator) is a key component of various pathways which induce the transcription of cytochrome P450 and hypoxia response genes. ARNT can be alternatively spliced to express Alt ARNT, containing an additional 15 amino acids immediately N-terminal to the DNA-binding basic region. Here, we show that ARNT and Alt ARNT proteins are differentially phosphorylated by protein kinase CKII in vitro. Phosphorylation had an inhibitory effect on DNA-binding to an E-box probe by Alt ARNT, but not ARNT, homodimers. This inhibitory phosphorylation occurs through Ser77. Moreover, a point mutant, Alt ARNT S77A, shows increased activity on an E-box reporter gene, consistent with Ser77 being a regulatory site in vivo. In contrast, DNA binding by an Alt ARNT/dioxin receptor heterodimer to the xenobiotic response element is not inhibited by phosphorylation with CKII, nor does Alt ARNT S77A behave differently from wild type Alt ARNT in the context of a dioxin receptor heterodimer.

Kewley, Robyn J. [School of Molecular and Biomedical Science (Biochemistry), Centre for the Molecular Genetics of Development, University of Adelaide, SA 5005 (Australia)]. E-mail: rkewley@csu.edu.au; Whitelaw, Murray L. [School of Molecular and Biomedical Science (Biochemistry), Centre for the Molecular Genetics of Development, University of Adelaide, SA 5005 (Australia)

2005-12-09

389

Reduced expression of IL-12 receptor beta2 and IL-18 receptor alpha genes in natural killer cells and macrophages derived from B6-mi/mi mice.  

PubMed

The mi transcriptional factor (MITF) is a basic helix-loop-helix leucine zipper-type transcriptional factor. The mi mutant allele encodes an abnormal MITF, in which one out of four consecutive arginines is deleted in the basic domain. The VGA-9-tg (tg) allele is another mutant allele and considered to be a null mutant allele. C57BL/6 (B6)-mi/mi mice showed abnormal phenotypes of natural killer (NK) cells and macrophages, whereas B6-tg/tg mice did not. The expression levels of the genes for the interleukin-12 receptor (IL-12R) beta2 and IL-18Ralpha were reduced in both the NK cells and macrophages of B6-mi/mi mice, while the expression levels of the corresponding genes in B6-tg/tg mice were unaffected. The B6-mi/mi NK cells and B6-mi/mi macrophages showed impaired responses to stimulation with IL-12, IL-18, and IL-12 plus IL-18 stimulation. The abnormal NK cell and macrophage of B6-mi/mi mice appear to be due to decreased expression of the IL-12Rbeta2 and IL-18Ralpha genes. PMID:15492754

Kataoka, Tatsuki R; Komazawa, Nobuyasu; Oboki, Keisuke; Morii, Eiichi; Nakano, Toru

2005-01-01

390

Association between seed dormancy and pericarp color is controlled by a pleiotropic gene that regulates abscisic acid and flavonoid synthesis in weedy red rice.  

PubMed

Seed dormancy has been associated with red grain color in cereal crops for a century. The association was linked to qSD7-1/qPC7, a cluster of quantitative trait loci for seed dormancy/pericarp color in weedy red rice. This research delimited qSD7-1/qPC7 to the Os07g11020 or Rc locus encoding a basic helix-loop-helix family transcription factor by intragenic recombinants and provided unambiguous evidence that the association arises from pleiotropy. The pleiotropic gene expressed in early developing seeds promoted expression of key genes for biosynthesis of abscisic acid (ABA), resulting in an increase in accumulation of the dormancy-inducing hormone; activated a conserved network of eight genes for flavonoid biosynthesis to produce the pigments in the lower epidermal cells of the pericarp tissue; and enhanced seed weight. Thus, the pleiotropic locus most likely controls the dormancy and pigment traits by regulating ABA and flavonoid biosynthetic pathways, respectively. The dormancy effect could be eliminated by a heat treatment, but could not be completely overcome by gibberellic acid or physical removal of the seed maternal tissues. The dormancy-enhancing alleles differentiated into two groups basically associated with tropical and temperate ecotypes of weedy rice. Of the pleiotropic effects, seed dormancy could contribute most to the weed adaptation. Pleiotropy prevents the use of the dormancy gene to improve resistance of white pericarp cultivars against pre-harvest sprouting through conventional breeding approaches. PMID:21954164

Gu, Xing-You; Foley, Michael E; Horvath, David P; Anderson, James V; Feng, Jiuhuan; Zhang, Lihua; Mowry, Chase R; Ye, Heng; Suttle, Jeffrey C; Kadowaki, Koh-ichi; Chen, Zongxiang

2011-09-27

391

Protein secretion in gram-negative bacteria: assembly of the three components of ABC protein-mediated exporters is ordered and promoted by substrate binding.  

PubMed Central

One of the strategies used by Gram-negative bacteria to secrete proteins across the two membranes which delimit the cells, is sec independent and dedicated to proteins lacking an N-terminal signal peptide. It depends on ABC protein-mediated exporters, which consist of three cell envelope proteins, two inner membrane proteins, an ATPase (the ABC protein), a membrane fusion protein (MFP) and an outer membrane polypeptide. Erwinia chrysanthemi metalloproteases B and C and Serratia marcescens hemoprotein HasA are secreted by such homologous pathways and interact with the ABC protein. Using as protein substrates HasA and GST-PrtC, a chimeric protein which has a glutathione S-transferase moiety fused to a large C-terminal domain of protease C, we developed a simple system to identify proteins bound to the substrate based on substrate affinity-chromatography using heme- or glutathione-agarose. We show an ordered association between the protein substrates and the three exporter components: the substrate recognizes the ABC protein which interacts with the MFP which in turn binds the outer membrane component. Substrate binding is required for assembly of the three components. Images

Letoffe, S; Delepelaire, P; Wandersman, C

1996-01-01

392

Protein-mediated layer-by-layer synthesis of TiO?(B)/anatase/carbon coating on nickel foam as negative electrode material for lithium-ion battery.  

PubMed

Through an aqueous, protein-mediated layer-by-layer titania deposition process, we have fabricated a protamine/titania composite layer on nickel foam. The coating was composed of amorphous carbon and TiO2(B)/anatase nanoparticles and formed upon organic pyrolysis under a reducing atmosphere (5% H2-Ar mixture). X-ray diffraction analyses, Auger electron spectroscopy, and high-resolution transmission electron microscopy revealed that the obtained coatings contained fine monoclinic TiO2(B) and anatase nanocrystals, along with amorphous carbon. Moreover, the coating can be used as a binder-free negative electrode material for lithium-ion batteries and exhibits high reversible capacity and fast charge-discharge properties; a reversible capacity of 245 mAh g(-1) was obtained at a current density of 50 mA g(-1), and capacities of 167 and 143 mAh g(-1) were obtained at current densities of 1 and 2 A g(-1), respectively. PMID:23597025

Wang, Xiaobo; Yan, Yong; Hao, Bo; Chen, Ge

2013-04-18

393

Basic science of pain.  

PubMed

The origin of the theory that the transmission of pain is through a single channel from the skin to the brain can be traced to the philosopher and scientist René Descartes. This simplified scheme of the reflex was the beginning of the development of the modern doctrine of reflexes. Unfortunately, Descartes' reflex theory directed both the study and treatment of pain for more than 330 years. It is still described in physiology and neuroscience textbooks as fact rather than theory. The gate control theory proposed by Melzack and Wall in 1965 rejuvenated the field of pain study and led to further investigation into the phenomena of spinal sensitization and central nervous system plasticity, which are the potential pathophysiologic correlates of chronic pain. The processing of pain takes place in an integrated matrix throughout the neuroaxis and occurs on at least three levels-at peripheral, spinal, and supraspinal sites. Basic strategies of pain control monopolize on this concept of integration by attenuation or blockade of pain through intervention at the periphery, by activation of inhibitory processes that gate pain at the spinal cord and brain, and by interference with the perception of pain. This article discusses each level of pain modulation and reviews the mechanisms of action of opioids and potential new analgesics. A brief description of animal models frames a discussion about recent advances regarding the role of glial cells and central nervous system neuroimmune activation and innate immunity in the etiology of chronic pain states. Future investigation into the discovery and development of novel, nonopioid drug therapy may provide needed options for the millions of patients who suffer from chronic pain syndromes, including syndromes in which the pain originates from peripheral nerve, nerve root, spinal cord, bone, muscle, and disc. PMID:16595445

DeLeo, Joyce A

2006-04-01

394

Near-Universal Basic Income  

Microsoft Academic Search

Under what I call â€Near-Universal Basic Income,†or NUBI, everyone receives a high level of basic income, except for the rich. NUBI is therefore only near-universal and it requires means-testing. It is an economic hybrid: a cross between Universal Basic Income (UBI) and conservative social relief. My thesis is that if standard considerations that are often advanced to support UBI

Nir Eyal

2010-01-01

395

Regulation of cell divisions and differentiation by MALE STERILITY32 is required for anther development in maize.  

PubMed

Male fertility in flowering plants relies on proper division and differentiation of cells in the anther, a process that gives rise to four somatic layers surrounding central germinal cells. The maize gene male sterility32 (ms32) encodes a basic helix-loop-helix (bHLH) transcription factor, which functions as an important regulator of both division and differentiation during anther development. After the four somatic cell layers are generated properly through successive periclinal divisions, in the ms32 mutant, tapetal precursor cells fail to differentiate, and, instead, undergo additional periclinal divisions to form extra layers of cells. These cells become vacuolated and expand, and lead to failure in pollen mother cell development. ms32 expression is specific to the pre-meiotic anthers and is distributed initially broadly in the four lobes, but as the anther develops, its expression becomes restricted to the innermost somatic layer, the tapetum. The ms32-ref mac1-1 double mutant is unable to form tapetal precursors and also exhibits excessive somatic proliferation leading to numerous, disorganized cell layers, suggesting a synergistic interaction between ms32 and mac1. Altogether, our results show that MS32 is a major regulator in maize anther development that promotes tapetum differentiation and inhibits periclinal division once a tapetal cell is specified. PMID:24033746

Moon, Jihyun; Skibbe, David; Timofejeva, Ljudmilla; Wang, Chung-Ju Rachel; Kelliher, Timothy; Kremling, Karl; Walbot, Virginia; Cande, William Zacheus

2013-10-05

396

Twist1 Controls a Cell-Specification Switch Governing Cell Fate Decisions within the Cardiac Neural Crest  

PubMed Central

Neural crest cells are multipotent progenitor cells that can generate both ectodermal cell types, such as neurons, and mesodermal cell types, such as smooth muscle. The mechanisms controlling this cell fate choice are not known. The basic Helix-loop-Helix (bHLH) transcription factor Twist1 is expressed throughout the migratory and post-migratory cardiac neural crest. Twist1 ablation or mutation of the Twist-box causes differentiation of ectopic neuronal cells, which molecularly resemble sympathetic ganglia, in the cardiac outflow tract. Twist1 interacts with the pro-neural factor Sox10 via its Twist-box domain and binds to the Phox2b promoter to repress transcriptional activity. Mesodermal cardiac neural crest trans-differentiation into ectodermal sympathetic ganglia-like neurons is dependent upon Phox2b function. Ectopic Twist1 expression in neural crest precursors disrupts sympathetic neurogenesis. These data demonstrate that Twist1 functions in post-migratory neural crest cells to repress pro-neural factors and thereby regulate cell fate determination between ectodermal and mesodermal lineages.

Vincentz, Joshua W.; Firulli, Beth A.; Lin, Andrea; Spicer, Douglas B.; Howard, Marthe J.; Firulli, Anthony B.

2013-01-01

397

Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF  

PubMed Central

Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and an important oncogene in melanoma. MITF heterodimeric assembly with related basic helix–loop–helix leucine zipper transcription factors is highly restricted, and its binding profile to cognate DNA sequences is distinct. Here, we determined the crystal structure of MITF in its apo conformation and in the presence of two related DNA response elements, the E-box and M-box. In addition, we investigated mouse and human Mitf mutations to dissect the functional significance of structural features. Owing to an unusual three-residue shift in the leucine zipper register, the MITF homodimer shows a marked kink in one of the two zipper helices to allow an out-of-register assembly. Removal of this insertion relieves restricted heterodimerization by MITF and permits assembly with the transcription factor MAX. Binding of MITF to the M-box motif is mediated by an unusual nonpolar interaction by Ile212, a residue that is mutated in mice and humans with Waardenburg syndrome. As several related transcription factors have low affinity for the M-box sequence, our analysis unravels how these proteins discriminate between similar target sequences. Our data provide a rational basis for targeting MITF in the treatment of important hereditary diseases and cancer.

Pogenberg, Vivian; Ogmundsdottir, Margret H; Bergsteinsdottir, Kristin; Schepsky, Alexander; Phung, Bengt; Deineko, Viktor; Milewski, Morlin; Steingrimsson, Eirikur; Wilmanns, Matthias

2012-01-01

398

Omega-3 Polyunsaturated Fatty Acids Enhance Neuronal Differentiation in Cultured Rat Neural Stem Cells  

PubMed Central

Polyunsaturated fatty acids (PUFAs) can induce neurogenesis and recovery from brain diseases. However, the exact mechanisms of the beneficial effects of PUFAs have not been conclusively described. We recently reported that docosahexaenoic acid (DHA) induced neuronal differentiation by decreasing Hes1 expression and increasing p27kip1 expression, which causes cell cycle arrest in neural stem cells (NSCs). In the present study, we examined the effect of eicosapentaenoic acid (EPA) and arachidonic acid (AA) on differentiation, expression of basic helix-loop-helix transcription factors (Hes1, Hes6, and NeuroD), and the cell cycle of cultured NSCs. EPA also increased mRNA levels of Hes1, an inhibitor of neuronal differentiation, Hes6, an inhibitor of Hes1, NeuroD, and Map2 mRNA and Tuj-1-positive cells (a neuronal marker), indicating that EPA induced neuronal differentiation. EPA increased the mRNA levels of p21cip1 and p27kip1, a cyclin-dependent kinase inhibitor, which indicated that EPA induced cell cycle arrest. Treatment with AA decreased Hes1 mRNA but did not affect NeuroD and Map2 mRNA levels. Furthermore, AA did not affect the number of Tuj-1-positive cells or cell cycle progression. These results indicated that EPA could be involved in neuronal differentiation by mechanisms alternative to those of DHA, whereas AA did not affect neuronal differentiation in NSCs.

Katakura, Masanori; Hashimoto, Michio; Okui, Toshiyuki; Shahdat, Hossain Md; Matsuzaki, Kentaro; Shido, Osamu

2013-01-01

399

Conditional deletion of neurogenin-3 using Nkx2.1iCre results in a mouse model for the central control of feeding, activity and obesity.  

PubMed

The ventral hypothalamus acts to integrate visceral and systemic information to control energy balance. The basic helix-loop-helix transcription factor neurogenin-3 (Ngn3) is required for pancreatic ?-cell development and has been implicated in neuronal development in the hypothalamus. Here, we demonstrate that early embryonic hypothalamic inactivation of Ngn3 (also known as Neurog3) in mice results in rapid post-weaning obesity that is associated with hyperphagia and reduced energy expenditure. This obesity is caused by loss of expression of Pomc in Pomc- and Cart-expressing (Pomc/Cart) neurons in the arcuate nucleus, indicating an incomplete specification of anorexigenic first order neurons. Furthermore, following the onset of obesity, both the arcuate and ventromedial hypothalamic nuclei become insensitive to peripheral leptin treatment. This conditional mouse mutant therefore represents a novel model system for obesity that is associated with hyperphagia and underactivity, and sheds new light upon the roles of Ngn3 in the specification of hypothalamic neurons controlling energy balance. PMID:23649822

Anthwal, Neal; Pelling, Michelle; Claxton, Suzanne; Mellitzer, Georg; Collin, Caitlin; Kessaris, Nicoletta; Richardson, William D; Gradwohl, Gérard; Ang, Siew-Lan

2013-05-02

400

Complex regulation controls Neurogenin3 proteolysis.  

PubMed

The ubiquitin proteasome system (UPS) is known to be responsible for the rapid turnover of many transcription factors, where half-life is held to be critical for regulation of transcriptional activity. However, the stability of key transcriptional regulators of development is often very poorly characterised. Neurogenin 3 (Ngn3) is a basic helix-loop-helix transcription factor that plays a central role in specification and differentiation of endocrine cells of the pancreas and gut, as well as spermatogonia and regions of the brain. Here we demonstrate that Ngn3 protein stability is regulated by the ubiquitin proteasome system and that Ngn3 can be ubiquitylated on lysines, the N-terminus and, highly unusually, on non-canonical residues including cysteines and serines/threonines. Rapid turnover of Ngn3 is regulated both by binding to its heterodimeric partner E protein and by the presence of cdk inhibitors. We show that protein half-life does appear to regulate the activity of Ngn3 in vivo, but, unlike the related transcription factor c-myc, ubiquitylation on canonical sites is not a requirement for transcriptional activity of Ngn3. Hence, we characterise an important new level of Ngn3 post-translational control, which may regulate its transcriptional activity. PMID:23259061

Roark, Ryan; Itzhaki, Laura; Philpott, Anna

2012-10-16

401

Neurog3 gene dosage regulates allocation of endocrine and exocrine cell fates in the developing mouse pancreas  

PubMed Central

The basic helix-loop-helix transcription factor Neurog3 (Neurogenin3 or Ngn3) actively drives endodermal progenitor cells towards endocrine islet cell differentiation during embryogenesis. Here, we manipulate Neurog3 expression levels in endocrine progenitor cells without altering its expression pattern using heterozygosity and a hypomorph. Lowered Neurog3 gene dosage in the developing pancreatic epithelium reduces the overall production of endocrine islet cells without significantly affecting the proportions of various islet cell types that do form. A reduced Neurog3 production level in the endocrine-directed pancreatic progenitor population activates the expression of Neurog3 in an increased number of epithelial progenitors. Yet a significant number of these Neurog3+ cells detected in heterozygous and hypomorphic pancreata, possibly those that express low levels of Neurog3, move on to adopt pancreatic ductal or acinar fates. These data directly demonstrate that achieving high levels of Neurog3 expression is a critical step for endocrine commitment from multipotent pancreatic progenitors. These findings also suggest that a high level of Neurog3 expression could mediate lateral inhibition or other unknown feedback mechanisms to regulate the number of cells that initiate Neurog3 transcription and protein production. The control of Neurog3+ cell number and the Neurog3 threshold-dependent endocrine differentiation mechanism combine to select a specific proportion of pancreatic progenitor cells to adopt the islet cell fate.

Wang, Sui; Yan, Jingbo; Anderson, Daniel A.; Xu, Yanwen; Kanal, Maneesh C.; Cao, Zheng; Wright, Christopher V. E.; Gu, Guoqiang

2010-01-01

402

Direct downstream targets of proneural activators in the imaginal disc include genes involved in lateral inhibitory signaling.  

PubMed

In Drosophila imaginal discs, the spatially restricted activities of the achaete (ac) and scute (sc) proteins, which are transcriptional activators of the basic-helix-loop-helix class, define proneural clusters (PNCs) of potential sensory organ precursor (SOP) cells. Here, we report the identification of several genes that are direct downstream targets of ac-sc activation, as judged by the following criteria. The genes are expressed in the PNCs of the wing imaginal disc in an ac-sc-dependent manner; the proximal promoter regions of all of these genes contain one or two high-affinity ac-sc binding sites, which define the novel consensus GCAGGTG(T/G)NNNYY; where tested, these binding sites are required in vivo for PNC expression of promoter-reporter fusion genes. Interestingly, these ac-sc target genes, including Bearded, Enhancer of split m7, Enhancer of split m8, and scabrous, are all known or believed to function in the selection of a single SOP from each PNC, a process mediated by inhibitory cell-cell interactions. Thus, one of the earliest steps in adult peripheral neurogenesis is the direct activation by proneural proteins of genes involved in restricting the expression of the SOP cell fate. PMID:7958878

Singson, A; Leviten, M W; Bang, A G; Hua, X H; Posakony, J W

1994-09-01

403

New insights into the Orange domain of E(spl)-M8, and the roles of the C-terminal domain in autoinhibition and Groucho recruitment  

PubMed Central

CK2 is a Ser/Thr protein kinase that regulates the activity of the Drosophila basic-helix-loop-helix (bHLH) repressor M8 encoded by the Enhancer of split Complex (E(spl)C) during neurogenesis. Specifically, phosphorylation appears to elicit a conformational change in an autoinhibited state of M8 to one that is permissive for repression. We describe biochemical and molecular modeling studies that provide new insights into repression by M8. Our studies implicate the phosphorylation domain in autoinhibition, and indicate that binding of the co-repressor Groucho (Gro) is context-dependent. Molecular modeling indicates that the Orange domain, proposed to be a specificity-determinant, may instead play a structural role, and that a conformational rearrangement of this domain may be necessary for repression. This model also provides a structural mechanism for the behavior of mutant alleles of the m8 gene. The insights gained from these studies should be applicable to the conserved metazoan bHLH repressors of the Hairy and Enhancer of Split (HES) family that are related to Drosophila M8.

Eastwood, Karen; Yin, Chong; Bandyopadhyay, Mohna; Bidwai, Ashok

2011-01-01

404

TWIST inactivation reduces CBFA1/RUNX2 expression and DNA binding to the osteocalcin promoter in osteoblasts.  

PubMed

The Saethre-Chotzen (SC) syndrome is characterized by increased osteogenesis and premature fusion of cranial sutures, resulting from mutations in TWIST, a basic helix-loop-helix transcription factor. The molecular target genes for Twist in osteoblasts are however unknown. We report here that TWIST haploinsufficiency in mutant osteoblasts reduces mRNA and protein levels for CBFA1/RUNX2, a specific osteoblast transcription factor, during both osteoblast cell growth and in vitro osteogenesis. Moreover, this is associated with altered expression of major osteoblast-specific genes. Electrophoretic mobility shift assay (EMSA) showed reduced-binding ability of Cbfa1 to its target OSE2 element in the osteocalcin promoter in mutant osteoblasts. By contrast, TWIST inactivation does not hamper Cbfa1 binding on a similar upstream element present in the alpha1(I) collagen promoter in mutant osteoblasts. This provides the first evidence that TWIST inactivation alters CBFA1/RUNX2 expression and Cbfa1 binding ability to the osteocalcin promoter, indicating that CBFA1/RUNX2 is a target gene for TWIST in human osteoblasts. PMID:12270142

Yousfi, Malika; Lasmoles, Françoise; Marie, Pierre J

2002-09-27

405

Identification of Novel MyoD Gene Targets in Proliferating Myogenic Stem Cells  

PubMed Central

A major control point for skeletal myogenesis revolves around the muscle basic helix-loop-helix gene family that includes MyoD, Myf-5, myogenin, and MRF4. Myogenin and MRF4 are thought to be essential to terminal differentiation events, whereas MyoD and Myf-5 are critical to establishing the myogenic cell lineage and producing committed, undifferentiated myogenic stem cells (myoblasts). Although mouse genetic studies have revealed the importance of MyoD and Myf-5 for myoblast development, the genetic targets of MyoD and Myf-5 activity in undifferentiated myoblasts remain unknown. In this study, we investigated the function of MyoD as a transcriptional activator in undifferentiated myoblasts. By using conditional expression of MyoD, in conjunction with suppression subtractive hybridizations, we show that the Id3 and NP1 (neuronal pentraxin 1) genes become transcriptionally active following MyoD induction in undifferentiated myoblasts. Activation of Id3 and NP1 represents a stable, heritable event that does not rely on continued MyoD activity and is not subject to negative regulation by an activated H-Ras G12V protein. These results are the first to demonstrate that MyoD functions as a transcriptional activator in myogenic stem cells and that this key myogenic regulatory factor exhibits different gene target specificities, depending upon the cellular environment.

Wyzykowski, Jeffrey C.; Winata, Therry I.; Mitin, Natalia; Taparowsky, Elizabeth J.; Konieczny, Stephen F.

2002-01-01

406

Interaction between the bHLH Transcription Factor FIT and ETHYLENE INSENSITIVE3/ETHYLENE INSENSITIVE3-LIKE1 Reveals Molecular Linkage between the Regulation of Iron Acquisition and Ethylene Signaling in Arabidopsis[C][W  

PubMed Central

Understanding the regulation of key genes involved in plant iron acquisition is of crucial importance for breeding of micronutrient-enriched crops. The basic helix-loop-helix protein FER-LIKE FE DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT), a central regulator of Fe acquisition in roots, is regulated by environmental cues and internal requirements for iron at the transcriptional and posttranscriptional levels. The plant stress hormone ethylene promotes iron acquisition, but the molecular basis for this remained unknown. Here, we demonstrate a direct molecular link between ethylene signaling and FIT. We identified ETHYLENE INSENSITIVE3 (EIN3) and ETHYLENE INSENSITIVE3-LIKE1 (EIL1) in a screen for direct FIT interaction partners and validated their physical interaction in planta. We demonstrate that the ein3 eil1 transcriptome was affected to a greater extent upon iron deficiency than normal iron compared with the wild type. Ethylene signaling by way of EIN3/EIL1 was required for full-level FIT accumulation. FIT levels were reduced upon application of aminoethoxyvinylglycine and in the ein3 eil1 background. MG132 could restore FIT levels. We propose that upon ethylene signaling, FIT is less susceptible to proteasomal degradation, presumably due to a physical interaction between FIT and EIN3/EIL1. Increased FIT abundance then leads to the high level of expression of genes required for Fe acquisition. This way, ethylene is one of the signals that triggers Fe deficiency responses at the transcriptional and posttranscriptional levels.

Lingam, Sivasenkar; Mohrbacher, Julia; Brumbarova, Tzvetina; Potuschak, Thomas; Fink-Straube, Claudia; Blondet, Eddy; Genschik, Pascal; Bauer, Petra

2011-01-01

407

Disruption of CK2? in Embryonic Neural Stem Cells Compromises Proliferation and Oligodendrogenesis in the Mouse Telencephalon? †  

PubMed Central

Genetic programs that govern neural stem/progenitor cell (NSC) proliferation and differentiation are dependent on extracellular cues and a network of transcription factors, which can be regulated posttranslationally by phosphorylation. However, little is known about the kinase-dependent pathways regulating NSC maintenance and oligodendrocyte development. We used a conditional knockout approach to target the murine regulatory subunit (beta) of protein kinase casein kinase 2 (CK2?) in embryonic neural progenitors. Loss of CK2? leads to defects in proliferation and differentiation of embryonic NSCs. We establish CK2? as a key positive regulator for the development of oligodendrocyte precursor cells (OPCs), both in vivo and in vitro. We show that CK2? directly interacts with the basic helix-loop-helix (bHLH) transcription factor Olig2, a critical modulator of OPC development, and activates the CK2-dependent phosphorylation of its serine-threonine-rich (STR) domain. Finally, we reveal that the CK2-targeted STR domain is required for the oligodendroglial function of Olig2. These findings suggest that CK2 may control oligodendrogenesis, in part, by regulating the activity of the lineage-specific transcription factor Olig2. Thus, CK2? appears to play an essential and uncompensated role in central nervous system development.

Huillard, Emmanuelle; Ziercher, Lea; Blond, Olivier; Wong, Michael; Deloulme, Jean-Christophe; Souchelnytskyi, Serhiy; Baudier, Jacques; Cochet, Claude; Buchou, Thierry

2010-01-01

408

Mad1 function is regulated through elements within the carboxy terminus.  

PubMed

Myc and Mad are basic helix-loop-helix leucine zipper (bHLH-LZ) proteins that heterodimerize with Max to bind DNA and thereby influence the transcription of Myc-responsive genes. Myc-Max dimers transactivate whereas Mad-Max-mSin3 complexes repress Myc-mediated transcriptional activation. We have previously shown that the N-terminal mSin3 binding domain and the centrally located bHLH-LZ are required for Mad1 to function during a molecular switch from proliferation to differentiation. Here we demonstrate that the carboxy terminus (CT) of Mad1 contains previously unidentified motifs necessary for the regulation of Mad1 function. We show that removal of the last 18 amino acids of Mad1 (region V) abolishes the growth-inhibitory function of the protein and the ability to reverse a Myc-imposed differentiation block. Moreover, deletion of region V results in a protein that binds DNA weakly and no longer represses Myc-dependent transcriptional activation. In contrast, deletion of the preceding 24 amino acids (region IV) together with region V restores DNA binding and transcriptional repression, suggesting a functional interplay between these two regions. Furthermore, phosphorylation within region IV appears to mediate this interplay. These findings indicate that novel regulatory elements are present in the Mad1 CT. PMID:10825189

Barrera-Hernandez, G; Cultraro, C M; Pianetti, S; Segal, S

2000-06-01

409

Ah receptor and NF-kappaB interplay on the stage of epigenome.  

PubMed

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that belongs to the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family. Its ligands include many natural and synthetic compounds, some of which, such as polyhalogenated aromatic hydrocarbons and polycyclic aromatic hydrocarbons, are important environmental contaminants. NF-kappaB is a pleiotropic factor that regulates many physiological and pathophysiological processes including the immune and inflammatory responses. In the past decade, accumulating evidence suggests close interactions between AhR and NF-kappaB pathways, and these interactions are potentially important mechanisms for many pathological processes such as the chemical-induced immune dysfunctions, carcinogenesis and alteration of xenobiotic metabolism and disposition. AhR-NF-kappaB interaction has become a mechanistic linchpin linking certain pathological responses induced by environmental insults. Furthermore, the AhR-NF-kappaB interaction provides basis for therapeutic applications of certain AhR ligands to treat human diseases. The effects of AhR-NF-kappaB on the epigenome are an important area that is not well understood. In this review, I highlight current research regarding the AhR-NF-kappaB(RelA) interactions with emphasis on the epigenetic impacts of these interactions on chromatin modifications and transcription elongation control. PMID:19014911

Tian, Yanan

2008-10-28

410

Tcf15 Primes Pluripotent Cells for Differentiation  

PubMed Central

Summary The events that prime pluripotent cells for differentiation are not well understood. Inhibitor of DNA binding/differentiation (Id) proteins, which are inhibitors of basic helix-loop-helix (bHLH) transcription factor activity, contribute to pluripotency by blocking sequential transitions toward differentiation. Using yeast-two-hybrid screens, we have identified Id-regulated transcription factors that are expressed in embryonic stem cells (ESCs). One of these, Tcf15, is also expressed in the embryonic day 4.5 embryo and is specifically associated with a novel subpopulation of primed ESCs. An Id-resistant form of Tcf15 rapidly downregulates Nanog and accelerates somatic lineage commitment. We propose that because Tcf15 can be held in an inactive state through Id activity, it may prime pluripotent cells for entry to somatic lineages upon downregulation of Id. We also find that Tcf15 expression is dependent on fibroblast growth factor (FGF) signaling, providing an explanation for how FGF can prime for differentiation without driving cells out of the pluripotent state.

Davies, Owen R.; Lin, Chia-Yi; Radzisheuskaya, Aliaksandra; Zhou, Xinzhi; Taube, Jessica; Blin, Guillaume; Waterhouse, Anna; Smith, Andrew J.H.; Lowell, Sally

2013-01-01

411

Interallelic complementation at the mouse Mitf locus.  

PubMed

Mutations at the mouse microphthalmia locus (Mitf) affect the development of different cell types, including melanocytes, retinal pigment epithelial cells of the eye, and osteoclasts. The MITF protein is a member of the MYC supergene family of basic-helix-loop-helix-leucine-zipper (bHLHZip) transcription factors and is known to regulate the expression of cell-specific target genes by binding DNA as homodimer or as heterodimer with related proteins. The many mutations isolated at the locus have different effects on the phenotype and can be arranged in an allelic series in which the phenotypes range from near normal to white microphthalmic animals with osteopetrosis. Previous investigations have shown that certain combinations of Mitf alleles complement each other, resulting in a phenotype more normal than that of each homozygote alone. Here we analyze this interallelic complementation in detail and show that it is limited to one particular allele, Mitf(Mi-white) (Mitf(Mi-wh)), a mutation affecting the DNA-binding domain. Both loss- and gain-of-function mutations are complemented, as are other Mitf mutations affecting the DNA-binding domain. Furthermore, this behavior is not restricted to particular cell types: Both eye development and coat color phenotypes are complemented. Our analysis suggests that Mitf(Mi-wh)-associated interallelic complementation is due to the unique biochemical nature of this mutation. PMID:12586714

Steingrímsson, Eiríkur; Arnheiter, Heinz; Hallsson, Jón Hallsteinn; Lamoreux, M Lynn; Copeland, Neal G; Jenkins, Nancy A

2003-01-01

412

Ligand-activated Ahr signaling leads to disruption of nephrogenesis and altered Wilms' tumor suppressor mRNA splicing.  

PubMed

The aryl hydrocarbon receptor (Ahr), a member of the large basic helix-loop-helix (bHLH) and PAS homology domain superfamily, is a highly conserved transcriptional regulator involved in mammalian development. In the present study, a murine metanephros organ culture system was employed to evaluate the role of the Ahr signaling in nephrogenesis in vitro. Ahr and Wilms' tumor suppressor (wt1) mRNAs were detected by in situ hybridization and RT-PCR during the course of renal development. Treatment with 3 microM BaP, a hydrocarbon ligand of Ahr, inhibited glomerulogenesis and branching morphogenesis of metanephric kidneys. Deficits in the epithelialization of mesenchymal cells were evidenced by inhibition of the formation of podocyte foot processes and glomerular basement membranes. Hydrocarbon treatment markedly induced -KTS wt1 splice variants, although total wt1 mRNA levels remained unchanged. A significant decrease in total WT1 protein was observed by both immunocytochemistry and Western analysis in cultures challenged with BaP compared to controls. Comparison of metanephric cultures from Ahr+/+ and Ahr-/- mice showed that Ahr is involved in kidney development, and required for BaP-induced deficits in nephrogenesis. These results indicate that ligand activation of Ahr signaling disrupts nephrogenesis in vitro, and that this response involves modulation of wt1 alternative splicing and post-transcriptional control. PMID:12687018

Falahatpisheh, M Hadi; Ramos, Kenneth S

2003-04-10

413

Pod1 is required in stromal cells for glomerulogenesis.  

PubMed

Pod1 (capsulin/epicardin/Tcf21) is a basic-helix-loop-helix transcription factor that is highly expressed in the mesenchyme of developing organs that include the kidney, lung, gut, and heart. Null Pod1 mice are born but die shortly after birth due to a lack of alveoli in the lungs and cardiac defects. In addition, the kidneys are hypoplastic and demonstrate disrupted branching morphogenesis of the ureteric bud epithelium, a marked reduction in the number of nephrons, a delay in glomerulogenesis, and blood vessel abnormalities. To further dissect the cellular function of Pod1 during kidney development, chimeric mice were generated through aggregations of null Pod1 embryonic stem cells and murine embryos ubiquitously expressing enhanced green fluorescent protein (GFP). Histologic, immunohistochemical, and in situ hybridization analysis of the resulting chimeric offspring demonstrated both cell autonomous and non-cell autonomous roles for Pod1 in the differentiation of specific renal cell lineages that include peritubular interstitial cells and pericytes. Most strikingly, the glomerulogenesis defect was rescued by the presence of wild-type stromal cells, suggesting a non-cell autonomous role for Pod1 in this cell population. PMID:12619136

Cui, Shiying; Schwartz, Lois; Quaggin, Susan E

2003-03-01

414

The bHLH/Per-Arnt-Sim transcription factor SIM2 regulates muscle transcript myomesin2 via a novel, non-canonical E-box sequence  

PubMed Central

Despite a growing number of descriptive studies that show Single-minded 2 (Sim2) is not only essential for murine survival, but also upregulated in colon, prostate and pancreatic tumours, there is a lack of direct target genes identified for this basic helix–loop–helix/PAS transcription factor. We have performed a set of microarray experiments aimed at identifying genes that are differentially regulated by SIM2, and successfully verified that the Myomesin2 (Myom2) gene is SIM2-responsive. Although SIM2 has been reported to be a transcription repressor, we find that SIM2 induces transcription of Myom2 and activates the Myom2 promoter sequence when co-expressed with the heterodimeric partner protein, ARNT1, in human embryonic kidney cells. Truncation and mutation of the Myom2 promoter sequence, combined with chromatin immunoprecipitation studies in cells, has lead to the delineation of a non-canonical E-box sequence 5?-AACGTG-3? that is bound by SIM2/ARNT1 heterodimers. Interestingly, in immortalized human myoblasts knock down of Sim2 results in increased levels of Myom2 RNA, suggesting that SIM2 is acting as a repressor in these cells and so its activity is likely to be highly context dependent. This is the first report of a direct SIM2/ARNT1 target gene with accompanying analysis of a functional response element.

Woods, Susan; Farrall, Alexandra; Procko, Carl; Whitelaw, Murray L.

2008-01-01

415

Expression of the Gs protein alpha-subunit disrupts the normal program of differentiation in cultured murine myogenic cells.  

PubMed Central

The manner in which growth factors acting at the cell surface regulate activity of myogenic basic-helix-loop-helix proteins in the nucleus and thus control the fate of committed skeletal myoblasts remains poorly understood. In this study, we report that immunoreactive Gs protein alpha-subunits (Gs alpha) localize to nuclei of proliferating C2C12 myoblasts but not to nuclei of differentiated postmitotic C2C12 myotubes. To explore the biological significance of this observation, we placed a cDNA encoding Gs alpha in an expression vector under the control of a steroid-inducible promoter and isolated colonies of stably transfected C2C12 myoblasts. Dexamethasone-induced expression of activated Gs alpha markedly delayed differentiation in comparison with uninduced stably transfected cells, which differentiated normally in mitogen-depleted media. Northern blot analysis showed that impaired differentiation was associated with delayed up-regulation of MyoD and myogenin and delayed down-regulation of Id, a dominant negative inhibitor of differentiation. Similar impairment of differentiation could not be reproduced in wild-type C2C12 cells by increasing intracellular cAMP either with forskolin or treatment with a cell-permeable cAMP analog. However, treatment of myoblasts with cholera toxin markedly inhibited myogenic differentiation. Taken together, these findings suggest a novel role for Gs alpha in modulating myogenic differentiation.

Tsai, C C; Saffitz, J E; Billadello, J J

1997-01-01

416

Silencing of the inhibitor of DNA binding protein 4 (ID4) contributes to the pathogenesis of mouse and human CLL  

PubMed Central

Inhibitor of DNA binding protein 4 (ID4) is a member of the dominant-negative basic helix-loop-helix transcription factor family that lacks DNA binding activity and has tumor suppressor function. ID4 promoter methylation has been reported in acute myeloid leukemia and chronic lymphocytic leukemia (CLL), although the expression, function, and clinical relevance of this gene have not been characterized in either disease. We demonstrate that the promoter of ID4 is consistently methylated to various degrees in CLL cells, and increased promoter methylation in a univariable analysis correlates with shortened patient survival. However, ID4 mRNA and protein expression is uniformly silenced in CLL cells irrespective of the degree of promoter methylation. The crossing of ID4+/? mice with E?-TCL1 mice triggers a more aggressive murine CLL as measured by lymphocyte count and inferior survival. Hemizygous loss of ID4 in nontransformed TCL1-positive B cells enhances cell proliferation triggered by CpG oligonucleotides and decreases sensitivity to dexamethasone-mediated apoptosis. Collectively, this study confirms the importance of the silencing of ID4 in murine and human CLL pathogenesis.

Chen, Shih-Shih; Claus, Rainer; Lucas, David M.; Yu, Lianbo; Qian, Jiang; Ruppert, Amy S.; West, Derek A.; Williams, Katie E.; Johnson, Amy J.; Sablitzky, Fred

2011-01-01

417

Stomatal development in Arabidopsis and grasses: differences and commonalities.  

PubMed

Stomata, found on the epidermis of all terrestrial plants, consist of two specialized cells called guard cells, which surround a tiny pore. Major advances have been made in our understanding of the genetic control of stomatal development in Arabidopsis and grasses. In Arabidopsis, three basic-helix-loop-helix (bHLH) genes control the successive steps that lead to stomatal formation. SPEECHLESS (SPCH) drives the cell division that initiates the stomatal cell lineage, MUTE induces the formation of the immediate stomatal precursor cell, and FAMA causes the stomatal precursor cell to divide into the two guard cells. Recent results demonstrate that these genes share functions with their grass homologs, and that MUTE is expressed later in development than its grass counterparts. Other differences in stomatal development between these two plant groups are exemplified by the PANGLOSS1 (PAN1) gene of maize. PAN1, which encodes a leucine-rich repeat receptor-like kinase with an inactive kinase domain, promotes polarization of the subsidiary mother cell and orients its cell division plane. Because such events do not exist in Arabidopsis, it is likely that the PAN1-like genes of Arabidopsis and PAN1 are paralogs. Together, these results indicate that distinctions in the regulation of gene expression and protein function are both responsible for the divergence of stomatal development between Arabidopsis and grasses. PMID:21425077

Serna, Laura

2011-01-01

418

Out of the mouths of plants: the molecular basis of the evolution and diversity of stomatal development.  

PubMed

Stomata are microscopic valves on the plant epidermis that played a critical role in the evolution of land plants. Studies in the model dicot Arabidopsis thaliana have identified key transcription factors and signaling pathways controlling stomatal patterning and differentiation. Three paralogous Arabidopsis basic helix-loop-helix proteins, SPEECHLESS (SPCH), MUTE, and FAMA, mediate sequential steps of cell-state transitions together with their heterodimeric partners SCREAM (SCRM) and SCRM2. Cell-cell signaling components, including putative ligands, putative receptors, and mitogen-activated protein kinase cascades, orient asymmetric cell divisions and prevent overproduction and clustering of stomata. The recent availability of genome sequence and reverse genetics tools for model monocots and basal land plants allows for the examination of the conservation of genes important in stomatal patterning and differentiation. Studies in grasses have revealed that divergence of SPCH-MUTE-FAMA predates the evolutionary split of monocots and dicots and that these proteins show conserved and novel roles in stomatal differentiation. By contrast, specific asymmetric cell divisions in Arabidopsis and grasses require unique molecular components. Molecular phylogenetic analysis implies potential conservation of signaling pathways and prototypical functions of the transcription factors specifying stomatal differentiation. PMID:20179138

Peterson, Kylee M; Rychel, Amanda L; Torii, Keiko U

2010-02-23

419

PHYTOCHROME INTERACTING FACTOR3 Associates with the Histone Deacetylase HDA15 in Repression of Chlorophyll Biosynthesis and Photosynthesis in Etiolated Arabidopsis Seedlings[W][OA  

PubMed Central

PHYTOCHROME INTERACTING FACTOR3 (PIF3) is a key basic helix-loop-helix transcription factor of Arabidopsis thaliana that negatively regulates light responses, repressing chlorophyll biosynthesis, photosynthesis, and photomorphogenesis in the dark. However, the mechanism for the PIF3-mediated transcription regulation remains largely unknown. In this study, we found that the REDUCED POTASSIUM DEPENDENCY3/HISTONE DEACETYLASE1-type histone deacetylase HDA15 directly interacted with PIF3 in vivo and in vitro. Genome-wide transcriptome analysis revealed that HDA15 acts mainly as a transcriptional repressor and negatively regulates chlorophyll biosynthesis and photosynthesis gene expression in etiolated seedlings. HDA15 and PIF3 cotarget to the genes involved in chlorophyll biosynthesis and photosynthesis in the dark and repress gene expression by decreasing the acetylation levels and RNA Polymerase II–associated transcription. The binding of HDA15 to the target genes depends on the presence of PIF3. In addition, PIF3 and HDA15 are dissociated from the target genes upon exposure to red light. Taken together, our results indicate that PIF3 associates with HDA15 to repress chlorophyll biosynthetic and photosynthetic genes in etiolated seedlings.

Liu, Xuncheng; Chen, Chia-Yang; Wang, Ko-Ching; Luo, Ming; Tai, Ready; Yuan, Lianyu; Zhao, Minglei; Yang, Songguang; Tian, Gang; Cui, Yuhai; Hsieh, Hsu-Liang; Wu, Keqiang

2013-01-01

420

A noncoding RNA regulates the neurogenin1 gene locus during mouse neocortical development.  

PubMed

The proneural basic helix-loop-helix (bHLH) transcription factor neurogenin1 (Neurog1) plays a pivotal role in neuronal differentiation during mammalian development. The spatiotemporal control of the Neurog1 gene expression is mediated by several specific enhancer elements, although how these elements regulate the Neurog1 locus has remained largely unclear. Recently it has been shown that a large number of enhancer elements are transcribed, but the regulation and function of the resulting transcripts have been investigated for only several such elements. We now show that an enhancer element located 5.8-7.0 kb upstream of the mouse Neurog1 locus is transcribed. The production of this transcript, designated utNgn1, is highly correlated with that of Neurog1 mRNA during neuronal differentiation. Moreover, knockdown of utNgn1 by a corresponding short interfering RNA inhibits the production of Neurog1 mRNA in response to induction of neuronal differentiation. We also found that production of utNgn1 is suppressed by polycomb group (PcG) proteins, which inhibit the expression of Neurog1. Our results thus suggest that a noncoding RNA transcribed from an enhancer element positively regulates transcription at the Neurog1 locus. PMID:23027973

Onoguchi, Masahiro; Hirabayashi, Yusuke; Koseki, Haruhiko; Gotoh, Yukiko

2012-10-01

421

G9a mediates Sharp-1-dependent inhibition of skeletal muscle differentiation  

PubMed Central

Sharp-1, a basic helix-loop-helix transcription factor, is a potent repressor of skeletal muscle differentiation and is dysregulated in muscle pathologies. However, the mechanisms by which it inhibits myogenesis are not fully understood. Here we show that G9a, a lysine methyltransferase, is involved in Sharp-1–mediated inhibition of muscle differentiation. We demonstrate that G9a directly interacts with Sharp-1 and enhances its ability to transcriptionally repress the myogenin promoter. Concomitant with a differentiation block, G9a-dependent histone H3 lysine 9 dimethylation (H3K9me2) and MyoD methylation are apparent upon Sharp-1 overexpression in muscle cells. RNA interference–mediated reduction of G9a or pharmacological inhibition of its activity erases these repressive marks and rescues the differentiation defect imposed by Sharp-1. Our findings provide new insights into Sharp-1–dependent regulation of myogenesis and identify epigenetic mechanisms that could be targeted in myopathies characterized by elevated Sharp-1 levels.

Ling, Belinda Mei Tze; Gopinadhan, Suma; Kok, Wai Kay; Shankar, Shilpa Rani; Gopal, Pooja; Bharathy, Narendra; Wang, Yaju; Taneja, Reshma

2012-01-01

422

Origins of enhancer sequences of recombinant murine leukemia viruses from spontaneous B- and T-cell lymphomas of CWD mice.  

PubMed Central

Recombinant murine leukemia viruses from the highly leukemic mouse strains AKR, HRS, and C58 usually acquire pathogenic U3 region sequences fro the endogenous xenotropic virus, Bxv-1. However, the majority of tumors from another highly leukemic strain, CWD, contained recombinant viruses that lacked Bxv-1-specific sequences. The nucleotide sequence of the U3 regions of two such CWD recombinants was nearly identical to that of the endogenous ecotropic virus parent Emv-1, but they shared three nucleotide substitutions immediately 3' of the enhancer core. These substitutions were found in recombinant proviruses from about one-third of spontaneous CWD lymphomas as determined by an oligonucleotide hybridization assay of proviral fragments that had been nucleotide substitutions in the CWD viruses were inherited from an endogenous polytropic provirus that is absent in the other highly leukemic strains. On the basis of the results of these and previous studies, we propose that CWD recombinants acquire pathogenic U3 region sequences through recombination with an endogenous polytropic virus or Bxv-1 and that the pathogenicity of these sequences may be related to a sequence motif that is known to bind members of the basic helix-loop-helix class of transcription factors. Images

Massey, A C; Lawrenz-Smith, S C; Innes, D J; Thomas, C Y

1994-01-01

423

Molecular Evolution of the Plant R Regulatory Gene Family  

PubMed Central

Anthocyanin pigmentation patterns in different plant species are controlled in part by members of the myc-like R regulatory gene family. We have examined the molecular evolution of this gene family in seven plant species. Three regions of the R protein show sequence conservation between monocot and dicot R genes. These regions encode the basic helix-loop-helix domain, as well as conserved N-terminal and C-terminal domains; mean replacement rates for these conserved regions are 1.02 X 10(-9) nonsynonymous nucleotide substitutions per site per year. More than one-half of the protein, however, is diverging rapidly, with nonsynonymous substitution rates of 4.08 X 10(-9) substitutions per site per year. Detailed analysis of R homologs within the grasses (Poaceae) confirm that these variable regions are indeed evolving faster than the flanking conserved domains. Both nucleotide substitutions and small insertion/deletions contribute to the diversification of the variable regions within these regulatory genes. These results demonstrate that large tracts of sequence in these regulatory loci are evolving at a fairly rapid rate.

Purugganan, M. D.; Wessler, S. R.

1994-01-01

424

Verification at the protein level of the PIF4-mediated external coincidence model for the temperature-adaptive photoperiodic control of plant growth in Arabidopsis thaliana  

PubMed Central

Plant circadian clock controls a wide variety of physiological and developmental events, which include the short-days (SDs)-specific promotion of the elongation of hypocotyls during de-etiolation and also the elongation of petioles during vegetative growth. In A. thaliana, the PIF4 gene encoding a phytochrome-interacting basic helix-loop-helix (bHLH) transcription factor plays crucial roles in this photoperiodic control of plant growth. According to the proposed external coincidence model, the PIF4 gene is transcribed precociously at the end of night specifically in SDs, under which conditions the protein product is stably accumulated, while PIF4 is expressed exclusively during the daytime in long days (LDs), under which conditions the protein product is degraded by the light-activated phyB and also the residual proteins are inactivated by the DELLA family of proteins. A number of previous reports provided solid evidence to support this coincidence model mainly at the transcriptional level of the PIF4 and PIF4-traget genes. Nevertheless, the diurnal oscillation profiles of PIF4 proteins, which were postulated to be dependent on photoperiod and ambient temperature, have not yet been demonstrated. Here we present such crucial evidence on PIF4 protein level to further support the external coincidence model underlying the temperature-adaptive photoperiodic control of plant growth in A. thaliana.

Yamashino, Takafumi; Nomoto, Yuji; Lorrain, Severine; Miyachi, Miki; Ito, Shogo; Nakamichi, Norihito; Fankhauser, Christian; Mizuno, Takeshi

2013-01-01

425

H1-mediated repression of transcription factor binding to a stably positioned nucleosome.  

PubMed

Previously, we reported that histone H1 binding to nucleosome cores results in the repression of binding of the basic helix-loop-helix upstream stimulatory factor (USF) (Juan, L.-J., Utley, R. T., Adams, C. C., Vettese-Dadey, M., and Workman, J. L. (1994) EMBO J. 13, 6031-6040). We have tested whether this inhibition resulted from H1-mediated changes in nucleosome positioning (Ura, K., Hayes, J. J., and Wolffe, A. P. (1995) EMBO J. 14, 3752-3765) forcing the USF recognition sequence into less accessible locations within the nucleosome. Nucleosome boundaries were determined by assays combining micrococcal nuclease and restriction endonuclease digestion. A unique pair of boundaries were observed, indicating a single nucleosome translational position. This nucleosome position did not change on H1 or USF binding. Thus, H1 repression of USF binding was independent of nucleosome mobility, indicating an alternative mechanism of H1 repression. H1 repressed USF binding at a site 35 base pairs into the nucleosome core more effectively than at a site near the "linker" DNA, suggesting that inhibition by H1 was not simply due to steric occlusion. Instead, these data are consistent with a model by which H1 binding reduces transient dynamic exposure of the DNA from the histone octamer surface (Polach, K. L., and Widom, J. (1995) J. Mol. Biol. 254, 130-149). PMID:9013616

Juan, L J; Utley, R T; Vignali, M; Bohm, L; Workman, J L

1997-02-01

426

Sequence-specific transcriptional activation by Myc and repression by Max.  

PubMed Central

The c-Myc oncoprotein, which is required for cellular proliferation, resembles in its structure a growing number of transcription factors. However, the mechanism of its action in vivo is not yet clear. The discovery of the specific cognate DNA-binding site for Myc and its specific heterodimerization partner, Max, enabled the use of direct experiments to elucidate how Myc functions in vivo and how this function is modulated by Max. Here we demonstrate that exogenously expressed Myc is capable of activating transcription in vivo through its specific DNA-binding site. Moreover, transcriptional activation by Myc is dependent on the basic region, the integrity of the helix-loop-helix and leucine zipper dimerization motifs located in the carboxy-terminal portion of the protein, and the regions in the amino terminus conserved among Myc family proteins. In contrast to Myc, exogenously expressed Max elicited transcriptional repression and blocked transcriptional activation by Myc through the same DNA-binding site. Our results suggest a functional antagonism between Myc and Max which is mediated by their relative levels in the cells. A model for the activity of Myc and Max in vivo is presented. Images

Amin, C; Wagner, A J; Hay, N

1993-01-01

427

Achaete-scute homologue-1 tapers neuroendocrine cell differentiation in lungs after exposure to naphthalene.  

PubMed

The basic helix-loop-helix transcription factor achaete-scute homologue-1 (ASH1) plays a critical role in regulating the neuroendocrine (NE) phenotype in normal and neoplastic lung. Transgenic (TG) mice that constitutively express human ASH1 (hASH1) under control of the Clara cell 10-kDa protein (CC10) promoter in non-NE airway lining cells display progressive epithelial hyperplasia and bronchiolar metaplasia or bronchiolization of the alveoli (BOA). However, little is known about the involvement of hASH1 in regeneration of the conducting airway. In this study, we investigated the impact of hASH1 on airway cell injury and repair in the TG mice following an intraperitoneal injection of naphthalene, which specifically ablates bronchiolar Clara cells and induces pulmonary NE cell hyperplasia. We discovered an overall attenuation of NE maturation coupled with increased proliferation in TG mice during post-naphthalene repair. In addition, BOA lesions revealed enhanced epithelial cell proliferation while preserving Clara cell markers CC10 and the principal naphthalene-metabolizing enzyme cytochrome P4502F2. These data suggest that ASH1 may play an important role in maintaining a progenitor phenotype that promotes renewal of both NE and epithelial cells. Moreover, ASH1 may propagate a stem cell microenvironment in BOA where epithelium becomes resistant to naphthalene toxicity. PMID:20554700

Jensen-Taubman, Sandra; Wang, Xiao-Yang; Linnoila, R Ilona

2010-06-16

428

ASH1 gene is a specific therapeutic target for lung cancers with neuroendocrine features.  

PubMed

Lung cancers with neuroendocrine features are usually aggressive, although the underlying molecular mechanisms largely remain to be determined. The basic helix-loop-helix protein, achaete-scute complex-like 1/achaete-scute homologue 1 (ASH1), is expressed in normal fetal pulmonary neuroendocrine cells and lung cancers with neuroendocrine elements and is suggested to be involved in lung carcinogenesis. In the present study, we show inhibition of ASH1 expression by plasmid-based RNA interference (RNAi) to significantly suppress growth of lung cancer cells with ASH1 expression through G2-M cell cycle arrest and accumulation of sub-G1 populations, possibly linked to cleavage of caspase-9 and caspase-7. However, lung cancer cell lines without ASH1 expression and immortalized normal BEAS2B bronchial epithelial cells were not affected. The RNAi-resistant mutant ASH1 clearly induced rescue from G2-M arrest, suggesting a target-specific effect of RNAi. An ASH1-RNAi adenovirus was also established and significantly inhibited not only in vitro cell proliferation but also in vivo xenograft growth of ASH1-positive NCI-H460 cells. Elevated levels of apoptosis were also observed in NCI-H460 xenografts with the ASH1-RNAi adenovirus. The present study therefore suggests that ASH1 plays a crucial role in lung cancer development and may be an effective therapeutic target in lung cancers with neuroendocrine features. PMID:16322211

Osada, Hirotaka; Tatematsu, Yoshio; Yatabe, Yasushi; Horio, Yoshitsugu; Takahashi, Takashi

2005-12-01

429

Far-red light inhibits germination through DELLA-dependent stimulation of ABA synthesis and ABI3 activity  

PubMed Central

Under the canopy, far-red (FR) light represses seed germination by inactivating phytochrome photoreceptors. This elicits a decrease in gibberellins (GA) levels and an increase in abscisic acid (ABA) levels. GA promotes germination by enhancing the proteasome-mediated destruction of DELLA repressors. ABA prevents germination by stimulating the expression of ABI repressors. How phytochromes elicit changes in hormone levels or how GA- and ABA-dependent signals are coordinated to repress germination remains poorly understood. We show that repression of germination by FR light involves stabilized DELLA factors GAI, RGA and RGL2 that stimulate endogenous ABA synthesis. In turn, ABA blocks germination through the transcription factor ABI3. The role of PIL5, a basic helix-loop-helix transcription factor stimulating GAI and RGA expression, is significant, provided GA synthesis is high enough; otherwise, high GAI and RGA protein levels persist to block germination. Under white light, GAI and RGA driven by the RGL2 promoter can substitute for RGL2 to promote ABA synthesis and repress germination, consistent with the recent findings with RGL2. The three DELLA factors inhibit testa rupture whereas ABI3 blocks endosperm rupture.

Piskurewicz, Urszula; Tureckova, Veronika; Lacombe, Eric; Lopez-Molina, Luis

2009-01-01

430

Down-Regulation of Myogenin Can Reverse Terminal Muscle Cell Differentiation  

PubMed Central

Certain higher vertebrates developed the ability to reverse muscle cell differentiation (dedifferentiation) as an additional mechanism to regenerate muscle. Mammals, on the other hand, show limited ability to reverse muscle cell differentiation. Myogenic Regulatory Factors (MRFs), MyoD, myogenin, Myf5 and Myf6 are basic-helix-loop-helix (bHLH) transcription factors essential towards the regulation of myogenesis. Our current interest is to investigate whether down-regulation of MRFs in terminally differentiated mouse myotubes can induce reversal of muscle cell differentiation. Results from this work showed that reduction of myogenin levels in terminally differentiated mouse myotubes can reverse their differentiation state. Down-regulation of myogenin in terminally differentiated mouse myotubes induces cellular cleavage into mononucleated cells and cell cycle re-entry, as shown by re-initiation of DNA synthesis and increased cyclin D1 and cyclin E2 levels. Finally, we provide evidence that down-regulation of myogenin causes cell cycle re-entry (via down-regulation of MyoD) and cellularisation through separate pathways. These data reveal the important role of myogenin in maintaining terminal muscle cell differentiation and point to a novel mechanism by which muscle cells could be re-activated through its down-regulation.

Mastroyiannopoulos, Nikolaos P.; Nicolaou, Paschalis; Anayasa, Mustafa; Uney, James B.; Phylactou, Leonidas A.

2012-01-01

431

Hand2 is required in the epithelium for palatogenesis in mice  

PubMed Central

Summary The basic helix-loop-helix (bHLH) transcription factor Hand2 has been implicated in the development of multiple organs, including craniofacial organs. Mice carrying Hand2 hypomorphic alleles (Hand2LoxP/?) display a cleft palate phenotype. A specific deletion of the Hand2 branchial arch-specific enhancer also leads to a hypoplastic mandible and cleft palate formation in mice. However, the underlying mechanism of Hand2 regulation of palate development remains unknown. Here we show that Hand2 is expressed in both the epithelium and mesenchyme of the developing palate. While mesenchymal specific inactivation of Hand2 has no impact on palate development, epithelial specific deletion of Hand2 creates a cleft palate phenotype. Hand2 appears to exert distinct roles in the anterior and posterior palate. In the anterior palate of Hand2LoxP/? mice, premature death of periderm cells and a down-regulation of Shh are observed in the medial edge epithelium (MEE), accompanied by a decreased level of cell proliferation in the palatal mesenchyme. In the posterior palate, a lower dose of Hand2 causes aberrant periderm cell death on the surface of the epithelium, triggering abnormal fusion between the palatal shelf and mandible and preventing palatal shelf elevation. We further demonstrate that BMP activities are essential for the expression of Hand2 in the palate. We conclude that Hand2 is an intrinsic regulator in the epithelium and is required for palate development.

Xiong, Wei; He, Fenglei; Morikawa, Yuka; Yu, Xueyan; Zhang, Zunyi; Lan, Yu; Jiang, Rulang; Cserjesi, Peter; Chen, YiPing

2009-01-01

432

Specific inactivation of Twist1 in the mandibular arch neural crest cells affects the development of the ramus and reveals interactions with Hand2  

PubMed Central

Background The basic Helix-Loop-Helix (bHLH) transcription factor Twist1 fulfills an essential function in neural crest cell formation, migration and survival and is associated with the craniosynostic Saethre-Chotzen syndrome in humans. However, its functions during mandibular development, when it may interact with other bHLH transcription factors like Hand2, are unknown since mice homozygous for the Twist1 null mutation die in early embryogenesis. To determine the role of Twist1 during mandibular development, we used the Hand2-Cre transgene to conditionally inactivate the gene in the neural crest cells populating the mandibular pharyngeal arch. Results The mutant mice exhibited a spectrum of craniofacial anomalies, including mandibular hypoplasia, altered middle ear development, and cleft palate. It appears that Twist1 is essential for the survival of the neural crest cells involved in the development of the mandibular ramal elements. Twist1 plays a role in molar development and cusp formation by participating in the reciprocal signaling needed for the formation of the enamel knot. This gene is also needed to control the ossification of the mandible, a redundant role shared with Hand2. Conclusion Twist1, along with Hand2, is essential for the proximo-distal patterning and development of the mandible and ossification.

Zhang, Yanping; Blackwell, Evan L.; McKnight, Mitchell T.; Knutsen, Gregory R.; Vu, Wendy T.; Ruest, L. Bruno

2012-01-01

433

Hand transcription factors cooperatively regulate development of the distal midline mesenchyme  

PubMed Central

Hand proteins are evolutionally conserved basic helix-loop-helix (bHLH) transcription factors implicated in development of neural crest-derived tissues, heart and limb. Hand1 is expressed in the distal (ventral) zone of the branchial arches, whereas the Hand2 expression domain extends ventrolaterally to occupy two-thirds of the mandibular arch. To circumvent the early embryonic lethality of Hand1 or Hand2-null embryos and to examine their roles in neural crest development, we generated mice with neural crest-specific deletion of Hand1 and various combinations of mutant alleles of Hand2. Ablation of Hand1 alone in neural crest cells did not affect embryonic development, however, further removing one Hand2 allele or deleting the ventrolateral branchial arch expression of Hand2 lead to a novel phenotype presumably due to impaired growth of the distal midline mesenchyme. Although we failed to detect changes in proliferation or apoptosis between the distal mandibular arch of wild-type and Hand1/Hand2 compound mutants at embryonic day (E)10.5, dysregulation of Pax9, Msx2 and Prx2 was observed in the distal mesenchyme at E12.5. In addition, the inter-dental mesenchyme and distal symphysis of Meckel’s cartilage became hypoplastic, resulting in the formation of a single fused lower incisor within the hypoplastic fused mandible. These findings demonstrate the importance of Hand transcription factors in the transcriptional circuitry of craniofacial and tooth development.

Barbosa, Ana C.; Funato, Noriko; Chapman, Shelby; McKee, Marc D.; Richardson, James A.; Olson, Eric N.; Yanagisawa, Hiromi

2008-01-01

434

G9a mediates Sharp-1-dependent inhibition of skeletal muscle differentiation.  

PubMed

Sharp-1, a basic helix-loop-helix transcription factor, is a potent repressor of skeletal muscle differentiation and is dysregulated in muscle pathologies. However, the mechanisms by which it inhibits myogenesis are not fully understood. Here we show that G9a, a lysine methyltransferase, is involved in Sharp-1-mediated inhibition of muscle differentiation. We demonstrate that G9a directly interacts with Sharp-1 and enhances its ability to transcriptionally repress the myogenin promoter. Concomitant with a differentiation block, G9a-dependent histone H3 lysine 9 dimethylation (H3K9me2) and MyoD methylation are apparent upon Sharp-1 overexpression in muscle cells. RNA interference-mediated reduction of G9a or pharmacological inhibition of its activity erases these repressive marks and rescues the differentiation defect imposed by Sharp-1. Our findings provide new insights into Sharp-1-dependent regulation of myogenesis and identify epigenetic mechanisms that could be targeted in myopathies characterized by elevated Sharp-1 levels. PMID:23087213

Ling, Belinda Mei Tze; Gopinadhan, Suma; Kok, Wai Kay; Shankar, Shilpa Rani; Gopal, Pooja; Bharathy, Narendra; Wang, Yaju; Taneja, Reshma

2012-10-19

435

ANTHOCYANIN1 of Petunia Controls Pigment Synthesis, Vacuolar pH, and Seed Coat Development by Genetically Distinct Mechanisms  

PubMed Central

ANTHOCYANIN1 (AN1) of petunia is a transcription factor of the basic helix-loop-helix (bHLH) family that is required for the synthesis of anthocyanin pigments. Here, we show that AN1 controls additional aspects of cell differentiation: the acidification of vacuoles in petal cells, and the size and morphology of cells in the seed coat epidermis. We identified an1 alleles, formerly known as ph6, that sustain anthocyanin synthesis but not vacuolar acidification and seed coat morphogenesis. These alleles express truncated proteins lacking the C-terminal half of AN1, including the bHLH domain, at an ?30-fold higher level than wild-type AN1. An allelic series in which one, two, or three amino acids were inserted into the bHLH domain indicated that this domain is required for both anthocyanin synthesis and vacuolar acidification. These findings show that AN1 controls more aspects of epidermal cell differentiation than previously thought through partially separable domains.

Spelt, Cornelis; Quattrocchio, Francesca; Mol, Joseph; Koes, Ronald

2002-01-01

436

Isolation of a Regulatory Gene of Anthocyanin Biosynthesis in Tuberous Roots of Purple-Fleshed Sweet Potato[OA  

PubMed Central

Many transcriptional factors harboring the R2R3-MYB domain, basic helix-loop-helix domain, or WD40 repeats have been identified in various plant species as regulators of flavonoid biosynthesis in flowers, seeds, and fruits. However, the regulatory elements of flavonoid biosynthesis in underground organs have not yet been elucidated. We isolated the novel MYB genes IbMYB1 and IbMYB2s from purple-fleshed sweet potato (Ipomoea batatas L. Lam. cv Ayamurasaki). IbMYB1 was predominantly expressed in the purple flesh of tuberous roots but was not detected (or only scarcely) in other anthocyanin-containing tissues such as nontuberous roots, stems, leaves, or flowers. IbMYB1 was also expressed in the tuberous roots of other purple-fleshed cultivars but not in those of orange-, yellow-, or white-fleshed cultivars. Although the orange- or yellow-fleshed cultivars contained anthocyanins in the skins of their tuberous roots, we could not detect IbMYB1 transcripts in these tissues. These results suggest that IbMYB1 controls anthocyanin biosynthesis specifically in the flesh of tuberous roots. The results of transient and stable transformation experiments indicated that expression of IbMYB1 alone was sufficient for induction of all structural anthocyanin genes and anthocyanin accumulation in the flesh of tuberous roots, as well as in heterologous tissues or heterologous plant species.

Mano, Hironori; Ogasawara, Fumiaki; Sato, Kazuhito; Higo, Hiromi; Minobe, Yuzo

2007-01-01

437

Genome-wide association mapping to candidate polymorphism resolution in the unsequenced barley genome.  

PubMed

Although commonplace in human disease genetics, genome-wide association (GWA) studies have only relatively recently been applied to plants. Using 32 phenotypes in the inbreeding crop barley, we report GWA mapping of 15 morphological traits across ?500 cultivars genotyped with 1,536 SNPs. In contrast to the majority of human GWA studies, we observe high levels of linkage disequilibrium within and between chromosomes. Despite this, GWA analysis readily detected common alleles of high penetrance. To investigate the potential of combining GWA mapping with comparative analysis to resolve traits to candidate polymorphism level in unsequenced genomes, we fine-mapped a selected phenotype (anthocyanin pigmentation) within a 140-kb interval containing three genes. Of these, resequencing the putative anthocyanin pathway gene HvbHLH1 identified a deletion resulting in a premature stop codon upstream of the basic helix-loop-helix domain, which was diagnostic for lack of anthocyanin in our association and biparental mapping populations. The methodology described here is transferable to species with limited genomic resources, providing a paradigm for reducing the threshold of map-based cloning in unsequenced crops. PMID:21115826

Cockram, James; White, Jon; Zuluaga, Diana L; Smith, David; Comadran, Jordi; Macaulay, Malcolm; Luo, Zewei; Kearsey, Mike J; Werner, Peter; Harrap, David; Tapsell, Chris; Liu, Hui; Hedley, Peter E; Stein, Nils; Schulte, Daniela; Steuernagel, Burkhard; Marshall, David F; Thomas, William T B; Ramsay, Luke; Mackay, Ian; Balding, David J; Waugh, Robbie; O'Sullivan, Donal M

2010-11-29

438

Genome-wide association mapping to candidate polymorphism resolution in the unsequenced barley genome  

PubMed Central

Although commonplace in human disease genetics, genome-wide association (GWA) studies have only relatively recently been applied to plants. Using 32 phenotypes in the inbreeding crop barley, we report GWA mapping of 15 morphological traits across ?500 cultivars genotyped with 1,536 SNPs. In contrast to the majority of human GWA studies, we observe high levels of linkage disequilibrium within and between chromosomes. Despite this, GWA analysis readily detected common alleles of high penetrance. To investigate the potential of combining GWA mapping with comparative analysis to resolve traits to candidate polymorphism level in unsequenced genomes, we fine-mapped a selected phenotype (anthocyanin pigmentation) within a 140-kb interval containing three genes. Of these, resequencing the putative anthocyanin pathway gene HvbHLH1 identified a deletion resulting in a premature stop codon upstream of the basic helix-loop-helix domain, which was diagnostic for lack of anthocyanin in our association and biparental mapping populations. The methodology described here is transferable to species with limited genomic resources, providing a paradigm for reducing the threshold of map-based cloning in unsequenced crops.

Cockram, James; White, Jon; Zuluaga, Diana L.; Smith, David; Comadran, Jordi; Macaulay, Malcolm; Luo, Zewei; Kearsey, Mike J.; Werner, Peter; Harrap, David; Tapsell, Chris; Liu, Hui; Hedley, Peter E.; Stein, Nils; Schulte, Daniela; Steuernagel, Burkhard; Marshall, David F.; Thomas, William T. B.; Ramsay, Luke; Mackay, Ian; Balding, David J.; Waugh, Robbie; O'Sullivan, Donal M.; Booer, Chris; Pike, Steve; Hamilton, Graeme; Jellis, Graham; Davies, Nigel; Ross, Anne; Bury, Paul; Habgood, Rodney; Klose, Steve; Vequaud, Dominique; Christerson, Therese; Brosnan, James; Newton, Adrian; Russell, Joanne; Shaw, Paul; Bayles, Rosemary; Wang, Minghui

2010-01-01

439

Identification and characterization of a novel 21.6-kDa tegumental protein from Clonorchis sinensis.  

PubMed

Tegumental proteins form a membrane-bound outer surface and are thus involved in host-parasite interactions and parasite survival. A complementary DNA clone encoding a novel 21.6-kDa tegumental protein (CsTegu21.6, accession number JF911532) was identified in a sequence library for the adult Clonorchis sinensis liver fluke. The complete coding sequence was 564 bp and encoded a protein of 188 amino acids. A BLASTX search revealed identities from 43 to 47% with previously identified tegumental proteins in C. sinensis and other helminthic parasites. Multiple alignment of the amino acids of CsTegu21.6 with those of four other C. sinensis tegumental proteins, CsTegu21.1, CsTegu22.3, CsTegu20.8 and CsTegu31.8, revealed pair-wise sequence identities ranging from 24 to 31.8%. A calcium-binding EF-hand domain containing a basic helix-loop-helix structure at the N terminus and a dynein light chain domain at the C terminus were found in CsTegu21.6; these motifs are common in tegumental proteins. CsTegu21.6 was specifically observed on the tegument of adult worms using immunolocalization analysis. PMID:22015384

Kim, Yu-Jung; Yoo, Won Gi; Lee, Myoung-Ro; Kim, Dae-Won; Lee, Won-Ja; Kang, Jung-Mi; Na, Byoung-Kuk; Ju, Jung-Won

2011-10-21

440

Analysis of the Hand1 cell lineage reveals novel contributions to cardiovascular, neural crest, extra-embryonic, and lateral mesoderm derivatives.  

PubMed

The basic Helix-Loop-Helix (bHLH) transcription factors Hand1 and Hand2 play critical roles in the development of multiple organ systems during embryogenesis. The dynamic expression patterns of these two factors within developing tissues obfuscate their respective unique and redundant organogenic functions. To define cell lineages potentially dependent upon Hand gene expression, we generated a mutant allele in which the coding region of Hand1 is replaced by Cre recombinase. Subsequent Cre-mediated activation of ?-galactosidase or eYFP reporter alleles enabled lineage trace analyses that clearly define the fate of Hand1-expressing cells. Hand1-driven Cre marks specific lineages within the extra embryonic tissues, placenta, sympathetic nervous system, limbs, jaw, and several cell types within the cardiovascular system. Comparisons between Hand1 expression and Hand1-lineage greatly refine our understanding of its dynamic spatial-temporal expression domains and raise the possibility of novel Hand1 functions in structures not thought to be Hand1-dependent. PMID:20882677

Barnes, Ralston M; Firulli, Beth A; Conway, Simon J; Vincentz, Joshua W; Firulli, Anthony B

2010-11-01

441

ShRNA-mediated gene silencing of AHR promotes the differentiation of P19 mouse embryonic carcinoma cells into cardiomyocytes.  

PubMed

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix (bHLH) transcription factor that is activated by environmental contaminants including polychlorinated biphenyls (PCBs). The AHR affects a variety of processes that are involved in cell growth and differentiation. In this study, we constructed a P19 embryonic carcinoma cell line with AHR gene silencing using the vector-based approach of short hairpin (sh)RNA interference that allows cells to differentiate into cardiac myocytes when treated with dimethyl sulfoxide (DMSO). The expression levels of the cardiac development-specific GATA4 and Nkx2.5 genes were measured using real-time quantitative polymerase chain reaction (qPCR). Our data showed that the expression levels of the GATA4 and Nkx2.5 genes were increased in the AHR-silenced P19 cells compared with the control groups. Four critical genes (ARNT, CYP1A1, GSK3? and ?-catenin) expressed in the AHR and in the Wnt signaling pathway were also measured by qPCR. We found that the expression levels of ARNT, CYP1A1 and ?-catenin were suppressed, whereas GSK3? expression was elevated in the AHR-silenced P19 cells. Therefore, it is possible that the silencing of AHR promotes the differentiation of P19 cells through the AHR and Wnt signal transduction pathway. PMID:22684894

Zhu, Chun; Chen, Yu-Lin; Wang, Xue-Jie; Hu, Xiao-Shan; Yu, Zhang-Bin; Han, Shu-Ping

2012-06-08

442

Aberrant upregulation of ASCL2 by promoter demethylation promotes the growth and resistance to 5-fluorouracil of gastric cancer cells.  

PubMed

Achaete scute-like 2 (ASCL2), a basic helix-loop-helix transcription factor, plays an essential role in the maintenance of adult intestinal stem cells. However, the function of ASCL2 in gastric cancer (GC) is poorly understood. Therefore, we investigated the roles and regulatory transcription mechanisms of ASCL2 in GC. Gene expression and methylation data analysis showed that ASCL2 was upregulated and hypomethylated in GC tissues. Using real-time RT-PCR and pyrosequen