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1

A comparison of methods for successful triggering of gene silencing in Coprinus cinereus  

Microsoft Academic Search

Post-transcriptional gene-silencing methods (PTGS), including RNAi, are becoming increasingly pervasive in functional genomics.\\u000a To advance analysis of the recently sequenced Coprinus cinereus genome, a high throughput gene silencing method is essential. We have exploited the GFP reporter gene to evaluate and quantify\\u000a efficacy of three different silencing strategies. Modular constructs that encompassed antisense, untranslatable sense, and RNAi-mediating hairpin sequences, were

Mary N. Heneghan; Ana M. S. B. Costa; Michael P. Challen; Peter R. Mills; Andy Bailey; Gary D. Foster

2007-01-01

2

RNA interference is ineffective as a routine method for gene silencing in chick embryos as monitored by fgf8 silencing  

PubMed Central

The in vivo accessibility of the chick embryo makes it a favoured model system for experimental developmental biology. Although the range of available techniques now extends to miss-expression of genes through in ovo electroporation, it remains difficult to knock out individual gene expression. Recently, the possibility of silencing gene expression by RNAi in chick embryos has been reported. However, published studies show only discrete quantitative differences in the expression of the endogenous targeted genes and unclear morphological alterations. To elucidate whether the tools currently available are adequate to silence gene expression sufficiently to produce a clear and specific null-like mutant phenotype, we have performed several experiments with different molecules that trigger RNAi: dsRNA, siRNA, and shRNA produced from a plasmid coexpressing green fluorescent protein as an internal marker. Focussing on fgf8 expression in the developing isthmus, we show that no morphological defects are observed, and that fgf8 expression is neither silenced in embryos microinjected with dsRNA nor in embryos microinjected and electroporated with a pool of siRNAs. Moreover, fgf8 expression was not significantly silenced in most isthmic cells transformed with a plasmid producing engineered shRNAs to fgf8. We also show that siRNA molecules do not spread significantly from cell to cell as reported for invertebrates, suggesting the existence of molecular differences between different model systems that may explain the different responses to RNAi. Although our results are basically in agreement with previously reported studies, we suggest, in contrast to them, that with currently available tools and techniques the number of cells in which fgf8 gene expression is decreased, if any, is not sufficient to generate a detectable mutant phenotype, thus making RNAi useless as a routine method for functional gene analysis in chick embryos.

2005-01-01

3

A virus-induced gene silencing method to study soybean cyst nematode parasitism in Glycine max  

PubMed Central

Background Bean pod mottle virus (BPMV) based virus-induced gene silencing (VIGS) vectors have been developed and used in soybean for the functional analysis of genes involved in disease resistance to foliar pathogens. However, BPMV-VIGS protocols for studying genes involved in disease resistance or symbiotic associations with root microbes have not been developed. Findings Here we describe a BPMV-VIGS protocol suitable for reverse genetic studies in soybean roots. We use this method for analyzing soybean genes involved in resistance to soybean cyst nematode (SCN). A detailed SCN screening pipeline is described. Conclusions The VIGS method described here provides a new tool to identify genes involved in soybean-nematode interactions. This method could be adapted to study genes associated with any root pathogenic or symbiotic associations.

2013-01-01

4

A simplified miRNA-based gene silencing method for Drosophila melanogaster  

PubMed Central

MicroRNA-based RNA interference is commonly used to produce loss-of-function phenotypes in mammalian systems, but is used only sparingly in invertebrates such as C. elegans and D. melanogaster. Here, we evaluate this method in transgenic strains of D. melanogaster and cultured S2 cells. High throughput-ready expression vectors were developed that permit rapid cloning of synthetic hairpin RNAs. As proof of concept, this method was used for the efficient silencing of dpp gene activity in the adult wing, and the analysis of the general RNA Polymerase II (Pol II) elongation factor, Nelf-E.

Haley, Benjamin; Hendrix, David; Trang, Vinh; Levine, Michael

2008-01-01

5

The two hit hypothesis: An improved method for siRNA-mediated gene silencing in stimulated primary human T cells.  

PubMed

Small interfering RNAs (siRNAs) have revolutionised cellular and molecular biology by uncovering new roles for genes in various biological processes and by providing new opportunities to silence gene expression for therapeutic purposes. A limiting factor of siRNA-mediated gene silencing, however, is the ability to efficiently deliver these molecules into hard-to-transfect cell types such as primary T cells. Nucleofection® technology, marketed by Lonza (Amaxa®), is an electroporation-based method that is commonly used for the delivery of siRNAs and plasmids into primary T cells. In this study we found that the recommended programs for nucleofection of stimulated primary human T cells with siRNAs inhibited cellular proliferation and were associated with a significant loss of cell viability. Furthermore, viable cells that survived the nucleofection procedure were perturbed in their ability to polarise in response to chemokine stimulation in comparison to mock nucleofections. We therefore evaluated other nucleofection programs and highlight one that resulted in significant silencing at the protein level following nucleofection with siRNAs, while maintaining cell viability and responsiveness to chemokine stimulation. Further optimisation of this method revealed that a second nucleofection with siRNAs after 72h significantly increased silencing compared to a single nucleofection. This new and improved two-hit nucleofection method for siRNA-mediated gene silencing in stimulated primary human T cells will therefore permit the investigation of genes and signalling pathways in the T cell immune response. PMID:23988722

Freeley, Michael; Long, Aideen

2013-08-27

6

Gene silencing in plants  

Microsoft Academic Search

The review considers the cytoplasmic silencing of viral RNAs by short RNAs and the silencing of endogenous mRNAs by specific\\u000a short double-stranded microRNAs. The role of some cell factors such as Dicer, Argonaute, RNA-dependent RNA polymerase, RNA\\u000a polymerase IV, and pectin methylesterase is described in detail. The role of viral proteins and nucleic acids in silencing\\u000a suppression and possible biotechnological

Yu. L. Dorokhov

2007-01-01

7

Systems and Methods for Silencing Expression of a Gene in a Cell and Uses Thereof.  

National Technical Information Service (NTIS)

The present invention provides RNA-based systems that are capable of silencing expression of a gene in a cell. Also provided are pharmaceutical compositions, cells, and kits that include the systems; cultures of primary cells that have been contacted with...

C. M. Troy L. A. Greene

2005-01-01

8

Constructs and methods for high-throughput gene silencing in plants  

Microsoft Academic Search

Gene silencing can be achieved by transformation of plants with constructs that express self-complementary (termed hairpin) RNA containing sequences homologous to the target genes. The DNA sequences encoding the self-complementary regions of hairpin (hp) RNA constructs form an inverted repeat. The inverted repeat can be stabilized in bacteria through separation of the self-complementary regions by a “spacer” region. When the

Chris Helliwell; Peter Waterhouse

2003-01-01

9

Constructs and Methods for Hairpin RNA-Mediated Gene Silencing in Plants  

Microsoft Academic Search

Double-stranded RNA (dsRNA) induces an endogenous sequence-specific RNA degradation mechanism in most eukaryotic cells. The mechanism can be harnessed to silence genes in plants by expressing self-complementary single-stranded (hairpin) RNA in which the duplexed region has the same sequence as part of the target gene's mRNA. We describe a number of plasmid vectors for generating hairpin RNAs, including those designed

Chris A. Helliwell; Peter M. Waterhouse

2005-01-01

10

A systemic gene silencing method suitable for high throughput, reverse genetic analyses of gene function in fern gametophytes  

Microsoft Academic Search

BACKGROUND: Ceratopteris richardii is a useful experimental system for studying gametophyte development and sexual reproduction in plants. However, few tools for cloning mutant genes or disrupting gene function exist for this species. The feasibility of systemic gene silencing as a reverse genetics tool was examined in this study. RESULTS: Several DNA constructs targeting a Ceratopteris protoporphyrin IX magnesium chelatase (CrChlI)

George Rutherford; Milos Tanurdzic; Mitsuyasu Hasebe; Jo Ann Banks

2004-01-01

11

Method: low-cost delivery of the cotton leaf crumple virus-induced gene silencing system  

PubMed Central

Background We previously developed a virus-induced gene silencing (VIGS) vector for cotton from the bipartite geminivirusCotton leaf crumple virus (CLCrV). The original CLCrV VIGS vector was designed for biolistic delivery by a gene gun. This prerequisite limited the use of the system to labs with access to biolistic equipment. Here we describe the adaptation of this system for delivery by Agrobacterium (Agrobacterium tumefaciens). We also describe the construction of two low-cost particle inflow guns. Results The biolistic CLCrV vector was transferred into two Agrobacterium binary plasmids. Agroinoculation of the binary plasmids into cotton resulted in silencing and GFP expression comparable to the biolistic vector. Two homemade low-cost gene guns were used to successfully inoculate cotton (G. hirsutum) and N. benthamiana with either the CLCrV VIGS vector or the Tomato golden mosaic virus (TGMV) VIGS vector respectively. Conclusions These innovations extend the versatility of CLCrV-based VIGS for analyzing gene function in cotton. The two low-cost gene guns make VIGS experiments affordable for both research and teaching labs by providing a working alternative to expensive commercial gene guns.

2012-01-01

12

RNA Interference and Antisense Mediated Gene Silencing  

Microsoft Academic Search

Gene silencing by RNA interference (RNAi) and by antisense RNA are powerful tools to interfere with the expression of eukryotic genes. Since the first description of RNAi in 1998, antisense-mediated gene silencing has been considered to have essentially the same mechanism as gene silencing by RNAi. However, while substantial effort has been made to dissect the RNAi pathway, the cellular

Markus Kuhlmann; Blaga Popova; Wolfgang Nellen

13

Plant DNA viruses and gene silencing  

Microsoft Academic Search

Gene silencing is a multifaceted phenomenon leading to propagative down-regulation of gene expression. Gene silencing, first observed in plants containing transgenes, can operate both at the transcriptional and post-transcriptional levels. Silencing effects can be triggered by nuclear transgenes and by cytoplasmic RNA viruses, and it can be propagated between these elements and endogenous plant genes that share sequence homology. Although

Simon N. Covey; Nadia S. Al-Kaff

2000-01-01

14

DNA abrasion onto plants is an effective method for geminivirus infection and virus-induced gene silencing.  

PubMed

Geminiviruses belong to a rapidly growing group of plant pathogens that contribute to crop losses in tropical and subtropical areas of the world. Geminivirus infection is a model for plant DNA replication and virus/host interactions. Geminiviruses are also used as vectors to induce silencing of endogenous genes in several plant species. A method was analyzed for inoculating geminiviruses using plasmid DNA rubbed onto leaves in the presence of an abrasive (DNA abrasion). Although the use of DNA abrasion to inoculate geminiviruses has been described previously, the technique has fallen out of favor and has not been systematically optimized. However, consistent efficiencies of 100% infection rates can be achieved by DNA abrasion. The symptoms of Tomato Golden Mosaic Virus or Cabbage Leaf Curl Virus infection on Nicotiana benthamiana were similar in timing and appearance to the symptoms observed in plants inoculated using Agrobacterium as the delivery method. More importantly, silencing of an endogenous gene was highly efficient when a geminivirus silencing vector was inoculated by the DNA abrasion method. Other plant species successfully inoculated with geminiviruses by DNA abrasion were Nicotiana tabacum, Capsicum annuum and Nicandra physalodes. Unfortunately, Arabidopsis thaliana could not be infected with Cabbage Leaf Curl Virus using leaf abrasion, demonstrating limitation of the method. However, leaf abrasion to inoculate geminiviruses is an easy and inexpensive method that should be considered as an accessible technique to the growing number of researchers using geminiviruses. PMID:17337069

Ascencio-Ibañez, Jose Trinidad; Settlage, Sharon B

2007-03-06

15

Posttranscriptional gene silencing across kingdoms  

Microsoft Academic Search

Post-transcriptional gene silencing (PTGS) as a consequence of the introduction of either transgenes or double-stranded RNA molecules has been found to occur in a number of species. In the past year, studies in different systems have greatly enhanced our understanding of the molecular mechanisms of these phenomena. The ubiquitous presence of PTGS in both the plant and animal kingdoms and

Carlo Cogoni; Giuseppe Macino

2000-01-01

16

Applying gene silencing technology to contraception.  

PubMed

Population control of feral animals is often difficult, as it can be dangerous for the animals, labour intensive and expensive. Therefore, a useful tool for control of animal populations would be a non-surgical method to induce sterility. Our laboratories utilize methods aimed at targeting brain cells in vivo with vehicles that deliver a payload of either inhibitory RNAs or genes intended to correct cellular dysfunction. A useful framework for design of a new approach will be the combination of these methods with the intended goal to produce a technique that can be used to non-invasively sterilize cats and dogs. For this approach to succeed, it has to meet several conditions: the target gene must be essential for fertility; the method must include a mechanism to effectively and specifically silence the gene of interest; the method of delivering the silencing agent must be minimally invasive, and finally, the silencing effect must be sustained for the lifespan of the target species, so that expansion of the population can be effectively prevented. In this article, we discuss our work to develop gene silencing technology to induce sterility; we will use examples of our previous studies demonstrating that this approach is viable. These studies include (i) the use of viral vectors able to disrupt reproductive cyclicity when delivered to the regions of the brain involved in the control of reproduction and (ii) experiments with viral vectors that are able to ameliorate neuronal disease when delivered systemically using a novel approach of gene therapy. PMID:23279544

Dissen, G A; Lomniczi, A; Boudreau, R L; Chen, Y H; Davidson, B L; Ojeda, S R

2012-12-01

17

Aging: gene silencing or gene activation?  

PubMed

According to the author's theory of gene silencing, the key process in aging involves reduced expression of a number of genes. Silencing of genes has a complex mechanism, which involves methylation of DNA, histone modification and chromatin remodeling. In addition to deacetylation of the histones and methylation of DNA, recently described RNAi mechanism could initiate formation of silenced chromatin. Hypermethylation of the promoter will silence the gene. Genome-wide hypomethylation will induce genomic instability, amplification of oncogenes and also silencing of the genes through RNAi mechanism. Studies by different groups, conducted in yeast, worms, flies and mice, confirmed substantial changes in gene expression in aging. Among them, the most important was silencing of tumor suppressors and other genes involved in the control of cell cycle, apoptosis, detoxification, and cholesterol metabolism. There was also increased expression of the smaller group of oncogenes and other genes which are associated with typical diseases of old age. Caloric restriction normalizes expression of a substantial percentage of these genes. Animal studies confirmed importance of caloric restriction, which decreases signaling through the IGF-1/AKT pathway and expression of gene p53. These studies, however, cannot be directly applied to human aging. It is proposed that age management therapy should attempt to normalize gene expression in the older population to the level typical for young adults. This would require activation of silenced genes and normalization of overexpressed genes. Caloric restriction and exercise are helpful in decreasing the activity of important oncogenes and activation of silenced tumor suppressors, and may have a positive impact, not only on aging, but also on prevention of cancer. Dietary supplements containing phytochemicals should normalize increased expression of oncogenes. Examples are: genistein and EGCG, which effect signaling through the IGF-1/AKT pathway and resveratrol and limonen, which do so through the RAS pathway. A group of amino acid derivatives and organic acids of animal and human origin should activate silenced tumor suppressor genes (Aminocare A10, Aminocare Extra). Among them 3-phenylacetylamino-2, 6-piperidinedione intercalates specifically with DNA and protects sequences of tumor suppressor genes, which are vulnerable to the effects of carcinogens. Phenylacetate activates p53 and p21 through inhibition of methyltransferase and farnesylation of the RAS protein. Phenylbutyrate activates tumor suppressor genes through inhibition of histone deacetylation. Phenylacetylglutamine decreases genomic instability and expression of oncogenes and promotes apoptosis. The application of DNA microarray techniques to human studies should provide more information about differences in gene expression in different age groups and help design more effective age management regimens. PMID:15533642

Burzynski, Stanislaw R

2005-01-01

18

Posttranscriptional gene silencing in nuclei.  

PubMed

In plants, small interfering RNAs (siRNAs) with sequence homology to transcribed regions of genes can guide the sequence-specific degradation of corresponding mRNAs, leading to posttranscriptional gene silencing (PTGS). The current consensus is that siRNA-mediated PTGS occurs primarily in the cytoplasm where target mRNAs are localized and translated into proteins. However, expression of an inverted-repeat double-stranded RNA corresponding to the soybean FAD2-1A desaturase intron is sufficient to silence FAD2-1, implicating nuclear precursor mRNA (pre-mRNA) rather than cytosolic mRNA as the target of PTGS. Silencing FAD2-1 using intronic or 3'-UTR sequences does not affect transcription rates of the target genes but results in the strong reduction of target transcript levels in the nucleus. Moreover, siRNAs corresponding to pre-mRNA-specific sequences accumulate in the nucleus. In Arabidopsis, we find that two enzymes involved in PTGS, Dicer-like 4 and RNA-dependent RNA polymerase 6, are localized in the nucleus. Collectively, these results demonstrate that siRNA-directed RNA degradation can take place in the nucleus, suggesting the need for a more complex view of the subcellular compartmentation of PTGS in plants. PMID:21173264

Hoffer, Paul; Ivashuta, Sergey; Pontes, Olga; Vitins, Alexa; Pikaard, Craig; Mroczka, Andrew; Wagner, Nicholas; Voelker, Toni

2010-12-20

19

Posttranscriptional gene silencing in nuclei  

PubMed Central

In plants, small interfering RNAs (siRNAs) with sequence homology to transcribed regions of genes can guide the sequence-specific degradation of corresponding mRNAs, leading to posttranscriptional gene silencing (PTGS). The current consensus is that siRNA-mediated PTGS occurs primarily in the cytoplasm where target mRNAs are localized and translated into proteins. However, expression of an inverted-repeat double-stranded RNA corresponding to the soybean FAD2-1A desaturase intron is sufficient to silence FAD2-1, implicating nuclear precursor mRNA (pre-mRNA) rather than cytosolic mRNA as the target of PTGS. Silencing FAD2-1 using intronic or 3?-UTR sequences does not affect transcription rates of the target genes but results in the strong reduction of target transcript levels in the nucleus. Moreover, siRNAs corresponding to pre-mRNA–specific sequences accumulate in the nucleus. In Arabidopsis, we find that two enzymes involved in PTGS, Dicer-like 4 and RNA-dependent RNA polymerase 6, are localized in the nucleus. Collectively, these results demonstrate that siRNA-directed RNA degradation can take place in the nucleus, suggesting the need for a more complex view of the subcellular compartmentation of PTGS in plants.

Hoffer, Paul; Ivashuta, Sergey; Pontes, Olga; Vitins, Alexa; Pikaard, Craig; Mroczka, Andrew; Wagner, Nicholas; Voelker, Toni

2011-01-01

20

Gene silencing by synthetic U1 Adaptors  

Microsoft Academic Search

We describe a gene silencing method that employs a mechanism of action distinct from those of antisense and RNA interference. U1 Adaptors are bifunctional oligonucleotides with a 'target domain' complementary to a site in the target gene's terminal exon and a 'U1 domain' that binds to the U1 small nuclear RNA component of the U1 small nuclear ribonucleoprotein (U1 snRNP)

Rafal Goraczniak; Mark A Behlke; Samuel I Gunderson

2009-01-01

21

RNA Interference and Antisense Mediated Gene Silencing  

Microsoft Academic Search

Gene silencing by RNA interference (RNAi) and by antisense RNA are powerful tools to interfere with the expression of eukryotic\\u000a genes. Since the first description of RNAi in 1998, antisense-mediated gene silencing has been considered to have essentially\\u000a the same mechanism as gene silencing by RNAi. However, while substantial effort has been made to dissect the RNAi pathway,\\u000a the cellular

Markus Kuhlmann; Blaga Popova; Wolfgang Nellen

22

Environmentally Induced Gene Silencing in Breast Cancer.  

National Technical Information Service (NTIS)

The main goal of the study was to test the hypothesis that a reduction in gene expression could induce gene silencing (i.e. relatively stable loss of gene expression) in breast cells. Silencing of a variety of tumor suppressor genes plays a major role in ...

M. Turker

2008-01-01

23

Alcohol Polymeric Nanoparticles for Gene Silencing Applications  

Microsoft Academic Search

Gene silencing proves to be a promising technique for the treatment of genetic diseases by knocking down certain gene sequences in mRNA that code for specific proteins involved in genetic diseases. When using the correct short interfering RNA (siRNA), RNA interference machinery can be manipulated to silence almost any gene or protein expression in the human body, providing a new

Somer Hall; Amanda Portis; Gina Carballo; Greg Baker; Pat Walton; Christina Chan

24

Gene silencing – a new theory of aging  

Microsoft Academic Search

The aging process involves silencing of the genes through methylation of promoter sequences and the acetylation of histones. This process contributes not only to aging, but also cancer when silencing affects tumor suppressor genes. Antineoplastons work as molecular switches, turning inactive tumor suppressor genes back on through demethylation of the DNA and acetylation of the histones. While they activate tumor

Stanislaw R Burzynski

2003-01-01

25

An efficient method to enhance gene silencing by using precursor microRNA designed small hairpin RNAs  

Microsoft Academic Search

Gene silencing can be mediated by small interfering RNA (siRNA) and microRNA (miRNA). To investigate the potential application\\u000a of using a precursor microRNA (pre-miRNA) backbone for gene silencing, we studied the inhibition efficiency of exogenous GFP\\u000a and endogenous GAPDH by conventional shRNA- and pre-miRNA-designed hairpins, respectively. In this study, the conventional\\u000a shRNA-, pre-miRNA-30-, and pre-miRNA-155-designed hairpins targeting either GFP or

Zhixin Shan; Qiuxiong Lin; Chunyu Deng; Xiaohong Li; Wei Huang; Honghong Tan; Yongheng Fu; Min Yang; Xi-Yong Yu

2009-01-01

26

Virus-induced gene silencing for rice using agroinoculation.  

PubMed

Virus-induced gene silencing (VIGS) is a reverse genetics technique that is based on the RNA-mediated defense against viruses in plants. VIGS is a method of gene knockdown triggered by a replicating viral nucleic acid engineered to carry a host gene to be silenced. While there are a number of excellent VIGS vectors available for dicots, only a few are available for monocots. Here, we describe the detailed method of the use of a newly developed VIGS vector for rice, based on the rice-infecting Rice tungro bacilliform virus, a pararetrovirus with dsDNA genome. Using a method based on Agrobacterium-mediated injection of the VIGS construct at the meristematic region of young rice plants, silencing of target genes can be achieved and the silenced phenotype can be visualized in 3 weeks. PMID:23386293

Purkayastha, Arunima; Sharma, Shweta; Dasgupta, Indranil

2013-01-01

27

Common Themes in Mechanisms of Gene Silencing  

Microsoft Academic Search

The assembly of DNA into regions of inaccessible chromatin, called silent chromatin, is involved in the regulation of gene expression and maintenance of chromosome stability in eukaryotes. Recent studies on Sir2-containing silencing complexes in budding yeast and HP1- and Swi6-containing silencing complexes in metazoans and fission yeast suggest a common mechanism for the assembly of these domains, which involves the

Danesh Moazed

2001-01-01

28

Homology-dependent Gene Silencing in Paramecium  

Microsoft Academic Search

Microinjection at high copy number of plasmids containing only the coding region of a gene into the Paramecium somatic macronucleus led to a marked reduction in the expression of the corresponding endogenous gene(s). The silencing effect, which is stably maintained throughout vegetative growth, has been observed for all Paramecium genes examined so far: a single-copy gene (ND7), as well as

Francoise Ruiz; Laurence Vayssie; Catherine Klotz; Linda Sperling; Luisa Madeddu

1998-01-01

29

Application of gene silencing in plants  

Microsoft Academic Search

Recent studies of gene silencing in plants have revealed two RNA-mediated epigenetic processes, RNA-directed RNA degradation and RNA-directed DNA methylation. These natural processes have provided new avenues for developing high-efficiency, high-throughput technology for gene suppression in plants.

Ming-Bo Wang; Peter M Waterhouse

2002-01-01

30

Epigenetic gene silencing by Runx proteins  

Microsoft Academic Search

Runx family proteins have the potential for either activating or suppressing gene expression in a context-dependent manner. There are several mechanisms by which transcriptional repression can occur. A wide range of locus inactivation, that is often called gene silencing, is thought to be achieved by chromatin modifications. Recently, Runx family proteins were found to have an essential role in either

Ichiro Taniuchi; Dan R Littman

2004-01-01

31

Artificial trans-Acting siRNAs Confer Consistent and Effective Gene Silencing  

Microsoft Academic Search

Manipulating gene expression is critical to exploring gene function and a useful tool for altering commercial traits. Techniques such as hairpin-based RNA interference, virus-induced gene silencing, and artificial microRNAs take advantage of endog- enous posttranscriptional gene silencing pathways to block translation of designated transcripts. Here we present a novel gene silencing method utilizing artificial trans-acting small interfering RNAs in Arabidopsis

M. de la Luz Gutierrez-Nava; M. J. Aukerman; H. Sakai; S. V. Tingey; R. W. Williams

2008-01-01

32

Review Article: The Silence of Genes in Transgenic Plants  

Microsoft Academic Search

In genetically modified plants, the introduced transgenes are sometimes not expressed. They can be silenced. Transgenes can also cause the silencing of endogenous plant genes if they are sufficiently homologous, a phenomenon known as co-suppression. Silencing occurs transcriptionally and post-transcriptionally but silencing of endogenous genes seems predominantly post-transcriptional. If viral transgenes are introduced and silenced, the post-transcriptional process also prevents

MAIKE STAM; JOSEPH N. M MOL; JAN M KOOTER

1997-01-01

33

Posttranscriptional Gene Silencing and Translation in Giardia  

Microsoft Academic Search

\\u000a The control of gene expression in Giardia lamblia includes several mechanisms already described in higher eukaryotes, but with some interesting features for this early-branching\\u000a organism. Here we describe two gene expression control systems in Giardia, posttranscriptional gene silencing (PTGS) and translation, and the close interaction between them. For the first mechanism,\\u000a all the components were identified as being active in

Pablo R. Gargantini; César G. Prucca; Hugo D. Luján

34

Transcriptional gene silencing in plants  

Microsoft Academic Search

The review presents current data on molecular genetic mechanisms of suppression of the gene (transgene) expression in plants\\u000a at the transcriptional level. The stages of RNA-directed DNA methylation are discussed in detail. Mutations affecting transcriptional\\u000a gene inactivation without altering nucleotide sequence methylation are described.

T. V. Marenkova; E. V. Deineko

2010-01-01

35

Short hairpin activated gene silencing in mammalian cells.  

PubMed

RNA interference (RNAi) is now a popular method for silencing gene expression in a variety of systems. RNAi methods use double-stranded RNAs (dsRNAs) to target complementary RNAs for destruction. In mammalian systems, very short dsRNAs (22-25 bp) such as short interfering RNAs (siRNAs) or short hairpin RNAs (shRNAs) are used to avoid endogenous nonspecific antiviral responses that target longer dsRNAs. siRNAs elicit a transient silencing response, while shRNAs can be expressed continuously to establish stable gene silencing. shRNAs can be introduced into cells and animals using a variety of standard vectors as well as retroviral or lentiviral expression systems. This chapter describes the design, construction, validation, and use of shRNAs for silencing genes. We report our results from testing a variety of shRNA design features and shRNA expression vectors. We also provide methods that use shRNAs to permit different levels of gene expression. Additionally, we discuss some aspects important for constructing an information pipeline to support development of a large shRNA library. PMID:15103070

Paddison, Patrick J; Caudy, Amy A; Sachidanandam, Ravi; Hannon, Gregory J

2004-01-01

36

Gene silencing--a new theory of aging.  

PubMed

The aging process involves silencing of the genes through methylation of promoter sequences and the acetylation of histones. This process contributes not only to aging, but also cancer when silencing affects tumor suppressor genes. Antineoplastons work as molecular switches, turning inactive tumor suppressor genes back on through demethylation of the DNA and acetylation of the histones. While they activate tumor suppressor genes, antineoplastons also activate some additional genes silenced during the aging process. Evidence of activation of silenced genes can be pursued by documenting the relationship between 'molecular switches' - DNA-demethylating agents and histone deacetylation inhibitors, genes which are turned on by them, and clinical anti-aging changes. PMID:12615527

Burzynski, Stanislaw R

2003-04-01

37

Successive silencing of tandem reporter genes in potato (Solanum tuberosum) over 5 years of vegetative propagation  

PubMed Central

Background and Aims Transgenic plants represent an excellent tool for experimental plant biology and are an important component of modern agriculture. Fully understanding the stability of transgene expression is critical in this regard. Most changes in transgene expression occur soon after transformation and thus unwanted lines can be discarded easily; however, transgenes can be silenced long after their integration. Methods To study the long-term changes in transgene expression in potato (Solanum tuberosum), the activity of two reporter genes, encoding green fluorescent protein (GFP) and neomycin phosphotransferase (NPTII), was monitored in a set of 17 transgenic lines over 5 years of vegetative propagation in vitro. Key Results A decrease in transgene expression was observed mainly in lines with higher initial GFP expression and a greater number of T-DNA insertions. Complete silencing of the reporter genes was observed in four lines (nearly 25 %), all of which successively silenced the two reporter genes, indicating an interconnection between their silencing. The loss of GFP fluorescence always preceded the loss of kanamycin resistance. Treatment with the demethylation drug 5-azacytidine indicated that silencing of the NPTII gene, but probably not of GFP, occurred directly at the transcriptional level. Successive silencing of the two reporter genes was also reproduced in lines with reactivated expression of previously silenced transgenes. Conclusions We suggest a hypothetical mechanism involving the successive silencing of the two reporter genes that involves the switch of GFP silencing from the post-transcriptional to transcriptional level and subsequent spreading of methylation to the NPTII gene.

Nocarova, Eva; Opatrny, Zdenek; Fischer, Lukas

2010-01-01

38

Chitosanase-based method for RNA isolation from cells transfected with chitosan/siRNA nanocomplexes for real-time RT-PCR in gene silencing  

PubMed Central

Chitosan, a well known natural cationic polysaccharide, has been successfully implemented in vitro and in vivo as a nonviral delivery system for both plasmid DNA and siRNA. While using chitosan/siRNA polyplexes to knock down specific targets, we have underestimated the effect of nucleic acids binding to chitosan when extracting RNA for subsequent quantitative PCR evaluation of silencing. In vitro transfection using chitosan/siRNA-based polyplexes reveals a very poor recovery of total RNA especially when using low cell numbers in 96 well plates. Here, we describe a method that dramatically enhances RNA extraction from chitosan/siRNA-treated cells by using an enzymatic treatment with a type III chitosanase. We show that chitosanase treatment prior to RNA extraction greatly enhances the yield and the integrity of extracted RNA. This method will therefore eliminate the bias associated with lower RNA yield and integrity when quantifying gene silencing of chitosan-based systems using quantitative real time PCR.

Alameh, Mohamad; Jean, Myriam; DeJesus, Diogo; Buschmann, Michael D; Merzouki, Abderrazzak

2010-01-01

39

Evaluating the Ability of the Barley Stripe Mosaic Virus-Induced Gene Silencing System to Simultaneously Silence Two Wheat Genes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Virus-induced gene silencing (VIGS) is an important tool for rapid assessment of gene function in plants. The ability of the Barley stripe mosaic virus (BSMV) VIGS system to simultaneously silence two genes was assessed by comparing the extent of down-regulation of the wheat PDS and SGT1 genes afte...

40

Exploring plant genomes by RNA-induced gene silencing  

Microsoft Academic Search

The nucleotide sequences of several animal, plant and bacterial genomes are now known, but the functions of many of the proteins that they are predicted to encode remain unclear. RNA interference is a gene-silencing technology that is being used successfully to investigate gene function in several organisms — for example, Caenorhabditis elegans. We discuss here that RNA-induced gene silencing approaches

Christopher A. Helliwell; Peter M. Waterhouse

2003-01-01

41

Silencing of a meristematic gene using geminivirus-derived vectors.  

PubMed

Geminiviruses are DNA viruses that replicate and transcribe their genes in plant nuclei. They are ideal vectors for understanding plant gene function because of their ability to cause systemic silencing in new growth and ease of inoculation. We previously demonstrated DNA episome-mediated gene silencing from a bipartite geminivirus in Nicotiana benthamiana. Using an improved vector, we now show that extensive silencing of endogenous genes can be obtained using less than 100 bp of homologous sequence. Concomitant symptom development varied depending upon the target gene and insert size, with larger inserts producing milder symptoms. In situ hybridization of silenced tissue in attenuated infections demonstrated that silencing occurs in cells that lack detectable levels of viral DNA. A mutation confining the virus to vascular tissue produced extensive silencing in mesophyll tissue, further demonstrating that endogenous gene silencing can be separated from viral infection. We also show that two essential genes encoding a subunit of magnesium chelatase and proliferating cell nuclear antigen (PCNA) can be silenced simultaneously from different components of the same viral vector. Immunolocalization of silenced tissue showed that the PCNA protein was down-regulated throughout meristematic tissues. Our results demonstrate that geminivirus-derived vectors can be used to study genes involved in meristem function in intact plants. PMID:11532181

Peele, C; Jordan, C V; Muangsan, N; Turnage, M; Egelkrout, E; Eagle, P; Hanley-Bowdoin, L; Robertson, D

2001-08-01

42

Gene silencing by nuclear orphan receptors.  

PubMed

Nuclear orphan receptors represent a large and diverse subgroup in the nuclear receptor superfamily. Although putative ligands for these orphan members remain to be identified, some of these receptors possess intrinsic activating, inhibitory, or dual regulatory functions in development, differentiation, homeostasis, and reproduction. In particular, gene-silencing events elicited by chicken ovalbumin upstream promoter-transcription factors (COUP-TFs); dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX-1); germ cell nuclear factor (GCNF); short heterodimer partner (SHP); and testicular receptors 2 and 4 (TR2 and TR4) are among the best characterized. These orphan receptors are critical in controlling basal activities or hormonal responsiveness of numerous target genes. They employ multiple and distinct mechanisms to mediate target gene repression. Complex cross-talk exists between these orphan receptors at their cognate DNA binding elements and an array of steroid?nonsteroid hormone receptors, other transcriptional activators, coactivators and corepressors, histone modification enzyme complexes, and components of basal transcriptional components. Therefore, perturbation induced by these orphan receptors at multiple levels, including DNA binding activities, receptor homo- or heterodimerization, recruitment of cofactor proteins, communication with general transcriptional machinery, and changes at histone acetylation status and chromatin structures, may contribute to silencing of target gene expression in a specific promoter or cell-type context. Moreover, the findings derived from gene-targeting studies have demonstrated the significance of these orphan receptors' function in physiologic settings. Thus, COUP-TFs, DAX-1, GCNF, SHP, and TR2 and 4 are known to be required for multiple physiologic and biologic functions, including neurogenesis and development of the heart and vascular system steroidogenesis and sex determination, gametogenesis and embryonic development, and cholesterol?lipid homeostasis. PMID:15193450

Zhang, Ying; Dufau, Maria L

2004-01-01

43

Initiation and Maintenance of Virus-Induced Gene Silencing  

Microsoft Academic Search

The phytoene desaturase (PDS) gene of Nicotiana benthamiana was silenced in plants infected with potato virus X (PVX) vectors carrying PDS inserts, and a green fluorescent protein (GFP) transgene was silenced in plants infected with PVX-GFP. This virus-induced gene silencing (VIGS) is post-transcriptional and cytoplasmic because it is targeted against exons rather than introns of PDS RNA and against viral

M. Teresa Ruiz; Olivier Voinnet; David C. Baulcombe

1998-01-01

44

A Viral Suppressor of Gene Silencing in Plants  

Microsoft Academic Search

Gene silencing is an important but little understood regulatory mechanism in plants. Here we report that a viral sequence, initially identified as a mediator of synergistic viral disease, acts to suppress the establishment of both transgene-induced and virus-induced posttranscriptional gene silencing. The viral suppressor of silencing comprises the 5'-proximal region of the tobacco etch potyviral genomic RNA encoding P1, helper

Radhamani Anandalakshmi; Gail J. Pruss; Xin Ge; Rajendra Marathe; Allison C. Mallory; Trenton H. Smith; Vicki B. Vance

1998-01-01

45

Gene silencing in potato: allelic differences and effect of ploidy  

Microsoft Academic Search

Silencing of genes is mostly studied in diploid, homozygous, self-fertile and sexually propagated species. However, conclusions drawn for these species are not always applicable to crops like potato, which is an autotetraploid, highly heterozygous, vegetatively propagated species. Factors influencing the level of silencing in potato are discussed, with emphasis on inhibition of the granule-bound starch synthase I (GBSSI) gene. Type

Anne-Marie A. Wolters; Richard G. F. Visser

2000-01-01

46

Gene silencing from plant DNA carried by a Geminivirus  

Microsoft Academic Search

Summary The geminivirus tomato golden mosaic virus (TGMV) replicates in nuclei and expresses genes from high copy number DNA episomes. The authors used TGMV as a vector to determine whether episomal DNA can cause silencing of homologous, chromosomal genes. Two markers were used to assess silencing: (1) the sulfur allele (su) of magnesium chelatase, an enzyme required for chlorophyll formation;

Susanne Kjemtrup; Kim S. Sampson; Charles G. Peele; Long V. Nguyen; Mark A. Conkling; William F. Thompson; Dominique Robertson

1998-01-01

47

Paired termini stabilize antisense RNAs and enhance conditional gene silencing in Escherichia coli  

Microsoft Academic Search

Reliable methods for conditional gene silencing in bacteria have been elusive. To improve silencing by expressed antisense RNAs (asRNAs), we syste- matically altered several design parameters and targeted multiple reporter and essential genes in Escherichia coli. A paired termini (PT) design, where flanking inverted repeats create paired dsRNA termini, proved effective. PTasRNAs tar- geted against the ackA gene within the

Nobutaka Nakashima; Tomohiro Tamura; L. Good

2006-01-01

48

Virus-induced multiple gene silencing to study redundant metabolic pathways in plants: silencing the starch degradation pathway in Nicotiana benthamiana.  

PubMed

Virus-induced gene silencing (VIGS) is a rapid technique that allows for specific and reproducible post-transcriptional degradation of targeted mRNA. The method has been proven efficient for suppression of expression of many single enzymes. The metabolic networks of plants, however, often contain isoenzymes and gene families that are able to compensate for a mutation and mask the development of a silencing phenotype. Here, we show the application of multiple gene VIGS repression for the study of these redundant biological pathways. Several genes in the starch degradation pathway [disproportionating enzyme 1; (DPE1), disproportionating enzyme 2 (DPE2), and GWD] were silenced. The functionally distinct DPE enzymes are present in alternate routes for sugar export to the cytoplasm and result in an increase in starch production when silenced individually. Simultaneous silencing of DPE1 and DPE2 in Nicotiana benthamiana resulted in a near complete suppression in starch and accumulation of malto-oligosaccharides. PMID:22345045

George, Gavin M; Bauer, Rolene; Blennow, Andreas; Kossmann, Jens; Lloyd, James R

2012-03-07

49

Transgenic gene silencing strategies for virus control  

Microsoft Academic Search

Co-suppression of transgenes and their homologous viral sequences by RNA silencing is a powerful strategy for achieving high-level\\u000a virus resistance in plants. This review provides a brief overview of RNA silencing mechanisms in plants and discusses important\\u000a transgene construct design features underpinning successful RNA silencing-mediated transgenic virus control. Application of\\u000a those strategies to protect horticultural and field crops from virus

R. G. Dietzgen; N. Mitter

2006-01-01

50

Homoeologous gene silencing in tissue cultured wheat callus  

Microsoft Academic Search

BACKGROUND: In contrast to diploids, most polyploid plant species, which include the hexaploid bread wheat, possess an additional layer of epigenetic complexity. Several studies have demonstrated that polyploids are affected by homoeologous gene silencing, a process in which sub-genomic genomic copies are selectively transcriptionally inactivated. This form of silencing can be tissue specific and may be linked to developmental or

Andrew Bottley; Natalie H Chapman

2008-01-01

51

Novel RNA-based Strategies for Therapeutic Gene Silencing  

Microsoft Academic Search

The past decade has seen intense scientific interest in non-coding RNAs. In particular, the discovery and subsequent exploitation of gene silencing via RNA interference (RNAi) has revolutionized the way in which gene expression is now studied and understood. It is now well established that post-transcriptional gene silencing (PTGS) by the microRNA (miRNA) and other RNAi-associated pathways represents an essential layer

Christopher R Sibley; Yiqi Seow; Matthew JA Wood

2010-01-01

52

Novel sexual-cycle-specific gene silencing in Aspergillus nidulans.  

PubMed

We report a novel sexual-cycle-specific gene-silencing system in the genetic model Aspergillus nidulans. Duplication of the mating type matA(HMG) gene in this haploid organism triggers Mat-induced silencing (MatIS) of both endogenous and transgenic matA genes, eliminates function of the encoded SRY structural ortholog, and results in formation of barren fruiting bodies. MatIS is spatiotemporally restricted to the prezygotic stage of the sexual cycle and does not interfere with vegetative growth, asexual reproduction, differentiation of early sexual tissues, or fruiting body development. MatIS is reversible upon deletion of the matA transgene. In contrast to other sex-specific silencing phenomena, MatIS silencing has nearly 100% efficiency and appears to be independent of homologous duplicated DNA segments. Remarkably, transgene-derived matA RNA might be sufficient to induce MatIS. A unique feature of MatIS is that RNA-mediated silencing is RNA interference/Argonaute-independent and is restricted to the nucleus having the duplicated gene. The silencing phenomenon is recessive and does not spread between nuclei within the common cytoplasm of a multinucleate heterokaryon. Gene silencing induced by matA gene duplication emerges as a specific feature associated with matA(HMG) regulation during sexual development. PMID:23341415

Czaja, Wioletta; Miller, Karen Y; Miller, Bruce L

2013-01-22

53

Selective gene silencing by viral delivery of short hairpin RNA  

PubMed Central

RNA interference (RNAi) technology has not only become a powerful tool for functional genomics, but also allows rapid drug target discovery and in vitro validation of these targets in cell culture. Furthermore, RNAi represents a promising novel therapeutic option for treating human diseases, in particular cancer. Selective gene silencing by RNAi can be achieved essentially by two nucleic acid based methods: i) cytoplasmic delivery of short double-stranded (ds) interfering RNA oligonucleotides (siRNA), where the gene silencing effect is only transient in nature, and possibly not suitable for all applications; or ii) nuclear delivery of gene expression cassettes that express short hairpin RNA (shRNA), which are processed like endogenous interfering RNA and lead to stable gene down-regulation. Both processes involve the use of nucleic acid based drugs, which are highly charged and do not cross cell membranes by free diffusion. Therefore, in vivo delivery of RNAi therapeutics must use technology that enables the RNAi therapeutic to traverse biological membrane barriers in vivo. Viruses and the vectors derived from them carry out precisely this task and have become a major delivery system for shRNA. Here, we summarize and compare different currently used viral delivery systems, give examples of in vivo applications, and indicate trends for new developments, such as replicating viruses for shRNA delivery to cancer cells.

2010-01-01

54

Listening to the silent genes: transgene silencing, gene regulation and pathogen control  

Microsoft Academic Search

By capitalizing on the initially puzzling observations of unpredictable transgene silencing and variable expression, plant scientists have pioneered research into a novel type of epigenetic regulation, termed homology-dependent gene silencing. This silencing process has implications for natural mechanisms of gene expression in plants and other eukaryotes, and has branched out into studies of reversible DNA modifications; RNA metabolism, transport and

Jan M. Kooter; Marjori A. Matzke; Peter Meyer

1999-01-01

55

Structure and Gene-Silencing Mechanisms of Small Noncoding RNAs  

Microsoft Academic Search

Small (19–31-nucleotides) noncoding RNAs were identified in the past 10 years for their distinct function in gene silencing.\\u000a The best known gene-silencing phenomenon, RNA interference (RNAi), is triggered in a sequence-specific manner by endogenously\\u000a produced or exogenously introduced small doubled-stranded RNAs. As knowledge of the structure and function of the RNAi machinery\\u000a has expanded, this phenomenon has become a powerful

Chia-Ying Chu; Tariq M. Rana

2009-01-01

56

Gene expression: Total silencing by intron-spliced hairpin RNAs  

Microsoft Academic Search

Post-transcriptional gene silencing (PTGS), a sequence-specific RNA degradation mechanism inherent in many life-forms, can be induced in plants by transforming them with either antisense or co-suppression constructs, but typically this results in only a small proportion of silenced individuals. Here we show that gene constructs encoding intron-spliced RNA with a hairpin structure can induce PTGS with almost 100% efficiency when

Neil A. Smith; Surinder P. Singh; Ming-Bo Wang; Peter A. Stoutjesdijk; Allan G. Green; Peter M. Waterhouse

2000-01-01

57

Induction of Gene Silencing by Hairpin RNA Expression in Tetrahymena thermophila Reveals a Second Small RNA Pathway  

Microsoft Academic Search

Unlike in other eukaryotes, in which it causes gene silencing, RNA interference (RNAi) has been linked to programmed DNA deletion in the ciliate Tetrahymena thermophila. Here we have developed an efficient method to inducibly express double-stranded RNA hairpins and demonstrated that they cause gene silencing through targeted mRNA degradation in all phases of the life cycle, including growth, starvation, and

Rachel A. Howard-Till; Meng-Chao Yao

2006-01-01

58

Co-silencing the mirabilis antiviral protein permits virus-induced gene silencing in Mirabilis jalapa  

Technology Transfer Automated Retrieval System (TEKTRAN)

Virus-induced gene silencing (VIGS) is an attractive and rapid technique for loss of function assay that can reveal the phenotype of embryo-lethal sequences and avoids the need for time consuming transformation and regeneration processes. Among various VIGS vectors that have been explored, the tobac...

59

733. The Human XIST Gene Promoter Prevents Silencing of an Integrated Reporter Gene  

Microsoft Academic Search

Epigenetic silencing and position dependent expression are long-standing problems which continue to limit the development of gene replacement therapy. As a strategy to overcome this problem we have tested the ability of the human XIST (X inactivation-specific transcript) gene promoter to overcome epigenetic silencing. The XIST gene is one of a relatively small cohort of genes which are expressed from

Michael R. Greene; Christopher H. Lowrey

2005-01-01

60

Polymeric Nanoparticles for siRNA Delivery and Gene Silencing  

PubMed Central

Gene silencing using small interfering RNA (siRNA) has several potential therapeutic applications. In the present study, we investigated nanoparticles formulated using the biodegradable polymer, poly(d,l-lactide-co-glycolide) (PLGA) for siRNA delivery. A cationic polymer, polyethylenimine (PEI), was incorporated in the PLGA matrix to improve siRNA encapsulation in PLGA nanoparticles. PLGA-PEI nanoparticles were formulated using double emulsion-solvent evaporation technique and characterized for siRNA encapsulation and in vitro release. The effectiveness of siRNA-loaded PLGA-PEI nanoparticles in silencing a model gene, fire fly luciferase, was investigated in cell culture. Presence of PEI in PLGA nanoparticle matrix increased siRNA encapsulation by about 2-fold and also improved the siRNA release profile. PLGA-PEI nanoparticles carrying luciferase-targeted siRNA enabled effective silencing of the gene in cells stably expressing luciferase as well as in cells that could be induced to overexpress the gene. Quantitative studies indicated that presence of PEI in PLGA nanoparticles resulted in 2-fold higher cellular uptake of nanoparticles while fluorescence microscopy studies showed that PLGA-PEI nanoparticles delivered the encapsulated siRNA in the cellular cytoplasm; both higher uptake and greater cytosolic delivery could have contributed to the gene silencing effectiveness of PLGA-PEI nanoparticles. Serum stability and lack of cytotoxicity further add to the potential of PLGA-PEI nanoparticles in gene silencing-based therapeutic applications.

Patil, Yogesh; Panyam, Jayanth

2009-01-01

61

Detailed characterization of the posttranscriptional gene-silencing-related small RNA in a GUS gene-silenced tobacco.  

PubMed Central

Posttranscriptional gene-silencing phenomena such as cosuppression and RNA interference are associated with the occurrence of small, about 21-23 nt short RNA species homologous to the silenced gene. We here show that the small RNA present in silenced transgenic plants can easily be detected in total RNA isolated according to standard procedures. This will allow for the development of routine and early screenings for the presence of small RNA species and, therefore, gene silencing in transgenic plants. We further demonstrate that the small RNA fraction can be visualized with the SYBR Green II RNA stain, isolated from a gel, labeled and used as a specific probe. Using these approaches, we have fine-mapped the sequences of the GUS gene that are represented in the small RNA fraction of a GUS-silenced tobacco line containing an inverted repeat of the GUS gene. In this tobacco line, the silencing-associated small RNA is a mixture of fragments that cover the 3' two-thirds of the GUS coding region. The 5' coding and the 3' noncoding ends of the GUS mRNA are not represented in the small RNA fraction. The RNA fragments are not likely to be a primary synthesis product of an RNA-dependent RNA polymerase, but rather degradation products from nuclease activity. Surprisingly, RNA isolated from wild-type, untransformed plants showed the presence of a similar-sized small RNA pool. This might indicate the existence of small RNA species from putative endogenous genes that are down regulated by a similar posttranscriptional gene-silencing mechanism. The possibility of isolating and labeling the small RNA pool from wild-type plants will provide a way to identify and study such putative genes.

Hutvagner, G; Mlynarova, L; Nap, J P

2000-01-01

62

MORC family ATPases required for heterochromatin condensation and gene silencing.  

PubMed

Transposable elements (TEs) and DNA repeats are commonly targeted by DNA and histone methylation to achieve epigenetic gene silencing. We isolated mutations in two Arabidopsis genes, AtMORC1 and AtMORC6, which cause derepression of DNA-methylated genes and TEs but no losses of DNA or histone methylation. AtMORC1 and AtMORC6 are members of the conserved Microrchidia (MORC) adenosine triphosphatase (ATPase) family, which are predicted to catalyze alterations in chromosome superstructure. The atmorc1 and atmorc6 mutants show decondensation of pericentromeric heterochromatin, increased interaction of pericentromeric regions with the rest of the genome, and transcriptional defects that are largely restricted to loci residing in pericentromeric regions. Knockdown of the single MORC homolog in Caenorhabditis elegans also impairs transgene silencing. We propose that the MORC ATPases are conserved regulators of gene silencing in eukaryotes. PMID:22555433

Moissiard, Guillaume; Cokus, Shawn J; Cary, Joshua; Feng, Suhua; Billi, Allison C; Stroud, Hume; Husmann, Dylan; Zhan, Ye; Lajoie, Bryan R; McCord, Rachel Patton; Hale, Christopher J; Feng, Wei; Michaels, Scott D; Frand, Alison R; Pellegrini, Matteo; Dekker, Job; Kim, John K; Jacobsen, Steven E

2012-05-03

63

Therapeutic gene silencing in neurological disorders, using interfering RNA  

Microsoft Academic Search

The development of interfering RNA (RNAi) from a naturally occurring phenomenon to a tool for mediating highly specific gene silencing provides an exciting prospect as a novel therapeutic strategy for a wide range of disorders. Although the efficacy of RNAi as a research tool for analysing gene function has been well demonstrated in several cell types, the therapeutic potential of

G. Scott Ralph; Nicholas D. Mazarakis; Mimoun Azzouz

2005-01-01

64

Silence of the genes — mechanisms of long-term repression  

Microsoft Academic Search

A large fraction of genes in the mammalian genome is repressed in every cell throughout development. Here, we propose that this long-term silencing is carried out by distinct molecular mechanisms that operate in a global manner and, once established, can be maintained autonomously through DNA replication. Both individually and in combination these mechanisms bring about repression, mainly by lowering gene

Laura Lande-Diner; Howard Cedar

2005-01-01

65

RNAi-Based Gene Silencing in Chicken Brain Development.  

PubMed

The mouse is the most commonly used vertebrate model for the analysis of gene function because of the well-established genetic tools that are available for loss-of-function studies. However, studies of gene function during development can be problematic in mammals. Many genes are active during different stages of development. Absence of gene function during early development may cause embryonic lethality and thus prevent analysis of later stages of development. To avoid these problems, precise temporal control of gene silencing is required.In contrast to mammals, oviparous animals are accessible for experimental manipulations during embryonic development. The combination of accessibility and RNAi-based gene silencing makes the chicken embryo a powerful model for developmental studies. Depending on the time window during which gene silencing is attempted, chicken embryos can be used for RNAi in ovo or cultured in a domed dish for easier access during ex ovo RNAi. Both techniques allow for precise temporal control of gene silencing during embryonic development. PMID:24048939

Andermatt, Irwin; Stoeckli, Esther T

2014-01-01

66

Silencers  

NASA Astrophysics Data System (ADS)

Large size silencers are attached to the intake and exhaust of large industrial plants, e.g. forced ventilation systems for mining industry, intake of cooling towers (Fig. 11.1) or flue gas stacks of power plants to protect the neighbourhood from plant noise. Large silencers are also required for ventilation openings of rooms with high internal sound pressure levels, e.g. industrial production halls or subway ventilation ducts.

Kurze, U.; Riedel, E.

67

Optimization of virus-induced gene silencing in pepper (Capsicum annuum L.).  

PubMed

Virus-induced gene silencing is currently a powerful tool for the study of gene function in plants. Here, we optimized the protocol for virus-induced gene silencing, and investigated factors that affect the efficiency of tobacco rattle virus-induced gene silencing in pepper plants. Consequently, an optimal protocol was obtained by the syringe-infiltration method in the leaves of pepper plants. The protocol involves 2-leaf stage plants, preparing the Agrobacterium inoculum at a final OD600 of 1.0 and then growing the inoculated plants at 22°C. Using this protocol, we achieved high efficiency in silencing CaPDS in different cultivars of pepper plants. We further used the CaPOD gene to illustrate the general reliability of this optimized protocol. Viral symptoms were observed on the leaves of inoculated plants of the Early Calwonder cultivar 25 days post-inoculation, indicating that this protocol can also be used to silence other genes in pepper plants. Real-time polymerase chain reaction analyses revealed that the expression levels of CaPDS and CaPOD were dramatically reduced in inoculated leaves compared to control plants. These results demonstrate that the optimized protocol can be applied to functional genomic studies in pepper to investigate genes involved in a wide range of biological processes. PMID:23979884

Wang, J-E; Li, D-W; Gong, Z-H; Zhang, Y-L

2013-07-24

68

Development of Agrobacterium-Mediated Virus-Induced Gene Silencing and Performance Evaluation of Four Marker Genes in Gossypium barbadense.  

PubMed

Gossypiumbarbadense is a cultivated cotton species and possesses many desirable traits, including high fiber quality and resistance to pathogens, especially Verticilliumdahliae (a devastating pathogen of Gossypium hirsutum, the main cultivated species). These elite traits are difficult to be introduced into G. hirsutum through classical breeding methods. In addition, genetic transformation of G. barbadense has not been successfully performed. It is therefore important to develop methods for evaluating the function and molecular mechanism of genes in G. barbadense. In this study, we had successfully introduced a virus-induced gene silencing (VIGS) system into three cultivars of G. barbadense by inserting marker genes into the tobacco rattle virus (TRV) vector. After we optimized the VIGS conditions, including light intensity, photoperiod, seedling age and Agrobacterium strain, 100% of plants agroinfiltrated with the GaPDS silencing vector showed white colored leaves. Three other marker genes, GaCLA1, GaANS and GaANR, were employed to further test this VIGS system in G. barbadense. The transcript levels of the endogenous genes in the silenced plants were reduced by more than 99% compared to control plants; these plants presented phenotypic symptoms 2 weeks after inoculation. We introduced a fusing sequence fragment of GaPDS and GaANR gene silencing vectors into a single plant, which resulted in both photobleaching and brownish coloration. The extent of silencing in plants agroinfiltrated with fusing two-gene-silencing vector was consistent with plants harboring a single gene silencing vector. The development of this VIGS system should promote analysis of gene function in G. barbadense, and help to contribute desirable traits for breeding of G. barbadense and G. hirsutum. PMID:24023833

Pang, Jinhuan; Zhu, Yue; Li, Qing; Liu, Jinzhi; Tian, Yingchuan; Liu, Yule; Wu, Jiahe

2013-09-02

69

Efficient gene silencing by expression of double stranded RNA in Neurospora crassa  

Microsoft Academic Search

In Neurospora crassa, sequence-specific inhibition of endogenous genes can be induced by the introduction of transgenic DNA homologous to the target gene, through the mechanism of post-transcriptional gene silencing (PTGS) known as quelling. The appli- cation of this strategy to inactivate genes in N. crassa has, to date, been restricted by a limited silencing efficiency and instability of the silenced

Marina Goldoni; Gianluca Azzalin; Giuseppe Macino; Carlo Cogoni

2004-01-01

70

Silencing and Un-silencing of Tetracycline-Controlled Genes in Neurons  

Microsoft Academic Search

To identify the underlying reason for the controversial performance of tetracycline (Tet)-controlled regulated gene expression in mammalian neurons, we investigated each of the three components that comprise the Tet inducible systems, namely tetracyclines as inducers, tetracycline-transactivator (tTA) and reverse tTA (rtTA), and tTA-responsive promoters (Ptets). We have discovered that stably integrated Ptet becomes functionally silenced in the majority of neurons

Peixin Zhu; M. Isabel Aller; Udo Baron; Sidney Cambridge; Melanie Bausen; Jan Herb; Jürgen Sawinski; Ali Cetin; Pavel Osten; Mark L. Nelson; Sebastian Kügler; Peter H. Seeburg; Rolf Sprengel; Mazahir T. Hasan; Peter Fraser

2007-01-01

71

Gene socialization: gene order, GC content and gene silencing in Salmonella  

Microsoft Academic Search

BACKGROUND: Genes of conserved order in bacterial genomes tend to evolve slower than genes whose order is not conserved. In addition, genes with a GC content lower than the GC content of the resident genome are known to be selectively silenced by the histone-like nucleoid structuring protein (H-NS) in Salmonella. RESULTS: In this study, we use a comparative genomics approach

Nikolas Papanikolaou; Kalliopi Trachana; Theodosios Theodosiou; Vasilis J Promponas; Ioannis Iliopoulos

2009-01-01

72

Gene silencing as an adaptive defence against viruses  

Microsoft Academic Search

Gene silencing was perceived initially as an unpredictable and inconvenient side effect of introducing transgenes into plants. It now seems that it is the consequence of accidentally triggering the plant's adaptive defence mechanism against viruses and transposable elements. This recently discovered mechanism, although mechanistically different, has a number of parallels with the immune system of mammals.

Peter M. Waterhouse; Ming-Bo Wang; Tony Lough

2001-01-01

73

The Development and Application of a Multiple Gene Co-Silencing System Using Endogenous URA3 as a Reporter Gene in Ganoderma lucidum  

PubMed Central

Ganoderma lucidum is one of the most important medicinal mushrooms; however, molecular genetics research on this species has been limited due to a lack of reliable reverse genetic tools. In this study, the endogenous orotidine 5?-monophosphate decarboxylase gene (URA3) was cloned as a silencing reporter, and four gene-silencing methods using hairpin, sense, antisense, and dual promoter constructs, were introduced into G. lucidum through a simple electroporation procedure. A comparison and evaluation of silencing efficiency demonstrated that all of the four methods differentially suppressed the expression of URA3. Our data unequivocally indicate that the dual promoter silencing vector yields the highest rate of URA3 silencing compared with other vectors (up to 81.9%). To highlight the advantages of the dual promoter system, we constructed a co-silencing system based on the dual promoter method and succeeded in co-silencing URA3 and laccase in G. lucidum. The reduction of the mRNA levels of the two genes were correlated. Thus, the screening efficiency for RNAi knockdown of multiple genes may be improved by the co-silencing of an endogenous reporter gene. The molecular tools developed in this study should facilitate the isolation of genes and the characterization of the functions of multiple genes in this pharmaceutically important species, and these tools should be highly useful for the study of other basidiomycetes.

Mu, Dashuai; Shi, Liang; Ren, Ang; Li, Mengjiao; Wu, Fengli; Jiang, Ailiang; Zhao, Mingwen

2012-01-01

74

RNA-Mediated Gene Silencing in Hematopoietic Cells  

PubMed Central

In the past few years, the discovery of RNA-mediated gene silencing mechanisms, like RNA interference (RNAi), has revolutionized our understanding of eukaryotic gene expression. These mechanisms are activated by double-stranded RNA (dsRNA) and mediate gene silencing either by inducing the sequence-specific degradation of complementary mRNA or by inhibiting mRNA translation. RNAi now provides a powerful experimental tool to elucidate gene function in vitro and in vivo, thereby opening new exciting perspectives in the fields of molecular analysis and eventually therapy of several diseases such as infections and cancer. In hematology, numerous studies have described the successful application of RNAi to better define the role of oncogenic fusion proteins in leukemogenesis and to explore therapeutic approaches in hematological malignancies. In this review, we highlight recent advances and caveats relating to the application of this powerful new methodology to hematopoiesis.

Venturini, Letizia; Eder, Matthias; Scherr, Michaela

2006-01-01

75

RNA-mediated gene silencing in the cereal fungal pathogen Cochliobolus sativus.  

PubMed

A high-throughput RNA-mediated gene silencing system was developed for Cochliobolus sativus (anamorph: Bipolaris sorokiniana), the causal agent of spot blotch, common root rot and black point in barley and wheat. The green fluorescent protein gene (GFP) and the proteinaceous host-selective toxin gene (ToxA) were first introduced into C. sativus via the polyethylene glycol (PEG)-mediated transformation method. Transformants with a high level of expression of GFP or ToxA were generated. A silencing vector (pSGate1) based on the Gateway cloning system was developed and used to construct RNA interference (RNAi) vectors. Silencing of GFP and ToxA in the transformants was demonstrated by transformation with the RNAi construct expressing hairpin RNA (hpRNA) of the target gene. The polyketide synthase gene (CsPKS1), involved in melanin biosynthesis pathways in C. sativus, was also targeted by transformation with the RNAi vector (pSGate1-CsPKS1) encoding hpRNA of the CsPKS1 gene. The transformants with pSGate1-CsPKS1 exhibited an albino phenotype or reduced melanization, suggesting effective silencing of the endogenous CsPKS1 in C. sativus. Sectors exhibiting the wild-type phenotype of the fungus appeared in some of the CsPKS1-silenced transformants after subcultures as a result of inactivation or deletions of the RNAi transgene. The gene silencing system established provides a useful tool for functional genomics studies in C. sativus and other filamentous fungi. PMID:21356000

Leng, Yueqiang; Wu, Chengxiang; Liu, Zhaohui; Friesen, Timothy L; Rasmussen, Jack B; Zhong, Shaobin

2010-10-01

76

RNAi gene silencing affects cell and developmental plasticity in hydra  

Microsoft Academic Search

The recent establishment of gene silencing through RNA interference upon feeding opens avenues to decipher the genetic control of regeneration in hydra. Following that approach, we identified three main stages for head regeneration. Immediately post-amputation, the serine protease inhibitor Kazal1 gene produced by the gland cells prevents from an excessive autophagy in regenerating tips. This cytoprotective function, or self-preservation, is

Brigitte Galliot; Marijana Miljkovic-Licina; Luiza Ghila; Simona Chera

2007-01-01

77

Optimization of Agrobacterium -mediated transient gene expression and endogenous gene silencing in Piper colubrinum Link. by vacuum infiltration  

Microsoft Academic Search

The present study describes the successful development of vacuum infiltration method in the oomycete-resistant wild Piper sp., Piper colubrinum, as a rapid transient method for expression of GUS (?-Glucuronidase) reporter gene and introduction of hairpin vector for endogenous gene silencing. The GUS reporter gene construct pCAMBIA 1305.2 was used as a positive control to test the efficiency of vacuum infiltration

Tomson ManiS; S. Manjula

2011-01-01

78

MicroRNA-directed transcriptional gene silencing in mammalian cells  

PubMed Central

MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional level in the cytoplasm, but recent findings suggest additional roles for miRNAs in the nucleus. To address whether miRNAs might transcriptionally silence gene expression, we searched for miRNA target sites proximal to known gene transcription start sites in the human genome. One conserved miRNA, miR-320, is encoded within the promoter region of the cell cycle gene POLR3D in the antisense orientation. We provide evidence of a cis-regulatory role for miR-320 in transcriptional silencing of POLR3D expression. miR-320 directs the association of RNA interference (RNAi) protein Argonaute-1 (AGO1), Polycomb group (PcG) component EZH2, and tri-methyl histone H3 lysine 27 (H3K27me3) with the POLR3D promoter. Our results suggest the existence of an epigenetic mechanism of miRNA-directed transcriptional gene silencing (TGS) in mammalian cells.

Kim, Daniel H.; Saetrom, Pal; Sn?ve, Ola; Rossi, John J.

2008-01-01

79

Polycomb target genes are silenced in multiple myeloma.  

PubMed

Multiple myeloma (MM) is a genetically heterogeneous disease, which to date remains fatal. Finding a common mechanism for initiation and progression of MM continues to be challenging. By means of integrative genomics, we identified an underexpressed gene signature in MM patient cells compared to normal counterpart plasma cells. This profile was enriched for previously defined H3K27-tri-methylated genes, targets of the Polycomb group (PcG) proteins in human embryonic fibroblasts. Additionally, the silenced gene signature was more pronounced in ISS stage III MM compared to stage I and II. Using chromatin immunoprecipitation (ChIP) assay on purified CD138+ cells from four MM patients and on two MM cell lines, we found enrichment of H3K27me3 at genes selected from the profile. As the data implied that the Polycomb-targeted gene profile would be highly relevant for pharmacological treatment of MM, we used two compounds to chemically revert the H3K27-tri-methylation mediated gene silencing. The S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin (DZNep) and the histone deacetylase inhibitor LBH589 (Panobinostat), reactivated the expression of genes repressed by H3K27me3, depleted cells from the PRC2 component EZH2 and induced apoptosis in human MM cell lines. In the immunocompetent 5T33MM in vivo model for MM, treatment with LBH589 resulted in gene upregulation, reduced tumor load and increased overall survival. Taken together, our results reveal a common gene signature in MM, mediated by gene silencing via the Polycomb repressor complex. The importance of the underexpressed gene profile in MM tumor initiation and progression should be subjected to further studies. PMID:20634887

Kalushkova, Antonia; Fryknäs, Mårten; Lemaire, Miguel; Fristedt, Charlotte; Agarwal, Prasoon; Eriksson, Maria; Deleu, Sarah; Atadja, Peter; Osterborg, Anders; Nilsson, Kenneth; Vanderkerken, Karin; Oberg, Fredrik; Jernberg-Wiklund, Helena

2010-07-09

80

Inducible RNA interference-mediated gene silencing using nanostructured gene delivery arrays.  

PubMed

RNA interference (RNAi) has become a powerful biological tool over the past decade. In this study, a tetracycline-inducible small hairpin RNA (shRNA) vector system was designed for silencing cyan fluorescent protein (CFP) expression and delivered alongside the yfp marker gene into Chinese hamster ovary cells using impalefection on spatially indexed vertically aligned carbon nanofiber arrays (VACNFs). The VACNF architecture provided simultaneous delivery of multiple genes, subsequent adherence and proliferation of interfaced cells, and repeated monitoring of single cells over time. Following impalefection and tetracycline induction, 53.1% +/- 10.4% of impalefected cells were fully silenced by the inducible CFP-silencing shRNA vector. Additionally, efficient CFP silencing was observed in single cells among a population of cells that remained CFP-expressing. This effective transient expression system enables rapid analysis of gene-silencing effects using RNAi in single cells and cell populations. PMID:19206549

Mann, David G J; McKnight, Timothy E; McPherson, Jackson T; Hoyt, Peter R; Melechko, Anatoli V; Simpson, Michael L; Sayler, Gary S

2008-01-01

81

eIF4GI Facilitates the MicroRNA-Mediated Gene Silencing  

PubMed Central

MicroRNAs (miRNAs) are small noncoding RNAs that mediate post-transcriptional gene silencing by binding to complementary target mRNAs and recruiting the miRNA-containing ribonucleoprotein complexes to the mRNAs. However, the molecular basis of this silencing is unclear. Here, we show that human Ago2 associates with the cap-binding protein complex and this association is mediated by human eIF4GI, a scaffold protein required for the translation initiation. Using a cap photo-crosslinking method, we show that Ago2 closely associates with the cap structure. Taken together, these data suggest that eIF4GI participates in the miRNA-mediated post-transcriptional gene silencing by promoting the association of Ago2 with the cap-binding complex.

Ryu, Incheol; Park, Ji Hoon; An, Sihyeon; Kwon, Oh Sung; Jang, Sung Key

2013-01-01

82

REST: A mammalian silencer protein that restricts sodium channel gene expression to neurons  

Microsoft Academic Search

Expression of the type II voltage-dependent sodium channel gene is restricted to neurons by a silencer element active in nonneuronal cells. We have cloned cDNA coding for a transcription factor (REST) that binds to this silencer element. Expression of a recombinant REST protein confers the ability to silence type II reporter genes in neuronal cell types lacking the native REST

Jayhong A Chong; José Tapia-Ramirez; Sandra Kim; Juan J Toledo-Aral; Yingcong Zheng; Michael C Boutros; Yelena M Altshuller; Michael A Frohman; Susan D Kraner; Gail Mandel

1995-01-01

83

Internuclear gene silencing in Phytophthora infestans is established through chromatin remodelling  

Microsoft Academic Search

In the plant pathogen Phytophthora infestans, nuclear integration of inf1 transgenic DNA sequences results in internuclear gene silencing of inf1. Although silencing is regulated at the transcriptional level, it also affects transcription from other nuclei within heterokaryotic cells of the mycelium. Here we report experiments exploring the mechanism of internuclear gene silencing in P. infestans. The DNA methylation inhibitor 5-azacytidine

Pieter van West; Samantha J. Shepherd; Claire A. Walker; Shuang Li; Alex A. Appiah; Laura J. Grenville-Briggs; Francine Govers; Neil A. R. Gow

2008-01-01

84

Analysis of developmental control genes using virus-induced gene silencing.  

PubMed

A consistent challenge in studying the evolution of developmental processes has been the problem of explicitly assessing the function of developmental control genes in diverse species. In recent years, virus-induced gene silencing (VIGS) has proved to be remarkably adaptable and efficient in silencing developmental control genes in species across the angiosperms. Here we describe proven protocols for Nicotiana benthamiana and Papaver somniferum, representing a core and basal eudicot species. PMID:23386295

Geuten, Koen; Viaene, Tom; Vekemans, Dries; Kourmpetli, Sofia; Drea, Sinead

2013-01-01

85

Silver nanoscale antisense drug delivery system for photoactivated gene silencing.  

PubMed

The unique photophysical properties of noble metal nanoparticles contribute to their potential as photoactivated drug delivery vectors. Here we demonstrate the synthesis and characterization of 60-80 nm silver nanoparticles (SNPs) decorated with thiol-terminated photolabile DNA oligonucleotides. In vitro assays and fluorescent confocal microscopy of treated cell cultures show efficient UV-wavelength photoactivation of surface-tethered caged ISIS2302 antisense oligonucleotides possessing internal photocleavable linkers. As a demonstration of the advantages of these novel nanocarriers, we investigate properties including: enhanced stability to nucleases, increased hybridization activity upon photorelease, and efficient cellular uptake as compared to commercial transfection vectors. Their potential as multicomponent delivery agents for oligonucleotide therapeutics is shown through regulation of ICAM-1 (Intracellular Adhesion Molecule-1) silencing. Our results suggest a means to achieve light-triggered, spatiotemporally controlled gene silencing via nontoxic silver nanocarriers, which hold promise as tailorable platforms for nanomedicine, gene expression studies, and genetic therapies. PMID:23473419

Brown, Paige K; Qureshi, Ammar T; Moll, Alyson N; Hayes, Daniel J; Monroe, W Todd

2013-03-25

86

Paired termini stabilize antisense RNAs and enhance conditional gene silencing in Escherichia coli.  

PubMed

Reliable methods for conditional gene silencing in bacteria have been elusive. To improve silencing by expressed antisense RNAs (asRNAs), we systematically altered several design parameters and targeted multiple reporter and essential genes in Escherichia coli. A paired termini (PT) design, where flanking inverted repeats create paired dsRNA termini, proved effective. PTasRNAs targeted against the ackA gene within the acetate kinase-phosphotransacetylase operon (ackA-pta) triggered target mRNA decay and a 78% reduction in AckA activity with high genetic penetrance. PTasRNAs are abundant and stable and function through an RNase III independent mechanism that requires a large stoichiometric excess of asRNA. Conditional ackA silencing reduced carbon flux to acetate and increased heterologous gene expression. The PT design also improved silencing of the essential fabI gene. Full anti-fabI PTasRNA induction prevented growth and partial induction sensitized cells to a FabI inhibitor. PTasRNAs have potential for functional genomics, antimicrobial discovery and metabolic flux control. PMID:17062631

Nakashima, Nobutaka; Tamura, Tomohiro; Good, Liam

2006-10-24

87

Modification of Seed Oil Composition in Arabidopsis by Artificial microRNA-Mediated Gene Silencing  

PubMed Central

Various post transcriptional gene silencing strategies have been developed and exploited to study gene function or engineer disease resistance. The recently developed artificial microRNA strategy is an alternative method of effectively silencing target genes. The ?12-desaturase (FAD2), Fatty acid elongase (FAE1), and Fatty acyl-ACP thioesterase B (FATB) were targeted with amiR159b-based constructs in Arabidopsis thaliana to evaluate changes in oil composition when expressed with the seed-specific Brassica napus truncated napin (FP1) promoter. Fatty acid profiles from transgenic homozygous seeds reveal that the targeted genes were silenced. The down-regulation of the AtFAD-2 gene substantially increased oleic acid from the normal levels of ?15% to as high as 63.3 and reduced total PUFA content (18:2?9,12?+?18:3?9,12,15?+?20:2?11,14?+?20:3?11,14,17) from 46.8 to 4.8%. ?12-desaturase activity was reduced to levels as low as those in the null fad-2-1 and fad-2-2 mutants. Silencing of the FAE1 gene resulted in the reduction of eicosenoic acid (20:1?11) to 1.9 from 15.4% and silencing of FATB resulted in the reduction of palmitic acid (16:0) to 4.4% from 8.0%. Reduction in FATB activity is comparable with a FATB knock-out mutant. These results demonstrate for the first time amiR159b constructs targeted against three endogenous seed-expressed genes are clearly able to down-regulate and generate genotypic changes that are inherited stably over three generations.

Belide, Srinivas; Petrie, James Robertson; Shrestha, Pushkar; Singh, Surinder Pal

2012-01-01

88

Pulmonary Gene Silencing in Transgenic EGFP Mice Using Aerosolised Chitosan\\/siRNA Nanoparticles  

Microsoft Academic Search

Purpose  This work describes the production and application of an aerosolised formulation of chitosan nanoparticles for improved pulmonary\\u000a siRNA delivery and gene silencing in mice.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Aerosolised chitosan\\/siRNA nanoparticles were pneumatically formed using a nebulising catheter and sized by laser diffraction.\\u000a In vitro silencing of aerosolised and non-aerosolised formulations was evaluated in an EGFP endogenous-expressing H1299 cell line\\u000a by flow cytometry. Non-invasive

Ebbe J. B. Nielsen; Jan M. Nielsen; Daniel Becker; Alexander Karlas; Hridayesh Prakash; Sys Z. Glud; Jonathan Merrison; Flemming Besenbacher; Thomas F. Meyer; Jørgen Kjems; Kenneth A. Howard

2010-01-01

89

RNA-Mediated Transcriptional Gene Silencing in Human Cells  

Microsoft Academic Search

The utilization of small interfering RNAs (siRNAs) represents a new paradigm in gene knockout technology. siRNAs can be used\\u000a to knockdown the expression of a particular gene by targeting the mRNA in a post-transcriptional manner. While there are a\\u000a plethora of reports applying siRNA-mediated post-transcriptional silencing (PTGS) therapeutically there are apparent limitations\\u000a such as the duration of the effect and

Kevin V. Morris

90

Maternal factor-mediated epigenetic gene silencing in the ascidian Ciona intestinalis  

Microsoft Academic Search

Epigenetic regulation of genes plays a critical role in achieving proper gene expression during development, and it has been\\u000a reported that epigenetic modifications are associated with transposon silencing in many organisms. Here, we report a type\\u000a of epigenetic gene silencing, maternal gfp\\/gene silencing (MGS), in the basal chordate Ciona intestinalis. A transgenic line of Ciona, Tg[MiTFr3dTPOG]45 (abbreviated as Tg45), which

Yasunori Sasakura; Miho M. Suzuki; Akiko Hozumi; Kazuo Inaba; Nori Satoh

2010-01-01

91

Virus-induced gene silencing in strawberry fruit.  

PubMed

Virus-induced gene silencing (VIGS) is a technology that exploits an RNA-mediated antiviral defense mechanism and which has great potential for use in plant reverse genetics. Recently, whole-genome studies and gene sequencing in plants have produced a massive amount of sequence information. A major challenge for plant biologists is to convert this sequence information into functional information. In this study, we demonstrate that VIGS can be used to determine gene functions in strawberry and that it is a powerful new tool for studying fruit ripening. The ABA synthetic gene FaNCED1, which can promote strawberry fruit ripening, was used as the reporter gene. In this chapter, we describe the use of TRV-mediated VIGS in strawberry fruit. PMID:23386306

Jia, Haifeng; Shen, Yuanyue

2013-01-01

92

Characterization of Arabidopsis Genes Involved in Gene Silencing. Final Progress Report  

SciTech Connect

Enhancer of gene silencing 1 (egs1) is an Arabidopsis mutant that enhances post-transcriptional gene silencing of the rolB gene introduced by genetic engineering (transgene). The goal of our proposal was cloning EGS1 based on its map position. Although we screened more than 2000 chromosomes for recombination, we were unable to get closer than 2 cM to the gene. We experienced an unexpected tendency of the post-transcriptionally silenced transgene to switch to a more stable silenced state. This made it impossible to select egs1 homozygotes for map based cloning. This forced us to reconsider our cloning strategy. One possibility would have been to use a different transgene as the target of gene silencing. We tested two other transgenes. Both encoded proteins unrelated to the first but they were all expressed from the same type of promoter and they all had a similar tendency to become post-transcriptionally silenced. After screening over 80 F2 segregants from each cross between our egs1 mutant and Arabidopsis of the same ecotype homozygous for the new transgene, we were disappointed to find that the egs1 mutation did not enhance post-transcription silencing of the two new genes. In 80 plants we expected to have between 4 and 6 plants that were homozygous for the transgene and for the mutant egs1 allele. If egs1 mutations could enhance gene silencing of the new transgene, these plants would not express it. However all the double homozygotes still expressed the transgene. Therefore, we could not change the target transgene for mapping. This was the state of the cloning at the time for renewal of the grant in 1999. Because the selection of new meaningful recombinant plants had become extremely inefficient using the original rolB transgene, we abandoned the attempt at map based cloning and did not apply for further funding.

Grant, S. R.

1999-02-05

93

siRNA-mediated gene silencing: a global genome view  

PubMed Central

The task of specific gene knockdown in vitro has been facilitated through the use of short interfering RNA (siRNA), which is now widely used for studying gene function, as well as for identifying and validating new drug targets. We explored the possibility of using siRNA for dissecting cellular pathways by siRNA-mediated gene silencing followed by gene expression profiling and systematic pathway analysis. We used siRNA to eliminate the Rb1 gene in human cells and determined the effects of Rb1 knockdown on the cell by using microarray-based gene expression profiling coupled with quantitative pathway analysis using the GenMapp and MappFinder software. Retinoblastoma protein is one of the key cell cycle regulators, which exerts its function through its interactions with E2F transcription factors. Rb1 knockdown affected G1/S and G2/M transitions of the cell cycle, DNA replication and repair, mitosis, and apoptosis, indicating that siRNA-mediated transient elimination of Rb1 mimics the control of cell cycle through Rb1 dissociation from E2F. Additionally, we observed significant effects on the processes of DNA damage response and epigenetic regulation of gene expression. Analysis of transcription factor binding sites was utilized to distinguish between putative direct targets and genes induced through other mechanisms. Our approach, which combines the use of siRNA-mediated gene silencing, mediated microarray screening and quantitative pathway analysis, can be used in functional genomics to elucidate the role of the target gene in intracellular pathways. The approach also holds significant promise for compound selection in drug discovery.

Semizarov, Dimitri; Kroeger, Paul; Fesik, Stephen

2004-01-01

94

Optimized cDNA libraries for virus-induced gene silencing (VIGS) using tobacco rattle virus  

PubMed Central

Background Virus-induced gene silencing (VIGS) has emerged as a method for performing rapid loss-of-function experiments in plants. Despite its expanding use, the effect of host gene insert length and other properties on silencing efficiency have not been systematically tested. In this study, we probed the optimal properties of cDNA fragments of the phytoene desaturase (PDS) gene for efficient VIGS in Nicotiana benthamiana using tobacco rattle virus (TRV). Results NbPDS inserts of between 192 bp and 1304 bp led to efficient silencing as determined by analysis of leaf chlorophyll a levels. The region of the NbPDS cDNA used for silencing had a small effect on silencing efficiency with 5' and 3' located inserts performing more poorly than those from the middle. Silencing efficiency was reduced by the inclusion of a 24 bp poly(A) or poly(G) homopolymeric region. We developed a method for constructing cDNA libraries for use as a source of VIGS-ready constructs. Library construction involved the synthesis of cDNA on a solid phase support, digestion with RsaI to yield short cDNA fragments lacking poly(A) tails and suppression subtractive hybridization to enrich for differentially expressed transcripts. We constructed two cDNA libraries from methyl-jasmonate treated N. benthamiana roots and obtained 2948 ESTs. Thirty percent of the cDNA inserts were 401–500 bp in length and 99.5% lacked poly(A) tails. To test the efficiency of constructs derived from the VIGS-cDNA libraries, we silenced the nicotine biosynthetic enzyme, putrescine N-methyltransferase (PMT), with ten different VIGS-NbPMT constructs ranging from 122 bp to 517 bp. Leaf nicotine levels were reduced by more than 90% in all plants infected with the NbPMT constructs. Conclusion Based on the silencing of NbPDS and NbPMT, we suggest the following design guidelines for constructs in TRV vectors: (1) Insert lengths should be in the range of ~200 bp to ~1300 bp, (2) they should be positioned in the middle of the cDNA and (3) homopolymeric regions (i.e. poly(A/T) tails) should not be included. Our VIGS-cDNA library method, which incorporates these guidelines to produce sequenced, VIGS-ready cDNAs, will be useful for both fast-forward and reverse genetics experiments in TRV vectors.

Liu, Enwu; Page, Jonathan E

2008-01-01

95

Global Reactivation of Epigenetically Silenced Genes in Prostate Cancer  

PubMed Central

Transcriptional silencing associated with aberrant promoter hypermethylation is a common mechanism of inactivation of tumor suppressor genes in cancer cells. To globally profile the genes silenced by hypermethylation in prostate cancer, we screened a whole genome expression microarray for genes reactivated in the LNCaP, DU-145, PC-3 and MDA2b prostate tumor cell lines after treatment with the demethylating drug 5-aza-2 deoxycytidine and histone deacetylation inhibiting drug trichostatin A. A total of 2997 genes showed at least 2-fold upregulation of expression after drug treatment in at least one prostate tumor cell line. For validation we examined the first 45 genes, ranked by upregulation of expression, that had a typical CpG island and were known to be expressed in the normal cell counterpart. Two important findings were firstly that several genes known to be frequently hypermethylated in prostate cancer were apparent. Secondly, validation studies revealed eight novel genes hypermethylated in the prostate tumor cell lines, four of which were unmethylated in normal prostate cells and hypermethylated in primary prostate tumors (SLC15A3 66%, KRT7 54%, TACSTD2 17%, GADD45b 3%). Thus, we established the utility of our screen for genes hypermethylated in prostate cancer cells. One of the novel genes was TACSTD2/TROP2 a marker of human prostate basal cells with stem cell characteristics. TACSTD2 was unmethylated in prostatic intraepithelial neoplasia and may have utility in emerging methylation-based detection of prostate cancer tests. Further study of the hypermethylome will provide insight into the biology of the disease and facilitate translational studies in prostate cancer.

Ibragimova, Ilsiya; de Caceres, Inmaculada Ibanez; Hoffman, Amanda M.; Potapova, Anna; Dulaimi, Essel; Al-Saleem, Tahseen; Hudes, Gary R.; Ochs, Michael F.; Cairns, Paul

2010-01-01

96

Simultaneous silencing of multiple genes in the apple scab fungus, Venturia inaequalis, by expression of RNA with chimeric inverted repeats  

Microsoft Academic Search

RNA-mediated gene silencing has been demonstrated in plants, animals, and more recently in filamentous fungi. Here, we report high frequency, RNA-mediated gene silencing in the apple scab fungus, Venturia inaequalis. The green fluorescent protein (GFP) transgene was silenced in a GFP-expressing transformant. An endogenous gene, trihydroxynaphthalene reductase (THN), involved in melanin biosynthesis, was also silenced. Silencing of these two genes

Anna Fitzgerald; Jan A. L. van Kan; Kim M. Plummer

2004-01-01

97

Isolation and characterization of novel F-plasmid sopB mutants defective in gene silencing  

Microsoft Academic Search

The product of the sopB gene on the Escherichia coli F-plasmid has been shown to silence genes in the vicinity of its binding region, sopC, when overexpressed. We searched for mutants defective in SopB-dependent silencing by screening for a plasmid incompatibility phenotype, in order to examine the relationship between gene silencing and the intracellular localization of SopB, as revealed by

Y. Kubo; S.-K. Kim; R. Hanai

2002-01-01

98

Construction and properties of a gene-silencing vector based on Poplar mosaic virus (genus Carlavirus)  

Microsoft Academic Search

A gene-silencing vector based on a full-length genomic clone of Poplar mosaic virus (PopMV) was constructed, with coat protein and movement protein genes removed, and containing instead, the coding sequence for green fluorescent protein (GFP). This paper demonstrates that the PopMV-derived gene-silencing vector was able to silence GFP expression in GFP transgenic Nicotiana benthamiana plants. The full-length genome of an

M. Naylor; J. Reeves; J. I. Cooper; M.-L. Edwards; H. Wang

2005-01-01

99

Novel vectors for retrotransposon-induced gene silencing in Magnaporthe oryzae  

Microsoft Academic Search

Here we report a novel system to induce RNA silencing in Magnaporthe\\u000a oryzae using the retrotransposon MAGGY. The gene-silencing vector pSilent-MG carries a MAGGY variant with a unique cloning site\\u000a in the 3? UTR region and a geneticin-resistance cassette as a selection marker. A gene-silencing assay with a GFP gene revealed\\u000a that pSilent-MG vectors induced gene silencing at a practical

Ba Van Vu; Masako Takino; Toshiki Murata; Hitoshi Nakayashiki

2011-01-01

100

A new virus-induced gene silencing vector based on Euphorbia mosaic virus-Yucatan peninsula for NPR1 silencing in Nicotiana benthamiana and Capsicum annuum var. Anaheim.  

PubMed

Virus-induced gene silencing is based on the sequence-specific degradation of RNA. Here, a gene silencing vector derived from EuMV-YP, named pEuMV-YP:?AV1, was used to silence ChlI and NPR1 genes in Nicotiana benthamiana. The silencing of the ChlI transcripts was efficient in the stems, petioles and leaves as reflected in tissue bleaching and reduced transcript levels. The silencing was stable, reaching the flowers and fruits, and was observed throughout the life cycle of the plants. Additionally, the silencing of the NPR1 gene was efficient in both N. benthamiana and Capsicum annuum. After silencing, the plants' viral symptoms increased to levels similar to those seen in wild-type plants. These results suggest that NPR1 plays a role in the compatible interactions of EuMV-YP N. benthamiana and EuMV-C. annum var. anaheim. PMID:23546940

Villanueva-Alonzo, Hernan J; Us-Camas, Rosa Y; López-Ochoa, Luisa A; Robertson, Dominique; Guerra-Peraza, Orlene; Minero-García, Yereni; Moreno-Valenzuela, Oscar A

2013-04-02

101

Temporal and spatial Bean pod mottle virus-induced gene silencing in soybean.  

PubMed

Virus-induced gene silencing (VIGS) is a powerful reverse genetics tool in plant science. In this study, we investigated the temporal and spatial silencing patterns achieved by Bean pod mottle virus (BPMV)-based VIGS in soybean using virus constructs targeting green fluorescence protein (GFP). Silencing GFP enabled an in-depth analysis of silencing in soybean tissues over time in a transgenic line constitutively expressing GFP. We discovered evidence for variable GFP silencing based on insert orientation and targeted region in the coding sequence. A 3' sequence in reverse orientation produced the strongest silencing phenotypes. Furthermore, we documented that BPMV VIGS can achieve widespread silencing in a broad range of tissues, including leaves, stems, flowers and roots. Near-complete silencing was attained in leaves and flowers. Although weaker than in shoots, the observed gene silencing in soybean roots will also allow reverse genetics studies in this tissue. When GFP fluorescence was assayed in cross-sections of stems and leaf petioles, near-complete and uniform silencing was observed in all cell types. Silencing was observed from as early as 2?weeks post-virus inoculation in leaves to 7?weeks post-virus inoculation in flowers, suggesting that this system can induce and maintain silencing for significant durations. PMID:22738403

Juvale, Parijat S; Hewezi, Tarek; Zhang, Chunquan; Kandoth, Pramod Kaitheri; Mitchum, Melissa G; Hill, John H; Whitham, Steven A; Baum, Thomas J

2012-06-27

102

Taming of transposable elements by homology-dependent gene silencing.  

PubMed

Transposable elements can invade virgin genomes within a few generations, after which the elements are 'tamed' and retain only limited transpositional activity. Introduction of the I element, a transposon similar to mammalian LINE elements, into Drosophila melanogaster genomes devoid of such elements initially results in high-frequency transposition of the incoming transposon, high mutation rate, chromosomal nondisjunction and female sterility, a syndrome referred to as hybrid dysgenesis (for review, see refs 2-4); a related syndrome has also been described in mammals. High-frequency transposition is transient, as the number of I elements reaches a finite value and transposition ceases after approximately ten generations. It has been proposed that the I elements encode a factor that negatively regulates their own transcription, but evidence for such a mechanism is lacking. Using the hybrid dysgenesis syndrome in Drosophila as a model, we show here that transpositional activity of the I element can be repressed by prior introduction of transgenes expressing a small internal region of the I element. This autoregulation presents features characteristic of homology-dependent gene silencing, a process known as cosuppression. Repression does not require any translatable sequence, its severity correlates with transgene copy number and it develops in a generation-dependent manner via germline transmission of a silencing effector in females only. These results demonstrate that transposable elements are prone to and can be tamed by homology-dependent gene silencing, a process that may have emerged during the course of evolution as a specific defense mechanism against these elements. PMID:9988275

Jensen, S; Gassama, M P; Heidmann, T

1999-02-01

103

Domains of gene silencing near the left end of chromosome III in Saccharomyces cerevisiae.  

PubMed Central

In Saccharomyces cerevisiae the HM loci and regions adjacent to the telomeres are transcriptionally silent. HML is situated 11 kb from the left telomere of chromosome III. I have systematically examined gene silencing along this 11-kb chromosomal region. I found that silencing extends at least 1.1 kb beyond HML, indicating that the HML E silencer acts on both sides. Moreover, I obtained evidence indicating that a 0.71-kb sequence near the E silencer acts as a barrier to the spread of silencing and coincides with the left boundary of the silent HML domain. I also showed that silencing at the telomere is limited to an approximately 2-kb domain. On the other hand, an approximately 7-kb region between HML and the telomere is not silenced by HML or the telomere. These results provide a clear example of organization of the eukaryotic genome into interspersed domains with distinct potentials for gene expression.

Bi, Xin

2002-01-01

104

Domains of gene silencing near the left end of chromosome III in Saccharomyces cerevisiae.  

PubMed

In Saccharomyces cerevisiae the HM loci and regions adjacent to the telomeres are transcriptionally silent. HML is situated 11 kb from the left telomere of chromosome III. I have systematically examined gene silencing along this 11-kb chromosomal region. I found that silencing extends at least 1.1 kb beyond HML, indicating that the HML E silencer acts on both sides. Moreover, I obtained evidence indicating that a 0.71-kb sequence near the E silencer acts as a barrier to the spread of silencing and coincides with the left boundary of the silent HML domain. I also showed that silencing at the telomere is limited to an approximately 2-kb domain. On the other hand, an approximately 7-kb region between HML and the telomere is not silenced by HML or the telomere. These results provide a clear example of organization of the eukaryotic genome into interspersed domains with distinct potentials for gene expression. PMID:11973296

Bi, Xin

2002-04-01

105

Convergent transcription induces transcriptional gene silencing in fission yeast and mammalian cells  

PubMed Central

We demonstrate that convergent transcription induces transcriptional gene silencing (TGS) in trans for both fission yeast and mammalian cells. This methodology has advantages over existing strategies to induce gene silencing. Previous studies in fission yeast have characterized TGS as a cis specific process involving RNA interference that maintains heterochromatic regions such as centromeres. In contrast for mammalian cells, gene silencing is known to occur by a post transcriptional mechanism employing exogenous siRNAs or endogenous microRNAs to inactivate mRNA. We now show that introduction of convergent transcription plasmids into either S. pombe or mammalian cells allows the production of dsRNA from inserted gene fragments resulting in TGS of endogenous genes. We predict that using convergent transcription to induce gene silencing will prove a generally useful strategy and allow a fuller molecular understanding of the biology of transcriptional gene silencing.

Gullerova, Monika; Proudfoot, Nick J.

2012-01-01

106

RNA silencing as a tool to uncover gene function and engineer novel traits in soybean.  

PubMed

RNA silencing refers collectively to diverse RNA-mediated pathways of nucleotide-sequence-specific inhibition of gene expression. It has been used to analyze gene function and engineer novel traits in various organisms. Here, we review the application of RNA silencing in soybean. To produce soybean lines, in which a particular gene is stably silenced, researchers have frequently used a transgene that transcribes inverted repeats of a target gene segment. Suppression of gene expression in developing soybean embryos has been one of the main focuses of metabolic engineering using transgene-induced silencing. Plants that have enhanced resistance against diseases caused by viruses or cyst nematode have also been produced. Meanwhile, Agrobacterium rhizogenes-mediated transformation has been used to induce RNA silencing in roots, which enabled analysis of the roles of gene products in nodulation or disease resistance. RNA silencing has also been induced using viral vectors, which is particularly useful for gene function analysis. So far, three viral vectors for virus-induced gene silencing have been developed for soybean. One of the features of the soybean genome is the presence of a large number of duplicated genes. Potential use of RNA silencing technology in combination with forward genetic approaches for analyzing duplicated genes is discussed. PMID:23136487

Kasai, Megumi; Kanazawa, Akira

2012-02-04

107

Gene silencing in adipose tissue macrophages regulates whole-body metabolism in obese mice.  

PubMed

Adipose tissue (AT) inflammation and infiltration by macrophages is associated with insulin resistance and type 2 diabetes in obese humans, offering a potential target for therapeutics. However, whether AT macrophages (ATMs) directly contribute to systemic glucose intolerance has not been determined. The reason is the lack of methods to ablate inflammatory genes expressed in macrophages specifically localized within AT depots, leaving macrophages in other tissues unaffected. Here we report that i.p. administration of siRNA encapsulated by glucan shells in obese mice selectively silences genes in epididymal ATMs, whereas macrophages within lung, spleen, kidney, heart, skeletal muscle, subcutaneous (SubQ) adipose, and liver are not targeted. Such administration of GeRPs to silence the inflammatory cytokines TNF-? or osteopontin in epididymal ATMs of obese mice caused significant improvement in glucose tolerance. These data are consistent with the hypothesis that cytokines produced by ATMs can exacerbate whole-body glucose intolerance. PMID:23630254

Aouadi, Myriam; Tencerova, Michaela; Vangala, Pranitha; Yawe, Joseph C; Nicoloro, Sarah M; Amano, Shinya U; Cohen, Jessica L; Czech, Michael P

2013-04-29

108

RNA interference in Entamoeba histolytica: implications for parasite biology and gene silencing  

PubMed Central

Entamoeba histolytica is a major health threat to people in developing countries, where it causes invasive diarrhea and liver abscesses. The study of this important human pathogen has been hindered by a lack of tools for genetic manipulation. Recently, a number of genetic approaches based on variations of the RNAi method have been successfully developed and cloning of endogenous small-interfering RNAs from E. histolytica revealed an abundant population of small RNAs with an unusual 5?-polyphosphate structure. However, little is known about the implications of these findings to amebic biology or the mechanisms of gene silencing in this organism. In this article we review the literature relevant to RNAi in E. histolytica, discuss its implications for advances in gene silencing in this organism and outline potential future directions towards understanding the repertoire of RNAi and its impact on the biology of this deep-branching eukaryotic parasite.

Zhang, Hanbang; Pompey, Justine M; Singh, Upinder

2011-01-01

109

Development of a gene silencing DNA vector derived from a broad host range geminivirus  

Microsoft Academic Search

BACKGROUND: Gene silencing is proving to be a powerful tool for genetic, developmental, and physiological analyses. The use of viral induced gene silencing (VIGS) offers advantages to transgenic approaches as it can be potentially applied to non-model systems for which transgenic techniques are not readily available. However, many VIGS vectors are derived from Gemini viruses that have limited host ranges.

Edward M Golenberg; D Noah Sather; Leandria C Hancock; Kenneth J Buckley; Natalie M Villafranco; David M Bisaro

2009-01-01

110

RNA-DNA Interactions and DNA Methylation in PostTranscriptional Gene Silencing  

Microsoft Academic Search

Post-transcriptional gene silencing (PTGS) is a homology-dependent process that reduces cytoplasmic RNA levels. In several experimental systems, there is also an association of PTGS with methylation of DNA. To investigate this associ- ation, we used plants carrying a transgene encoding the green fluorescent protein (GFP). Gene silencing was induced using potato virus X RNA vectors carrying parts of the coding

Al Jones; Andrew J. Hamilton; Olivier Voinnet; Carole L. Thomas; Andrew J. Maule; David C. Baulcombe

1999-01-01

111

RNA silencing of lactate dehydrogenase gene in Rhizopus oryzae  

PubMed Central

Rhizopus oryzae is a filamentous fungus, belonging to the order Mucorales. It can ferment a wide range of carbohydrates hydrolyzed from lignocellulosic materials and even cellobiose to produce ethanol. However, R. oryzae also produces lactic acid as a major metabolite, which reduces the yield of ethanol. In this study, we show that significant reduction of lactic acid production could be achieved by short (25nt) synthetic siRNAs targeting the ldhA gene. The average yield of lactic acid production by R. oryzae during the batch fermentation process, where glucose had been used as a sole carbon source, diminished from 0.07gm/gm in wild type to 0.01gm/gm in silenced samples. In contrast, the average yield of ethanol production increased from 0.39gm/gm in wild type to 0.45gm/gm in silenced samples. These results show 85.7% (gm/gm) reduction in lactic acid production as compared with the wild type R. oryzae, while an increase of 15.4% (gm/gm) in ethanol yield.

Gheinani, Ali Hashemi; Jahromi, Neda Haghayegh; Feuk-Lagerstedt, Elisabeth; Taherzadeh, Mohammad J

2011-01-01

112

A virus-induced gene silencing approach to understanding alkaloid metabolism in Catharanthus roseus  

PubMed Central

The anticancer agents vinblastine and vincristine are bisindole alkaloids derived from coupling vindoline and catharanthine, monoterpenoid indole alkaloids produced exclusively by Madagascar periwinkle (Catharanthus roseus) plants. Industrial production of vinblastine and vincristine currently relies on isolation from C. roseus leaves, a process that affords these compounds in 0.0003–0.01% yields. Metabolic engineering efforts to improve alkaloid content or provide alternative sources of the bisindole alkaloids ultimately rely on the isolation and characterization of the genes involved. Several vindoline biosynthetic genes have been isolated, and the cellular and subcellular organization of the corresponding enzymes has been well studied. However, due to the leaf-specific localization of vindoline biosynthesis, and the lack of production of this precursor in cell suspension and hairy root cultures of C. roseus, further elucidation of this pathway demands the development of reverse genetics approaches to assay gene function in planta. The bipartite pTRV vector system is a Tobacco Rattle Virus-based virus-induced gene silencing (VIGS) platform that has provided efficient and effective means to assay gene function in diverse plant systems. We have developed a VIGS method to investigate gene function in C. roseus plants using the pTRV vector system. The utility of this approach in understanding gene function in C. roseus leaves is demonstrated by silencing known vindoline biosynthetic genes previously characterized in vitro.

Liscombe, David K.; O'Connor, Sarah E.

2011-01-01

113

Perturbation Analysis of Heterochromatin-Mediated Gene Silencing and Somatic Inheritance  

PubMed Central

Repetitive sequences in eukaryotic genomes induce chromatin-mediated gene-silencing of juxtaposed genes. Many components that promote or antagonize silencing have been identified, but how heterochromatin causes variegated and heritable changes in gene expression remains mysterious. We have used inducible mis-expression in the Drosophila eye to recover new factors that alter silencing caused by the bwD allele, an insertion of repetitive satellite DNA that silences a bw+ allele on the homologous chromosome. Inducible modifiers allow perturbation of silencing at different times in development, and distinguish factors that affect establishment or maintenance of silencing. We find that diverse chromatin and RNA processing factors can de-repress silencing. Most factors are effective even in differentiated cells, implying that silent chromatin remains plastic. However, over-expression of the bantam microRNA or the crooked-legs (crol) zinc-finger protein only de-repress silencing when expressed in cycling cells. Over-expression of crol accelerates the cell cycle, and this is required for de-repression of silencing. Strikingly, continual over-expression of crol converts the speckled variegation pattern of bwD into sectored variegation, where de-repression is stably inherited through mitotic divisions. Over-expression of crol establishes an open chromatin state, but the factor is not needed to maintain this state. Our analysis reveals that active chromatin states can be efficiently inherited through cell divisions, with implications for the stable maintenance of gene expression patterns through development.

Schneiderman, Jonathan I.; Goldstein, Sara; Ahmad, Kami

2010-01-01

114

Cohesin and polycomb proteins functionally interact to control transcription at silenced and active genes.  

PubMed

Cohesin is crucial for proper chromosome segregation but also regulates gene transcription and organism development by poorly understood mechanisms. Using genome-wide assays in Drosophila developing wings and cultured cells, we find that cohesin functionally interacts with Polycomb group (PcG) silencing proteins at both silenced and active genes. Cohesin unexpectedly facilitates binding of Polycomb Repressive Complex 1 (PRC1) to many active genes, but their binding is mutually antagonistic at silenced genes. PRC1 depletion decreases phosphorylated RNA polymerase II and mRNA at many active genes but increases them at silenced genes. Depletion of cohesin reduces long-range interactions between Polycomb Response Elements in the invected-engrailed gene complex where it represses transcription. These studies reveal a previously unrecognized role for PRC1 in facilitating productive gene transcription and provide new insights into how cohesin and PRC1 control development. PMID:23818863

Schaaf, Cheri A; Misulovin, Ziva; Gause, Maria; Koenig, Amanda; Gohara, David W; Watson, Audrey; Dorsett, Dale

2013-06-20

115

Transcriptional silencing of an amoebapore gene in Entamoeba histolytica: molecular analysis and effect on pathogenicity.  

PubMed

Transcriptional silencing of the gene coding for amoebapore A (AP-A) was observed when trophozoites of Entamoeba histolytica were transfected with a hybrid plasmid construct containing the ap-a gene flanked by the upstream and downstream segments of the original Ehap-a gene. Transfectants were totally devoid of ap-a transcript and AP-A protein. An identical silencing effect was observed upon transfection with a plasmid that contained only the 5' upstream region of ap-a. Removal of the selecting antibiotic enabled the isolation of plasmidless clones, which retained in their progeny the silenced phenotype. E. histolytica cells were able to overexpress ap-a when transfected with a plasmid containing the gene flanked by the 5' and 3' regions of the EhRP-L21 gene. This plasmid, however, could not express ap-a in the retransfected, cloned trophozoites lacking AP-A. This is the first report of gene silencing in E. histolytica, and the mechanism appears to belong to transcriptional gene silencing and not to posttranscriptional gene silencing. This conclusion is based on the following results: (i) silencing was achieved by transfection of homologous 5' flanking sequences (470 bp of the Ehap-a gene), (ii) transcription initiation of Ehap-a was found to be blocked, and (iii) short double-stranded RNA fragments of the ap-a coding and noncoding sequences were not detected. Trophozoites lacking AP-A are nonpathogenic and impaired in their bacteriolytic capability. PMID:12684379

Bracha, Rivka; Nuchamowitz, Yael; Mirelman, David

2003-04-01

116

Influence of viral genes on the cell-to-cell spread of RNA silencing  

Microsoft Academic Search

The turnip crinkle virus-based vector TCV-GFPDCP had been devised previously to study cell-to-cell and long-distance spread of virus-induced RNA silencing. TCV-GFPDCP, which had been constructed by replac- ing the coat protein (CP) gene with a green fluorescent protein (GFP) coding sequence, was able to induce RNA silencing in single epidermal cells, from which RNA silencing spread from cell-to-cell. Using this

Yu Zhou; Eugene Ryabov; Xuemei Zhang; Yiguo Hong

2008-01-01

117

Maternally and Paternally Silenced Imprinted Genes Differ in Their Intron Content  

PubMed Central

Imprinted genes exhibit silencing of one of the parental alleles during embryonic development. In a previous study imprinted genes were found to have reduced intron content relative to a non-imprinted control set (Hurst et al., 1996). However, due to the small sample size, it was not possible to analyse the source of this effect. Here, we re-investigate this observation using larger datasets of imprinted and control (non-imprinted) genes that allow us to consider mouse and human, and maternally and paternally silenced, imprinted genes separately. We find that, in the human and mouse, there is reduced intron content in the maternally silenced imprinted genes relative to a non-imprinted control set. Among imprinted genes, a strong bias is also observed in the distribution of intronless genes, which are found exclusively in the maternally silenced dataset. The paternally silenced dataset in the human is not different to the control set; however, the mouse paternally silenced dataset has more introns than the control group. A direct comparison of mouse maternally and paternally silenced imprinted gene datasets shows that they differ significantly with respect to a variety of intron-related parameters. We discuss a variety of possible explanations for our observations.

Fahey, Marie E.; Mills, Walter; Higgins, Desmond G.

2004-01-01

118

The effect of RAFT-derived cationic block copolymer structure on gene silencing efficiency.  

PubMed

In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475)) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA(475)) from 7 to 69 units. The polymers were characterized using size exclusion chromatography and (1)H NMR. Chinese Hamster Ovary-GFP and Human Embryonic Kidney 293 cells were used to assay cell viability while the efficiency of block copolymers to complex with siRNA was evaluated by agarose gel electrophoresis. The ability of the polymer-siRNA complexes to enter into cells and to silence the targeted reporter gene enhanced green fluorescent protein (EGFP) was measured by using a CHO-GFP silencing assay. The length of the central cationic block appears to be the key structural parameter that has a significant effect on cell viability and gene silencing efficiency with block lengths of 110-120 monomer units being the optimum. The ABA block copolymer architecture is also critical with the outer hydrophilic blocks contributing to serum stability and overall efficiency of the polymer as a delivery system. PMID:22831854

Hinton, Tracey M; Guerrero-Sanchez, Carlos; Graham, Janease E; Le, Tam; Muir, Benjamin W; Shi, Shuning; Tizard, Mark L V; Gunatillake, Pathiraja A; McLean, Keith M; Thang, San H

2012-07-23

119

RNAi gene silencing affects cell and developmental plasticity in hydra.  

PubMed

The recent establishment of gene silencing through RNA interference upon feeding opens avenues to decipher the genetic control of regeneration in hydra. Following that approach, we identified three main stages for head regeneration. Immediately post-amputation, the serine protease inhibitor Kazal1 gene produced by the gland cells prevents from an excessive autophagy in regenerating tips. This cytoprotective function, or self-preservation, is similar to that played by Kazal-type proteins in the mammalian exocrine pancreas, in homeostatic or post-injury conditions, likely reflecting an evolutionarily conserved mechanism linking cell survival to tissue repair. Indeed, in wild-type hydra, within the first hours following mid-gastric section, an extensive cellular remodelling is taking place, including phenotypic cellular transitions and cell proliferation. The activation of the MAPK pathway, which leads to the RSK-dependent CREB phosphorylation, is required for these early cellular events. Later, at the early-late stage, the expression of the Gsx/cnox-2 ParaHox gene in proliferating apical neuronal progenitors is required for the de novo neurogenesis that precedes the emergence of the tentacle rudiments. Hence, head regeneration in wild-type hydra relies on spatially restricted and timely orchestrated cellular modifications, which display similarities with those reported during vertebrate epimorphic regeneration. These results suggest some conservation across evolution of the mechanisms driving the post-amputation reactivation of developmental programs. PMID:17631443

Galliot, Brigitte; Miljkovic-Licina, Marijana; Ghila, Luiza; Chera, Simona

2007-02-15

120

Differential gene silencing induced by short interfering RNA in cultured pine cells associates with the cell cycle phase  

Microsoft Academic Search

The double-stranded short interfering RNA (siRNA) molecules can silence targeted genes through sequence-specific cleavage of the cognate RNA transcript. The rapid adoption of technologies based on this siRNA interference mechanism has been a widely used method to analyze gene function in plants, invertebrates, and mammalian systems. In order to understand the dynamics of siRNA-mediated gene inactivation during cell division, we

Wei Tang; Ronald J. Newton; Douglas A. Weidner

2006-01-01

121

Hairpin RNAs and Retrotransposon LTRs Effect RNAi and Chromatin-Based Gene Silencing  

Microsoft Academic Search

The expression of short hairpin RNAs in several organisms silences gene expression by targeted mRNA degradation. This RNA interference (RNAi) pathway can also affect the genome, as DNA methylation arises at loci homologous to the target RNA in plants. We demonstrate in fission yeast that expression of a synthetic hairpin RNA is sufficient to silence the homologous locus in trans

Vera Schramke; Robin Allshire

2003-01-01

122

FACTORS INFLUENCING THE DEVELOPMENT OF GENE SILENCING WITHIN AGROBACTERIA INFUSED TABACCO LEAVES  

Technology Transfer Automated Retrieval System (TEKTRAN)

A highly sensitive luciferase-based transient assay, combined with viral suppressors of silencing, have been used to examine factors influencing the induction and level of post transcriptional gene silencing (PTGS) within leaves of Nicotiana tobacum infused with Agrobacteria. The timing of PTGS dev...

123

Transcriptional Silencing of an Amoebapore Gene in Entamoeba histolytica: Molecular Analysis and Effect on Pathogenicity  

Microsoft Academic Search

Transcriptional silencing of the gene coding for amoebapore A (AP-A) was observed when trophozoites of Entamoeba histolytica were transfected with a hybrid plasmid construct containing the ap-a gene flanked by the upstream and downstream segments of the original Ehap-a gene. Transfectants were totally devoid of ap-a transcript and AP-A protein. An identical silencing effect was observed upon transfection with a

Rivka Bracha; Yael Nuchamowitz; David Mirelman

2003-01-01

124

Heterologous virus-induced gene silencing as a promising approach in plant functional genomics  

Microsoft Academic Search

VIGS (virus induced gene silencing) is considered as a powerful genomics tool for characterizing the function of genes in\\u000a a few closely related plant species. The investigations have been carried out mainly in order to test if a pre-existing VIGS\\u000a vector can serve as an efficient tool for gene silencing in a diverse array of plant species. Another route of

Seied Ali Hosseini Tafreshi; Mansour Shariati; Mohammad Reza Mofid; Mojtaba Khayam Nekui; Abolghasem Esmaeili

125

Lentiviral-mediated RNAi in vivo silencing of Col6a1, a gene with complex tissue specific expression pattern  

Microsoft Academic Search

RNA interference (RNAi) through the use of lentiviral vectors is a valuable technique to induce loss of function mutations in mammals. Although very promising, the method has found only limited application and its general applicability remains to be established. Here we analyze how different factors influence RNAi mediated silencing of Col6a1, a gene of the extracellular matrix with a complex

Kosjenka Frka; Nicola Facchinello; Claudia Del Vecchio; Andrea Carpi; Matteo Curtarello; Rina Venerando; Alessia Angelin; Cristina Parolin; Paolo Bernardi; Paolo Bonaldo; Dino Volpin; Paola Braghetta; Giorgio M. Bressan

2009-01-01

126

Consistent gene silencing in transgenic plants expressing a replicating potato virus X RNA.  

PubMed Central

Tobacco plants were transformed with constructs in which the transgene was a cDNA of replicating potato virus X (PVX) RNA. The constructs, referred to here as amplicons, were the intact genome of PVX and PVX constructs modified to carry the beta-glucuronidase (GUS) reporter gene either as an additional gene or as a replacement for the coat protein gene (PVX/GUS/CP and PVX/GUS respectively). Transformed plants carrying these constructs displayed several phenotypes that we attribute to post-transcriptional gene silencing. These phenotypes include the absence of viral symptoms, low accumulation of transgene-derived RNA, extreme strain-specific resistance against PVX, low and non-uniform GUS expression (in the PVX/GUS and PVX/GUS/CP plants) and suppression of transiently expressed RNA sharing homology with the transgene. Importantly, the amplicon-mediated gene silencing was exhibited in all lines tested. There was no evidence of gene silencing in seven lines expressing a PVX RNA that was unable to replicate. From these data we conclude that the replicating viral RNA is a potent trigger of gene silencing. Moreover, amplicon-mediated gene silencing provides an important new strategy for the consistent activation of gene silencing in transgenic plants.

Angell, S M; Baulcombe, D C

1997-01-01

127

RNA interference: From gene silencing to gene-specific therapeutics  

Microsoft Academic Search

In the past 4 years, RNA interference (RNAi) has become widely used as an experimental tool to analyse the function of mammalian genes, both in vitro and in vivo. By harnessing an evolutionary conserved endogenous biological pathway, first identified in plants and lower organisms, double-stranded RNA (dsRNA) reagents are used to bind to and promote the degradation of target RNAs,

Ray K. M. Leung; Paul A. Whittaker

2005-01-01

128

Virus-induced gene silencing using artificial miRNAs in Nicotiana benthamiana.  

PubMed

Virus-induced gene silencing using artificial microRNAs (MIR VIGS) is a newly developed technique for plant reverse genetic studies. Traditional virus-induced gene silencing (VIGS) assays introduce a large gene fragment, which is expressed and then converted into small RNAs by the endogenous siRNA-based gene silencing machinery of the plant host. By contrast, MIR VIGS uses well-designed miRNAs to induce RNA-mediated silencing of the target gene. Using a single artificial miRNA can provide greater specificity by reducing off-target effects. Here, we describe a detailed protocol for MIR VIGS in Nicotiana benthamiana using a modified Cabbage leaf curl virus (CaLCuV)-based vector. PMID:23386298

Tang, Yang; Lai, Yizhen; Liu, Yule

2013-01-01

129

Increasing the amylose content of durum wheat through silencing of the SBEIIa genes  

PubMed Central

Background High amylose starch has attracted particular interest because of its correlation with the amount of Resistant Starch (RS) in food. RS plays a role similar to fibre with beneficial effects for human health, providing protection from several diseases such as colon cancer, diabetes, obesity, osteoporosis and cardiovascular diseases. Amylose content can be modified by a targeted manipulation of the starch biosynthetic pathway. In particular, the inactivation of the enzymes involved in amylopectin synthesis can lead to the increase of amylose content. In this work, genes encoding starch branching enzymes of class II (SBEIIa) were silenced using the RNA interference (RNAi) technique in two cultivars of durum wheat, using two different methods of transformation (biolistic and Agrobacterium). Expression of RNAi transcripts was targeted to the seed endosperm using a tissue-specific promoter. Results Amylose content was markedly increased in the durum wheat transgenic lines exhibiting SBEIIa gene silencing. Moreover the starch granules in these lines were deformed, possessing an irregular and deflated shape and being smaller than those present in the untransformed controls. Two novel granule bound proteins, identified by SDS-PAGE in SBEIIa RNAi lines, were investigated by mass spectrometry and shown to have strong homologies to the waxy proteins. RVA analysis showed new pasting properties associated with high amylose lines in comparison with untransformed controls. Finally, pleiotropic effects on other starch genes were found by semi-quantitative and Real-Time reverse transcription-polymerase chain reaction (RT-PCR). Conclusion We have found that the silencing of SBEIIa genes in durum wheat causes obvious alterations in granule morphology and starch composition, leading to high amylose wheat. Results obtained with two different methods of transformation and in two durum wheat cultivars were comparable.

2010-01-01

130

Aberrant Epigenetic Silencing Is Triggered by a Transient Reduction in Gene Expression  

PubMed Central

Background Aberrant epigenetic silencing plays a major role in cancer formation by inactivating tumor suppressor genes. While the endpoints of aberrant silencing are known, i.e., promoter region DNA methylation and altered histone modifications, the triggers of silencing are not known. We used the tet-off system to test the hypothesis that a transient reduction in gene expression will sensitize a promoter to undergo epigenetic silencing. Methodology/Principal Findings The tet responsive promoter (PTRE) was used to drive expression of the selectable human HPRT cDNA in independent transfectants of an Hprt deficient mouse cell line. In this system, high basal HPRT expression is greatly reduced when doxycycline (Dox) is added to the culture medium. Exposure of the PTRE-HPRT transfectants to Dox induced HPRT deficient clones in a time dependent manner. A molecular analysis demonstrated promoter region DNA methylation, loss of histone modifications associated with expression (i.e., H3 lysine 9 and 14 acetylation and lysine 4 methylation), and acquisition of the repressive histone modification H3 lysine 9 methylation. These changes, which are consistent with aberrant epigenetic silencing, were not present in the Dox-treated cultures, with the exception of reduced H3 lysine 14 acetylation. Silenced alleles readily reactivated spontaneously or after treatment of cells with inhibitors of histone deacetylation and/or DNA methylation, but re-silencing of reactivated alleles did not require a new round of Dox exposure. Inhibition of histone deacetylation inhibited both the induction of silencing and re-silencing, whereas inhibition of DNA methylation had no such effect. Conclusions/Significance This study demonstrates that a transient reduction in gene expression triggers a pathway for aberrant silencing in mammalian cells and identifies histone deacetylation as a critical early step in this process. DNA methylation, in contrast, is a secondary step in the silencing pathway under study. A model to explain these observations is offered.

Oyer, Jon A.; Chu, Adrian; Brar, Sukhmani; Turker, Mitchell S.

2009-01-01

131

Induction of RNA interference in Caenorhabditis elegans by RNAs derived from plants exhibiting post-transcriptional gene silencing  

Microsoft Academic Search

The term 'gene silencing' refers to transcriptional and post-transcriptional control of gene expression. Related processes are found across kingdoms in plants and animals. We intended to test whether particular RNA constituents of a silenced plant can induce silencing in an animal. We generated Nicotiana benthamiana lines that expressed green fluorescent protein (GFP) from a transgene. Plants in which GFP expression

Alexandra Boutla; Kriton Kalantidis; Nektarios Tavernarakis; M ina Tsagris; Martin Tabler

2002-01-01

132

Heterologous virus-induced gene silencing as a promising approach in plant functional genomics.  

PubMed

VIGS (virus induced gene silencing) is considered as a powerful genomics tool for characterizing the function of genes in a few closely related plant species. The investigations have been carried out mainly in order to test if a pre-existing VIGS vector can serve as an efficient tool for gene silencing in a diverse array of plant species. Another route of investigation has been the constructing of new viral vectors to act in their hosts. Our approach was the creation of a heterologous system in which silencing of endogenous genes was achieved by sequences isolated from evolutionary remote species. In this study, we showed that a TRV-based vector cloned with sequences from a gymnosperm, Taxus baccata L. silenced the endogenous phytoene desaturase in an angiosperm, N. benthamiana. Our results showed that inserts of between 390 and 724 bp isolated from a conserved fragment of the Taxus PDS led to silencing of its homolog in tobacco. The real time analysis indicated that the expression of PDS was reduced 2.1- to 4.0-fold in pTRV-TbPDS infected plants compared with buffer treated plants. Once the best insert is identified and the conditions are optimized for heterologous silencing by pTRV-TbPDS in tobacco, then we can test if TRV can serve as an efficient silencing vector in Taxus. This strategy could also be used to silence a diverse array of genes from a wide range of species which have no VIGS protocol. The results also showed that plants silenced heterologously by the VIGS system a minimally affected with respect to plant growth which may be ideal for studying the genes that their complete loss of function may lead to decrease of plant growth or plant death. PMID:21655951

Hosseini Tafreshi, Seied Ali; Shariati, Mansour; Mofid, Mohammad Reza; Khayam Nekui, Mojtaba; Esmaeili, Abolghasem

2011-06-08

133

Small-Interfering RNA-Eluting Surfaces as a Novel Concept for Intravascular Local Gene Silencing  

PubMed Central

New drug-eluting stent (DES) methods have recently been demonstrated to improve outcomes of intravascular interventions. A novel technique is the design of gene-silencing stents that elute specific small-interfering RNAs (siRNAs) for better vascular wall regeneration. Although siRNAs used to alter gene expression have surpassed expectations in in vitro experiments, the functional and local delivery of siRNAs is still the major obstacle for the in vivo application of RNA interference. In this preliminary in vitro study we investigated a surface-immobilized siRNA delivery technique that would be readily adaptable for local intravascular applications in vivo. The transfection potency of gelatin coatings consisting of a specific siRNA complexed with polyethylenimine (PEI) was examined in primary human endothelial cells by flow cytometry and quantitative real-time polymerase chain reaction. Several media conditions, such as the presence or absence of serum during cultivation, were investigated. Furthermore, different siRNA and PEI amounts, as well as nitrogen/phosphate ratios, were tested for their transfection efficiency. Gelatin coatings consisting of PEI and siRNA against an exemplary endothelial adhesion molecule receptor achieved a significant knockdown of around 70%. The transfection efficiency of the coatings was not influenced by the presence of serum. The results of this preliminary study support the expectation that this novel coating may be favorable for local in vivo gene silencing (for example, when immobilized on stents or balloons for percutanous transluminal coronary angioplasty). However, further animal experiments are needed to confirm the translation into clinical practice. This intriguing technology leads the way to more sophisticated and individualized coatings for the post-DES era, toward silencing of genes involved in the pathway of intimal hyperplasia.

Nolte, Andrea; Walker, Tobias; Schneider, Martina; Kray, Oya; Avci-Adali, Meltem; Ziemer, Gerhard; Wendel, Hans Peter

2011-01-01

134

Herpes Simplex Virus Type 1 Suppresses RNA-Induced Gene Silencing in Mammalian Cells?  

PubMed Central

RNA-induced silencing is a potent innate antiviral defense strategy in plants, and suppression of silencing is a hallmark of pathogenic plant viruses. However, the impact of silencing as a mammalian antiviral defense mechanism and the ability of mammalian viruses to suppress silencing in natural host cells have remained controversial. The ability of herpes simplex virus type 1 (HSV-1) to suppress silencing was examined in a transient expression system that employed an imperfect hairpin to target degradation of transcripts encoding enhanced green fluorescent protein (EGFP). HSV-1 infection suppressed EGFP-specific silencing as demonstrated by increased EGFP mRNA levels and an increase in the EGFP mRNA half-life. The increase in EGFP mRNA stability occurred despite the well-characterized host macromolecular shutoff functions of HSV-1 that globally destabilize mRNAs. Moreover, mutant viruses defective in these functions increased the stability of EGFP mRNA even more than did the wild-type virus in silenced cells compared to results in control cells. The importance of RNA silencing to HSV-1 replication was confirmed by a significantly enhanced virus burst size in cells in which silencing was knocked down with small inhibitory RNAs directed to Argonaute 2, an integral component of the silencing complex. Given that HSV-1 encodes several microRNAs, it is possible that a dynamic equilibrium exists between silencing and silencing suppression that is capable of modulating viral gene expression to promote replication, to evade host defenses, and/or to promote latency.

Wu, Zetang; Zhu, Yali; Bisaro, David M.; Parris, Deborah S.

2009-01-01

135

Development and application of an efficient virus-induced gene silencing system in Nicotiana tabacum using geminivirus alphasatellite  

Microsoft Academic Search

Virus-induced gene silencing (VIGS) is a recently developed technique for characterizing the function of plant genes by gene\\u000a transcript suppression and is increasingly used to generate transient loss-of-function assays. Here we report that the 2mDNA1,\\u000a a geminivirus satellite vector, can induce efficient gene silencing in Nicotiana tabacum with Tobacco curly shoot virus. We have successfully silenced the ?-glucuronidase (GUS) gene

Chang-jun Huang; Tong Zhang; Fang-fang Li; Xin-yue Zhang; Xue-ping Zhou

2011-01-01

136

Gene silencing by H-NS from distal DNA site.  

PubMed

In the modern concept of gene regulation, 'DNA looping' is the most common underlying mechanism in the interaction between RNA polymerase (RNAP) and transcription factors acting at a distance. This study demonstrates an additional mechanism by which DNA-bound proteins communicate with each other, by analysing the bacterial histone-like nucleoid-structuring protein (H-NS), a general transcriptional silencer. The LEE5 promoter (LEE5p) of enteropathogenic Escherichia coli was used as a model system to investigate the mechanism of H-NS-mediated transcription repression. We found that H-NS represses LEE5p by binding to a cluster of A tracks upstream of -114, followed by spreading to a site at the promoter through the oligomerization of H-NS molecules. At the promoter, the H-NS makes a specific contact with the carboxy terminal domain of the ? subunit of RNAP, which prevents the processing of RNAP-promoter complexes into initiation-competent open promoter complexes, thereby regulating LEE5p from distance. PMID:22924981

Shin, Minsang; Lagda, Arvin Cesar; Lee, Jae Woong; Bhat, Abhay; Rhee, Joon Haeng; Kim, Jeong-Sun; Takeyasu, Kunio; Choy, Hyon E

2012-09-14

137

Construction of hairpin RNA expressing vectors for RNA-mediated gene silencing in fungi  

Technology Transfer Automated Retrieval System (TEKTRAN)

RNA-mediated gene silencing is one of the major tools for functional genomics in fungi and can be achieved by transformation with constructs that express hairpin (hp) RNA with sequences homologous to the target gene(s). To make an hpRNA expression construct, a portion of the target gene can be ampl...

138

Therapeutic silencing of an endogenous gene by systemic administration of modified siRNAs  

Microsoft Academic Search

RNA interference (RNAi) holds considerable promise as a therapeutic approach to silence disease-causing genes, particularly those that encode so-called `non-druggable' targets that are not amenable to conventional therapeutics such as small molecules, proteins, or monoclonal antibodies. The main obstacle to achieving in vivo gene silencing by RNAi technologies is delivery. Here we show that chemically modified short interfering RNAs (siRNAs)

Jürgen Soutschek; Akin Akinc; Birgit Bramlage; Klaus Charisse; Rainer Constien; Mary Donoghue; Sayda Elbashir; Anke Geick; Philipp Hadwiger; Jens Harborth; Matthias John; Venkitasamy Kesavan; Gary Lavine; Rajendra K. Pandey; Timothy Racie; Kallanthottathil G. Rajeev; Ingo Röhl; Ivanka Toudjarska; Gang Wang; Silvio Wuschko; David Bumcrot; Victor Koteliansky; Stefan Limmer; Muthiah Manoharan; Hans-Peter Vornlocher

2004-01-01

139

siRNA-mediated gene silencing in vitro and in vivo  

Microsoft Academic Search

RNA interference is now established as an important biological strategy for gene silencing, but its application to mammalian cells has been limited by nonspecific inhibitory effects of long dsRNA on translation. Here, we describe a viral-mediated delivery mechanism that results in specific silencing of targeted genes through expression of small interfering RNA (siRNA). We establish proof of principle by markedly

Haibin Xia; Qinwen Mao; Henry L Paulson; Beverly L Davidson

2002-01-01

140

Highly efficient gene silencing using perfect complementary artificial miRNA targeting AP1 or heteromeric artificial miRNA targeting AP1 and CAL genes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Gene silencing is a useful technique for elucidating biological function of genes by knocking down their expression. Recently developed artificial microRNAs (amiRNAs) exploit an endogenous gene silencing mechanism that processes natural miRNA precursors to small silencing RNAs that target transcript...

141

Cell type specific, traceable gene silencing for functional gene analysis during vertebrate neural development  

PubMed Central

Many genes have several, sometimes divergent functions during development. Therefore, timing of gene knockdown for functional analysis during development has to be done with precise temporal control, as loss of a gene's function at early stages prevents its analysis later in development. RNAi, in combination with the accessibility of chicken embryos, is an effective approach for temporally controlled analysis of gene function during neural development. Here, we describe novel plasmid vectors that contain cell type-specific promoters/enhancers to drive the expression of a fluorescent marker, followed directly by a miR30-RNAi transcript for gene silencing. These vectors allow for direct tracing of cells experiencing gene silencing by the bright fluorescence. The level of knockdown is sufficient to reproduce the expected pathfinding defects upon perturbation of genes with known axon guidance functions. Mixing different vectors prior to electroporation enables the simultaneous knockdown of multiple genes in independent regions of the spinal cord. This permits complex cellular and molecular interactions to be examined during development, in a fast and precise manner. The advancements of the in ovo RNAi technique that we describe will not only markedly enhance functional gene analysis in the chicken, but also could be adapted to other organisms in developmental studies.

Wilson, Nicole H.; Stoeckli, Esther T.

2011-01-01

142

Selective gene silencing in activated leukocytes by targeting siRNAs to the integrin lymphocyte function-associated antigen-1  

Microsoft Academic Search

Silencing gene expression by RNAi is a powerful method for exploring gene function and validating drug targets and potentially for therapy. Lymphocytes and other primary blood cells are resistant to lipid-based transfection in vitro and are difficult to target in vivo. We show here that antibody-protamine fusion proteins targeting the human integrin lymphocyte function-associated antigen-1 (LFA-1) efficiently deliver siRNAs and

Dan Peer; Pengcheng Zhu; Christopher V. Carman; Judy Lieberman; Motomu Shimaoka

2007-01-01

143

Id1 overexpression is independent of repression and epigenetic silencing of tumor suppressor genes in melanoma  

PubMed Central

The full molecular consequences of oncogene activation during tumorigenesis are not well understood, but several studies have recently linked oncogene activation to epigenetic silencing of specific genes.1,2 Transcriptional repressor Id1 is overexpressed in many malignancies including melanoma, and Id1 targets include tumor suppressor genes TSP1, CDKN2A (p16) and CDKN1A (p21), which are frequently epigenetically silenced in cancer. We confirmed that both TSP1 and CDKN2A have abnormal promoter region DNa methylation in primary melanoma, but the mechanism by which this silencing occurs remains unknown. Here we explore the effects of stable lentiviral Id1 overexpression on the expression of these Id1 target genes in human melanoma cell lines. Overexpressed Id1 was functional and bound transcriptional activator E2A, but did not sequester E2A from gene promoters and repress gene expression. Therefore, these Id1 target genes were resistant to Id1-mediated gene silencing. Our results suggest that Id1 activation may need to occur at discrete stages in cooperation with additional gene dysregulation to repress and induce epigenetic silencing of tumor suppressor genes during melanoma progression.

Healey, Megan A.; Deaton, Staci L.; Alder, Jonathan K.; Winnepenninckx, Veronique; Casero, Robert A.; Herman, James G.

2013-01-01

144

RETRACTED ARTICLE: Virus-induced gene silencing for functional analysis of selected genes  

Microsoft Academic Search

Virus-induced gene silencing (VIGS) is a technology that exploits an RNA-mediated antiviral defense mechanism and has been\\u000a shown to be of great potential in plant reverse genetics. Circumvention of plant transformation, methodological simplicity,\\u000a robustness, and speedy results makes VIGS an attractive alternative instrument in functional genomics, even in a high throughput\\u000a fashion. The system is well established in Nicotiana benthamiana,

Mandar R. Godge; Arunima Purkayastha; Indranil Dasgupta; Prakash P. Kumar

2008-01-01

145

RNA interference: gene silencing in the fast lane  

Microsoft Academic Search

Sequencing of whole genomes has provided new perspectives into the blueprints of diverse organisms. Knowing the sequences, however, does not always tell us much about the function of the genes that regulate development and homeostasis. RNA interference (RNAi) is becoming the method of choice for gene function analysis in cells and whole organisms. Here we review the approaches available to

Ralf Kittler; Frank Buchholz

2003-01-01

146

Gene silencing using a heat-inducible RNAi system in Arabidopsis  

Microsoft Academic Search

Controlling gene expression during plant development is an efficient tool to explore gene function. In this paper, we describe a gene expression system driven by a heath shock gene promoter (HSP18.2), to trigger the expression of an intron-containing inverted repeat. RNA interference became a powerful way for gene functional analysis by reverse genetic approaches. However, constitutive gene silencing cannot be

Frédéric G. Masclaux; Martine Charpenteau; Taku Takahashi; Rafael Pont-Lezica; Jean-Philippe Galaud

2004-01-01

147

POST-TRANSCRIPTIONAL SILENCING OF POLYPHENOL OXIDASE GENE EXPRESSION IN RED CLOVER  

Technology Transfer Automated Retrieval System (TEKTRAN)

Post-transcriptional gene silencing (PTGS) by transformation of anti-sense, co-suppression, or hairpin RNA-producing constructs is a powerful tool to analyze in vivo gene function in plants. We are using this approach to reduce polyphenol oxidase (PPO) gene expression in red clover in order to bett...

148

Transgenesis by lentiviral vectors: Lack of gene silencing in mammalian embryonic stem cells and preimplantation embryos  

Microsoft Academic Search

The introduction of foreign genes into early mouse embryos and embryonic stem (ES) cells is invaluable for the analysis of gene function and regulation in the living animal. The use of vectors derived from retroviruses as gene transfer vehicles in this setting has had limited success because of silencing of transgene expression. Here, we show that vectors derived from lentiviruses,

Alexander Pfeifer; Masahito Ikawa; Yelena Dayn; Inder M. Verma

2002-01-01

149

Development of a gene silencing DNA vector derived from a broad host range geminivirus  

PubMed Central

Background Gene silencing is proving to be a powerful tool for genetic, developmental, and physiological analyses. The use of viral induced gene silencing (VIGS) offers advantages to transgenic approaches as it can be potentially applied to non-model systems for which transgenic techniques are not readily available. However, many VIGS vectors are derived from Gemini viruses that have limited host ranges. We present a new, unipartite vector that is derived from a curtovirus that has a broad host range and will be amenable to use in many non-model systems. Results The construction of a gene silencing vector derived from the geminivirus Beet curly top virus (BCTV), named pWSRi, is reported. Two versions of the vector have been developed to allow application by biolistic techniques or by agro-infiltration. We demonstrate its ability to silence nuclear genes including ribulose bisphosphate carboxylase small subunit (rbcS), transketolase, the sulfur allele of magnesium chelatase (ChlI), and two homeotic transcription factors in spinach or tomato by generating gene-specific knock-down phenotypes. Onset of phenotypes occurred 3 to 12 weeks post-inoculation, depending on the target gene, in organs that developed after the application. The vector lacks movement genes and we found no evidence for significant spread from the site of inoculation. However, viral amplification in inoculated tissue was detected and is necessary for systemic silencing, suggesting that signals generated from active viral replicons are efficiently transported within the plant. Conclusion The unique properties of the pWSRi vector, the ability to silence genes in meristem tissue, the separation of virus and silencing phenotypes, and the broad natural host range of BCTV, suggest that it will have wide utility.

Golenberg, Edward M; Sather, D Noah; Hancock, Leandria C; Buckley, Kenneth J; Villafranco, Natalie M; Bisaro, David M

2009-01-01

150

Silencing near tRNA genes is nucleosome-mediated and distinct from boundary element function.  

PubMed

Transfer RNA (tRNA) genes and other RNA polymerase III transcription units are dispersed in high copy throughout nuclear genomes, and can antagonize RNA polymerase II transcription in their immediate chromosomal locus. Previous work in Saccharomyces cerevisiae found that this local silencing required subnuclear clustering of the tRNA genes near the nucleolus. Here we show that the silencing also requires nucleosome participation, though the nature of the nucleosome interaction appears distinct from other forms of transcriptional silencing. Analysis of an extensive library of histone amino acid substitutions finds a large number of residues that affect the silencing, both in the histone N-terminal tails and on the nucleosome disk surface. The residues on the disk surfaces involved are largely distinct from those affecting other regulatory phenomena. Consistent with the large number of histone residues affecting tgm silencing, survey of chromatin modification mutations shows that several enzymes known to affect nucleosome modification and positioning are also required. The enzymes include an Rpd3 deacetylase complex, Hos1 deacetylase, Glc7 phosphatase, and the RSC nucleosome remodeling activity, but not multiple other activities required for other silencing forms or boundary element function at tRNA gene loci. Models for communication between the tRNA gene transcription complexes and local chromatin are discussed. PMID:23707796

Good, Paul D; Kendall, Ann; Ignatz-Hoover, James; Miller, Erin L; Pai, Dave A; Rivera, Sara R; Carrick, Brian; Engelke, David R

2013-05-23

151

A role for the nucleoporin Nup170p in chromatin structure and gene silencing  

PubMed Central

Embedded in the nuclear envelope, nuclear pore complexes (NPCs) not only regulate nuclear transport, but also interface with transcriptionally active euchromatin, largely silenced heterochromatin, as well as the boundaries between these regions. It is unclear what functional role NPCs play in establishing or maintaining these distinct chromatin domains. We report that the yeast NPC protein Nup170p interacts with regions of the genome containing ribosomal protein and subtelomeric genes. Here, it functions in nucleosome positioning and as a repressor of transcription. We show that the role of Nup170p in subtelomeric gene silencing is linked to its association with the RSC chromatin-remodeling complex and the silencing factor Sir4p, and that the binding of Nup170p and Sir4p to subtelomeric chromatin is cooperative and necessary for the association of telomeres with the nuclear envelope. Our results establish the NPC as an active participant in silencing and the formation of peripheral heterochromatin.

Van de Vosse, David W.; Wan, Yakun; Lapetina, Diego L.; Chen, Wei-Ming; Chiang, Jung-Hsien; Aitchison, John D.; Wozniak, Richard W.

2013-01-01

152

Gold Nanorod-siRNA Induces Efficient In Vivo Gene Silencing in the Rat Hippocampus  

PubMed Central

Gold nanorods (GNRs), cellular imaging nanoprobes, have been used for drug delivery therapy to immunologically privileged regions in the brain. We demonstrate that nanoplexes formed by electrostatic binding between negatively charged RNA and positively charged GNRs, silence the expression of the target housekeeping gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) within the CA1 hippocampal region of the rat brain, without showing cytotoxicity. Fluorescence imaging with siRNACy3GAPDH and dark field imaging using plasmonic enhanced scattering from GNRs were used to monitor the distribution of the nanoplexes within different neuronal cell types present in the targeted hippocampal region. Our results show robust nanoplex uptake and slow release of the fluorescent gene silencer with significant impact on suppression of GAPDH gene expression (70% gene silencing, >10 days post-injection). The observed gene knockdown using nanoplexes in targeted regions of the brain opens a new era of drug treatment for neurological disorders.

Bonoiu, Adela C.; Bergey, Earl J.; Ding, Hong; Hu, Rui; Kumar, Rajiv; Yong, Ken-Tye; Prasad, Paras N.; Mahajan, Supriya; Picchione, Kelly E.; Bhattacharjee, Arin; Ignatowski, Tracey A.

2011-01-01

153

Tomato Mosaic Virus Replication Protein Suppresses Virus-Targeted Posttranscriptional Gene Silencing  

Microsoft Academic Search

Posttranscriptional gene silencing (PTGS), a homology-dependent RNA degradation system, has a role in defending against virus infection in plants, but plant viruses encode a suppressor to combat PTGS. Using transgenic tobacco in which the expression of green fluorescent protein (GFP) is posttranscriptionally silenced, we investigated a tomato mosaic virus (ToMV)-encoded PTGS suppressor. Infection with wild-type ToMV (L strain) interrupted GFP

Kenji Kubota; Shinya Tsuda; Atsushi Tamai; Tetsuo Meshi

2003-01-01

154

HvCKX2 gene silencing by biolistic or Agrobacterium-mediated transformation in barley leads to different phenotypes  

PubMed Central

Background CKX genes encode cytokinin dehydrogenase enzymes (CKX), which metabolize cytokinins in plants and influence developmental processes. The genes are expressed in different tissues and organs during development; however, their exact role in barley is poorly understood. It has already been proven that RNA interference (RNAi)-based silencing of HvCKX1 decreased the CKX level, especially in those organs which showed the highest expression, i.e. developing kernels and roots, leading to higher plant productivity and higher mass of the roots [1]. The same type of RNAi construct was applied to silence HvCKX2 and analyze the function of the gene. Two cultivars of barley were transformed with the same silencing and selection cassettes by two different methods: biolistic and via Agrobacterium. Results The mean Agrobacterium-mediated transformation efficiency of Golden Promise was 3.47% (±2.82). The transcript level of HvCKX2 in segregating progeny of T1 lines was decreased to 34%. The reduction of the transcript in Agrobacterium-derived plants resulted in decreased CKX activity in the developing and developed leaves as well as in 7 DAP (days after pollination) spikes. The final phenotypic effect was increased productivity of T0 plants and T1 lines. Higher productivity was the result of the higher number of seeds and higher grain yield. It was also correlated with the higher 1000 grain weight, increased (by 7.5%) height of the plants and higher (from 0.5 to 2) numbers of spikes. The transformation efficiency of Golden Promise after biolistic transformation was more than twice as low compared to Agrobacterium. The transcript level in segregating progeny of T1 lines was decreased to 24%. Otherwise, the enzyme activity found in the leaves of the lines after biolistic transformation, especially in cv. Golden Promise, was very high, exceeding the relative level of the control lines. These unbalanced ratios of the transcript level and the activity of the CKX enzyme negatively affected kernel germination or anther development and as a consequence setting the seeds. The final phenotypic effect was the decreased productivity of T0 plants and T1 lines obtained via the biolistic silencing of HvCKX2. Conclusion The phenotypic result, which was higher productivity of silenced lines obtained via Agrobacterium, confirms the hypothesis that spatial and temporal differences in expression contributed to functional differentiation. The applicability of Agrobacterium-mediated transformation for gene silencing of developmentally regulated genes, like HvCKX2, was proven. Otherwise low productivity and disturbances in plant development of biolistic-silenced lines documented the unsuitability of the method. The possible reasons are discussed.

2012-01-01

155

dsRNA-induced gene silencing in Moniliophthora perniciosa, the causal agent of witches’ broom disease of cacao  

Microsoft Academic Search

The genome sequence of the hemibiotrophic fungus Moniliophthora perniciosa revealed genes possibly participating in the RNAi machinery. Therefore, studies were performed in order to investigate the efficiency of gene silencing by dsRNA. We showed that the reporter gfp gene stably introduced into the fungus genome can be silenced by transfection of in vitro synthesized gfpdsRNA. In addition, successful dsRNA-induced silencing

A. C. Caribé dos Santos; J. A. L. Sena; S. C. Santos; C. V. Dias; C. P. Pirovani; C. Pungartnik; R. R. Valle; J. C. M. Cascardo; M. Vincentz

2009-01-01

156

Mod5 protein binds to tRNA gene complexes and affects local transcriptional silencing.  

PubMed

The tRNA gene-mediated (tgm) silencing of RNA polymerase II promoters is dependent on subnuclear clustering of the tRNA genes, but genetic analysis shows that the silencing requires additional mechanisms. We have identified proteins that bind tRNA gene transcription complexes and are required for tgm silencing but not required for gene clustering. One of the proteins, Mod5, is a tRNA modifying enzyme that adds an N6-isopentenyl adenosine modification at position 37 on a small number of tRNAs in the cytoplasm, although a subpopulation of Mod5 is also found in the nucleus. Recent publications have also shown that Mod5 has tumor suppressor characteristics in humans as well as confers drug resistance through prion-like misfolding in yeast. Here, we show that a subpopulation of Mod5 associates with tRNA gene complexes in the nucleolus. This association occurs and is required for tgm silencing regardless of whether the pre-tRNA transcripts are substrates for Mod5 modification. In addition, Mod5 is bound to nuclear pre-tRNA transcripts, although they are not substrates for the A37 modification. Lastly, we show that truncation of the tRNA transcript to remove the normal tRNA structure also alleviates silencing, suggesting that synthesis of intact pre-tRNAs is required for the silencing mechanism. These results are discussed in light of recent results showing that silencing near tRNA genes also requires chromatin modification. PMID:23898186

Pratt-Hyatt, Matthew; Pai, Dave A; Haeusler, Rebecca A; Wozniak, Glenn G; Good, Paul D; Miller, Erin L; McLeod, Ian X; Yates, John R; Hopper, Anita K; Engelke, David R

2013-07-29

157

Manipulation of Cell Physiology Enables Gene Silencing in Well-differentiated Airway Epithelia  

PubMed Central

The application of RNA interference-based gene silencing to the airway surface epithelium holds great promise to manipulate host and pathogen gene expression for therapeutic purposes. However, well-differentiated airway epithelia display significant barriers to double-stranded small-interfering RNA (siRNA) delivery despite testing varied classes of nonviral reagents. In well-differentiated primary pig airway epithelia (PAE) or human airway epithelia (HAE) grown at the air–liquid interface (ALI), the delivery of a Dicer-substrate small-interfering RNA (DsiRNA) duplex against hypoxanthine–guanine phosphoribosyltransferase (HPRT) with several nonviral reagents showed minimal uptake and no knockdown of the target. In contrast, poorly differentiated cells (2–5-day post-seeding) exhibited significant oligonucleotide internalization and target knockdown. This finding suggested that during differentiation, the barrier properties of the epithelium are modified to an extent that impedes oligonucleotide uptake. We used two methods to overcome this inefficiency. First, we tested the impact of epidermal growth factor (EGF), a known enhancer of macropinocytosis. Treatment of the cells with EGF improved oligonucleotide uptake resulting in significant but modest levels of target knockdown. Secondly, we used the connectivity map (Cmap) database to correlate gene expression changes during small molecule treatments on various cells types with genes that change upon mucociliary differentiation. Several different drug classes were identified from this correlative assessment. Well-differentiated epithelia treated with DsiRNAs and LY294002, a PI3K inhibitor, significantly improved gene silencing and concomitantly reduced target protein levels. These novel findings reveal that well-differentiated airway epithelia, normally resistant to siRNA delivery, can be pretreated with small molecules to improve uptake of synthetic oligonucleotide and RNA interference (RNAi) responses.

Krishnamurthy, Sateesh; Behlke, Mark A; Ramachandran, Shyam; Salem, Aliasger K; McCray Jr, Paul B; Davidson, Beverly L

2012-01-01

158

Virus-induced gene silencing of Arabidopsis thaliana gene homologues in wheat identifies genes conferring improved drought tolerance.  

PubMed

In a non-model staple crop like wheat (Triticum aestivumI L.), functional validation of potential drought stress responsive genes identified in Arabidopsis could provide gene targets for breeding. Virus-induced gene silencing (VIGS) of genes of interest can overcome the inherent problems of polyploidy and limited transformation potential that hamper functional validation studies in wheat. In this study, three potential candidate genes shown to be involved in abiotic stress response pathways in Arabidopsis thaliana were selected for VIGS experiments in wheat. These include Era1 (enhanced response to abscisic acid), Cyp707a (ABA 8'-hydroxylase), and Sal1 (inositol polyphosphate 1-phosphatase). Gene homologues for these three genes were identified in wheat and cloned in the viral vector barley stripe mosaic virus (BSMV) in the antisense direction, followed by rub inoculation of BSMV viral RNA transcripts onto wheat plants. Quantitative real-time PCR showed that VIGS-treated wheat plants had significant reductions in target gene transcripts. When VIGS-treated plants generated for Era1 and Sal1 were subjected to limiting water conditions, they showed increased relative water content, improved water use efficiency, reduced gas exchange, and better vigour compared to water-stressed control plants inoculated with RNA from the empty viral vector (BSMV0). In comparison, the Cyp707a-silenced plants showed no improvement over BSMV0-inoculated plants under limited water condition. These results indicate that Era1 and Sal1 play important roles in conferring drought tolerance in wheat. Other traits affected by Era1 silencing were also studied. Delayed seed germination in Era1-silenced plants suggests this gene may be a useful target for developing resistance to pre-harvest sprouting. PMID:23364940

Manmathan, Harish; Shaner, Dale; Snelling, Jacob; Tisserat, Ned; Lapitan, Nora

2013-01-30

159

Virus-induced gene silencing of Arabidopsis thaliana gene homologues in wheat identifies genes conferring improved drought tolerance  

PubMed Central

In a non-model staple crop like wheat (Triticum aestivumI L.), functional validation of potential drought stress responsive genes identified in Arabidopsis could provide gene targets for breeding. Virus-induced gene silencing (VIGS) of genes of interest can overcome the inherent problems of polyploidy and limited transformation potential that hamper functional validation studies in wheat. In this study, three potential candidate genes shown to be involved in abiotic stress response pathways in Arabidopsis thaliana were selected for VIGS experiments in wheat. These include Era1 (enhanced response to abscisic acid), Cyp707a (ABA 8’-hydroxylase), and Sal1 (inositol polyphosphate 1-phosphatase). Gene homologues for these three genes were identified in wheat and cloned in the viral vector barley stripe mosaic virus (BSMV) in the antisense direction, followed by rub inoculation of BSMV viral RNA transcripts onto wheat plants. Quantitative real-time PCR showed that VIGS-treated wheat plants had significant reductions in target gene transcripts. When VIGS-treated plants generated for Era1 and Sal1 were subjected to limiting water conditions, they showed increased relative water content, improved water use efficiency, reduced gas exchange, and better vigour compared to water-stressed control plants inoculated with RNA from the empty viral vector (BSMV0). In comparison, the Cyp707a-silenced plants showed no improvement over BSMV0-inoculated plants under limited water condition. These results indicate that Era1 and Sal1 play important roles in conferring drought tolerance in wheat. Other traits affected by Era1 silencing were also studied. Delayed seed germination in Era1-silenced plants suggests this gene may be a useful target for developing resistance to pre-harvest sprouting.

Lapitan, Nora

2013-01-01

160

tRNA genes protect a reporter gene from epigenetic silencing in mouse cells  

PubMed Central

It is a well-established fact that the tRNA genes in yeast can function as chromatin barrier elements. However, so far there is no experimental evidence that tRNA and other Pol III-transcribed genes exhibit barrier activity in mammals. This study utilizes a recently developed reporter gene assay to test a set of Pol III-transcribed genes and gene clusters with variable promoter and intergenic regions for their ability to prevent heterochromatin-mediated reporter gene silencing in mouse cells. The results show that functional copies of mouse tRNA genes are effective barrier elements. The number of tRNA genes as well as their orientation influence barrier function. Furthermore, the DNA sequence composition of intervening and flanking regions affects barrier activity of tRNA genes. Barrier activity was maintained for much longer time when the intervening and flanking regions of tRNA genes were replaced by AT-rich sequences, suggesting a negative role of DNA methylation in the establishment of a functional barrier. Thus, our results suggest that tRNA genes are essential elements in establishment and maintenance of chromatin domain architecture in mammalian cells.

Ebersole, Thomas; Kim, Jung-Hyun; Samoshkin, Alexander; Kouprina, Natalay; Pavlicek, Adam; White, Robert J

2011-01-01

161

Localized methylation in the key regulator gene endothelin- 1 is associated with cell type-specific transcriptional silencing  

Microsoft Academic Search

DNA methylation can contribute to the stable transcriptional silencing of mammalian genes. Often times, these genes are important developmental regulators, and their silencing in cell types where they are not supposed to be active is important for the phenotypic stability of the cells. To identify key developmental regulator genes whose expression in terminally differentiated cells may be inhibited by DNA

Tammy W. Vallender; Bruce T. Lahn

2006-01-01

162

Polyethyleneimine (PEI) Mediated siRNA Gene Silencing in the Schistosoma mansoni Snail Host, Biomphalaria glabrata  

PubMed Central

An in vivo, non-invasive technique for gene silencing by RNA interference (RNAi) in the snail, Biomphalaria glabrata, has been developed using cationic polymer polyethyleneimine (PEI) mediated delivery of long double-stranded (ds) and small interfering (si) RNA. Cellular delivery was evaluated and optimized by using a ‘mock’ fluorescent siRNA. Subsequently, we used the method to suppress expression of Cathepsin B (CathB) with either the corresponding siRNA or dsRNA of this transcript. In addition, the knockdown of peroxiredoxin (Prx) at both RNA and protein levels was achieved with the PEI-mediated soaking method. B. glabrata is an important snail host for the transmission of the parasitic digenean platyhelminth, Schistosoma mansoni that causes schistosomiasis in the neotropics. Progress is being made to realize the genome sequence of the snail and to uncover gene expression profiles and cellular pathways that enable the snail to either prevent or sustain an infection. Using PEI complexes, a convenient soaking method has been developed, enabling functional gene knockdown studies with either dsRNA or siRNA. The protocol developed offers a first whole organism method for host-parasite gene function studies needed to identify key mechanisms required for parasite development in the snail host, which ultimately are needed as points for disrupting this parasite mediated disease.

Knight, Matty; Miller, Andre; Liu, Yijia; Scaria, Puthupparampil; Woodle, Martin; Ittiprasert, Wannaporn

2011-01-01

163

Immune responses to dsRNA: Implications for gene silencing technologies  

Microsoft Academic Search

Nucleic acid-induced gene silencing, such as RNA interference (RNAi), induces a multitude of responses in addition to the knockdown of a gene. This is best understood in the context of the antiviral immune response, from which the processes of RNAi are thought to be derived. Viral challenge of a vertebrate host leads to an intricate series of responses that orchestrate

Adam J Karpala; Tim J Doran; Andrew GD Bean

2005-01-01

164

Artificial micro RNA (amiRNA) induced gene silencing in alfalfa (Medicago sativa)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Gene silencing is a powerful technique that allows the study of the function of specific genes by selectively reducing their transcription. Several different approaches can be used; however, they all have in common the artificial generation of single-stranded small RNAs that are utilized by the endo...

165

Chalcone synthase as a reporter in virus-induced gene silencing studies of flower senescence  

Microsoft Academic Search

Agrobacterium-mediatedinfection of petunia (Petunia hybrida) plants with tobacco rattle virus (TRV) bearing fragments of Petuniagenes resulted in systemic infection and virus-induced gene silencing (VIGS) of the homologous host genes. Infection with TRV containing a phytoene desaturase (PDS) fragment resulted in reduced abundance of PDS transcripts and typical photobleaching of photosynthetic tissues. Infection with TRV containing a chalcone synthase (CHS) fragment

Jen-Chih Chen; Cai-Zhong Jiang; Timothy E. Gookin; Donald A. Hunter; David G. Clark; Michael S. Reid

2004-01-01

166

Autonomous Silencing as Well as Competition Controls ?-Globin Gene Expression during Development  

PubMed Central

To investigate the control of the ?-globin gene during development, we produced transgenic mice in which sequences of the ?-gene promoter were replaced by equivalent sequences of the ?-gene promoter in the context of a human ?-globin locus yeast artificial chromosome (?YAC) and analyzed the effects on globin gene expression during development. Replacement of 1,077 nucleotides (nt) of the ?-gene promoter by 1,359 nt of the ? promoter resulted in striking inhibition of the ?-promoter/?-gene expression in the adult stage of development, providing direct evidence that the expression of the ? gene in the adult is mainly controlled by autonomous silencing. Measurements of the expression of the ? promoter/?-globin gene as well as the wild ? genes showed that gene competition is also involved in the control of ?-gene expression in the fetal stage of development. We conclude that autonomous silencing is the main mechanism controlling ?-gene expression in the adult, while autonomous silencing as well as competition between ? and ? genes contributes to the control of ? to ? switching during fetal development.

Yu, Man; Han, Hemei; Xiang, Ping; Li, Qiliang; Stamatoyannopoulos, George

2006-01-01

167

Genomic screening for genes upregulated by demethylation revealed novel targets of epigenetic silencing in breast cancer  

Microsoft Academic Search

Breast cancer arises through the accumulation of multiple genetic alterations and epigenetic changes such as methylation,\\u000a which silences gene expression in a variety of cancers. In the present study, we applied genomic screening to identify genes\\u000a upregulated by the demethylating agent 5-aza-2?-deoxycytidine (DAC) in a human breast cancer cell line (MCF7). We identified\\u000a 288 genes upregulated and 29 genes downregulated

Tomoko Fujikane; Noriko Nishikawa; Minoru Toyota; Hiromu Suzuki; Masanori Nojima; Reo Maruyama; Masami Ashida; Mutsumi Ohe-Toyota; Masahiro Kai; Toshihiko Nishidate; Yasushi Sasaki; Tousei Ohmura; Koichi Hirata; Takashi Tokino

2010-01-01

168

Dissection of Tomato Lycopene Biosynthesis through Virus-Induced Gene Silencing1[C][W][OPEN  

PubMed Central

Lycopene biosynthesis in tomato (Solanum lycopersicum) fruits has been proposed to proceed through a poly-cis pathway catalyzed by phytoene synthase (PSY), two desaturases (phytoene desaturase [PDS] and ?-carotene desaturase [ZDS]), and two cis-trans isomerases (?-carotene isomerase [ZISO] and prolycopene isomerase [CrtISO]). The mechanism of action of these enzymes has been studied in Escherichia coli, but a systematic study of their in vivo function is lacking. We studied the function of nine candidate genes (PSY1, PSY2, PSY3, PDS, ZDS, ZISO, CrtISO, CrtISO-Like1, and CrtISO-Like2) using virus-induced gene silencing (VIGS) coupled to high-resolution liquid chromatography coupled with diode array detector and mass spectrometry, which allowed the identification and quantitation of 45 different carotenoid isomers, including linear xanthophylls. The data confirm the confinement of the VIGS signal to the silenced fruits and the similarity of the phenotypes of PSY1- and CrtISO-silenced fruits with those of the yellow flesh and tangerine mutants. Light was able to restore lycopene biosynthesis in ZISO-silenced fruits. Isomeric composition of fruits silenced at different metabolic steps suggested the existence of three functional units, comprising PSY1, PDS/ZISO, and ZDS/CrtISO, and responsible for the synthesis of 15-cis-phytoene, 9,9’-di-cis-?-carotene, and all-trans-lycopene, respectively. Silencing of a desaturase (PDS or ZDS) resulted in the induction of the isomerase in the same functional unit (ZISO or CrtISO, respectively). All-trans-?-carotene was detectable in nonsilenced fruits, greatly increased in ZDS-silenced ones, and disappeared in CrtISO-Like1-/CrtISO-Like2-silenced ones, suggesting the existence of a metabolic side branch, comprising this compound and initiated by the latter enzymes.

Fantini, Elio; Falcone, Giulia; Frusciante, Sarah; Giliberto, Leonardo; Giuliano, Giovanni

2013-01-01

169

Virus-induced gene silencing (VIGS) in Cysticapnos vesicaria, a zygomorphic-flowered Papaveraceae (Ranunculales, basal eudicots)  

PubMed Central

Background and Aims Studies of evolutionary diversification in the basal eudicot family Papaveraceae, such as the transition from actinomorphy to zygomorphy, are hampered by the lack of comparative functional studies. So far, gene silencing methods are only available in the actinomorphic species Eschscholzia californica and Papaver somniferum. This study addresses the amenability of Cysticapnos vesicaria, a derived fumitory with zygomorphic flowers, to virus-induced gene silencing (VIGS), and describes vegetative and reproductive traits in this species. Methods VIGS-mediated downregulation of the C. vesicaria PHYTOENE DESATURASE gene (CvPDS) and of the FLORICAULA gene CvFLO was carried out using Agrobacterium tumefaciens transfer of Tobacco rattle virus (TRV)-based vectors. Wild-type and vector-treated plants were characterized using reverse transcription–PCR (RT–PCR), in situ hybridization, and macroscopic and scanning electron microscopic imaging. Key Results Cysticapnos vesicaria germinates rapidly, can be grown at high density, has a short life cycle and is self-compatible. Inoculation of C. vesicaria with a CvPDS-VIGS vector resulted in strong photobleaching of green parts and reduction of endogenous CvPDS transcript levels. Gene silencing persisted during inflorescence development until fruit set. Inoculation of plants with CvFLO-VIGS affected floral phyllotaxis, symmetry and floral organ identities. Conclusions The high penetrance, severity and stability of pTRV-mediated silencing, including the induction of meristem-related phenotypes, make C. vesicaria a very promising new focus species for evolutionary–developmental (evo–devo) studies in the Papaveraceae. This now enables comparative studies of flower symmetry, inflorescence determinacy and other traits that diversified in the Papaveraceae.

Hidalgo, Oriane; Bartholmes, Conny; Gleissberg, Stefan

2012-01-01

170

Enhancement of virus-induced gene silencing through viral-based production of inverted-repeats.  

PubMed

Plant virus-based vectors carrying sequences homologous to endogenous genes trigger silencing through a homology-dependent RNA degradation mechanism. This phenomenon, called virus-induced gene silencing (VIGS), has potential as a powerful reverse-genetics tool in functional genomic programmes through transient, loss-of-function screens. Here, we describe a method to enhance the robustness of the VIGS phenotype by increasing the level of dsRNA molecule production, a critical step in the VIGS response. Incorporation of 40-60 base direct inverted-repeats into a plant viral vector generates RNA molecules that form dsRNA hairpins. A tobacco mosaic virus (TMV)-based vector carrying such inverted-repeats, homologous to a green fluorescent protein (gfp) transgene or an endogenous phytoene desaturase (pds) gene, generated a stronger and more pervasive VIGS phenotype than constructs carrying corresponding cDNA fragments in sense or antisense orientation. Real-time RT-PCR indicated that there was up to a threefold reduction in target mRNA accumulation in the tissues where VIGS was triggered by constructs carrying inverted-repeats compared to those where it was triggered by sense or antisense constructs. Moreover, an enhanced VIGS pds phenotype was observed using a different vector, based on barley stripe mosaic virus, in the monocotyledonous host barley. This demonstrates that VIGS can be significantly improved through the inclusion of small inverted-repeats in plant virus-based vectors, generating a more robust loss-of-function phenotype. This suggests that dsRNA formation can be a limiting factor in the VIGS phenomenon. PMID:12753592

Lacomme, Christophe; Hrubikova, Katarina; Hein, Ingo

2003-05-01

171

DNA methylation in cancer: a gene silencing mechanism and the clinical potential of its biomarkers.  

PubMed

Initiation and progression of human cancer not only depends on genetic alterations but also on epigenetic changes such as DNA methylation and histone modifications. Aberrant DNA hypermethylation in the promoter regions of genes is the most well-defined epigenetic change in tumors and is associated with inappropriate gene silencing. This feature can be utilized to search for tumor-specific DNA methylation biomarkers and to examine candidate DNA biomarkers for clinical use. DNA methylation biomarker is defined as a molecular target that undergoes DNA methylation changes in carcinogenesis. Such a biomarker is useful for early detection of cancer, predicting and/or monitoring the therapeutic response, and detection of recurrent cancer. In this review, we describe the mechanism that establishes and maintains DNA methylation patterns as well as the mechanism of aberrant gene silencing in cancer, and then we introduce methods to isolate the DNA methylation biomarkers. We also summarize the current status of clinical implementation for some of the most widely studied and well-validated DNA methylation biomarkers, including tissue factor pathway inhibitor 2 (TFPI2), septin 9 (SEPT9), glutathione S-transferase pi 1 (GSTP1), and O(6)-methylguanine-DNA methyltransferase (MGMT), and assess the clinical potential of these biomarkers for risk assessment, early diagnosis, prognosis, treatment, and the prevention of cancer. Finally we describe the possible involvement of 5-hydroxymethylcytosine in cancer; this is a recently discovered 5-methylcytosine oxidation derivative and might have a diagnostic potential in certain cancers. Abnormal DNA methylations are leading candidates for the development of specific markers for cancer diagnosis and therapy. PMID:23419314

Fukushige, Shinichi; Horii, Akira

2013-01-01

172

Silencing of Host Genes Directed by Virus-Derived Short Interfering RNAs in Caenorhabditis elegans  

PubMed Central

Small interfering RNAs (siRNAs) processed from viral replication intermediates by RNase III-like enzyme Dicer guide sequence-specific antiviral silencing in fungi, plants, and invertebrates. In plants, virus-derived siRNAs (viRNAs) can target and silence cellular transcripts and, in some cases, are responsible for the induction of plant diseases. Currently it remains unclear whether viRNAs are also capable of modulating the expression of cellular genes in the animal kingdom, although animal virus-encoded microRNAs (miRNAs) are known to guide efficient silencing of host genes, thereby facilitating virus replication. In this report, we showed that viRNAs derived from a modified nodavirus triggered potent silencing of homologous cellular transcripts produced by the endogenous gene or transgene in the nematode worm Caenorhabditis elegans. Like that found in plants, virus-induced gene silencing (VIGS) in C. elegans also involves RRF-1, a worm RNA-dependent RNA polymerase (RdRP) that is known to produce single-stranded secondary siRNAs in a Dicer-independent manner. We further demonstrated that VIGS in C. elegans is inheritable, suggesting that VIGS has the potential to generate profound epigenetic consequences in future generations. Altogether, these findings, for the first time, confirmed that viRNAs have the potential to modulate host gene expression in the animal kingdom. Most importantly, the success in uncoupling the trigger and the target of the antiviral silencing would allow for the exploration of novel features of virus-host interactions mediated by viRNAs in the animal kingdom.

Guo, Xunyang; Li, Wan-Xiang

2012-01-01

173

Tethering RITS to a nascent transcript initiates RNAi- and heterochromatin-dependent gene silencing.  

PubMed

In the fission yeast Schizosaccharomyces pombe, the RNA-Induced Transcriptional Silencing (RITS) complex has been proposed to target the chromosome via siRNA-dependent base-pairing interactions to initiate heterochromatin formation. Here we show that tethering of the RITS subunit, Tas3, to the RNA transcript of the normally active ura4+ gene silences ura4+ expression. This silencing depends on a functional RNAi pathway, requires the heterochromatin proteins, Swi6/HP1, Clr4/Suv39h, and Sir2, and is accompanied by the generation of ura4+ siRNAs, histone H3-lysine 9 methylation, and Swi6 binding. Furthermore, the ability of the newly generated ura4+ siRNAs to silence a second ura4+ allele in trans is strongly inhibited by the conserved siRNA nuclease, Eri1. Surprisingly, silencing of tethered ura4+, or ura4+ inserted within centromeric heterochromatin, or some of the endogenous centromeric repeat promoters, is not associated with changes in RNA polymerase II occupancy. These findings support a model in which targeting of nascent transcripts by RITS mediates chromatin modifications and suggest that cotranscriptional processing events play a primary role in the silencing mechanism. PMID:16751098

Bühler, Marc; Verdel, André; Moazed, Danesh

2006-06-01

174

Dosage Compensation in the Mouse Balances Up-Regulation and Silencing of X-Linked Genes  

PubMed Central

Dosage compensation in mammals involves silencing of one X chromosome in XX females and requires expression, in cis, of Xist RNA. The X to be inactivated is randomly chosen in cells of the inner cell mass (ICM) at the blastocyst stage of development. Embryonic stem (ES) cells derived from the ICM of female mice have two active X chromosomes, one of which is inactivated as the cells differentiate in culture, providing a powerful model system to study the dynamics of X inactivation. Using microarrays to assay expression of X-linked genes in undifferentiated female and male mouse ES cells, we detect global up-regulation of expression (1.4- to 1.6-fold) from the active X chromosomes, relative to autosomes. We show a similar up-regulation in ICM from male blastocysts grown in culture. In male ES cells, up-regulation reaches 2-fold after 2–3 weeks of differentiation, thereby balancing expression between the single X and the diploid autosomes. We show that silencing of X-linked genes in female ES cells occurs on a gene-by-gene basis throughout differentiation, with some genes inactivating early, others late, and some escaping altogether. Surprisingly, by allele-specific analysis in hybrid ES cells, we also identified a subgroup of genes that are silenced in undifferentiated cells. We propose that X-linked genes are silenced in female ES cells by spreading of Xist RNA through the X chromosome territory as the cells differentiate, with silencing times for individual genes dependent on their proximity to the Xist locus.

Lin, Hong; Gupta, Vibhor; VerMilyea, Matthew D; Falciani, Francesco; Lee, Jeannie T; O'Neill, Laura P; Turner, Bryan M

2007-01-01

175

Gene silencing in root lesion nematodes (Pratylenchus spp.) significantly reduces reproduction in a plant host.  

PubMed

Root lesion nematodes (RLNs, Pratylenchus species) are a group of economically important migratory endoparasitic plant pathogens that attack host roots of major crops such as wheat and sugarcane, and can reduce crop yields by 7-15%. Pratylenchus thornei and Pratylenchus zeae were treated with double stranded RNA (dsRNA) to study gene silencing, (RNA interference, RNAi), as a potential strategy for their control. Mixed stages of nematodes of both species ingested dsRNA when incubated in a basic soaking solution in the presence of the neurostimulant octopamine. Incubation for up to 16 h in soaking solutions containing 10-50 mM octopamine, 0.1-1.0 mg/mL FITC, and 0.5-6 mM spermidine did not affect vitality. Spermidine phosphate salt hexahydrate rather than spermidine or spermidine trihydrochloride increased uptake of FITC by nematodes, and this resulted in more effective gene silencing. Silencing pat-10 and unc-87 genes of P. thornei and P. zeae resulted in paralysis and uncoordinated movements in both species, although to a higher degree in P. thornei. There was also a greater reduction in transcript of both genes in P. thornei indicating that it may be more susceptible to RNAi. For P. thornei treated with dsRNA of pat-10 and unc-87 there was a significant reduction (77-81%) in nematode reproduction on carrot mini discs over a 5 week period. The results show that RLNs are clearly amenable to gene silencing, and that in planta delivery of dsRNA to target genes in these nematodes should confer host resistance. Moreover, for the two genes, dsRNA derived from either nematode species silenced the corresponding gene in both species. This implies cross-species control of nematodes via RNAi is possible. PMID:23201220

Tan, Jo-Anne C H; Jones, Michael G K; Fosu-Nyarko, John

2012-11-29

176

ADAM33 gene silencing by promoter hypermethylation as a molecular marker in breast invasive lobular carcinoma  

PubMed Central

Background ADAM33 protein is a member of the family of transmembrane glycoproteins composed of multidomains. ADAM family members have different activities, such as proteolysis and adhesion, making them good candidates to mediate the extracellular matrix remodelling and changes in cellular adhesion that characterise certain pathologies and cancer development. It was reported that one family member, ADAM23, is down-regulated by promoter hypermethylation. This seems to correlate with tumour progression and metastasis in breast cancer. In this study, we explored the involvement of ADAM33, another ADAM family member, in breast cancer. Methods First, we analysed ADAM33 expression in breast tumour cell lines by RT-PCR and western blotting. We also used 5-aza-2'-deoxycytidine (5azadCR) treatment and DNA bisulphite sequencing to study the promoter methylation of ADAM33 in breast tumour cell lines. We evaluated ADAM33 methylation in primary tumour samples by methylation specific PCR (MSP). Finally, ADAM33 promoter hypermethylation was correlated with clinicopathological data using the chi-square test and Fisher's exact test. Results The expression analysis of ADAM33 in breast tumour cell lines by RT-PCR revealed gene silencing in 65% of tumour cell lines. The corresponding lack of ADAM33 protein was confirmed by western blotting. We also used 5-aza-2'-deoxycytidine (5-aza-dCR) demethylation and bisulphite sequencing methodologies to confirm that gene silencing is due to ADAM33 promoter hypermethylation. Using MSP, we detected ADAM33 promoter hypermethylation in 40% of primary breast tumour samples. The correlation between methylation pattern and patient's clinicopathological data was not significantly associated with histological grade; tumour stage (TNM); tumour size; ER, PR or ERBB2 status; lymph node status; metastasis or recurrence. Methylation frequency in invasive lobular carcinoma (ILC) was 76.2% compared with 25.5% in invasive ductal carcinoma (IDC), and this difference was statistically significant (p = 0.0002). Conclusion ADAM33 gene silencing may be related to the discohesive histological appearance of ILCs. We suggest that ADAM33 promoter methylation may be a useful molecular marker for differentiating ILC and IDC.

2009-01-01

177

Gene silencing in X-chromosome inactivation: advances in understanding facultative heterochromatin formation.  

PubMed

In female mammals, one of the two X chromosomes is silenced for dosage compensation between the sexes. X-chromosome inactivation is initiated in early embryogenesis by the Xist RNA that localizes to the inactive X chromosome. During development, the inactive X chromosome is further modified, a specialized form of facultative heterochromatin is formed and gene repression becomes stable and independent of Xist in somatic cells. The recent identification of several factors involved in this process has provided insights into the mechanism of Xist localization and gene silencing. The emerging picture is complex and suggests that chromosome-wide silencing can be partitioned into several steps, the molecular components of which are starting to be defined. PMID:21765457

Wutz, Anton

2011-07-18

178

Double-stranded RNA-mediated gene silencing in fission yeast  

Microsoft Academic Search

Double-stranded RNA (dsRNA) can specifically inhibit gene expression in a variety of organisms by invoking post-transcriptional degradation of homo- logous mRNA. Here we show that dsRNA-mediated gene regulation also occurs in the fission yeast Schizosaccharomyces pombe. We present evidence that: (i) reporter gene silencing is significantly enhanced when additional non-coding sense RNA is co-expressed with antisense RNA; (ii) expression of

Mitch Raponi; Greg M. Arndt

2003-01-01

179

Critical Role of Histone Methylation in Tumor Suppressor Gene Silencing in Colorectal Cancer  

Microsoft Academic Search

The mechanism of DNA hypermethylation-associated tumor suppressor gene silencing in cancer remains incompletely understood. Here, we show by chromatin immunoprecipitation that for three genes (P16, MLH1, and the O6-methylguanine-DNA methyltransferase gene, MGMT), histone H3 Lys-9 methylation directly correlates and histone H3 Lys-9 acetylation inversely correlates with DNA methylation in three neoplastic cell lines. Treatment with the histone deacetylase inhibitor trichostatin

Yutaka Kondo; LanLan Shen; Jean-Pierre J. Issa

2003-01-01

180

Virus-induced gene silencing of the alkaloid-producing basal eudicot model plant Eschscholzia californica (California Poppy).  

PubMed

Eschscholzia californica (California poppy), a member of the basal eudicot family of the Papaveraceae, is an important species to study alkaloid biosynthesis and the effect of alkaloids on plant metabolism. More recently, it has also been developed as a model system to study the evolution of plant morphogenesis. While progress has been made towards establishing methods for generating genetically modified cell culture lines, transcriptome data and gene expression analysis, the stable transformation and subsequent regeneration of transgenic plants has proven extremely time consuming and difficult. Here, we describe in detail a method to transiently down regulate expression of a target gene by virus-induced gene silencing (VIGS) and the subsequent analysis of the VIGS treated plants. VIGS in E. californica allows for the study of gene function within 2 to 3 weeks after inoculation, and the method proves very efficient, enabling the rapid analysis of gene functions. PMID:23386297

Tekleyohans, Dawit G; Lange, Sabrina; Becker, Annette

2013-01-01

181

Elucidation of the functions of genes central to diterpene metabolism in tobacco trichomes using posttranscriptional gene silencing  

Microsoft Academic Search

The functions of two key, trichome-expressed genes were assessed using different posttranscriptional gene silencing strategies (PTGS). Efficient RNA interference (RNAi) revealed the function of a cembratriene-ol (CBT-ol) cyclase gene responsible for conversion of geranylgeranyl pyrophosphate to CBT-ols, and verified the function of a P450 gene responsible for conversion of CBT-ols to CBT-diols. CBT-diols are abundant diterpenes that comprise about 60%

Erming Wang; George J. Wagner

2003-01-01

182

Gene dosage induction of silencing directed against an Arabidopsis Myb transgene in tobacco  

Technology Transfer Automated Retrieval System (TEKTRAN)

An unexpected reduction in petal pigmentation on petunia plants genetically engineered for enhanced flower color was one of the first experimental demonstrations of the natural process of RNA-associated gene silencing. The obvious visual nature of such alterations to pigment patterns of transgenic ...

183

Cell-free construction of disarmed Abutilon mosaic virus-based gene silencing vectors  

Microsoft Academic Search

The bipartite Abutilon mosaic virus (AbMV) was engineered as a versatile silencing vector in which the coat protein gene of DNA A was deleted and replaced by sequences of interest. Plants transgenic for the dimeric AbMV DNA B component were used as test hosts to minimize the risk of unintended release of the recombinant DNA. The vector construct was stable

Björn Krenz; Christina Wege; Holger Jeske

2010-01-01

184

Suppression of Gene Silencing: A General Strategy Used by Diverse DNA and RNA Viruses of Plants  

Microsoft Academic Search

In transgenic and nontransgenic plants, viruses are both initiators and targets of a defense mechanism that is similar to posttranscriptional gene silencing (PTGS). Recently, it was found that potyviruses and cucumoviruses encode pathogenicity determinants that suppress this defense mechanism. Here, we test diverse virus types for the ability to suppress PTGS. Nicotiana benthamiana exhibiting PTGS of a green fluorescent protein

Olivier Voinnet; Yvonne M. Pinto; David C. Baulcombe

1999-01-01

185

In vivo gene silencing in Plasmodium berghei—a mouse malaria model  

Microsoft Academic Search

RNA interference (RNAi) has emerged as a specific and efficient tool to silence gene expression in a variety of organisms and cell lines. An important prospect for RNAi technology is its possible application in the treatment of diseases using short interfering RNAs (siRNAs). However, the effect of siRNAs in adult animals and their potential to treat or prevent diseases are

Asif Mohmmed; Palakodeti V. N Dasaradhi; Raj K Bhatnagar; Virander S Chauhan; Pawan Malhotra

2003-01-01

186

BIOFILTRATION INCORPORATING GENE SILENCING TECHNOLOGY FOR THE PRODUCTION OF METHANOL FROM METHANE CONTAINING WASTE GASES  

EPA Science Inventory

I expect the proposed and revised approach will work, as there are multiple examples of plasmid-based gene silencing systems in nature (HOK/SOK is a perfect example). The challenge will be in developing a strong plasmid for use in methanotrophs. Potential to ...

187

DNMT1 and DNMT3b cooperate to silence genes in human cancer cells  

Microsoft Academic Search

Inactivation of tumour suppressor genes is central to the development of all common forms of human cancer. This inactivation often results from epigenetic silencing associated with hypermethylation rather than intragenic mutations. In human cells, the mechanisms underlying locus-specific or global methylation patterns remain unclear. The prototypic DNA methyltransferase, Dnmt1, accounts for most methylation in mouse cells, but human cancer cells

Ina Rhee; Kurtis E. Bachman; Ben Ho Park; Kam-Wing Jair; Ray-Whay Chiu Yen; Kornel E. Schuebel; Hengmi Cui; Andrew P. Feinberg; Christoph Lengauer; Kenneth W. Kinzler; Stephen B. Baylin; Bert Vogelstein

2002-01-01

188

Gene silencing in X-chromosome inactivation: advances in understanding facultative heterochromatin formation  

Microsoft Academic Search

In female mammals, one of the two X chromosomes is silenced for dosage compensation between the sexes. X-chromosome inactivation is initiated in early embryogenesis by the Xist RNA that localizes to the inactive X chromosome. During development, the inactive X chromosome is further modified, a specialized form of facultative heterochromatin is formed and gene repression becomes stable and independent of

Anton Wutz

2011-01-01

189

Fox Chase researchers identify new mechanism used by cells to reverse silenced genes:  

Cancer.gov

Scientists at Fox Chase Cancer Center have discovered a new mechanism used by cells in the body to turn on silenced genes. This process is critical in preventing the development of cancer—suggesting the possibility of new therapies that might target the specific changes underlying the disease.

190

Mi2?-mediated silencing of the fetal ?-globin gene in adult erythroid cells.  

PubMed

An understanding of the human fetal to adult hemoglobin switch offers the potential to ameliorate ?-type globin gene disorders such as sickle cell anemia and ?-thalassemia through activation of the fetal ?-globin gene. Chromatin modifying complexes, including MBD2-NuRD and GATA-1/FOG-1/NuRD, play a role in ?-globin gene silencing, and Mi2? (CHD4) is a critical component of NuRD complexes. We observed that knockdown of Mi2? relieves ?-globin gene silencing in ?-YAC transgenic murine chemical inducer of dimerization hematopoietic cells and in CD34(+) progenitor-derived human primary adult erythroid cells. We show that independent of MBD2-NuRD and GATA-1/FOG-1/NuRD, Mi2? binds directly to and positively regulates both the KLF1 and BCL11A genes, which encode transcription factors critical for ?-globin gene silencing during ?-type globin gene switching. Remarkably, <50% knockdown of Mi2? is sufficient to significantly induce ?-globin gene expression without disrupting erythroid differentiation of primary human CD34(+) progenitors. These results indicate that Mi2? is a potential target for therapeutic induction of fetal hemoglobin. PMID:23444401

Amaya, Maria; Desai, Megha; Gnanapragasam, Merlin Nithya; Wang, Shou Zhen; Zu Zhu, Sheng; Williams, David C; Ginder, Gordon D

2013-02-26

191

Mi2?-mediated silencing of the fetal ?-globin gene in adult erythroid cells  

PubMed Central

An understanding of the human fetal to adult hemoglobin switch offers the potential to ameliorate ?-type globin gene disorders such as sickle cell anemia and ?-thalassemia through activation of the fetal ?-globin gene. Chromatin modifying complexes, including MBD2-NuRD and GATA-1/FOG-1/NuRD, play a role in ?-globin gene silencing, and Mi2? (CHD4) is a critical component of NuRD complexes. We observed that knockdown of Mi2? relieves ?-globin gene silencing in ?-YAC transgenic murine chemical inducer of dimerization hematopoietic cells and in CD34+ progenitor-derived human primary adult erythroid cells. We show that independent of MBD2-NuRD and GATA-1/FOG-1/NuRD, Mi2? binds directly to and positively regulates both the KLF1 and BCL11A genes, which encode transcription factors critical for ?-globin gene silencing during ?-type globin gene switching. Remarkably, <50% knockdown of Mi2? is sufficient to significantly induce ?-globin gene expression without disrupting erythroid differentiation of primary human CD34+ progenitors. These results indicate that Mi2? is a potential target for therapeutic induction of fetal hemoglobin.

Amaya, Maria; Desai, Megha; Gnanapragasam, Merlin Nithya; Wang, Shou Zhen; Zu Zhu, Sheng; Williams, David C.

2013-01-01

192

DNA-intercalators Causing Rapid Re-expression of Methylated and Silenced Genes in Cancer Cells  

PubMed Central

Epigenetic inactivation of tumor-suppressor and other regulatory genes plays a critical role in carcinogenesis. Transcriptional silencing is often maintained by DNA methyl transferase (DNMT)-mediated hypermethylation of CpG islands in promoter DNA. Nucleoside analogs including azacytidine and decitabine have been used to inhibit DNMT and re-activate genes, and are clinically used. Their shortcomings include a short half-life and a slow onset of action due to required nucleotide incorporation during DNA replication, which may limit clinical utility. It might be useful to begin to identify lead compounds having novel properties, specifically distinct and fast-acting gene desilencing. We previously identified chemicals augmenting gene expression in multiple reporter systems. We now report that a subset of these compounds that includes quinacrine re-expresses epigenetically silenced genes implicated in carcinogenesis. p16, TFPI2, the cadherins E-cadherin and CDH13, and the secreted frizzle-related proteins (SFRPs) SFRP1 and SFRP5 were desilenced in cancer cell lines. These lead compounds were fast-acting: re-expression occurred by 12-24 hours. Reactivation of silenced genes was accompanied by depletion of DNMT1 at the promoters of activated genes and demethylation of DNA. A model compound, 5175328, induced changes more rapidly than decitabine. These gene desilencing agents belonged to a class of acridine compounds, intercalated into DNA, and inhibited DNMT1 activity in vitro. Although to define the mechanism would be outside the scope of this initial report, this class may re-activate silenced genes in part by intercalating into DNA and subsequently inhibiting full DNMT1 activity. Rapid mechanisms for chemical desilencing of methylated genes therefore exist.

Hossain, M. Zulfiquer; Healey, Megan A.; Lee, Calvin; Poh, Weijie; Yerram, Sashidhar R.; Patel, Kalpesh; Azad, Nilofer S.; Herman, James G.; Kern, Scott E.

2013-01-01

193

Development and application of an efficient virus-induced gene silencing system in Nicotiana tabacum using geminivirus alphasatellite*  

PubMed Central

Virus-induced gene silencing (VIGS) is a recently developed technique for characterizing the function of plant genes by gene transcript suppression and is increasingly used to generate transient loss-of-function assays. Here we report that the 2mDNA1, a geminivirus satellite vector, can induce efficient gene silencing in Nicotiana tabacum with Tobacco curly shoot virus. We have successfully silenced the ?-glucuronidase (GUS) gene in GUS transgenic N. tabacum plants and the sulphur desaturase (Su) gene in five different N. tabacum cultivars. These pronounced and severe silencing phenotypes are persistent and ubiquitous. Once initiated in seedlings, the silencing phenotype lasted for the entire life span of the plants and silencing could be induced in a variety of tissues and organs including leaf, shoot, stem, root, and flower, and achieved at any growth stage. This system works well between 18–32 °C. We also silenced the NtEDS1 gene and demonstrated that NtEDS1 is essential for N gene mediated resistance against Tobacco mosaic virus in N. tabacum. The above results indicate that this system has great potential as a versatile VIGS system for routine functional analysis of genes in N. tabacum.

Huang, Chang-jun; Zhang, Tong; Li, Fang-fang; Zhang, Xin-yue; Zhou, Xue-ping

2011-01-01

194

Efficient delivery of small interfering RNA to plant cells by a nanosecond pulsed laser-induced stress wave for posttranscriptional gene silencing  

Microsoft Academic Search

Small interfering RNA (siRNA) induced posttranscriptional gene silencing (PTGS) has been an efficient method for genetic and molecular analysis of certain developmental and physiological processes and represented a potential strategy for both controlling virus replication and developing therapeutic products. However, there are limitations for the methods currently used to deliver siRNA into cells. We report here, to our knowledge, the

Wei Tang; Douglas A. Weidner; Benjamin Y. Hu; Ronald J. Newton; Xin-Hua Hu

2006-01-01

195

RNA interference (RNAi) for the silencing of extracellular serine proteases genes in Acanthamoeba: Molecular analysis and effect on pathogenecity  

Microsoft Academic Search

Silencing of extracellular serine protease genes was undertaken by interference RNA (RNAi). Chemically synthesized, small interfering RNA (siRNA) were highly specific and efficient in silencing the catalytic domain of extracellular serine proteases of Acanthamoeba. In order to confirm the silencing phenomenon, the extracellular serine protease activities in RNAi-treated parasites were compared to non-treated parasites, using zymography profiles, Acanthamoeba-conditioned medium (ACM)

Jacob Lorenzo-Morales; Antonio Ortega-Rivas; Pilar Foronda; Néstor Abreu-Acosta; David Ballart; Enrique Martínez; Basilio Valladares

2005-01-01

196

In Vivo Screening of Artificial Small RNAs for Silencing Endogenous Genes in Escherichia coli.  

PubMed

Bacterial noncoding small RNAs (sRNAs) modulate expression of numerous genes through antisense interactions with mRNAs. This chapter describes an in vivo screening strategy to engineer artificial sRNAs that can posttranscriptionally regulate desired endogenous genes in Escherichia coli. Artificial sRNA libraries are constructed by randomizing the antisense domain of natural sRNAs and screened for gene silencing activity using a cotransformed reporter vector. These small synthetic riboregulators can be used in synthetic gene circuits to control cell functions by directly targeting endogenous genes. PMID:23996441

Sharma, Vandana; Yokobayashi, Yohei

2013-01-01

197

Gene-silencing antisense oligomers inhibit acinetobacter growth in vitro and in vivo.  

PubMed

Background.?Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) are synthetic DNA/RNA analogues that silence expression of specific genes. We studied whether PPMOs targeted to essential genes in Acinetobacter lwoffii and Acinetobacter baumannii are active in vitro and in vivo. Methods.?PPMOs were evaluated in vitro using minimum inhibitory concentration (MIC) and viability assays, and in vivo using murine pulmonary infection models with intranasal PPMO treatment. Results.?MICs of PPMOs ranged from 0.1 to 64 µM (approximately 0.6-38 µg/mL). The most effective PPMO tested was (RXR)4-AcpP, which is targeted to acpP. (RXR)4-AcpP reduced viability of A. lwoffii and A. baumannii by >10(3) colony-forming units/mL at 5-8 times MIC. Mice treated with ?0.25 mg/kg of (RXR)4-AcpP survived longer and had less inflammation and bacterial lung burden than mice treated with a scrambled-sequence PPMO or phosphate-buffered saline. Treatment could be delayed after infection and still increase survival. Conclusions.?PPMOs targeted to essential genes of A. lwoffii and A. baumannii were bactericidal and had MICs in a clinically relevant range. (RXR)4-AcpP increased survival of mice infected with A. lwoffii or A. baumannii, even when initial treatment was delayed after infection. PPMOs could be a viable therapeutic approach in dealing with multidrug-resistant Acinetobacter species. PMID:24130069

Geller, Bruce L; Marshall-Batty, Kimberly; Schnell, Frederick J; McKnight, Mattie M; Iversen, Patrick L; Greenberg, David E

2013-10-14

198

Transcriptional silencing functions of the yeast protein Orc1/Sir3 subfunctionalized after gene duplication.  

PubMed

The origin recognition complex (ORC) defines origins of replication and also interacts with heterochromatin proteins in a variety of species, but how ORC functions in heterochromatin assembly remains unclear. The largest subunit of ORC, Orc1, is particularly interesting because it contains a nucleosome-binding BAH domain and because it gave rise to Sir3, a key silencing protein in Saccharomyces cerevisiae, through gene duplication. We examined whether Orc1 possessed a Sir3-like silencing function before duplication and found that Orc1 from the yeast Kluyveromyces lactis, which diverged from S. cerevisiae before the duplication, acts in conjunction with the deacetylase Sir2 and the histone-binding protein Sir4 to generate heterochromatin at telomeres and a mating-type locus. Moreover, the ability of KlOrc1 to spread across a silenced locus depends on its nucleosome-binding BAH domain and the deacetylase Sir2. Interestingly, KlOrc1 appears to act independently of the entire ORC, as other subunits of the complex, Orc4 and Orc5, are not strongly associated with silenced domains. These findings demonstrate that Orc1 functioned in silencing before duplication and suggest that Orc1 and Sir2, both of which are broadly conserved among eukaryotes, may have an ancient history of cooperating to generate chromatin structures, with Sir2 deacetylating histones and Orc1 binding to these deacetylated nucleosomes through its BAH domain. PMID:20974972

Hickman, Meleah A; Rusche, Laura N

2010-10-25

199

Transcriptional silencing functions of the yeast protein Orc1/Sir3 subfunctionalized after gene duplication  

PubMed Central

The origin recognition complex (ORC) defines origins of replication and also interacts with heterochromatin proteins in a variety of species, but how ORC functions in heterochromatin assembly remains unclear. The largest subunit of ORC, Orc1, is particularly interesting because it contains a nucleosome-binding BAH domain and because it gave rise to Sir3, a key silencing protein in Saccharomyces cerevisiae, through gene duplication. We examined whether Orc1 possessed a Sir3-like silencing function before duplication and found that Orc1 from the yeast Kluyveromyces lactis, which diverged from S. cerevisiae before the duplication, acts in conjunction with the deacetylase Sir2 and the histone-binding protein Sir4 to generate heterochromatin at telomeres and a mating-type locus. Moreover, the ability of KlOrc1 to spread across a silenced locus depends on its nucleosome-binding BAH domain and the deacetylase Sir2. Interestingly, KlOrc1 appears to act independently of the entire ORC, as other subunits of the complex, Orc4 and Orc5, are not strongly associated with silenced domains. These findings demonstrate that Orc1 functioned in silencing before duplication and suggest that Orc1 and Sir2, both of which are broadly conserved among eukaryotes, may have an ancient history of cooperating to generate chromatin structures, with Sir2 deacetylating histones and Orc1 binding to these deacetylated nucleosomes through its BAH domain.

Hickman, Meleah A.; Rusche, Laura N.

2010-01-01

200

Functional significance of repressor element 1 silencing transcription factor (REST) target genes in pancreatic beta cells  

Microsoft Academic Search

Aims\\/hypothesis  The expression of several neuronal genes in pancreatic beta cells is due to the absence of the transcription factor repressor\\u000a element 1 (RE-1) silencing transcription factor (REST). The identification of these traits and their functional significance\\u000a in beta cells has only been partly elucidated. Herein, we investigated the biological consequences of a repression of REST\\u000a target genes by expressing REST

D. Martin; F. Allagnat; G. Chaffard; D. Caille; M. Fukuda; R. Regazzi; A. Abderrahmani; G. Waeber; P. Meda; P. Maechler; J.-A. Haefliger

2008-01-01

201

Baculovirus-mediated gene silencing in insect cells using intracellularly produced long double-stranded RNA  

Microsoft Academic Search

Double-stranded RNA-mediated interference (RNAi) has recently emerged as a powerful reverse genetics tool to silence gene expression in multiple organisms, including plants, nematodes and insects. In this study, DNA vectors capable of promoting the synthesis of long hairpin dsRNAs in vivo from a DNA template to suppress gene expression in insect cells have been successfully constructed. The inhibition of the

Yi Huang; Fei Deng; Zhihong Hu; Just M. Vlak; Hanzhong Wang

2007-01-01

202

Different effects on ACC oxidase gene silencing triggered by RNA interference in transgenic tomato  

Microsoft Academic Search

RNA interference (RNAi) is a potent trigger for specific gene silencing of expression in a number of organisms and is an efficient way of shutting down gene expression. 1-Aminocyclopropane-1-carboxylate (ACC) oxidase catalyzes the oxidation of ACC to ethylene, a plant growth regulator that plays an important role in the tomato ripening process. In this research, to produce double-stranded (ds)RNA of

Ai-Sheng Xiong; Quan-Hong Yao; Ri-He Peng; Xian Li; Pei-Lai Han; Hui-Qin Fan

2005-01-01

203

P-Body Formation Is a Consequence, Not the Cause, of RNA-Mediated Gene Silencing  

Microsoft Academic Search

P bodies are cytoplasmic domains that contain proteins involved in diverse posttranscriptional processes, such as mRNA degradation, nonsense-mediated mRNA decay (NMD), translational repression, and RNA- mediated gene silencing. The localization of these proteins and their targets in P bodies raises the question of whether their spatial concentration in discrete cytoplasmic domains is required for posttranscriptional gene regulation. We show that

Ana Eulalio; Isabelle Behm-Ansmant; Daniel Schweizer; Elisa Izaurralde

2007-01-01

204

Virus-induced gene silencing in the rapid cycling columbine Aquilegia coerulea "Origami".  

PubMed

Aquilegia Origami is an emerging model system for ecology and evolution, which has numerous genetic and genomic tools. Virus-induced gene silencing (VIGS) has been established as an effective approach to study gene function in Aquilegia. In the current protocol, we demonstrate VIGS using Agrobacterium strain GV3101 carrying tobacco rattle virus (TRV)-based constructs to infect Aquilegia coerulea "Origami" plants via vacuum infiltration. PMID:23386296

Sharma, Bharti; Kramer, Elena M

2013-01-01

205

Role of RUNX family members in transcriptional repression and gene silencing  

Microsoft Academic Search

RUNX family members are DNA-binding transcription factors that regulate the expression of genes involved in cellular differentiation and cell cycle progression. The RUNX family includes three mammalian RUNX proteins (RUNX1, -2, -3) and two homologues in Drosophila. Experiments in Drosophila and mouse indicate that the RUNX proteins are required for gene silencing of engrailed and CD4, respectively. RUNX-mediated repression involves

Kristie L Durst; Scott W Hiebert

2004-01-01

206

Aucsia Gene Silencing Causes Parthenocarpic Fruit Development in Tomato[C][W  

PubMed Central

In angiosperms, auxin phytohormones play a crucial regulatory role in fruit initiation. The expression of auxin biosynthesis genes in ovules and placenta results in uncoupling of tomato (Solanum lycopersicum) fruit development from fertilization with production of parthenocarpic fruits. We have identified two newly described genes, named Aucsia genes, which are differentially expressed in auxin-synthesis (DefH9-iaaM) parthenocarpic tomato flower buds. The two tomato Aucsia genes encode 53-amino-acid-long peptides. We show, by RNA interference-mediated gene suppression, that Aucsia genes are involved in both reproductive and vegetative plant development. Aucsia-silenced tomato plants exhibited auxin-related phenotypes such as parthenocarpic fruit development, leaf fusions, and reflexed leaves. Auxin-induced rhizogenesis in cotyledon explants and polar auxin transport in roots were reduced in Aucsia-silenced plants compared with wild-type plants. In addition, Aucsia-silenced plants showed an increased sensitivity to 1-naphthylphthalamic acid, an inhibitor of polar auxin transport. We further prove that total indole-3-acetic acid content was increased in preanthesis Aucsia-silenced flower buds. Thus, the data presented demonstrate that Aucsia genes encode a novel family of plant peptides that control fruit initiation and affect other auxin-related biological processes in tomato. Aucsia homologous genes are present in both chlorophytes and streptophytes, and the encoded peptides are distinguished by a 16-amino-acid-long (PYSGXSTLALVARXSA) AUCSIA motif, a lysine-rich carboxyl-terminal region, and a conserved tyrosine-based endocytic sorting motif.

Molesini, Barbara; Pandolfini, Tiziana; Rotino, Giuseppe Leonardo; Dani, Valeria; Spena, Angelo

2009-01-01

207

Dynamic and reversibility of heterochromatic gene silencing in human disease  

Microsoft Academic Search

In eukaryotic organisms cellular fate and tissue specific gene expression are regulated by the activity of proteins known as transcription factors that by interacting with specific DNA sequences direct the activation or repression of target genes. The post genomic era has shown that transcription factors are not the unique key regulators of gene expression. Epigenetic mechanisms such as DNA methylation,

Giuseppe ZARDO; Francesco FAZI; Lorena TRAVAGLINI; Clara NERVI

2005-01-01

208

Gene silencing in the marine diatom Phaeodactylum tricornutum  

Microsoft Academic Search

Diatoms are a major but poorly understood phytoplankton group. The recent completion of two whole genome sequences has revealed that they contain unique combinations of genes, likely recruited during their history as secondary endo- symbionts, as well as by horizontal gene transfer from bacteria. A major limitation for the study of diatom biology and gene function is the lack of

Valentina De Riso; Raffaella Raniello; Florian Maumus; Alessandra Rogato; Chris Bowler; Angela Falciatore

2009-01-01

209

Reverse Genetics of Floral Scent: Application of Tobacco Rattle Virus-Based Gene Silencing in Petunia1[OA  

PubMed Central

Floral fragrance is responsible for attracting pollinators as well as repelling pathogens and pests. As such, it is of immense biological importance. Molecular dissection of the mechanisms underlying scent production would benefit from the use of model plant systems with big floral organs that generate an array of volatiles and that are amenable to methods of forward and reverse genetics. One candidate is petunia (Petunia hybrida), which has emerged as a convenient model system, and both RNAi and overexpression approaches using transgenes have been harnessed for the study of floral volatiles. Virus-induced gene silencing (VIGS) is characterized by a simple inoculation procedure and rapid results relative to transgenesis. Here, we demonstrate the applicability of the tobacco rattle virus-based VIGS system to studies of floral scent. Suppression of the anthocyanin pathway via chalcone synthase silencing was used as a reporter, allowing easy visual identification of anthocyaninless silenced flowers/tissues with no effect on the level of volatile emissions. Use of tobacco rattle virus constructs containing target genes involved in phenylpropanoid volatile production, fused to the chalcone synthase reporter, allowed simple identification of flowers with suppressed activity of the target genes. The applicability of VIGS was exemplified with genes encoding S-adenosyl-l-methionine:benzoic acid/salicylic acid carboxyl methyltransferase, phenylacetaldehyde synthase, and the myb transcription factor ODORANT1. Because this high-throughput reverse-genetics approach was applicable to both structural and regulatory genes responsible for volatile production, it is expected to be highly instrumental for large-scale scanning and functional characterization of novel scent genes.

Spitzer, Ben; Zvi, Michal Moyal Ben; Ovadis, Marianna; Marhevka, Elena; Barkai, Oren; Edelbaum, Orit; Marton, Ira; Masci, Tania; Alon, Michal; Morin, Shai; Rogachev, Ilana; Aharoni, Asaph; Vainstein, Alexander

2007-01-01

210

Functional characterization of Nicotiana benthamiana homologs of peanut water deficit-induced genes by virus-induced gene silencing  

Microsoft Academic Search

Determining the functional role of genes that are differentially regulated during a stress response is challenging. In this\\u000a study, few water deficit-induced genes from peanut were characterized in Nicotiana benthamiana using virus-induced gene silencing (VIGS) and their relevance for stress adaptation was validated. Twenty-five cDNA clones\\u000a from peanut water deficit stress-induced cDNA library that had more than 50% nucleotide similarity

M. Senthil-Kumar; Geetha Govind; Li Kang; Kirankumar S. Mysore; M. Udayakumar

2007-01-01

211

Active RNA Silencing at Low Temperature Indicates Distinct Pathways for Antisense-Mediated Gene-Silencing in Potato  

Microsoft Academic Search

Previously, it was shown that low temperature (? 15 °C) inhibits RNA silencing-mediated defence by the control of siRNA generation. In contrast, we have found nine antisense potato lines out of 24 in which RNA silencing was not inhibited at low temperature. In these lines, the extent of endogenous repression varied in leaves and was found to be different in roots

Anita Sós-Heged?s; Ágnes Lovas; Mihály Kondrák; Gabriella Kovács; Zsófia Bánfalvi

2005-01-01

212

Secondary RNA structure and its role in RNA interference to silence the respiratory syncytial virus fusion protein gene.  

PubMed

RNA interference (RNAi) is a post-transcriptional, gene silencing mechanism which uses small interfering RNA molecules (siRNA) for gene silencing. Respiratory Syncytial Virus (RSV) is an important respiratory pathogen of medical significance that causes high mortality in infants. The fusion (F) protein of RSV is a good target for therapeutic purposes as it is primarily responsible for penetration of the virus into host cells and subsequent syncytium formation during infection. In the present study, four siRNAs were designed and used individually as well as a mixture, to silence the RSV F gene. The relationship between siRNA design, target RNA structure, and their thermodynamics was also investigated. Silencing of F gene was observed using indirect immunofluorescence, western blot, reverse transcription PCR, and progeny viral titers. Our results show F gene silencing by all the four siRNAs individually and collectively. RT-PCR analysis revealed a decrease in mRNA level which corresponded to decreased F protein expression. siRNAs also inhibited RSV progeny as shown by viral titer estimation on infected HEp-2 cells. The present study demonstrates the silencing of the F gene using siRNA. Thermodynamic characteristics of the target RSV mRNA and siRNA seem to play an important role in siRNA gene silencing efficiency. PMID:19507066

Vig, Komal; Lewis, Nuruddeen; Moore, Eddie G; Pillai, Shreekumar; Dennis, Vida A; Singh, Shree R

2009-06-09

213

Multi-armed cationic cyclodextrin:poly(ethylene glycol) polyrotaxanes as efficient gene silencing vectors.  

PubMed

A family of branched polyrotaxanes (bPRTx(+)), threaded with multiple cationic ?-cyclodextrins (?-CDs) onto a multi-armed poly(ethylene glycol) (PEG) core, were synthesized and studied as gene silencing vectors. These bPRTx(+) formed stable, positively charged complexes with diameters of 150-250 nm at N/P ratios as low as 2.5. The bPRTx(+) materials were shown to have gene-silencing efficiencies comparable to those of Lipofectamine 2000 (L2k) and bPEI, while displaying similar toxicity profiles. The unique structure of these polyrotaxanes allows them to effectively condense and complex siRNA into nanoparticles at much lower N/P ratios than L2k or bPEI. These findings suggest that bPRTx(+) may be useful materials for gene therapy applications. PMID:23042106

Kulkarni, Aditya; DeFrees, Kyle; Schuldt, Ryan A; Vlahu, Alexander; VerHeul, Ross; Hyun, Seok-Hee; Deng, Wei; Thompson, David H

2013-01-01

214

DNA methylation and differentiation: silencing, upregulation and modulation of gene expression.  

PubMed

Differentiation-related DNA methylation is receiving increasing attention, partly owing to new, whole-genome analyses. These revealed that cell type-specific differential methylation in gene bodies is more frequent than in promoters. We review new insights into the functionality of DNA methylation during differentiation, with emphasis on the methylomes of myoblasts, myotubes and skeletal muscle versus non-muscle samples. Biostatistical analyses of data from reduced representation bisulfite sequencing are discussed. Lastly, a model is presented for how promoter and intragenic DNA hypermethylation affect gene expression, including increasing the efficiency of polycomb silencing at some promoters, downmodulating other promoters rather than silencing them, counteracting enhancers with heterologous specificity, altering chromatin conformation by inhibiting the binding of CTCF, modulating mRNA transcript levels by inhibiting overlapping promoters of noncoding RNA genes or by regulating the use of alternative mRNA promoters, modulating transcription termination, regulating alternative splicing and acting as barriers to the spread of activating chromatin. PMID:24059801

Ehrlich, Melanie; Lacey, Michelle

2013-10-01

215

The distribution of repressive histone modifications on silenced FMR1 alleles provides clues to the mechanism of gene silencing in fragile X syndrome  

PubMed Central

Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and the most common known cause of autism. Most cases of FXS result from the expansion of a CGG·CCG repeat in the 5? UTR of the FMR1 gene that leads to gene silencing. It has previously been shown that silenced alleles are associated with histone H3 dimethylated at lysine 9 (H3K9Me2) and H3 trimethylated at lysine 27 (H3K27Me3), modified histones typical of developmentally repressed genes. We show here that these alleles are also associated with elevated levels of histone H3 trimethylated at lysine 9 (H3K9Me3) and histone H4 trimethylated at lysine 20 (H4K20Me3). All four of these modified histones are present on exon 1 of silenced alleles at levels comparable to that seen on pericentric heterochromatin. The two groups of histone modifications show a different distribution on fragile X alleles: H3K9Me2 and H3K27Me3 have a broad distribution, whereas H3K9Me3 and H4K20Me3 have a more focal distribution with the highest level of these marks being present in the vicinity of the repeat. This suggests that the trigger for gene silencing may be local to the repeat itself and perhaps involves a mechanism similar to that involved in the formation of pericentric heterochromatin.

Kumari, Daman; Usdin, Karen

2010-01-01

216

Characterization of virus-induced gene silencing in tobacco plants infected with apple latent spherical virus.  

PubMed

Apple latent spherical virus (ALSV) expressing green fluorescent protein (GFP-ALSV) was used for analysis of virus-induced gene silencing (VIGS) in tobacco plants expressing GFP (GFP-tobacco). In GFP-tobacco inoculated with GFP-ALSV, small dark spots appeared on inoculated leaves at 5 days post-inoculation (dpi), then expanded, and finally covered the whole area of the leaves after 12 dpi. Most of the fluorescence of upper leaves above the 12th true leaf disappeared at 21 dpi. Thus, GFP-ALSV infection efficiently triggered VIGS of a transgene (GFP gene) in tobacco plants. Analysis of GFP-silenced leaves showed that viral RNAs and proteins accumulated in all leaves where most GFP mRNA had been degraded. The siRNAs derived from ALSV-RNAs were not detected in samples from which siRNA of GFP mRNA could be easily detected. Direct tissue blot analysis showed that the spread of GFP-ALSV always preceded the induction of VIGS in infected leaves of GFP-tobacco. GFP leaf patch tests using Nicotiana benthamiana line 16c showed that Vp20, one of the three capsid proteins, is a silencing suppressor which interferes with systemic silencing. PMID:17598069

Yaegashi, H; Yamatsuta, T; Takahashi, T; Li, C; Isogai, M; Kobori, T; Ohki, S; Yoshikawa, N

2007-06-30

217

3?UTR-Mediated Gene Silencing of the Mixed Lineage Leukemia (MLL) Gene  

PubMed Central

Translocations involving the Mixed Lineage Leukemia (MLL) gene generate in-frame fusions of MLL with more than 50 different partner genes (PGs). Common to all MLL translocations is the exchange not only of coding regions, but also of MLL and PG 3?-untranslated regions (3?UTRs). As a result, the MLL-PG fusion is normally highly expressed and considered the main driver of leukemia development, whereas the function of the PG-MLL fusions in leukemic disease is unclear. As 3?UTRs have been recognized as determinant regions for regulation of gene expression, we hypothesized that loss of the MLL 3?UTR could have a role in generating high MLL-PG levels and leukemia development. Here, we first tested the MLL-PG and PG-MLL mRNA levels in different leukemic cells and tumours and uncovered differential expression that indicates strong repression by the MLL-3?UTR. Reporter assays confirmed that the 3?UTR of MLL, but not of its main PGs, harbours a region that imposes a strong gene silencing effect. Gene suppression by the MLL 3?UTR was largely microRNA independent and did not affect mRNA stability, but inhibited transcription. This effect can at least partially be attributed to a tighter interaction of the MLL 3?UTR with RNA polymerase II than PG 3?UTRs, affecting its phosphorylation state. Altogether, our findings indicate that MLL translocations relieve oncogenic MLL-PG fusions from the repressive MLL 3?UTR, contributing to higher activity of these genes and leukaemia development.

Gomez-Benito, Maria; Loayza-Puch, Fabricio; Oude Vrielink, Joachim; Odero, Maria D.; Agami, Reuven

2011-01-01

218

Global role for polyadenylation-assisted nuclear RNA degradation in posttranscriptional gene silencing.  

PubMed

Fission yeast Cid14, a component of the TRAMP (Cid14/Trf4-Air1-Mtr4 polyadenylation) complex, polyadenylates nuclear RNA and stimulates degradation by the exosome for RNA quality control. Here, we analyze patterns of global gene expression in cells lacking the Cid14 or the Dis3/Rpr44 subunit of the nuclear exosome. We found that transcripts from many genes induced during meiosis, including key regulators, accumulated in the absence of Cid14 or Dis3. Moreover, our data suggest that additional substrates include transcripts involved in heterochromatin assembly. Mutant cells lacking Cid14 and/or Dis3 accumulate transcripts corresponding to naturally silenced repeat elements within heterochromatic domains, reflecting defects in centromeric gene silencing and derepression of subtelomeric gene expression. We also uncover roles for Cid14 and Dis3 in maintaining the genomic integrity of ribosomal DNA. Our data indicate that polyadenylation-assisted nuclear RNA turnover functions in eliminating a variety of RNA targets to control diverse processes, such as heterochromatic gene silencing, meiotic differentiation, and maintenance of genomic integrity. PMID:18025105

Wang, Shao-Win; Stevenson, Abigail L; Kearsey, Stephen E; Watt, Stephen; Bähler, Jürg

2007-11-19

219

HIGS: host-induced gene silencing in the obligate biotrophic fungal pathogen Blumeria graminis.  

PubMed

Powdery mildew fungi are obligate biotrophic pathogens that only grow on living hosts and cause damage in thousands of plant species. Despite their agronomical importance, little direct functional evidence for genes of pathogenicity and virulence is currently available because mutagenesis and transformation protocols are lacking. Here, we show that the accumulation in barley (Hordeum vulgare) and wheat (Triticum aestivum) of double-stranded or antisense RNA targeting fungal transcripts affects the development of the powdery mildew fungus Blumeria graminis. Proof of concept for host-induced gene silencing was obtained by silencing the effector gene Avra10, which resulted in reduced fungal development in the absence, but not in the presence, of the matching resistance gene Mla10. The fungus could be rescued from the silencing of Avra10 by the transient expression of a synthetic gene that was resistant to RNA interference (RNAi) due to silent point mutations. The results suggest traffic of RNA molecules from host plants into B. graminis and may lead to an RNAi-based crop protection strategy against fungal pathogens. PMID:20884801

Nowara, Daniela; Gay, Alexandra; Lacomme, Christophe; Shaw, Jane; Ridout, Christopher; Douchkov, Dimitar; Hensel, Götz; Kumlehn, Jochen; Schweizer, Patrick

2010-09-30

220

Thrombospondin-2 Gene Silencing in Human Aortic Smooth Muscle Cells Improves Cell Attachment  

PubMed Central

Background Despite decades of research, anastomotic intimal hyperplasia remains a major cause of delayed prosthetic arterial graft failure. Previously, we reported profound upregulation of Thrombospondin-2 (TSP-2) mRNA in neointimal smooth muscle cells following prosthetic arterial bypass graft placement. TSP-2 is an anti-angiogenic matricellular protein with specific functions yet unknown. In this study, we hypothesized that inhibition of TSP-2 in human aortic smooth muscle cells (HAoSMCs) would reduce cell proliferation and migration in-vitro, providing a therapeutic target to mitigate intimal hyperplasia. Study Design HAoSMCs were transfected with TSP-2 siRNA using a commercial transfection reagent. Gene silencing was evaluated using qRT-PCR. ELISA was used to measure TSP-2 protein levels in cell culture supernatants. Cell migration and proliferation were assessed using scratch wound assays and alamar blue assays respectively. Attachment assays were performed to assess the effect of TSP-2 silencing on HAoSMC adhesion to fibronectin. Results TSP-2 siRNA achieved consistent target gene silencing at 48 hours post-transfection in HAoSMCs. This single transfection allowed suppression of TSP-2 protein expression for over 30 days. TSP-2 gene silencing did not affect HAoSMC migration or proliferation. MMP-2 levels were also unaffected by changes in TSP-2 protein levels. However, HAoSMC attachment to fibronectin improved significantly in cells treated with TSP-2 siRNA. Conclusions siRNA-mediated TSP-2 silencing of human aortic HAoSMCs improved cell attachment but had no effect on cell migration or proliferation. The effect on cell attachment was unrelated to changes in MMP activity.

Yoshida, Shunsuke; Nabzdyk, Christoph S; Pradhan, Leena; LoGerfo, Frank W

2011-01-01

221

A brief history of RNAi: the silence of the genes  

Microsoft Academic Search

The use of the RNA interference (RNAi) pathway to eliminate gene products has greatly facili- tated the understanding of gene function. Behind this remarkable pathway is an intricate network of proteins that ensures the degradation of the target mRNA. In this review, we explore the history of RNAi as well as highlighting recent discoveries.—Sen, G. L., Blau, H. M. A

George L. Sen; Helen M. Blau

2006-01-01

222

Dissecting functions of KATANIN and WRINKLED1 in cotton fiber development by virus-induced gene silencing.  

PubMed

Most of the world's natural fiber comes from cotton (Gossypium spp.), which is an important crop worldwide. Characterizing genes that regulate cotton yield and fiber quality is expected to benefit the sustainable production of natural fiber. Although a huge number of expressed sequence tag sequences are now available in the public database, large-scale gene function analysis has been hampered by the low-efficiency process of generating transgenic cotton plants. Tobacco rattle virus (TRV) has recently been reported to trigger virus-induced gene silencing (VIGS) in cotton leaves. Here, we extended the utility of this method by showing that TRV-VIGS can operate in reproductive organs as well. We used this method to investigate the function of KATANIN and WRINKLED1 in cotton plant development. Cotton plants with suppressed KATANIN expression produced shorter fibers and elevated weight ratio of seed oil to endosperm. By contrast, silencing of WRINKLED1 expression resulted in increased fiber length but reduced oil seed content, suggesting the possibility to increase fiber length by repartitioning carbon flow. Our results provide evidence that the TRV-VIGS system can be used for rapid functional analysis of genes involved in cotton fiber development. PMID:22837356

Qu, Jing; Ye, Jian; Geng, Yun-Feng; Sun, Yan-Wei; Gao, Shi-Qiang; Zhang, Bi-Pei; Chen, Wen; Chua, Nam-Hai

2012-07-26

223

The role of WDR5 in silencing human fetal globin gene expression  

PubMed Central

Background Histone H3 lysine 4 (K4) methylation has been linked with transcriptional activity in mammalian cells. The WD40-repeat protein, WDR5, is an essential component of the MLL complex that induces histone H3 K4 methylation, but the role of WDR5 in human globin gene regulation has not yet been established. Design and Methods To study the role of WDR5 in human globin gene regulation, we performed knockdown experiments in both K562 cells and primary human bone marrow erythroid progenitor cells (BMC). The effects of WDR5 knockdown on ?-globin gene expression were determined. Biochemical approaches were also employed to investigate WDR5 interaction molecules. Chromosomal marks in the globin locus were analyzed by ChIP. Results We found that WDR5 interacted with protein arginine methyltransferase 5 (PRMT5), a known repressor of ?-globin gene expression, and was essential for generating tri-methylated H3K4 (H3K4me3) at the ?-globin promoter in K562 cells. Enforced expression of WDR5 in K562 cells reduced ?-globin gene expression, whereas knockdown of WDR5 increased ?-globin gene expression in both K562 cells and primary human bone marrow erythroid progenitor cells. Consistent with this, both histone H3 and H4 acetylation at the ?-globin promoter were increased, while histone H4R3 and H3K9 methylation were decreased, in WDR5 knockdown cells compared to controls. We found that WDR5 interacted with HDAC1 and a PHD domaincontaining protein, ING2 (inhibitor of growth), an H3K4me3 mark reader, to enhance ?-globin gene transcriptional repression. In human BMC, levels of WDR5 were highly enriched on the ?-promoter relative to levels on other globin promoters and compared to the ?-promoter in cord blood erythroid progenitors, suggesting that WDR5 is important in the developmental globin gene expression program. Conclusions Our data are consistent with a model in which WDR5 binds the ?-globin promoter in a PRMT5-dependent manner; H3K4me3 induced at the ?-globin promoter by WDR5 may result in the recruitment of the ING2-associated HDAC1 component and consequent silencing of ?-globin gene expression.

Xu, Zhen; He, Yinghong; Ju, Junyi; Rank, Gerhard; Cerruti, Loretta; Ma, Chi; Simpson, Richard J.; Moritz, Robert L.; Jane, Stephen M.; Zhao, Quan

2012-01-01

224

Intravaginal gene silencing using biodegradable polymer nanoparticles densely loaded with small-interfering RNA  

PubMed Central

Vaginal instillation of small-interfering RNA (siRNA) using liposomes has led to silencing of endogenous genes in the genital tract and protected against challenge from infectious disease. Although siRNA lipoplexes are easily formulated, several of the most effective transfection agents available commercially may be toxic to the mucosal epithelia and none are able to provide controlled or sustained release. Here, we demonstrate an alternate approach, using nanoparticles composed entirely of FDA-approved materials. To render these materials effective for gene silencing we developed novel approaches to load them with high amounts of siRNA. A single dose of siRNA-loaded nanoparticles to the mouse female reproductive tract caused efficient and sustained gene silencing. Knockdown of gene expression was observed proximal (in the vaginal lumen) and distal (in the uterine horns) to the site of topical delivery. In addition, nanoparticles penetrated deep into the epithelial tissue. This is the first report demonstrating that biodegradable polymer nanoparticles are effective delivery vehicles for siRNA in the vaginal mucosa.

Woodrow, Kim A.; Cu, Yen; Booth, Carmen J.; Saucier-Sawyer, Jennifer K.; Wood, Monica J.; Saltzman, W. Mark

2009-01-01

225

A common telomeric gene silencing assay is affected by nucleotide metabolism  

PubMed Central

Telomere-associated position effect variegation (TPEV) in budding yeast has been used as a model for understanding epigenetic inheritance and gene silencing. A widely used assay to identify mutants with improper TPEV employs the URA3 gene at the telomere of chromosome VII-L that can be counter-selected with 5-fluoroorotic acid (5-FOA). 5-FOA resistance has been inferred to represent lack of transcription of URA3 and therefore to represent heterochromatin-induced gene silencing. For two genes implicated in telomere silencing, POL30 and DOT1, we show that the URA3 telomere reporter assay does not reflect their role in heterochromatin formation. Rather, an imbalance in ribonucleotide reductase (RNR), which is induced by 5-FOA, and the specific promoter of URA3 fused to ADH4 at telomere VII-L are jointly responsible for the variegated phenotype. We conclude that metabolic changes caused by the drug employed and certain mutants being studied are incompatible with the use of certain prototrophic markers for TPEV.

Rossmann, Marlies P.; Luo, Weijun; Tsaponina, Olga; Chabes, Andrei; Stillman, Bruce

2011-01-01

226

Gene silencing by cell-penetrating, sequence-selective and nucleic-acid hydrolyzing antibodies  

PubMed Central

Targeting particular mRNAs for degradation is a fascinating approach to achieve gene silencing. Here we describe a new gene silencing tool exploiting a cell-penetrating, nucleic-acid hydrolyzing, single-domain antibody of the light-chain variable domain, 3D8 VL. We generated a synthetic library of 3D8 VL on the yeast surface by randomizing residues located in one of two ?-sheets. Using 18-bp single-stranded nucleic acids as target substrates, including the human Her2/neu-targeting sequence, we selected 3D8 VL variants that had ?100–1000-fold higher affinity and ?2–5-fold greater selective hydrolyzing activity for target substrates than for off targets. 3D8 VL variants efficiently penetrated into living cells to be accumulated in the cytosol and selectively decreased the amount of target sequence-carrying mRNAs as well as the proteins encoded by these mRNAs with minimal effects on off-target genes. In particular, one 3D8 VL variant targeting the Her2 sequence showed more efficient downregulation of Her2 expression than a small-interfering RNA targeting the same Her2 sequence, resulting in apoptotic cell death of Her2-overexpressing breast cancer cells. Our results demonstrate that cell-penetrating 3D8 VL variants with sequence-selective, nucleic-acid-hydrolyzing activity can selectively degrade target mRNAs in the cytosol, providing a new gene silencing tool mediated by antibody.

Jang, Ji-Young; Kim, Jeong-Sun; Kwon, Myung-Hee; Kim, Yong-Sung

2010-01-01

227

Polycomb Target Genes Are Silenced in Multiple Myeloma  

Microsoft Academic Search

Multiple myeloma (MM) is a genetically heterogeneous disease, which to date remains fatal. Finding a common mechanism for initiation and progression of MM continues to be challenging. By means of integrative genomics, we identified an underexpressed gene signature in MM patient cells compared to normal counterpart plasma cells. This profile was enriched for previously defined H3K27-tri-methylated genes, targets of the

Antonia Kalushkova; Mårten Fryknäs; Miguel Lemaire; Charlotte Fristedt; Prasoon Agarwal; Maria Eriksson; Sarah Deleu; Peter Atadja; Anders Österborg; Kenneth Nilsson; Karin Vanderkerken; Fredrik Öberg; Helena Jernberg-Wiklund; Axel Imhof

2010-01-01

228

Tomato Mosaic Virus Replication Protein Suppresses Virus-Targeted Posttranscriptional Gene Silencing  

PubMed Central

Posttranscriptional gene silencing (PTGS), a homology-dependent RNA degradation system, has a role in defending against virus infection in plants, but plant viruses encode a suppressor to combat PTGS. Using transgenic tobacco in which the expression of green fluorescent protein (GFP) is posttranscriptionally silenced, we investigated a tomato mosaic virus (ToMV)-encoded PTGS suppressor. Infection with wild-type ToMV (L strain) interrupted GFP silencing in tobacco, coincident with visible symptoms, whereas some attenuated strains of ToMV (L11 and L11A strains) failed to suppress GFP silencing. Analyses of recombinant viruses containing the L and L11A strains revealed that a single base change in the replicase gene, which causes an amino acid substitution, is responsible for the symptomless and suppressor-defective phenotypes of the attenuated strains. An agroinfiltration assay indicated that the 130K replication protein acts as a PTGS suppressor. Small interfering RNAs (siRNAs) of 21 to 25 nucleotides accumulated during ToMV infection, suggesting that the major target of the ToMV-encoded suppressor is downstream from the production of siRNAs in the PTGS pathway. Analysis with GFP-tagged recombinant viruses revealed that the suppressor inhibits the establishment of the ToMV-targeted PTGS system in the inoculated leaves but does not detectably suppress the activity of the preexisting, sequence-specific PTGS machinery there. Taken together, these results indicate that it is likely that the ToMV-encoded suppressor, the 130K replication protein, blocks the utilization of silencing-associated small RNAs, so that a homology-dependent RNA degradation machinery is not newly formed.

Kubota, Kenji; Tsuda, Shinya; Tamai, Atsushi; Meshi, Tetsuo

2003-01-01

229

Defined Folate-PEG-siRNA Conjugates for Receptor-specific Gene Silencing  

PubMed Central

Gene silencing mediated by small interfering RNA (siRNA) is a novel approach in the development of new cancer therapeutics. Polycations used for nucleic acid delivery still remain heterogeneous compounds, despite continuous progress in polymer synthetic technologies. Here we report the development of a structural defined folic acid polyethylene glycol (PEG) siRNA conjugate accessible via click chemistry yielding a monodisperse ligand-PEG-siRNA conjugate. The folic acid targeting ligand was synthesized by solid phase supported peptide chemistry. The conjugate was shown to be specifically internalized into folic acid receptor expressing cells. When combined with a structurally defined polycation, again synthesized with the precision of solid phase chemistry, efficient receptor specific gene silencing is achieved.

Dohmen, Christian; Frohlich, Thomas; Lachelt, Ulrich; Rohl, Ingo; Vornlocher, Hans-Peter; Hadwiger, Philipp; Wagner, Ernst

2012-01-01

230

Effective Gene Silencing by Multilayered siRNA Coated Gold Nanoparticles**  

PubMed Central

Small interfering RNA (siRNA) has been widely proposed to treat various diseases by silencing genes, but its delivery remains a challenge. A well-controlled assembly approach was applied to prepare a protease assisted nanodelivery system. Onto a gold nanoparticles (AuNPs), protease degradable poly-L-lysine (PLL) and siRNA were fabricated by alternating the charged polyelectrolytes. In this study, up to 4 layers of PLL and 3 layers of siRNA (sR3P) were coated. Due to slow degradation of PLL, the incorporated siRNA was released gradually and showed extended gene silencing effect. Importantly, the inhibition effect in cells was found to correlate with the number of siRNA layers.

Lee, Seung Koo; Han, Myung Shin; Asokan, Subashini

2011-01-01

231

Bidirectional transfer of RNAi between honey bee and Varroa destructor: Varroa gene silencing reduces Varroa population.  

PubMed

The mite Varroa destructor is an obligatory ectoparasite of the honey bee (Apis mellifera) and is one of the major threats to apiculture worldwide. We previously reported that honey bees fed on double-stranded RNA (dsRNA) with a sequence homologous to that of the Israeli acute paralysis virus are protected from the viral disease. Here we show that dsRNA ingested by bees is transferred to the Varroa mite and from mite on to a parasitized bee. This cross-species, reciprocal exchange of dsRNA between bee and Varroa engendered targeted gene silencing in the latter, and resulted in an over 60% decrease in the mite population. Thus, transfer of gene-silencing-triggering molecules between this invertebrate host and its ectoparasite could lead to a conceptually novel approach to Varroa control. PMID:23308063

Garbian, Yael; Maori, Eyal; Kalev, Haim; Shafir, Sharoni; Sela, Ilan

2012-12-20

232

Bidirectional Transfer of RNAi between Honey Bee and Varroa destructor: Varroa Gene Silencing Reduces Varroa Population  

PubMed Central

The mite Varroa destructor is an obligatory ectoparasite of the honey bee (Apis mellifera) and is one of the major threats to apiculture worldwide. We previously reported that honey bees fed on double-stranded RNA (dsRNA) with a sequence homologous to that of the Israeli acute paralysis virus are protected from the viral disease. Here we show that dsRNA ingested by bees is transferred to the Varroa mite and from mite on to a parasitized bee. This cross-species, reciprocal exchange of dsRNA between bee and Varroa engendered targeted gene silencing in the latter, and resulted in an over 60% decrease in the mite population. Thus, transfer of gene-silencing-triggering molecules between this invertebrate host and its ectoparasite could lead to a conceptually novel approach to Varroa control.

Kalev, Haim; Shafir, Sharoni; Sela, Ilan

2012-01-01

233

Compromised virus-induced gene silencing in RDR6-deficient plants.  

PubMed

RNA silencing in plants serves as a potent antiviral defense mechanism through the action of small interfering RNAs (siRNAs), which direct RNA degradation. siRNAs can be derived directly from the viral genome or via the action of host-encoded RNA-dependent RNA polymerases (RDRs). Plant genomes encode multiple RDRs, and it has been demonstrated that plants defective for RDR6 hyperaccumulate several classes of virus. In this study, we compared the effectiveness of virus-induced gene silencing (VIGS) and RNA-directed DNA methylation (RdDM) in wild-type and RDR6-deficient Nicotiana benthamiana plants. For the potexvirus Potato virus X (PVX) and the potyvirus Plum pox virus (PPV), the efficiency of both VIGS and RdDM were compromised in RDR6-defective plants despite accumulating high levels of viral siRNAs similar to infection of wild-type plants. The reduced efficiency of VIGS and RdDM was unrelated to the size class of siRNA produced and, at least for PVX, was not dependent on the presence of the virus-encoded silencing suppressor protein, 25K. We suggest that primary siRNAs produced from PVX and PPV in the absence of RDR6 may not be good effectors of silencing and that RDR6 is required to produce secondary siRNAs that drive a more effective antiviral response. PMID:19129420

Vaistij, Fabián E; Jones, Louise

2009-01-07

234

Hepatic Stellate Cell-Specific Gene Silencing Induced by an Artificial MicroRNA for Antifibrosis In Vitro  

Microsoft Academic Search

Background  We previously reported that the anti-transforming growth factor-beta1 (TGF-?1) ribozymes directed by T7 and CMV promoters\\u000a could reverse the character of activated hepatic stellate cells (HSCs) in vitro and improve fibrotic pathology in vivo. However,\\u000a nonspecific elimination of the effects of TGF-?1 without selectivity might have unfavorable consequences, such as overwhelming\\u000a inflammation, tissue necrosis, etc.\\u000a \\u000a \\u000a \\u000a \\u000a Aims  To establish an activated-HSC-specific gene silencing method

Ying ChangHua-jun; Hua-jun Jiang; Xue-mei Sun; Xiao-kun Cai; Xing-xing He; Pei-yuan Li; Wang-xian Tang; Yu-hu Song; Ju-sheng Lin

2010-01-01

235

Silencing Huntington’s Disease Gene with RNAi  

Microsoft Academic Search

\\u000a Huntington’s disease (HD), a hereditary condition afflicting 30,000 Americans, cannot be treated by existing therapies and\\u000a it is universally fatal. It is characterized by movement disorder (Huntington’s chorea), emotional distress, and dementia.\\u000a HD is caused by a highly penetrant, autosomal-dominant mutation in the HD gene at chromosomal locus 4p16.3. Expansion of the\\u000a CAG repeat at the 5?-end of this gene

Yu Zhang; Robert M. Friedlander

236

Multisubunit RNA polymerases IV and V: purveyors of non-coding RNA for plant gene silencing  

Microsoft Academic Search

In all eukaryotes, nuclear DNA-dependent RNA polymerases I, II and III synthesize the myriad RNAs that are essential for life. Remarkably, plants have evolved two additional multisubunit RNA polymerases, RNA polymerases IV and V, which orchestrate non-coding RNA-mediated gene silencing processes affecting development, transposon taming, antiviral defence and allelic crosstalk. Biochemical details concerning the templates and products of RNA polymerases

Jeremy R. Haag; Craig S. Pikaard

2011-01-01

237

How Does RNA Editing Affect dsRNA-mediated Gene Silencing?  

Microsoft Academic Search

In general, double-stranded RNA (dsRNA)-binding proteins (dsRBPs) are not sequence-specific. A dsRNA molecule in a cell will interact with any dsRBP it comes in contact with, suggesting that different dsRNA-mediated pathways intersect and affect each other. This paper analyzes evidence that the ADAR RNA editing enzymes, which act on dsRNA, affect dsRNA-medi- ated gene silencing pathways. Examples of how ADARs

B. L. BASS

2006-01-01

238

Cucurbit yellow stunting disorder virus p25 is a suppressor of post-transcriptional gene silencing  

Microsoft Academic Search

Post-transcriptional gene silencing (PTGS) degrades RNA in a sequence-specific manner and is utilised by plants as a natural defence mechanism against virus invaders. Two members of the genus Crinivirus have been reported to encode suppressors and counter PTGS: Sweet potato chlorotic stunt virus p22 and Tomato chlorosis virus (ToCV) p22, coat protein and coat protein minor. Using an Agrobacterium-mediated transient

Amr R. A. Kataya; Mohamed N. S. Suliman; Kriton Kalantidis; Ioannis C. Livieratos

2009-01-01

239

Epigenetic Silencing of Nucleolar rRNA Genes in Alzheimer's Disease  

Microsoft Academic Search

BackgroundRibosomal deficits are documented in mild cognitive impairment (MCI), which often represents an early stage Alzheimer's disease (AD), as well as in advanced AD. The nucleolar rRNA genes (rDNA), transcription of which is critical for ribosomal biogenesis, are regulated by epigenetic silencing including promoter CpG methylation.Methodology\\/Principal FindingsTo assess whether CpG methylation of the rDNA promoter was dysregulated across the AD

Maciej Pietrzak; Grzegorz Rempala; Peter T. Nelson; Jing-Juan Zheng; Michal Hetman

2011-01-01

240

Genetic unmasking of epigenetically silenced tumor suppressor genes in colon cancer cells deficient in DNA methyltransferases  

Microsoft Academic Search

Hypermethylation associated silencing of the CpG islands of tumor suppressor genes is a common hallmark of human cancer. Here we report a functional search for hypermethylated CpG islands using the colorectal cancer cell line HCT-116, in which two major DNA methyltransferases, DNMT1 and DNMT3b, have been genetically disrupted (DKO cells). Using two molecular screenings for differentially methylated loci (differential methylation

Maria F. Paz; Susan Wei; Juan C. Cigudosa; Sandra Rodriguez-Perales; Miguel A. Peinado; Tim Hui-Ming Huang; Manel Esteller

2003-01-01

241

Structural insights into human KAP1 PHD finger–bromodomain and its role in gene silencing  

Microsoft Academic Search

The tandem PHD finger–bromodomain, found in many chromatin-associated proteins, has an important role in gene silencing by the human co-repressor KRAB-associated protein 1 (KAP1). Here we report the three-dimensional solution structure of the tandem PHD finger–bromodomain of KAP1. The structure reveals a distinct scaffold unifying the two protein modules, in which the first helix, ?Z, of an atypical bromodomain forms

Lei Zeng; Kyoko L Yap; Alexey V Ivanov; Xueqi Wang; Shiraz Mujtaba; Olga Plotnikova; Frank J Rauscher III; Ming-Ming Zhou

2008-01-01

242

Fertile Hypomorphic ARGONAUTE (ago1) Mutants Impaired in PostTranscriptional Gene Silencing and Virus Resistance  

Microsoft Academic Search

Transgene-induced post-transcriptional gene silencing (PTGS) results from specific degradation of RNAs that are ho- mologous with the transgene transcribed sequence. This phenomenon, also known as cosuppression in plants and quelling in fungi, resembles RNA interference (RNAi) in animals. Indeed, cosuppression\\/quelling\\/RNAi require related PAZ\\/PIWI proteins (AGO1\\/QDE-2\\/RDE-1), indicating that these mechanisms are related. Unlike Neurospora crassa qde-2 and Caenorhabditis elegans rde-1 mutants,

Jean-Benoit Morel; Christian Godon; Philippe Mourrain; Christophe Béclin; Stéphanie Boutet; Frank Feuerbach; Florence Proux; Hervé Vaucheret

2002-01-01

243

TRBP recruits the Dicer complex to Ago2 for microRNA processing and gene silencing  

Microsoft Academic Search

MicroRNAs (miRNAs) are generated by a two-step processing pathway to yield RNA molecules of approximately 22nucleotides that negatively regulate target gene expression at the post-transcriptional level. Primary miRNAs are processed to precursor miRNAs (pre-miRNAs) by the Microprocessor complex. These pre-miRNAs are cleaved by the RNase III Dicer to generate mature miRNAs that direct the RNA-induced silencing complex (RISC) to messenger

Thimmaiah P. Chendrimada; Richard I. Gregory; Easwari Kumaraswamy; Jessica Norman; Neil Cooch; Kazuko Nishikura; Ramin Shiekhattar

2005-01-01

244

Functional gene silencing mediated by chitosan/siRNA nanocomplexes  

NASA Astrophysics Data System (ADS)

Chitosan/siRNA nanoparticles to knock down FHL2 gene expression were reported in this work. The physicochemical properties such as particle size, surface charge, morphology and complex stability of chitosan nanoparticle-incorporated siRNA were evaluated. Nanoparticles which were formulated with chitosan/siRNA exhibited irregular, lamellar and dendritic structures with a hydrodynamic radius size of about 148 nm and net positive charges with zeta-potential value of 58.5 mV. The knockdown effect of the chitosan/siRNA nanoparticles on gene expression in FHL2 over-expressed human colorectal cancer Lovo cells was investigated. The result showed that FHL2 siRNA formulated within chitosan nanoparticles could knock down about 69.6% FHL2 gene expression, which is very similar to the 68.8% reduced gene expression when siRNA was transfected with liposome Lipofectamine. Western analysis further showed significant FHL-2 protein expression reduced by the chitosan/siRNA nanoparticles. The results also showed that blocking FHL2 expression by siRNA could also inhibit the growth and proliferation of human colorectal cancer Lovo cells. The current results demonstrated that chitosan-based siRNA nanoparticles were a very efficient delivery system for siRNA in vivo as previously reported.

Ji, A. M.; Su, D.; Che, O.; Li, W. S.; Sun, L.; Zhang, Z. Y.; Yang, B.; Xu, F.

2009-10-01

245

Discovery of epigenetically silenced genes in acute myeloid leukemias.  

PubMed

The demethylating 5-aza-2'deoxycytidine (DAC) and the histone deacetylase inhibitor (HDACi) suberoyl anilide bishydroxamide (SAHA) possess potent antitumorigenic properties in myeloid disorders. However, the transcriptome alterations mediated by these drugs are poorly understood. We analyzed the transcriptional effects of DAC and SAHA in the AML cell line KG-1. Microarray analyses revealed 76 genes expressed in normal CD34+ cells, absent in KG-1 cells but whose expression was induced after drug treatment. A total of 39 of these genes harbored CpG islands in their promoters. We examined the expression level of these genes in 120 AML patient samples representing diverse karyotpyes. Gas2l1, tfIIs, ehd3, enolase 2, mx1, dral, astml and pxdn were diminished across all AML karyotypes examined. Ehd3 was methylated in 63% of AML patients examined. This methylation was lost upon complete remission, and not observed in normal CD34+ cells. CD34+ cells expressed ehd3 at approximately 10-fold higher levels than AML samples. Another highlighted gene, alpha-catenin, is located at q31 of chromosome 5. Analyses of 29 5q- AML/myelodysplastic syndrome (MDS) samples revealed marked decreases in expression of alpha-catenin, compared to non-5q- MDS samples (6.6+/-9-fold). However, no methylation was detected, suggesting indirect effects of these drugs on the expression of alpha-catenin. PMID:17330099

Desmond, J C; Raynaud, S; Tung, E; Hofmann, W-K; Haferlach, T; Koeffler, H P

2007-03-01

246

Efficient gene silencing by delivery of locked nucleic acid antisense oligonucleotides, unassisted by transfection reagents  

Microsoft Academic Search

For the past 15-20 years, the intracellular delivery and silencing activity of oligodeoxynucleotides have been essentially completely dependent on the use of a delivery technology (e.g. lipofection). We have developed a method (called 'gymnosis') that does not require the use of any transfection reagent or any additives to serum whatsoever, but rather takes advantage of the normal growth properties of

C. A. Stein; J. Bo Hansen; Johnathan Lai; SiJian Wu; Anatoliy Voskresenskiy; A. Hog; Jesper Worm; Maj Hedtjarn; Naira Souleimanian; Paul Miller; Harris S. Soifer; Daniella Castanotto; Luba Benimetskaya; H. Orum; Troels Koch

2010-01-01

247

Cell-free construction of disarmed Abutilon mosaic virus-based gene silencing vectors.  

PubMed

The bipartite Abutilon mosaic virus (AbMV) was engineered as a versatile silencing vector in which the coat protein gene of DNA A was deleted and replaced by sequences of interest. Plants transgenic for the dimeric AbMV DNA B component were used as test hosts to minimize the risk of unintended release of the recombinant DNA. The vector construct was stable genetically upon systemic infection and, in common with the parental virus, the vector remained phloem-limited. For virus-induced gene silencing (VIGS), a phytoene desaturase gene fragment was isolated from Nicotiana benthamiana (NbPDS) and inserted into the vector. After agroinfection, phytoene desaturase silencing was triggered efficiently in all leaf tissues without interference by viral symptoms. In order to facilitate further the use of the system, a technique for cell-free construction of recombinants was established using rolling circle amplification and biolistic inoculation of DNA B-transgenic plants. This novel procedure provides a convenient and safe way for delivering VIGS constructs for functional genomics. PMID:20638413

Krenz, Björn; Wege, Christina; Jeske, Holger

2010-07-16

248

DNA Elements Reducing Transcriptional Gene Silencing Revealed by a Novel Screening Strategy  

PubMed Central

Transcriptional gene silencing (TGS)–a phenomenon observed in endogenous genes/transgenes in eukaryotes–is a huge hindrance to transgenic technology and occurs mainly when the genes involved share sequence homology in their promoter regions. TGS depends on chromosomal position, suggesting the existence of genomic elements that suppress TGS. However, no systematic approach to identify such DNA elements has yet been reported. Here, we developed a successful novel screening strategy to identify such elements (anti-silencing regions–ASRs), based on their ability to protect a flanked transgene from TGS. A silenced transgenic tobacco plant in which a subsequently introduced transgene undergoes obligatory promoter-homology dependent TGS in trans allowed the ability of DNA elements to prevent TGS to be used as the screening criterion. We also identified ASRs in a genomic library from a different plant species (Lotus japonicus: a perennial legume); the ASRs include portions of Ty1/copia retrotransposon-like and pararetrovirus-like sequences; the retrotransposon-like sequences also showed interspecies anti-TGS activity in a TGS-induction system in Arabidopsis. Anti-TGS elements could provide effective tools to reduce TGS and ensure proper regulation of transgene expression. Furthermore, the screening strategy described here will also facilitate the efficient identification of new classes of anti-TGS elements.

Ueno, Keiichiro; Ohashi, Yuko; Mitsuhara, Ichiro

2013-01-01

249

CASPASE 2-MEDIATED TUMOR SUPPRESSION INVOLVES SURVIVIN GENE SILENCING  

PubMed Central

One of the pivotal functions of endogenous tumor suppression is to oppose aberrant cell survival, but the molecular requirements of this process are not completely understood. Here, we show that caspase 2, a death effector with largely unknown functions, represses transcription of the survivin gene, a general regulator of cell division and cytoprotection in tumors. This pathway involves caspase 2 proteolytic cleavage of the NF?B activator, RIP1. In turn, loss of RIP1 abolishes transcription of NF?B target genes, including survivin, resulting in deregulated mitotic transitions, enhanced apoptosis, and suppression of tumorigenicity, in vivo. Therefore, caspase 2 functions as an endogenous inhibitor of NF?B-dependent cell survival, and this mechanism may contribute to tumor suppression in humans.

Guha, Minakshi; Xia, Fang; Raskett, Christopher M.; Altieri, Dario C.

2009-01-01

250

Gene silencing in Caenorhabditis elegans by transitive RNA interference  

Microsoft Academic Search

When a cell is exposed to double-stranded RNA (dsRNA), mRNA from the homologous gene is selectively degraded by a process called RNA interference (RNAi). Here, we provide evidence that dsRNA is amplified in Caenorhabditis elegans to ensure a robust RNAi response. Our data suggest a model in which mRNA targeted by RNAi functions as a template for 5 to 3

MATTHEW N. ALDER; SHALE DAMES; JEFFREY GAUDET; SUSAN E. MANGO

2003-01-01

251

Small RNAs in transcriptional gene silencing and genome defence  

Microsoft Academic Search

Small RNA molecules of about 20-30 nucleotides have emerged as powerful regulators of gene expression and genome stability. Studies in fission yeast and multicellular organisms suggest that effector complexes, directed by small RNAs, target nascent chromatin-bound non-coding RNAs and recruit chromatin-modifying complexes. Interactions between small RNAs and nascent non-coding transcripts thus reveal a new mechanism for targeting chromatin-modifying complexes to

Danesh Moazed

2009-01-01

252

Ikaros and GATA-1 Combinatorial Effect Is Required for Silencing of Human ?-Globin Genes?  

PubMed Central

During development and erythropoiesis, globin gene expression is finely modulated through an important network of transcription factors and chromatin modifying activities. In this report we provide in vivo evidence that endogenous Ikaros is recruited to the human ?-globin locus and targets the histone deacetylase HDAC1 and the chromatin remodeling protein Mi-2 to the human ?-gene promoters, thereby contributing to ?-globin gene silencing at the time of the ?- to ?-globin gene transcriptional switch. We show for the first time that Ikaros interacts with GATA-1 and enhances the binding of the latter to different regulatory regions across the locus. Consistent with these results, we show that the combinatorial effect of Ikaros and GATA-1 impairs close proximity between the locus control region and the human ?-globin genes. Since the absence of Ikaros also affects GATA-1 recruitment to GATA-2 promoter, we propose that the combinatorial effect of Ikaros and GATA-1 is not restricted to globin gene regulation.

Bottardi, Stefania; Ross, Julie; Bourgoin, Vincent; Fotouhi-Ardakani, Nasser; Affar, El Bachir; Trudel, Marie; Milot, Eric

2009-01-01

253

Gene Silencing by RNA Interference in the White Rot Fungus Phanerochaete chrysosporium?  

PubMed Central

The effectiveness of RNA interference (RNAi) is demonstrated in the lignin-degrading fungus Phanerochaete chrysosporium. The manganese-containing superoxide dismutase gene (MnSOD1) was used as the target for RNAi. The plasmid constructed for gene silencing contained a transcriptional unit for hairpin RNA expression. Significantly lower MnSOD expression at both the mRNA and protein activity levels was detected in RNAi transformants. Furthermore, even though P. chrysosporium possesses three copies of the MnSOD gene, this RNAi construct was sufficient to decrease the enzymatic activity by as much as 70% relative to control levels. Implementation of the RNAi technique in P. chrysosporium provides an alternative genetic tool for studies of gene function, particularly of essential genes or gene families.

Matityahu, Avi; Hadar, Yitzhak; Dosoretz, Carlos G.; Belinky, Paula A.

2008-01-01

254

Gene silencing by RNA Interference in the white rot fungus Phanerochaete chrysosporium.  

PubMed

The effectiveness of RNA interference (RNAi) is demonstrated in the lignin-degrading fungus Phanerochaete chrysosporium. The manganese-containing superoxide dismutase gene (MnSOD1) was used as the target for RNAi. The plasmid constructed for gene silencing contained a transcriptional unit for hairpin RNA expression. Significantly lower MnSOD expression at both the mRNA and protein activity levels was detected in RNAi transformants. Furthermore, even though P. chrysosporium possesses three copies of the MnSOD gene, this RNAi construct was sufficient to decrease the enzymatic activity by as much as 70% relative to control levels. Implementation of the RNAi technique in P. chrysosporium provides an alternative genetic tool for studies of gene function, particularly of essential genes or gene families. PMID:18606804

Matityahu, Avi; Hadar, Yitzhak; Dosoretz, Carlos G; Belinky, Paula A

2008-07-07

255

RNA silencing in plants  

Microsoft Academic Search

There are at least three RNA silencing pathways for silencing specific genes in plants. In these pathways, silencing signals can be amplified and transmitted between cells, and may even be self-regulated by feedback mechanisms. Diverse biological roles of these pathways have been established, including defence against viruses, regulation of gene expression and the condensation of chromatin into heterochromatin. We are

David Baulcombe

2004-01-01

256

Rapid activation of the bivalent gene Sox21 requires displacement of multiple layers of gene-silencing machinery  

PubMed Central

The rapid formation of numerous tissues during development is highly dependent on the swift activation of key developmental regulators. Recent studies indicate that many key regulatory genes are repressed in embryonic stem cells (ESCs), yet poised for rapid activation due to the presence of both activating (H3K4 trimethylation) and repressive (H3K27 trimethylation) histone modifications (bivalent genes). However, little is known about bivalent gene regulation. In this study, we investigated the regulation of the bivalent gene Sox21, which is activated rapidly when ESCs differentiate in response to increases in Sox2. Chromatin immunoprecipitation demonstrated that prior to differentiation, the Sox21 gene is bound by a complex array of repressive and activating transcriptional machinery. Upon activation, all identified repressive machinery and histone modifications associated with the gene are lost, but the activating modifications and transcriptional machinery are retained. Notably, these changes do not occur when ESCs differentiate in response to retinoic acid. Moreover, ESCs lacking a functional PRC2 complex fail to activate this gene, apparently due to its association with other repressive complexes. Together, these findings suggest that bivalent genes, such as Sox21, are silenced by a complex set of redundant repressive machinery, which exit rapidly in response to appropriate differentiation signals.—Chakravarthy, H., Ormsbee, B. D., Mallanna, S. K., Rizzino, A. Rapid activation of the bivalent gene Sox21 requires displacement of multiple layers of gene-silencing machinery.

Chakravarthy, Harini; Ormsbee, Briana D.; Mallanna, Sunil K.; Rizzino, Angie

2011-01-01

257

Reduced expression of DACT2 promotes hepatocellular carcinoma progression: involvement of methylation-mediated gene silencing  

PubMed Central

Background Hepatocellular carcinoma (HCC) is one of the most aggressive malignancies in humans, and its prognosis is generally poor even after surgery. Many advances have been made to understand the pathogenesis of HCC; however, the molecular mechanisms that lead to hepatocarcinogenesis and progression are still not clearly understood. Methods The expression of DACT2 in specimens from 30 paired HCCs and an additional 61 HCC patients after liver transplantation was evaluated by quantitative RT-PCR and immunohistochemical analysis. We investigated the methylation status of the DACT2 promoter region. We also analyzed the alterations of the cell cycle, migration and invasion after DACT2 knockdown. Results The expression level of DACT2 was significantly lower in HCC tissues than in non-cancerous tissues. Reduced DACT2 expression was associated with large tumor size. DACT2 transcripts were at low levels in hypermethylated liver cancer cells and were restored by exposure to a demethylating agent. Reduced expression of DACT2 in MHCC97L cells induced G1/S arrest, increased cell proliferation, and promoted cell invasion. Conclusions Our study suggests that DACT2 is silenced by promoter hypermethylation, and reduced DACT2 can promote liver cancer progression. DACT2 may serve as a novel tumor suppressor gene in HCC.

2013-01-01

258

H-NS mediates the silencing of laterally acquired genes in bacteria.  

PubMed

Histone-like nucleoid structuring protein (H-NS) is a modular protein that is associated with the bacterial nucleoid. We used chromatin immunoprecipitation to determine the binding sites of H-NS and RNA polymerase on the Salmonella enterica serovar Typhimurium chromosome. We found that H-NS does not bind to actively transcribed genes and does not co-localize with RNA polymerase. This shows that H-NS principally silences gene expression by restricting the access of RNA polymerase to the DNA. H-NS had previously been shown to preferentially bind to curved DNA in vitro. In fact, at the genomic level we discovered that the level of H-NS binding correlates better with the AT-content of DNA. This is likely to have evolutionary consequences because we show that H-NS binds to many Salmonella genes acquired by lateral gene transfer, and functions as a gene silencer. The removal of H-NS from the cell causes un-controlled expression of several Salmonella pathogenicity islands, and we demonstrate that this has deleterious consequences for bacterial fitness. Our discovery of this novel role for H-NS may have implications for the acquisition of foreign genes by enteric bacteria. PMID:16933988

Lucchini, Sacha; Rowley, Gary; Goldberg, Martin D; Hurd, Douglas; Harrison, Marcus; Hinton, Jay C D

2006-08-01

259

Lsh participates in DNA methylation and silencing of stem cell genes.  

PubMed

Transcriptional control of stem cell genes is a critical step in differentiation of embryonic stem cells and in reprogramming of somatic cells into stem cells. Here we report that Lsh, a regulator of repressive chromatin at retrotransposons, also plays an important role in silencing of stem cell-specific genes such as Oct4. We found that CpG methylation is gained during in vitro differentiation of several stem cell-specific genes (in 11 of 12 promoter regions) and thus appears to be a common epigenetic mark. Lsh depletion prevents complete silencing of stem cell gene expression and moreover promotes the maintenance of stem cell characteristics in culture. Lsh is required for establishment of DNA methylation patterns at stem cell genes during differentiation, in part by regulating access of Dnmt3b to its genomic targets. Our results indicate that Lsh is involved in the control of stem cell genes and suggest that Lsh is an important epigenetic modulator during early stem cell differentiation. PMID:19650037

Xi, Sichuan; Geiman, Theresa M; Briones, Victorino; Guang Tao, Yong; Xu, Hong; Muegge, Kathrin

2009-11-01

260

Simultaneous gene transduction and silencing using stimuli-responsive viral/nonviral chimeric nanoparticles.  

PubMed

Despite viral vectors' predominant use in clinical trials, due to higher gene delivery efficiency than nonviral counterparts, intrinsic immunogenicity and limited tunability for multi-modal effects are major concerns for their usage in gene therapy. An adeno-associated viral (AAV) particle was shielded with acid-degradable, siRNA-encapsulating polyketal (PK) shell, resulting in core-shell viral/nonviral chimeric nanoparticles (ChNPs). The AAV core of a ChNP is protected from immune responses by the PK shell which also facilitates the intracellular trafficking of the AAV core and efficiently releases the encapsulated siRNA into the cytoplasm. ChNPs led to significantly enhanced gene transduction, compared to unmodified free AAVs, and simultaneous silencing of a target gene, while avoiding inactivation by recognition from the immune system. Furthermore, conjugation of sialic acid (SA) on the surface of ChNPs enabled receptor-mediated targeted gene delivery to CD22-expressing cells. The ChNPs developed in this study combine the advantages of both viral and nonviral vectors and are a promising platform for targeted co-delivery of DNA and siRNA in inducing synergistic therapeutic effects by simultaneous expression and silencing of multiple genes. PMID:22281425

Cho, Soo Kyung; Kwon, Young Jik

2012-01-24

261

A mode matching method for modeling dissipative silencers lined with poroelastic materials and containing mean flow.  

PubMed

A mode matching method for predicting the transmission loss of a cylindrical shaped dissipative silencer partially filled with a poroelastic foam is developed. The model takes into account the solid phase elasticity of the sound-absorbing material, the mounting conditions of the foam, and the presence of a uniform mean flow in the central airway. The novelty of the proposed approach lies in the fact that guided modes of the silencer have a composite nature containing both compressional and shear waves as opposed to classical mode matching methods in which only acoustic pressure waves are present. Results presented demonstrate good agreement with finite element calculations provided a sufficient number of modes are retained. In practice, it is found that the time for computing the transmission loss over a large frequency range takes a few minutes on a personal computer. This makes the present method a reliable tool for tackling dissipative silencers lined with poroelastic materials. PMID:21218865

Nennig, Benoit; Perrey-Debain, Emmanuel; Ben Tahar, Mabrouk

2010-12-01

262

Selective gene silencing in activated leukocytes by targeting siRNAs to the integrin lymphocyte function-associated antigen-1  

PubMed Central

Silencing gene expression by RNAi is a powerful method for exploring gene function and validating drug targets and potentially for therapy. Lymphocytes and other primary blood cells are resistant to lipid-based transfection in vitro and are difficult to target in vivo. We show here that antibody-protamine fusion proteins targeting the human integrin lymphocyte function-associated antigen-1 (LFA-1) efficiently deliver siRNAs and specifically induce silencing in primary lymphocytes, monocytes, and dendritic cells. Moreover, a fusion protein constructed from an antibody that preferentially recognizes activation-dependent conformational changes in LFA-1 selectively targets activated leukocytes and can be used to suppress gene expression and cell proliferation only in activated lymphocytes. The siRNA-fusion protein complexes do not cause lymphocyte activation or induce IFN responses. K562 cells expressing latent WT or constitutively activated LFA-1 engrafted in the lungs of SCID mice are selectively targeted by intravenously injected fusion protein–siRNA complexes, demonstrating the potential in vivo applicability of LFA-1-directed siRNA delivery.

Peer, Dan; Zhu, Pengcheng; Carman, Christopher V.; Lieberman, Judy; Shimaoka, Motomu

2007-01-01

263

The efficiency of silencing expression of the gene coding STAT3 transcriptional factor and susceptibility of bladder cancer cells to apoptosis  

PubMed Central

Aim of the study Abnormalities in signaling as well as altered gene expression have been identified in numerous diseases, including cancer. The biological functions of signal transducer and activator of transcription 3 (STAT3) are very broad. It is thought that STAT3 can also contribute to oncogenesis. RNA interference (RNAi) is one of the most efficient tools for silencing gene expression within cells. The main goal of the study was to verify the effectiveness of STAT3 gene silencing and its influence on cell proliferation and activation of apoptosis in bladder cancer cells. Material and methods The study was conducted on cellular material, which was the stable human bladder cancer cell line T24. The synthesis of shRNA (short hairpin RNA) interfering with the STAT3 gene was based on pSUPER. neo expression vector. The gene expression at the mRNA level was determined by the real-time PCR method. The influence of STAT3 gene silencing on apoptosis induced in cells with modulated STAT3 expression was evaluated using parallel quantification of mono- and oligonucleosomal DNA degradation of genomic DNA. Results In transfected T24 cells, the STAT3 mRNA expression decreased to the level of 68.3% compared to the scrambled (SCR) control. Silencing the STAT3 gene induced changes in the phenotype of T24 cells. Statistically significant differences in cell proliferation (p = 0.0318) and apoptosis induction (p = 0.0376) were observed. Conclusions Application of the designed shRNA for the STAT3 gene contributed to a decrease of expression of the examined gene. It also decreased the proliferation and increased the susceptibility to apoptosis in T24 bladder cancer cells.

Bednarek, Ilona; Sypniewski, Daniel; Gawlik, Natalia; Goraus, Karol

2012-01-01

264

Potato Virus X-Induced Gene Silencing in Leaves and Tubers of Potato1  

PubMed Central

Virus induced gene silencing (VIGS) is increasingly used to generate transient loss-of-function assays and has potential as a powerful reverse-genetics tool in functional genomic programs as a more rapid alternative to stable transformation. A previously described potato virus X (PVX) VIGS vector has been shown to trigger silencing in the permissive host Nicotiana benthamiana. This paper demonstrates that a PVX-based VIGS vector is also effective in triggering a VIGS response in both diploid and cultivated tetraploid Solanum species. We show that systemic silencing of a phytoene desaturase gene is observed and maintained throughout the foliar tissues of potato plants and was also observed in tubers. Here we report that VIGS can be triggered and sustained on in vitro micropropagated tetraploid potato for several cycles and on in vitro generated microtubers. This approach will facilitate large-scale functional analysis of potato expressed sequence tags and provide a noninvasive reverse-genetic approach to study mechanisms involved in tuber and microtuber development.

Faivre-Rampant, Odile; Gilroy, Eleanor M.; Hrubikova, Katarina; Hein, Ingo; Millam, Steve; Loake, Gary J.; Birch, Paul; Taylor, Mark; Lacomme, Christophe

2004-01-01

265

Splicing factor Spf30 assists exosome-mediated gene silencing in fission yeast.  

PubMed

Heterochromatin assembly in fission yeast relies on the processing of cognate noncoding RNAs by both the RNA interference and the exosome degradation pathways. Recent evidence indicates that splicing factors facilitate the cotranscriptional processing of centromeric transcripts into small interfering RNAs (siRNAs). In contrast, how the exosome contributes to heterochromatin assembly and whether it also relies upon splicing factors were unknown. We provide here evidence that fission yeast Spf30 is a splicing factor involved in the exosome pathway of heterochromatin silencing. Spf30 and Dis3, the main exosome RNase, colocalize at centromeric heterochromatin and euchromatic genes. At the centromeres, Dis3 helps recruiting Spf30, whose deficiency phenocopies the dis3-54 mutant: heterochromatin is impaired, as evidenced by reduced silencing and the accumulation of polyadenylated centromeric transcripts, but the production of siRNAs appears to be unaffected. Consistent with a direct role, Spf30 binds centromeric transcripts and locates at the centromeres in an RNA-dependent manner. We propose that Spf30, bound to nascent centromeric transcripts, perhaps with other splicing factors, assists their processing by the exosome. Splicing factor intercession may thus be a common feature of gene silencing pathways. PMID:20028739

Bernard, Pascal; Drogat, Julie; Dheur, Sonia; Genier, Sylvie; Javerzat, Jean-Paul

2009-12-22

266

Effective endogenous gene silencing mediated by pH responsive peptides proceeds via multiple pathways  

PubMed Central

Cationic amphipathic histidine rich peptides possess high plasmid DNA and siRNA delivery capabilities. To further understand the pH responsive siRNA delivery process and evaluate the capabilities of such peptides we have investigated their ability to mediate specific silencing of endogenous GAPDH gene activity in MCF-7 and A549 cells and compared this with plasmid DNA delivery. A substantial and selective reduction of both GAPDH activity and expression was achieved using pH responsive peptide vectors, which compared favourably with that mediated by commercially available non-viral vectors in terms of efficacy and toxicity. Furthermore, by comparing the efficacy of both gene delivery and silencing mediated by a series of such peptides, their sensitivities to known inhibitors of endocytotic processes, and their route of uptake via confocal live cell imaging, we show that both plasmid DNA and siRNA are internalised via endocytosis. However siRNA entry facilitated by LAH4-L1, proceeds via a cholesterol dependent mechanism, in contrast to DNA transfer which is associated with clathrin dependent endocytosis. Furthermore, using peptides that respond at increasingly acidic pH, we demonstrate that the route of entry for the siRNA that ultimately mediates silencing is peptide specific and while some pH responsive peptides promote the escape of labelled siRNA from endosomes, others may promote entry via alternative mechanisms.

Lam, Jenny. K.W.; Liang, Wanling; Lan, Yun; Chaudhuri, Poulami; Chow, Michael Y.T.; Witt, Katarzyna; Kudsiova, Laila; Mason, A. James

2012-01-01

267

Gene silencing of HIV chemokine receptors using ribozymes and single-stranded antisense RNA.  

PubMed

The chemokine receptors CXCR4 and CCR5 are required for HIV-1 to enter cells, and the progression of HIV-1 infection to AIDS involves a switch in the co-receptor usage of the virus from CCR5 to CXCR4. These receptors therefore make attractive candidates for therapeutic intervention, and we have investigated the silencing of their genes by using ribozymes and single-stranded antisense RNAs. In the present study, we demonstrate using ribozymes that a depletion of CXCR4 and CCR5 mRNAs can be achieved simultaneously in human PBMCs (peripheral blood mononuclear cells), cells commonly used by the virus for infection and replication. Ribozyme activity leads to an inhibition of the cell-surface expression of both CCR5 and CXCR4, resulting in a significant inhibition of HIV-1 replication when PBMCs are challenged with the virus. In addition, we show that small single-stranded antisense RNAs can also be used to silence CCR5 and CXCR4 genes when delivered to PBMCs. This silencing is caused by selective degradation of receptor mRNAs. PMID:16293105

Qureshi, Amer; Zheng, Richard; Parlett, Terry; Shi, Xiaoju; Balaraman, Priyadhashini; Cheloufi, Sihem; Murphy, Brendan; Guntermann, Christine; Eagles, Peter

2006-03-01

268

Gene silencing of HIV chemokine receptors using ribozymes and single-stranded antisense RNA  

PubMed Central

The chemokine receptors CXCR4 and CCR5 are required for HIV-1 to enter cells, and the progression of HIV-1 infection to AIDS involves a switch in the co-receptor usage of the virus from CCR5 to CXCR4. These receptors therefore make attractive candidates for therapeutic intervention, and we have investigated the silencing of their genes by using ribozymes and single-stranded antisense RNAs. In the present study, we demonstrate using ribozymes that a depletion of CXCR4 and CCR5 mRNAs can be achieved simultaneously in human PBMCs (peripheral blood mononuclear cells), cells commonly used by the virus for infection and replication. Ribozyme activity leads to an inhibition of the cell-surface expression of both CCR5 and CXCR4, resulting in a significant inhibition of HIV-1 replication when PBMCs are challenged with the virus. In addition, we show that small single-stranded antisense RNAs can also be used to silence CCR5 and CXCR4 genes when delivered to PBMCs. This silencing is caused by selective degradation of receptor mRNAs.

Qureshi, Amer; Zheng, Richard; Parlett, Terry; Shi, Xiaoju; Balaraman, Priyadhashini; Cheloufi, Sihem; Murphy, Brendan; Guntermann, Christine; Eagles, Peter

2005-01-01

269

Intrinsic nucleic acid-binding activity of Chp1 chromodomain is required for heterochromatic gene silencing.  

PubMed

Centromeric heterochromatin assembly in fission yeast requires the RNAi pathway. Chp1, a chromodomain (CD) protein, forms the Ago1-containing RNA-induced transcriptional silencing (RITS) complex and recruits siRNA-bound RITS to methylated histone H3 lysine 9 (H3K9me) via its CD. Here, we show that the CD of Chp1 (Chp1-CD) possesses unique nucleic acid-binding activities that are essential for heterochromatic gene silencing. Detailed electrophoretic-mobility shift analyses demonstrated that Chp1 binds to RNA via the CD in addition to its central RNA-recognition motif. Interestingly, robust RNA- and DNA-binding activity of Chp1-CD was strongly enhanced when it was bound to H3K9me, which was revealed to involve a positively charged domain within the Chp1-CD by structural analyses. These results demonstrate a role for the CD that provides a link between RNA, DNA, and methylated histone tails to ensure heterochromatic gene silencing. PMID:22727667

Ishida, Mayumi; Shimojo, Hideaki; Hayashi, Aki; Kawaguchi, Rika; Ohtani, Yasuko; Uegaki, Koichi; Nishimura, Yoshifumi; Nakayama, Jun-Ichi

2012-06-21

270

Silencing of the AV2 gene by antisense RNA protects transgenic plants against a bipartite begomovirus  

PubMed Central

Whitefly-transmitted geminiviruses (genus Begomovirus) are phytopathogens that cause heavy losses to crops worldwide. Efforts to engineer resistance against these viruses are focused mainly on silencing of complementary-sense virus genes involved in virus replication. Here we have targeted a virion-sense gene (AV2) to develop resistance against Tomato leaf curl New Delhi virus, a bipartite begomovirus prevalent throughout the Indian subcontinent. We show that tobacco plants transformed with an antisense construct targeting this gene are resistant to the virus. Following challenged with the virus, transgenic plants remained symptomless, although viral DNA could be detected in some plants by PCR. This is the first report of transgenic resistance against a bipartite begomovirus obtained by targeting a virion-sense gene. The relatively conserved nature of the gene suggests that the technology may be useful to develop broad-spectrum resistance which is required because of the fact that plants are often infected with multiple begomoviruses in the field.

Mubin, Muhammad; Mansoor, Shahid; Hussain, Mazhar; Zafar, Yusuf

2007-01-01

271

RNA-Mediated Silencing in Algae: Biological Roles and Tools for Analysis of Gene Function ?  

PubMed Central

Algae are a large group of aquatic, typically photosynthetic, eukaryotes that include species from very diverse phylogenetic lineages, from those similar to land plants to those related to protist parasites. The recent sequencing of several algal genomes has provided insights into the great complexity of these organisms. Genomic information has also emphasized our lack of knowledge of the functions of many predicted genes, as well as the gene regulatory mechanisms in algae. Core components of the machinery for RNA-mediated silencing show widespread distribution among algal lineages, but they also seem to have been lost entirely from several species with relatively small nuclear genomes. Complex sets of endogenous small RNAs, including candidate microRNAs and small interfering RNAs, have now been identified by high-throughput sequencing in green, red, and brown algae. However, the natural roles of RNA-mediated silencing in algal biology remain poorly understood. Limited evidence suggests that small RNAs may function, in different algae, in defense mechanisms against transposon mobilization, in responses to nutrient deprivation and, possibly, in the regulation of recently evolved developmental processes. From a practical perspective, RNA interference (RNAi) is becoming a promising tool for assessing gene function by sequence-specific knockdown. Transient gene silencing, triggered with exogenously synthesized nucleic acids, and/or stable gene repression, involving genome-integrated transgenes, have been achieved in green algae, diatoms, yellow-green algae, and euglenoids. The development of RNAi technology in conjunction with system level “omics” approaches may provide the tools needed to advance our understanding of algal physiological and metabolic processes.

Cerutti, Heriberto; Ma, Xinrong; Msanne, Joseph; Repas, Timothy

2011-01-01

272

Polycomb silencing of the Drosophila 4E-BP gene regulates imaginal disc cell growth.  

PubMed

Polycomb group (PcG) proteins are best known for their role in maintaining stable, mitotically heritable silencing of the homeotic (HOX) genes during development. In addition to loss of homeotic gene silencing, some PcG mutants also have small imaginal discs. These include mutations in E(z), Su(z)12, esc and escl, which encode Polycomb repressive complex 2 (PRC2) subunits. The cause of this phenotype is not known, but the human homologs of PRC2 subunits have been shown to play a role in cell proliferation, are over-expressed in many tumors, and appear to be required for tumor proliferation. Here we show that the small imaginal disc phenotype arises, at least in part, from a cell growth defect. In homozygous E(z) mutants, imaginal disc cells are smaller than cells in normally proliferating discs. We show that the Thor gene, which encodes eIF4E-binding protein (4E-BP), the evolutionarily conserved inhibitor of cap-dependent translation and potent inhibitor of cell growth, is involved in the development of this phenotype. The Thor promoter region contains DNA binding motifs for transcription factors found in well-characterized Polycomb response elements (PREs), including PHO/PHOL, GAGA factor, and others, suggesting that Thor may be a direct target of Polycomb silencing. We present chromatin immunoprecipitation evidence that PcG proteins are bound to the Thor 5' region in vivo. The Thor gene is normally repressed in imaginal discs, but Thor mRNA and 4E-BP protein levels are elevated in imaginal discs of PRC2 subunit mutant larvae. Deletion of the Thor gene in E(z) mutants partially restores imaginal disc size toward wild-type and results in an increase in the fraction of larvae that pupariate. These results thus suggest that PcG proteins can directly modulate cell growth in Drosophila, in part by regulating Thor expression. PMID:23523430

Mason-Suares, Heather; Tie, Feng; Yan, Christopher M; Harte, Peter J

2013-03-20

273

Multiple Bromodomain Genes Are Involved in Restricting the Spread of Heterochromatic Silencing at the Saccharomyces cerevisiae HMR-tRNA Boundary  

Microsoft Academic Search

The transfer RNA gene downstream from the HMR locus in S. cerevisiae functions as part of a boundary (barrier) element that restricts the spread of heterochromatic gene silencing into the downstream region of chromosome III. A genetic screen for identifying additional genes that, when mutated, allow inap- propriate spreading of silencing from HMR through the tRNA gene was performed. YTA7,

Nithya Jambunathan; Adam W. Martinez; Elizabeth C. Robert; Nneamaka B. Agochukwu; Megan E. Ibos; Sandra L. Dugas; David Donze

2005-01-01

274

Developmental Silencing of Human ?-Globin Gene Expression Is Mediated by the Transcriptional Repressor RREB1*  

PubMed Central

The mammalian embryonic ?-globin genes, including that of humans, are expressed at the early embryonic stage and then switched off during erythroid development. This autonomous silencing of the ?-globin gene transcription is probably regulated by the cooperative work of various protein-DNA and protein-protein complexes formed at the ?-globin promoter and its upstream enhancer (HS-40). We present data here indicating that a protein-binding motif, ZF2, contributes to the repression of the HS-40-regulated human ?-promoter activity in erythroid cell lines and in transgenic mice. Combined site-directed mutagenesis and EMSA suggest that repression of the human ?-globin promoter is mediated through binding of the zinc finger factor RREB1 to ZF2. This model is further supported by the observation that human ?-globin gene transcription is elevated in the human erythroid K562 cell line or the primary erythroid culture upon RNA interference (RNAi)2 knockdown of RREB1 expression. These data together suggest that RREB1 is a putative repressor for the silencing of the mammalian ?-globin genes during erythroid development. Because ?-globin is a powerful inhibitor of HbS polymerization, our experiments have provided a foundation for therapeutic up-regulation of ?-globin gene expression in patients with severe hemoglobinopathies.

Chen, Ruei-Lin; Chou, Yu-Chi; Lan, Yii-Jenq; Huang, Ting-Shuo; Shen, C.-K. James

2010-01-01

275

A High Throughput Barley Stripe Mosaic Virus Vector for Virus Induced Gene Silencing in Monocots and Dicots  

Microsoft Academic Search

Barley stripe mosaic virus (BSMV) is a single-stranded RNA virus with three genome components designated alpha, beta, and gamma. BSMV vectors have previously been shown to be efficient virus induced gene silencing (VIGS) vehicles in barley and wheat and have provided important information about host genes functioning during pathogenesis as well as various aspects of genes functioning in development. To

Cheng Yuan; Cui Li; Lijie Yan; Andrew O. Jackson; Zhiyong Liu; Chenggui Han; Jialin Yu; Dawei Li

2011-01-01

276

Transgene-Induced Silencing of the Zoosporogenesis-Specific NIFC Gene Cluster of Phytophthora infestans Involves Chromatin Alterations?  

PubMed Central

Clustered within the genome of the oomycete phytopathogen Phytophthora infestans are four genes encoding spore-specific nuclear LIM interactor-interacting factors (NIF proteins, a type of transcriptional regulator) that are moderately conserved in DNA sequence. NIFC1, NIFC2, and NIFC3 are zoosporogenesis-induced and grouped within 4 kb, and 20 kb away resides a sporulation-induced form, NIFS. To test the function of the NIFC family, plasmids expressing full-length hairpin constructs of NIFC1 or NIFC2 were stably transformed into P. infestans. This triggered silencing of the cognate gene in about one-third of transformants, and all three NIFC genes were usually cosilenced. However, NIFS escaped silencing despite its high sequence similarity to the NIFC genes. Silencing of the three NIFC genes impaired zoospore cyst germination by 60% but did not affect other aspects of the life cycle. Silencing was transcriptional based on nuclear run-on assays and associated with tighter chromatin packing based on nuclease accessibility experiments. The chromatin alterations extended a few hundred nucleotides beyond the boundaries of the transcribed region of the NIFC cluster and were not associated with increased DNA methylation. A plasmid expressing a short hairpin RNA having sequence similarity only to NIFC1 silenced both that gene and an adjacent member of the gene cluster, likely due to the expansion of a heterochromatic domain from the targeted locus. These data help illuminate the mechanism of silencing in Phytophthora and suggest that caution should be used when interpreting silencing experiments involving closely spaced genes.

Judelson, Howard S.; Tani, Shuji

2007-01-01

277

Arabidopsis SGS2 and SGS3 Genes Are Required for Posttranscriptional Gene Silencing and Natural Virus Resistance  

Microsoft Academic Search

Posttranscriptional gene silencing (PTGS) in plants results from the degradation of mRNAs and shows phenomenological similarities with quelling in fungi and RNAi in animals. Here, we report the isolation of sgs2 and sgs3 Arabidopsis mutants impaired in PTGS. We establish a mechanistic link between PTGS, quelling, and RNAi since the Arabidopsis SGS2 protein is similar to an RNA-dependent RNA polymerase

Philippe Mourrain; Christophe Béclin; Taline Elmayan; Frank Feuerbach; Christian Godon; Jean-Benoit Morel; David Jouette; Anne-Marie Lacombe; Snezana Nikic; Nathalie Picault; Karine Rémoué; Mathieu Sanial; Truy-Anh Vo; Hervé Vaucheret

2000-01-01

278

GATA-4 and GATA-5 Transcription Factor Genes and Potential Downstream Antitumor Target Genes Are Epigenetically Silenced in Colorectal and Gastric Cancer  

PubMed Central

The GATA family of transcription factors participates in gastrointestinal (GI) development. Increases in GATA-4 and -5 expression occur in differentiation and GATA-6 expression in proliferation in embryonic and adult settings. We now show that in colorectal cancer (CRC) and gastric cancer promoter hypermethylation and transcriptional silencing are frequent for GATA-4 and -5 but are never seen for GATA-6. Potential antitumor target genes upregulated by GATA-4 and -5, the trefoil factors, inhibin?, and disabled-2 (Dab2) are also silenced, in GI cancers, with associated methylation of the promoters. Drug or genetically induced demethylation simultaneously leads to expression, in CRC cells, of all of the GATA-4, -5, and downstream genes. Expression of exogenous GATA-5 overrides methylation at the downstream promoters to activate the target genes. Selection for silencing of both upstream transcription factors and their target genes in GI cancers could indicate that epigenetic silencing of the involved genes provides a summated contribution to tumor progression.

Akiyama, Yoshimitsu; Watkins, Neil; Suzuki, Hiromu; Jair, Kam-Wing; van Engeland, Manon; Esteller, Manel; Sakai, Hidekazu; Ren, Chun-Yan; Yuasa, Yasuhito; Herman, James G.; Baylin, Stephen B.

2003-01-01

279

RORC2 Gene Silencing in Human Th17 Cells by siRNA: Design and Evaluation of Highly Efficient siRNA  

PubMed Central

Background RNA interference-based gene silencing has recently been applied as an efficient tool for functional gene analysis. RORC2 is the key transcription factor orchestrating Th17 cells differentiation, the cells that are known as the pathogenic elements in various autoimmune diseases. The aim of this study was to design efficient siRNAs specific for RORC2 and to evaluate different criteria affecting their functionality. Methods Three siRNA duplexes specific for RORC2 mRNA were designed. Th17 cells were produced from IL-6 and IL-1 treated cord blood CD4+ T cells. The T cells were transfected with three different designed siRNAs against RORC2 and the expression of RORC2 gene was measured using quantitative real time PCR. Results Different levels of RORC2 down regulation were observed in the presence of each of the designed siRNAs. Efficient siRNA with 91.1% silencing activity met the majority of the established bioinformatics criteria while the one with 46.6% silencing activity had more deviations from these criteria. Conclusion The more bioinformatics criteria are considered, the more functionality were observed for silencing RORC2. However, the importance of the type of criteria per se should not be neglected. Although all recommended criteria are important for designing siRNA but their value is not the same.

Hakemi, Mazdak Ganjalikhani; Ghaedi, Kamran; Andalib, Alireza; Homayouni, Vida; Hosseini, Mohsen; Rezaei, Abbas

2013-01-01

280

Methylation of TFPI-2 gene is not the sole cause of its silencing.  

PubMed

TFPI-2 (tissue factor pathway inhibitor-2) is a serine protease inhibitor that may suppress tumor cell invasion and metastasis. TFPI-2 expression is often lost in cells derived from tumors of diverse organs. We have examined whether aberrant hypermethylation of the 5' end of the TFPI-2 gene is associated with its loss of expression. After 5-azacytidine treatment of three cell lines lacking TFPI-2 expression (HT1080 fibrosarcoma cells, MCF-7 breast carcinoma cells, and LNCaP prostate carcinoma cells), TFPI-2 transcripts could be detected by RT-PCR. In these three cell lines, methylation of the 5' end of the TFPI-2 gene was detected, while two prostate carcinoma cell lines in which the TFPI-2 gene was expressed, PC-3 and DU-145, showed no methylation. However, all the three cell lines which lacked TFPI-2 expression also contained unmethylated TFPI-2 alleles. Furthermore, a transiently transfected TFPI-2 promoter was non-functional in the three cell lines, but function was attained following treatment with 5-azacytidine. Our results indicate that while methylation of the TFPI-2 gene is associated with its silencing, it is not the sole cause, and we suggest that one or more components of pathways regulating TFPI-2 expression have also undergone methylation-associated silencing in these cell lines. PMID:12632077

Rao, Chilukuri N; Segawa, Takehiko; Navari, Jason R; Xu, Linda; Srivastava, Shiv; Moul, Judd W; Phillips, Benette

2003-04-01

281

Heterochromatin silencing at p53 target genes by a small viral protein  

PubMed Central

The transcription factor p53 guards against tumor and virus replication and is inactivated in almost all cancers. p53 activated transcription of target genes is thought to be synonymous with the stabilization of p53 in response to oncogenes and DNA damage. During adenovirus replication, the degradation of p53 by E1B-55k is considered essential for p53 inactivation, and is the basis for p53 selective viral cancer therapies. Here we reveal a dominant epigenetic mechanism that silences p53-activated transcription, irrespective of p53 phosphorylation and stabilization. We show that another adenoviral protein, E4-ORF3, inactivates p53 independently of E1B-55k by forming a nuclear structure that induces de novo H3K9me3 heterochromatin formation at p53 target promoters, preventing p53 DNA-binding. This suppressive nuclear web is highly selective in silencing p53 promoters and operates in the backdrop of global transcriptional changes that drive oncogenic replication. These findings are important for understanding how high levels of wild-type p53 might also be inactivated in cancer as well as the mechanisms that induce aberrant epigenetic silencing of tumor suppressor loci. Our study changes the longstanding definition of how p53 is inactivated in adenovirus infection and provides key insights that could enable the development of true p53 selective oncolytic viral therapies.

Soria, Conrado; Estermann, Fanny E.; Espantman, Kristen C.; O'Shea, Clodagh C.

2010-01-01

282

Tissue-specific gene silencing mediated by a naturally occurring chalcone synthase gene cluster in Glycine max.  

PubMed

Chalcone synthase, a key regulatory enzyme in the flavonoid pathway, constitutes an eight-member gene family in Glycine max (soybean). Three of the chalcone synthase (CHS) gene family members are arranged as inverted repeats in a 10-kb region, corresponding to the I locus (inhibitor). Spontaneous mutations of a dominant allele (I or i(i)) to a recessive allele (i) have been shown to delete promoter sequences, paradoxically increasing total CHS transcript levels and resulting in black seed coats. However, it is not known which of the gene family members contribute toward pigmentation and how this locus affects CHS expression in other tissues. We investigated the unusual nature of the I locus using four pairs of isogenic lines differing with respect to alleles of the I locus. RNA gel blots using a generic open reading frame CHS probe detected similar CHS transcript levels in stems, roots, leaves, young pods, and cotyledons of the yellow and black isolines but not in the seed coats, which is consistent with the dominant I and i(i) alleles mediating CHS gene silencing in a tissue-specific manner. Using real-time RT-PCR, a variable pattern of expression of CHS genes in different tissues was demonstrated. However, increase in pigmentation in the black seed coats was associated with release of the silencing effect specifically on CHS7/CHS8, which occurred at all stages of seed coat development. These expression changes were linked to structural changes taking place at the I locus, shown to encompass a much wider region of at least 27 kb, comprising two identical 10.91-kb stretches of CHS gene duplications. The suppressive effect of this 27-kb I locus in a specific tissue of the G. max plant represents a unique endogenous gene silencing mechanism. PMID:15064367

Tuteja, Jigyasa H; Clough, Steven J; Chan, Wan-Ching; Vodkin, Lila O

2004-04-01

283

Identification and characterization of a novel transcriptional silencer in the human collagen type IV gene COL4A2.  

PubMed

Collagen type IV [alpha 1(IV)2 alpha 2(IV)] is the basic structural component of all basement membranes. The two subunit genes COL4A1 and COL4A2 are found closely linked in the human and murine genomes and are transcribed divergently from a common promoter. Previously, activating elements had been detected within both genes which are indispensable for efficient transcription. An additional negative regulatory element has now been identified within the third intron of the COL4A2 gene which is able to inhibit transcription of both COL4 genes from their shared promoter, as well as the nonrelated herpes simplex virus thymidine kinase promoter. The element exerts its inhibitory effect largely independently from its relative orientation and distance from the initiation site of transcription. Therefore, the element represents a silencer which is named the "COL4 silencer." The minimal functional silencer could be narrowed down by deletion mapping to a sequence element located within intron 3 of the COL4A2 gene. This motif is specifically recognized by a nuclear protein, named "SILBF," and the binding site of which was determined by footprinting assays. Mutation studies and deletion analysis proved that the presence of this sequence element and its interaction with SILBF is not only essential but also sufficient for the silencing function. We assume that the COL4 silencer plays an important role in the control of overall expression and the balance of divergent transcription of both COL4 genes. PMID:7744753

Haniel, A; Welge-Lüssen, U; Kühn, K; Pöschl, E

1995-05-12

284

MED19 and MED26 Are Synergistic Functional Targets of the RE1 Silencing Transcription Factor in Epigenetic Silencing of Neuronal Gene Expression*S?  

PubMed Central

A key hub for the orchestration of epigenetic modifications necessary to restrict neuronal gene expression to the nervous system is the RE1 silencing transcription factor (REST; also known as neuron restrictive silencer factor, NRSF). REST suppresses the nonspecific and premature expression of neuronal genes in non-neuronal and neural progenitor cells, respectively, via recruitment of enzymatically diverse corepressors, including G9a histone methyltransferase (HMTase) that catalyzes di-methylation of histone 3-lysine 9 (H3K9me2). Recently, we identified the RNA polymerase II transcriptional Mediator to be an essential link between RE1-bound REST and G9a in epigenetic suppression of neuronal genes in non-neuronal cells. However, the means by which REST recruits Mediator to facilitate G9a-dependent extra-neuronal gene silencing remains to be elucidated. Here, we identify the MED19 and MED26 subunits in Mediator as direct physical and synergistic functional targets of REST. We show that although REST independently binds to both MED19 and MED26 in isolation, combined depletion of both subunits is required to disrupt the association of REST with Mediator. Furthermore, combined, but not individual, depletion of MED19/MED26 impairs REST-directed recruitment to RE1 elements of Mediator and G9a, leading to a reversal of G9a-dependent H3K9me2 and de-repression of REST-target gene expression. Together, these findings identify MED19/MED26 as a probable composite REST interface in Mediator and further clarify the mechanistic basis by which Mediator facilitates REST-imposed epigenetic restrictions on neuronal gene expression.

Ding, Ning; Tomomori-Sato, Chieri; Sato, Shigeo; Conaway, Ronald C.; Conaway, Joan W.; Boyer, Thomas G.

2009-01-01

285

Silencing VP28 gene of white spot syndrome virus of shrimp by bacterially expressed dsRNA.  

PubMed

An in vivo expression system to produce large amounts of virus-derived dsRNAs in bacteria to provide a practical control of white spot syndrome virus (WSSV) in shrimp was developed. The bacterially synthesized dsRNA specific to VP28 gene of WSSV promoted gene-specific interference with the WSSV infection in shrimp. Virus infectivity was significantly reduced in WSSV-challenged shrimp injected with VP28-dsRNA and 100% survival was recorded. The inhibition of the expression of WSSV VP28 gene in experimentally challenged animals by VP28-dsRNA was confirmed by RT-PCR and Western blot analyses. Furthermore, we have demonstrated the efficacy of bacterially expressed VP28-dsRNA to silence VP28 gene expression in SISK cell line transfected with eukaryotic expression vector (pcDNA3.1) inserted with VP28 gene of WSSV. The expression level of VP28 gene in SISK cells was determined by fluorescent microscopy and ELISA. The results showed that the expression was significantly reduced in cells transfected with VP28dsRNA, whereas the cells transected with pcDNA-VP28 alone showed higher expression. The in vivo production of dsRNA using prokaryotic expression system could be an alternative to in vitro method for large-scale production of dsRNA corresponding to VP28 gene of WSSV for practical application to control the WSSV in shrimp farming. PMID:17965920

Sarathi, M; Simon, Martin C; Ahmed, V P Ishaq; Kumar, S Rajesh; Hameed, A S Sahul

2007-10-27

286

A Single dicer Gene Is Required for Efficient Gene Silencing Associated with Two Classes of Small Antisense RNAs in Mucor circinelloides? †  

PubMed Central

RNA silencing in the zygomycete Mucor circinelloides exhibits uncommon features, such as induction by self-replicative sense transgenes and the accumulation of two size classes of antisense small interfering RNAs (siRNAs). To investigate whether this silencing phenomenon follows the rules of a canonical RNA-silencing mechanism, we used hairpin RNA (hpRNA)-producing constructs as silencing triggers and analyzed the efficiency and stability of silencing in different genetic backgrounds. We show here that the dsRNA-induced silencing mechanism is also associated with the accumulation of two sizes of antisense siRNAs and that this mechanism is not mediated by the previously known dcl-1 (dicer-like) gene, which implies the existence of an additional dicer gene. An M. circinelloides dcl-2 gene was cloned and characterized, and the corresponding null mutant was generated by gene replacement. This mutant is severely impaired in the silencing mechanism induced by self-replicative sense or inverted-repeat transgenes, providing the first genetic evidence of a canonical silencing mechanism in this class of fungus and pointing to a role for dcl-2 in the mechanism. Moreover, a functional dcl-2 gene is required for the normal accumulation of the two sizes of antisense RNAs, as deduced from the analysis of dcl-2? transformants containing hpRNA-expressing plasmids. In addition to its critical role in transgene-induced silencing, the dcl-2 gene seems to play a role in the control of vegetative development, since the dcl-2 null mutants showed a significant decrease in their production of asexual spores.

de Haro, Juan P.; Calo, Silvia; Cervantes, Maria; Nicolas, Francisco E.; Torres-Martinez, Santiago; Ruiz-Vazquez, Rosa M.

2009-01-01

287

Herpes Simplex Virus Type 1 Suppresses RNA-Induced Gene Silencing in Mammalian Cells  

Microsoft Academic Search

RNA-induced silencing is a potent innate antiviral defense strategy in plants, and suppression of silencing is a hallmark of pathogenic plant viruses. However, the impact of silencing as a mammalian antiviral defense mechanism and the ability of mammalian viruses to suppress silencing in natural host cells have remained controversial. The ability of herpes simplex virus type 1 (HSV-1) to suppress

Zetang Wu; Yali Zhu; David M. Bisaro; Deborah S. Parris

2009-01-01

288

Characterization of virus-induced gene silencing in tobacco plants infected with apple latent spherical virus  

Microsoft Academic Search

Summary  Apple latent spherical virus (ALSV) expressing green fluorescent protein (GFP-ALSV) was used for analysis of virus-induced\\u000a gene silencing (VIGS) in tobacco plants expressing GFP (GFP-tobacco). In GFP-tobacco inoculated with GFP-ALSV, small dark\\u000a spots appeared on inoculated leaves at 5 days post-inoculation (dpi), then expanded, and finally covered the whole area of\\u000a the leaves after 12 dpi. Most of the fluorescence

H. Yaegashi; T. Yamatsuta; T. Takahashi; C. Li; M. Isogai; T. Kobori; S. Ohki; N. Yoshikawa

2007-01-01

289

Intergenic transcripts originating from a subclass of ribosomal DNA repeats silence ribosomal RNA genes in trans.  

PubMed

Epigenetic silencing of a fraction of ribosomal DNA (rDNA) requires association of the nucleolar chromatin-remodelling complex NoRC to 150-250 nucleotide RNAs (pRNA) that originate from an RNA polymerase I promoter located in the intergenic spacer separating rDNA repeats. Here, we show that NoRC-associated pRNA is transcribed from a sub-fraction of hypomethylated rRNA genes during mid S phase, acting in trans to inherit DNA methylation and transcriptional repression of late-replicating silent rDNA copies. The results reveal variability between individual rDNA clusters with distinct functional consequences. PMID:20010804

Santoro, Raffaella; Schmitz, Kerstin-Maike; Sandoval, Juan; Grummt, Ingrid

2009-12-04

290

In vivo production of small interfering RNAs that mediate gene silencing  

US Patent & Trademark Office Database

The invention provides engineered RNA precursors that when expressed in a cell are processed by the cell to produce targeted small interfering RNAs (siRNAs) that selectively silence targeted genes (by cleaving specific mRNAs) using the cell's own RNA interference (RNAi) pathway. By introducing nucleic acid molecules that encode these engineered RNA precursors into cells in vitro with appropriate regulatory sequences, expression of the engineered RNA precursors can be selectively controlled both temporally and spatially, i.e., at particular times and/or in particular tissues, organs, or cells.

2012-07-31

291

Multisubunit RNA Polymerases IV and V: Purveyors of Non-Coding RNA for Plant Gene Silencing  

SciTech Connect

In all eukaryotes, nuclear DNA-dependent RNA polymerases I, II and III synthesize the myriad RNAs that are essential for life. Remarkably, plants have evolved two additional multisubunit RNA polymerases, RNA polymerases IV and V, which orchestrate non-coding RNA-mediated gene silencing processes affecting development, transposon taming, antiviral defence and allelic crosstalk. Biochemical details concerning the templates and products of RNA polymerases IV and V are lacking. However, their subunit compositions reveal that they evolved as specialized forms of RNA polymerase II, which provides the unique opportunity to study the functional diversification of a eukaryotic RNA polymerase family.

Haag, Jeremy R.; Pikaard, Craig S.

2011-08-01

292

Silencing of TaBTF3 gene impairs tolerance to freezing and drought stresses in wheat.  

PubMed

Basic transcription factor 3 (BTF3), the ?-subunit of the nascent polypeptide-associated complex, is responsible for the transcriptional initiation of RNA polymerase II and is also involved in cell apoptosis, translation initiation regulation, growth, development, and other functions. Here, we report the impact of BTF3 on abiotic tolerance in higher plants. The transcription levels of the TaBTF3 gene, first isolated from wheat seedlings in our lab, were differentially regulated by diverse abiotic stresses and hormone treatments, including PEG-induced stress (20 % polyethylene glycol 6000), cold (4 °C), salt (100 mM NaCl), abscisic acid (100 ?M), methyl jasmonate (50 ?M), and salicylic acid (50 ?M). Southern blot analysis indicated that, in the wheat genome, TaBTF3 is a multi-copy gene. Compared to BSMV-GFP-infected wheat plants (control), under freezing (-8 °C for 48 h) or drought stress (withholding water for 15 days) conditions, TaBTF3-silenced wheat plants showed lower survival rates, free proline content, and relative water content and higher relative electrical conductivity and water loss rate. These results suggest that silencing of the TaBTF3 gene may impair tolerance to freezing and drought stresses in wheat and that it may be involved in the response to abiotic stresses in higher plants. PMID:23942841

Kang, Guozhang; Ma, Hongzhen; Liu, Guoqin; Han, Qiaoxia; Li, Chengwei; Guo, Tiancai

2013-08-14

293

Global DNA hypomethylation coupled to repressive chromatin domain formation and gene silencing in breast cancer  

PubMed Central

While genetic mutation is a hallmark of cancer, many cancers also acquire epigenetic alterations during tumorigenesis including aberrant DNA hypermethylation of tumor suppressors, as well as changes in chromatin modifications as caused by genetic mutations of the chromatin-modifying machinery. However, the extent of epigenetic alterations in cancer cells has not been fully characterized. Here, we describe complete methylome maps at single nucleotide resolution of a low-passage breast cancer cell line and primary human mammary epithelial cells. We find widespread DNA hypomethylation in the cancer cell, primarily at partially methylated domains (PMDs) in normal breast cells. Unexpectedly, genes within these regions are largely silenced in cancer cells. The loss of DNA methylation in these regions is accompanied by formation of repressive chromatin, with a significant fraction displaying allelic DNA methylation where one allele is DNA methylated while the other allele is occupied by histone modifications H3K9me3 or H3K27me3. Our results show a mutually exclusive relationship between DNA methylation and H3K9me3 or H3K27me3. These results suggest that global DNA hypomethylation in breast cancer is tightly linked to the formation of repressive chromatin domains and gene silencing, thus identifying a potential epigenetic pathway for gene regulation in cancer cells.

Hon, Gary C.; Hawkins, R. David; Caballero, Otavia L.; Lo, Christine; Lister, Ryan; Pelizzola, Mattia; Valsesia, Armand; Ye, Zhen; Kuan, Samantha; Edsall, Lee E.; Camargo, Anamaria Aranha; Stevenson, Brian J.; Ecker, Joseph R.; Bafna, Vineet; Strausberg, Robert L.; Simpson, Andrew J.; Ren, Bing

2012-01-01

294

A 3'-flanking NF-kappaB site mediates developmental silencing of the human zeta-globin gene.  

PubMed Central

The central developmental event in the human (h)alpha-globin gene cluster is selective silencing of the zeta-globin gene as erythropoiesis shifts from primitive erythroblasts in the embryonic yolk sac to definitive erythroblasts in the fetal liver. Previous studies have demonstrated that full developmental silencing of the hzeta-globin gene in transgenic mice requires the proximal 2.1 kb of its 3'-flanking region. In the current report, we localize this silencing activity to a 108 bp segment located 1.2 kb 3' to the zeta-globin gene. Protein(s) in nuclear extracts from cell lines representing the fetal/adult erythroid stage bind specifically to an NF-kappaB motif located at this site. In contrast, this binding activity is lacking in the nuclear extract of an embryonic-stage erythroid line expressing zeta-globin. This complex is quantitatively recognized by antisera to the NF-kappaB p50 and to a lesser extent to p65 subunits. A two-base substitution that disrupts NF-kappaB site protein binding in vitro also results in the loss of the developmental silencing activity in vivo. The data suggest that NF-kappaB complex formation is a crucial component of hzeta-globin gene silencing. This finding expands the roles of this widely distributed transcriptional complex to include negative regulation in mammalian development.

Wang, Z; Liebhaber, S A

1999-01-01

295

Spreading the silence.  

PubMed

RITS (RNA-induced initiation of transcriptional gene silencing complex) plays diverse roles in heterochromatin regulation: silencing transcription by recruitment of chromatin modifiers and destroying transcripts by RNAi. In a recent issue of Molecular Cell, Li et al. now show that the polymerization of Tas3, a component of RITS, contributes to the spreading of silencing mediated by RITS. PMID:19460340

Partridge, Janet F

2009-05-01

296

An RNA-Dependent RNA Polymerase Gene in Arabidopsis Is Required for Posttranscriptional Gene Silencing Mediated by a Transgene but Not by a Virus  

Microsoft Academic Search

Posttranscriptional gene silencing is a defense mechanism in plants that is similar to quelling in fungi and RNA interference in animals. Here, we describe four genetic loci that are required for posttranscriptional gene silencing in Arabidopsis. One of these, SDE1, is a plant homolog of QDE-1 in Neurospora crassa that encodes an RNA-dependent RNA polymerase. The sde1 mutation was specific

Tamas Dalmay; Andrew Hamilton; Stephen Rudd; Susan Angell; David C. Baulcombe

2000-01-01

297

A comparison between analytic and numerical methods for modelling automotive dissipative silencers with mean flow  

NASA Astrophysics Data System (ADS)

Identifying an appropriate method for modelling automotive dissipative silencers normally requires one to choose between analytic and numerical methods. It is common in the literature to justify the choice of an analytic method based on the assumption that equivalent numerical techniques are more computationally expensive. The validity of this assumption is investigated here, and the relative speed and accuracy of two analytic methods are compared to two numerical methods for a uniform dissipative silencer that contains a bulk reacting porous material separated from a mean gas flow by a perforated pipe. The numerical methods are developed here with a view to speeding up transmission loss computation, and are based on a mode matching scheme and a hybrid finite element method. The results presented demonstrate excellent agreement between the analytic and numerical models provided a sufficient number of propagating acoustic modes are retained. However, the numerical mode matching method is shown to be the fastest method, significantly outperforming an equivalent analytic technique. Moreover, the hybrid finite element method is demonstrated to be as fast as the analytic technique. Accordingly, both numerical techniques deliver fast and accurate predictions and are capable of outperforming equivalent analytic methods for automotive dissipative silencers.

Kirby, R.

2009-08-01

298

White as a Reporter Gene to Detect Transcriptional Silencers Specifying Position-Specific Gene Expression during Drosophila Melanogaster Eye Development  

PubMed Central

The white(+) gene was used as a reporter to detect transcriptional silencer activity in the Drosophila genome. Changes in the spatial expression pattern of white were scored in the adult eye as nonuniform patterns of pigmentation. Thirty-six independent P[lacW] transposant lines were collected. These represent 12 distinct pigmentation patterns and probably 21 loci. The spatial pigmentation pattern is due to cis-acting suppression of white(+) expression, and the suppression probably depends on cell position rather than cell type. The mechanism of suppression differs from inactivation by heterochromatin. In addition, activation of lacZ in P[lacW] occurs also in specific patterns in imaginal discs and embryos in many of the lines. The expression patterns of white(+) and lacZ may reflect the activity of regulatory elements belonging to an endogenous gene near each P[lacW] insertion site. We speculate that these putative POSE (position-specific expression) genes may have a role in pattern formation of the eye as well as other imaginal structures. Three of the loci identified are optomotor-blind, engrailed and invected. teashirt is also implicated as a candidate gene. We propose that this ``silencer trap'' may be an efficient way of identifying genes involved in imaginal pattern formation.

Sun, Y. H.; Tsai, C. J.; Green, M. M.; Chao, J. L.; Yu, C. T.; Jaw, T. J.; Yeh, J. Y.; Bolshakov, V. N.

1995-01-01

299

Efficient silencing of gene expression with modular trimeric Pol II expression cassettes comprising microRNA shuttles  

PubMed Central

Expressed polycistronic microRNA (miR) cassettes have useful properties that can be utilized for RNA interference (RNAi)-based gene silencing. To advance their application we generated modular trimeric anti-hepatitis B virus (HBV) Pol II cassettes encoding primary (pri)-miR-31-derived shuttles that target three different viral genome sites. A panel of six expression cassettes, comprising each of the possible ordering combinations of the pri-miR-31 shuttles, was initially tested. Effective silencing of individual target sequences was achieved in transfected cells and transcribed pri-miR trimers generated intended guide strands. There was, however, variation in processing and silencing by each of the shuttles. In some cases the monomers’ position within the trimers influenced processing and this correlated with target silencing. Compromised efficacy could be compensated by substituting the pri-miR-31 backbone with a pri-miR-30a scaffold. Inhibition of HBV replication was achieved in vivo, and in cell culture without disruption of endogenous miR function or induction of the interferon response. A mutant HBV target sequence, with changes in one of the guide cognates, was also silenced by the trimeric cassettes. The modular nature of the cassettes together with compatibility with expression from Pol II promoters should be advantageous for gene silencing applications requiring simultaneous targeting of different sites.

Ely, Abdullah; Naidoo, Tanusha; Arbuthnot, Patrick

2009-01-01

300

Suppression of RNA Silencing by a Geminivirus Nuclear Protein, AC2, Correlates with Transactivation of Host Genes  

PubMed Central

Bipartite geminiviruses encode a small protein, AC2, that functions as a transactivator of viral transcription and a suppressor of RNA silencing. A relationship between these two functions had not been investigated before. We characterized both of these functions for AC2 from Mungbean yellow mosaic virus-Vigna (MYMV). When transiently expressed in plant protoplasts, MYMV AC2 strongly transactivated the viral promoter; AC2 was detected in the nucleus, and a split nuclear localization signal (NLS) was mapped. In a model Nicotiana benthamiana plant, in which silencing can be triggered biolistically, AC2 reduced local silencing and prevented its systemic spread. Mutations in the AC2 NLS or Zn finger or deletion of its activator domain abolished both these effects, suggesting that suppression of silencing by AC2 requires transactivation of host suppressor(s). In line with this, in Arabidopsis protoplasts, MYMV AC2 or its homologue from African cassava mosaic geminivirus coactivated >30 components of the plant transcriptome, as detected with Affymetrix ATH1 GeneChips. Several corresponding promoters cloned from Arabidopsis were strongly induced by both AC2 proteins. These results suggest that silencing suppression and transcription activation by AC2 are functionally connected and that some of the AC2-inducible host genes discovered here may code for components of an endogenous network that controls silencing.

Trinks, Daniela; Rajeswaran, R.; Shivaprasad, P. V.; Akbergenov, Rashid; Oakeley, Edward J.; Veluthambi, K.; Hohn, Thomas; Pooggin, Mikhail M.

2005-01-01

301

Dissecting Epigenetic Silencing Complexity in the Mouse Lung Cancer Suppressor Gene Cadm1  

PubMed Central

Disease-oriented functional analysis of epigenetic factors and their regulatory mechanisms in aberrant silencing is a prerequisite for better diagnostics and therapy. Yet, the precise mechanisms are still unclear and complex, involving the interplay of several effectors including nucleosome positioning, DNA methylation, histone variants and histone modifications. We investigated the epigenetic silencing complexity in the tumor suppressor gene Cadm1 in mouse lung cancer progenitor cell lines, exhibiting promoter hypermethylation associated with transcriptional repression, but mostly unresponsive to demethylating drug treatments. After predicting nucleosome positions and transcription factor binding sites along the Cadm1 promoter, we carried out single-molecule mapping with DNA methyltransferase M.SssI, which revealed in silent promoters high nucleosome occupancy and occlusion of transcription factor binding sites. Furthermore, M.SssI maps of promoters varied within and among the different lung cancer cell lines. Chromatin analysis with micrococcal nuclease also indicated variations in nucleosome positioning to have implications in the binding of transcription factors near nucleosome borders. Chromatin immunoprecipitation showed that histone variants (H2A.Z and H3.3), and opposing histone modification marks (H3K4me3 and H3K27me3) all colocalized in the same nucleosome positions that is reminiscent of epigenetic plasticity in embryonic stem cells. Altogether, epigenetic silencing complexity in the promoter region of Cadm1 is not only defined by DNA hypermethylation, but high nucleosome occupancy, altered nucleosome positioning, and ‘bivalent’ histone modifications, also likely contributed in the transcriptional repression of this gene in the lung cancer cells. Our results will help define therapeutic intervention strategies using epigenetic drugs in lung cancer.

Reamon-Buettner, Stella Marie; Borlak, Juergen

2012-01-01

302

Oxidative Stress Can Affect the Gene Silencing Effect of DOTAP Liposome in an In Vitro Translation System  

PubMed Central

Oxidative stress can affect in vitro GFP expression through its control of the gene silencing effect of the liposome prepared by 1,2-dioleoyl-3-trimethyl-ammonium propane (DOTAP). The gene silencing effect of cationic DOTAP liposome in in vitro GFP expression, especially focusing on its translation process, and the effects of oxidative stress on its silencing effect were investigated. GFP expression, initiated by mRNA, was found to be thoroughly inhibited in the presence of DOTAP liposome at concentration of more than 2.5 mM, though its inhibitory effect was reduced in the presence of hydrogen peroxide. The analyses of (i) the interaction of mRNA with DOTAP, (ii) the chemical structure of DOTAP, and (iii) the membrane fluidity of DOTAP liposome imply the possible role of gene expression by the liposome membrane and stress conditions.

Umakoshi, Hiroshi; Tanabe, Tomoyuki; Suga, Keishi; Bui, Huong Thi; Shimanouchi, Toshinori; Kuboi, Ryoichi

2011-01-01

303

The Chp1-Tas3 core is a multifunctional platform critical for gene silencing by RITS  

PubMed Central

RNA interference (RNAi) is critical for the assembly of heterochromatin at fission yeast centromeres. Central to this process is the RNA-induced Initiation of Transcriptional gene Silencing (RITS) complex, which physically anchors small non-coding RNAs to chromatin. RITS includes Ago1, the chromodomain protein Chp1, and Tas3, which bridges between Chp1 and Ago1. Chp1 is a large protein with, apart from its chromodomain, no recognizable domains. Here we describe how the structured C-terminal half of Chp1 binds the Tas3 N-terminal domain, revealing Chp1's tight embrace of Tas3. The structure also reveals a PIN domain at the C-terminal tip of Chp1 that controls subtelomeric transcripts through a post-transcriptional mechanism. We suggest that the Chp1-Tas3 complex provides a solid and versatile platform to recruit both RNAi-dependent and RNAi-independent gene-silencing pathways for locus-specific regulation of heterochromatin.

Schalch, Thomas; Job, Godwin; Shanker, Sreenath; Partridge, Janet F.; Joshua-Tor, Leemor

2011-01-01

304

Combined Multi-modal Optical Imaging and Targeted Gene Silencing Using Stimuli-transforming Nanotheragnostics  

PubMed Central

Combined diagnosis and therapy for cancer has been of great interest in medicine. Small interference RNA (siRNA)-encapsulating polyplexes were covalently coated with small gold nanoparticles (Au NPs) via acid-cleavable linkages in order to explore the possibility of achieving combined stimuli-responsive multi-modal optical imaging and stimuli-enhanced gene silencing. In a mildly acidic tumor environment, Au NPs are dissociated from the siRNA-carrying polyplexes, generating various optical signal changes such as diminished scattering intensity, increased variance of Doppler frequency, and blue-shifted UV absorbance (stimuli-responsive imaging). Simultaneously, Au NP dissociation exposes the siRNA-carrying polyplex with elevated surface charge and results in enhanced cellular uptake and transfection (stimuli-enhanced therapy). In this study, the feasibility of achieving combined diagnosis and therapy for cancer (theragnostics) is demonstrated by 1) microscopic and spectrophotometric confirmation of acid-transformation of the nanoparticles, 2) reduced scattering intensity and increased variance of Doppler frequency in an acidic pH upon the nanoparticle’s transformation, and 3) simultaneous optical signal changes and gene silencing in vitro under a tumor pH-mimicking condition. This novel type of stimuli-responsive nanotheragnostics will provide a new paradigm for pinpointed, multi-modal, and combined imaging and therapy for cancer.

Shim, Min Suk; Kim, Chang Soo; Ahn, Yeh-Chan; Chen, Zhongping; Kwon, Young Jik

2010-01-01

305

Transformation of the flax rust fungus, Melampsora lini: selection via silencing of an avirulence gene  

PubMed Central

SUMMARY Rust fungi cause devastating diseases on many important food crops, with a damaging stem rust epidemic currently affecting wheat production in Africa and the Middle East. These parasitic fungi propagate exclusively on plants, precluding the use of many biotechnological tools available for other culturable fungi. In particular the lack of a stable transformation system has been an impediment to the genetic manipulation required for molecular analysis of rust pathogenicity. We have developed an Agrobacterium-mediated genetic transformation procedure for the model flax rust fungus Melampsora lini, which infects flax (Linum usitatissimum). Selection of transgenic rust lines is based on silencing of AvrL567, which encodes a rust effector protein that is recognised by the flax L6 immune receptor. The non-transgenic rust line is unable to infect flax plants expressing L6, while silenced transgenic lines are virulent on these plants, providing an effective selection system. This directly confirms that the cloned AvrL567 gene is responsible for flax rust virulence phenotypes, and demonstrates the utility of this system to probe rust gene function.

Lawrence, Gregory J.; Dodds, Peter N.; Ellis, Jeffrey G.

2011-01-01

306

The Chp1-Tas3 core is a multifunctional platform critical for gene silencing by RITS.  

PubMed

RNA interference (RNAi) is critical for the assembly of heterochromatin at Schizosaccharomyces pombe centromeres. Central to this process is the RNA-induced initiation of transcriptional gene silencing (RITS) complex, which physically anchors small noncoding RNAs to chromatin. RITS includes Ago1, the chromodomain protein Chp1, and Tas3, which forms a bridge between Chp1 and Ago1. Chp1 is a large protein with no recognizable domains, apart from its chromodomain. Here we describe how the structured C-terminal half of Chp1 binds the Tas3 N-terminal domain, revealing the tight association of Chp1 and Tas3. The structure also shows a PIN domain at the C-terminal tip of Chp1 that controls subtelomeric transcripts through a post-transcriptional mechanism. We suggest that the Chp1-Tas3 complex provides a solid and versatile platform to recruit both RNAi-dependent and RNAi-independent gene-silencing pathways for locus-specific regulation of heterochromatin. PMID:22081013

Schalch, Thomas; Job, Godwin; Shanker, Sreenath; Partridge, Janet F; Joshua-Tor, Leemor

2011-11-13

307

Angiotensinogen Gene Silencing Reduces Markers of Lipid Accumulation and Inflammation in Cultured Adipocytes  

PubMed Central

Inflammatory adipokines secreted from adipose tissue are major contributors to obesity-associated inflammation and other metabolic dysfunctions. We and others have recently documented the contribution of adipose tissue renin-angiotensin system to the pathogenesis of obesity, inflammation, and insulin resistance. We hypothesized that adipocyte-derived angiotensinogen (Agt) plays a critical role in adipogenesis and/or lipogenesis as well as inflammation. This was tested using 3T3-L1 adipocytes, stably transfected with Agt-shRNA or scrambled Sc-shRNA as a control. Transfected preadipocytes were differentiated and used to investigate the role of adipose Agt through microarray and PCR analyses and adipokine profiling. As expected, Agt gene silencing significantly reduced the expression of Agt and its hormone product angiotensin II (Ang II), as well as lipid accumulation in 3T3-L1 adipocytes. Microarray studies identified several genes involved in lipid metabolism and inflammatory pathways which were down-regulated by Agt gene inactivation, such as glycerol-3-phosphate dehydrogenase 1 (Gpd1), serum amyloid A 3 (Saa3), nucleotide-binding oligomerization domain containing 1 (Nod1), and signal transducer and activator of transcription 1 (Stat1). Mouse adipogenesis PCR arrays revealed lower expression levels of adipogenic/lipogenic genes such as peroxisome proliferator activated receptor gamma (PPAR?), sterol regulatory element binding transcription factor 1 (Srebf1), adipogenin (Adig), and fatty acid binding protein 4 (Fabp4). Further, silencing of Agt gene significantly lowered expression of pro-inflammatory adipokines including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-?), and monocyte chemotactic protein-1 (MCP-1). In conclusion, this study directly demonstrates critical effects of Agt in adipocyte metabolism and inflammation and further support a potential role for adipose Agt in the pathogenesis of obesity-associated metabolic alterations.

Carroll, Wenting X.; Kalupahana, Nishan S.; Booker, Suzanne L.; Siriwardhana, Nalin; LeMieux, Monique; Saxton, Arnold M.; Moustaid-Moussa, Naima

2013-01-01

308

Role of hPHF1 in H3K27 methylation and Hox gene silencing.  

PubMed

Polycomb group (PcG) proteins are required for maintaining the silent state of the homeotic genes and other important developmental regulators. The silencing function of the PcG proteins has been linked to their intrinsic histone modifying enzymatic activities. The EED-EZH2 complex, containing the core subunits EZH2, EED, SUZ12, and RbAp48, functions as a histone H3K27-specific methyltransferase. Here we describe the identification and characterization of a related EED-EZH2 protein complex which is distinguished from the previous complex by the presence of another PcG protein, hPHF1. Consistent with the ability of hPHF1 to stimulate the enzymatic activity of the core EED-EZH2 complex in vitro, manipulation of mPcl1, the mouse counterpart of hPHF1, in NIH 3T3 cells and cells of the mouse male germ cell line GC1spg results in global alteration of H3K27me2 and H3K27me3 levels and Hox gene expression. Small interfering RNA-mediated knockdown of mPcl1 affects association of the Eed-Ezh2 complex with certain Hox genes, such as HoxA10, as well as Hox gene expression concomitant with an alteration on the H3K27me2 levels of the corresponding promoters. Therefore, our results reveal hPHF1 as a component of a novel EED-EZH2 complex and demonstrate its important role in H3K27 methylation and Hox gene silencing. PMID:18086877

Cao, Ru; Wang, Hengbin; He, Jin; Erdjument-Bromage, Hediye; Tempst, Paul; Zhang, Yi

2007-12-17

309

Heterochromatic genes undergo epigenetic changes and escape silencing in immunodeficiency, centromeric instability, facial anomalies (ICF) syndrome.  

PubMed

Immunodeficiency, Centromeric Instability, Facial Anomalies (ICF) syndrome is a rare autosomal recessive disorder that is characterized by a marked immunodeficiency, severe hypomethylation of the classical satellites 2 and 3 associated with disruption of constitutive heterochromatin, and facial anomalies. Sixty percent of ICF patients have mutations in the DNMT3B (DNA methyltransferase 3B) gene, encoding a de novo DNA methyltransferase. In the present study, we have shown that, in ICF lymphoblasts and peripheral blood, juxtacentromeric heterochromatic genes undergo dramatic changes in DNA methylation, indicating that they are bona fide targets of the DNMT3B protein. DNA methylation in heterochromatic genes dropped from about 80% in normal cells to approximately 30% in ICF cells. Hypomethylation was observed in five ICF patients and was associated with activation of these silent genes. Although DNA hypomethylation occurred in all the analyzed heterochromatic genes and in all the ICF patients, gene expression was restricted to some genes, every patient having his own group of activated genes. Histone modifications were preserved in ICF patients. Heterochromatic genes were associated with histone modifications that are typical of inactive chromatin: they had low acetylation on H3 and H4 histones and were slightly enriched in H3K9Me(3), both in ICF and controls. This was also the case for those heterochromatic genes that escaped silencing. This finding suggests that gene activation was not generalized to all the cells, but rather was restricted to a clonal cell population that may contribute to the phenotypic variability observed in ICF syndrome. A slight increase in H3K27 monomethylation was observed both in heterochromatin and active euchromatin in ICF patients; however, no correlation between this modification and activation of heterochromatic genes was found. PMID:21559330

Brun, Marie-Elisabeth; Lana, Erica; Rivals, Isabelle; Lefranc, Gérard; Sarda, Pierre; Claustres, Mireille; Mégarbané, André; De Sario, Albertina

2011-04-29

310

HC-Pro silencing suppressor significantly alters the gene expression profile in tobacco leaves and flowers  

PubMed Central

Background RNA silencing is used in plants as a major defence mechanism against invasive nucleic acids, such as viruses. Accordingly, plant viruses have evolved to produce counter defensive RNA-silencing suppressors (RSSs). These factors interfere in various ways with the RNA silencing machinery in cells, and thereby disturb the microRNA (miRNA) mediated endogene regulation and induce developmental and morphological changes in plants. In this study we have explored these effects using previously characterized transgenic tobacco plants which constitutively express (under CaMV 35S promoter) the helper component-proteinase (HC-Pro) derived from a potyviral genome. The transcript levels of leaves and flowers of these plants were analysed using microarray techniques (Tobacco 4 × 44 k, Agilent). Results Over expression of HC-Pro RSS induced clear phenotypic changes both in growth rate and in leaf and flower morphology of the tobacco plants. The expression of 748 and 332 genes was significantly changed in the leaves and flowers, respectively, in the HC-Pro expressing transgenic plants. Interestingly, these transcriptome alterations in the HC-Pro expressing tobacco plants were similar as those previously detected in plants infected with ssRNA-viruses. Particularly, many defense-related and hormone-responsive genes (e.g. ethylene responsive transcription factor 1, ERF1) were differentially regulated in these plants. Also the expression of several stress-related genes, and genes related to cell wall modifications, protein processing, transcriptional regulation and photosynthesis were strongly altered. Moreover, genes regulating circadian cycle and flowering time were significantly altered, which may have induced a late flowering phenotype in HC-Pro expressing plants. The results also suggest that photosynthetic oxygen evolution, sugar metabolism and energy levels were significantly changed in these transgenic plants. Transcript levels of S-adenosyl-L-methionine (SAM) were also decreased in these plants, apparently leading to decreased transmethylation capacity. The proteome analysis using 2D-PAGE indicated significantly altered proteome profile, which may have been both due to altered transcript levels, decreased translation, and increased proteosomal/protease activity. Conclusion Expression of the HC-Pro RSS mimics transcriptional changes previously shown to occur in plants infected with intact viruses (e.g. Tobacco etch virus, TEV). The results indicate that the HC-Pro RSS contributes a significant part of virus-plant interactions by changing the levels of multiple cellular RNAs and proteins.

2011-01-01

311

Developmental silencing of the embryonic zeta-globin gene: concerted action of the promoter and the 3'-flanking region combined with stage-specific silencing by the transcribed segment.  

PubMed

Globin gene switching is a well-described model of eucaryotic developmental control. In the case of the human alpha-globin gene cluster, migration of erythropoietic activity from the embryonic yolk sac to the fetal liver is parallaled by the zeta-globin gene silencing and enhanced expression of the alpha-globin genes. To map critical cis determinants of this switch, the human zeta-globin gene, the alpha-globin gene, and chimeric recombinants were introduced into the mouse genome. Consistent with previous studies, expression of the individual alpha- and zeta-globin transgenes was found to be developmentally appropriate. Contrary to current models, however, the alpha- and zeta-globin gene promoters were not sufficient to establish this control. Instead, full silencing of the zeta-globin gene required the combined activities of this promoter, transcribed region, and 3'-flanking sequences. Individually, the silencing activities of the zeta-globin gene promoter and 3'-flanking region were minimal but increased markedly when both regions were present. The zeta-globin transcribed region appeared to contribute to gene silencing by a mechanism specifically activated in definitive erythroblasts in the fetal liver. These data demonstrate that a complex set of controls, requiring at least three determinants and involving at least two independent mechanisms, is necessary for full developmental silencing of the human zeta-globin gene. PMID:8649371

Liebhaber, S A; Wang, Z; Cash, F E; Monks, B; Russell, J E

1996-06-01

312

Geminivirus-Mediated Gene Silencing from Cotton Leaf Crumple Virus Is Enhanced by Low Temperature in Cotton1[C][OA  

PubMed Central

A silencing vector for cotton (Gossypium hirsutum) was developed from the geminivirus Cotton leaf crumple virus (CLCrV). The CLCrV coat protein gene was replaced by up to 500 bp of DNA homologous to one of two endogenous genes, the magnesium chelatase subunit I gene (ChlI) or the phytoene desaturase gene (PDS). Cotyledons of cotton cultivar ‘Deltapine 5415’ bombarded with the modified viral vectors manifested chlorosis due to silencing of either ChlI or PDS in approximately 70% of inoculated plants after 2 to 3 weeks. Use of the green fluorescence protein gene showed that replication of viral DNA was restricted to vascular tissue and that the viral vector could transmit to leaves, roots, and the ovule integument from which fibers originate. Temperature had profound effects on vector DNA accumulation and the spread of endogenous gene silencing. Consistent with reports that silencing against viruses increases at higher temperatures, plants grown at a 30°C/26°C day/night cycle had a greater than 10-fold reduction in viral DNA accumulation compared to plants grown at 22°C/18°C. However, endogenous gene silencing decreased at 30°C/26°C. There was an approximately 7 d delay in the onset of gene silencing at 22°C/18°C, but silencing was extensive and persisted throughout the life of the plant. The extent of silencing in new growth could be increased or decreased by changing temperature regimes at various times following the onset of silencing. Our experiments establish the use of the CLCrV silencing vector to study gene function in cotton and show that temperature can have a major impact on the extent of geminivirus-induced gene silencing.

Tuttle, John R.; Idris, A.M.; Brown, Judith K.; Haigler, Candace H.; Robertson, Dominique

2008-01-01

313

An RNA-Seq Transcriptome Analysis of Histone Modifiers and RNA Silencing Genes in Soybean during Floral Initiation Process.  

PubMed

Epigenetics has been recognised to play vital roles in many plant developmental processes, including floral initiation through the epigenetic regulation of gene expression. The histone modifying proteins that mediate these modifications involve the SET domain-containing histone methyltransferases, JmjC domain-containing demethylase, acetylases and deacetylases. In addition, RNA interference (RNAi)-associated genes are also involved in epigenetic regulation via RNA-directed DNA methylation and post-transcriptional gene silencing. Soybean, a major crop legume, requires a short day to induce flowering. How histone modifications regulate the plant response to external cues that initiate flowering is still largely unknown. Here, we used RNA-seq to address the dynamics of transcripts that are potentially involved in the epigenetic programming and RNAi mediated gene silencing during the floral initiation of soybean. Soybean is a paleopolyploid that has been subjected to at least two rounds of whole genome duplication events. We report that the expanded genomic repertoire of histone modifiers and RNA silencing genes in soybean includes 14 histone acetyltransferases, 24 histone deacetylases, 47 histone methyltransferases, 15 protein arginine methyltransferases, 24 JmjC domain-containing demethylases and 47 RNAi-associated genes. To investigate the role of these histone modifiers and RNA silencing genes during floral initiation, we compared the transcriptional dynamics of the leaf and shoot apical meristem at different time points after a short-day treatment. Our data reveal that the extensive activation of genes that are usually involved in the epigenetic programming and RNAi gene silencing in the soybean shoot apical meristem are reprogrammed for floral development following an exposure to inductive conditions. PMID:24147010

Liew, Lim Chee; Singh, Mohan B; Bhalla, Prem L

2013-10-16

314

An RNA-Seq Transcriptome Analysis of Histone Modifiers and RNA Silencing Genes in Soybean during Floral Initiation Process  

PubMed Central

Epigenetics has been recognised to play vital roles in many plant developmental processes, including floral initiation through the epigenetic regulation of gene expression. The histone modifying proteins that mediate these modifications involve the SET domain-containing histone methyltransferases, JmjC domain-containing demethylase, acetylases and deacetylases. In addition, RNA interference (RNAi)-associated genes are also involved in epigenetic regulation via RNA-directed DNA methylation and post-transcriptional gene silencing. Soybean, a major crop legume, requires a short day to induce flowering. How histone modifications regulate the plant response to external cues that initiate flowering is still largely unknown. Here, we used RNA-seq to address the dynamics of transcripts that are potentially involved in the epigenetic programming and RNAi mediated gene silencing during the floral initiation of soybean. Soybean is a paleopolyploid that has been subjected to at least two rounds of whole genome duplication events. We report that the expanded genomic repertoire of histone modifiers and RNA silencing genes in soybean includes 14 histone acetyltransferases, 24 histone deacetylases, 47 histone methyltransferases, 15 protein arginine methyltransferases, 24 JmjC domain-containing demethylases and 47 RNAi-associated genes. To investigate the role of these histone modifiers and RNA silencing genes during floral initiation, we compared the transcriptional dynamics of the leaf and shoot apical meristem at different time points after a short-day treatment. Our data reveal that the extensive activation of genes that are usually involved in the epigenetic programming and RNAi gene silencing in the soybean shoot apical meristem are reprogrammed for floral development following an exposure to inductive conditions.

Liew, Lim Chee; Singh, Mohan B.; Bhalla, Prem L.

2013-01-01

315

Correction: RNA interference-mediated gene silencing in murine T cells: in vitro and in vivo validation of proinflammatory target genes  

Microsoft Academic Search

T cells play a central role in many inflammatory diseases, hence the identification and validation of T cell-specific target genes will increase the understanding of T cell function in pathologic inflammatory situations. RNA interference (RNAi), with its ability to induce specific gene silencing in mammalian cells, represents a powerful technology to investigate and validate the function of pharmaceutical target genes

Tatjana C Gust; Luisa Neubrandt; Claudia Merz; Khusru Asadullah; Ulrich Zügel; Arne von Bonin

2008-01-01

316

Virus-Induced Gene Silencing in the Culinary Ginger (Zingiber officinale): An Effective Mechanism for Down-Regulating Gene Expression in Tropical Monocots  

Microsoft Academic Search

Virus-induced gene silencing (VIGS) has been shown to be effective for transient knockdown of gene expres- sion in plants to analyze the effects of specific genes in development and stress-related responses. VIGS is well established for studies of model systems and crops within the Solanaceae, Brassicaceae, Leguminaceae, and Poaceae, but only recently has been applied to plants residing outside these

Tanya Renner; J. Bragg; Heather E. Driscoll; Juliana Cho; Andrew O. Jackson; Chelsea D. Specht

2009-01-01

317

Gene silencing in vitro and in vivo using intronic microRNAs.  

PubMed

MicroRNAs (miRNAs), small single-stranded regulatory RNAs capable of interfering with intracellular messenger RNAs (mRNAs) that contain either complete or partial complementarity, are useful for the design of new therapies against cancer polymorphism and viral mutation. Numerous miRNAs have been reported to induce RNA interference (RNAi), a posttranscriptional gene-silencing mechanism. Recent evidence also indicates that they are involved in the transcriptional regulation of genome activities. They were first discovered in Caenorhabditis elegans as native RNA fragments that modulate a wide range of genetic regulatory pathways during embryonic development and are now recognized as small gene silencers transcribed from the noncoding regions of a genome. In humans, nearly 97% of the genome is noncoding DNA, which varies from one individual to another, and changes in these sequences are frequently noted to manifest in clinical and circumstantial malfunction; for example, type 2 myotonic dystrophy and fragile X syndrome were found to be associated with miRNAs derived from introns. Intronic miRNA is a new class of miRNAs derived from the processing of nonprotein-coding regions of gene transcripts. The intronic miRNAs differ uniquely from previously described intergenic miRNAs in the requirement of RNA polymerase (Pol)-II and spliceosomal components for its biogenesis. Several kinds of intronic miRNAs have been identified in C. elegans, mouse, and human cells; however, their functions and applications have not been reported. Here, we show for the first time that intron-derived miRNA is not only able to induce RNAi in mammalian cells, but also in fish, chicken embryos, and adult mice cells, demonstrating the evolutionary preservation of this gene regulation system in vivo. These miRNA-mediated animal models provide artificial means to reproduce the mechanisms of miRNA-induced disease in vivo and will shed further light on miRNA-related therapies. PMID:23007511

Lin, Shi-Lung; Ying, Shao-Yao

2013-01-01

318

Frequent Epigenetic Silencing of the Folate-Metabolising Gene Cystathionine-Beta-Synthase in Gastrointestinal Cancer  

PubMed Central

Background Both gastric and colorectal cancers (CRC) are the most frequently occurring malignancies worldwide with the overall survival of these patients remains unsatisfied. Identification of tumor suppressor genes (TSG) silenced by promoter CpG methylation uncovers mechanisms of tumorigenesis and identifies new epigenetic biomarkers for early cancer detection and prognosis assessment. Cystathionine-beta-synthase (CBS) functions in the folate metabolism pathway, which is intricately linked to methylation of genomic DNA. Dysregulation of DNA methylation contributes substantially to cancer development. Methodology/Principal Findings To identify potential TSGs silenced by aberrant promoter methylation in CRC, we analyzed tumor and adjacent tissues from CRC cases using the Illumina Human Methylation45 BeadChip. We identified hypermethylation of the CBS gene in CRC samples, compared to adjacent tissues. Methylation and decreased mRNA expression of CBS were detected in most CRC cell lines by methylation-specific PCR and semiquantitative RT-PCR, as well as in gastric cancer. Treatment with 5-aza-2'-deoxycytidine and/or trichostatin A reversed methylation and restored CBS mRNA expression indicating a direct effect. Aberrant methylation was further detected in 31% of primary CRCs (29 of 96) and 55% of gastric tumors (11 of 20). In contrast, methylation was seldom found in normal tissues adjacent to the tumor. CBS methylation was associated with KRAS mutations in primary CRCs (P?=?0.04, by ?2-test). However, no association was found between CBS methylation or KRAS mutations with cancer relapse/metastasis in Stage II CRC patients. Conclusion A novel finding from this study is that the folate metabolism enzyme CBS mRNA levels are frequently downregulated through CpG methylation of the CBS gene in gastric cancer and CRC, suggesting that CBS functions as a tumor suppressor gene. These findings warrant further study of CBS as an epigenetic biomarker for molecular diagnosis of gastrointestinal cancers.

Wang, Jian; Su, Xianwei; Ng, Ka Man; Qiu, Tian; Shan, Ling; Ling, Yun; Wang, Linfang; Cai, Jianqiang; Ying, Jianming

2012-01-01

319

Chitosan-modified poly(D,L-lactide-co-glycolide) nanospheres for plasmid DNA delivery and HBV gene-silencing.  

PubMed

Gene silencing using small interfering RNA (siRNA) has several potential therapeutic applications. In the present study, we investigated nanoparticles (NS) formulated using the biodegradable polymer, poly(D,L-lactide-co-glycolide) (PLGA) for plasmid DNA (pDNA) delivery. A cationic polymer, Chitosan (CHS), was incorporated in the PLGA matrix to improve pDNA loading efficiency and cellular uptake ability. PLGA-CHS NS were prepared by a spontaneous emulsion diffusion (SED) method, and various formulation factors were investigated. Spherical nanoparticles with particle size of around 60 nm were obtained under optimum formulation condition. The effectiveness of pDNA-loaded PLGA-CHS nanoparticles in expressing the indicative enhanced Green Fluorescent Protein (eGFP) and in slicing Hepatitis B virus (HBV) gene were examined in HepG2.2.15 cells. CHS-modified PLGA NS exhibited much higher loading efficiency than unmodified PLGA NS. CHS-PLGA NS showed a positive zeta potential, while plain-PLGA NS were negatively charged. EGFP expression studies by observation with confocal leaser scanning microscopy (CLSM) indicated that pDNA-loaded CHS-PLGA NS were more effectively taken up by the cells than plain-PLGA NS. The corresponding results showed that the HBV gene-silencing efficiency of CHS-PLGA NS was higher than those of plain-PLGA NS and naked pDNA. Thus, CHS-PLGA NS containing pDNA could provide an effective pDNA delivery system in vitro, showing that such an approach could be useful in the treatment of viral diseases in vivo. PMID:21645597

Zeng, Ping; Xu, Yi; Zeng, Chunhua; Ren, Hong; Peng, Mingli

2011-05-27

320

RNA-directed transcriptional gene silencing in plants can be inherited independently of the RNA trigger and requires Met1 for maintenance  

Microsoft Academic Search

Background: The association between DNA methylation and gene silencing has long been recognized; however, signals that initiate de novo methylation are largely unknown. In plants, recognition of RNAs that are inducers of posttranscriptional gene silencing (PTGS) can result in sequence-specific DNA methylation, and the aim of this work was to investigate whether heritable epigenetic changes can occur by this mechanism

Louise Jones; Frank Ratcliff; David C Baulcombe

2001-01-01

321

Effects of STAT3 Gene Silencing and Rapamycin on Apoptosis in Hepatocarcinoma Cells  

PubMed Central

The PI3K/Akt/mTOR and JAK/STAT3 signaling pathways are important for regulating apoptosis, and are frequently activated in cancers. In this study, we targeted STAT3 and mTOR in human hepatocellular carcinoma Bel-7402 cells and examined the subsequent alterations in cellular apoptosis. The expression of STAT3 was silenced with small interfering RNA (siRNA)-expressing plasmid. The activity of mTOR was inhibited using rapamycin. Following treatment, Annexin V/propidium iodide staining followed by flow cytometry and Hoechst33258 immunofluorescence staining was used to examine cellular apoptosis. JC-1 staining was used to monitor depolarization of mitochondrial membrane (??m). Furthermore, the expression of activated caspase 3 protein was analyzed by Western blotting. Compared to non-treated or control siRNA-transfected cells, significantly higher levels of apoptosis were detected in siSTAT3-transfected or rapamycin-treated cells (P < 0.05), which was further enhanced in cells targeted for both molecules (P < 0.05). The pro-apoptotic effects were accompanied with concomitant depolarization of mitochondrial membrane and up-regulation of activated caspase 3. Combined treatments using rapamycin and STAT3 gene silencing significantly increases apoptosis in Bel-7402 cells, displaying more dramatic effect than any single treatment. This study provides evidence for targeting multiple molecules in cancer therapy.

Zhang, Yi; Zhang, Jun-Wei; Lv, Guo-Yue; Xie, Shu-Li; Wang, Guang-Yi

2012-01-01

322

Reductively-responsive siRNA-conjugated hydrogel nanoparticles for gene silencing  

PubMed Central

A critical need still remains for effective delivery of RNA interference (RNAi) therapeutics to target tissues and cells. Self-assembled lipid- and polymer-based systems have been most extensively explored for transfection with small interfering RNA (siRNA) in liver and cancer therapies. Safety and compatibility of materials implemented in delivery systems must be ensured to maximize therapeutic indices. Hydrogel nanoparticles of defined dimensions and compositions, prepared via a particle molding process that is a unique off-shoot of soft lithography known as PRINT (Particle Replication in Non-wetting Templates), were explored in these studies as delivery vectors. Initially, siRNA was encapsulated in particles through electrostatic association and physical entrapment. Dose-dependent gene silencing was elicited by PEGylated hydrogels at low siRNA doses without cytotoxicity. To prevent disassociation of cargo from particles after systemic administration or during post-fabrication processing for surface functionalization, a polymerizable siRNA pro-drug conjugate with a degradable, disulfide linkage was prepared. Triggered release of siRNA from the prodrug hydrogels was observed under a reducing environment while cargo retention and integrity were maintained under physiological conditions. Gene silencing efficiency and cytocompatibility were optimized by screening the amine content of the particles. When appropriate control siRNA cargos were loaded into hydrogels, gene knockdown was only encountered for hydrogels containing releasable, target-specific siRNAs, accompanied by minimal cell death. Further investigation into shape, size, and surface decoration of siRNA-conjugated hydrogels should enable efficacious targeted in vivo RNAi therapies.

Dunn, Stuart S.; Tian, Shaomin; Blake, Steven; Wang, Jin; Galloway, Ashley L.; Murphy, Andrew; Pohlhaus, Patrick D.; Rolland, Jason P.; Napier, Mary E.; DeSimone, Joseph M.

2012-01-01

323

Transcriptional gene silencing of HIV-1 through promoter targeted RNA is highly specific  

PubMed Central

We have previously reported induction of transcriptional gene silencing (TGS) of HIV-1 by short hairpin RNA (shRNA) expressed in MOLT-4 cells. The shRNA (termed shPromA) targets the highly conserved tandem NF?B binding sequences of the HIV-1 promoter. Recent articles have reported that TGS mediated by promoter-targeted siRNAs was exclusively the result of sequence non-specific off-target effects. Specifically, several mismatched siRNAs to the target promoter sequences were reported to also induce significant TGS, suggesting TGS was a consequence of off-target effects. Here, following extensive investigation, we report that shPromA induces sequence specific transcriptional silencing in HIV-1 infection in MOLT-4 cells, while four shRNA variants, mismatched by 2–3 nucleotides, fail to suppress viral replication. We confirm similar levels of shRNA expression from the U6 promoter and the presence of processed/cleaved siRNAs for each construct in transduced MOLT-4 cells. HIV-1 sequence specific shPromA does not suppress HIV-2, which has an alternate NF?B binding sequence. As a result of the unique sequence targeted, shPromA does not induce downregulation of other NF?B driven genes, either at the mRNA or protein level. Furthermore, we confirmed shPromA does not have sequence non-specific off-target effects through unaltered expression of CD4, CXCR4 and CCR5, which are used for viral entry. Additionally, shPromA does not alter PKR, IFN levels, and three downstream mediators of IFN? response genes. Our data clearly shows that shPromA achieved highly specific TGS of HIV-1, demonstrating that effective TGS can be induced with minimal off-target effects.

Ishida, Takaomi; Yamagishi, Makoto; Ahlenstiel, Chantelle; Swaminathan, Sanjay; Marks, Katharine; Murray, Daniel; McCartney, Erin M; Beard, Michael R; Alexander, Marina; Purcell, Damian FJ; Cooper, David A; Watanabe, Toshiki; Kelleher, Anthony D

2011-01-01

324

A common protein binds to two silencers 5' to the human beta-globin gene.  

PubMed Central

The temporal sequence of expression of human globin genes during development suggests precise regulation of these genes. Recent studies have characterized a number of DNA sequences within or flanking the human beta-globin gene which are important in its regulation and several proteins which bind to these sequences have been identified. We have found two proteins which bind 5' to the human beta-globin gene. One of these proteins, which we designate BP1, binds to two sequences, one between -550 and -527 bp relative to the cap site, the other between -302 and -294 bp. A second protein, BP2, binds to sequences between -275 and -263 bp. The binding sites for both BP1 and BP2 are in two regions which function as silencers in a transient expression assay using the human erythroleukemia cell line K562. These results and others presented here suggest that BP1 may act as a repressor protein. Negative regulation seems to be an important component of tissue and developmental specific globin gene regulation. Images

Berg, P E; Williams, D M; Qian, R L; Cohen, R B; Cao, S X; Mittelman, M; Schechter, A N

1989-01-01

325

Multiple binding of methyl-CpG and polycomb proteins in long-term gene silencing events.  

PubMed

Epigenetic regulation is involved in the maintenance of long-term silencing phenomena, such as X-inactivation and genomic imprinting in mammals. Gene repression is mediated by several mechanisms, such as histone modifications, DNA methylation, and recruitment of Polycomb proteins. To understand the mechanistic relationships between these mechanisms for stable gene silencing, we analyzed the mechanisms of X- and Y-inactivation of the PAR2 gene SYBL1, previously showed to be regulated by concerted epigenetic mechanisms. Maintenance of stable repression occurs via the recruitment of both MBDPs and PRC2 complexes to SYBL1 promoter. Their binding is equally sensitive to defective DNA methylation seen in cells derived from ICF syndrome patients. Multiple occupancy is a feature shared within long-term repressed genes, such as the X-inactivated PGK1 and the imprinted IGF2. MBD2, MBD3, and MeCP2 occupy SYBL1 promoter simultaneously, as revealed by sequential ChIP. We did not find this co-occurring binding when looked for members of PRC2 complex together with any of the methyl-binding proteins. Furthermore, in co-transfection assays, MECP2 can silence methylated SYBL1 promoter, whereas the mutated protein fails. However, RNA interference of endogenous MECP2 does not induce the expression of the inactive SYBL1 alleles, suggesting that its silencing activity can be replaced by the other methyl-binding proteins. Our data suggest that maintenance of long-term silencing involves multiple layers of epigenetic control functionally redundant. PRC2 and MBD proteins could collaborate to different phases of this process, the former possibly recruiting DNMTs to the silenced promoters, the latter dictating the lock of the transcription. PMID:17133344

Matarazzo, M R; De Bonis, M L; Strazzullo, M; Cerase, A; Ferraro, M; Vastarelli, P; Ballestar, E; Esteller, M; Kudo, S; D'Esposito, M

2007-03-01

326

Transcriptional control of genes encoding CS1 pili: negative regulation by a silencer and positive regulation by Rns.  

PubMed

The adherence of enterotoxigenic Escherichia coli (ETEC) to the human small intestine is an important early event in infection. Attachment is thought to be mediated by proteinaceous structures called pili. We have investigated the regulation of expression of the genes encoding CS1 pili found on human ETEC strains and find that there are at least three promoters, P1 and P2, upstream of the coo genes, and P3, downstream of the start of cooB translation. We identified a silencer of transcription which extends over several hundred bases overlapping the cooB open reading frame. This silencer is dependent on the promoter and/or upstream region for its negative effect. The DNA binding protein H-NS is a repressor of coo transcription that acts in the same region as the silencer, so it is possible that H-NS is involved in this silencing. Rns, a member of the AraC family, positively regulates transcription of the coo operon and relieves the silencing of CS1 expression. PMID:9294429

Murphree, D; Froehlich, B; Scott, J R

1997-09-01

327

Transcriptional control of genes encoding CS1 pili: negative regulation by a silencer and positive regulation by Rns.  

PubMed Central

The adherence of enterotoxigenic Escherichia coli (ETEC) to the human small intestine is an important early event in infection. Attachment is thought to be mediated by proteinaceous structures called pili. We have investigated the regulation of expression of the genes encoding CS1 pili found on human ETEC strains and find that there are at least three promoters, P1 and P2, upstream of the coo genes, and P3, downstream of the start of cooB translation. We identified a silencer of transcription which extends over several hundred bases overlapping the cooB open reading frame. This silencer is dependent on the promoter and/or upstream region for its negative effect. The DNA binding protein H-NS is a repressor of coo transcription that acts in the same region as the silencer, so it is possible that H-NS is involved in this silencing. Rns, a member of the AraC family, positively regulates transcription of the coo operon and relieves the silencing of CS1 expression.

Murphree, D; Froehlich, B; Scott, J R

1997-01-01

328

Rapid activation of the bivalent gene Sox21 requires displacement of multiple layers of gene-silencing machinery.  

PubMed

The rapid formation of numerous tissues during development is highly dependent on the swift activation of key developmental regulators. Recent studies indicate that many key regulatory genes are repressed in embryonic stem cells (ESCs), yet poised for rapid activation due to the presence of both activating (H3K4 trimethylation) and repressive (H3K27 trimethylation) histone modifications (bivalent genes). However, little is known about bivalent gene regulation. In this study, we investigated the regulation of the bivalent gene Sox21, which is activated rapidly when ESCs differentiate in response to increases in Sox2. Chromatin immunoprecipitation demonstrated that prior to differentiation, the Sox21 gene is bound by a complex array of repressive and activating transcriptional machinery. Upon activation, all identified repressive machinery and histone modifications associated with the gene are lost, but the activating modifications and transcriptional machinery are retained. Notably, these changes do not occur when ESCs differentiate in response to retinoic acid. Moreover, ESCs lacking a functional PRC2 complex fail to activate this gene, apparently due to its association with other repressive complexes. Together, these findings suggest that bivalent genes, such as Sox21, are silenced by a complex set of redundant repressive machinery, which exit rapidly in response to appropriate differentiation signals. PMID:20876214

Chakravarthy, Harini; Ormsbee, Briana D; Mallanna, Sunil K; Rizzino, Angie

2010-09-27

329

Silencing of the N Family of Resistance Genes in Nicotiana edwardsonii Compromises the Hypersensitive Response to Tombusviruses  

Microsoft Academic Search

The nontarget effects associated with silencing of the N gene in Nicotiana edwardsonii, an amphidiploid species de- rived from N. glutinosa and N. clevelandii, have been char- acterized in this study. The N protein confers resistance to Tobacco mosaic virus (TMV), and is representative of a family of nucleotide-binding site leucine-rich repeat pro- teins present in N. glutinosa. Previous studies

Boovaraghan Balaji; John Cawly; Carlos Angel; Zhanyuan Zhang; Karuppaiah Palanichelvam; Anthony Cole; James Schoelz

2007-01-01

330

ANALYSIS OF RNA-MEDIATED GENE SILENCING USING A NEW VECTOR (PKNOCKOUT) AND AN IN PLANTA AGROBACTERIUM TRANSIENT EXPRESSION SYSTEM  

Technology Transfer Automated Retrieval System (TEKTRAN)

A hairpin RNA (hpRNA) vector, pKNOCKOUT (pKO) has been constructed to facilitate the analysis of posttranscriptional gene silencing (PTGS) in an agrobacteria-mediated transient expression system developed for tobacco. The pKO binary vector was tested by cloning a firefly luciferase (Photinus pyrali...

331

Rapid induction of transcriptional and post-transcriptional gene silencing using a novel Cucumber mosaic virus vector  

Microsoft Academic Search

We developed a novel RNA virus vector based on the Cucumber mosaic virus (CMV), which is able to efficiently induce gene silencing in plants. We manipulated the RNA 2 of the CMV Y strain, whose genome consists of tripartite components, and introduced restriction sites for cloning a foreign sequence into the vector. To evaluate the vector (designated CMV2-A1) in terms

Shungo Otagaki; Makoto Arai; Akiko Takahashi; Kazunori Goto; Jin-Sung Hong; Chikara Masuta; Akira Kanazawa

2006-01-01

332

The effect of pds gene silencing on chloroplast pigment composition, thylakoid membrane structure and photosynthesis efficiency in tobacco plants  

Microsoft Academic Search

Nicotiana tabacum plants that are silenced in pds gene have been constructed by RNAi technology. Transgenics showed different degrees of albinism and PSII efficiency was decreased significantly compared to wild type plants. The total carotenoid contents decreased. The ratio of chlorophyll (Chl) a to b was unchanged while the content of both declined. The grana stacking of thylakoid in variegation

Min Wang; Gang Wang; Jing Ji; Jiehua Wang

2009-01-01

333

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

334

Promoter-specific transcriptional interference and c-myc gene silencing by siRNAs in human cells  

PubMed Central

Small interfering RNAs (siRNAs) directed to gene promoters can silence genes at the transcriptional level. siRNA-directed transcriptional silencing (RdTS) was first described in plants and yeasts and more recently in mammalian cells. RdTS has been associated with the induction of epigenetic changes and the formation of complexes containing RNA interference and chromatin-remodelling factors. Here, we show that a promoter-targeted siRNA inhibits transcription of the c-myc gene. Transcriptional silencing of c-myc did not involve changes of known epigenetic marks. Instead, the c-myc promoter-targeted siRNA interfered with transcription initiation blocking the assembly of the pre-initiation complex. Transcriptional interference depended on Argonaute 2 and a noncoding promoter-associated RNA initiated upstream and overlapping the transcription start site. Silencing of c-myc led to growth arrest, reduced clonogenic potential and senescence of c-myc over-expressing prostate cancer cells with minimal effect on normal cells. RNA-directed transcriptional interference may be a natural mechanism of transcriptional control and siRNAs targeting noncoding RNAs participating in this regulatory pathway could be valuable tools to control expression of deregulated genes in human diseases.

Napoli, Sara; Pastori, Chiara; Magistri, Marco; Carbone, Giuseppina M; Catapano, Carlo V

2009-01-01

335

Promoter-specific transcriptional interference and c-myc gene silencing by siRNAs in human cells.  

PubMed

Small interfering RNAs (siRNAs) directed to gene promoters can silence genes at the transcriptional level. siRNA-directed transcriptional silencing (RdTS) was first described in plants and yeasts and more recently in mammalian cells. RdTS has been associated with the induction of epigenetic changes and the formation of complexes containing RNA interference and chromatin-remodelling factors. Here, we show that a promoter-targeted siRNA inhibits transcription of the c-myc gene. Transcriptional silencing of c-myc did not involve changes of known epigenetic marks. Instead, the c-myc promoter-targeted siRNA interfered with transcription initiation blocking the assembly of the pre-initiation complex. Transcriptional interference depended on Argonaute 2 and a noncoding promoter-associated RNA initiated upstream and overlapping the transcription start site. Silencing of c-myc led to growth arrest, reduced clonogenic potential and senescence of c-myc over-expressing prostate cancer cells with minimal effect on normal cells. RNA-directed transcriptional interference may be a natural mechanism of transcriptional control and siRNAs targeting noncoding RNAs participating in this regulatory pathway could be valuable tools to control expression of deregulated genes in human diseases. PMID:19461583

Napoli, Sara; Pastori, Chiara; Magistri, Marco; Carbone, Giuseppina M; Catapano, Carlo V

2009-05-21

336

Angiotensin converting enzyme gene polymorphism: Potential silencer motif and impact on progression in IgA nephropathy  

Microsoft Academic Search

Angiotensin converting gene enzyme polymorphism: Potential silencer motif and impact on progression in IgA nephropathy. Since the renin angiotensin system (RAS) is established as an important factor in renal disease progression, we determined whether RAS alleles that have been linked to variability in outcome in several cardiovascular diseases also affect progression of IgA nephropathy. These genetic variants include: (1) angiotensin

Tracy E Hunley; Bruce A Julian; John A Phillips; Marshal L Summar; Hiroaki Yoshida; Robert G Horn; Nancy J Brown; Agnes Fogo; Iekuni Ichikawa; Valentina Kon

1996-01-01

337

Multifunctional quantum-dot-based siRNA delivery for HPV18 E6 gene silence and intracellular imaging.  

PubMed

The functional quantum dots (QDs) were specifically designed to overcome barriers in siRNA delivery such as siRNA protection, cellular penetration, endosomal release, carrier unpacking, intracellular transport and gene silencing. In this paper, two l-arginine-functional-modi?ed CdSe/ZnSe QDs were synthesized as siRNA carriers to silence HPV18 E6 gene in HeLa cells. Using such constructs, these QDs showed significantly low cellular cytotoxicity and good siRNA protection. Flow cytometric and confocal microscopic analyses confirmed that the QDs delivered siRNA into HeLa cells efficiently. Importantly, superior gene silencing efficiency was achieved as evaluated by Reverse Transcription-PCR (RT-PCR) and Western blotting and HeLa cells growth was inhibited in xCELLigence installation analysis and MTT assay when treated with QD-siRNA complexes. Interestingly, the QDs coated with ?-CD-l-Arg showed optimized property compared with those coated with l-Arg. Furthermore, these QDs complexes could also be used as nanocrystal probing agents, allowing real-time tracking and localization of QDs during delivery and transfection. The properties and capabilities of these QDs showed that amino acid-modi?ed QDs could be used as useful siRNA carriers to effectively silence a target gene as well as fluorescence probes to analyze intracellular imaging in vivo. PMID:21784514

Li, Jin-Ming; Zhao, Mei-Xia; Su, Hua; Wang, Yuan-Yuan; Tan, Cai-Ping; Ji, Liang-Nian; Mao, Zong-Wan

2011-07-23

338

Inhibition of Androgen-Independent Growth of Prostate Cancer by siRNA- Mediated Androgen Receptor Gene Silencing.  

National Technical Information Service (NTIS)

To determine if AR gene silencing in prostate cancer cells via RNA interference mechanism leads to disruption of androgen-independent progression. We generated a recombinant AAV for long-term expression of a hairpin-structured AR siRNA in vivo. Then we de...

B. Li

2008-01-01

339

Suppression of post-transcriptional gene silencing by a plant viral protein localized in the nucleus  

PubMed Central

Post-transcriptional gene silencing (PTGS) is a homology-dependent RNA degradation process that may target RNA exclusively in the cytoplasm. In plants, PTGS functions as a natural defense mechanism against viruses. We reported previously that the 2b protein encoded by cucumber mosaic cucumovirus (CMV) is a virulence determinant and a suppressor of PTGS initiation in transgenic Nicotiana benthamiana. By fusion with the green fluorescent protein, we now show that the CMV 2b protein localizes to the nuclei of tobacco suspension cells and whole plants via an arginine-rich nuclear localization signal, 22KRRRRR27. We further demonstrate that the nuclear targeting of the 2b protein is required for the efficient suppression of PTGS, indicating that PTGS may be blocked in the nucleus. In addition, our data indicate that the PTGS suppressor activity is important, but not sufficient, for virulence determination by the 2b protein.

Lucy, Andrew P.; Guo, Hui-Shan; Li, Wan-Xiang; Ding, Shou-Wei

2000-01-01

340

Morphology engineering of Penicillium chrysogenum by RNA silencing of chitin synthase gene.  

PubMed

Chitin synthases, that catalyze the formation of chitin the major component of cell walls in most filamentous fungi, play crucial roles in the growth and morphogenesis. To investigate the roles of chitin synthase in Penicillium chrysogenum, we developed an RNAi system to silence the class III chitin synthase gene chs4. After transformation, mutants had a slow growth rate and shorter but highly branched hyphae. All transformants either were unable to form conidia or could form only a few. Changes in chs4 expression could lead to a completely different morphology and eventually cause distinct penicillin yields. In particular, the yield of one transformant was 41 % higher than that of the original strain. PMID:23187754

Liu, Hui; Wang, Peng; Gong, Guohong; Wang, Li; Zhao, Genhai; Zheng, Zhiming

2012-11-28

341

Polyion complex stability and gene silencing efficiency with a siRNA-grafted polymer delivery system.  

PubMed

An siRNA-grafted polymer through disulfide linkage was prepared to improve the physicochemical properties and transfection efficacies of the polyion complexes (PICs) as a nanocarrier of siRNA. The siRNA-grafted polymer formed stable PICs due to its larger numbers and higher density of anionic charges compared with monomeric siRNA, leading to effective internalization by cultured cells. Following the endosomal escape of the PIC, the disulfide linkage of the siRNA-grafted polymer allowed efficient siRNA release from the PIC under intracellular reductive conditions. Consequently, the PIC from the siRNA-grafted polymer showed a potent gene silencing effect without cytotoxicity or immunogenicity, demonstrating a promising feature of the siRNA-grafted polymer to construct the PIC-based nanocarrier for in vivo siRNA delivery. PMID:20692701

Takemoto, Hiroyasu; Ishii, Atsushi; Miyata, Kanjiro; Nakanishi, Masataka; Oba, Makoto; Ishii, Takehiko; Yamasaki, Yuichi; Nishiyama, Nobuhiro; Kataoka, Kazunori

2010-08-07

342

Targeting the IGF-1R signaling and mechanisms for epigenetic gene silencing in human multiple myeloma  

PubMed Central

Multiple myeloma (MM) is a B cell malignancy characterized by the expansion of clonal plasmablast/plasma cells within the bone-marrow. It is well established that the bone-marrow microenvironment has a pivotal role in providing critical cytokines and cell–cell interactions to support the growth and survival of the MM tumor clone. The pathogenesis of MM is, however, only fragmentarily understood. Detailed genomic analysis reveals a heterogeneous and complex pattern of structural and numerical chromosomal aberrations. In this review we will discuss some of the recent results on the functional role and potential clinical use of the IGF-1R, one of the major mediators of growth and survival for MM. We will also describe some of our results on epigenetic gene silencing in MM, as it may indeed constitute a novel basis for the understanding of tumor initiation and maintenance in MM and thus may change the current view on treatment strategies for MM.

Nilsson, Kenneth

2012-01-01

343

A sensitive switch for visualizing natural gene silencing in single cells  

PubMed Central

RNA interference is a natural gene expression silencing system that appears throughout the tree of life. As the list of cellular processes linked to RNAi grows, so does the demand for tools to accurately measure RNAi dynamics in living cells. We engineered a synthetic RNAi sensor that converts this negative regulatory signal into a positive output in living mammalian cells thereby allowing increased sensitivity and activation. Furthermore, the circuit’s modular design allows potentially any microRNA of interest to be detected. We demonstrated that the circuit responds to an artificial microRNA and becomes activated when the RNAi target is replaced by a natural microRNA target (miR-34) in U2OS osteosarcoma cells. Our studies extend the application of rationally designed synthetic switches to RNAi, providing a sensitive way to visualize the dynamics of RNAi activity rather than just the presence of miRNA molecules.

Haynes, Karmella A.; Ceroni, Francesca; Flicker, Daniel; Younger, Andrew; Silver, Pamela A.

2012-01-01

344

Arabidopsis RPT2a, 19S Proteasome Subunit, Regulates Gene Silencing via DNA Methylation  

PubMed Central

The ubiquitin/proteasome pathway plays a crucial role in many biological processes. Here we report a novel role for the Arabidopsis 19S proteasome subunit RPT2a in regulating gene activity at the transcriptional level via DNA methylation. Knockout mutation of the RPT2a gene did not alter global protein levels; however, the transcriptional activities of reporter transgenes were severely reduced compared to those in the wild type. This transcriptional gene silencing (TGS) was observed for transgenes under control of either the constitutive CaMV 35S promoter or the cold-inducible RD29A promoter. Bisulfite sequencing analysis revealed that both the transgene and endogenous RD29A promoter regions were hypermethylated at CG and non-CG contexts in the rpt2a mutant. Moreover, the TGS of transgenes driven by the CaMV 35S promoters was released by treatment with the DNA methylation inhibitor 5-aza-2?-deoxycytidine, but not by application of the inhibitor of histone deacetylase Trichostatin A. Genetic crosses with the DNA methyltransferase met1 single or drm1drm2cmt3 triple mutants also resulted in a release of CaMV 35S transgene TGS in the rpt2a mutant background. Increased methylation was also found at transposon sequences, suggesting that the 19S proteasome containing AtRPT2a negatively regulates TGS at transgenes and at specific endogenous genes through DNA methylation.

Sako, Kaori; Maki, Yuko; Kanai, Tomoyuki; Kato, Eriko; Maekawa, Shugo; Yasuda, Shigetaka; Sato, Takeo; Watahiki, Masaaki K.; Yamaguchi, Junji

2012-01-01

345

Effect of age on the gene expression of neural-restrictive silencing factor NRSF/REST.  

PubMed

Aging affects a wide range of gene expression changes in the nervous system. Such effects could be attributed to random changes in the environment with age around each gene, but also could be caused by selective changes in a limited set of key regulatory transcription factors and/or chromatin remodeling components. To approach the question of whether neural-restrictive silencer factor NRSF, a key determinant of the neuron-specific gene expression, is involved in these changes, we examined the levels of NRSF in the rat brain and dosal root ganglia during aging by semi-quantitative reverse transcriptase-mediated polymerase chain reaction (PCR) (RT-PCR). Complementary expression profiles of transcripts of NRSF and SCG10 in the mature brain were shown by in situ hybridization. Neither the mRNA levels of NRSF nor a splicing variant NRnV were changed, at least in rats up to 26 months old. The gene expression level of SCG10, one of the NRSF targets, was also unaffected by age. The stable expression of SCG10 transcripts in aging was confirmed by in situ hybridization. The NRS-binding ability of NRSF was also unchanged significantly in the nuclear extracts of aged rat brain. These results suggest that the genetic machinery associated with the NRS-NRSF system is well maintained during aging. PMID:11804711

Mori, Nozomu; Mizuno, Takafumi; Murai, Kiyohito; Nakano, Itsuko; Yamashita, Hitoshi

346

Cysteine Dioxygenase 1 Is a Tumor Suppressor Gene Silenced by Promoter Methylation in Multiple Human Cancers  

PubMed Central

The human cysteine dioxygenase 1 (CDO1) gene is a non-heme structured, iron-containing metalloenzyme involved in the conversion of cysteine to cysteine sulfinate, and plays a key role in taurine biosynthesis. In our search for novel methylated gene promoters, we have analyzed differential RNA expression profiles of colorectal cancer (CRC) cell lines with or without treatment of 5-aza-2?-deoxycytidine. Among the genes identified, the CDO1 promoter was found to be differentially methylated in primary CRC tissues with high frequency compared to normal colon tissues. In addition, a statistically significant difference in the frequency of CDO1 promoter methylation was observed between primary normal and tumor tissues derived from breast, esophagus, lung, bladder and stomach. Downregulation of CDO1 mRNA and protein levels were observed in cancer cell lines and tumors derived from these tissue types. Expression of CDO1 was tightly controlled by promoter methylation, suggesting that promoter methylation and silencing of CDO1 may be a common event in human carcinogenesis. Moreover, forced expression of full-length CDO1 in human cancer cells markedly decreased the tumor cell growth in an in vitro cell culture and/or an in vivo mouse model, whereas knockdown of CDO1 increased cell growth in culture. Our data implicate CDO1 as a novel tumor suppressor gene and a potentially valuable molecular marker for human cancer.

Brait, Mariana; Ling, Shizhang; Nagpal, Jatin K.; Chang, Xiaofei; Park, Hannah Lui; Lee, Juna; Okamura, Jun; Yamashita, Keishi; Sidransky, David; Kim, Myoung Sook

2012-01-01

347

Comprehensive protein-based artificial microRNA screens for effective gene silencing in plants.  

PubMed

Artificial microRNA (amiRNA) approaches offer a powerful strategy for targeted gene manipulation in any plant species. However, the current unpredictability of amiRNA efficacy has limited broad application of this promising technology. To address this, we developed epitope-tagged protein-based amiRNA (ETPamir) screens, in which target mRNAs encoding epitope-tagged proteins were constitutively or inducibly coexpressed in protoplasts with amiRNA candidates targeting single or multiple genes. This design allowed parallel quantification of target proteins and mRNAs to define amiRNA efficacy and mechanism of action, circumventing unpredictable amiRNA expression/processing and antibody unavailability. Systematic evaluation of 63 amiRNAs in 79 ETPamir screens for 16 target genes revealed a simple, effective solution for selecting optimal amiRNAs from hundreds of computational predictions, reaching ?100% gene silencing in plant cells and null phenotypes in transgenic plants. Optimal amiRNAs predominantly mediated highly specific translational repression at 5' coding regions with limited mRNA decay or cleavage. Our screens were easily applied to diverse plant species, including Arabidopsis thaliana, tobacco (Nicotiana benthamiana), tomato (Solanum lycopersicum), sunflower (Helianthus annuus), Catharanthus roseus, maize (Zea mays) and rice (Oryza sativa), and effectively validated predicted natural miRNA targets. These screens could improve plant research and crop engineering by making amiRNA a more predictable and manageable genetic and functional genomic technology. PMID:23645631

Li, Jian-Feng; Chung, Hoo Sun; Niu, Yajie; Bush, Jenifer; McCormack, Matthew; Sheen, Jen

2013-05-03

348

Efficient siRNA-mediated prolonged gene silencing in human amniotic fluid stem cells.  

PubMed

Human amniotic fluid stem cells (hAFSCs) are a very promising new type of fetal stem cells with numerous applications for basic science and cell-based therapies. They harbor a high differentiation potential and a low risk for tumor development, can be grown in large quantities and do not raise the ethical concerns associated with embryonic stem cells. RNA interference (RNAi) is a powerful technology to explain specific gene functions and has important implications for the clinical usage of tissue engineering. We provide a straightforward, 72-h-long protocol for siRNA-mediated gene silencing in hAFSCs. The lipid-based forward transfection protocol described in this article is the first RNAi approach for prolonged gene knockdown in hAFSCs. This protocol allows efficient, functional and reproducible gene knockdown in human stem cells over a prolonged period of time (approximately 2 weeks). We also show the successful use of this protocol in primary nontransformed nonimmortalized fibroblasts, cervical adenocarcinoma cells, transformed embryonic kidney cells, immortalized endometrial stromal cells and acute monocytic leukemia cells, suggesting a wide spectrum of applications in various cell types. PMID:20539284

Rosner, Margit; Siegel, Nicol; Fuchs, Christiane; Slabina, Nina; Dolznig, Helmut; Hengstschläger, Markus

2010-05-20

349

F127/Calcium phosphate hybrid nanoparticles: a promising vector for improving siRNA delivery and gene silencing.  

PubMed

Calcium phosphate-based transfection method had been used to transfer DNA into living cells. However, it had so far not been studied in detail to what extend siRNA delivery system. In this study, Pluronic F127/calcium phosphate hybrid nanoparticles (F127/CaP) were prepared by a facile room temperature method and employed as carriers to deliver siRNA to silence tumor cell. The morphology of the F127/CaP hybrid nanoparticles was investigated with TEM. In order to determine the ratio of F127 to CaP in the hybrid nanoparticles, TGA (the thermogravimetric analysis) was applied. MTT assays confirmed that the F127/CaP hybrid nanoparticles were quite safe. The hybrid F127/CaP nanoparticles obtained were 120-210?nm in diameter, and they were applied as siRNA carriers for siRNA loading and in vitro transfection. The siRNA encapsulating efficiency was 91.5 wt.% with a loading content of 6.5 wt.%. Compared to traditional CaP transfection method, the siRNA-loaded F127/CaP exhibited higher gene inhibition efficiency, and this was supported by fluorescence microscopy. Quantitative analysis of GFP silencing efficiency of various siRNA formulations was measured by using FACS flow cytometry analysis. Additionally, both custom CaP and F127/CaP are biocompatible and biodegradable, thus the as-prepared F127/CaP hybrid nanoparticles are promising for siRNA delivery. PMID:23746331

Qin, Liubin; Sun, Ying; Liu, Peifeng; Wang, Qi; Han, Baosan; Duan, Yourong

2013-06-08

350

The post-transcriptional gene silencing machinery functions independently of DNA methylation to repress a LINE1-like retrotransposon in Neurospora crassa  

Microsoft Academic Search

Post-transcriptional gene silencing (PTGS) involving small interfering RNA (siRNA)-directed degradation of RNA transcripts and transcriptional silencing via DNA methylation have each been proposed as mech- anisms of genome defence against invading nucleic acids, such as transposons and viruses. Furthermore, recent data from plants indicates that many trans- posons are silenced via a combination of the two mechanisms, and siRNAs can

Tony Nolan; Laura Braccini; Gianluca Azzalin; Arianna De Toni; Giuseppe Macino; Carlo Cogoni

2005-01-01

351

Analysis of transitive RNA silencing after grafting in transgenic plants with the coat protein gene of Sweet potato feathery mottle virus  

Microsoft Academic Search

We have previously reported the graft transmission of target specificity for RNA silencing using transgenic Nicotiana benthamiana plants expressing the coat protein gene (CP, including the 3? non-translated region) of Sweet potato feathery mottle virus. Transgenic plants carrying the 5? 200 and 400 bp regions of CP were newly produced. From these plants, two silenced and two non-silenced lines were selected

A. K. M. N. Haque; Yoshikazu Tanaka; Shoji Sonoda; Masamichi Nishiguchi

2007-01-01

352

Position Dependent Silencing of Germline V? Segments on TCR? Alleles Containing Pre-Assembled V?DJ?C?1 Genes  

PubMed Central

The genomic organization of TCR? loci enables V?-to-DJ?2 rearrangements on alleles with assembled V?DJ?C?1 genes, which could have deleterious physiologic consequences. To determine whether such V? rearrangements occur and if so how they might be regulated, we analyzed mice with TCR? alleles containing pre-assembled functional V?DJ?C?1 genes. V?10 segments were transcribed, rearranged, and expressed in thymocytes when located immediately upstream of a V?1DJ?C?1 gene, but not on alleles with a V?14DJ?C?1 gene. Germline V?10 transcription was silenced in mature ?? T cells. This allele-dependent and developmental stage-specific silencing of V?10 correlated with increased CpG methylation and decreased histone acetylation over the V?10 promoter and coding region. Transcription, rearrangement, and expression of the V?4 and V?16 segments located upstream of V?10 were silenced on alleles containing either V?DJ?C?1 gene; sequences within V?4, V?16, and the V?4/V?16--V?10 intergenic region exhibited constitutive high CpG methylation and low histone acetylation. Collectively, our data indicate that the position of V? segments relative to assembled V?DJ?C?1 genes influences their rearrangement and suggest that DNA sequences between V? segments may form boundaries between active and inactive V? chromatin domains upstream of V?DJ?C? genes.

Brady, Brenna L.; Oropallo, Michael A.; Yang-Iott, Katherine S.; Serwold, Thomas; Hochedlinger, Konrad; Jaenisch, Rudolf; Weissman, Irving L.; Bassing, Craig H.

2010-01-01

353

Tsw gene-based resistance is triggered by a functional RNA silencing suppressor protein of the Tomato spotted wilt virus.  

PubMed

As a result of contradictory reports, the avirulence (Avr) determinant that triggers Tsw gene-based resistance in Capsicum annuum against the Tomato spotted wilt virus (TSWV) is still unresolved. Here, the N and NSs genes of resistance-inducing (RI) and resistance-breaking (RB) isolates were cloned and transiently expressed in resistant Capsicum plants to determine the identity of the Avr protein. It was shown that the NSs(RI) protein triggered a hypersensitive response (HR) in Tsw-containing Capsicum plants, but not in susceptible Capsicum, whereas no HR was discerned after expression of the N(RI) (/) (RB) protein, or when NSs(RB) was expressed. Although NSs(RI) was able to suppress the silencing of a functional green fluorescence protein (GFP) construct during Agrobacterium tumefaciens transient assays on Nicotiana benthamiana, NSs(RB) had lost this capacity. The observation that RB isolates suppressed local GFP silencing during an infection indicated a recovery of RNA silencing suppressor activity for the NSs protein or the presence of another RNA interference (RNAi) suppressor. The role of NSs as RNA silencing suppressor and Avr determinant is discussed in the light of a putative interplay between RNAi and the natural Tsw resistance gene. PMID:23360130

de Ronde, Dryas; Butterbach, Patrick; Lohuis, Dick; Hedil, Marcio; van Lent, Jan W M; Kormelink, Richard

2013-01-30

354

DNA Replication Factor C1 Mediates Genomic Stability and Transcriptional Gene Silencing in Arabidopsis[W][OA  

PubMed Central

Genetic screening identified a suppressor of ros1-1, a mutant of REPRESSOR OF SILENCING1 (ROS1; encoding a DNA demethylation protein). The suppressor is a mutation in the gene encoding the largest subunit of replication factor C (RFC1). This mutation of RFC1 reactivates the unlinked 35S-NPTII transgene, which is silenced in ros1 and also increases expression of the pericentromeric Athila retrotransposons named transcriptional silent information in a DNA methylation-independent manner. rfc1 is more sensitive than the wild type to the DNA-damaging agent methylmethane sulphonate and to the DNA inter- and intra- cross-linking agent cisplatin. The rfc1 mutant constitutively expresses the G2/M-specific cyclin CycB1;1 and other DNA repair-related genes. Treatment with DNA-damaging agents mimics the rfc1 mutation in releasing the silenced 35S-NPTII, suggesting that spontaneously induced genomic instability caused by the rfc1 mutation might partially contribute to the released transcriptional gene silencing (TGS). The frequency of somatic homologous recombination is significantly increased in the rfc1 mutant. Interestingly, ros1 mutants show increased telomere length, but rfc1 mutants show decreased telomere length and reduced expression of telomerase. Our results suggest that RFC1 helps mediate genomic stability and TGS in Arabidopsis thaliana.

Liu, Qian; Wang, Junguo; Miki, Daisuke; Xia, Ran; Yu, Wenxiang; He, Junna; Zheng, Zhimin; Zhu, Jian-Kang; Gong, Zhizhong

2010-01-01

355

LIM-domain proteins, LIMD1, Ajuba, and WTIP are required for microRNA-mediated gene silencing  

PubMed Central

In recent years there have been major advances with respect to the identification of the protein components and mechanisms of microRNA (miRNA) mediated silencing. However, the complete and precise repertoire of components and mechanism(s) of action remain to be fully elucidated. Herein we reveal the identification of a family of three LIM domain-containing proteins, LIMD1, Ajuba and WTIP (Ajuba LIM proteins) as novel mammalian processing body (P-body) components, which highlight a novel mechanism of miRNA-mediated gene silencing. Furthermore, we reveal that LIMD1, Ajuba, and WTIP bind to Ago1/2, RCK, Dcp2, and eIF4E in vivo, that they are required for miRNA-mediated, but not siRNA-mediated gene silencing and that all three proteins bind to the mRNA 5? m7GTP cap–protein complex. Mechanistically, we propose the Ajuba LIM proteins interact with the m7GTP cap structure via a specific interaction with eIF4E that prevents 4EBP1 and eIF4G interaction. In addition, these LIM-domain proteins facilitate miRNA-mediated gene silencing by acting as an essential molecular link between the translationally inhibited eIF4E-m7GTP-5?cap and Ago1/2 within the miRISC complex attached to the 3?-UTR of mRNA, creating an inhibitory closed-loop complex.

James, Victoria; Zhang, Yining; Foxler, Daniel E.; de Moor, Cornelia H.; Kong, Yi Wen; Webb, Thomas M.; Self, Tim J.; Feng, Yungfeng; Lagos, Dimitrios; Chu, Chia-Ying; Rana, Tariq M.; Morley, Simon J.; Longmore, Gregory D.; Bushell, Martin; Sharp, Tyson V.

2010-01-01

356

Dimethylation of histone H3 lysine 9 is a critical mark for DNA methylation and gene silencing in Arabidopsis thaliana  

Microsoft Academic Search

The Arabidopsis KRYPTONITE gene encodes a member of the Su(var)3-9 family of histone methyltransferases. Mutations of kryptonite cause a reduction of methylated histone H3 lysine 9, a loss of DNA methylation, and reduced gene silencing. Lysine residues of histones can be either monomethylated, dimethylated or trimethylated and recent evidence suggests that different methylation states are found in different chromatin domains.

James P. Jackson; Lianna Johnson; Zuzana Jasencakova; Xing Zhang; Laura PerezBurgos; Prim B. Singh; Xiaodong Cheng; Ingo Schubert; Thomas Jenuwein; Steven E. Jacobsen

2004-01-01

357

Silencing of metallothionein-I gene in mouse lymphosarcoma cells by methylation  

PubMed Central

Metallothionein-I (MT-I) gene is silenced by methylation of CpG islands in mouse lymphosarcoma P1798 cells but not in the thymus, the cell type from which the tumor was derived. Bisulfite genomic sequencing revealed that all 21 CpG dinucleotides present within ?216 bp to +1 bp with respect to transcription start site are methylated in the tumor cell line, but none is methylated in the thymus. The lymphosarcoma cells induced MT-I in response to heavy metals only after demethylation with 5-azacytidine (5-AsaC). The electrophoretic mobility shift assay using specific oligonucleotide probes showed that the key transcription factors regulating MT-I gene (e.g., MTF-1, Sp 1 and MLTF/USF) are active in P1798 cells. In vivo footprinting of the proximal promoter region showed that none of the metal regulatory elements (MREs) or MLTF/USF are occupied in response to heavy metals. Demethylation of the lymphosarcoma cells with 5-AzaC resulted in constitutive footprinting at MLTF/ARE, and zinc-inducible footprinting at MRE-c, MRE-d and MRE-e sites. Demethylation of just 10 ? 20% of the CpG islands was sufficient to render the gene inducible by cadmium or zinc. The MT-I induction persisted in the cancer cells for several generations even after withdrawal of 5-AzaC from the culture medium.

Majumder, Sarmila; Ghoshal, Kalpana; Li, Zhiling; Bo, Yuan

2008-01-01

358

Senataxin plays an essential role with DNA damage response proteins in meiotic recombination and gene silencing.  

PubMed

Senataxin, mutated in the human genetic disorder ataxia with oculomotor apraxia type 2 (AOA2), plays an important role in maintaining genome integrity by coordination of transcription, DNA replication, and the DNA damage response. We demonstrate that senataxin is essential for spermatogenesis and that it functions at two stages in meiosis during crossing-over in homologous recombination and in meiotic sex chromosome inactivation (MSCI). Disruption of the Setx gene caused persistence of DNA double-strand breaks, a defect in disassembly of Rad51 filaments, accumulation of DNA:RNA hybrids (R-loops), and ultimately a failure of crossing-over. Senataxin localised to the XY body in a Brca1-dependent manner, and in its absence there was incomplete localisation of DNA damage response proteins to the XY chromosomes and ATR was retained on the axial elements of these chromosomes, failing to diffuse out into chromatin. Furthermore persistence of RNA polymerase II activity, altered ubH2A distribution, and abnormal XY-linked gene expression in Setx?/? revealed an essential role for senataxin in MSCI. These data support key roles for senataxin in coordinating meiotic crossing-over with transcription and in gene silencing to protect the integrity of the genome. PMID:23593030

Becherel, Olivier J; Yeo, Abrey J; Stellati, Alissa; Heng, Evelyn Y H; Luff, John; Suraweera, Amila M; Woods, Rick; Fleming, Jean; Carrie, Dianne; McKinney, Kristine; Xu, Xiaoling; Deng, Chuxia; Lavin, Martin F

2013-04-11

359

Applications of RNA interference-based gene silencing in animal agriculture.  

PubMed

Classical genetic selection, recently aided by genomic selection tools, has been successful in achieving remarkable progress in livestock improvement. However, genetic selection has led to decreased genetic diversity and, in some cases, acquisition of undesirable traits. In order to meet the increased demands of our expanding population, new technologies and practices must be developed that contend with zoonotic and animal disease, environmental impacts of large farming operations and the increased food and fibre production needed to feed and clothe our society. Future increases in productivity may be dependent upon the acquisition of genetic traits not currently encoded by the genomes of animals used in standard agricultural practice, thus making classical genetic selection impossible. Genetic engineering of livestock is commonly used to produce pharmaceuticals or to impart enhanced production characteristics to animals, but has also demonstrated its usefulness in producing animals with disease resistance. However, significant challenges remain because it has been more difficult to produce animals in which specific genes have been removed. It is now possible to modify livestock genomes to block expression of endogenous and exogenous genes (such as those expressed following virus infection). In the present review, we discuss mechanisms of silencing gene expression via the biology of RNA interference (RNAi), the technology of activating the RNAi pathway and the application of this technology to enhance livestock production through increased production efficiency and prevention of disease. An increased demand for sustainable food production is at the forefront of scientific challenges and RNAi technology will undoubtedly play a key role. PMID:20003845

Long, Charles R; Tessanne, Kimberly J; Golding, Michael C

2010-01-01

360

Gene silencing in the spider mite Tetranychus urticae : dsRNA and siRNA parental silencing of the Distal-less gene  

Microsoft Academic Search

A major prerequisite to understanding the evolution of developmental programs includes an appreciation of gene function in\\u000a a comparative context. RNA interference (RNAi) represents a powerful method for reverse genetics analysis of gene function.\\u000a However, RNAi protocols exist for only a handful of arthropod species. To extend functional analysis in basal arthropods,\\u000a we developed a RNAi protocol for the two-spotted

Abderrahman Khila; Miodrag Grbi?

2007-01-01

361

Relative gene-silencing efficiencies of small interfering RNAs targeting sense and antisense transcripts from the same genetic locus  

PubMed Central

Short interfering RNAs (siRNAs) directed against different regions of genes display marked variation in their potency in mediating mRNA degradation. Various factors have been proposed to affect the efficacy of siRNA. We explored some of the factors by evaluating in cultured human cells 28 randomly selected siRNAs targeting the GPR39 and MGC29643 transcripts derived from the same genetic locus but transcribed in opposite directions. Twenty of the 24 siRNAs targeting the overlapping regions of the transcripts simultaneously reduced the levels of both transcripts. Single nucleotide changes in either of the siRNA strands significantly reduced the gene-silencing efficiency of the siRNA on targeted sense transcript without affecting the antisense transcript. Overall, we observed a greater gene-silencing efficiency on the MGC29643 transcript than on the GPR39 transcript in HeLa cells. Since MGC29643 transcript is more abundant than the GPR39 transcript [0.24 versus 0.008% relative to 100% for glyceraldehyde-3-phosphate dehydrogenase (GAPDH)], the results suggest that the abundance of the mRNA affects the efficiency of silencing. Two additional observations supported this hypothesis. First, GAPDH whose intracellular level is the highest of the three was the most efficiently silenced. Second, a reversal of gene-silencing efficiency was observed in U-138 MG cells in which the relative abundance of the GPR39 and MGC29643 transcripts is also reversed. Our study suggests that low-abundant transcripts are less susceptible to siRNA-mediated degradation than medium- and high-abundant transcripts.

Hu, Xiuyuan; Hipolito, Sharlene; Lynn, Rebecca; Abraham, Violet; Ramos, Silvester; Wong-Staal, Flossie

2004-01-01

362

Relative gene-silencing efficiencies of small interfering RNAs targeting sense and antisense transcripts from the same genetic locus.  

PubMed

Short interfering RNAs (siRNAs) directed against different regions of genes display marked variation in their potency in mediating mRNA degradation. Various factors have been proposed to affect the efficacy of siRNA. We explored some of the factors by evaluating in cultured human cells 28 randomly selected siRNAs targeting the GPR39 and MGC29643 transcripts derived from the same genetic locus but transcribed in opposite directions. Twenty of the 24 siRNAs targeting the overlapping regions of the transcripts simultaneously reduced the levels of both transcripts. Single nucleotide changes in either of the siRNA strands significantly reduced the gene-silencing efficiency of the siRNA on targeted sense transcript without affecting the antisense transcript. Overall, we observed a greater gene-silencing efficiency on the MGC29643 transcript than on the GPR39 transcript in HeLa cells. Since MGC29643 transcript is more abundant than the GPR39 transcript [0.24 versus 0.008% relative to 100% for glyceraldehyde-3-phosphate dehydrogenase (GAPDH)], the results suggest that the abundance of the mRNA affects the efficiency of silencing. Two additional observations supported this hypothesis. First, GAPDH whose intracellular level is the highest of the three was the most efficiently silenced. Second, a reversal of gene-silencing efficiency was observed in U-138 MG cells in which the relative abundance of the GPR39 and MGC29643 transcripts is also reversed. Our study suggests that low-abundant transcripts are less susceptible to siRNA-mediated degradation than medium- and high-abundant transcripts. PMID:15333693

Hu, Xiuyuan; Hipolito, Sharlene; Lynn, Rebecca; Abraham, Violet; Ramos, Silvester; Wong-Staal, Flossie

2004-08-27

363

siRNA-Aptamer Chimeras on Nanoparticles, Preserving Targeting Functionality for Effective Gene Silencing  

PubMed Central

siRNA-aptamer chimera is emerging as a highly promising approach for cell-type specific delivery of siRNA due to the outstanding targeting capability of aptamer and the compatibility of chimera with native ribonuclease (Dicer) processing. For efficient RNA interference (RNAi), however, additional challenges must be addressed, in particular how to get siRNA out of endosome after cell entry and how to preserve aptamer targeting specificity when chimeras are combined with delivery carriers. Here, we report a rationally designed nanoparticle vector that simultaneously displays large surface area for high siRNA payload, exposed aptamer for specific targeting, proton sponge effect for endosome escape, and fluorescence for imaging and quantification. A key concept of this work is to graft chimeras onto nanoparticle surface via a two-step process: first immobilizing siRNA onto nanoparticle via non-covalent interactions to facilitate intracellular unpackaging and reduce nanoparticle surface charge (avoiding non-specific electrostatic interactions between aptamers and nanoparticles), and then coupling siRNA and aptamer with retained conformation and high accessibility. Compared with conventional one-step adsorption of siRNA-aptamer chimeras onto nanoparticles with random orientations and conformations, which does not elicit much improved RNAi effect than non-targeted nanoparticle-siRNA complexes (~6-8% improvement of the total cell population), under the same RNA concentration our approach shows selective gene silencing and enables 34% more silenced cells of the total cell population over non-targeted nanoparticle-siRNA complexes. This remarkable difference in RNAi efficiency using nanoparticle-chimera complexes is directly related to cell uptake discrepancy resulted from aptamer conformation on nanoparticle surface (intact vs. random).

Bagalkot, Vaishali

2011-01-01

364

MGMT germline polymorphism is associated with somatic MGMT promoter methylation and gene silencing in colorectal cancer.  

PubMed

O-6-methylguanine-DNA methyltransferase (MGMT) repairs inappropriately methylated guanine residues in DNA. MGMT promoter methylation and gene silencing are common events in colorectal cancer, and may or may not co-exist with the CpG island methylator phenotype (CIMP). To date, no study has examined the relationship between MGMT promoter methylation and common MGMT single nucleotide polymorphisms (SNPs), which have been associated with colorectal cancer risk. Utilizing real-time polymerase chain reaction (MethyLight technology), we quantified DNA methylation in MGMT and eight other markers (a CIMP diagnostic panel including CACNA1G, CDKN2A, CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1 in 182 colorectal cancers collected from two prospective cohorts, the Nurses' Health Study and the Health Professionals Follow-up Study. We genotyped four MGMT germline SNPs in normal DNA and assessed microsatellite instability (MSI), 18q loss of heterozygosity and KRAS and BRAF status in tumors. The presence of a common MGMT promoter SNP (NM_002412.2:c.-56C>T) (rs16906252) was strongly associated with MGMT methylation (multivariate odds ratio 18.0; 95% confidence interval, 6.2-52.1, P < 0.0001). The presence of the c.-56C>T SNP was also associated with loss of MGMT expression in tumors (assessed by immunohistochemistry) (P = 0.009). This promoter SNP was not correlated with KRAS, BRAF, CIMP or MSI status. None of the other three non-promoter SNPs was significantly associated with any molecular changes tested. In conclusion, we have found a strong association between the germline polymorphism (c.-56C>T) of the MGMT promoter and promoter methylation/silencing of MGMT in colorectal cancer. Our data provide compelling evidence for common susceptibility for MGMT promoter CpG island methylation. PMID:17621591

Ogino, Shuji; Hazra, Aditi; Tranah, Gregory J; Kirkner, Gregory J; Kawasaki, Takako; Nosho, Katsuhiko; Ohnishi, Mutsuko; Suemoto, Yuko; Meyerhardt, Jeffrey A; Hunter, David J; Fuchs, Charles S

2007-07-09

365

Gene silencing following siRNA delivery to skin via coated steel microneedles: In vitro and in vivo proof-of-concept.  

PubMed

The development of siRNA-based gene silencing therapies has significant potential for effectively treating debilitating genetic, hyper-proliferative or malignant skin conditions caused by aberrant gene expression. To be efficacious and widely accepted by physicians and patients, therapeutic siRNAs must access the viable skin layers in a stable and functional form, preferably without painful administration. In this study we explore the use of minimally-invasive steel microneedle devices to effectively deliver siRNA into skin. A simple, yet precise microneedle coating method permitted reproducible loading of siRNA onto individual microneedles. Following recovery from the microneedle surface, lamin A/C siRNA retained full activity, as demonstrated by significant reduction in lamin A/C mRNA levels and reduced lamin A/C protein in HaCaT keratinocyte cells. However, lamin A/C siRNA pre-complexed with a commercial lipid-based transfection reagent (siRNA lipoplex) was less functional following microneedle coating. As Accell-modified "self-delivery" siRNA targeted against CD44 also retained functionality after microneedle coating, this form of siRNA was used in subsequent in vivo studies, where gene silencing was determined in a transgenic reporter mouse skin model. Self-delivery siRNA targeting the reporter (luciferase/GFP) gene was coated onto microneedles and delivered to mouse footpad. Quantification of reporter mRNA and intravital imaging of reporter expression in the outer skin layers confirmed functional in vivo gene silencing following microneedle delivery of siRNA. The use of coated metal microneedles represents a new, simple, minimally-invasive, patient-friendly and potentially self-administrable method for the delivery of therapeutic nucleic acids to the skin. PMID:23313112

Chong, Rosalind H E; Gonzalez-Gonzalez, Emilio; Lara, Maria F; Speaker, Tycho J; Contag, Christopher H; Kaspar, Roger L; Coulman, Sion A; Hargest, Rachel; Birchall, James C

2013-01-08

366

Posttranscriptional Gene Silencing of GBSSI in Potato: Effects of Size and Sequence of the Inverted Repeats  

Microsoft Academic Search

In the past, silencing of granule-bound starch synthase (GBSSI) in potato was achieved by antisense technology, where it was\\u000a observed that inclusion of the 3? end of the GBSSI coding region increased silencing efficiency. Since higher silencing efficiencies\\u000a were desired, GBSSI inverted repeat constructs were designed and tested in potato. First, large inverted repeats comprising\\u000a the 5? and the 3?

H. J. B. Heilersig; A. E. H. M. Loonen; Bergervoet-van Deelen van J. E. M; A. M. A. Wolters; R. G. F. Visser

2006-01-01

367

HC-Pro silencing suppressor significantly alters the gene expression profile in tobacco leaves and flowers  

Microsoft Academic Search

Background  RNA silencing is used in plants as a major defence mechanism against invasive nucleic acids, such as viruses. Accordingly,\\u000a plant viruses have evolved to produce counter defensive RNA-silencing suppressors (RSSs). These factors interfere in various\\u000a ways with the RNA silencing machinery in cells, and thereby disturb the microRNA (miRNA) mediated endogene regulation and\\u000a induce developmental and morphological changes in plants.

Arto J Soitamo; Balaji Jada; Kirsi Lehto

2011-01-01

368

Expression of geminiviral AC2 RNA silencing suppressor changes sugar and jasmonate responsive gene expression in transgenic tobacco plants  

PubMed Central

Background RNA-silencing is a conserved gene regulation and surveillance machinery, which in plants, is also used as major defence mechanism against viruses. Various virus-specific dsRNA structures are recognized by the silencing machinery leading to degradation of the viral RNAs or, as in case of begomoviruses, to methylation of their DNA genomes. Viruses produce specific RNA silencing suppressor (RSS) proteins to prevent these host defence mechanisms, and as these interfere with the silencing machinery they also disturb the endogenous silencing reactions. In this paper, we describe how expression of AC2 RSS, derived from African cassava mosaic geminivirus changes transcription profile in tobacco (Nicotiana tabacum) leaves and in flowers. Results Expression of AC2 RSS in transgenic tobacco plants induced clear phenotypic changes both in leaves and in flowers. Transcriptomes of these plants were strongly altered, with total of 1118 and 251 differentially expressed genes in leaves and flowers, respectively. The three most up-regulated transcript groups were related to stress, cell wall modifications and signalling, whereas the three most down-regulated groups were related to translation, photosynthesis and transcription. It appears that many of the gene expression alterations appeared to be related to enhanced biosynthesis of jasmonate and ethylene, and consequent enhancement of the genes and pathways that are regulated by these hormones, or to the retrograde signalling caused by the reduced photosynthetic activity and sugar metabolism. Comparison of these results to a previous transcriptional profiling of HC-Pro RSS-expressing plants revealed that some of same genes were induced by both RSSs, but their expression levels were typically higher in AC2 than in HC-Pro RSS expressing plants. All in all, a large number of transcript alterations were found to be specific to each of the RSS expressing transgenic plants. Conclusions AC2 RSS in transgenic tobacco plants interferes with the silencing machinery. It causes stress and defence reactions for instance via induction of the jasmonate and ethylene biosynthesis, and by consequent gene expression alteration regulated by these hormones. The changed sugar metabolism may cause significant down-regulation of genes encoding ribosomal proteins, thus reducing the general translation level.

2012-01-01

369

Bloom's syndrome gene-deficient phenotype in mouse primary cells induced by a modified tetracycline-controlled trans-silencer.  

PubMed

We recently reported genome-wide bi-allelic mutagenesis and phenotype-based genetic screening by tetracycline-regulated disruption of the Bloom's syndrome gene (Blm) in mouse embryonic stem (ES) cells. However, the same approach was hampered in mouse tissues owing to leaky expression of the Blm gene, which is the major obstacle in the tetracycline regulatory system. Here we describe a single-chain reverse tetracycline-controlled trans-silencer (sc rtTS) which reduces leaky expression in the tet-off system. The sc rtTS consists of two silencer moieties linked by a 36 amino acid linker. Although the silencer moiety contained a dimerization domain compatible with the tetracycline-controlled transactivator (tTA), heterodimerization with tTA was prevented because intramolecular self-assembly between linked silencer moieties was preferred. The system was applied to mouse splenic lymphocytes and elevation of sister chromatid exchange, the hallmark of Blm dysfunction, was observed in the presence of doxycycline. A cassette containing both sc rtTS and tTA was introduced into the Blm allele in ES cells and reduction of basal activity was observed upon doxycycline treatment. Our data demonstrate effectiveness of sc rtTS in the tet-off system. Application of sc rtTS in mice may allow us to implement bi-allelic mutagenesis in vivo. PMID:16387452

Hayakawa, Tomoko; Yusa, Kosuke; Kouno, Michiyoshi; Takeda, Junji; Horie, Kyoji

2006-01-04

370

Identification of a PRMT5-dependent repressor complex linked to silencing of human fetal globin gene expression  

PubMed Central

Defining the molecular mechanisms underpinning fetal (?) globin gene silencing may provide strategies for reactivation of ?-gene expression, a major therapeutic objective in patients with ?-thalassemia and sickle cell disease (SCD). We have previously demonstrated that symmetric methylation of histone H4 Arginine 3 (H4R3me2s) by the protein arginine methyltransferase PRMT5 is required for recruitment of the DNA methyltransferase DNMT3A to the ?-promoter, and subsequent DNA methylation and gene silencing. Here we show in an erythroid cell line, and in primary adult erythroid progenitors that PRMT5 induces additional repressive epigenetic marks at the ?-promoter through the assembly of a multiprotein repressor complex containing the histone modifying enzymes SUV4-20h1, casein kinase 2? (CK2?), and components of the nucleosome remodeling and histone deacetylation complex. Expression of a mutant form of PRMT5 lacking methyltransferase activity or shRNA-mediated knockdown of SUV4-20h1 resulted in loss of complex binding to the ?-promoter, reversal of both histone and DNA repressive epigenetic marks, and increased ?-gene expression. The repressive H4K20me3 mark induced by SUV4-20h1 is enriched on the ?-promoter in erythroid progenitors from adult bone marrow compared with cord blood, suggesting developmental specificity. These studies define coordinated epigenetic events linked to fetal globin gene silencing, and provide potential therapeutic targets for the treatment of ?-thalassemia and SCD.

Rank, Gerhard; Cerruti, Loretta; Simpson, Richard J.; Moritz, Robert L.

2010-01-01

371

HIGS: Host-Induced Gene Silencing in the Obligate Biotrophic Fungal Pathogen Blumeria graminis[W][OA  

PubMed Central

Powdery mildew fungi are obligate biotrophic pathogens that only grow on living hosts and cause damage in thousands of plant species. Despite their agronomical importance, little direct functional evidence for genes of pathogenicity and virulence is currently available because mutagenesis and transformation protocols are lacking. Here, we show that the accumulation in barley (Hordeum vulgare) and wheat (Triticum aestivum) of double-stranded or antisense RNA targeting fungal transcripts affects the development of the powdery mildew fungus Blumeria graminis. Proof of concept for host-induced gene silencing was obtained by silencing the effector gene Avra10, which resulted in reduced fungal development in the absence, but not in the presence, of the matching resistance gene Mla10. The fungus could be rescued from the silencing of Avra10 by the transient expression of a synthetic gene that was resistant to RNA interference (RNAi) due to silent point mutations. The results suggest traffic of RNA molecules from host plants into B. graminis and may lead to an RNAi-based crop protection strategy against fungal pathogens.

Nowara, Daniela; Gay, Alexandra; Lacomme, Christophe; Shaw, Jane; Ridout, Christopher; Douchkov, Dimitar; Hensel, Gotz; Kumlehn, Jochen; Schweizer, Patrick

2010-01-01

372

SAM Domain Polymerization Links Subnuclear Clustering of PRC1 to Gene Silencing.  

PubMed

The Polycomb-group (PcG) repressive complex-1 (PRC1) forms microscopically visible clusters in nuclei; however, the impact of this cluster formation on transcriptional regulation and the underlying mechanisms that regulate this process remain obscure. Here, we report that the sterile alpha motif (SAM) domain of a PRC1 core component Phc2 plays an essential role for PRC1 clustering through head-to-tail macromolecular polymerization, which is associated with stable target binding of PRC1/PRC2 and robust gene silencing activity. We propose a role for SAM domain polymerization in this repression by two distinct mechanisms: first, through capturing and/or retaining PRC1 at the PcG targets, and second, by strengthening the interactions between PRC1 and PRC2 to stabilize transcriptional repression. Our findings reveal a regulatory mechanism mediated by SAM domain polymerization for PcG-mediated repression of developmental loci that enables a robust yet reversible gene repression program during development. PMID:24091011

Isono, Kyoichi; Endo, Takaho A; Ku, Manching; Yamada, Daisuke; Suzuki, Rie; Sharif, Jafar; Ishikura, Tomoyuki; Toyoda, Tetsuro; Bernstein, Bradley E; Koseki, Haruhiko

2013-09-30

373

Variables and Strategies in Development of Therapeutic Post-Transcriptional Gene Silencing Agents  

PubMed Central

Post-transcriptional gene silencing (PTGS) agents such as ribozymes, RNAi and antisense have substantial potential for gene therapy of human retinal degenerations. These technologies are used to knockdown a specific target RNA and its cognate protein. The disease target mRNA may be a mutant mRNA causing an autosomal dominant retinal degeneration or a normal mRNA that is overexpressed in certain diseases. All PTGS technologies depend upon the initial critical annealing event of the PTGS ligand to the target RNA. This event requires that the PTGS agent is in a conformational state able to support hybridization and that the target have a large and accessible single-stranded platform to allow rapid annealing, although such platforms are rare. We address the biocomplexity that currently limits PTGS therapeutic development with particular emphasis on biophysical variables that influence cellular performance. We address the different strategies that can be used for development of PTGS agents intended for therapeutic translation. These issues apply generally to the development of PTGS agents for retinal, ocular, or systemic diseases. This review should assist the interested reader to rapidly appreciate critical variables in PTGS development and facilitate initial design and testing of such agents against new targets of clinical interest.

Sullivan, Jack M.; Yau, Edwin H.; Kolniak, Tiffany A.; Sheflin, Lowell G.; Taggart, R. Thomas; Abdelmaksoud, Heba E.

2011-01-01

374

The Development of an Efficient Multipurpose Bean Pod Mottle Virus Viral Vector Set for Foreign Gene Expression and RNA Silencing1[C  

PubMed Central

Plant viral vectors are valuable tools for heterologous gene expression, and because of virus-induced gene silencing (VIGS), they also have important applications as reverse genetics tools for gene function studies. Viral vectors are especially useful for plants such as soybean (Glycine max) that are recalcitrant to transformation. Previously, two generations of bean pod mottle virus (BPMV; genus Comovirus) vectors have been developed for overexpressing and silencing genes in soybean. However, the design of the previous vectors imposes constraints that limit their utility. For example, VIGS target sequences must be expressed as fusion proteins in the same reading frame as the viral polyprotein. This requirement limits the design of VIGS target sequences to open reading frames. Furthermore, expression of multiple genes or simultaneous silencing of one gene and expression of another was not possible. To overcome these and other issues, a new BPMV-based vector system was developed to facilitate a variety of applications for gene function studies in soybean as well as in common bean (Phaseolus vulgaris). These vectors are designed for simultaneous expression of multiple foreign genes, insertion of noncoding/antisense sequences, and simultaneous expression and silencing. The simultaneous expression of green fluorescent protein and silencing of phytoene desaturase shows that marker gene-assisted silencing is feasible. These results demonstrate the utility of this BPMV vector set for a wide range of applications in soybean and common bean, and they have implications for improvement of other plant virus-based vector systems.

Zhang, Chunquan; Bradshaw, Jeffrey D.; Whitham, Steven A.; Hill, John H.

2010-01-01

375

Structural features of GmIRCHS, candidate of the I gene inhibiting seed coat pigmentation in soybean: implications for inducing endogenous RNA silencing of chalcone synthase genes  

Microsoft Academic Search

Most commercial soybean varieties have yellow seeds due to loss of pigmentation in the seed coat. The I gene inhibits pigmentation over the entire seed coat, resulting in a uniform yellow color of mature harvested seeds. We previously\\u000a demonstrated that the inhibition of seed coat pigmentation by the I gene results from post-transcriptional gene silencing (PTGS) of chalcone synthase (CHS)

Atsushi Kasai; Kosuke Kasai; Setsuzo Yumoto; Mineo Senda

2007-01-01

376

SiO2 nanoparticles biocompatibility and their potential for gene delivery and silencing  

NASA Astrophysics Data System (ADS)

Despite the extensive use of silica nanoparticles (SiO2NPs) in many fields, the results about their potential toxicity are still controversial. In this work, we have performed a systematic in vitro study to assess the biological impact of SiO2NPs, by investigating 3 different sizes (25, 60 and 115 nm) and 2 surface charges (positive and negative) of the nanoparticles in 5 cell lines (3 in adherence and 2 in suspension). We analyzed the cellular uptake and distribution of the NPs along with their possible effects on cell viability, membrane integrity and generation of reactive oxygen species (ROS). Experimental results show that all the investigated SiO2NPs do not induce detectable cytotoxic effects (up to 2.5 nM concentration) in all cell lines, and that cellular uptake is mediated by an endocytic process strongly dependent on the particle size and independent of its original surface charge, due to protein corona effects. Once having assessed the biocompatibility of SiO2NPs, we have evaluated their potential in gene delivery, showing their ability to silence specific protein expression. The results of this work indicate that monodisperse and stable SiO2NPs are not toxic, revealing their promising potential in various biomedical applications.Despite the extensive use of silica nanoparticles (SiO2NPs) in many fields, the results about their potential toxicity are still controversial. In this work, we have performed a systematic in vitro study to assess the biological impact of SiO2NPs, by investigating 3 different sizes (25, 60 and 115 nm) and 2 surface charges (positive and negative) of the nanoparticles in 5 cell lines (3 in adherence and 2 in suspension). We analyzed the cellular uptake and distribution of the NPs along with their possible effects on cell viability, membrane integrity and generation of reactive oxygen species (ROS). Experimental results show that all the investigated SiO2NPs do not induce detectable cytotoxic effects (up to 2.5 nM concentration) in all cell lines, and that cellular uptake is mediated by an endocytic process strongly dependent on the particle size and independent of its original surface charge, due to protein corona effects. Once having assessed the biocompatibility of SiO2NPs, we have evaluated their potential in gene delivery, showing their ability to silence specific protein expression. The results of this work indicate that monodisperse and stable SiO2NPs are not toxic, revealing their promising potential in various biomedical applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr11269d

Malvindi, Maria Ada; Brunetti, Virgilio; Vecchio, Giuseppe; Galeone, Antonio; Cingolani, Roberto; Pompa, Pier Paolo

2012-01-01

377

Silencing of GSTP1, a Prostate Cancer Prognostic Gene, by the Estrogen Receptor-? and Endothelial Nitric Oxide Synthase Complex  

PubMed Central

We recently identified in prostate tumors (PCa) a transcriptional prognostic signature comprising a significant number of genes differentially regulated in patients with worse clinical outcome. Induction of up-regulated genes was due to chromatin remodeling by a combinatorial complex between estrogen receptor (ER)-? and endothelial nitric oxide synthase (eNOS). Here we show that this complex can also repress transcription of prognostic genes that are down-regulated in PCa, such as the glutathione transferase gene GSTP1. Silencing of GSTP1 is a common early event in prostate carcinogenesis, frequently caused by promoter hypermethylation. We validated loss of glutathione transferase (GST) P1-1 expression in vivo, in tissue microarrays from a retrospective cohort of patients, and correlated it with decreased disease-specific survival. Furthermore, we show that in PCa cultured cells ER?/eNOS causes GSTP1 repression by being recruited at estrogen responsive elements in the gene promoter with consequential remodeling of local chromatin. Treatment with ER? antagonist or its natural ligand 5?-androstane-3?,17?-diol, eNOS inhibitors or ER? small interference RNA abrogated the binding and reversed GSTP1 silencing, demonstrating the direct involvement of the complex. In vitro, GSTP1 silencing by ER?/eNOS was specific for cells from patients with worse clinical outcome where it appeared the sole mechanism regulating GSTP1 expression because no promoter hypermethylation was present. However, in vivo chromatin immunoprecipitation assays on fresh PCa tissues demonstrated that silencing by ER?/eNOS can coexist with promoter hypermethylation. Our findings reveal that the ER?/eNOS complex can exert transcriptional repression and suggest that this may represent an epigenetic event favoring inactivation of the GSTP1 locus by methylation. Moreover, abrogation of ER?/eNOS function by 3?-adiol emphasizes the significance of circulating or locally produced sex steroid hormones or their metabolites in PCa biology with relevant clinical/therapeutic implications.

Re, A.; Aiello, A.; Nanni, S.; Grasselli, A.; Benvenuti, V.; Pantisano, V.; Strigari, L.; Colussi, C.; Ciccone, S.; Mazzetti, A. P.; Pierconti, F.; Pinto, F.; Bassi, P.; Gallucci, M.; Sentinelli, S.; Trimarchi, F.; Bacchetti, S.; Pontecorvi, A.; Lo Bello, M.

2011-01-01

378

Neuron-restrictive silencer factor functions to suppress Sp1-mediated transactivation of human secretin receptor gene.  

PubMed

In the present study, a functional neuron restrictive silencer element (NRSE) was initially identified in the 5' flanking region (-83 to -67, relative to ATG) of human secretin receptor (hSCTR) gene by promoter assays coupled with scanning mutation analyses. The interaction of neuron restrictive silencer factor (NRSF) with this motif was later indicated via gel mobility shift and ChIP assays. The silencing activity of NRSF was confirmed by over-expression and also by shRNA knock-down of endogenous NRSF. These studies showed an inverse relationship between the expression levels of NRSF and hSCTR in the cells. As hSCTR gene was previously shown to be controlled by two GC-boxes which are regulated by the ratio of Sp1 to Sp3, in the present study, the functional interactions of NRSF and Sp proteins to regulate hSCTR gene was investigated. By co-immunoprecipitation assays, we found that NRSF could be co-precipitated with Sp1 as well as Sp3 in PANC-1 cells. Interestingly, co-expressions of these factors showed that NRSF could suppress Sp1-mediated, but not Sp3-mediated, transactivation of hSCTR. Taken together, we propose here that the down-regulatory effects of NRSF on hSCTR gene expression are mediated via its suppression on Sp1-mediated transactivation. PMID:23168245

Yuan, Yuan; Chow, Billy K C; Lee, Vien H Y; Lee, Leo T O

2012-11-17

379

Gene silencing H-NS paralogue StpA forms a rigid protein filament along DNA that blocks DNA accessibility.  

PubMed

Nucleoid-associated proteins are bacterial proteins that are responsible for chromosomal DNA compaction and global gene regulation. One such protein is Escherichia coli Histone-like nucleoid structuring protein (H-NS) which functions as a global gene silencer. Whereas the DNA-binding mechanism of H-NS is well-characterized, its paralogue, StpA which is also able to silence genes is less understood. Here we show that StpA is similar to H-NS in that it is able to form a rigid filament along DNA. In contrast to H-NS, the StpA filament interacts with a naked DNA segment to cause DNA bridging which results in simultaneous stiffening and bridging of DNA. DNA accessibility is effectively blocked after the formation of StpA filament on DNA, suggesting rigid filament formation is the important step in promoting gene silencing. We also show that >1?mM magnesium promotes higher order DNA condensation, suggesting StpA may also play a role in chromosomal DNA packaging. PMID:22187157

Lim, Ci Ji; Whang, Yixun R; Kenney, Linda J; Yan, Jie

2011-12-19

380

Histone H1 Is Dispensable for Methylation-Associated Gene Silencing in Ascobolus immersus and Essential for Long Life Span  

PubMed Central

A gene encoding a protein that shows sequence similarity with the histone H1 family only was cloned in Ascobolus immersus. The deduced peptide sequence presents the characteristic three-domain structure of metazoan linker histones, with a central globular region, an N-terminal tail, and a long positively charged C-terminal tail. By constructing an artificial duplication of this gene, named H1, it was possible to methylate and silence it by the MIP (methylation induced premeiotically) process. This resulted in the complete loss of the Ascobolus H1 histone. Mutant strains lacking H1 displayed normal methylation-associated gene silencing, underwent MIP, and showed the same methylation-associated chromatin modifications as did wild-type strains. However, they displayed an increased accessibility of micrococcal nuclease to chromatin, whether DNA was methylated or not, and exhibited a hypermethylation of the methylated genome compartment. These features are taken to imply that Ascobolus H1 histone is a ubiquitous component of chromatin which plays no role in methylation-associated gene silencing. Mutant strains lacking histone H1 reproduced normally through sexual crosses and displayed normal early vegetative growth. However, between 6 and 13 days after germination, they abruptly and consistently stopped growing, indicating that Ascobolus H1 histone is necessary for long life span. This constitutes the first observation of a physiologically important phenotype associated with the loss of H1.

Barra, Jose L.; Rhounim, Laila; Rossignol, Jean-Luc; Faugeron, Godeleine

2000-01-01

381

Neuron-restrictive silencer factor causes epigenetic silencing of K v4.3 gene after peripheral nerve injury  

Microsoft Academic Search

Peripheral nerve injury causes a variety of alterations in pain-related gene expression in primary afferent, which underlie the neuronal plasticity in neuropathic pain. One of the characteristic alterations is a long-lasting downregulation of voltage-gated potassium (Kv) channel, including Kv4.3, in the dorsal root ganglion (DRG). The present study showed that nerve injury reduces the messenger RNA (mRNA) expression level of

H. Uchida; K. Sasaki; L. Ma; H. Ueda

2010-01-01

382

Modulation of histone methylation and MLH1 gene silencing by hexavalent chromium  

SciTech Connect

Hexavalent chromium [Cr(VI)] is a mutagen and carcinogen, and occupational exposure can lead to lung cancers and other adverse health effects. Genetic changes resulting from DNA damage have been proposed as an important mechanism that mediates chromate's carcinogenicity. Here we show that chromate exposure of human lung A549 cells increased global levels of di- and tri-methylated histone H3 lysine 9 (H3K9) and lysine 4 (H3K4) but decreased the levels of tri-methylated histone H3 lysine 27 (H3K27) and di-methylated histone H3 arginine 2 (H3R2). Most interestingly, H3K9 dimethylation was enriched in the human MLH1 gene promoter following chromate exposure and this was correlated with decreased MLH1 mRNA expression. Chromate exposure increased the protein as well as mRNA levels of G9a a histone methyltransferase that specifically methylates H3K9. This Cr(VI)-induced increase in G9a may account for the global elevation of H3K9 dimethylation. Furthermore, supplementation with ascorbate, the primary reductant of Cr(VI) and also an essential cofactor for the histone demethylase activity, partially reversed the H3K9 dimethylation induced by chromate. Thus our studies suggest that Cr(VI) may target histone methyltransferases and demethylases, which in turn affect both global and gene promoter specific histone methylation, leading to the silencing of specific tumor suppressor genes such as MLH1.

Sun Hong; Zhou Xue; Chen Haobin; Li Qin [Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, New York 10987 (United States); Costa, Max [Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, New York 10987 (United States)], E-mail: Max.Costa@nyumc.org

2009-06-15

383

Unmasking of epigenetically silenced genes reveals DNA promoter methylation and reduced expression of PTCH in breast cancer  

Microsoft Academic Search

A pharmacological-based global screen for epigenetically silenced tumor suppressor genes was performed in MCF-7 and MDA-MB-231\\u000a breast cancer cells. Eighty-one genes in MCF-7 cells and 131 in MDA-MB-231 cells were identified, that had low basal expression\\u000a and were significantly upregulated following treatment. Eighteen genes were studied for methylation and\\/or expression in breast\\u000a cancer; PTCH, the receptor for the hedgehog (Hh)

Ido Wolf; Shikha Bose; Julian C. Desmond; Bryan T. Lin; Elizabeth A. Williamson; Beth Y. Karlan; H. Phillip Koeffler

2007-01-01

384

High-Stearic and High-Oleic Cottonseed Oils Produced by Hairpin RNA-Mediated PostTranscriptional Gene Silencing  

Microsoft Academic Search

We have genetically modified the fatty acid composition of cottonseed oil using the recently developed technique of hairpin RNA-mediated gene silencing to down-regulate the seed expression of two key fatty acid desaturase genes, ghSAD-1- encoding stearoyl-acyl-carrier protein 9-desaturase and ghFAD2-1-encoding oleoyl-phosphatidylcholine 6-desaturase. Hairpin RNA-encoding gene constructs (HP) targeted against either ghSAD-1 or ghFAD2-1 were transformed into cotton (Gossypium hirsutum cv

Qing Liu; Surinder P. Singh; Allan G. Green

2002-01-01

385

Loss of an Ig? gene enhancer in mature B cells results in rapid gene silencing and partial reversible dedifferentiation.  

PubMed

We address here whether there is cellular memory of a transcriptional enhancer once it has served its purpose to establish an active chromatin state. We have previously shown that the mouse Ig? gene's downstream enhancers, E3' and Ed, are essential but play redundant roles for establishing transcriptional activity in the locus during B cell development. To determine whether these enhancers are also necessary for the maintenance of transcriptional activity, we conditionally deleted E3' in mature B cells that possessed Ed(-/-) alleles. Upon E3' deletion, the locus became rapidly silenced and lost positive histone epigenetic marks, and the mature B cells partially dedifferentiated, induced RAG-1 and -2 along with certain other pro-B cell makers, and then redifferentiated after triggering Ig? gene rearrangements. We conclude that the Ig? gene's downstream enhancers are essential for both the establishment and maintenance of transcriptional activity and that there is no cellular memory of previous transcriptional activity in this locus. Furthermore, upon enhancer loss, the mature B cells unexpectedly underwent reversible retrograde differentiation. This result establishes that receptor editing can occur in mature B cells and raises the possibility that this may provide a tolerance mechanism for eliminating autoreactive B cells in the periphery. PMID:23508106

Zhou, Xiaorong; Xiang, Yougui; Ding, Xiaoling; Garrard, William T

2013-03-18

386

Virus-induced gene silencing of soybean rust resistance genes in Glycine tomentella  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soybean rust, incited by the fungal pathogen Phakopsora pachyrhizi, is a serious foliar soybean disease capable of causing major economic yield loss. Specific resistance to P. pachyrhizi is known and single dominant genes have been identified in soybean (Rpp1-4), but these genes have been deemed ine...

387

Transient silencing of the grapevine gene VvPGIP1 by agroinfiltration with a construct for RNA interference.  

PubMed

Grapevine is an economically important crop, and the recent completion of its genome makes it possible to study the function of specific genes through reverse genetics. However, the analysis of gene function by RNA interference (RNAi) in grapevine is difficult, because the generation of stable transgenic plants has low efficiency and is time consuming. Recently, transient expression of genes in grapevine leaves has been obtained by Agrobacterium tumefaciens infiltration (agroinfiltration). We therefore tested the possibility to silence grapevine genes by agroinfiltration of RNAi constructs. A construct to express a double strand RNA (dsRNA) corresponding to the defense-related gene VvPGIP1, encoding a polygalacturonase-inhibiting protein (PGIP), was obtained and transiently expressed by agroinfiltration in leaves of grapevine plants grown in vitro. Expression of VvPGIP1 and accumulation of PGIP activity were strongly induced by infiltration with control bacteria, but not with bacteria carrying the dsRNA construct, indicating that the gene was efficiently silenced. In contrast, expression of another defense-related gene, VST1, encoding a stilbene synthase, was unaffected by the dsRNA construct. We have therefore demonstrated the possibility of transient down-regulation of grapevine genes by agroinfiltration of constructs for the expression of dsRNA. This system can be employed to evaluate the effectiveness of constructs that can be subsequently used to generate stable RNAi transgenic plants. PMID:21932028

Bertazzon, Nadia; Raiola, Alessandro; Castiglioni, Carla; Gardiman, Massimo; Angelini, Elisa; Borgo, Michele; Ferrari, Simone

2011-09-20

388

Structure and Gene Silencing Activities of Monovalent and Pentavalent Cationic Lipid Vectors Complexed with siRNA †  

Microsoft Academic Search

Small interfering RNAs (siRNAs) of 19-25 bp mediate the cleavage of complementary mRNA, leading to post-transcriptional gene silencing. We examined cationic lipid (CL)-mediated delivery of siRNA into mammalian cells and made comparisons to CL-based DNA delivery. The effect of lipid composition and headgroup charge on the biophysical and biological properties of CL-siRNA vectors was determined. X-ray diffraction revealed that CL-siRNA

Nathan F. Bouxsein; Christopher S. McAllister; Kai K. Ewert; Charles E. Samuel; Cyrus R. Safinya

2007-01-01

389

In vivo trans-specific gene silencing in fungal cells by in planta expression of a double-stranded RNA  

Microsoft Academic Search

BACKGROUND: Self-complementary RNA transcripts form a double-stranded RNA (dsRNA) that triggers a sequence-specific mRNA degradation, in a process known as RNA interference (RNAi), leading to gene silencing. In vascular plants, RNAi molecules trafficking occur between cells and systemically throughout the plant. RNAi signals can spread systemically throughout a plant, even across graft junctions from transgenic to non-transgenic stocks. There is

Maria Laine P Tinoco; Bárbara BA Dias; Rebeca C Dall'Astta; João A Pamphile; Francisco JL Aragão

2010-01-01

390

Silencing of the human SET gene in vitro with lentivirus-mediated RNA interference.  

PubMed

In our previous study, SET was identified as one of the differentially expressed proteins that was associated with tetra-arsenic tetra-sulfide (As4S4)-induced NB4-R1 [retinoic acid-resistant acute promyelocytic leukemia (APL) cell line] apoptosis. However, the mechanism through which SET regulates pathways during this process remains unclear. The aim of this study was to construct lentivirus-mediated short hairpin RNA (shRNA) against SET and investigate the effect of SET on As4S4-induced retinoic acid-resistant APL cell apoptosis. In the present study, 4 different oligonucleotides targeting the human SET gene were synthesized and cloned into the eukaryotic expression plasmid pGCSIL-GFP. The recombinant vectors were introduced into NB4-R1 cells. The silencing efficiency was measured by real-time quantitative PCR (RT-qPCR) and western blotting. Our results showed that the 4 recombinant RNA interference (RNAi) vectors were constructed successfully. Fluorescence microscopy demonstrated that infection efficiency ranged from 70 to 90%. Infection with the 4 different RNAi vectors significantly knocked down the expression of SET by 52.8, 69.1, 48.9 and 90.3% at the mRNA level, and 92.5, 96.3, 91.7 and 98.4% at the protein level, respectively. We attempt to clarify the mechanism of As4S4 treatment on retinoic acid-resistant APL. PMID:23338687

Liu, Yanfeng; He, Pengcheng; Zhang, Mei; Shi, Lili; Zhu, Huachao; Wang, Yuan; Zhao, Jing

2013-01-15

391

Reducible hyaluronic acid-siRNA conjugate for target specific gene silencing.  

PubMed

Despite wide applications of polymer-drug conjugates, there are only a few polymer-siRNA conjugates like poly(ethylene glycol) conjugated siRNA. In this work, reducible hyaluronic acid (HA)-siRNA conjugate was successfully developed for target specific systemic delivery of siRNA to the liver. The conjugation of siRNA to HA made it possible to form a compact nanocomplex of siRNA with relatively nontoxic linear polyethyleneimine (LPEI). After characterization of HA-siRNA conjugate by size exclusion chromatography (SEC) and gel electrophoresis, its complex formation with LPEI was investigated with a particle analyzer. The HA-siRNA/LPEI complex had a mean particle size of ca. 250 nm and a negative or neutral surface charge at physiological condition. The reducible HA-siRNA/LPEI complex showed a higher in vitro gene silencing efficiency than noncleavable HA-siRNA/LPEI complex. Furthermore, after systemic delivery, apolipoprotein B (ApoB) specific HA-siApoB/LPEI complex was target specifically delivered to the liver, which resulted in statistically significant reduction of ApoB mRNA expression in a dose dependent manner. The HA-siRNA conjugate can be effectively applied as a model system to the treatment of liver diseases using various siRNAs and relatively nontoxic polycations. PMID:23731084

Park, Kitae; Yang, Jeong-A; Lee, Min-Young; Lee, Hwiwon; Hahn, Sei Kwang

2013-06-17

392

SiO2 nanoparticles biocompatibility and their potential for gene delivery and silencing.  

PubMed

Despite the extensive use of silica nanoparticles (SiO(2)NPs) in many fields, the results about their potential toxicity are still controversial. In this work, we have performed a systematic in vitro study to assess the biological impact of SiO(2)NPs, by investigating 3 different sizes (25, 60 and 115 nm) and 2 surface charges (positive and negative) of the nanoparticles in 5 cell lines (3 in adherence and 2 in suspension). We analyzed the cellular uptake and distribution of the NPs along with their possible effects on cell viability, membrane integrity and generation of reactive oxygen species (ROS). Experimental results show that all the investigated SiO(2)NPs do not induce detectable cytotoxic effects (up to 2.5 nM concentration) in all cell lines, and that cellular uptake is mediated by an endocytic process strongly dependent on the particle size and independent of its original surface charge, due to protein corona effects. Once having assessed the biocompatibility of SiO(2)NPs, we have evaluated their potential in gene delivery, showing their ability to silence specific protein expression. The results of this work indicate that monodisperse and stable SiO(2)NPs are not toxic, revealing their promising potential in various biomedical applications. PMID:22095171

Malvindi, Maria Ada; Brunetti, Virgilio; Vecchio, Giuseppe; Galeone, Antonio; Cingolani, Roberto; Pompa, Pier Paolo

2011-11-18

393

Targeted gene silencing in mouse germ cells by insertion of a homologous DNA into a piRNA generating locus  

PubMed Central

In germ cells, early embryos, and stem cells of animals, PIWI-interacting RNAs (piRNAs) have an important role in silencing retrotransposons, which are vicious genomic parasites, through transcriptional and post-transcriptional mechanisms. To examine whether the piRNA pathway can be used to silence genes of interest in germ cells, we have generated knock-in mice in which a foreign DNA fragment was inserted into a region generating pachytene piRNAs. The knock-in sequence was transcribed, and the resulting RNA was processed to yield piRNAs in postnatal testes. When reporter genes possessing a sequence complementary to portions of the knock-in sequence were introduced, they were greatly repressed after the time of pachytene piRNA generation. This repression mainly occurred at the post-transcriptional level, as degradation of the reporter RNAs was accelerated. Our results show that the piRNA pathway can be used as a tool for sequence-specific gene silencing in germ cells and support the idea that the piRNA generating regions serve as traps for retrotransposons, enabling the host cell to generate piRNAs against active retrotransposons.

Yamamoto, Yasuhiro; Watanabe, Toshiaki; Hoki, Yuko; Shirane, Kenjiro; Li, Yufeng; Ichiiyanagi, Kenji; Kuramochi-Miyagawa, Satomi; Toyoda, Atsushi; Fujiyama, Asao; Oginuma, Masayuki; Suzuki, Hitomi; Sado, Takashi; Nakano, Toru; Sasaki, Hiroyuki

2013-01-01

394

In vivo trans-specific gene silencing in fungal cells by in planta expression of a double-stranded RNA  

PubMed Central

Background Self-complementary RNA transcripts form a double-stranded RNA (dsRNA) that triggers a sequence-specific mRNA degradation, in a process known as RNA interference (RNAi), leading to gene silencing. In vascular plants, RNAi molecules trafficking occur between cells and systemically throughout the plant. RNAi signals can spread systemically throughout a plant, even across graft junctions from transgenic to non-transgenic stocks. There is also a great interest in applying RNAi to pathogenic fungi. Specific inhibition of gene expression by RNAi has been shown to be suitable for a multitude of phytopathogenic filamentous fungi. However, double-stranded (ds)RNA/small interfering (si)RNA silencing effect has not been observed in vivo. Results This study demonstrates for the first time the in vivo interference phenomenon in the pathogenic fungus Fusarium verticillioides, in which expression of an individual fungal transgene was specifically abolished by inoculating mycelial cells in transgenic tobacco plants engineered to express siRNAs from a dsRNA corresponding to the particular transgene. Conclusion The results provide a powerful tool for further studies on molecular plant-microbe and symbiotic interactions. From a biotechnological perspective, silencing of fungal genes by generating siRNAs in the host provides a novel strategy for the development of broad fungi-resistance strategies in plants and other organisms.

2010-01-01

395

Selective silencing of viral gene expression in HPV-positive human cervical carcinoma cells treated with siRNA, a primer of RNA interference  

Microsoft Academic Search

Selective silencing of mammalian gene expression has recently been achieved using short interfering RNA (siRNA). Synthetic siRNA targets homologous mRNA for degradation and the process is highly efficient. Here we demonstrate siRNA silencing of pathogenic viral gene expression. As a well characterized model we chose cervical carcinoma cells positive for human papillomavirus type 16. Over 90% of human cervical cancers

Ming Jiang; Jo Milner

2002-01-01

396

Apple latent spherical virus vectors for reliable and effective virus-induced gene silencing among a broad range of plants including tobacco, tomato, Arabidopsis thaliana, cucurbits, and legumes.  

PubMed

Apple latent spherical virus (ALSV) vectors were evaluated for virus-induced gene silencing (VIGS) of endogenous genes among a broad range of plant species. ALSV vectors carrying partial sequences of a subunit of magnesium chelatase (SU) and phytoene desaturase (PDS) genes induced highly uniform knockout phenotypes typical of SU and PDS inhibition on model plants such as tobacco and Arabidopsis thaliana, and economically important crops such as tomato, legume, and cucurbit species. The silencing phenotypes persisted throughout plant growth in these plants. In addition, ALSV vectors could be successfully used to silence a meristem gene, proliferating cell nuclear antigen and disease resistant N gene in tobacco and RCY1 gene in A. thaliana. As ALSV infects most host plants symptomlessly and effectively induces stable VIGS for long periods, the ALSV vector is a valuable tool to determine the functions of interested genes among a broad range of plant species. PMID:19243807

Igarashi, Aki; Yamagata, Kousuke; Sugai, Tomokazu; Takahashi, Yukari; Sugawara, Emiko; Tamura, Akihiro; Yaegashi, Hajime; Yamagishi, Noriko; Takahashi, Tsubasa; Isogai, Masamichi; Takahashi, Hideki; Yoshikawa, Nobuyuki

2009-02-25

397

THE USE OF NANOPARTICLE-MEDIATED TARGETED GENE SILENCING AND DRUG DELIVERY TO OVERCOME TUMOR DRUG RESISTANCE  

PubMed Central

Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) enables cancer cells to develop resistance to multiple anticancer drugs. Functional inhibitors of P-gp have shown promising efficacy in early clinical trials, but their long-term safety is yet to be established. A novel approach to overcome drug resistance is to use siRNA-mediated RNA interference to silence the expression of the efflux transporter. Because P-gp plays an important role in the physiological regulation of endogenous and xenobiotic compounds in the body, it is important to deliver P-gp targeted siRNA and anticancer drug specifically to tumor cells. Further, for optimal synergy, both the drug and siRNA may need to be temporally colocalized in the tumor cells. In the current study, we investigated the effectiveness of simultaneous and targeted delivery of anticancer drug, paclitaxel, along with P-gp targeted siRNA, using poly(D,L-lactide-co-glycolide) nanoparticles to overcome tumor drug resistance. Nanoparticles were surface functionalized with biotin for active tumor targeting. Dual agent nanoparticles encapsulating the combination of paclitaxel and P-gp targeted siRNA showed significantly higher cytotoxicity in vitro than nanoparticles loaded with paclitaxel alone. Enhanced therapeutic efficacy of dual agent nanoparticles could be correlated with effective silencing of the MDR1 gene that encodes for P-gp and with increased accumulation of paclitaxel in drug-resistant tumor cells. In vivo studies in a mouse model of drug-resistant tumor demonstrated significantly greater inhibition of tumor growth following treatment with biotin-functionalized nanoparticles encapsulating both paclitaxel and P-gp targeted siRNA at a paclitaxel dose that was ineffective in the absence of gene silencing. These results suggest that that the combination of P-gp gene silencing and cytotoxic drug delivery using targeted nanoparticles can overcome tumor drug resistance.

Patil, Yogesh; Swaminathan, Suresh; Sadhukha, Tanmoy; Ma, Linan; Panyam, Jayanth

2009-01-01

398

Cell cycle arrest drastically extends the duration of gene silencing after transient expression of short hairpin RNA.  

PubMed

Targeted gene silencing through RNA interference (RNAi) utilizes short interfering RNA (siRNA) duplexes or vectors expressing short hairpin RNA (shRNA), which is processed in the cells to siRNA. Stable RNAi in mammalian cells is usually achieved through genomic integration of shRNA expressing vectors, but transiently transfected siRNA was also reported to produce long-term silencing in primary mammalian cells. We have developed lentiviral vector LLCEP TU6X for tetracycline/doxycycline-inducible expression of cloned shRNA and a new selectable marker EGFP-Puro, comprising destabilized green fluorescent protein fused with puromycin acetyltransferase. To investigate the stability of gene silencing after transient shRNA expression, LLCEP TU6X vector carrying shRNA against firefly luciferase was transduced into luciferase-expressing human HT1080 fibrosarcoma cells. When doxycycline-induced transcription was followed by the removal of the inducer, EGFP-Puro reverted to basal level within two days, but RNAi activity required six days for full reversion in proliferating cells. When cell division was blocked with mimosine or by inducible expression of cell cycle inhibitors p27 or p21, RNAi effect was undiminished for 4-5 days and maintained at >60% level as late as 21 days after the inducer was removed. In contrast to the phenotypic stability of RNAi, the amount of siRNA in nondividing cells, measured by an RNAse protection assay, decreased approximately 7-fold just one week after transcription shutdown. These results indicate that gene silencing by transiently expressed shRNA is extremely stable in nondividing cells, and that this effect is not merely a consequence of siRNA stability. PMID:17102616

Maliyekkel, Anil; Davis, Brian M; Roninson, Igor B

2006-10-16

399

Posttranscriptional gene silencing and virus resistance in Nicotiana benthamiana expressing a Grapevine virus A minireplicon  

Microsoft Academic Search

Grapevine virus A (GVA) is closely associated with the economically important rugose-wood disease of grapevine. In an attempt to develop GVA\\u000a resistance, we made a GFP-tagged GVA-minireplicon and utilized it as a tool to consistently activate RNA silencing. Launching\\u000a the GVA-minireplicon by agroinfiltration delivery resulted in a strong RNA silencing response. In light of this finding, we\\u000a produced transgenic Nicotiana

Marina Brumin; Svetlana Stukalov; Sabrina Haviv; Mookkan Muruganantham; Yoni Moskovitz; Ozgur Batuman; Annie Fenigstein; Munir Mawassi

2009-01-01

400

Construction of efficient and effective transformation vectors for palmitoyl-acyl carrier protein thioesterase gene silencing in oil palm  

PubMed Central

Palm oil obtained from E. guineensis Jacq. Tenera is known to have about 44% of palmitic acid (C16:0). Palmitoyl-Acyl Carrier Protein Thioesterase (PATE) is one of the key enzymes involved in plastidial fatty acid biosynthesis; and it determines the level of the C16:0 assimilation in oilseeds. This enzyme's activity in oil palm is responsible for high (> 44 % in E. guineensis Jacq. Tenera and 25 % in E. oleifera) content of C16:0 in its oil. By post-transcriptional PATE gene silencing, C16:0 content can be minimized for nutritional value improvement of the palm oil. The objective of this study was the construction of novel transformation vectors for PATE gene silencing. Six different transformation vectors targeted against PATE gene were constructed using 619 bp long PATE gene (5' region) fragment (from GenBank AF507115). In one set of three transformation vectors, PATE gene fragment was fused with CaMV 35S promoter in antisense, intron-spliced inverted repeat (ISIR), and inverted repeat (IR) orientations to generate antisense mRNA and hair-pin RNAs (hpRNA). In another set of three transformation vectors with same design, CaMV 35S was replaced with Oil palm mesocarp tissue-specific promoter (MSP). The expression cassette of antisense, ISIR, and IR of PATE gene fragments were constructed in primary cloning vector, pHANNIBAL or its derivative/s. Finally, all 6 expression cassettes were sub-cloned into pCAMBIA 1301 which contains the Hygromycinr and the GUS reporter genes for transformant selection and transformation detection respectively. The results of the RE analyses of the constructs and sequence analyses of PATE and MSP shows and confirms the orientation, size and locations of all the components from constructs. We hypothesize that 4 (pISIRPATE-PC, pIRPATE-PC, pMISIRPATE-PC and pMIRPATE-PC) out of 6 transformation vectors constructed in this study will be efficient and effective in palmitoyl-ACP thioesterase gene silencing in oil palm. Abbreviations antiPATE - Antisense Palmitoyl-acyl carrier protein thioesterase, BCV - Binary cloning vector, cDNA - Complementary deoxyribonucleic acid, hpRNA - hair-pin RNA, ihpRNA - intron containing hair-pin RNA, IR - inverted repeat, ISIR - intron-spliced inverted repeat, MCS - Multiple cloning site, MSP - Oil palm mesocarp tissue-specific promoter, nt - Nucleotide/s, PATE - Palmitoyl-acyl carrier protein thioesterase, PCR - Polymerase chain reaction, PCV - Primary cloning vector, pDNA - Plasmid deoxyribonucleic acid, PTGS - Post-transcriptional gene silencing, RE - Restriction enzyme.

Bhore, Subhash Janardhan; Shah, Farida Habib

2011-01-01

401

A Truncated Form of the Human CAF-1 p150 Subunit Impairs the Maintenance of Transcriptional Gene Silencing in Mammalian Cells  

PubMed Central

Chromatin assembly factor 1 (CAF-1) is a protein complex formed of three subunits, p150, p60, and p48, conserved from the yeast Saccharomyces cerevisiae to humans, which can promote nucleosome assembly onto newly replicated DNA. In S. cerevisiae, deletion of the genes encoding any of the three CAF-1 subunits (cac? mutants), although nonlethal, results in a silencing defect of genes packaged into heterochromatin. Here we report on a mammalian cell model that we devised to monitor gene silencing and its reversal in a quantitative manner. This model relies on the use of a cell line stably transfected with a reporter gene in a silenced state. Reversal of reporter gene silencing was achieved upon treatment of the cells with 5-azacytidine, which re