Project description:The goal of this study was to determine the effect of transcription factor deletions on the expression of subtelomeric genes in the presence of environmental stimuli. This study is a component of a larger study, which identified that environment-responsive transcription factors bind proto-silencer elements and regulate subtelomeric silencing. Subtelomeric chromatin is subject to evolutionarily conserved complex epigenetic regulation and is implicated in numerous aspects of cellular function including formation of heterochromatin, regulation of different stress response pathways, and control of lifespan. Subtelomeric DNA is characterized by the presence of specific repeated segments that serve to propagate silencing activities or to protect chromosomal regions from spreading epigenetic control. Here, using condition-specific genome wide chromatin immunoprecipitation and expression data, we show that multiple environment-responsive yeast transcription factors act as silencing factors when conditionally associated with subtelomeric proto-silencing regions called X elements. In this context, some factors control the propagation of silencing toward centromeres in response to stimuli affecting stress responses and metabolism, whereas others influence boundaries of silencing, regulating telomere-proximal genes in Y’ elements. These data suggest a fundamental mechanism to coordinate telomere biology related to aging and adaptation with cellular environment and the activities of other cellular processes. Each experiment was performed with two biological and two technical replicates of each condition resulting in a total of four replicates. Each experiment includes two replicates in each labeling orientation (two replicates of Cy3/Cy5 and two replicates of Cy5/Cy3 (test sample/reference sample)). There are two replicates per array.
Project description:The goal of this study was to determine the effect of transcription factor deletions on the expression of subtelomeric genes in the presence of environmental stimuli. This study is a component of a larger study, which identified that environment-responsive transcription factors bind proto-silencer elements and regulate subtelomeric silencing. Subtelomeric chromatin is subject to evolutionarily conserved complex epigenetic regulation and is implicated in numerous aspects of cellular function including formation of heterochromatin, regulation of different stress response pathways, and control of lifespan. Subtelomeric DNA is characterized by the presence of specific repeated segments that serve to propagate silencing activities or to protect chromosomal regions from spreading epigenetic control. Here, using condition-specific genome wide chromatin immunoprecipitation and expression data, we show that multiple environment-responsive yeast transcription factors act as silencing factors when conditionally associated with subtelomeric proto-silencing regions called X elements. In this context, some factors control the propagation of silencing toward centromeres in response to stimuli affecting stress responses and metabolism, whereas others influence boundaries of silencing, regulating telomere-proximal genes in Y’ elements. These data suggest a fundamental mechanism to coordinate telomere biology related to aging and adaptation with cellular environment and the activities of other cellular processes.
Project description:Subtelomeric chromatin is subject to evolutionarily conserved complex epigenetic regulation and is implicated in numerous aspects of cellular function including formation of heterochromatin, regulation of different stress response pathways, and control of lifespan. Subtelomeric DNA is characterized by the presence of specific repeated segments that serve to propagate silencing activities or to protect chromosomal regions from spreading epigenetic control. Using condition-specific genome wide chromatin immunoprecipitation and expression data, we show that several yeast transcription factors regulate subtelomeric silencing in response to various environmental stimuli through conditional association with proto-silencing regions called X elements. In this context, some factors control the propagation of silencing toward centromeres in response to stimuli affecting stress responses and metabolism, whereas others appear to influence boundaries of silencing, regulating telomere-proximal genes in Y’ elements. The factors implicated here have previously been shown to control adjacent genes at intrachromosomal positions, suggesting dual functionality of the factors and a possible mechanism of coordinating intrachromosomal gene expression with subtelomeric silencing. These data suggest a fundamental mechanism to coordinate telomere biology related to aging and adaptation with cellular environment and the activities of other cellular processes. These are Chip-CHIP data for myc tagged Oaf1p transcription factor from S. cerevisiae grown in the presence or absence of the fatty acid oleate.
Project description:Subtelomeric chromatin is subject to evolutionarily conserved complex epigenetic regulation and is implicated in numerous aspects of cellular function including formation of heterochromatin, regulation of different stress response pathways, and control of lifespan. Subtelomeric DNA is characterized by the presence of specific repeated segments that serve to propagate silencing activities or to protect chromosomal regions from spreading epigenetic control. Using condition-specific genome wide chromatin immunoprecipitation and expression data, we show that several yeast transcription factors regulate subtelomeric silencing in response to various environmental stimuli through conditional association with proto-silencing regions called X elements. In this context, some factors control the propagation of silencing toward centromeres in response to stimuli affecting stress responses and metabolism, whereas others appear to influence boundaries of silencing, regulating telomere-proximal genes in Y’ elements. The factors implicated here have previously been shown to control adjacent genes at intrachromosomal positions, suggesting dual functionality of the factors and a possible mechanism of coordinating intrachromosomal gene expression with subtelomeric silencing. These data suggest a fundamental mechanism to coordinate telomere biology related to aging and adaptation with cellular environment and the activities of other cellular processes. These are Chip-CHIP data for myc tagged Oaf1p transcription factor from S. cerevisiae grown in the presence or absence of the fatty acid oleate. ChIP-CHIP analysis was performed to determine the genomic distribution of Oaf1p transcription factor in the BY4742 yeast strain after growth in 0.1% glucose, or in the presence of the fatty acid oleate. Three biological replicates for each growth condition (in the presence of low glucose or 5 h after a shift to medium containing oleate as a carbon source). ChIP samples were amplified by PCR, labelled and hybridized to 50-mer tiling arrays covering both strands of the entire yeast genome at a 64 bp resolution.
Project description:Budding yeast telomeres and cryptic mating-type loci are anchored at the nuclear envelope, forming foci that sequester Silent information regulators (SIR factors), much as heterochromatic chromocenters in higher eukaryotes sequester HP1. Here we examine the impact of such subcompartments for regulating transcription genome-wide. We show that the efficiency of subtelomeric reporter gene repression depends not only on the strength of SIR factor recruitment by cis-acting elements, but also on the accumulation of SIRs in perinuclear foci, which result from the clustering of telomeres. To monitor the effects of disrupting this subnuclear compartment, we performed microarray analyses under conditions that eliminate telomere anchoring, while preserving SIR complex integrity. We found 60 genes reproducibly misregulated. Among those with increased expression, 22% were within 20kb of a telomere, confirming that NE anchoring helps repress natural subtelomeric genes. In contrast, loci that were down-regulated were distributed over all chromosomes. Half of this ectopic repression was SIR-complex dependent. We conclude that released SIR factors can promiscuously repress transcription at nontelomeric genes despite the presence of "anti-silencing" mechanisms. Bioinformatic analysis revealed that promoters bearing the PAC (RNA Polymerase A and C promoters) or Abf1 binding consenses are consistently down-regulated by mislocalization of SIR factors. Thus, the normal telomeric sequestration of SIRs not only favors subtelomeric repression, but prevents promiscuous effects at a distinct subset of promoters. This demonstrates that patterns of gene expression can be regulated by changing the spatial distribution of repetitive DNA sequences that bind repressive factors.
Project description:Telomere chromatin structure is pivotal for maintaining genome stability by regulating the binding of telomere-associated proteins and inhibition of a DNA damage response. In yeast, the silent information regulator (Sir) proteins bind to terminal telomeric repeats and to subtelomeric X-elements resulting in histone deacetylation and transcriptional silencing. Herein, we show that sir2 mutant strains display a very specific loss of a nucleosome residing in the X-element. Most yeast telomeres contain an X-element and the nucleosome occupancy defect in sir2 mutants is remarkably consistent between different telomeres.
Project description:Both upregulation and downregulation by cis-regulatory elements help establish precise gene expression. Our understanding of how elements repress transcriptional activity is far more limited than activating elements. To address this gap, we characterized RE1, a group of transcriptional silencers bound by REST, on a genome-wide scale using an optimized massively parallel reporter assay (MPRAduo). MPRAduo empirically defined a minimal binding strength of REST required by silencer (REST m-value), above which multiple cofactors colocalize and act to directly silence transcription. We identified 1,500 human variants that alter RE1 silencing and found their effect sizes are predictable when they overlap with REST binding sites above the m-value. In addition, we demonstrate that non-canonical REST binding motifs exhibit silencer function only if they precisely align two half sites with specific spacer length. Our results show mechanistic insights into RE1 silencer which allows us to predict its activity and effect of variants on RE1, providing a paradigm for performing genome-wide functional characterization transcription factors binding sites.
Project description:Both upregulation and downregulation by cis-regulatory elements help establish precise gene expression. Our understanding of how elements repress transcriptional activity is far more limited than activating elements. To address this gap, we characterized RE1, a group of transcriptional silencers bound by REST, on a genome-wide scale using an optimized massively parallel reporter assay (MPRAduo). MPRAduo empirically defined a minimal binding strength of REST required by silencer (REST m-value), above which multiple cofactors colocalize and act to directly silence transcription. We identified 1,500 human variants that alter RE1 silencing and found their effect sizes are predictable when they overlap with REST binding sites above the m-value. In addition, we demonstrate that non-canonical REST binding motifs exhibit silencer function only if they precisely align two half sites with specific spacer length. Our results show mechanistic insights into RE1 silencer which allows us to predict its activity and effect of variants on RE1, providing a paradigm for performing genome-wide functional characterization transcription factors binding sites.
Project description:The telomeric repeat sequences (TGTGG) are the same at all chromosome ends, but the number and position of subtelomeric X and Y repeat elements vary. Using chromatin immunoprecipitation and genome-wide analyses, we here demonstrate that the subtelomeric X and Y elements have distinct structural and functional properties. Y elements are transcriptionally active and highly enriched in histones, whereas X elements are repressed and completely devoid of nucleosomes. In contrast to X elements, the Y elements lack the classical hallmarks of heterochromatin, e.g. high Sir3 and Rap1 occupancy as well as low levels of histone 4 lysine 16 acetylation, Our analyses refute the idea that subtelomeric silencing is a general phenomenon and suggest that the presence of X and Y elements govern the chromatin structure and transcription activtiy at individual chromosome ends. Keywords: nucleosome position and Histone 4 lys 16 acetylation Chip on CHIP