Project description:The polymerase associated factor 1 complex (Paf1C) is a multifunctional epigenetic regulator of RNA polymerase II (Pol II) transcription. Paf1C controls gene expression by stimulating the placement of co-transcriptional histone modifications, influencing nucleosome occupancy in coding regions, facilitating transcription termination, and regulating nuclear export of RNAs. In this study, we investigate the extent to which these functions of Paf1C combine to influence the Saccharomyces cerevisiae transcriptome. Using conditions that enrich for unstable transcripts, we show that deletion of PAF1 affects all classes of Pol II-transcribed RNAs including multiple classes of noncoding transcripts. Gene ontology analysis revealed that mRNAs encoding genes involved in iron and phosphate homeostasis were differentially affected by deletion of PAF1. We further investigated these two groups of mRNAs with the goal of identifying overarching mechanisms of up and down-regulation in cells lacking Paf1. Our results indicate that only a subset of the observed changes result from loss of Paf1C-promoted histone modifications. We also found that transcription of the FET4 gene is differentially regulated by Paf1 and an upstream CUT. Together these data highlight the complexity of the epigenetic regulation of Pol II transcription imposed by Paf1C and identify a role for Paf1C in promoting CUT transcription.
Project description:To identify the direct targets of the Paf1/RNA polymerase II complex we compared expression profiles of isogenic wild type and paf1 and ctr9 mutant strains. We also created a Tet-regulated form of Paf1 and monitored expression patterns after shut off of Paf1. Samples were isolated at one hour intervals from 1 to 8 hours after shut off. Experiment Overall Design: Transcripts were compared on Affymetrix microarrays using standard protocols.
Project description:Eukaryotes employ a set of conserved transcription elongation factors to modulate the behavior of RNA polymerase II (RNAPII). Disruptions of one such factor, the Paf1 complex (Paf1C), generate subunit-specific phenotypes, including distinct changes to co-transcriptional histone modifications. How individual Paf1C subunits impact transcription and coupled processes remains ambiguous. By comparing conditional depletion and steady-state deletion of Paf1C subunits, we determine direct and indirect contributions of Paf1C to gene expression in Saccharomyces cerevisiae. Through nascent transcript sequencing, RNAPII profiling, and mechanistic modeling of transcription elongation dynamics, we find evidence for unique roles of Paf1C subunits in regulating RNAPII processivity, elongation rate, mRNA stability, transcript splicing, and repression of antisense transcripts. Through genetic suppression, we attribute increased antisense transcription, but not other defects, of a PAF1 mutant to loss of H3 K36 methylation. This work comprehensively analyzes both the immediate and extended roles of Paf1C subunits in transcription elongation and transcript regulation.
Project description:Eukaryotes employ a set of conserved transcription elongation factors to modulate the behavior of RNA polymerase II (RNAPII). Disruptions of one such factor, the Paf1 complex (Paf1C), generate subunit-specific phenotypes, including distinct changes to co-transcriptional histone modifications. How individual Paf1C subunits impact transcription and coupled processes remains ambiguous. By comparing conditional depletion and steady-state deletion of Paf1C subunits, we determine direct and indirect contributions of Paf1C to gene expression in Saccharomyces cerevisiae. Through nascent transcript sequencing, RNAPII profiling, and mechanistic modeling of transcription elongation dynamics, we find evidence for unique roles of Paf1C subunits in regulating RNAPII processivity, elongation rate, mRNA stability, transcript splicing, and repression of antisense transcripts. Through genetic suppression, we attribute increased antisense transcription, but not other defects, of a PAF1 mutant to loss of H3 K36 methylation. This work comprehensively analyzes both the immediate and extended roles of Paf1C subunits in transcription elongation and transcript regulation.
Project description:Eukaryotes employ a set of conserved transcription elongation factors to modulate the behavior of RNA polymerase II (RNAPII). Disruptions of one such factor, the Paf1 complex (Paf1C), generate subunit-specific phenotypes, including distinct changes to co-transcriptional histone modifications. How individual Paf1C subunits impact transcription and coupled processes remains ambiguous. By comparing conditional depletion and steady-state deletion of Paf1C subunits, we determine direct and indirect contributions of Paf1C to gene expression in Saccharomyces cerevisiae. Through nascent transcript sequencing, RNAPII profiling, and mechanistic modeling of transcription elongation dynamics, we find evidence for unique roles of Paf1C subunits in regulating RNAPII processivity, elongation rate, mRNA stability, transcript splicing, and repression of antisense transcripts. Through genetic suppression, we attribute increased antisense transcription, but not other defects, of a PAF1 mutant to loss of H3 K36 methylation. This work comprehensively analyzes both the immediate and extended roles of Paf1C subunits in transcription elongation and transcript regulation.
Project description:The Polymerase Associated Factor 1 complex (Paf1C) is a multifunctional regulator of eukaryotic gene expression important for the coordination of transcription with chromatin modification and post-transcriptional processes. In this study, we investigated the extent to which the functions of Paf1C combine to regulate the Saccharomyces cerevisiae transcriptome. While previous studies focused on the roles of Paf1C in controlling mRNA levels, here, we took advantage of a genetic background that enriches for unstable transcripts, and demonstrate that deletion of PAF1 affects all classes of Pol II transcripts including multiple classes of noncoding RNAs (ncRNAs). By conducting a de novo differential expression analysis independent of gene annotations, we found that Paf1 positively and negatively regulates antisense transcription at multiple loci. Comparisons with nascent transcript data revealed that many, but not all, changes in RNA levels detected by our analysis are due to changes in transcription instead of post-transcriptional events. To investigate the mechanisms by which Paf1 regulates protein-coding genes, we focused on genes involved in iron and phosphate homeostasis, which were differentially affected by PAF1 deletion. Our results indicate that Paf1 stimulates phosphate gene expression through a mechanism that is independent of any individual Paf1C-dependent histone modification. In contrast, the inhibition of iron gene expression by Paf1 correlates with a defect in H3 K36 trimethylation. Finally, we showed that one iron regulon gene, FET4, is coordinately controlled by Paf1 and transcription of upstream noncoding DNA. Together, these data identify roles for Paf1C in controlling both coding and noncoding regions of the yeast genome.
Project description:Phf5a regulates transcription elongation in mouse embryonic stem cells (ESCs), through regulation of the Paf1 complex. In this study we assayed for genome-wide localization of Paf1, Leo1 and Cdc73 subunits of the Paf1 complex in mouse ESCs under conditions of shControl and shPhf5a knockdown. These results revealed that downregualtion of Phf5a results in the significant decrease of Paf1 complex binding to its targets in ESCs.
Project description:In this study, we found that the ARF tumor suppressor directly binds the PAF1 subunit to block the assembly of PAF1 complex (PAF1c) and its interaction with RNAPII, thereby dampening PAF1c-dependent transcription in vitro and in cells. To investigate whether ARF regulates RNAPII and PAF1c occupancy at putative target genes identified through RNA-seq, we performed ChIP-seq (RNAPII, PAF1, and CTR9) in ARF (shARF) vs. control (shNT) knockdown MEFs. Our data show that loss of ARF increases RNAPII, PAF1, and CTR9 occupancy on upregulated genes, consistent with ARF-mediated gene-specific repression. Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for RNA polymerase subunit RPB3 and PAF1 complex subunits PAF1 and CTR9 in mouse embryonic fibroblasts.
Project description:Small RNA molecules are well known for silencing gene expression post-transcriptionally, but they are also implicated in epigenetic regulation across kingdoms. However, the mechanisms of epigenetic gene silencing by small RNAs are mostly unknown. In addition, stably silencing genes de novo using synthetic small RNAs to trigger locus-independent heterochromatin formation is impossible. Using fission yeast, we show that RNA-directed heterochromatin formation is negatively controlled by the highly conserved RNA polymerase-associated factor 1 (Paf1) complex. Temporary expression of a synthetic hairpin RNA in Paf1 mutants triggers stable heterochromatin formation at homologous loci, effectively silencing genes in trans. This repressed state is propagated over many generations by continual production of secondary siRNAs, independently of the synthetic hairpin RNA. Our work uncovers a novel mechanism for small RNA-mediated epigenome regulation and highlights fundamental roles for the Paf1 complex and the RNA interference machinery in building epigenetic memory.
Project description:Small RNA molecules are well known for silencing gene expression post-transcriptionally, but they are also implicated in epigenetic regulation across kingdoms. However, the mechanisms of epigenetic gene silencing by small RNAs are mostly unknown. In addition, stably silencing genes de novo using synthetic small RNAs to trigger locus-independent heterochromatin formation is impossible. Using fission yeast, we show that RNA-directed heterochromatin formation is negatively controlled by the highly conserved RNA polymerase-associated factor 1 (Paf1) complex. Temporary expression of a synthetic hairpin RNA in Paf1 mutants triggers stable heterochromatin formation at homologous loci, effectively silencing genes in trans. This repressed state is propagated over many generations by continual production of secondary siRNAs, independently of the synthetic hairpin RNA. Our work uncovers a novel mechanism for small RNA-mediated epigenome regulation and highlights fundamental roles for the Paf1 complex and the RNA interference machinery in building epigenetic memory.