Project description:Promoter-proximal pausing of RNA polymerase II (Pol II) is a widespread in higher eukaryotes. Previous studies have shown that GAF is enriched at paused genes, but the role of GAF in pausing has not been well characterized on a genome-wide level. To investigate the role of GAF in pausing, we RNAi-depleted GAF from Drosophila S2 cells, and examined the effects on promoter-proximal polymerase. We confirmed the importance of GAF for pausing on the classic pause model gene Hsp70. To determine the dependence of pausing on GAF genome-wide, we assayed the levels of transcriptionally-engaged polymerase genome-wide using GRO-seq in control and GAF-RNAi cells. We found that promoter-proximal polymerase was significantly reduced on a subset of paused genes with GAF-bound promoters. There is a dramatic change in nucleosome distribution at genes with reduction in pausing upon GAF depletion and intergenic GAF binding sites in GAF knock-down, suggesting that GAF allows the establishment of pausing at these genes by directing nucleosome displacement off of the promoter. In addition, the insulator factor BEAF, BEAF-interacting protein Chriz, and transcription M1BP enrichment on unaffected genes suggests that redundant transcription factors or insulators protect other GAF-bound paused genes from GAF knock-down effects. Three biological replicates of MNase digested chromatin from LacZ-RNAi and GAGA factor-RNAi cells.
Project description:Metazoan transcription is controlled through either coordinated recruitment of transcription machinery to the gene promoter, or subsequently, through regulated pausing of RNA polymerase II (Pol II) in early elongation. We report that a key difference between genes that use these distinct regulatory strategies lies in the chromatin architecture specified by their DNA sequences. Pol II pausing is prominent at highly-regulated genes whose sequences inherently disfavor nucleosome formation within the gene, but favor nucleosomal occlusion of the promoter. Pausing of polymerase maintains these genes in an active state by inhibiting the formation of repressive promoter chromatin. In contrast, promoters of housekeeping genes that lack paused Pol II are deprived of nucleosomes regardless of polymerase binding, but show higher nucleosome occupancy downstream. Our results suggest that the âdefaultâ chromatin state of a gene instructs its regulation, and that highly-regulated promoters have evolved to encourage competition between nucleosomes and paused Pol II for promoter occupancy. All experiments were done using two channels per chip, comparing DNA immunoprecipitated by the indicated antibody to matching input chromatin used for affinity purification. Where appropriate, replicate data sets were averaged.
Project description:Metazoan transcription is controlled through either coordinated recruitment of transcription machinery to the gene promoter, or subsequently, through regulated pausing of RNA polymerase II (Pol II) in early elongation. We report that a key difference between genes that use these distinct regulatory strategies lies in the chromatin architecture specified by their DNA sequences. Pol II pausing is prominent at highly-regulated genes whose sequences inherently disfavor nucleosome formation within the gene, but favor nucleosomal occlusion of the promoter. Pausing of polymerase maintains these genes in an active state by inhibiting the formation of repressive promoter chromatin. In contrast, promoters of housekeeping genes that lack paused Pol II are deprived of nucleosomes regardless of polymerase binding, but show higher nucleosome occupancy downstream. Our results suggest that the “default” chromatin state of a gene instructs its regulation, and that highly-regulated promoters have evolved to encourage competition between nucleosomes and paused Pol II for promoter occupancy.
Project description:Metazoan transcription is controlled through either coordinated recruitment of transcription machinery to the gene promoter, or subsequently, through regulated pausing of RNA polymerase II (Pol II) in early elongation. We report that a key difference between genes that use these distinct regulatory strategies lies in the chromatin architecture specified by their DNA sequences. Pol II pausing is prominent at highly-regulated genes whose sequences inherently disfavor nucleosome formation within the gene, but favor nucleosomal occlusion of the promoter. Pausing of polymerase maintains these genes in an active state by inhibiting the formation of repressive promoter chromatin. In contrast, promoters of housekeeping genes that lack paused Pol II are deprived of nucleosomes regardless of polymerase binding, but show higher nucleosome occupancy downstream. Our results suggest that the “default” chromatin state of a gene instructs its regulation, and that highly-regulated promoters have evolved to encourage competition between nucleosomes and paused Pol II for promoter occupancy.
Project description:Metazoan transcription is controlled through either coordinated recruitment of transcription machinery to the gene promoter, or subsequently, through regulated pausing of RNA polymerase II (Pol II) in early elongation. We report that a key difference between genes that use these distinct regulatory strategies lies in the chromatin architecture specified by their DNA sequences. Pol II pausing is prominent at highly-regulated genes whose sequences inherently disfavor nucleosome formation within the gene, but favor nucleosomal occlusion of the promoter. Pausing of polymerase maintains these genes in an active state by inhibiting the formation of repressive promoter chromatin. In contrast, promoters of housekeeping genes that lack paused Pol II are deprived of nucleosomes regardless of polymerase binding, but show higher nucleosome occupancy downstream. Our results suggest that the "default" chromatin state of a gene instructs its regulation, and that highly-regulated promoters have evolved to encourage competition between nucleosomes and paused Pol II for promoter occupancy.