Project description:In cells lacking the histone methyltransferase Set2, initiation of RNA polymerase II transcription occurs inappropriately within the protein-coding regions of genes, rather than being restricted to the proximal promoter. Here, we mapped the transcripts produced in an S. cerevisiae strain lacking Set2, and applied rigorous statistical methods to identify sites of cryptic transcription at high resolution.
Project description:RNA Polymerase II (Pol II) carries out transcription of both protein-coding and non-coding genes. Whereas Pol II initiation at protein-coding genes has been studied in detail, Pol II initiation at non-coding genes such as small nuclear RNA (snRNA) genes is not understood at the structural level. Here we study Pol II initiation at snRNA gene promoters and show that the snRNA-activating protein complex (SNAPc) enables DNA opening and transcription initiation independent of TFIIE and TFIIH in vitro. We then resolve cryo-EM structures of the SNAPc-containing Pol II preinitiation complex (PIC) assembled on U1 and U5 snRNA promoters. The core of SNAPc binds two turns of DNA and recognizes the snRNA promoter-specific proximal sequence element (PSE) located upstream of the TATA box-binding protein TBP. Two extensions of SNAPc called wing-1 and wing-2 bind TFIIA and TFIIB, respectively, explaining how SNAPc directs Pol II to snRNA promoters. Comparison of structures of closed and open promoter complexes elucidates TFIIH-independent DNA opening. These results provide the structural basis of Pol II initiation at non-coding RNA gene promoters.
Project description:In cells lacking the histone methyltransferase Set2, initiation of RNA polymerase II transcription occurs inappropriately within the protein-coding regions of genes, rather than being restricted to the proximal promoter. Here, we mapped the transcripts produced in an S. cerevisiae strain lacking Set2, and applied rigorous statistical methods to identify sites of cryptic transcription at high resolution. Wild type (BY4741) and set2â (BY4741) strains were grown at 30°C in YPD (1% yeast extract, 2% peptone, 2% dextrose) to an OD600 of 0.6-0.8. For each of the three replicates, Total RNA was extracted by acid-phenol method (Xiao et al. 2003). Double-stranded cDNA was prepared using an Invitrogen SuperScript⢠(Cat No. 11917-010) primed with Oligo(dt) and random hexamers. For each replicate, the wt and set2â cDNA were independetly fluorescently labeled and comparatively hybridized to high-resolution 385K Saccharomyces cerevisiae CGH arrays (2005-08-16_SCER_WG_CGH) with Tm-normalized probes. In one of the replicates, assignment of the fluorescent label was reversed.
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:In Saccharomyces cerevisiae, Sen1 is a 252-kDa, nuclear superfamily-1 RNA/DNA helicase that encoded by an essential gene SEN1 (Senataxin). It is an important component of the Nrd1p-Nab3p-Sen1p (NRD1) complex that regulates the transcriptional termination of most non-coding and some coding transcripts at RNA polymerase pause sites. Sen1 specifically interacts with Rnt1p (RNase III), an endoribonuclease, and with Rpb1p (Rpo21p), a subunit of RNA polymerase II, through its N-terminal domain (NTD), which is a critical element of the RNA-processing machinery. Moreover, mutations in the N-terminal tail of SETX, a human ortholog of yeast Senataxin (Sen1) reported in neurological disorders. In one of the earlier studies, we have reported that the loss of dispensable NTD in yeast Sen1 resulted in flocculation and slow growing phenotypes along with defective DNA damage repair mechanisms. So, we attempted to explore the molecular basis of functional impairment associated with the loss of Sen1 N-terminal domain through global oligonucleotide microarray analysis. Also, we investigated for functionally enriched pathways based on the altered basal level gene expression profiles upon NTD loss of Sen1. The microarray data were validated by quantitative real-time PCR wherever necessary.
Project description:CDK9 is a critical kinase required for the productive transcription of protein-coding genes by RNA polymerase II (pol II) in higher eukaryotes. Phosphorylation of targets including the elongation factor SPT5 and the carboxyl-terminal domain (CTD) of RNA pol II allow the polymerase to pass an early elongation checkpoint (EEC), which is encountered soon after initiation. In addition to halting RNA polymerase II at the EEC, CDK9 inhibition also causes premature termination of transcription across the last exon, loss of polyadenylation factors from chromatin, and loss of polyadenylation of nascent transcripts. Inhibition of the phosphatase PP2A abrogates the premature termination and loss of polyadenylation caused by CDK9 inhibition, suggesting that CDK9 and PP2A, working together, regulate the coupling of elongation and transcription termination to RNA maturation. Our phosphoproteomic analyses, using either DRB or an analog-sensitive CDK9 cell line confirm the splicing factor SF3B1 as an additional key target of this kinase. CDK9 inhibition causes loss of interaction of splicing and export factors with SF3B1, suggesting that CDK9 also helps to co-ordinates coupling of splicing and export to transcription.