Project description:Aim and Methods: To understand the precise role of Spt4 in budding yeast, various high throughput sequencing techniques were used. Nucleosome positions were studied using MNase-seq in WT and spt4∆ cells. The position of RNAPII was examined using NET-seq in spt4∆ cells or cells in which Spt4 has been anchored away to the cytoplasm (Spt4 AA). RNAPII was also mapped in cells in which Spt5 has been anchored away to the cytoplasm (Spt5 AA). Steady-state transcript levels were assessed using RNA-seq in samples coupled with NET-seq. The position of the Spt4 on RNAPII was mapped at single nucleotide resolution using TEF-seq. With the same technique, the position of Spt5 on RNAPII was investigated in wild type (WT) and spt4 knock-out (spt4∆) cells. The position and levels of the pre-initiation complex were assessed using ChIP-seq on Sua7(TFIIB) in WT and spt4∆ cells. Results: The interaction between the Spt4/5 complex and RNAPII periodically changes as RNAPII transitions through nucleosomes. The dynamic interaction of Spt5 with RNAPII is dependent on Spt4. In spt4∆ and Spt4 AA cells, RNAPII distribution is altered in a similar way compared to their respective controls. After transcribing into nucleosomes, RNAPII accumulates upstream of nucleosome dyads, especially around the +2 nucleosome. In Spt5 AA cells, the distribution and amount of RNAPII on genes are severely affected. Nucleosome positions are altered in spt4∆ cells. Although the position of the +1 nucleosome remains unchanged, nucleosome spacing from this point is increased, and the level of increase in nucleosome spacing correlates with the level of RNAPII accumulation. Conclusion: This work suggests that Spt4 regulates nucleosome positioning by a mechanism related to transcription and promotes RNAPII movement through nucleosome barriers, especially the barrier set by the +2 nucleosome.
Project description:The carboxy-terminal domain (CTD) of the largest subunit of RNA Polymerase II (RNAPII) consists of multiple tandem repeats of the heptapeptide consensus Y1-S2-P3-T4-S5-P6-S7. RNAPII CTD is intrinsically disordered and has been shown to promote liquid-liquid phase-separation (LLPS) of RNAPII in vivo. However, understanding the precise role of the conserved heptad residues in LLPS has been hampered by the lack of direct characterization of the biochemical properties of the CTD. Here, we generated a systematic array of RNAPII CTD variants to unravel the sequence-encoded molecular grammar underlying LLPS of the human CTD.
Project description:Bottom-up proteomics database search algorithms used for peptide identification cannot comprehensively identify posttranslational modifications (PTMs) in a single-pass because of high false discovery rates (FDRs). A new approach to database searching enables Global PTM (G-PTM) identification by exclusively looking for curated PTMs, thereby avoiding the FDR penalty experienced during conventional variable modification searches. We identified nearly 2500 unique, high-confidence modified peptides comprising 31 different PTM types in single-pass database searches.
Project description:We present a strategy termed PASS-DIA (Precursor ion And Small Slice-DIA) in which MS/MS spectra are acquired with small isolation window (slices) and MS/MS spectra are interpreted with accurately measured precursor ion masses. This method enables direct application of conventional spectrum-centric analysis pipelines for peptide identification and precursor ion-based quantitation. The performance of PASS-DIA was superior to both DDA and conventional DIA experiment with regard to identification of peptides. Application of PASS-DIA for analysis of samples with post-translationally modified peptides such as phosphorylation and N-glycosylation again revealed its superior performance. Finally, use of PASS-DIA to characterize a rare proteome of human fallopian tube organoid samples revealed biologically relevant and low abundance proteins. Overall, PASS-DIA is a novel DIA approach for use as a discovery tool which outperforms both conventional DDA and DIA experiments to provide additional protein information. We believe that PASS-DIA method could become an important strategy for discovery type studies when deeper proteome characterization is required.
Project description:Deregulation of RNA Polymerase II (RNAPII) by oncogenic signaling leads to collisions of RNAPII with DNA synthesis machinery (transcription-replication conflicts, TRCs). TRCs can result in DNA damage and underlie genomic instability in tumor cells. Here we provide evidence that elongating RNAPII promotes activation of the ATM kinase at TRCs to drive DNA repair. We show the ATPase Wrnip1 that binds and protects stalled replication forks, associates with RNAPII and limits ATM activation. Wrnip1 binding to elongating RNAPII requires catalytic activity of the ubiquitin ligase Huwe1. Mutation of Huwe1 promotes the transfer of Wrnip1 onto replisome and induces TRCs stimulating ATM activation on RNAPII. This mechanism is evoked early upon replicative stress to induce Wrnip1 translocation and ATM signaling at TRCs. Thus, although primarily considered as genotoxic events, TRCs can provide a mechanism to maintain genome stability under replicative stress.
Project description:The C-terminal domain (CTD) of RNA polymerase II (RNAPII) is composed of heptapeptide repeats, which play a key regulatory role in gene expression. Using genetic interaction and mRNA expression analysis we found that truncating the CTD resulted in distinct changes to cellular function. Truncating the CTD altered RNAPII occupancy to not only cause decreases, but also increases in mRNA levels. The latter were largely mediated by promoter elements, and in part were linked to the transcription factor Rpn4. The mediator subunit Cdk8 was enriched at promoters of these genes, and its removal not only restored normal mRNA and RNAPII occupancy levels, but also reduced the abnormally high cellular amounts of Rpn4. This suggested a positive role of Cdk8 in relationship to RNAPII, which contrasted with the negative role at the activated INO1 gene. Here, loss of CDK8 suppressed the reduced mRNA expression and RNAPII occupancy levels of CTD truncation mutants. Two channel microarrays were used. RNA isolated from a large amount of wt yeast from a single culture was used as a common reference. This common reference was used in one of the channels for each hybridization and used in the statistical analysis to obtain an average expression-profile for each deletion mutant relative to the wt. Two independent cultures were hybridized on two separate microarrays. For the first hybridization the Cy5 (red) labeled cRNA from the deletion mutant is hybridized together with the Cy3 (green) labeled cRNA from the common reference. For the replicate hybridization, the labels are swapped. Each gene is represented twice on the microarray, resulting in four measurements per mutant. Using the Erlenmeyer growth protocol up to five deletion strains were grown on a single day. In the tecan platereader, up to eleven deletion strains could be grown on a single day. Wt cultures were grown parallel to the deletion mutants to assess day-to-day variance.
Project description:ChIP-chip by array of Rpb3 localization in yeast with different CTD lenghts and with or without CDK8 deletion to determine the role of CTD length and Cdk8 on RNAPII localization
Project description:We generated high-throughput sequencing (ChIP-seq) data for genome wide occupancy of hDot1L and RNAPII-5p in human embryonic carcinoma cell. Performing ChIP-seq for hDot1L and RNAPII-5p in NCCIT cell lines (embryonic carcinoma cell lines in human).