Project description:Histone H2B mono-ubiquitylation (H2Bub1) and phosphorylation of elongation factor Spt5 by cyclin-dependent kinase 9 (Cdk9) occur during transcription by RNA polymerase II (RNAPII), and are mutually dependent in fission yeast. How Cdk9 activity and H2Bub1 cooperate to regulate the expression of individual genes remains unclear. Here we show Cdk9 inhibition or H2Bub1 loss induces intragenic antisense transcription of distinct gene subsets; ablation of both pathways derepresses antisense transcription of over half the genome. H2Bub1 and phospho-Spt5 have similar genome-wide distributions; both are enriched in coding regions, and H2Bub1 levels are directly proportional to those of phospho-Spt5. Cdk9-dependence of antisense suppression correlates with high H2Bub1 occupancy, and with promoter-proximal RNAPII pausing. Combined reduction of Cdk9 activity and loss of H2Bub1 prevent recruitment of the histone deacetylase Clr6-CII to transcribed genes, and lead to decreased histone occupancy and increased histone acetylation within gene coding regions. These results uncover new pathways linking regulators of RNAPII transcription elongation to suppression of aberrant antisense transcription, and demonstrate novel interactions between co-transcriptional histone modification pathways.
Project description:Transcript elongation by RNA polymerase II (RNAPII) is accompanied by conserved patterns of histone modification within transcribed regions, but it remains uncertain how these modifications influence, or are influenced by, properties of the elongation complex. Here we establish an intimate link between Cdk9, the kinase component of positive transcription elongation factor b (P-TEFb), and mono-ubiquitylation of histone H2B (H2Bub1), in the fission yeast Schizosaccharomyces pombe. Mutations that impair Cdk9 function reduce H2Bub1 levels in vivo. Conversely, mutations that prevent H2Bub1 decrease phosphorylation of elongation factor subunit Spt5, a sensitive and specific indicator of Cdk9 activity. Chromatin immunoprecipitation (ChIP) analysis suggests this is due to impaired Cdk9 recruitment to H2Bub1-deficient chromatin. P-TEFb and H2Bub1 pathways also interact genetically: mutation of the histone H2B ubiquitin-acceptor residue decreases the requirement for Cdk9 activity in vivo, and multiple cdk9 mutations suppress morphological defects of H2Bub1-deficient strains. Moreover, H2Bub1 loss causes redistribution of transcribing RNAPII on chromatin that is corrected by a hypomorphic cdk9 mutation. Therefore, whereas mutual dependence of Spt5 phosphorylation and H2Bub1 suggests positive feedback between P-TEFb and the ubiquitylation machinery, mutual suppression by cdk9 and H2Bub1-pathway mutations indicates an antagonistic relationship, whereby the activities must be balanced to properly regulate elongation. In order to study the genome-wide localization of H2Bub1 in Schizosaccharomyces pombe, H2Bub1, H2B-Flag as well as RNAPII (along with associated DNA sequences) were immunoprecipitated using repectively anti-H2Bub1, anti-Flag and anti-8WG16 antibodies. The ChIPs were performed in duplicate from WT cells as well as in the H2B-K119R mutant. The extracted DNA was hybridized to a DNA microarray containing an average of 4 probes per kilobase across the whole yeast genome. The combined datasets are available in the supplemental files of the related publication.
Project description:Transcript elongation by RNA polymerase II (RNAPII) is accompanied by conserved patterns of histone modification within transcribed regions, but it remains uncertain how these modifications influence, or are influenced by, properties of the elongation complex. Here we establish an intimate link between Cdk9, the kinase component of positive transcription elongation factor b (P-TEFb), and mono-ubiquitylation of histone H2B (H2Bub1), in the fission yeast Schizosaccharomyces pombe. Mutations that impair Cdk9 function reduce H2Bub1 levels in vivo. Conversely, mutations that prevent H2Bub1 decrease phosphorylation of elongation factor subunit Spt5, a sensitive and specific indicator of Cdk9 activity. Chromatin immunoprecipitation (ChIP) analysis suggests this is due to impaired Cdk9 recruitment to H2Bub1-deficient chromatin. P-TEFb and H2Bub1 pathways also interact genetically: mutation of the histone H2B ubiquitin-acceptor residue decreases the requirement for Cdk9 activity in vivo, and multiple cdk9 mutations suppress morphological defects of H2Bub1-deficient strains. Moreover, H2Bub1 loss causes redistribution of transcribing RNAPII on chromatin that is corrected by a hypomorphic cdk9 mutation. Therefore, whereas mutual dependence of Spt5 phosphorylation and H2Bub1 suggests positive feedback between P-TEFb and the ubiquitylation machinery, mutual suppression by cdk9 and H2Bub1-pathway mutations indicates an antagonistic relationship, whereby the activities must be balanced to properly regulate elongation.
Project description:In Saccharomyces cerevisiae histone H2B is ubiquitylated at lysine 123. The SAGA complex component, Ubp8, is one of two proteases that remove this ubiquitin moiety. We analyzed gene expression in a strain containing a variant of histone H2B with lysine 123 converted to arginine to address the mechanisms by which ubiquitylation and deubiquitylation of histone H2B affects gene expression. We show that changes in gene expression observed upon deletion of ubp8 are suppressed by htb1K123R. This provides genetic evidence that Ubp8 alters gene expression through deubiquitylation of histone H2B. Second, microarray analyses of the htb1K123R strain show that loss of histone ubiquitylation results in a two-fold or greater change in expression of ~1.5% of the protein coding genes with greater than two-thirds increasing. For genes in which ubiquitylation represses expression, ubiquitylation principally acts through its effects on histone methylation. In contrast, decreased expression of the CWP1 gene was not paralleled by deletions of the methyltransferase components Swd3, Set2 or Dot1 and is thus likely independent of methylation. Finally, by comparing gene expression changes in the htb1K123R strain with those in a strain deleted for rad6, we conclude that lysine 123 affects transcription primarily because of its being a site of ubiquitylation. Keywords: yeast, histone ubiquitylation, Ubp8, gene expression, genetic modification, histone H2B Two dye-swapped, biological replicate experiments were performed for yeast strains CY1272(Htb1_K123R;htb2_delta0), BY10809(ubp8_delta0) and CY1383(Htb1_K123R;htb2_delta0;ubp8_delta0) with reference to BY4742(wt). Three biological replicates, including one dye-swap experiment, were performed comparing CY1272(Htb1_K123R;htb2_delta0) to BY13026(htb2_delta0).
Project description:Transcription by RNA polymerase II is regulated by epigenetic modifications to the chromatin template. The mono-ubiquitylation of H2B is established during transcription elongation and broadly impacts chromatin architecture and gene expression. The Polymerase Associated Factor 1 complex (Paf1C) is required for H2B ubiquitylation through an unknown mechanism. Here, we find that a 66-amino acid histone modification domain (HMD) within the Rtf1 subunit of Paf1C promotes H2B ubiquitylation in cells lacking all Paf1C members and present the crystal structure of this domain. Using site-specific in vivo crosslinking, we show that Rtf1 directly interacts with the ubiquitin conjugase Rad6 through a conserved surface on the HMD. Through ChIP-exo analysis, we observe that enrichment of Paf1C correlates with H2B ubiquitylation, and that the HMD, Rad6 and Bre1 localize to H2B. Finally, we demonstrate that the HMD directly stimulates H2B ubiquitylation in a reconstituted system, arguing that Paf1C functions as a cofactor for Rad6-Bre1 mediated catalysis.
Project description:In Saccharomyces cerevisiae histone H2B is ubiquitylated at lysine 123. The SAGA complex component, Ubp8, is one of two proteases that remove this ubiquitin moiety. We analyzed gene expression in a strain containing a variant of histone H2B with lysine 123 converted to arginine to address the mechanisms by which ubiquitylation and deubiquitylation of histone H2B affects gene expression. We show that changes in gene expression observed upon deletion of ubp8 are suppressed by htb1K123R. This provides genetic evidence that Ubp8 alters gene expression through deubiquitylation of histone H2B. Second, microarray analyses of the htb1K123R strain show that loss of histone ubiquitylation results in a two-fold or greater change in expression of ~1.5% of the protein coding genes with greater than two-thirds increasing. For genes in which ubiquitylation represses expression, ubiquitylation principally acts through its effects on histone methylation. In contrast, decreased expression of the CWP1 gene was not paralleled by deletions of the methyltransferase components Swd3, Set2 or Dot1 and is thus likely independent of methylation. Finally, by comparing gene expression changes in the htb1K123R strain with those in a strain deleted for rad6, we conclude that lysine 123 affects transcription primarily because of its being a site of ubiquitylation. Keywords: yeast, histone ubiquitylation, Ubp8, gene expression, genetic modification, histone H2B
Project description:Nucleosome dynamics facilitated by histone turnover is required for transcription as well as DNA replication and repair. Histone turnover is often associated with various histone modifications such as H3K56 acetylation (H3K56Ac), H3K36 methylation (H3K36me), and H4K20 methylation (H4K20me). In order to correlate histone modifications and transcription-dependent histone turnover, we performed genome wide analyses for euchromatic regions in G2/M-arrested fission yeast. The results show that transcription-dependent histone turnover at 5’ promoter and 3’ termination regions is directly correlated with the occurrence of H3K56Ac and H4K20 mono-methylation (H4K20me1) in actively transcribed genes. Furthermore, the increase of H3K56Ac and H4K20me1 and antisense RNA production was observed in the absence of the histone H3K36 methyltransferase Set2 and histone deacetylase complex (HDAC) that are involved in the suppression of histone turnover within the coding regions. These results together indicate that H4K20me1 as well as H3K56Ac are bona fide marks for transcription-dependent histone turnover in fission yeast.
Project description:The influence of mono-ubiquitylation of histone H2B (H2Bub) on transcription via nucleosome reassembly has been widely documented. Recently, it has also been shown that H2Bub promotes recovery from replication stress; however, the underling molecular mechanism remains unclear. Here, we show that H2B ubiquitylation coordinates activation of the intra-S replication checkpoint and chromatin re-assembly, in order to limit fork progression and DNA damage in the presence of replication stress. In particular, we show that the absence of H2Bub affects replication dynamics (enhanced fork progression and reduced origin firing), leading to γH2A accumulation and increased hydroxyurea sensitivity. Further genetic analysis indicates a role for H2Bub in transducing Rad53 phosphorylation. Concomitantly, we found that a change in replication dynamics is not due to a change in dNTP level, but is mediated by reduced Rad53 activation and destabilization of the RecQ helicase Sgs1 at the fork. Furthermore, we demonstrate that H2Bub facilitates the dissociation of the histone chaperone Asf1 from Rad53, and nucleosome reassembly behind the fork is compromised in cells lacking H2Bub. Taken together, these results indicate that the regulation of H2B ubiquitylation is a key event in the maintenance of genome stability, through coordination of intra-S checkpoint activation, chromatin assembly and replication fork progression. S.cerevisiae oligonucleotide microarrays were provided by Affymetrix (S.cerevisiae Tiling 1.0R, P/N 900645). BrdU and proteins ChIP-chip analyses were carried out as described (Fachinetti et al., M Cell, 2010).
Project description:In Penicillium oxalicum, histone H2B (PDE_01489) was one of the interacting proteins with the methyltransferase LaeA. It suggests that histone H2B may be a direct target of LaeA/Lae1. To verify whether histone H2B is one of the LaeA targets, an in vitro catalytic experiment was performed using Homo sapiens recombinant histone H2B (HsH2B, expressed in Escherichia coli, without histone modification), SAM as substrates, and LaeA. The products were analyzed by LC-MS/MS for histone modifications. Results showed that the mono and di-methylation of lysine 108 and the mono-methylation of lysine 116 were detected.