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Dot1 promotes H2B ubiquitination by a methyltransferase-independent mechanism.

ABSTRACT: The histone methyltransferase Dot1 is conserved from yeast to human and methylates lysine 79 of histone H3 (H3K79) on the core of the nucleosome. H3K79 methylation by Dot1 affects gene expression and the response to DNA damage, and is enhanced by monoubiquitination of the C-terminus of histone H2B (H2Bub1). To gain more insight into the functions of Dot1, we generated genetic interaction maps of increased-dosage alleles of DOT1. We identified a functional relationship between increased Dot1 dosage and loss of the DUB module of the SAGA co-activator complex, which deubiquitinates H2Bub1 and thereby negatively regulates H3K79 methylation. Increased Dot1 dosage was found to promote H2Bub1 in a dose-dependent manner and this was exacerbated by the loss of SAGA-DUB activity, which also caused a negative genetic interaction. The stimulatory effect on H2B ubiquitination was mediated by the N-terminus of Dot1, independent of methyltransferase activity. Our findings show that Dot1 and H2Bub1 are subject to bi-directional crosstalk and that Dot1 possesses chromatin regulatory functions that are independent of its methyltransferase activity.

SUBMITTER: van Welsem T

PROVIDER: S-EPMC6265471 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Histone H2B C-terminal helix mediates trans-histone H3K4 methylation independent of H2B ubiquitination.

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Fbxl19 recruits Rnf20 to CpG Islands and promotes H2B mono-ubiquitination

Project description:This SuperSeries is composed of the SubSeries listed below.

2016-10-01 | GSE76570 | GEO

Regulation of the Dot1 histone H3K79 methyltransferase by histone H4K16 acetylation.

Project description:Dot1 (disruptor of telomeric silencing-1), the histone H3 lysine 79 (H3K79) methyltransferase, is conserved throughout evolution, and its deregulation is found in human leukemias. Here, we provide evidence that acetylation of histone H4 allosterically stimulates yeast Dot1 in a manner distinct from but coordinating with histone H2B ubiquitination (H2BUb). We further demonstrate that this stimulatory effect is specific to acetylation of lysine 16 (H4K16ac), a modification central to chromatin structure. We provide a mechanism of this histone cross-talk and show that H4K16ac and H2BUb play crucial roles in H3K79 di- and trimethylation in vitro and in vivo. These data reveal mechanisms that control H3K79 methylation and demonstrate how H4K16ac, H3K79me, and H2BUb function together to regulate gene transcription and gene silencing to ensure optimal maintenance and propagation of an epigenetic state.

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Histone H2B ubiquitylation promotes activity of the intact Set1 histone methyltransferase complex in fission yeast.

Project description:The methylation of histone H3 at lysine 4 (H3K4me) is critical for the formation of transcriptionally active chromatin in eukaryotes. In yeast, Drosophila, and some human cell lines, H3K4me is globally stimulated by the monoubiquitylation of histone H2B (H2Bub1), another histone modification associated with transcription. The mechanism of this "trans-histone" modification pathway remains uncertain, and studies carried out in different experimental systems have suggested that H2Bub1 could either influence the subunit composition of methyltransferase complexes or directly stimulate methyltransferase activity. We have reconstituted this pathway in vitro using the native H3K4-specific methyltransferase complex Set1C purified from the fission yeast Schizosaccharomyces pombe and chromatin substrates that contain semisynthetic H2Bub1. We found that the activity of S. pombe Set1C toward nucleosomal histone H3 is directly enhanced by H2Bub1 in vitro. Importantly, Set1C purified from cells lacking H2Bub1 retained activity on free histone substrates, suggesting that Set1C remains intact in the absence of H2Bub1. Chromatin immunoprecipitation assays revealed a defect in recruitment of intact Set1C to transcribed chromatin in H2Bub1-deficient mutants. Our data argue that trans-histone crosstalk in S. pombe involves direct enhancement of Set1C methyltransferase activity by H2Bub1 and suggest that this represents a conserved aspect of H2Bub1-H3K4me crosstalk in eukaryotes.

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Fbxl19 recruits Rnf20 to CpG Islands and promotes H2B mono-ubiquitination [Affymetrix]

Project description:Rnf20 catalyzes lysine 120 mono-ubiquitination of histone H2B (H2Bub1) that has been previously involved in normal differentiation of embryonic stem (ES) and adult stem cells. However, the mechanisms underlying by which Rnf20 is recruited to its target chromosomal loci to generate H2Bub1 are still elusive. Here, we reveal that Fbxl19, a CxxC domain-containing protein, physically interacts with Rnf20, guides it preferentially to CpG island-containing target promoters, and thereby promotes mono-ubiqutination of H2B. We first show that up-regulation of Fbxl19 induces the level of global H2Bub1, while down-regulation of Fbxl19 reduces the level of H2Bub1 in mouse ES cells. Our genome-wide target mapping unveils the preferential occupancy of Fbxl19 on CpG island-containing promoters, and we further show that the binding of Fbxl19 is essential for the recruitment of Rnf20 to its target genes and subsequent H2Bub1. Altogether, our results demonstrate that Fbxl19 plays critical roles in the H2Bub1 pathway by recruiting Rnf20 to CGI target genes specifically and selectively.

2016-10-01 | GSE76558 | GEO

H2B ubiquitination regulates meiotic recombination by promoting chromatin relaxation.

Project description:Meiotic recombination is essential for fertility in most sexually reproducing species, but the molecular mechanisms underlying this process remain poorly understood in mammals. Here, we show that RNF20-mediated H2B ubiquitination is required for meiotic recombination. A germ cell-specific knockout of the H2B ubiquitination E3 ligase RNF20 results in complete male infertility. The Stra8-Rnf20-/- spermatocytes arrest at the pachytene stage because of impaired programmed double-strand break (DSB) repair. Further investigations reveal that the depletion of RNF20 in the germ cells affects chromatin relaxation, thus preventing programmed DSB repair factors from being recruited to proper positions on the chromatin. The gametogenetic defects of the H2B ubiquitination deficient cells could be partially rescued by forced chromatin relaxation. Taken together, our results demonstrate that RNF20/Bre1p-mediated H2B ubiquitination regulates meiotic recombination by promoting chromatin relaxation, and suggest an old drug may provide a new way to treat some oligo- or azoospermia patients with chromatin relaxation disorders.

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