Asymmetric distribution of H3K9me3 at replicating DNA strands silences L1 retrotransposons during S phase
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ABSTRACT:
PROVIDER: PRJNA869455 | ENA |
REPOSITORIES: ENA
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Project description:In higher eukaryotes, repetitive DNA sequences are transcriptionally silenced through histone H3 lysine 9 tri-methylation (H3K9me3). A loss of silencing of these elements leads to genome instability and human diseases, including cancer and aging1-3. While the role of H3K9me3 in the establishment and maintenance of heterochromatin and repression of DNA repeats has been extensively studied4-6, the pattern and mechanism underlying the partitioning of H3K9me3 at replicating DNA strands were unknown. Here, we report that H3K9me3 is preferentially transferred onto the leading strands of replication forks, which occurs predominantly at Long Interspersed Nuclear Element (LINE) retrotransposons that are theoretically transcribed at the head-on direction with replication fork movement. In contrast, all other modified forms of histones tested are distributed in a nearly symmetric manner at the leading and lagging strands. Mechanistically, the Human Silencing Hub (HUSH) complex interacts with the leading strand DNA polymerase Pol ε, and contributes to the asymmetric segregation of H3K9me3 during chromatin replication. Cells deficient for Pol ε (POLE3 and POLE4), the HUSH complex (MPP8 and TASOR), or cells expressing a MPP8 mutant defective of H3K9me3 binding, or TASOR mutants with reduced interaction with Pol ε, show compromised H3K9me3 asymmetry and increased LINE expression. These results reveal an unexpected mechanism whereby the HUSH complex functions with Pol ε to promote asymmetric H3K9me3 distribution at LINEs to suppress their expression during S phase.
2023-08-17 | GSE211192 | GEO
Project description:In eukaryotic cells, inheritable changes in gene expression in response to environmental and developmental stimuli is associated with changes in histone modifications and relies on the passage of these changes into daughter cells during cell division, a process that remains elusive. Here, we show that parental histone (H3-H4)2 tetramers, the primary carrier of epigenetic modifications, are assembled into nucleosomes onto both replicating leading and lagging strands, with a preference for lagging strands of DNA replication forks. This asymmetric distribution of parental (H3-H4)2 is exacerbated in cells lacking Dpb3 and Dpb4, two subunits of DNA polymerase Pol ε. Dpb3-Dpb4 binds (H3-H4)2 and participates in the transfer of parental (H3-H4)2 tetramers onto leading strands of DNA replication forks. Cells lacking Dpb3 and Dpb4 exhibits defects in epigenetic inheritance. These results reveal a previously undocumented mechanism of histone segregation and a direct role for Pol ε in this poorly understood process.
2018-08-28 | GSE112522 | GEO
Project description:Asymmetric partition of parental histone (H3-H4)2 tetramers onto replicating DNA strands
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Project description:Although essential for epigenetic inheritance, the transfer of parental histone (H3-H4)2 tetramers that contain epigenetic modifications to replicating DNA strands is poorly understood. Here, we show that the Mcm2-Ctf4-Pol axis facilitates the transfer of parental (H3-H4)2 tetramers to lagging strands of DNA replication forks. Mutating the H3-H4 binding domain of Mcm2, a subunit of the CMG (Cdc45-MCM-GINS) replicative helicase that translocates along leading strands, impairs the transfer of parental (H3-H4)2 to lagging strands. Similar effects are observed in Ctf4 and Pol-primase mutants that disrupt the connection of the CMG helicase via Ctf4-Pol to lagging strands. Our results support a model whereby parental (H3-H4)2 displaced from nucleosomes through leading-strand DNA replication are transferred to lagging strands for nucleosome assembly via the CMG-Ctf4-Pol complex.
2018-09-24 | GSE118580 | GEO
Project description:How parental histone (H3-H4)2 tetramers, the primary carriers of epigenetic modifications, are transferred onto leading and lagging strands of DNA replication forks for epigenetic inheritance remains elusive. Here we show that parental (H3-H4)2 tetramers are assembled into nucleosomes onto both leading and lagging strands, with a slight preference for lagging strands. The lagging-strand preference increases markedly in budding yeast cells lacking Dpb3 and Dpb4, two subunits of the leading strand DNA polymerase, Pol ε, owing to the impairment of parental (H3-H4)2 transfer to leading strands. Dpb3-Dpb4 binds H3-H4 in vitro and participates in the inheritance of heterochromatin. These results indicate that different proteins facilitate the transfer of parental (H3-H4)2 onto leading versus lagging strands and that Dbp3-Dpb4 plays an important role in this poorly understood process.
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Project description:The RNA modification N6-methyladenosine (m6A) has critical roles in many biological processes. However, the function of m6A in the early phase of mammalian development remains poorly understood. Here we show that the m6A reader YT521-B homology-domain-containing protein 1 (YTHDC1) is required for the maintenance of mouse embryonic stem (ES) cells in an m6A-dependent manner, and that its deletion initiates cellular reprogramming to a 2C-like state. Mechanistically, YTHDC1 binds to the transcripts of retrotransposons (such as intracisternal A particles, ERVK and LINE1) in mouse ES cells and its depletion results in the reactivation of these silenced retrotransposons, accompanied by a global decrease in SETDB1-mediated trimethylation at lysine 9 of histone H3 (H3K9me3). We further demonstrate that YTHDC1 and its target m6A RNAs act upstream of SETDB1 to repress retrotransposons and Dux, the master inducer of the two-cell stage (2C)-like program. This study reveals an essential role for m6A RNA and YTHDC1 in chromatin modification and retrotransposon repression. This SuperSeries is composed of the SubSeries listed below.
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Project description:RNAi is a conserved mechanism in which small interfering RNAs (siRNAs) guide the degradation of cognate RNAs, but also promote heterochromatin assembly at repetitive DNA elements such as centromeric repeats. However, the full extent of RNAi functions and its endogenous targets have not been explored. Here we show that in the fission yeast Schizosaccharomyces pombe, RNAi and heterochromatin factors cooperate to silence diverse loci, including sexual differentiation genes, genes encoding transmembrane proteins, and retrotransposons that are also targeted by the exosome RNA degradation machinery. In the absence of the exosome, transcripts are processed preferentially by the RNAi machinery, revealing widespread occurrence of siRNA clusters and corresponding increase in heterochromatin modifications across large domains. We show that the generation of siRNAs and heterochromatin assembly by RNAi is triggered by a mechanism involving the canonical poly(A) polymerase Pla1 and an associated RNA surveillance factor Red1, which also activate the exosome. Remarkably, siRNA production and heterochromatin modifications at genes are regulated by environmental growth conditions, and by developmental signals that induce gene expression during sexual differentiation. Our analyses uncover interplay between RNAi and the exosome that is conserved in higher eukaryotes, and show that differentiation signals modulate RNAi silencing to regulate developmental genes. 8 ChIP samples
2012-11-26 | E-GEOD-41642 | biostudies-arrayexpress
Project description:RNAi is a conserved mechanism in which small interfering RNAs (siRNAs) guide the degradation of cognate RNAs, but also promote heterochromatin assembly at repetitive DNA elements such as centromeric repeats. However, the full extent of RNAi functions and its endogenous targets have not been explored. Here we show that in the fission yeast Schizosaccharomyces pombe, RNAi and heterochromatin factors cooperate to silence diverse loci, including sexual differentiation genes, genes encoding transmembrane proteins, and retrotransposons that are also targeted by the exosome RNA degradation machinery. In the absence of the exosome, transcripts are processed preferentially by the RNAi machinery, revealing widespread occurrence of siRNA clusters and corresponding increase in heterochromatin modifications across large domains. We show that the generation of siRNAs and heterochromatin assembly by RNAi is triggered by a mechanism involving the canonical poly(A) polymerase Pla1 and an associated RNA surveillance factor Red1, which also activate the exosome. Remarkably, siRNA production and heterochromatin modifications at genes are regulated by environmental growth conditions, and by developmental signals that induce gene expression during sexual differentiation. Our analyses uncover interplay between RNAi and the exosome that is conserved in higher eukaryotes, and show that differentiation signals modulate RNAi silencing to regulate developmental genes. We sequenced 7 samples from Schizosaccharomyces pombe and 2 samples from Drosophila melanogaster.
2012-11-26 | E-GEOD-41634 | biostudies-arrayexpress