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Cdk1-dependent phosphorylation of Clr4Suv39H controls a histone H3 methylation switch that is essential for gametogenesis

ABSTRACT: Methylation of histone H3 at lysine 9 (H3K9) is a hallmark of heterochromatin that plays crucial roles in chromatin-dependent gene silencing and maintenance of genome stability by repressing repetitive DNA elements and recruiting downstream factors essential for faithful chromosome segregation. Fundamental principles of these processes have been elucidated in the fission yeast Schizosaccharomyces pombe (S. pombe), in which Clr4, the homologue of mammalian SUV39H, is the sole H3K9 methyltransferase. Although H3K9 methylation has been intensely studied in mitotic cells, occurrence and regulation during sexual differentiation remain largely unknown. Whether distinct H3 methylation states are relevant for gametogenesis is also not known. Here, using diploid S. pombe cells, we map H3K9 methylation genome-wide during the meiotic program and show that constitutive heterochromatin temporarily loses H3K9me2 and becomes H3K9me3 when cells exit mitosis and commit to the meiotic life cycle. Cells lacking the ability to tri-methylate H3K9 exhibit severe meiotic chromosome segregation defects, which does not occur in mitotic cells. Artificially increasing the affinity of the fission yeast heterochromatin protein 1 (HP1) homologue Swi6 towards H3K9me2 rescues chromosome segregation in the absence of H3K9me3. Thus, the H3K9me2 to H3K9me3 switch during early meiosis serves to retain Swi6 at centromeres, which is necessary for cohesin recruitment and kinetochore assembly. Finally, we show that the H3K9 methylation switch is regulated by differential phosphorylation of Clr4 by the cyclin-dependent kinase (CDK) Cdk1. Our results reveal how a highly conserved master regulator of the cell cycle regulates the specificity of the H3K9 methyltransferase and thereby controls the ratio of H3K9me2 to H3K9me3 to prevent unwanted gene silencing and to ensure faithful meiotic chromosome segregation. High degree of conservation of the proteins involved in our study and CDK-dependent phosphorylation of the mammalian SUV39H1 homologue suggest broad conservation of the mechanisms described here.

ORGANISM(S): Schizosaccharomyces pombe

PROVIDER: GSE182250 | GEO | 2022/10/17

REPOSITORIES: GEO

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Project description:We have characterized two post-translational histone modifications in C. elegans on a genomic scale. Micrococcal nuclease digestion and immunoprecipitation were used to obtain distinct populations of single nucleosome cores, which were analyzed using massively parallel DNA sequencing to obtain positional and coverage maps. Two methylated histone H3 populations were chosen for comparison: H3K4 histone methylation (associated with active chromosomal regions) and H3K9 histone methylation (associated with inactivity). From analysis of the sequence data, we found nucleosome cores with these modifications to be enriched in two distinct partitions of the genome; H3K4 methylation was particularly prevalent in promoter regions of widely-expressed genes while H3K9 methylation was enriched on specific chromosomal arms. For each of the six chromosomes, the highest level of H3K9 methylation corresponds to the pairing center responsible for chromosome alignment during meiosis. H3K9 enrichment at pairing centers appears to be an early mark in meiotic chromosome sorting, occurring in the absence of components required for proper pairing of homologous chromosomes. H3K9 methylation shows an intricate pattern within the chromosome arms, with a particular anti-correlation to regions that display a strong ~10 bp periodicity of AA/TT dinucleotides that is known to associate with germline trancription. By contrast to the global features observed with H3K9 methylation, H3K4 methylation profiles were most striking in their local characteristics around promoters, providing a unique promoter-central landmark for 3903 C. elegans genes and allowing a precise analysis of nucleosome positioning in the context of transcriptional initiation. Keywords: epigenetics Examination of total nucleosome and nucleosomes with 2 different histone modifications in C. elegans. 5 samples are analyzed: 1. total mononucleosome core DNA from C. elegans wild type strain N2, 2. anti-H3K4me2/3 precipitated mononucleosome core DNA from C. elegans wild type strain N2, 3. anti-H3K9me3 precipitated mononucleosome core DNA from C. elegans wild type strain N2, 4. total mononucleosome core DNA from C. elegans mutant strain zim-2(tm-574), 5. anti-H3K9me3 precipitated mononucleosome core DNA from C. elegans mutant strain zim-2(tm-574)

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Cdk1-dependent phosphorylation of Clr4Suv39H controls a histone H3 methylation switch that is essential for gametogenesis

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