Project description:Meiotic DSB, catalyzed by the Spo11 transesterase protein and accessory DSB proteins, form in the nucleosome depleted regions (NDR) at promoters, preferentially those located on the chromosome loops that shape meiotic chromosomes, whereas the DSB proteins are located on chromosome axes at the basis of these loops. Mechanisms bridging these two chromosomal regions for DSB formation have remained elusive. Here we show that Spp1, a conserved member of the histone H3K4 methyltransferase Set1 complex, is required for normal levels of DSB formation and is associated with chromosome axes in the DSB-rich domains during meiosis. Moreover, Spp1 physically interacts with the Mer2 axis-associated DSB protein, and uses its PHD finger as a magnet to read H3K4 trimethylation close to promoters, tether these regions to chromosome axes and activate cleavage in the nearby promoter by the DSB proteins. We further show that in the absence of Spp1 or the Set1 complex, DSB are introduced at a few new sites, located in promoters of transcriptionally induced genes, suggesting another selection mechanism of preferred DSB sequences. This paper provides the molecular mechanism linking H3K4me3 to the DSB forming machinery, by the meiosis-specific specialization of Spp1 as an active member of the DSB complex and a reader of H3K4me3, and opens perspectives for the study of DSB formation at mammalian recombination hotspots that are also enriched in H3K4me3. ChIP-chip experiment in vegetative or meiotic diploid SK1 yeast cells - two biological replicates
Project description:Meiotic DSB, catalyzed by the Spo11 transesterase protein and accessory DSB proteins, form in the nucleosome depleted regions (NDR) at promoters, preferentially those located on the chromosome loops that shape meiotic chromosomes, whereas the DSB proteins are located on chromosome axes at the basis of these loops. Mechanisms bridging these two chromosomal regions for DSB formation have remained elusive. Here we show that Spp1, a conserved member of the histone H3K4 methyltransferase Set1 complex, is required for normal levels of DSB formation and is associated with chromosome axes in the DSB-rich domains during meiosis. Moreover, Spp1 physically interacts with the Mer2 axis-associated DSB protein, and uses its PHD finger as a magnet to read H3K4 trimethylation close to promoters, tether these regions to chromosome axes and activate cleavage in the nearby promoter by the DSB proteins. We further show that in the absence of Spp1 or the Set1 complex, DSB are introduced at a few new sites, located in promoters of transcriptionally induced genes, suggesting another selection mechanism of preferred DSB sequences. This paper provides the molecular mechanism linking H3K4me3 to the DSB forming machinery, by the meiosis-specific specialization of Spp1 as an active member of the DSB complex and a reader of H3K4me3, and opens perspectives for the study of DSB formation at mammalian recombination hotspots that are also enriched in H3K4me3.
Project description:Histone H3K4 methylation is a feature of meiotic recombination hotspots shared by many organisms including plants and mammals. Meiotic recombination is initiated by programmed double strand break (DSB) formation that in budding yeast is directed in gene promoters by histone H3K4 di/trimethylation. This histone modification is indeed recognized by Spp1, a PHD-finger containing protein that belongs to the conserved histone H3K4 methyltransferase Set1 complex. During meiosis, Spp1 binds H3K4me and recruits a DSB protein, Mer2, to promote DSB formation close to gene promoters. How Set1C and Mer2 related functions of Spp1 are connected is not clear.
Project description:Histone H3K4 methylation is a feature of meiotic recombination hotspots shared by many organisms including plants and mammals. Meiotic recombination is initiated by programmed double-strand break (DSB) formation that in budding yeast takes place in gene promoters and is promoted by histone H3K4 di/trimethylation. This histone modification is recognized by Spp1, a PHD-finger containing protein that belongs to the conserved histone H3K4 methyltransferase Set1 complex. During meiosis, Spp1 binds H3K4me3 and interacts with a DSB protein, Mer2, to promote DSB formation close to gene promoters. How Set1 complex- and Mer2- related functions of Spp1 are connected is not clear. Here, combining genome-wide localization analyses, biochemical approaches and the use of separation of function mutants, we show that Spp1 is present within two distinct complexes in meiotic cells, the Set1 and the Mer2 complexes. Disrupting the Spp1-Set1 interaction mildly decreases H3K4me3 levels and does not affect meiotic recombination initiation. Conversely, the Spp1-Mer2 interaction is required for normal meiotic recombination initiation, but dispensable for Set1 complex-mediated histone H3K4 methylation. Finally, we provide evidence that Spp1 preserves normal H3K4me3 levels independently of the Set1 complex. We propose a model where Spp1 works in three ways to promote recombination initiation: first by depositing histone H3K4 methylation (Set1 complex), next by “reading” and protecting histone H3K4 methylation, and finally by making the link with the chromosome axis (Mer2-Spp1 complex). This work deciphers the precise roles of Spp1 in meiotic recombination and opens perspectives to study its functions in other organisms where H3K4me3 is also present at recombination hotspots.
Project description:Genomic features of DSB re-landscaping in rtf1 mutants. Histone modification is a critical determinant of frequency and location of double-strand breaks (DSBs), which induce recombination during meiosis. The Set1-dependent histone H3K4 and Dot1-dependent H3K79 methylations play an important role in DSB formations in budding yeast. Both methylations are promoted by the RNA polymerase II associated factor 1 (Paf1) complex, Paf1C. This study addressed a role of the Paf1C component Rtf1, which is critical for H3K4 and H3K79 methylations, for the regulation of meiotic DSB formation. Similar to set1 mutation, rtf1 mutation decreased the occurrence of DSBs in the genome. The rtf1 set1 double mutant exhibited a larger reduction in the levels of DSBs than the frequency of DSBs detected in either of the single mutants; this indicates independent roles of Rtf1 and Set1 in DSB formation. Importantly, the distribution of DSBs along chromosomes in the rtf1 mutant changed in a different manner than the pattern observed in the set1 and set1 dot1 mutants; this was characterized by enhanced DSB formation at some DSB-cold regions. These observations suggest that Rtf1, and, possibly, the Paf1C, determine DSB landscape in the genome, independent of H3K4 methylation.
Project description:Histone modifications are associated with meiotic recombination hotspots, discrete sites with augmented recombination frequency. For example, trimethylation of histone H3 lysine4 (H3K4me3) marks most hotspots in budding yeast and mouse. Modified histones are known to regulate meiotic recombination partly by promoting DNA double strand break (DSB) formation, but the role and precise landscape of histone modifications at hotspots remain unclear. Here, we studied hotspot-associated modifications in fission yeast and found general features: acetylation of H3 lysine9 (H3K9ac) is strikingly elevated, and H3K4me3 is not significantly enriched. Remarkably, elimination of H3K9ac reduced binding of the DSB-inducing enzyme Rec12 and DSB at hotspots. We also found that the H3K4 metyltransferase Set1 promotes DSB formation at some loci, but it restricts Rec12 binding to hotspots. These results suggest that H3K9ac rather than H3K4me3 is a hotspot-associated mark involved in meiotic DSB formation in fission yeast. S.pombe cells in a pat1-114 background were induced to enter meiosis by the haploid meiosis system, and harvested one hour after the induction. ChIP were performed using anti-H3Cter, H3K9ac, -H3K14ac and -H3K4me3 antibodies. pat1-114 rad50S rec12+-FLAG cells in a wild type, H3K9A or set1+ deletion background were induced to enter meiosis by the haploid meiosis system, and harvested five hours after the induction. ChIP were performed using anti-FLAG antibodies.
Project description:Histone modifications are associated with meiotic recombination hotspots, discrete sites with augmented recombination frequency. For example, trimethylation of histone H3 lysine4 (H3K4me3) marks most hotspots in budding yeast and mouse. Modified histones are known to regulate meiotic recombination partly by promoting DNA double strand break (DSB) formation, but the role and precise landscape of histone modifications at hotspots remain unclear. Here, we studied hotspot-associated modifications in fission yeast and found general features: acetylation of H3 lysine9 (H3K9ac) is strikingly elevated, and H3K4me3 is not significantly enriched. Remarkably, elimination of H3K9ac reduced binding of the DSB-inducing enzyme Rec12 and DSB at hotspots. We also found that the H3K4 metyltransferase Set1 promotes DSB formation at some loci, but it restricts Rec12 binding to hotspots. These results suggest that H3K9ac rather than H3K4me3 is a hotspot-associated mark involved in meiotic DSB formation in fission yeast.
Project description:In relation with the study of the meiotic dynamic of H3K4 methylation, we determined the meiotic Double Strand Breaks (DSB) profiles of wild-type and set1∆ cells.
Project description:In meiotic cells, chromosomes are organized as chromatin loop arrays anchored to a protein axis. This organization is essential to regulate meiotic recombination, from DNA double-strand break (DSB) formation to their repair. In mammals, it is unknown how chromatin loops are organized along the genome and how proteins participating in DSB formation are tethered to the chromosome axes. Here, we identified three categories of axis-associated genomic sites: PRDM9 binding sites, where DSBs form, binding sites of the insulator protein CTCF, and H3K4me3-enriched sites. We demonstrated that PRDM9 promotes the recruitment of MEI4 and IHO1, two proteins essential for DSB formation. In turn, IHO1 anchors DSB sites to the axis components HORMAD1 and SYCP3. We discovered that IHO1, HORMAD1 and SYCP3 are associated at the DSB ends during DSB repair. Our results highlight how interactions of proteins with specific genomic elements shape the meiotic chromosome organization for recombination.
Project description:Meiotic chromosome architecture called M-bM-^@M-^\axis-loop structuresM-bM-^@M-^] and histone modifications have been demonstrated to regulate the Spo11-dependent formation of DNA double-strand breaks (DSBs) that trigger meiotic recombination. Using genome-wide chromatin immunoprecipitation (ChIP) analyses followed by deep sequencing, we compared the genome-wide distribution of the axis protein Rec8 (the kleisin subunit of meiotic cohesin) with that of oligomeric DNA covalently bound to Spo11, indicative of DSB sites. The frequency of DSB sites is overall constant between Rec8 binding sites. However, DSB cold spots are observed in regions spanning M-BM-10.8 kb around Rec8 binding sites. The axis-associated cold spots are not due to exclusion of Spo11 localization from the axis, since ChIP experiments revealed that substantial Spo11 persists at Rec8 binding sites during DSB formation. Spo11 fused with Gal4 DNA binding domain (Gal4BD-Spo11) tethered in close proximity (M-bM-^IM-$0.8 kb) to Rec8 binding sites hardly forms meiotic DSBs, in contrast with other regions. In addition, H3K4 tri-methylation (H3K4me3) remarkably decreases at Rec8 binding sites. These results suggest that reduced histone H3K4me3 in combination with inactivation of Spo11 activity on the axis discourages DSB hot spot formation. ChIP-chip analysis of Rec8 on fission yeast meiotic chromosomes