Project description:Meiotic recombination between homologous chromosomes initiates via programmed DNA double-strand breaks (DSBs), generated by complexes comprising Spo11 transesterase plus accessory proteins. DSBs arise concomitantly with the development of axial chromosome structures, where the coalescence of axis sites produces linear arrays of chromatin loops. Recombining DNA sequences map to loops, but are ultimately tethered to the underlying axis. How and when such tethering occurs is currently unclear. Using ChIPchip in yeast, we show that Spo11-accessory proteins Rec114, Mer2 and Mei4 stably interact with chromosome axis sequences, upon phosphorylation of Mer2 by S-phase Cdk. This axis tethering requires meiotic axis components (Red1/Hop1) and is modulated in a domain-specific fashion by cohesin. Loss of Rec114, Mer2 and Mei4 binding correlates with loss of DSBs. Our results strongly suggest that hotspot sequences become tethered to axis sites by the DSB machinery prior to DSB formation.
Project description:In most organisms, meiotic recombination begins with programmed DNA double strand break (DSB) formation by Spo11. Here, we present evidence that Tel1/Mec1, the budding yeast ATM/ATR, regulate DSB formation by phosphorylating Rec114, an essential Spo11-accessory protein. Analyses of a non-phosphorylatable- or phosphomimetic- alleles of rec114 revealed that DSB-dependent phosphorylation of Rec114 limited its association with DSB-hotspots resulting in reduction in DSB formation. Also observed were the impact of Rec114 phosphorylation on its homolog synapsis-associated removal from chromosomes and NDT80-dependent turnover. Specifically, we found that the synapsis- and NDT80-dependent Rec114 downregulation occurred later in the rec114 mutant with a reduced Spo11-catalysis, but earlier in the other with an enhanced catalysis, strongly implicating the existence of a feedback mechanism coupling the extent of Spo11-catalysis to Rec114 activity. Taken together, these observations suggest that three different mechanisms of down regulating Rec114 contribute to meiotic DSB homeostasis, a feedback mechanism to maintain the number of meiotic DSBs at the developmentally programmed level. 6 genome wide ChIPchip sets: 3 for meiotic DSB formation (Spo11-ChIP) and 3 for protein-DNA association (Rec114-ChIP), each for wild type and two mutants during meiosis (corresponding to the main Figure 3, as well as to Figures S3, S4, S5).
Project description:During mouse meiosis, DNA double-strand breaks (DSBs) are initiated by SPO11 at recombination hotspots (HSs), activated by PRDM9. Although activated HSs are marked by H3K4me3 and H3K36me3 histone modifications at open chromatin, most of the DSB-initiating and repair proteins are associated with the chromosome axis. This study addresses the mechanistic importance of the axis-associated cohesin proteins in DSB formation. We demonstrate that interactions between PRDM9 and the meiotic axis proteins STAG3 and REC8 are essential for efficient DSB formation. The absence of STAG3 or REC8 leads to inefficient meiotic DSB formation at HSs. STAG3 is critical for DSB formation, even at PRDM9-independent DSB-sites. Also, STAG3 and REC8 facilitate recruitment of the DSB-promoting proteins HORMAD1, IHO1 and MEI4 required for SPO11 activity. Together, these results support an evolutionarily conserved model in which axis-associated cohesin complexes recruit recombination-initiating proteins to DSB sites to promote meiotic recombination initiation.
Project description:Meiotic recombination starts with the formation of DNA double-strand breaks (DSBs) made by Spo11. In Saccharomyces cerevisiae, the nonrandom distribution of meiotic DSBs along the genome can be attributed to the combined influence of multiple factors on Spo11 cleavage. One factor is higher-order chromatin structure, particularly the loop-axis organization of meiotic chromosomes. Axial element proteins Red1 and Hop1 provide the basis for meiotic loop-axis organization and are implicated in diverse aspects of meiotic recombination. Mek1 is a meiotic-specific kinase associated with Red1 and Hop1. Red1, Hop1, and Mek1 are required for normal DSB levels, but their effects on the DSB distribution has not been examined, and exactly how these proteins influence DSB levels and distribution is unknown. Here, we examined the contributions of Red1, Hop1, and Mek1 to the DSB distribution by deep sequencing and mapping Spo11-associated oligonucleotides from red1, hop1, and mek1 mutant strains, thereby generating genome-wide meiotic DSB maps.
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
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-seq analyses of Rec8, Spo11, and Gal4BD-Spo11 on budding yeast meiotic chromosomes M-bM-^@M-" Distribution of Rec8 in wt and Gal4BD-Spo11-expressing cells at 4h after meiotic induction M-bM-^@M-" Distribution of Spo11 at 3h, 4h, and 5h after meiotic induction M-bM-^@M-" Distribution of Gal4BD-Spo11 at 0h after meiotic induction
Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use Spo11-oligonucleotide complexes to map the distribution of meiotic DSBs in a spo11 mutant strain of Saccharomyces cerevisiae.
Project description:In most organisms, meiotic recombination begins with programmed DNA double strand break (DSB) formation by Spo11. Here, we present evidence that Tel1/Mec1, the budding yeast ATM/ATR, regulate DSB formation by phosphorylating Rec114, an essential Spo11-accessory protein. Analyses of a non-phosphorylatable- or phosphomimetic- alleles of rec114 revealed that DSB-dependent phosphorylation of Rec114 limited its association with DSB-hotspots resulting in reduction in DSB formation. Also observed were the impact of Rec114 phosphorylation on its homolog synapsis-associated removal from chromosomes and NDT80-dependent turnover. Specifically, we found that the synapsis- and NDT80-dependent Rec114 downregulation occurred later in the rec114 mutant with a reduced Spo11-catalysis, but earlier in the other with an enhanced catalysis, strongly implicating the existence of a feedback mechanism coupling the extent of Spo11-catalysis to Rec114 activity. Taken together, these observations suggest that three different mechanisms of down regulating Rec114 contribute to meiotic DSB homeostasis, a feedback mechanism to maintain the number of meiotic DSBs at the developmentally programmed level.
Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use S1Seq mapping to map the distribution of meiotic DSBs in spo11 mutant strains of Saccharomyces cerevisiae.
Project description:The Spo11-generated double-strand breaks (DSBs) that initiate meiotic recombination are non-randomly distributed across the genome. Here, we use Spo11-oligonucleotide complexes, a byproduct of DSB formation, to map the distribution of meiotic DSBs in pch2 and sir2 mutant strains of Saccharomyces cerevisiae.