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 to map the distribution of meiotic DSBs in a spo11 mutant strain 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.
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 meiosis, genetic recombination is initiated by the formation of many DNA double-strand breaks (DSBs) catalysed by the evolutionarily conserved topoisomerase-like enzyme, Spo11, in preferred genomic sites known as hotspots. DSB formation activates the Tel1/ATM DNA damage responsive (DDR) kinase, locally inhibiting Spo11 activity in adjacent hotspots via a process known as DSB interference. Intriguingly, in S. cerevisiae, over short genomic distances (<15 kb), Spo11 activity displays characteristics of concerted activity or clustering, wherein the frequency of DSB formation in adjacent hotspots is greater than expected by chance. We have proposed that clustering is caused by a limited number of sub-chromosomal domains becoming primed for DSB formation. Here, we provide evidence that DSB clustering is abolished when meiotic prophase timing is extended via deletion of the NDT80 transcription factor. We propose that extension of meiotic prophase enables most cells, and therefore most chromosomal domains within them, to reach an equilibrium state of similar Spo11-DSB potential, reducing the impact that priming has on estimates of coincident DSB formation. Consistent with this view, when Tel1 is absent but Ndt80 is present and thus cells are able to rapidly exit meiotic prophase, genome-wide maps of Spo11-DSB formation are skewed towards pericentromeric regions and regions that load pro-DSB factors early—revealing regions of preferential priming—but this effect is abolished when NDT80 is deleted. Our work highlights how the stochastic nature of Spo11-DSB formation in individual cells within the limited temporal window of meiotic prophase can cause localised DSB clustering—a phenomenon that is exacerbated in tel1∆ cells due to the dual roles that Tel1 has in DSB interference and meiotic prophase checkpoint control.
Project description:The nonrandom distribution of meiotic recombination shapes patterns of inheritance and genome evolution, but chromosomal features governing this distribution are poorly understood. Formation of the DNA double-strand breaks (DSBs) that initiate recombination results in accumulation of Spo11 protein covalently bound to small DNA fragments. We show here that sequencing these fragments provides a genome-wide DSB map of unprecedented resolution and sensitivity. We use this map to explore the influence of large-scale chromosome structures, chromatin, transcription factors, and local sequence composition on DSB distributions. Our analysis supports the view that the recombination terrain is molded by combinatorial and hierarchical interaction of factors that work on widely different size scales. Mechanistic aspects of DSB formation and early processing steps are also uncovered. This map illuminates the occurrence of DSBs in repetitive DNA elements, repair of which can lead to chromosomal rearrangements. We discuss implications for evolutionary dynamics of recombination hotspots. We deep sequenced 4 samples of Spo11 oligos on Roche 454 platform. Three samples are technical replicates of Spo11 oligo products prepared from one meiotic culture and the fourth sample was prepared from an independent culture.
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:DNA double-strand breaks (DSBs) initiate meiotic recombination. Past DSB-mapping studies have used rad50S or sae2? mutants, which are defective in break processing, to accumulate DSBs, and report large (= 50 kb) “DSB-hot” regions that are separated by “DSB-cold” domains of similar size. Substantial recombination occurs in some DSB-cold regions, suggesting that DSB patterns are not normal in rad50S or sae2? mutants. We therefore developed novel methods that detect DSBs using ssDNA enrichment and microarray hybridization, and that use background-based normalization to allow cross-comparison between array datasets, to map genome-wide the DSBs that accumulate in processing-capable, repair-defective dmc1î and dmc1î rad51î mutants. DSBs were observed at known hotspots, but also in most previously-identified “DSB-cold” regions, including near centromeres and telomeres. While about 40% of the genome is DSB-cold in rad50S mutants, analysis of meiotic ssDNA from dmc1? shows that most of these regions have significant DSB activity. Thus, DSBs are distributed much more uniformly than was previously believed. Southern-blot assays of DSBs in selected regions in dmc1?, rad50S and wild-type cells confirm these findings. Comparisons of DSB signals in dmc1, dmc1 rad51, and dmc1 spo11 mutant strains identify Dmc1 as the primary strand transfer activity genome-wide, and Spo11-induced lesions as initiating all meiotic recombination. Keywords: DSB mapping, ChIP-chip, single strand DNA , BND cellulose We use two different strategies to map the genome-wide distribution of meiotic DSBs in the yeast Saccharomyces cerevisiae. The first is a chromatin immunoprecipitation (ChIP) based approach that targets the Spo11p protein, which remains covalently attached to DSB ends in the rad50S mutant background. The second approach involves BND cellulose enrichment of the single strand DNA (ssDNA) recombination intermediate formed by end-resection at DSB sites following Spo11p removal. We use dmc1 and dmc1 rad51 mutants that accumulates meiotic single strand DNA intermediates