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 an SK1 x S88C F1 hybrid strain of Saccharomyces cerevisiae.
Project description:During meiosis, crossover recombination is essential to link homologous chromosomes and drive faithful chromosome segregation. Crossover recombination is non-random across the genome, and centromere-proximal crossovers are associated with an increased risk of aneuploidy, including Trisomy 21 in humans. Here, we identify the conserved Ctf19/CCAN kinetochore sub-complex as a major factor that minimizes potentially deleterious centromere-proximal crossovers in budding yeast. We uncover multi-layered suppression of pericentromeric recombination by the Ctf19 complex, operating across distinct chromosomal distances. The Ctf19 complex prevents meiotic DNA break formation, the initiating event of recombination, proximal to the centromere. The Ctf19 complex independently drives the enrichment of cohesin throughout the broader pericentromere to suppress crossovers, but not DNA breaks. This non-canonical role of the kinetochore in defining a chromosome domain that is refractory to crossovers adds a new layer of functionality by which the kinetochore prevents the incidence of chromosome segregation errors that generate aneuploid gametes. Two samples total: two biological replicate Spo11-oligo maps of S. cerevisiae SK1 mcm21 null mutant
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: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: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 promotes genetic diversification as well as pairing and segregation of homologous chromosomes, but the double-strand breaks (DSBs) that initiate recombination are dangerous lesions that can cause mutation or meiotic failure. How cells control DSBs to balance between beneficial and deleterious outcomes is not well understood. This study tests the hypothesis that DSB control involves a network of intersecting regulatory circuits. We show that DSBs form in greater numbers in Saccharomyces cerevisiae cells lacking ZMM proteins, a suite of recombination-promoting factors traditionally regarded as acting strictly downstream of DSB formation. This counterintuitive result suggests that homologous chromosomes that have successfully engaged one another stop making DSBs, and provides new insight into phenotypes of zmm and other recombination-defective mutants. A genetically distinct pathway ties DSB formation to meiotic progression through the Ndt80 transcription factor. High-resolution genome-wide DSB maps generated by sequencing short oligonucleotides covalently bound to Spo11 (Spo11 oligos) demonstrate that feedback tied to ZMM function contributes in unexpected ways to spatial patterning of the recombination landscape.
Project description:To segregate accurately during meiosis, homologous chromosomes in most species must recombine. Very small chromosomes would risk missegregation if recombination were randomly distributed, so the double-strand breaks (DSBs) that initiate recombination are not haphazard. How this nonrandomness is controlled is not understood. Here we demonstrate that Saccharomyces cerevisiae integrates multiple, temporally distinct pathways to regulate chromosomal binding of pro-DSB factors Rec114 and Mer2, thereby controlling duration of a DSB-competent state. Homologous chromosome engagement regulates Rec114/Mer2 dissociation late in prophase, whereas replication timing and proximity to centromeres or telomeres influence timing and amount of Rec114/Mer2 accumulation early. A distinct early mechanism boosts Rec114/Mer2 binding quickly to high levels specifically on the shortest chromosomes, dependent on chromosome axis proteins and subject to selection pressure to maintain hyperrecombinogenic properties of these chromosomes. Thus, an organism’s karyotype and its attendant risk of meiotic missegregation influence the shape and evolution of its recombination landscape.