| Popis: |
Meiosis is a special form of cell division by which sexually reproducing diploid organisms generate haploid gametes. Recombination between homologous chromosomes is a key meiotic event that generates genetic diversity and facilitates accurate segregation of chromosomes [1]. Meiotic recombination is initiated by DNA double-strand breaks (DSBs) made by the conserved topoisomerase-like protein Spo11 (Rec12 in fission yeast) [2–4]. DSBs are not evenly distributed across the genome – there are hot and cold regions in the eukaryotes studied [5]. In Schizosaccharomyces pombe the meiosis-specific cohesin subunits Rec8 and Rec11 are essential for DSB formation in some but not other regions of the genome [6], and for formation of linear elements (LinEs), or the related synaptonemal complex (SC) in other eukaryotes [7–11]. Proteins required for DSB formation decorate LinEs [12], and mutants lacking Rec10, a major component of LinEs, are completely defective for meiotic recombination [6, 10]. Recombination may occur in the context of LinEs, but it is not well understood how Rec10 is loaded onto chromosomes to form LinEs. We describe two novel components of LinEs in fission yeast, Rec25 and Rec27. Comparisons of rec10Δ, rec25Δ, and rec27Δ mutants reveal multiple pathways to load Rec10 onto chromosomes. In the major pathway Rec10 is loaded as part of a complex with Rec25 and Rec27 in a Rec8-dependent manner with subsequent region-specific effects on DSB formation and recombination. |
