Rec25 and Rec27, Novel Linear-Element Components, Link Cohesin to Meiotic DNA Breakage and Recombination

Abstract

Meiosis is a specialized nuclear division by which sexually reproducing diploid organisms generate haploid gametes. Recombination between homologous chromosomes facilitates accurate meiotic chromosome segregation and is initiated by DNA double-strand breaks (DSBs) made by the conserved topoisomerase-like protein Spo11 (Rec12 in fission yeast), but DSBs are not evenly distributed across the genome. In Schizosaccharomyces pombe, proteinaceous structures known as linear elements (LinEs) are formed during meiotic prophase. The meiosis-specific cohesin subunits Rec8 and Rec11 are essential for DSB formation in some regions of the genome, as well as for formation of LinEs or the related synaptonemal complex (SC) in other eukaryotes. Proteins required for DSB formation decorate LinEs, and mutants lacking Rec10, a major component of LinEs, are completely defective for recombination. Although recombination may occur in the context of LinEs, it is not well understood how Rec10 is loaded onto chromosomes. We describe two novel components of LinEs in fission yeast, Rec25 and Rec27. Comparisons of rec25Delta, rec27Delta, and rec10Delta mutants suggest multiple pathways to load Rec10. In the major pathway, Rec10 is loaded, together with Rec25 and Rec27, in a Rec8-dependent manner with subsequent region-specific effects on recombination.

Cohesins and Cohesin-Regulators in Meiosis

“…An example is found in S. pombe, in this organism Rec8 and Rec11, meiosis-specific cohesin subunits, are essential for DSBs only in some regions of the genome (Ellermeier & Smith, 2005). On the other hand the loading of Rec25 and Rec27, two recombination proteins in yeast, depends on the previous incorporation of Rec8 (Davis et al, 2008). This issue could be explained because of Rec8 is required for the normal chromosome compaction during meiotic prophase I (Ding et al, 2006), thus it has been proposed that the regional effect on DSBs production might be related to the meiotic chromosomal organization formed by the cohesins (Davis et al, 2008).…”

“…On the other hand the loading of Rec25 and Rec27, two recombination proteins in yeast, depends on the previous incorporation of Rec8 (Davis et al, 2008). This issue could be explained because of Rec8 is required for the normal chromosome compaction during meiotic prophase I (Ding et al, 2006), thus it has been proposed that the regional effect on DSBs production might be related to the meiotic chromosomal organization formed by the cohesins (Davis et al, 2008). Thus the role of cohesins in meiotic recombination should be at different levels, chromosomal organization, providing the proximity between sister chromatid to ensure a correct repair with an undamaged template and as individual proteins that form complexes with recombination proteins.…”

Functional interactions of Rec24, the fission yeast ortholog of mouse Mei4, with the meiotic recombination–initiation complex

“…LinE formation was analyzed by Rec10 immunostaining of chromosome spreads prepared at different times (3 and 3.5 hours) during prophase in pat1-114 synchronous meiosis. The rec12⌬ mutant was used as a negative control, and the rec8⌬ mutant was used as an additional control because LinE formation is impaired in cohesin mutants (Molnar et al, 1995;Lorenz et al, 2004;Davis et al, 2008). Morphologically similar LinEs were observed with similar frequencies in wild-type, rec24⌬ and rec12⌬ mutants at the two time points analyzed ( Fig.…”

“…The recombination defect in rec25⌬ and rec27⌬ mutants might be explained by the absence of LinE formation in these mutants (Davis et al, 2008). However, formation of LinE occurs in rec12⌬ and previously tested accessory protein mutants (Molnar et al, 2003;Lorenz et al, 2004;Lorenz et al, 2006;Davis et al, 2008).…”

“…However, formation of LinE occurs in rec12⌬ and previously tested accessory protein mutants (Molnar et al, 2003;Lorenz et al, 2004;Lorenz et al, 2006;Davis et al, 2008). Therefore, we addressed whether Rec24 has a role in LinE formation, using the major LinE component Rec10 as a marker (Lorenz et al, 2004).…”