RESUMO
Crossover formation is essential for proper segregation of homologous chromosomes during meiosis. Here, we show that Caenorhabditis elegans cyclin-dependent kinase 2 (CDK-2) partners with cyclin-like protein COSA-1 to promote crossover formation by promoting conversion of meiotic double-strand breaks into crossoverspecific recombination intermediates. Further, we identify MutSγ component MSH-5 as a CDK-2 phosphorylation target. MSH-5 has a disordered C-terminal tail that contains 13 potential CDK phosphosites and is required to concentrate crossoverpromoting proteins at recombination sites. Phosphorylation of the MSH-5 tail appears dispensable in a wild-type background, but when MutSγ activity is partially compromised, crossover formation and retention of COSA-1 at recombination sites are exquisitely sensitive to phosphosite loss. Our data support a model in which robustness of crossover designation reflects a positive feedback mechanism involving CDK-2mediated phosphorylation and scaffold-like properties of the MSH5 C-terminal tail, features that combine to promote full recruitment and activity of crossoverpromoting complexes.
Assuntos
Proteínas de Caenorhabditis elegans , Quinase 2 Dependente de Ciclina , Proteínas de Ligação a DNA , Meiose , Complexo Sinaptonêmico , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Segregação de Cromossomos , Troca Genética , Quinase 2 Dependente de Ciclina/genética , Quinase 2 Dependente de Ciclina/metabolismo , Proteínas de Ligação a DNA/metabolismo , Fosforilação , Complexo Sinaptonêmico/genética , Complexo Sinaptonêmico/metabolismoRESUMO
RAD-54.L is required for the repair of meiotic double-strand DNA breaks (DSBs), playing an essential role in promoting removal of recombinase RAD-51 and normal completion of meiotic recombination. Failure to complete meiotic DSB repair leads to 100% lethality of embryos produced by rad-54.L null mutant mothers. Here we report a new partial loss of function allele, rad-54.L(me139) , that may prove useful for investigating meiotic mechanisms by providing a sensitized genetic background that reduces but does not eliminate the essential functions of RAD-54.L.
RESUMO
Meiotic crossover formation requires the activity of multiple pro-crossover factors, including the MutSγ complex and the cyclin-related protein COSA-1, that become concentrated together at the sites of crossover recombination intermediates. Here we show that a transgene insertion expressing GFP::COSA-1 can suppress the crossover deficit caused by a partial reduction in MutSγ function. Our data, combined with previous findings, support a model in which COSA-1 promotes crossover formation, at least in part, through positive regulation of MutSγ function.