RESUMO
Cohesin is a conserved multisubunit protein complex that participates in chromosome segregation, DNA damage repair, chromatin regulation, and synaptonemal complex (SC) formation. Yeast, but not mice, depleted of the cohesin subunit Rec8 are defective in the formation of the axial elements (AEs) of the SC, suggesting that, in mammals, this function is not conserved. In this paper, we show that spermatocytes from mice lacking the two meiosis-specific cohesin subunits RAD21L and REC8 were unable to initiate RAD51- but not DMC1-mediated double-strand break repair, were not able to assemble their AEs, and arrested as early as the leptotene stage of prophase I, demonstrating that cohesin plays an essential role in AE assembly that is conserved from yeast to mammals.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Meiose , Proteínas Nucleares/metabolismo , Fosfoproteínas/metabolismo , Animais , Quebras de DNA de Cadeia Dupla , Proteínas de Ligação a DNA , Masculino , Camundongos , Camundongos Knockout , Proteínas Nucleares/deficiência , Fosfoproteínas/deficiência , Ligação Proteica , CoesinasRESUMO
The cohesin complex is a ring-shaped proteinaceous structure that entraps the two sister chromatids after replication until the onset of anaphase when the ring is opened by proteolytic cleavage of its α-kleisin subunit (RAD21 at mitosis and REC8 at meiosis) by separase. RAD21L is a recently identified α-kleisin that is present from fish to mammals and biochemically interacts with the cohesin subunits SMC1, SMC3 and STAG3. RAD21L localizes along the axial elements of the synaptonemal complex of mouse meiocytes. However, its existence as a bona fide cohesin and its functional role awaits in vivo validation. Here, we show that male mice lacking RAD21L are defective in full synapsis of homologous chromosomes at meiotic prophase I, which provokes an arrest at zygotene and leads to total azoospermia and consequently infertility. In contrast, RAD21L-deficient females are fertile but develop an age-dependent sterility. Thus, our results provide in vivo evidence that RAD21L is essential for male fertility and in females for the maintenance of fertility during natural aging.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Meiose , Fatores Etários , Animais , Proteínas Cromossômicas não Histona/deficiência , Cromossomos/metabolismo , Feminino , Histocitoquímica , Infertilidade , Masculino , Camundongos , Camundongos Knockout , Ovário/patologia , Subunidades Proteicas/metabolismo , Fatores Sexuais , Testículo/patologiaRESUMO
Meiosis is a fundamental process that generates new combinations between maternal and paternal genomes and haploid gametes from diploid progenitors. Many of the meiosis-specific events stem from the behavior of the cohesin complex (CC), a proteinaceous ring structure that entraps sister chromatids until the onset of anaphase. CCs ensure chromosome segregation, participate in DNA repair, regulate gene expression, and also contribute to synaptonemal complex (SC) formation at meiosis by keeping long-range distant DNA interactions through its conserved structure. Studies from yeast to humans have led to the assumption that Scc1/RAD21 is the α-kleisin that closes the tripartite CC that entraps two DNA molecules in mitosis, while its paralog REC8 is essential for meiosis. Here we describe the identification of RAD21L, a novel mammalian CC subunit with homology to the RAD21/REC8 α-kleisin subfamily, which is expressed in mouse testis. RAD21L interacts with other cohesin subunits such as SMC1α, SMC1b, SMC3 and with the meiosis-specific STAG3 protein. Thus, our results demonstrate the existence of a new meiotic-specific CC constituted by this α-kleisin and expand the view of REC8 as the only specific meiotic α-kleisin.
Assuntos
Proteínas de Ciclo Celular/química , Proteínas Cromossômicas não Histona/química , Proteínas de Ligação a DNA/química , Meiose , Proteínas Nucleares/química , Fosfoproteínas/química , Sequência de Aminoácidos , Animais , Proteínas de Ciclo Celular/genética , Proteínas Cromossômicas não Histona/genética , Sequência Conservada , Proteínas de Ligação a DNA/genética , Células HEK293 , Humanos , Masculino , Meiose/genética , Camundongos , Dados de Sequência Molecular , Proteínas Nucleares/genética , Fosfoproteínas/genética , Estrutura Terciária de Proteína/genética , Homologia de Sequência de Aminoácidos , Testículo/química , Testículo/fisiologia , CoesinasRESUMO
Shugoshin-2 (SGOL2) is one of the two mammalian orthologs of the Shugoshin/Mei-S322 family of proteins that regulate sister chromatid cohesion by protecting the integrity of the multiprotein cohesin complexes. This protective system is essential for faithful chromosome segregation during mitosis and meiosis, which is the physical basis of Mendelian inheritance. Regardless of its evolutionary conservation from yeast to mammals, little is known about the in vivo relevance and specific role that SGOL2 plays in mammals. Here we show that disruption of the gene encoding mouse SGOL2 does not cause any alteration in sister chromatid cohesion in embryonic cultured fibroblasts and adult somatic tissues. Moreover, mutant mice develop normally and survive to adulthood without any apparent alteration. However, both male and female Sgol2-deficient mice are infertile. We demonstrate that SGOL2 is necessary for protecting centromeric cohesion during mammalian meiosis I. In vivo, the loss of SGOL2 promotes a premature release of the meiosis-specific REC8 cohesin complexes from anaphase I centromeres. This molecular alteration is manifested cytologically by the complete loss of centromere cohesion at metaphase II leading to single chromatids and physiologically with the formation of aneuploid gametes that give rise to infertility.
