Abstract
Meiosis ensures genetic diversification of gametes and sexual reproduction. For successful meiosis, multiple events such as DNA replication, recombination, and chromosome segregation must occur coordinately in a strict regulated order. We investigated the meiotic roles of Cdc7 kinase in the initiation of meiotic recombination, namely, DNA double-strand breaks (DSBs) mediated by Spo11 and other coactivating proteins. Genetic analysis using bob1-1 cdc7Delta reveals that Cdc7 is essential for meiotic DSBs and meiosis I progression. We also demonstrate that the N-terminal region of Mer2, a Spo11 ancillary protein required for DSB formation and phosphorylated by cyclin-dependent kinase (CDK), contains two types of Cdc7-dependent phosphorylation sites near the CDK site (Ser30): One (Ser29) is essential for meiotic DSB formation, and the others exhibit a cumulative effect to facilitate DSB formation. Importantly, mutations on these sites confer severe defects in DSB formation even when the CDK phosphorylation is present at Ser30. Diploids of cdc7Delta display defects in the chromatin binding of not only Spo11 but also Rec114 and Mei4, other meiotic coactivators that may assist Spo11 binding to DSB hot spots. We thus propose that Cdc7, in concert with CDK, regulates Spo11 loading to DSB sites via Mer2 phosphorylation.
Highlights
The meiotic cell division comprises one round of DNA replication and activated homologous recombination followed by two consecutive nuclear divisions, and thereby converts a diploid cell to a haploid gamete with increased genetic diversity
MALDI-TOF mass-spectrometric (TOF-MS) analysis and alanine substitution analysis enabled us to identify in vivo bona fide phosphorylation sites in the N-terminal region of Mer2 and led us to conclude that the phosphorylation dependent on Cdc7 is vital for double-strand breaks (DSBs) formation via the chromatin loading of Spo11, which may be facilitated by Rec114, a component of the pre-DSB complex
We showed that Cdc7 plays an essential role in the regulation of meiotic DSB formation via phosphorylation of the N-terminal region of Mer2
Summary
The meiotic cell division comprises one round of DNA replication and activated homologous recombination followed by two consecutive nuclear divisions, and thereby converts a diploid cell to a haploid gamete with increased genetic diversity. Clb5–Clb6–cyclin-dependent kinase (CDK) activity has crucial roles in triggering both replication initiation and the activation of Spo in budding yeast meiosis (Dirick et al 1998; Stuart and Wittenberg 1998; Smith et al 2001; Henderson et al 2006). These studies suggest that cellular regulation coordinates DNA replication and DSB formation. We further demonstrate that Cdc is pivotal for the loading of Rec
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