The Saccharomyces cerevisiae MUM2 gene interacts with the DNA replication machinery and is required for meiotic levels of double strand breaks

The Saccharomyces cerevisiae MUM2 gene is essential for meiotic, but not mi totic, DNA replication and thus sporulation. Genetic interactions between M UM2 and a component of the origin recognition complex and polymerase alpha -primase suggest that MUM2 influences the function of the DNA replication m achinery. Early meiotic gene expression is induced to a much greater extent in mum2 cells than in meiotic cells treated with the DNA. synthesis inhibi tor hydroxyurea. This result indicates that the mum2 meiotic arrest is down stream of the arrest induced by hydroxyurea and suggests that DNA synthesis is initiated in the mutant. Genetic analyses indicate that the recombinati on that occurs in mum2 mutants is dependent on the normal recombination mac hinery and on synaptonemal complex components and therefore is not a conseq uence of lesions created by incompletely replicated DNA. Both meiotic ectop ic and allelic recombination are similarly reduced in the mum2 mutant, and the levels are consistent with the levels of meiosis-specific DSBs that are generated. Cytological analyses of mum2 mutants show that chromosome pairi ng and synapsis occur, although at reduced levels compared to wild type. Gi ven the near-wild-type levels of meiotic gene expression, pairing, and syna psis, we suggest that the reduction in DNA replication is directly responsi ble for the reduced level of DSBs and meiotic recombination.