Item

Abstract

During the mitotic cell cycle, DNA replication and chromosome segregation strictly alternate in order to maintain a constant ploidy. Meiosis, on the other hand, is a special form of cell division that is characterized by a single round of DNA replication followed by two consecutive nuclear divisions. In order to understand how these two divisions are implemented, mutants that undergo a single meiotic division are of special interest. The spo13 mutant undergoes a single nuclear division, during which it segregates a mixture of homologous chromosomes and sister chromatids. The Spo13 protein has been implicated in both the monopolar attachment of sister chromatids at meiosis I and the protection of centromeric cohesin until the second meiotic division. However, weshowedthat SPO13deletion cells were delayed in metaphase I by the spindle assembly checkpoint (SAC). In this work, we re-investigated the involvement of Spo13 for monopolar attachment and centromeric cohesin protection while taking into account the delay at metaphase I. We found that, while Spo13 is directly required for monopolar attachment, it is not directly involved in centromeric cohesin protection. Indeed, the premature loss of centromeric cohesin in spo13∆ cells is due to their delay in metaphase I, and shortening this delay restores centromeric cohesin protection. Furthermore, we found that Spo13, together with the polo-like kinase, prevents the activation of APC/CAma1 in meiosis I by phosphorylating the B-type cyclin, Clb1. Spo13 is therefore required for coordinating the APC/C activity with meiosis I-specific events.