Destruction of the securin Pds1p occurs at the onset of anaphase during both meiotic divisions in yeast

Sister chromatid cohesion is established during DNA replication and depends on a multiprotein complex called cohesin. At the onset of anaphase the coh esive structures that hold sisters together must be destroyed to allow segr egation of sisters. In the budding yeast Saccharomyces cerevisiae loss of s ister chromatid cohesion depends on a separating protein (separin) called E sp1. At the metaphase to anaphase transition, separin is activated by prote olysis of its inhibitory subunit (securin) called Pds1. This process is med iated by the anaphase promoting complex and an accessory protein Cdc20. In meiosis a single round of DNA replication is followed by two successive rou nds of segregation. Thus loss of cohesion is spun out over two divisions. B y studying the mechanisms that initiate anaphase in meiotic division we sho w that the yeast securin Pds1p is present in meiotic nuclei and is destroye d at the onset of each meiotic division. We also show that securin destruct ion depends on Cdc20p which accumulates within nuclei around the time of Pd s Ip's disappearance.