ANAPHASE INITIATION IN SACCHAROMYCES-CEREVISIAE IS CONTROLLED BY THE APC-DEPENDENT DEGRADATION OF THE ANAPHASE INHIBITOR PDS1P

Anaphase initiation has been postulated to be controlled through the u biquitin-dependent proteolysis of an unknown inhibitor. This process i nvolves the anaphase promoting complex (APC), a specific ubiquitin lig ase that has been shown to be involved in mitotic cyclin degradation. Previous studies demonstrated that in Saccharomyces cerevisiae, Pds1 p rotein is an anaphase inhibitor and suggested that it may be an APC ta rget. Here we show that in yeast cells and in mitotic Xenopus extracts Pds1p is degraded in an APC-dependent manner. In addition, Pds1p is d irectly ubiquitinated by the Xenopus APC. In budding yeast Pds1p is de graded at the time of anaphase initiation and nondegradable derivative s of Pds1p inhibit the onset of anaphase. We conclude that Pds1p is an anaphase inhibitor whose APC-dependent degradation is required for th e initiation of anaphase.