Role of ubiquitin-protein ligase UBR5 in the disassembly of mitotic checkpoint complexes
Sharon Kaisari, Shirly Miniowitz-Shemtov, Danielle Sitry-Shevah, Pnina Shomer, Guennadi Kozlov, Kalle Gehring, Avram Hershko
Abstract
-recognin 5) is associated with the APC/C*MCC complex immunopurified from extracts of nocodazole-arrested HeLa cells. UBR5 binds to mitotic checkpoint proteins BubR1, Bub3, and Cdc20 and promotes their polyubiquitylation in vitro. The dissociation of a Bub3*BubR1 subcomplex of MCC is stimulated by UBR5-dependent ubiquitylation, as suggested by observations that this process in mitotic extracts requires UBR5 and α-β bond hydrolysis of adenosine triphosphate. Furthermore, a system reconstituted from purified recombinant components carries out UBR5- and ubiquitylation-dependent dissociation of Bub3*BubR1. Immunodepletion of UBR5 from mitotic extracts slows down the release of MCC components from APC/C and prolongs the lag period in the recovery of APC/C activity in the exit from mitotic checkpoint arrest. We suggest that UBR5 may be involved in the regulation of the inactivation of the mitotic checkpoint.