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Genetics

Title:		Degradation of the Mitotic Cyclin Clb3 Is not Required for Mitotic Exit but Is Necessary for G1 Cyclin Control of the Succeeding Cell Cycle
Author(s):		Pecani K; Cross FR;
Address:		"The Rockefeller University, New York, New York 10065. The Rockefeller University, New York, New York 10065 fcross@rockefeller.edu"
Journal Title:		Genetics
Year:		2016
Volume:		20161028
Issue:		4
Page Number:		1479 - 1494
DOI:		10.1534/genetics.116.194837
ISSN/ISBN:		1943-2631 (Electronic) 0016-6731 (Print) 0016-6731 (Linking)
Abstract:		"B-type cyclins promote mitotic entry and inhibit mitotic exit. In Saccharomyces cerevisiae, four B-type cyclins, Clb1-4, carry out essential mitotic roles, with substantial but incomplete overlap of function among them. Previous work in many organisms has indicated that B-type cyclin-dependent inhibition of mitotic exit imposes a requirement for mitotic destruction of B-type cyclins. For instance, precise genomic removal of the Clb2 destruction box (D box) prevents mitotic proteolysis of Clb2, and blocks mitotic exit. Here, we show that, despite significant functional overlap between Clb2 and Clb3, D-box-dependent Clb3 proteolysis is completely dispensable for mitotic exit. Removal of the Clb3 D box results in abundant Clb3 protein and associated kinase throughout the cell cycle, but mitotic exit occurs with close to normal timing. Clb3 degradation is required for pre-Start G(1) control in the succeeding cell cycle. Deleting the CLB3 D box essentially eliminates all time delay before cell cycle Start following division, even in very small newborn cells. CLB3?Osdb cells show no cell cycle arrest response to mating pheromone, and CLB3?Osdb completely bypasses the requirement for CLN G(1) cyclins, even in the absence of the early expressed B-type cyclins CLB5,6 Thus, regulated mitotic proteolysis of Clb3 is specifically required to make passage of Start in the succeeding cell cycle 'memoryless'-dependent on conditions within that cycle, and independent of events such as B-type cyclin accumulation that occurred in the preceding cycle"
Keywords:		Cyclin B/genetics/*metabolism Mitosis/*genetics *Proteolysis Saccharomyces cerevisiae/cytology/*genetics Saccharomyces cerevisiae Proteins/genetics/*metabolism Clb3 G1 cyclin control Start destruction box mitotic exit;
Notes:		"MedlinePecani, Kresti Cross, Frederick R eng R01 GM078153/GM/NIGMS NIH HHS/ 2016/10/30 Genetics. 2016 Dec; 204(4):1479-1494. doi: 10.1534/genetics.116.194837. Epub 2016 Oct 28"