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APC ste9/srw1 promotes degradation of mitotic cyclins in G 1 and is inhibited by cdc2 phosphorylation
Author(s) -
Blanco Miguel A.,
SánchezDíaz Alberto,
de Prada José M.,
Moreno Sergio
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.15.3945
Subject(s) - biology , cyclin dependent kinase 1 , mitosis , phosphorylation , cyclin , microbiology and biotechnology , degradation (telecommunications) , biochemistry , cell cycle , genetics , gene , telecommunications , computer science
Fission yeast ste9/srw1 is a WD‐repeat protein highly homologous to budding yeast Hct1/Cdh1 and Drosophila Fizzy‐related that are involved in activating APC/C (anaphase‐promoting complex/cyclosome). We show that APC ste9/srw1 specifically promotes the degradation of mitotic cyclins cdc13 and cig1 but not the S‐phase cyclin cig2. APC ste9/srw1 is not necessary for the proteolysis of cdc13 and cig1 that occurs at the metaphase–anaphase transition but it is absolutely required for their degradation in G 1 . Therefore, we propose that the main role of APC ste9/srw1 is to promote degradation of mitotic cyclins when cells need to delay or arrest the cell cycle in G 1 . We also show that ste9/srw1 is negatively regulated by cdc2‐dependent protein phosphorylation. In G 1 , when cdc2–cyclin kinase activity is low, unphosphorylated ste9/srw1 interacts with APC/C. In the rest of the cell cycle, phosphorylation of ste9/srw1 by cdc2–cyclin complexes both triggers proteolysis of ste9/srw1 and causes its dissociation from the APC/C. This mechanism provides a molecular switch to prevent inactivation of cdc2 in G 2 and early mitosis and to allow its inactivation in G 1 .