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Apc10 and Ste9/Srw1, two regulators of the APC–cyclosome, as well as the CDK inhibitor Rum1 are required for G 1 cell‐cycle arrest in fission yeast
Author(s) -
Kominami Kinichiro,
SethSmith Helena,
Toda Takashi
Publication year - 1998
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/17.18.5388
Subject(s) - biology , cyclin dependent kinase , cell cycle , yeast , fission , microbiology and biotechnology , cdk inhibitor , genetics , cell , physics , quantum mechanics , neutron
Many eukaryotic cells arrest the cell cycle at G 1 phase upon nutrient deprivation. In fission yeast, during nitrogen starvation, cells divide twice and arrest at G 1 . We have isolated a novel type of sterile mutant, which undergoes one additional S phase upon starvation and, as a result, arrests at G 2 . Three loci ( apc10 , ste9/srw1 and rum1 ) were identified. The apc10 mutants, previously unidentified, show, in addition to sterility, temperature‐sensitive growth with defects in chromosome segregation. apc10 + is essential for viability, encodes a conserved protein (a homologue of budding yeast Apc10/Doc1) and is required for ubiquitination and degradation of mitotic B‐type cyclins. Apc10 does not co‐sediment with the 20S APC–cyclosome, a ubiquitin ligase for B‐type cyclins, and in the apc10 mutant the 20S complex is intact, suggesting that it is a novel regulator for this complex. A subpopulation of Apc10 does co‐immunoprecipitate with the anaphase‐promoting complex (APC). A second gene, ste9 + . srw1 + , encodes a member of the fizzy‐related family, also regulators of the APC. Finally, Rum1 is a cyclin‐dependent kinase (CDK) inhibitor which exists only in G 1 . The results suggest that dual downregulation of CDK, one via the APC and the other via the CDK inhibitor, is a universal mechanism that is used to arrest cell cycle progression at G 1 .