CDK Pho85 targets CDK inhibitor Sic1 to relieve yeast G1 checkpoint arrest after DNA damage

Robert Wysocki, Ali Javaheri, Kolbrun Kristjansdottir, Fei Sha, Stephen J. Kron

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

In budding yeast, DNA damage in G1 activates a Rad9-dependent checkpoint that targets the cyclin-dependent kinase (CDK) Cdc28 to delay G1 exit. After a transient arrest, cells may enter S phase before completing DNA repair. We used genetic analysis to identify the stress-responsive CDK Pho85, the cyclin Pho80 and the targeted transcription factors Pho4 and Swi5 as determinants of G1 checkpoint adaptation. Consistent with opposing roles for the Cdc28 inhibitor Sic1 in blocking G1 exit and Pho85 in targeting Sic1 for proteolysis, mutation of Sic1 curtails G1 checkpoint delay, whereas Pho85 inhibition after DNA damage promotes Sic1 stability. G1 checkpoint delay in mutants lacking both Sic1 and Pho4 is independent of Pho85 activity. These data establish a G1 checkpoint adaptation pathway where Pho85 mediates Pho4 downregulation and Sic1 degradation to release Cdc28 activity and promote onset of S phase.

Original languageEnglish
Pages (from-to)908-914
Number of pages7
JournalNature Structural and Molecular Biology
Volume13
Issue number10
DOIs
StatePublished - Oct 1 2006
Externally publishedYes

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