Phosphorylation of Sic1p by G1 Cdk required for its degradation and entry into S phase
G1 cyclin-dependent kinase (Cdk)-triggered degradation of the S-phase Cdk inhibitor Sic1p has been implicated in the transition from G1 to S phase in the cell cycle of budding yeast. A multidimensional electrospray mass spectrometry technique was used to map G1 Cdk phosphorylation sites in Sic1p bot...
Saved in:
Published in | Science (American Association for the Advancement of Science) Vol. 278; no. 5337; pp. 455 - 460 |
---|---|
Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
American Association for the Advancement of Science
17.10.1997
The American Association for the Advancement of Science |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | G1 cyclin-dependent kinase (Cdk)-triggered degradation of the S-phase Cdk inhibitor Sic1p has been implicated in the transition from G1 to S phase in the cell cycle of budding yeast. A multidimensional electrospray mass spectrometry technique was used to map G1 Cdk phosphorylation sites in Sic1p both in vitro and in vivo. A Sic1p mutant lacking three Cdk phosphorylation sites did not serve as a substrate for Cdc34p-dependent ubiquitination in vitro, was stable in vivo, and blocked DNA replication. Moreover, purified phosphoSic1p was ubiquitinated in cyclin-depleted G1 extract, indicating that a primary function of G1 cyclins is to tag Sic1p for destruction. These data suggest a molecular model of how phosphorylation and proteolysis cooperate to bring about the G1/S transition in budding yeast. |
---|---|
Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0036-8075 1095-9203 |
DOI: | 10.1126/science.278.5337.455 |