Sic1, a protein, is a stoichiometric inhibitor [1] of Cdk1-Clb (B-type cyclins) complexes in the budding yeast Saccharomyces cerevisiae. Because B-type cyclin-Cdk1 complexes are the drivers of S-phase initiation, Sic1 prevents premature S-phase entry. [2]

2011年2月7日 · SIC1 encodes a cyclin-dependent kinase inhibitor (CKI) that regulates the cell cycle at the G1 to S transition by inhibiting the activity of the cyclin-dependent kinase (CDK) Cdc28p (5 and reviewed in 13 and 14). Sic1p is a potent inhibitor of the cyclin-CDK complexes containing a B-type (Clb) but not a G1 (Cln) cyclin (3, 18).

2017年10月13日 · Traversal from G1 to S-phase in cycling cells of budding yeast is dependent on the destruction of the S-phase cyclin/CDK inhibitor SIC1. Genetic data suggest that SIC1 proteolysis is mediated by the ubiquitin pathway and requires the action of CDC34, CDC4, CDC53, SKP1, and CLN/CDC28.

In Saccharomyces cerevisiae, Sic1, an inhibitor of Cdk (cyclin-dependent kinase), blocks the activity of S-Cdk1 (Cdk1/Clb5,6) kinase that is required for DNA replication. Deletion of Sic1 causes premature DNA replication from fewer origins, extension of the S phase and inefficient separation of sister chromatids during anaphase.

2011年2月7日 · Sic1 is responsible for repressing the activity of Clb cyclin-containing Cdc28 complexes until the cell is prepared to leave G1 and commit to progression through the cell cycle [29]. Sic1 degradation has been previously demonstrated to be predominantly dependent on the G1 Cln–Cdc28 kinases [30,31].

The cyclin-dependent kinase inhibitor Sic1 is an intrinsically disordered protein (IDP) involved in cell-cycle regulation in the yeast Saccharomyces cerevisiae. Notwithstanding many studies on its biological function, structural characterization has been …

2025年1月4日 · We analyse oscillations of B-type (Clb) cyclins, focusing on the role of their inhibitor Sic1. Individually weak dispersed Sic1 phospho sites engage Cdc4 in a dynamic equilibrium. The multisite nature of this interaction confers cooperative dependence on kinase activity for Sic1 recognition & ubiquitination at equilibrium.

In the yeast Saccharomyces cerevisiae, Sic1, an inhibitor of Clb-Cdc28 kinases, must be phosphorylated and degraded in G 1 for cells to initiate DNA replication, and Cln-Cdc28 kinase appears to be primarily responsible for phosphorylation of Sic1.

Sic1 is an intrinsically disordered protein and achieves its inhibitory function by cooperative binding, where different structural regions stretch on the Cdk1/Clb surface. Moreover, Sic1 promotes S phase entry, facilitating Cdk1/Clb5 nuclear transport, and therefore revealing a double function of inhibitor/activator that rationalizes a ...

2016年10月3日 · Genetic data suggest that SIC1 proteolysis is mediated by the ubiquitin pathway and requires the action of CDC34, CDC4, CDC53, SKP1, and CLN/CDC28. As a first step in defining the functions of the corresponding gene products, we have reconstituted SIC1 multiubiquitination in DEAE-fractionated yeast extract.