Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A random population of temperature-sensitive mutants was screened by assaying for defects in DNA synthesis in a permeabilized yeast DNA replication system. Twenty mutants defective in in vitro DNA synthesis have been isolated. In this paper we describe eight of these mutants. Seven of them fall into three complementation groups--cdc2, cdc8, and cdc16--involved in the control of the cell-division cycle. Because synthesis in vitro represents propagation of replication forks active in vivo at the time of permeabilization, our finding that cdc2 and cdc16 mutants can incorporate dTMP into DNA in such permeabilized cells at 23 degrees C but not at 37 degrees C supports the conclusion that these two mutations directly affect DNA synthesis at replication forks. Such an involvement was previously suggested by in vivo analysis for CDC2 but was less clear for CDC16. Finally, the usefulness of our screening procedure is demonstrated by the isolation of replication mutants in previously undescribed complementation groups. One strain shows a serious defect in in vivo DNA synthesis but normal RNA synthesis.
 ...
PMID:Isolation of yeast DNA replication mutants in permeabilized cells. 635 28

The abundance of B-type cyclin-CDK complexes is determined by regulated synthesis and degradation of cyclin subunits. Cyclin proteolysis is required for the final exit from mitosis and for the initiation of a new cell cycle. In extracts from frog or clam eggs, degradation is accompanied by ubiquitination of cyclin. Three genes, CDC16, CDC23, and CSE1 have recently been shown to be required specifically for cyclin B proteolysis in yeast. To test whether these genes are required for cyclin ubiquitination, we prepared extracts from G1-arrested yeast cells capable of conjugating ubiquitin to the B-type cyclin Clb2. The ubiquitination activity was cell cycle regulated, required Clb2's destruction box, and was low if not absent in cdc16, cdc23, cdc27, and cse1 mutants. Furthermore all these mutants were also defective in ubiquitination of another mitotic B-type cyclin, Clb3. The Cdc16, Cdc23, and Cdc27 proteins all contain several copies of the tetratricopeptide repeat and are subunits of a complex that is required for the onset of anaphase. The finding that gene products that are required for ubiquitination of Clb2 and Clb3 are also required for cyclin proteolysis in vivo provides the best evidence so far that cyclin B is degraded via the ubiquitin pathway in living cells. Xenopus homologues of Cdc16 and Cdc27 have meanwhile been shown to be associated with a 20S particle that appears to function as a cell cycle-regulated ubiquitin-protein ligase.
 ...
PMID:TPR proteins required for anaphase progression mediate ubiquitination of mitotic B-type cyclins in yeast. 874 51

The Cdc28p cyclin-dependent kinase is thought to both catalyze the onset of DNA replication and prevent rereplication by blocking the reassembly of initiation complexes at replication origins. Budding yeast with mutations in the CDC16 gene represent an exception to this model, because they rereplicate DNA despite being in a G2-like arrest with continually elevated Cdc28p kinase activity. We show, in contradiction to Pichler et al. (1997), that the extra DNA that accumulates in cdc16 mutants is largely chromosomal, as we originally reported. Two-dimensional DNA electrophoresis shows that cdc16 mutants reinitiate DNA synthesis from normal chromosome replication origins, and density transfer experiments show that multiple chromosomal locations are affected. Rereplication from origins requires both Cdc6p and Cdc46/Mcm5p, initiation proteins that had been thought to be inactivated by the Cdc28p kinase. These results establish that CDC16 is required to prevent inappropriate firing of replication origins.
 ...
PMID:CDC16 controls initiation at chromosome replication origins. 966 Sep 30