Dissociation of CDK2 from cyclin A in response to the topoisomerase II inhibitor etoposide in v-src-transformed but not normal NIH 3T3 cells.
Our previous work has demonstrated that treatment of NIH 3T3 cells with etoposide (VP16), an inhibitor of DNA topoisomerase II and widely used anticancer agent, results in G2/M-phase arrest, whereas treatment of cells transformed by v-src, v-ras, or v-raf results in an S-phase blockage. The present studies describe the mechanistic aspects of this selective S-phase arrest in the v-src-transformed cells. The S-phase arrest in these cells was found to be coupled with depletion of cyclin A-dependent kinase activity. This decrease could not be explained by changes in the overall level of cyclin A, CDK2, p27, or p21 proteins. Rather, it was associated with a time-dependent reduction of CDK2 protein complexed with cyclin A following VP16 treatment. It was further shown that the decrease of cyclin A-associated CDK2 was linked to an increase of CDK2 protein in cyclin E immunocomplexes, which suggests that CDK2 might become redistributed following treatment with VP16. Thus, oncogenic transformation by v-src can trigger separation of CDK2 protein from cyclin A in response to VP16. This might contribute to the depletion of cyclin A-dependent kinase activity and the selective S-phase arrest by VP16 in v-src-transformed cells.
Chen
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G
Department of Molecular Biology, Cleveland Clinic Foundation, Cleveland, Ohio, 44195, USA. cheng@cesmtp.ccf.org
Hitomi
M
M
D016475:3T3 Cells / Q000187:drug effects* / Q000201:enzymology; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects; D002472:Cell Transformation, Viral; D019925:Cyclin A / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology*; D016391:Genes, src / Q000502:physiology*; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D059005:Topoisomerase II Inhibitors
D019925:Cyclin A; D011518:Proto-Oncogene Proteins; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D015688:Oncogene Protein pp60(v-src); D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; C495902:Cdk4 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases