Low levels of cyclin D and nonfunctional Rb protein affect cdk6 association with cyclin-dependent kinase inhibitor p27(Kip1).
p27(Kip1) associates with cyclin/cdk complexes and inhibiting cdk activity, and overexpression of p27(Kip1) induces G1 arrest. We found that p27(Kip1) overexpression inhibits cdk2 kinase activity, but not cdk6 kinase activity in HeLa cells. The amount of p27(Kip1) associated with cdk2 was significantly higher than that associated with cdk6. cdk6 complexes contained detectable amounts of p27(Kip1) in all human cell lines examined, except in HeLa cells where p27(Kip1) preferentially associated with cdk2. It appears that in HeLa cells overexpressed p27(Kip1) fails to inhibit cdk6 kinase activity because of low binding affinity of cdk6 to p27(Kip1). The low binding affinity is due to a low level of the cdk6/cyclin D complexes. Functional inactivation of pRb has an effect on p27(Kip1) association with cdk6/cyclin D complexes.
Kwon
T K
TK
Department of Immunology, School of Medicine, Keimyung University, 194 Dong-San Dong, Jung-Gu, Taegu, 705-717, South Korea. kwontk@dsmc.or.kr
Park
J W
JW
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D002460:Cell Line; D056741:Cyclin D; D051357:Cyclin-Dependent Kinase 2; D051361:Cyclin-Dependent Kinase 6; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism*; D004252:DNA Mutational Analysis; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D014162:Transfection; D025521:Tumor Suppressor Proteins
C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D056741:Cyclin D; D016213:Cyclins; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495911:CDK6 protein, human; C495893:Cdk2 protein, mouse; C495912:Cdk6 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases