p21WAF1/CIP1 mutants deficient in inhibiting cyclin-dependent kinases (CDKs) can promote assembly of active cyclin D/CDK4(6) complexes in human tumor cells.
The cyclin-dependent kinase (CDK) inhibitor p21WAF1/CIP1 is a multidomain, multifunctional protein and a candidate tumor suppressor. Here, we show that, among rationally designed and tumor-associated mutants of human p21 ectopically expressed in U-2-OS cells, those that are selectively deficient in binding to either cyclin or CDK are partially impaired in inhibiting endogenous CDK activities but efficiently promote assembly of active cyclin D/CDK4(6) complexes. These results provide mechanistic insights into the p21-cyclin/CDK interplay in vivo and suggest a functional subclassification of tumor-specific aberrations of p21. Intriguingly, the subclass exemplified by the melanoma-derived N50S mutant may promote tumorigenesis, by both attenuating CDK-inhibitory function and concomitantly activating the proto-oncogenic cyclin D-dependent kinases.
Welcker
M
M
Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
Lukas
J
J
Strauss
M
M
Bartek
J
J
D056741:Cyclin D; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D016147:Genes, Tumor Suppressor; D006801:Humans; D008545:Melanoma / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D014407:Tumor Cells, Cultured
C493956:CDKN1A protein, human; D056741:Cyclin D; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases