title: Abrogation of p53-induced cell cycle arrest by c-Myc: evidence for an inhibitor of p21WAF1/CIP1/SDI1.
abstract: The tumor-suppressor p53 inhibits cell cycle progression by direct transactivation of the p21WAF1/CIP1/SDI1 gene, which encodes a universal inhibitor of cyclin dependent kinases (cdk). The proto-oncogene product c-Myc induces cell cycle progression and, in the absence of survival factors, apoptosis. However, a direct link between the cell cycle machinery and c-Myc has not yet been established. We show that c-Myc has not yet been established. We show that c-Myc abrogates a p53-induced G1-arrest without elevating the expression of cdks or cyclins involved in the G1/S-transition. Instead, the results suggest that c-Myc interferes with the inhibitory action of p21 on cdk/cyclin-complexes by inducing a heat-labile inhibitor of p21. The inactivation of p21 and related cdk-inhibitors may explain several of the oncogenic actions of c-Myc, including the induction of proliferation, immortalisation and the inhibition of differentiation. Modulation of cdk activity by the induction of an inhibitor of cdk-inhibitors represents a novel mechanism of cell cycle regulation in mammalian cells.
mesh_terms: D016475:3T3 Cells; D000818:Animals; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000037:antagonists & inhibitors*; D004789:Enzyme Activation; D016193:G1 Phase / Q000235:genetics*; D016259:Genes, myc; D016158:Genes, p53; D051379:Mice; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000502:physiology*
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016271:Proto-Oncogene Proteins c-myc; D018844:Cyclin-Dependent Kinases