title: Myc-mediated apoptosis requires wild-type p53 in a manner independent of cell cycle arrest and the ability of p53 to induce p21waf1/cip1.
abstract: Deregulated expression of the c-myc proto-oncogene can lead to apoptosis under certain physiological conditions. By introducing a conditionally active Myc allele into primary embryo fibroblasts null for p53, and into fibroblasts without endogenous p53 expression but ectopically expressing a temperature-sensitive p53 allele, we show that expression of wild-type p53 is required for susceptibility to Myc-mediated apoptosis. Although ectopic expression of wild-type p53 blocked cells in the G1 phase of the cell cycle, G1 arrest by isoleucine starvation, in a manner independent of p53, did not confer susceptibility to apoptosis. Thus, growth arrest per se is not sufficient to induce Myc-mediated apoptosis; instead, a property intrinsic to p53 is specifically required. Moreover, apoptosis did not require induction of p53 target proteins, including the cyclin-dependent kinase inhibitor p21waf1/cip1. Therefore, the role of p53 in apoptosis may be distinct from its role in cell cycle arrest.
authors.affiliation: Ben May Institute, University of Chicago, Illinois 60637.
authors.forename: A J
authors.initials: AJ
authors.lastname: Wagner
authors.forename: J M
authors.initials: JM
authors.lastname: Kokontis
authors.forename: N
authors.initials: N
authors.lastname: Hay
mesh_terms: D000483:Alleles; D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000096:biosynthesis*; D003513:Cycloheximide / Q000494:pharmacology; D004622:Embryo, Mammalian; D005347:Fibroblasts; D016193:G1 Phase; D015870:Gene Expression; D016259:Genes, myc; D016158:Genes, p53; D007532:Isoleucine / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016271:Proto-Oncogene Proteins c-myc; D016159:Tumor Suppressor Protein p53; D007532:Isoleucine; D003513:Cycloheximide; D018844:Cyclin-Dependent Kinases