title: Inhibition of HIF-1- and wild-type p53-stimulated transcription by codon Arg175 p53 mutants with selective loss of functions.
abstract: Overexpression of ectopic mutant p53 represses wild-type p53-stimulated transcription, known as a dominant negative effect. On the other hand, overexpression of wild-type p53 can repress transcription stimulated by several transcription factors, including hypoxia-inducible factor-1 (HIF-1). Using a panel of well-characterized Arg175 p53 mutants we found that only mutants (Tyr175, Trp175, Asp175 and Phe175) which have completely lost their ability to transactivate repress wild-type p53-stimulated Bax, p21 and PG13 promoter constructs. In contrast, Asn175, Gln175, Leu175 and Pro175 mutants which partially retained transactivating functions did not exert dominant negative effects against PG13 and p21 promoter constructs. However, these latter mutants failed to activate Bax and, instead, exerted a dominant negative effect on a Bax-Luc promoter construct. We conclude that a dominant negative effect is promoter selective as a consequence of selective loss of transactivating function. Albeit less potent than wild-type p53, all Arg175 p53 mutants retained partial ability to repress HIF-1-stimulated transcription. We propose that transrepression and the dominant negative effect have similar mechanisms and may involve competition with transcription factors (wild-type p53, HIF-1, etc.) for cofactors such as p300. Thus, a p53(22/23) mutant, which is deficient in p300 binding, did not exert dominant negative effects. Like transrepression, the dominant negative effect required overexpression of mutant p53 and, therefore, is not dominant. In the presence of a wild-type p53 allele, levels of endogenous mutant p53 protein were low in heterozygous cells. Endogenous mutant p53 became overexpressed only after loss of the second p53 allele. Therefore, endogenous mutant p53s are unable to display a dominant negative effect. This explains why loss of the second p53 allele is required to eliminate p53 functions in cancer cells.
authors.affiliation: Medicine Branch, National Cancer Institute, NIH, Bethesda, MD 20892, USA. mikhailb@box-m.nih.gov
authors.forename: M V
authors.initials: MV
authors.lastname: Blagosklonny
authors.forename: P
authors.initials: P
authors.lastname: Giannakakou
authors.forename: L Y
authors.initials: LY
authors.lastname: Romanova
authors.forename: K M
authors.initials: KM
authors.lastname: Ryan
authors.forename: K H
authors.initials: KH
authors.lastname: Vousden
authors.forename: T
authors.initials: T
authors.lastname: Fojo
mesh_terms: D001120:Arginine / Q000235:genetics; D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics; D003062:Codon / Q000235:genetics; D016384:Consensus Sequence; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D005260:Female; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008297:Male; D009154:Mutation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2; D013379:Substrate Specificity; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; C493956:CDKN1A protein, human; D003062:Codon; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D001120:Arginine