A chromatin-associated and transcriptionally inactive p53-Mdm2 complex occurs in mdm2 SNP309 homozygous cells

Nicoleta C. Arva, Tamara R. Gopen, Kathryn E. Talbott, Latoya E. Campbell, Agustin Chicas, David E. White, Gareth L. Bond, Arnold J. Levine, Jill Bargonetti*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

100 Scopus citations

Abstract

In cancer cells, the function of the tumor suppressor protein p53 is usually blocked. Impairment of the p53 pathway results in tumor cells with endogenous overexpression of Mdm2 via a naturally occurring single nucleotide polymorphism (SNP) in the mdm2 gene at position 309. Here we report that in mdm2 SNP309 cells, inactivation of p53 results in a chromatin-associated Mdm2-p53 complex without clearance of p53 by protein degradation. Nuclear accumulation of p53 protein in mdm2 SNP309 cells results after 6 h of camptothecin, etoposide, or mitomycin C treatment, with the p53 protein phosphorylated at Ser 15. Chromatin immunoprecipitation demonstrated p53 and Mdm2 bound to p53 responsive elements. Interestingly, although the p53 protein was able to bind to DNA, quantitative PCR showed compromised transcription of endogenous target genes. Additionally, exogenously introduced p53 was incapable of activating transcription from p53 responsive elements in SNP309 cells, confirming the trans-acting nature of the inhibitor. Inhibition of Mdm2 by siRNA resulted in transcriptional activation of these p53 targets. Our data suggest that overproduction of Mdm2, resulting from a naturally occurring SNP, inhibits chromatin-bound p53 from activating the transcription of its target genes.

Original languageEnglish (US)
Pages (from-to)26776-26787
Number of pages12
JournalJournal of Biological Chemistry
Volume280
Issue number29
DOIs
StatePublished - Jul 22 2005

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'A chromatin-associated and transcriptionally inactive p53-Mdm2 complex occurs in mdm2 SNP309 homozygous cells'. Together they form a unique fingerprint.

Cite this