Mouse double minute 2 associates with chromatin in the presence of p53 and is released to facilitate activation of transcription.
The tumor suppressor p53 is a potent transcription factor of which the ability to mediate transcription is inhibited through an interaction with the oncoprotein mouse double minute 2 (Mdm2). The present study has tested the hypothesis that Mdm2 inhibits the p53 response in normally growing cells by binding to chromatin-associated p53. Using chromatin immunoprecipitation, we show that Mdm2 localizes with p53 at its responsive elements on the waf1 and mdm2 genes in human cell lines expressing p53, but not in cell lines lacking p53 expression, indicating that Mdm2 is recruited to regions of DNA in a p53-dependent manner. Interestingly, our results show a decrease of Mdm2 protein associated with p53-responsive elements on the waf1 and mdm2 genes when p53-induced transcription is activated either by DNA damage or through controlled overexpression of p53. Rapid activation of p53 transcriptional activity before increasing p53 protein levels was observed with addition of either small-molecule inhibitors to disrupt the p53-Mdm2 interaction or small interfering RNA to mdm2. These findings indicate Mdm2 transiently localizes with p53 at responsive elements and suggest that latent p53 results from the recruitment of Mdm2 to chromatin.
The Institute for Biomolecular Structure and Function and Department of Biological Sciences, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA.
David E
DE
White
Kathryn E
KE
Talbott
Nicoleta C
NC
Arva
Jill
J
Bargonetti
D045744:Cell Line, Tumor; D002843:Chromatin / Q000378:metabolism* / Q000502:physiology; D047369:Chromatin Immunoprecipitation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D006801:Humans; D020014:K562 Cells; D007951:Leukemia, Myeloid / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D020218:Response Elements; D015533:Transcriptional Activation / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015854:Up-Regulation
C493956:CDKN1A protein, human; D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2