The contribution of the RING finger domain of MDM2 to cell cycle progression.
The MDM2 oncoprotein binds to p53 and abrogates p53-mediated G1 arrest and apoptosis. We show that MDM2 over-expression accelerates cell cycle progression of RPM12650 cells by overcoming the negative effect of endogenous wild type p53 at the G1/S checkpoint. The interaction with p53 and transcription inhibition are necessary but not sufficient. The RING finger domain of MDM2 is also required for the positive effect of MDM2 on the cell cycle. Surprisingly, several point mutants in the zinc binding sites of the RING finger are fully competent for cell cycle stimulation even though they abolish MDM2-directed degradation of p53 and MDM2 E3-ligase activity. In contrast, alterations in and around the cryptic nucleolar localization sequence (KR motif) inhibit MDM2-mediated cell cycle progression as well as p53 degradation and MDM2 E3 ligase activity. We found that all the RING mutants decrease inhibition of both p53 dependent reporters and endogenous p21CIP1/WAF1/SDI1. These results indicate that the RING finger of MDM2 has a role in the regulation of the cell cycle that is independent of p53 degradation and endogenous p21CIP1/WAF1/SDI1 regulation.
Argentini
M
M
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch, France.
Barboule
N
N
Wasylyk
B
B
D000595:Amino Acid Sequence; D002453:Cell Cycle / Q000502:physiology*; D002466:Cell Nucleolus / Q000378:metabolism; D017124:Conserved Sequence; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D003545:Cysteine; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008025:Ligases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D003545:Cysteine