Quantitative analyses reveal the importance of regulated Hdmx degradation for p53 activation.
P53 regulates numerous downstream targets to induce cell cycle arrest, senescence, apoptosis, and DNA repair in response to diverse stresses. Hdm2 and Hdmx are critical negative regulators of P53 because Hdm2 regulates P53 abundance, and both can antagonize P53 transactivation. Modest changes in Hdm2 or Hdmx abundance affect P53 regulation, yet quantitative information regarding their endogenous intracellular concentrations and subcellular distributions during a stress response are lacking. We analyzed these parameters in normal and cancer cells after DNA damage. Our data show that the nuclear abundance of Hdm2 and Hdmx relative to P53 limits P53 activity in cells growing in culture. Upon DNA damage, P53 nuclear abundance increases, whereas Hdm2 and Hdmx stability decreases, which greatly limits their ability to antagonize P53, regardless of their levels. These data indicate that the damage-activated switch in Hdm2 ubiquitin ligase preference from P53 to itself and Hdmx is central to P53 activation.
Wang
Yunyuan V
YV
Gene Expression Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. wahl@salk.edu
Wade
Mark
M
Wong
Eetsin
E
Li
Yao-Cheng
YC
Rodewald
Luo Wei
LW
Wahl
Geoffrey M
GM
D018797:Cell Cycle Proteins; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D007700:Kinetics; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D004247:DNA