Journal of Biochemistry Advance Access originally published online on March 23, 2007
Journal of Biochemistry 2007 141(5):737-745; doi:10.1093/jb/mvm076
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© 2007 The Japanese Biochemical Society.
p53 Stabilization can be Uncoupled from its Role in Transcriptional Activation by Loss of PTTG1/Securin

Centro Andaluz de Biología Molecular y Medicina Regenerativa (C.S.I.C.) Avda. Americo Vespucio s/n 41092 Seville, Spain
To whom correspondence should be addressed. Tel: +34 954 468004, Fax: +34 954 461664, E-mail: ahernan{at}cica.es
Received March 1, 2007; Accepted March 6, 2007
| Abstract |
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HCT116 cells devoid of PTTG1/securin (sec/ HCT116) show a stabilized yet transcriptionally latent form of p53 protein in the absence of DNA damage. Ser15, Ser20 phosphorylation and other post-transcriptional modifications of p53 resolved by 2D gel electrophoresis are comparable to that observed in sec+/+ HCT116 cells. The difference in degradation was also shown to be independent of the ubiquitin system but reliant on calpains. However, the p53-mediated checkpoint response is active only after genotoxic stress in sec/ HCT116 cells. These findings point to the calpain pathway as a key player to maintain steady state levels of p53 in resting cells without affecting its activity.
Key Words: calpains, gene regulation, p53 tumour suppressor, protein stability, PTTG1/Securin
Abbreviations: ATM, ataxia telangectasia mutated; ATR, ataxia telangectasia related; cdk, cyclin-dependent kinase; CHX, cyclohexymide; Dox, doxorubicin; LLnL, N-acetyl-L-Leucyl-L-leucyl-L-norleucinal; NP40, nonidet P40; PMSF, phenylmethylsulfonylfluoride
*Present address: CR UK Dept of Oncology, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 2XZ, UK
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