Temperature-dependent switching between "wild-type" and "mutant" forms of p53-Val135.
The p53 gene is a suppressor of abnormal cell growth but is also subject to oncogenic activation by mutation. The mutant allele p53-Val135, has recently been discovered to be temperature-sensitive and functions as an oncogene at 37 degrees C and as a tumor suppressor at 32.5 degrees C. In order to investigate the molecular mechanism underlying the temperature sensitivity of p53-Val135 rabbit reticulocyte lysate was used to translate the p53 mRNAs in vitro at 37 degrees C and at 30 degrees C. The immunoreactivity and T antigen binding of wild-type protein p53-Ala135 were unaffected by temperature and were similar to wild-type p53 expressed in vivo. In contrast, the mutant p53-Val135 protein was markedly affected by temperature. At 37 degrees C p53-Val135 showed reduced T antigen binding and did not react with monoclonal antibodies PAb246 and PAb1620. At 30 degrees C, p53-Val135 behaved as the wild-type p53. Temperature also exerted a post-translational effect on p53-Val135 with complete conversion from wild-type to mutant phenotype within two minutes of temperature shift from 30 degrees C to 37 degrees C. There was incomplete conversion from mutant to wild-type phenotype when the temperature was shifted down from 37 degrees C to 30 degrees C. We propose that the temperature dependent forms of p53-Val135 represent conformational variants of the p53 protein with opposing functions in cell growth control.
Milner
J
J
Department of Pathology, University of Cambridge, U.K.
Medcalf
E A
EA
D000818:Animals; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism; D002474:Cell-Free System; D004912:Erythrocytes / Q000378:metabolism; D051379:Mice; D009154:Mutation; D010641:Phenotype; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011817:Rabbits; D013696:Temperature; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D014633:Valine
D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D016159:Tumor Suppressor Protein p53; D014633:Valine