Milner J, Medcalf E A
Department of Pathology, University of Cambridge, U.K.
J Mol Biol. 1990 Dec 5;216(3):481-4. doi: 10.1016/0022-2836(90)90371-R.
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.
p53基因是异常细胞生长的抑制因子，但也会因突变而发生致癌激活。最近发现突变等位基因p53-Val135具有温度敏感性，在37摄氏度时发挥癌基因功能，在32.5摄氏度时发挥肿瘤抑制因子功能。为了研究p53-Val135温度敏感性的分子机制，利用兔网织红细胞裂解物在37摄氏度和30摄氏度体外翻译p53 mRNA。野生型蛋白p53-Ala135的免疫反应性和T抗原结合不受温度影响，与体内表达的野生型p53相似。相比之下，突变型p53-Val135蛋白受温度影响明显。在37摄氏度时，p53-Val135的T抗原结合减少，且不与单克隆抗体PAb246和PAb1620反应。在30摄氏度时，p53-Val135表现得与野生型p53一样。温度对p53-Val135也有翻译后效应，温度从30摄氏度转变为37摄氏度后两分钟内，p53-Val135从野生型完全转变为突变型表型。当温度从37摄氏度降至30摄氏度时，从突变型到野生型表型的转变不完全。我们认为，p53-Val135的温度依赖性形式代表了p53蛋白的构象变体，在细胞生长控制中具有相反的功能。
