Hachiya M, Chumakov A, Miller C W, Akashi M, Said J, Koeffler H P
Department of Medicine, Cedars-Sinai Medical Center, UCLA School of Medicine 90048.
Anticancer Res. 1994 Sep-Oct;14(5A):1853-9.
The p53 encodes a cellular phosphoprotein that has been association with both neoplastic transformation and the control of cellular growth. Recent studies have reported that p53 also acts as a transcriptional regulator. We have studied transactivational properties of human wild-type and mutant p53 proteins representing 4 major mutational hotspots (codons 141, 175, 248, 273) as well as a double mutant Tyr141/His273 and a p53 with the transcriptional activating region removed (pcDC2). Transactivation by p53 was shown with a p53 concensus binding sequence controlled CAT reporter gene, and activity was assayed after co-transfection of the reporter with either wild-type or mutant p53 expression constructs. Wild-type p53 as well as one mutant p53 [(mutation of arginine to histidine at codon 273 (His 273)], had strong transactivating activity, but all other mutant p53s were inactive in transcriptional activation, including the double mutant Tyr141/His273 suggesting that the Tyr141 mutation was dominant over the His273 mutation in the same protein. Moreover, when mutant p53 (Tyr141, His175, Trp248, or Tyr141/His273) was cotransfected with either wild-type p53 or mutant His273 p53, these mutants inhibited the transactivation of coexpressed wild-type p53. The p53 vector (pcDC2), which contains p53 oligomerization sequences, but not the transactivational domain, markedly inhibited wild-type p53 transactivational activity. Each of the mutant p53s similarly inhibited the transactivation of His273 p53. Therefore, with the exception of His273, each of the other mutant p53 were unable to transactivate and each behaved in a dominant negative fashion.
p53编码一种细胞磷蛋白，该蛋白与肿瘤转化及细胞生长控制均有关联。最近的研究报道p53还可作为一种转录调节因子。我们研究了代表4个主要突变热点（密码子141、175、248、273）的人类野生型和突变型p53蛋白的反式激活特性，以及一个双突变体Tyr141/His273和一个去除了转录激活区域的p53（pcDC2）。通过一个受p53共有结合序列控制的CAT报告基因来显示p53的反式激活作用，在将报告基因与野生型或突变型p53表达构建体共转染后检测活性。野生型p53以及一种突变型p53 [密码子273处精氨酸突变为组氨酸（His 273）] 具有很强的反式激活活性，但所有其他突变型p53在转录激活方面均无活性，包括双突变体Tyr141/His273，这表明在同一蛋白中Tyr141突变对His273突变占主导地位。此外，当突变型p53（Tyr141、His175、Trp248或Tyr141/His273）与野生型p53或突变型His273 p53共转染时，这些突变体抑制了共表达的野生型p53的反式激活作用。含有p53寡聚化序列但不含转录激活结构域的p53载体（pcDC2）显著抑制野生型p53的反式激活活性。每个突变型p53同样抑制His273 p53的反式激活作用。因此，除His273外，其他每个突变型p53均无法进行反式激活，且均表现出显性负性作用。
