Huang Hua, Kaku Shinsuke, Knights Chad, Park Byung, Clifford Jane, Kulesz-Martin Molly
Department of Experimental Therapuetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
Exp Cell Res. 2002 Oct 1;279(2):248-59. doi: 10.1006/excr.2002.5596.
The protein encoded by C-terminal alternatively spliced p53 mRNA (p53as) has been shown previously to occur naturally in mouse cells and to bind sequence-specifically to DNA more efficiently than p53 (p53r, regular form). In the current study, p53as and p53r proteins ectopically expressed in p53-deficient cells each transactivated reporter plasmids containing p53 binding sites. However, p53as consistently was more efficient in transcriptional repression of promoters lacking p53 binding sites and in concentration-dependent repression of the p21(WAF1/Cip-l/Sdi) promoter sequence. The p53as protein, like p53r, associated with TATA-binding protein (TBP), indicating that this interaction does not require the last 26 amino acids of p53. Consistent with its stronger repression effects, p53as interfered with TBP binding to a TATA-containing DNA sequence more efficiently than p53r protein. Taken together, these in vitro and in vivo results demonstrate a novel role in transcriptional repression for a naturally occurring C-terminal variant form of mouse p53 protein associated with differences in DNA binding properties and interference with transcription factor binding.
先前研究表明，C末端选择性剪接的p53 mRNA（p53as）编码的蛋白质天然存在于小鼠细胞中，并且与DNA的序列特异性结合比p53（p53r，正常形式）更有效。在当前研究中，在p53缺陷细胞中异位表达的p53as和p53r蛋白各自反式激活了含有p53结合位点的报告质粒。然而，p53as在缺乏p53结合位点的启动子的转录抑制以及p21（WAF1/Cip-1/Sdi）启动子序列的浓度依赖性抑制方面始终更有效。与p53r一样，p53as蛋白与TATA结合蛋白（TBP）相关联，表明这种相互作用不需要p53的最后26个氨基酸。与其更强的抑制作用一致，p53as比p53r蛋白更有效地干扰TBP与含TATA的DNA序列的结合。综上所述，这些体外和体内结果证明了与DNA结合特性差异和对转录因子结合的干扰相关的天然存在的小鼠p53蛋白C末端变体形式在转录抑制中的新作用。
