Fiscella M, Zhang H, Fan S, Sakaguchi K, Shen S, Mercer W E, Vande Woude G F, O'Connor P M, Appella E
Advanced BioScience Laboratories-Basic Research Program, Molecular Oncology Section, Molecular Virology and Carcinogenesis Laboratory, Frederick, MD 21702, USA.
Proc Natl Acad Sci U S A. 1997 Jun 10;94(12):6048-53. doi: 10.1073/pnas.94.12.6048.
Exposure of mammalian cells to ionizing radiation (IR) induces a complex array of cellular responses including cell cycle arrest and/or apoptosis. IR-induced G1 arrest has been shown to depend on the presence of the tumor suppressor p53, which acts as a transcriptional activator of several genes. p53 also plays a role in the induction of apoptosis in response to DNA damage, and this pathway can be activated by both transcription-dependent and -independent mechanisms. Here we report the identification of a novel transcript whose expression is induced in response to IR in a p53-dependent manner, and that shows homology to the type 2C protein phosphatases. We have named this novel gene, wip1. In vitro, recombinant Wip1 displayed characteristics of a type 2C phosphatase, including Mg2+ dependence and relative insensitivity to okadaic acid. Studies performed in several cell lines revealed that wip1 accumulation following IR correlates with the presence of wild-type p53. The accumulation of wip1 mRNA following IR was rapid and transient, and the protein was localized to the nucleus. Similar to waf1, ectopic expression of wip1 in human cells suppressed colony formation. These results suggest that Wip1 might contribute to growth inhibitory pathways activated in response to DNA damage in a p53-dependent manner.
哺乳动物细胞暴露于电离辐射（IR）会引发一系列复杂的细胞反应，包括细胞周期停滞和/或凋亡。已表明IR诱导的G1期停滞依赖于肿瘤抑制因子p53的存在，p53作为多个基因的转录激活因子发挥作用。p53在响应DNA损伤诱导的凋亡中也起作用，并且该途径可通过转录依赖性和非依赖性机制激活。在此，我们报告鉴定了一种新的转录本，其表达以p53依赖性方式响应IR诱导，并且与2C型蛋白磷酸酶具有同源性。我们将这个新基因命名为wip1。在体外，重组Wip1表现出2C型磷酸酶的特性，包括对Mg2+的依赖性和对冈田酸的相对不敏感性。在几种细胞系中进行的研究表明，IR后wip1的积累与野生型p53的存在相关。IR后wip1 mRNA的积累迅速且短暂，并且该蛋白定位于细胞核。与waf1类似，wip1在人细胞中的异位表达抑制了集落形成。这些结果表明，Wip1可能以p53依赖性方式促进响应DNA损伤而激活的生长抑制途径。
