Lin Jing, Ding Lihua, Jin Rui, Zhang Hao, Cheng Long, Qin Xi, Chai Jiake, Ye Qinong
Beijing Institute of Biotechnology, Beijing, PR China.
Int J Biochem Cell Biol. 2009 Jul;41(7):1613-8. doi: 10.1016/j.biocel.2009.02.007. Epub 2009 Feb 21.
Four and a half LIM domains 1 (FHL1) belongs to a family of LIM-only proteins that regulate gene transcription, cell proliferation, differentiation and apoptosis. However, the biological function of FHL1 remains largely unknown. We used a yeast two-hybrid system and identified receptor interacting protein of 140kDa (RIP140) as a novel FHL1-binding protein. RIP140 interacted with FHL1 both in vitro and in mammalian cells and estrogen enhanced this interaction. All domains of FHL1 are required to interact with RIP140. Overexpression of FHL1 enhanced RIP140 repression of estrogen signaling in breast cancer cells in a reporter assay, whereas reduction of endogenous FHL1 with FHL1 small interfering RNA abolished this effect. Furthermore, overexpression of the FHL1 deletion mutant that lacks the RIP140-binding sites had no effect on RIP140 repression of estrogen signaling. Consistent with the results of the reporter assays, FHL1 and RIP140 synergistically inhibited the transcription of the estrogen-responsive gene pS2. The results presented here suggested the cooperative transcriptional regulation of estrogen signaling by FHL1 and RIP140, and might provide a new regulation mechanism by which estrogen signaling-related diseases such as breast cancer develop.
四和半LIM结构域蛋白1（FHL1）属于仅含LIM结构域的蛋白质家族，该家族蛋白可调节基因转录、细胞增殖、分化和凋亡。然而，FHL1的生物学功能在很大程度上仍不清楚。我们利用酵母双杂交系统，鉴定出140kDa的受体相互作用蛋白（RIP140）为一种新的FHL1结合蛋白。RIP140在体外和哺乳动物细胞中均与FHL1相互作用，雌激素可增强这种相互作用。FHL1的所有结构域都需要与RIP140相互作用。在报告基因检测中，FHL1的过表达增强了RIP140对乳腺癌细胞中雌激素信号的抑制作用，而用FHL1小干扰RNA降低内源性FHL1则消除了这种作用。此外，缺乏RIP140结合位点的FHL1缺失突变体的过表达对RIP140对雌激素信号的抑制作用没有影响。与报告基因检测结果一致，FHL1和RIP140协同抑制雌激素反应基因pS2的转录。此处呈现的结果表明FHL1和RIP140对雌激素信号进行协同转录调控，可能为乳腺癌等雌激素信号相关疾病的发生提供一种新的调控机制。
