Zeng Qi-Yan, Zeng Lin-Jie, Huang Yu, Huang Yong-Qi, Zhu Qi-Fang, Liao Zhi-Hong
Department of Biochemistry and Molecular Biology, Guangxi Medical University, Nanning, China E-mail :
Asian Pac J Cancer Prev. 2014;15(9):4101-7. doi: 10.7314/apjcp.2014.15.9.4101.
Protein phosphatase 1 (PP1) is a major serine/threonine phosphatase that controls gene expression and cell cycle progression. The active mutant IPP5 (8-60hIPP5(m)), the latest member of the inhibitory molecules for PP1, has been shown to inhibit the growth of human cervix carcinoma cells (HeLa). In order to elucidate the underlying mechanisms, the present study assessed overexpression of 8-60hIPP5(m) in HeLa cells. Flow cytometric and biochemical analyses showed that overexpression of 8-60hIPP5(m) induced G2/M-phase arrest, which was accompanied by the upregulation of cyclin B1 and phosphorylation of G2/M-phase proteins ATM, p53, p21(cip1/waf1) and Cdc2, suggesting that 8-60hIPP5(m) induces G2/M arrest through activation of the ATM/p53/p21(cip1/waf1)/Cdc2/ cyclin B1 pathways. We further showed that overexpression of 8-60hIPP5(m) led to delayed nuclear translocation of cyclin B1. 8-60hIPP5(m) also could translocate to the nucleus in G2/M phase and interact with pp1α and Cdc2 as demonstrated by co-precipitation assay. Taken together, our data demonstrate a novel role for 8-60hIPP5(m) in regulation of cell cycle in HeLa cells, possibly contributing to the development of new therapeutic strategies for cervix carcinoma.
蛋白磷酸酶1（PP1）是一种主要的丝氨酸/苏氨酸磷酸酶，可控制基因表达和细胞周期进程。活性突变体IPP5（8 - 60hIPP5(m)）是PP1抑制分子的最新成员，已被证明可抑制人宫颈癌细胞（HeLa）的生长。为了阐明其潜在机制，本研究评估了8 - 60hIPP5(m)在HeLa细胞中的过表达情况。流式细胞术和生化分析表明，8 - 60hIPP5(m)的过表达诱导了G2/M期阻滞，同时伴随着细胞周期蛋白B1的上调以及G2/M期蛋白ATM、p53、p21(cip1/waf1)和Cdc2的磷酸化，这表明8 - 60hIPP5(m)通过激活ATM/p53/p21(cip1/waf1)/Cdc2/细胞周期蛋白B1通路诱导G2/M期阻滞。我们进一步表明，8 - 60hIPP5(m)的过表达导致细胞周期蛋白B1的核转位延迟。如共沉淀分析所示，8 - 60hIPP5(m)在G2/M期也可转位至细胞核并与pp1α和Cdc2相互作用。综上所述，我们的数据证明了8 - 60hIPP5(m)在HeLa细胞周期调控中的新作用，可能有助于开发宫颈癌的新治疗策略。
