Jinno S, Suto K, Nagata A, Igarashi M, Kanaoka Y, Nojima H, Okayama H
Department of Molecular Genetics, Osaka University, Japan.
EMBO J. 1994 Apr 1;13(7):1549-56. doi: 10.1002/j.1460-2075.1994.tb06417.x.
The cdc25+ tyrosine phosphatase is a key mitotic inducer of the fission yeast Schizosaccharomyces pombe, controlling the timing of the initiation of mitosis. Mammals contain at least three cdc25+ homologues called cdc25A, cdc25B and cdc25C. In this study we investigate the biological function of cdc25A. Although very potent in rescuing the S.pombe cdc25 mutant, cdc25A is less structurally related to the S.pombe enzyme. Northern and Western blotting detection reveals that unlike cdc25B, cdc25C and cdc2, cdc25A is predominantly expressed in late G1. Moreover, immunodepletion of cdc25A in rat cells by microinjection of a specific antibody effectively blocks their cell cycle progression from G1 into the S phase, as determined by laser scanning single cell cytometry. These results indicate that cdc25A is not a mitotic regulator but a novel phosphatase that plays a crucial role in the start of the cell cycle. In view of its strong ability to activate cdc2 kinase and its specific expression in late G1, cdc2-related kinases functioning early in the cell cycle may be targets for this phosphatase.
细胞分裂周期蛋白25（cdc25+）酪氨酸磷酸酶是裂殖酵母粟酒裂殖酵母有丝分裂的关键诱导因子，控制有丝分裂起始的时间。哺乳动物至少含有三种称为cdc25A、cdc25B和cdc25C的cdc25+同源物。在本研究中，我们研究了cdc25A的生物学功能。尽管cdc25A在拯救粟酒裂殖酵母cdc25突变体方面非常有效，但它与粟酒裂殖酵母的酶在结构上的相关性较小。Northern和Western印迹检测显示，与cdc25B、cdc25C和cdc2不同，cdc25A主要在G1晚期表达。此外，通过显微注射特异性抗体对大鼠细胞中的cdc25A进行免疫去除，通过激光扫描单细胞流式细胞术测定，有效地阻断了它们从G1期进入S期的细胞周期进程。这些结果表明，cdc25A不是有丝分裂调节因子，而是一种在细胞周期开始时起关键作用的新型磷酸酶。鉴于其激活cdc2激酶的强大能力及其在G1晚期的特异性表达，在细胞周期早期起作用的与cdc2相关的激酶可能是这种磷酸酶的作用靶点。
