Abrieu A, Brassac T, Galas S, Fisher D, Labbé J C, Dorée M
Centre de Recherches de Biochimie Macromoléculaire, CNRSUPR 1086, 34293 Montpellier cedex 5, France.
J Cell Sci. 1998 Jun;111 ( Pt 12):1751-7. doi: 10.1242/jcs.111.12.1751.
We have investigated whether Plx1, a kinase recently shown to phosphorylate cdc25c in vitro, is required for activation of cdc25c at the G2/M-phase transition of the cell cycle in Xenopus. Using immunodepletion or the mere addition of an antibody against the C terminus of Plx1, which suppressed its activation (not its activity) at G2/M, we show that Plx1 activity is required for activation of cyclin B-cdc2 kinase in both interphase egg extracts receiving recombinant cyclin B, and cycling extracts that spontaneously oscillate between interphase and mitosis. Furthermore, a positive feedback loop allows cyclin B-cdc2 kinase to activate Plx1 at the G2/M-phase transition. In contrast, activation of cyclin A-cdc2 kinase does not require Plx1 activity, and cyclin A-cdc2 kinase fails to activate Plx1 and its consequence, cdc25c activation in cycling extracts.
我们研究了Plx1（一种最近显示在体外可使cdc25c磷酸化的激酶）在非洲爪蟾细胞周期的G2/M期转变时激活cdc25c是否是必需的。使用免疫去除法或仅仅添加一种针对Plx1 C末端的抗体（该抗体在G2/M期抑制其激活而非活性），我们发现，在接受重组细胞周期蛋白B的间期卵提取物以及在间期和有丝分裂之间自发振荡的循环提取物中，激活细胞周期蛋白B - cdc2激酶都需要Plx1活性。此外，一个正反馈环使得细胞周期蛋白B - cdc2激酶在G2/M期转变时激活Plx1。相反，激活细胞周期蛋白A - cdc2激酶不需要Plx1活性，并且在循环提取物中细胞周期蛋白A - cdc2激酶无法激活Plx1及其结果——cdc25c的激活。
