McCleland Mark L, Farrell Jeffrey A, O'Farrell Patrick H
Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.
J Cell Biol. 2009 Mar 9;184(5):639-46. doi: 10.1083/jcb.200810012.
Cyclins are key cell cycle regulators, yet few analyses test their role in timing the events that they regulate. We used RNA interference and real-time visualization in embryos to define the events regulated by each of the three mitotic cyclins of Drosophila melanogaster, CycA, CycB, and CycB3. Each individual and pairwise knockdown results in distinct mitotic phenotypes. For example, mitosis without metaphase occurs upon knockdown of CycA and CycB. To separate the role of cyclin levels from the influences of cyclin type, we knocked down two cyclins and reduced the gene dose of the one remaining cyclin. This reduction did not prolong interphase but instead interrupted mitotic progression. Mitotic prophase chromosomes formed, centrosomes divided, and nuclei exited mitosis without executing later events. This prompt but curtailed mitosis shows that accumulation of cyclin function does not directly time mitotic entry in these early embryonic cycles and that cyclin function can be sufficient for some mitotic events although inadequate for others.
细胞周期蛋白是关键的细胞周期调节因子，但很少有分析测试它们在调控其所调节事件的时间方面的作用。我们利用RNA干扰和胚胎中的实时可视化技术，来确定果蝇（Drosophila melanogaster）的三种有丝分裂细胞周期蛋白CycA、CycB和CycB3各自所调控的事件。每种单独的和成对的敲低都会导致不同的有丝分裂表型。例如，敲低CycA和CycB会导致没有中期的有丝分裂。为了将细胞周期蛋白水平的作用与细胞周期蛋白类型的影响区分开来，我们敲低了两种细胞周期蛋白，并降低了剩余一种细胞周期蛋白的基因剂量。这种降低并没有延长间期，而是中断了有丝分裂进程。有丝分裂前期染色体形成，中心体分裂，细胞核退出有丝分裂而没有执行后续事件。这种迅速但缩短的有丝分裂表明，细胞周期蛋白功能的积累并不直接决定这些早期胚胎周期中有丝分裂的起始时间，并且细胞周期蛋白功能对于某些有丝分裂事件可能是足够的，尽管对其他事件来说是不足的。
