Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
Curr Biol. 2011 Mar 8;21(5):428-32. doi: 10.1016/j.cub.2011.01.072. Epub 2011 Feb 25.
Supernumerary centrosomes are a key cause of genomic instability in cancer cells. New centrioles can be generated by duplication with a mother centriole as a platform or, in the absence of preexisting centrioles, by formation de novo. Polo-like kinase 4 (Plk4) regulates both modes of centriole biogenesis, and Plk4 deregulation has been linked to tumor development. We show that Plx4, the Xenopus homolog of mammalian Plk4 and Drosophila Sak, induces de novo centriole formation in vivo in activated oocytes and in egg extracts, but not in immature or in vitro matured oocytes. Both kinase activity and the polo-box domain of Plx4 are required for de novo centriole biogenesis. Polarization microscopy in "cycling" egg extracts demonstrates that de novo centriole formation is independent of Cdk2 activity, a major difference compared to template-driven centrosome duplication that is linked to the nuclear cycle and requires cyclinA/E/Cdk2. Moreover, we show that the Mos-MAPK pathway blocks Plx4-dependent de novo centriole formation before fertilization, thereby ensuring paternal inheritance of the centrosome. The results define a new system for studying the biochemical and molecular basis of de novo centriole formation and centriole biogenesis in general.
多余的中心体是癌细胞基因组不稳定的一个关键原因。新的中心粒可以通过以母中心粒为平台的复制产生，或者在没有预先存在的中心粒的情况下从头形成。Polo 样激酶 4（Plk4）调节中心体发生的这两种模式，Plk4 的失调与肿瘤的发展有关。我们表明，Plexin4（哺乳动物 Plk4 和果蝇 Sak 的 Xenopus 同源物）在激活的卵母细胞中和卵提取物中诱导体内新的中心粒形成，但在不成熟或体外成熟的卵母细胞中则不会。Plx4 的激酶活性和 polo 框结构域对于新的中心粒生物发生都是必需的。在“循环”卵提取物中的偏光显微镜显示，新的中心粒形成独立于 Cdk2 活性，这与模板驱动的中心体复制有很大的不同，模板驱动的中心体复制与核周期有关，需要 cyclinA/E/Cdk2。此外，我们表明，Mos-MAPK 途径在受精前阻止 Plx4 依赖的新中心粒形成，从而确保了中心体的父系遗传。这些结果定义了一个新的系统，用于研究从头形成中心粒和中心粒发生的生化和分子基础。
