Baumgarten Axel J, Felthaus Julia, Wäsch Ralph
Department of Hematology and Oncology, Albert-Ludwigs University Medical Center, Freiburg, Germany.
Cell Cycle. 2009 Feb 15;8(4):643-6. doi: 10.4161/cc.8.4.7810. Epub 2009 Feb 8.
The anaphase-promoting complex/cyclosome (APC/C) is a conserved ubiquitin ligase controlling mitosis and G1 phase of the cell cycle. The APC/C is activated by two regulatory subunits Cdc20 (APC/C(Cdc20)) and Cdh1 (APC/C(Cdh1)) to target securin, mitotic cyclins and other cell cycle regulatory proteins. Cdc20 is essential for sister chromatid separation at the meta- to anaphase transition in yeast, drosophila and perhaps mouse embryos. However, whether Cdc20 is essential for mitotic control of human somatic cells is uncertain. Therefore, we used a lentiviral vector-mediated inducible RNA interference (RNAi) system to generate strong downregulation of Cdc20 expression in clonal cells to further elucidate the role of human Cdc20. Here we show, that even an almost complete knockdown of Cdc20 below the detection limit in western blots does neither cause a mitotic block nor significant stabilization of the APC/C(Cdc20) substrates cyclin B and securin. Thus, there may be redundant mechanisms of mitotic control in the human somatic cell cycle.
后期促进复合体/细胞周期体（APC/C）是一种保守的泛素连接酶，可控制细胞周期的有丝分裂和G1期。APC/C由两个调节亚基Cdc20（APC/C（Cdc20））和Cdh1（APC/C（Cdh1））激活，以靶向切割蛋白、有丝分裂周期蛋白和其他细胞周期调节蛋白。Cdc20对于酵母、果蝇以及可能的小鼠胚胎中从中期到后期转变时姐妹染色单体的分离至关重要。然而，Cdc20对于人类体细胞的有丝分裂控制是否必不可少尚不确定。因此，我们使用慢病毒载体介导的诱导性RNA干扰（RNAi）系统在克隆细胞中强烈下调Cdc20的表达，以进一步阐明人类Cdc20的作用。我们在此表明，即使在蛋白质免疫印迹中Cdc20几乎完全敲低至检测限以下，也既不会导致有丝分裂阻滞，也不会使APC/C（Cdc20）底物周期蛋白B和切割蛋白显著稳定。因此，人类体细胞周期中可能存在有丝分裂控制的冗余机制。
