Venenum Biodesign, Genesis Biotechnology Group, Hamilton, NJ, USA.
Cell Cycle. 2011 May 1;10(9):1420-34. doi: 10.4161/cc.10.9.15485.
Protein phosphatase 2A (PP2A) is a heterotrimer consisting of A and B regulatory subunits and a C catalytic subunit. PP2A regulates mitotic cell events that include the cell cycle, nutrient sensing, p53 stability and various mitogenic signals. The role of PP2A during meiosis is less understood. We explored the role of Saccharomyces cerevisiae PP2A during meiosis. We show a PP2A (Cdc)⁵⁵ containing the human B/55 family B subunit ortholog, Cdc55, is required for progression through meiosis I. Mutant cells lacking Cdc55 remain mononucleated. They harbor meiotic gene expression, premeiotic DNA replication, homologous recombination and spindle pole body (SPB) defects. They initiate but do not complete replication and are defective in performing intergenic homologous recombination. Bypass alleles, which allow cells defective in recombination to finish meiosis, do not suppress the meiosis I defect. cdc55 cells arrest with a single SPB lacking microtubules, or duplicated but not separated SBPs containing microtubules. Finally, the premeiotic replication defect is suppressed by loss of Rad9 checkpoint function. We conclude PP2A (Cdc)⁵⁵ is required for the proper temporal initiation of multiple meiotic events and/or monitors these events to ensure their fidelity.
蛋白磷酸酶 2A（PP2A）是一种由 A 和 B 调节亚基和 C 催化亚基组成的异三聚体。PP2A 调节有丝分裂细胞事件，包括细胞周期、营养感应、p53 稳定性和各种有丝分裂信号。PP2A 在减数分裂中的作用知之甚少。我们探讨了酿酒酵母 PP2A 在减数分裂中的作用。我们发现含有人类 B/55 家族 B 亚基同源物 Cdc55 的 PP2A（Cdc）⁵⁵是通过减数分裂 I 所必需的。缺乏 Cdc55 的突变细胞仍保持单核。它们具有减数分裂基因表达、减数分裂前 DNA 复制、同源重组和纺锤体极体（SPB）缺陷。它们启动但不能完成复制，并且在进行基因间同源重组时存在缺陷。允许重组缺陷细胞完成减数分裂的旁路等位基因不能抑制减数分裂 I 缺陷。cdc55 细胞以单个缺乏微管的 SPB 或含有微管的复制但未分离的 SBPs 停滞。最后，通过丧失 Rad9 检查点功能抑制了减数分裂前的复制缺陷。我们得出结论，PP2A（Cdc）⁵⁵是多个减数分裂事件适当时间启动所必需的，或者监测这些事件以确保其保真度。
