Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
Cell Cycle. 2010 Dec 1;9(23):4688-702. doi: 10.4161/cc.9.23.14050.
Mek1 is a Chk2/Rad53/Cds1-related protein kinase that is required for proper meiotic progression of Schizosaccharomyces pombe. However, the molecular mechanisms of Mek1 regulation and Mek1 phosphorylation targets are unclear. Here, we report that Mek1 is phosphorylated at serine-12 (S12), S14 and threonine-15 (T15) by Rad3 (ATR) and/or Tel1 (ATM) kinases that are activated by meiotic programmed double-strand breaks (DSBs). Mutations of these sites by alanine replacement caused abnormal meiotic progression and recombination rates. Phosphorylation of these sites triggers autophosphorylation of Mek1; indeed, alanine replacement mutations of Mek1-T318 and -T322 residues in the activation loop of Mek1 reduced Mek1 kinase activity and meiotic recombination rates. Substrates of Mek1 include Mus81-T275, Rdh54-T6 and Rdh54-T673. Mus81-T275 is known to regulate the Mus81 function in DNA cleavage, whereas Rdh54-T6A/T673A mutant cells showed abnormal meiotic recombination. Taken together, we conclude that the phosphorylation of Mek1 by Rad3 or Tel1, Mek1 autophosphorylation and Mus81 or Rdh54 phosphorylation by Mek1 regulate meiotic progression in S. pombe.
Mek1 是一种 Chk2/Rad53/Cds1 相关蛋白激酶，它是裂殖酵母减数分裂进程所必需的。然而，Mek1 的调节和 Mek1 磷酸化靶标的分子机制尚不清楚。在这里，我们报告说 Mek1 在丝氨酸-12（S12）、S14 和苏氨酸-15（T15）处被 Rad3（ATR）和/或 Tel1（ATM）激酶磷酸化，这些激酶被减数分裂程序性双链断裂（DSB）激活。这些位点的突变导致异常的减数分裂进程和重组率。这些位点的磷酸化引发 Mek1 的自磷酸化；事实上，Mek1 激活环中的 Mek1-T318 和 -T322 残基的丙氨酸替换突变降低了 Mek1 激酶活性和减数分裂重组率。Mek1 的底物包括 Mus81-T275、Rdh54-T6 和 Rdh54-T673。Mus81-T275 已知调节 Mus81 在 DNA 切割中的功能，而 Rdh54-T6A/T673A 突变细胞显示出异常的减数分裂重组。总之，我们得出结论，Rad3 或 Tel1 对 Mek1 的磷酸化、Mek1 的自磷酸化以及 Mek1 对 Mus81 或 Rdh54 的磷酸化调节了裂殖酵母的减数分裂进程。
