Graduate School of Biostudies, Kyoto University, Yoshidakonoe, Sakyo, Kyoto, Japan.
Department of Molecular and Cell Biology, University of California, Berkeley, United States.
Elife. 2022 Jun 27;11:e77956. doi: 10.7554/eLife.77956.
In the first meiotic cell division, proper segregation of chromosomes in most organisms depends on chiasmata, exchanges of continuity between homologous chromosomes that originate from the repair of programmed double-strand breaks (DSBs) catalyzed by the Spo11 endonuclease. Since DSBs can lead to irreparable damage in germ cells, while chromosomes lacking DSBs also lack chiasmata, the number of DSBs must be carefully regulated to be neither too high nor too low. Here, we show that in , meiotic DSB levels are controlled by the phosphoregulation of DSB-1, a homolog of the yeast Spo11 cofactor Rec114, by the opposing activities of PP4 phosphatase and ATR kinase. Increased DSB-1 phosphorylation in mutants correlates with reduction in DSB formation, while prevention of DSB-1 phosphorylation drastically increases the number of meiotic DSBs both in mutants and in the wild-type background. and its close relatives also possess a diverged paralog of DSB-1, called DSB-2, and loss of is known to reduce DSB formation in oocytes with increasing age. We show that the proportion of the phosphorylated, and thus inactivated, form of DSB-1 increases with age and upon loss of DSB-2, while non-phosphorylatable DSB-1 rescues the age-dependent decrease in DSBs in mutants. These results suggest that DSB-2 evolved in part to compensate for the inactivation of DSB-1 through phosphorylation, to maintain levels of DSBs in older animals. Our work shows that PP4, ATR, and DSB-2 act in concert with DSB-1 to promote optimal DSB levels throughout the reproductive lifespan.
在第一次减数分裂中，大多数生物体中染色体的正确分离依赖于交叉，即同源染色体之间的连续性交换，这些交换源自 Spo11 内切酶催化的程序性双链断裂 (DSB) 的修复。由于 DSB 会导致生殖细胞无法修复的损伤，而缺乏 DSB 的染色体也缺乏交叉，因此必须仔细调节 DSB 的数量，使其既不过高也不过低。在这里，我们表明，在 中，减数分裂 DSB 水平受 DSB-1 的磷酸化调节，DSB-1 是酵母 Spo11 辅助因子 Rec114 的同源物，由 PP4 磷酸酶和 ATR 激酶的相反活性控制。在 突变体中，DSB-1 的磷酸化增加与 DSB 形成减少相关，而防止 DSB-1 磷酸化则大大增加了减数分裂 DSB 的数量，无论是在 突变体还是在野生型背景中。 和其密切相关的同源物还拥有一个分化的 DSB-1 平行物，称为 DSB-2，并且 缺失已知会随着年龄的增长减少卵母细胞中的 DSB 形成。我们表明，随着年龄的增长和 DSB-2 的缺失，磷酸化的、因此失活的 DSB-1 形式的比例增加，而不可磷酸化的 DSB-1 挽救了 突变体中与年龄相关的 DSB 减少。这些结果表明，DSB-2 的进化部分是为了通过磷酸化来补偿 DSB-1 的失活，以维持老年动物中 DSB 的水平。我们的工作表明，PP4、ATR 和 DSB-2 与 DSB-1 协同作用，以促进整个生殖寿命中 DSB 水平的最佳化。
