Elucidation of mechanisms ensuring optimal double-strand break number in meiotic cells

在本财年，我们继续研究通过光调节DSB-1蛋白来控制减数分裂双链断裂(DSB)的机制。我们发现，将DSB-1中的单个丝氨酸残基S186突变为丙氨酸，会导致高活性DSB的形成，即使在没有DSB-2蛋白的情况下也是如此。正常情况下，DSB-2的丢失会导致由于DSB的丢失而导致胚胎高度丧失活力。由于DSB-2的丢失可以很容易地挽救，我们推测它可能是基因组长期稳定所必需的。因此，我们对DSB-1非磷酸化突变系进行了全基因组长读测序，这些突变系经历了超过50代的高DSB水平。虽然对这一序列信息的分析仍在进行中，但已分离出具有自发突变和自发四倍体的个体突变动物。由于在野生型动物中从未观察到自发的四倍体，因此在非磷酸化的DSB-1突变动物中基因组变得不太稳定是合理的。我们试图通过磷酸特异性抗体的产生或质谱学直接证明DSB-1的磷酸化还没有成功；然而，我们现在已经完成了具有完全活性的旗帜标记的DSB-1等位基因的构建，该等位基因在蛋白质印迹中非常干净；该试剂应该对我们进一步的DSB-1特征的研究有很大的帮助。

We have continued to address the mechanisms of meiotic double-strand break (DSB) control by phosphoregulation of the protein DSB-1 in this fiscal year.We found that mutating a single serine residue in DSB-1, S186, to alanine, leads to hyperactive DSB formation, even in the absence of the protein DSB-2. Loss of DSB-2 norally leads to high embryonic inviability due to loss of DSBs. Since loss of DSB-2 can be rescued so easily, we reasoned that it might be required for long-term genome stability. We therefore have performed whole-genome long-read sequencing on DSB-1 non-phosphorylatable mutant lines that have been experiencing high DSB levels for over 50 generations. While analysis of this sequence information is still in progress, individual mutant animals have been isolated with spontaneous mutations and spontaneous tetraploidization. Since spontaneous tetraploidization is never observed in wild-type animals, it is plausible that the genome has become less stable in the non-phosphorylatable DSB-1 mutant animals.Our attempts to directly demonstrate phosphorylation of DSB-1 by phosphospecific antibody production or mass spectrometry have not yet been successful; however, we have now completed construction of a FLAG-tagged DSB-1 allele with full viability that is very clean on a western blot; this reagent should greatly aid in our further efforts to characterize DSB-1.