Sampathkumar Arivarasan, Zhong Chen, Tang Yuting, Fujita Yurika, Ito Masaru, Shinohara Akira
Institute for Protein Research, University of Osaka, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Sci Rep. 2024 Apr 25;14(1):9550. doi: 10.1038/s41598-024-60082-x.
DNA double-strand breaks (DSBs) activate DNA damage responses (DDRs) in both mitotic and meiotic cells. A single-stranded DNA (ssDNA) binding protein, Replication protein-A (RPA) binds to the ssDNA formed at DSBs to activate ATR/Mec1 kinase for the response. Meiotic DSBs induce homologous recombination monitored by a meiotic DDR called the recombination checkpoint that blocks the pachytene exit in meiotic prophase I. In this study, we further characterized the essential role of RPA in the maintenance of the recombination checkpoint during Saccharomyces cerevisiae meiosis. The depletion of an RPA subunit, Rfa1, in a recombination-defective dmc1 mutant, fully alleviates the pachytene arrest with the persistent unrepaired DSBs. RPA depletion decreases the activity of a meiosis-specific CHK2 homolog, Mek1 kinase, which in turn activates the Ndt80 transcriptional regulator for pachytene exit. These support the idea that RPA is a sensor of ssDNAs for the activation of meiotic DDR. Rfa1 depletion also accelerates the prophase I delay in the zip1 mutant defective in both chromosome synapsis and the recombination, consistent with the notion that the accumulation of ssDNAs rather than defective synapsis triggers prophase I delay in the zip1 mutant.
DNA双链断裂（DSBs）在有丝分裂和减数分裂细胞中都会激活DNA损伤反应（DDRs）。一种单链DNA（ssDNA）结合蛋白，即复制蛋白A（RPA），会与DSBs处形成的ssDNA结合，从而激活ATR/Mec1激酶以引发反应。减数分裂DSBs会诱导同源重组，该过程由一种名为重组检查点的减数分裂DDR监测，该检查点会在减数分裂前期I阻断粗线期退出。在本研究中，我们进一步阐明了RPA在酿酒酵母减数分裂过程中维持重组检查点的关键作用。在重组缺陷型dmc1突变体中，RPA亚基Rfa1的缺失完全缓解了粗线期停滞以及持续未修复的DSBs。RPA缺失会降低减数分裂特异性CHK2同源物Mek1激酶的活性，进而激活用于粗线期退出的Ndt80转录调节因子。这些结果支持了RPA是激活减数分裂DDR的ssDNA传感器这一观点。Rfa1缺失还会加速在染色体联会和重组均有缺陷的zip1突变体中的前期I延迟，这与ssDNA的积累而非缺陷联会引发zip1突变体前期I延迟的观点一致。
