Kim Soonjoung, Yamada Shintaro, Li Tao, Canasto-Chibuque Claudia, Kim Jun Hyun, Marcet-Ortega Marina, Xu Jiaqi, Eng Diana Y, Feeney Laura, Petrini John H J, Keeney Scott
Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
Department of Microbiology and Immunology, Institute for Immunology and Immunological Diseases, Yonsei University College of Medicine, Seoul, Korea.
Nat Commun. 2025 Apr 16;16(1):3613. doi: 10.1038/s41467-025-57928-x.
Nucleolytic resection of DNA ends is critical for homologous recombination, but its mechanism is not fully understood, particularly in mammalian meiosis. Here we examine roles of the conserved MRN complex (MRE11, RAD50, and NBS1) through genome-wide analysis of meiotic resection during spermatogenesis in mice with various MRN mutations, including several that cause chromosomal instability in humans. Meiotic DSBs form at elevated levels but remain unresected if Mre11 is conditionally deleted, thus MRN is required for both resection initiation and regulation of DSB numbers. Resection lengths are reduced to varying degrees in MRN hypomorphs or if MRE11 nuclease activity is attenuated in a conditional nuclease-dead Mre11 model. These findings unexpectedly establish that MRN is needed for longer-range extension of resection beyond that carried out by the orthologous proteins in budding yeast meiosis. Finally, resection defects are additively worsened by combining MRN and Exo1 mutations, and mice that are unable to initiate resection or have greatly curtailed resection lengths experience catastrophic spermatogenic failure. Our results elucidate MRN roles in meiotic DSB end processing and establish the importance of resection for mammalian meiosis.
DNA末端的核酸酶切对于同源重组至关重要，但其机制尚未完全阐明，尤其是在哺乳动物减数分裂过程中。在此，我们通过对具有各种MRN突变（包括几种导致人类染色体不稳定的突变）的小鼠精子发生过程中的减数分裂切除进行全基因组分析，研究了保守的MRN复合物（MRE11、RAD50和NBS1）的作用。如果Mre11被条件性敲除，减数分裂双链断裂（DSB）水平会升高，但仍未被切除，因此MRN对于切除起始和DSB数量的调节都是必需的。在MRN低表达型小鼠中，或者在条件性核酸酶失活的Mre11模型中如果MRE11核酸酶活性减弱，切除长度会不同程度地缩短。这些发现意外地表明，与芽殖酵母减数分裂中的直系同源蛋白相比，MRN对于切除的更长距离延伸是必需的。最后，将MRN和Exo1突变结合会使切除缺陷累加性恶化，无法起始切除或切除长度大幅缩短的小鼠会经历灾难性的精子发生失败。我们的结果阐明了MRN在减数分裂DSB末端加工中的作用，并确立了切除对哺乳动物减数分裂的重要性。
