Merigliano Chiara, Ryu Taehyun, Cibulka Jakub, Rawal Chetan C, See Colby D, Mitra Anik, Reynolds Trevor W, Butova Nadejda L, Caridi Christopher P, Li Xiao, Wang Jeff, Deng Changfeng, Chenoweth David M, Sung Patrick, Capelson Maya, Krejčí Lumír, Chiolo Irene
Department of Biological Sciences, Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089, USA.
Department of Biological Sciences, Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
Mol Cell. 2025 Jun 19;85(12):2355-2373.e11. doi: 10.1016/j.molcel.2025.05.012. Epub 2025 Jun 5.
Phase separation forms membraneless compartments, including heterochromatin "domains" and repair foci. Pericentromeric heterochromatin mostly comprises repeated sequences prone to aberrant recombination. In Drosophila cells, "safe" homologous recombination (HR) repair of these sequences requires their relocalization to the nuclear periphery before Rad51 recruitment and strand invasion. How this mobilization initiates is unknown, and the contribution of phase separation is unclear. Here, we show that Nup98 nucleoporin is recruited to repair sites before relocalization by Sec13 or Nup88, and downstream of the Smc5/6 complex and heterochromatin protein 1 (HP1). Remarkably, Nup98 condensates are immiscible with HP1 condensates, and they are required and sufficient to mobilize repair sites and exclude Rad51, thus preventing aberrant recombination while promoting HR repair. Disrupting this pathway results in heterochromatin repair defects and widespread chromosome rearrangements, revealing an "off-pore" role for nucleoporins and phase separation in nuclear dynamics and genome integrity in a multicellular eukaryote.
相分离形成无膜区室，包括异染色质“结构域”和修复灶。着丝粒周围异染色质大多由易于发生异常重组的重复序列组成。在果蝇细胞中，这些序列的“安全”同源重组（HR）修复需要在Rad51募集和链侵入之前将它们重新定位到核周。这种动员如何启动尚不清楚，相分离的作用也不明确。在这里，我们表明核孔蛋白Nup98在通过Sec13或Nup88重新定位之前被募集到修复位点，并且在Smc5/6复合体和异染色质蛋白1（HP1）的下游。值得注意的是，Nup98凝聚物与HP1凝聚物互不相溶，它们对于动员修复位点和排除Rad51是必需且充分的，从而在促进HR修复的同时防止异常重组。破坏这一途径会导致异染色质修复缺陷和广泛的染色体重排，揭示了核孔蛋白在多细胞真核生物的核动力学和基因组完整性中的“孔外”作用以及相分离的作用。
