Yuan Haiyan, Odiba Arome Solomon, Liao Guiyan, Zhou Ziteng, Fang Wenxia, Jin Cheng, Li Shaojun, Liu Xihui, Wang Bin
Department of Toxicology, School of Public Health, Guangxi Medical University, Nanning 530021, China.
Institute of Biological Sciences and Technology, Guangxi Academy of Sciences, Nanning 530007, China.
Biomolecules. 2025 May 23;15(6):755. doi: 10.3390/biom15060755.
The SMC-5/6 complex safeguards genome stability through the coordinated action of its core SMC proteins and associated NSE subunits. NSE-1 is a key component of the complex and is essential for DNA repair, yet it remains poorly characterized in . To further elucidate the functional mechanisms of NSE-1, we performed an EMS-based forward genetic screen in an reporter strain to identify mutants with defective NSE-1 expression or nuclear localization. We isolated three mutants; and , that display impaired NSE-1::GFP nuclear localization. SNP mapping and whole-genome sequencing revealed three novel alleles: two truncations, alleles (C587*) and (Q655*), and one missense variant, (Y975D), each altering a highly conserved residue in the SMC domain. All three mutants exhibited significantly reduced brood size, progeny viability, and slightly elevated male percentages. Phenotypic characterization revealed that the truncations completely abrogate NSE-1::GFP nuclear localization, whereas the missense allele causes stage-dependent, partial mislocalization. Functional assays further demonstrated allele-specific and developmental stage-dependent hypersensitivities to DNA-damaging agents (MMS, HU, and cisplatin). These separation-of-function alleles underscore the importance of domains and conserved residues in complex integrity and genome maintenance, and provide powerful genetic tools to dissect SMC-5/6 functions in vivo.
SMC-5/6复合物通过其核心SMC蛋白和相关NSE亚基的协同作用来维护基因组稳定性。NSE-1是该复合物的关键组分，对DNA修复至关重要，但在……中其特征仍了解甚少。为了进一步阐明NSE-1的功能机制，我们在一个……报告菌株中进行了基于EMS的正向遗传筛选，以鉴定NSE-1表达或核定位有缺陷的突变体。我们分离出三个突变体；……和……，它们表现出NSE-1::GFP核定位受损。SNP定位和全基因组测序揭示了三个新的……等位基因：两个截短突变，等位基因……（C587*）和……（Q655*），以及一个错义变体……（Y975D），每个都改变了SMC结构域中一个高度保守的残基。所有三个突变体的产卵量、后代活力均显著降低，雄性比例略有升高。表型特征表明，截短突变完全消除了NSE-1::GFP的核定位，而错义等位基因导致阶段依赖性的部分定位错误。功能分析进一步证明了等位基因特异性和发育阶段依赖性对DNA损伤剂（MMS、HU和顺铂）的超敏感性。这些功能分离的……等位基因强调了结构域和保守残基在复合物完整性和基因组维持中的重要性，并提供了强大的遗传工具来剖析SMC-5/6在体内的功能。
