Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA.
Laboratory for Plant Molecular Biology, Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Serbia.
DNA Repair (Amst). 2018 Mar;63:47-55. doi: 10.1016/j.dnarep.2018.01.010. Epub 2018 Feb 2.
Cells maintain a small arsenal of resolving functions to process and eliminate complex DNA intermediates that result as a consequence of homologous recombination and distressed replication. Ordinarily the homologous recombination system serves as a high-fidelity mechanism to restore the integrity of a damaged genome, but in the absence of the appropriate resolving function it can turn DNA intermediates resulting from replication stress into pathological forms that are toxic to cells. Here we have investigated how the nucleases Mus81 and Gen1 and the helicase Blm contribute to survival after DNA damage or replication stress in Ustilago maydis cells with crippled yet homologous recombination-proficient forms of Brh2, the BRCA2 ortholog and primary Rad51 mediator. We found collaboration among the factors. Notable were three findings. First, the ability of Gen1 to rescue hydroxyurea sensitivity of dysfunctional Blm requires the absence of Mus81. Second, the response of mutants defective in Blm and Gen1 to hydroxyurea challenge is markedly similar suggesting cooperation of these factors in the same pathway. Third, the repair proficiency of Brh2 mutant variants deleted of its N-terminal DNA binding region requires not only Rad52 but also Gen1 and Mus81. We suggest these factors comprise a subpathway for channeling repair when Brh2 is compromised in its interplay with DNA.
细胞维持着一小部分的解决功能，以处理和消除同源重组和受损复制产生的复杂 DNA 中间体。通常情况下，同源重组系统是一种恢复受损基因组完整性的高保真机制，但在缺乏适当的解决功能的情况下，它会将复制应激产生的 DNA 中间体转化为对细胞有毒的病理性形式。在这里，我们研究了在 Ustilago maydis 细胞中，当 Brh2 的同源重组功能正常但形式受损时，核酸酶 Mus81 和 Gen1 以及解旋酶 Blm 如何在 DNA 损伤或复制应激后促进存活。我们发现这些因素之间存在协作。值得注意的有三个发现。首先，Gen1 拯救功能失调的 Blm 的羟基脲敏感性的能力需要 Mus81 的缺失。其次，Blm 和 Gen1 缺陷突变体对羟基脲挑战的反应非常相似，表明这些因素在同一途径中合作。第三，缺失其 N 端 DNA 结合区的 Brh2 突变体变体的修复效率不仅需要 Rad52，还需要 Gen1 和 Mus81。我们认为，当 Brh2 在与 DNA 的相互作用中受到干扰时，这些因素构成了一个用于引导修复的亚途径。
