State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
Protein Cell. 2010 May;1(5):478-90. doi: 10.1007/s13238-010-0058-2. Epub 2010 Jun 4.
RecQ5 in mammalian cells has been suggested to suppress inappropriate homologous recombination. However, the specific pathway(s) in which it is involved and the underlining mechanism(s) remain poorly understood. We took advantage of genetic tools in Drosophila to investigate how Drosophila RecQ5 (dRecQ5) functions in vivo in homologous recombination-mediated double strand break (DSB) repair. We generated null alleles of dRecQ5 using the targeted recombination technique. The mutant animals are homozygous viable, but with growth retardation during development. The mutants are sensitive to both exogenous DSB-inducing treatment, such as gamma-irradiation, and endogenously induced double strand breaks (DSBs) by I-Sce I endonuclease. In the absence of dRecQ5, single strand annealing (SSA)-mediated DSB repair is compromised with compensatory increases in either inter-homologous gene conversion, or non-homologous end joining (NHEJ) when inter-chromosomal homologous sequence is unavailable. Loss of function of dRecQ5 also leads to genome instability in loss of heterozygosity (LOH) assays. Together, our data demonstrate that dRecQ5 functions in SSA-mediated DSB repair to achieve its full efficiency and in suppression of LOH in Drosophila.
在哺乳动物细胞中，RecQ5 被认为可以抑制不适当的同源重组。然而，其涉及的具体途径和潜在的机制仍知之甚少。我们利用果蝇中的遗传工具，研究了果蝇 RecQ5（dRecQ5）在体内同源重组介导的双链断裂（DSB）修复中是如何发挥作用的。我们使用靶向重组技术生成了 dRecQ5 的缺失突变体。这些突变体动物纯合子是存活的，但在发育过程中生长迟缓。这些突变体对外部 DSB 诱导处理（如γ射线照射）以及由 I-Sce I 内切酶诱导的内源性双链断裂（DSBs）都很敏感。在缺乏 dRecQ5 的情况下，单链退火（SSA）介导的 DSB 修复受到影响，当染色体间同源序列不可用时，要么通过同源基因转换进行补偿，要么通过非同源末端连接（NHEJ）进行补偿。dRecQ5 的功能丧失也会导致杂合性丢失（LOH）测定中的基因组不稳定性。总之，我们的数据表明，dRecQ5 在 SSA 介导的 DSB 修复中发挥作用，以实现其最大效率，并抑制果蝇中的 LOH。
