Gu Yanchao, Yang Yantao, Kou Chunhua, Peng Ying, Yang Wenguang, Zhang Jiayu, Jin Han, Han Xiaoru, Wang Yao, Shen Xihui
State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.
Suzhou XinBio Co., Ltd., Suzhou, Jiangsu, China.
Front Microbiol. 2024 Apr 18;15:1362880. doi: 10.3389/fmicb.2024.1362880. eCollection 2024.
Cyanobacteria, which have a photoautotrophic lifestyle, are threatened by ultraviolet solar rays and the reactive oxygen species generated during photosynthesis. They can adapt to environmental conditions primarily because of their DNA damage response and repair mechanisms, notably an efficient homologous recombination repair system. However, research on double-strand break (DSB) repair pathways, including the Holliday junction (HJ) resolution process, in sp. PCC6803 is limited. Here, we report that SynRuvC from cyanobacteria sp. PCC6803 has classical HJ resolution activity. We investigated the structural specificity, sequence preference, and biochemical properties of SynRuvC. SynRuvC strongly preferred Mn as a cofactor, and its cleavage site predominantly resides within the 5'-TG↓(G/A)-3' sequence. Interestingly, novel flap endonuclease and replication fork intermediate cleavage activities of SynRuvC were also determined, which distinguish it from other reported RuvCs. To explore the effect of SynRuvC on cell viability, we constructed a knockdown mutant and an overexpression strain of sp. PCC6803 ( and ) and assessed their survival under a variety of conditions. Knockdown of increased the sensitivity of cells to MMS, HU, and HO. The findings suggest that a novel RuvC family HJ resolvase SynRuvC is important in a variety of DNA repair processes and stress resistance in sp. PCC6803.
蓝藻具有光合自养的生活方式，受到太阳紫外线和光合作用过程中产生的活性氧的威胁。它们能够适应环境条件主要是因为其DNA损伤应答和修复机制，特别是高效的同源重组修复系统。然而，关于集胞藻PCC6803中双链断裂（DSB）修复途径，包括霍利迪连接体（HJ）拆分过程的研究有限。在此，我们报道来自集胞藻PCC6803的SynRuvC具有典型的HJ拆分活性。我们研究了SynRuvC的结构特异性、序列偏好性和生化特性。SynRuvC强烈偏好锰作为辅因子，其切割位点主要位于5'-TG↓(G/A)-3'序列内。有趣的是，还确定了SynRuvC新的瓣状核酸内切酶和复制叉中间体切割活性，这使其有别于其他已报道的RuvC。为了探究SynRuvC对细胞活力的影响，我们构建了集胞藻PCC6803（ 和 ）的敲低突变体和过表达菌株，并评估了它们在各种条件下的存活率。敲低 会增加细胞对甲基磺酸甲酯（MMS）、羟基脲（HU）和过氧化氢（HO）的敏感性。这些发现表明，一种新的RuvC家族HJ拆分酶SynRuvC在集胞藻PCC6803的多种DNA修复过程和抗逆性中起着重要作用。
