Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, 400084, India.
Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, 400076, India.
Appl Microbiol Biotechnol. 2015 Nov;99(22):9761-9. doi: 10.1007/s00253-015-6808-6. Epub 2015 Jul 23.
Deinococcus radiodurans displays compromised radioresistance in the presence of guanine quadruplex (G4)-binding drugs (G4 drugs). Genome-wide scanning showed islands of guanine runs (G-motif) in the upstream regions of coding sequences as well as in the structural regions of many genes, indicating a role for G4 DNA in the regulation of genome functions in this bacterium. G-motifs present upstream to some of the DNA damage-responsive genes like lexA, pprI, recF, recQ, mutL and radA were synthesized, and the formation of G4 DNA structures was probed in vitro. The G-motifs present at the 67th position upstream to recQ and at the 121st position upstream to mutL produced parallel and mixed G4 DNA structures, respectively. Expression of β-galactosidase under recQ and mutL promoters containing respective G-motifs was inhibited by G4 drugs under normal growth conditions in D. radiodurans. However, when such cells were exposed to γ radiation, mutL promoter activity was stimulated while recQ promoter activity was inhibited in the presence of G4 drugs. Deletion of the G-motif from the recQ promoter could relax it from G4 drug repression. D. radiodurans cells treated with G4 drug showed reduction in recQ expression and γ radiation resistance, indicating an involvement of G4 DNA in the radioresistance of this bacterium. These results suggest that G-motifs from D. radiodurans genome form different types of G4 DNA structures at least in vitro, and the recQ and mutL promoters seem to be differentially regulated at the levels of G4 DNA structures.
耐辐射球菌在存在鸟嘌呤四链体 (G4) 结合药物 (G4 药物) 的情况下显示出辐射抗性受损。全基因组扫描显示，在编码序列的上游区域以及许多基因的结构区域存在鸟嘌呤重复 (G-基序)，表明 G4 DNA 在调节该细菌的基因组功能方面发挥作用。合成了一些 DNA 损伤响应基因如 lexA、pprI、recF、recQ、mutL 和 radA 的上游存在 G-基序的基因，并在体外探测 G4 DNA 结构的形成。recQ 上游第 67 位和 mutL 上游第 121 位存在的 G-基序分别产生平行和混合 G4 DNA 结构。在正常生长条件下，含有各自 G-基序的 recQ 和 mutL 启动子表达的 β-半乳糖苷酶受到 G4 药物的抑制。然而，当这些细胞暴露于 γ 射线时，在 G4 药物存在下，mutL 启动子活性被刺激，而 recQ 启动子活性被抑制。从 recQ 启动子中删除 G-基序可以使其免受 G4 药物的抑制。用 G4 药物处理的耐辐射球菌细胞显示 recQ 表达减少和 γ 辐射抗性降低，表明 G4 DNA 参与了该细菌的辐射抗性。这些结果表明，耐辐射球菌基因组中的 G-基序至少在体外形成不同类型的 G4 DNA 结构，并且 recQ 和 mutL 启动子似乎在 G4 DNA 结构水平上受到差异调节。
