耐辐射异常球菌磷酸戊糖途径对DNA损伤修复的影响

Effects of Pentose Phosphate Pathway on DNA Damage Repair in Deinococcus radiodurans

耐辐射异常球菌(D.radiodurans)超强的辐照抗性归因于其高效的DNA损伤修复系统,磷酸戊糖途径(PPP)作为细胞各种糖类代谢枢纽,是合成核苷酸和核酸所需的核糖以及生成细胞还原力(NADPH)的重要途径。为探究D.radiodurans R1中PPP对DNA损伤修复的影响,本研究敲除PPP中编码限速酶葡萄糖-6-磷酸脱氢酶(G6PD)的基因zwf,比较UV辐照后突变株Δzwf与野生型D.radiodurans的生理生化差异。结果表明,zwf突变导致菌株对UV辐照敏感;UV辐照后Δzwf胞内NADPH、D-核糖、核苷酸合成前体IMP、UMP含量明显降低;葡萄糖酸-δ-内酯及D-核糖能完全和部分恢复Δzwf的UV辐射抗性。综上可知PPP通过提供DNA损伤修复原料及还原力,在DNA损伤修复过程中起着重要作用。本研究结果为DNA损伤修复机理提供参考。

D. radiodurans is one of the most radiation-resistant organisms known till today. The radiation-resistance of D. radiodurans is due to its efficient DNA-repair system. Pentose phosphate pathway acts as the centre of carbon metabolism generating nucleotide,NDAPH and the ribose needed for synthesizing nucleic acid. In order to explore the impact of PPP on DNA-repair system in D. radiodurans R1,the zwf gene which encodes the glucose- 6- phosphate dehydrogenase（ G6PD） were knocked out and the biophysical and biochemical difference between Δzwf and D.radiodurans R1 under UV radiation were analyzed. The lack of G6 PD blocks the PPP in Δzwf. The results showed that the mutant Δzwf became more sensitive to UV radiation,and the sensitive phenotype can be fully and partially compensated with gluconic acid-lactone or D-Ribose. Additionally,the content of metabolites,such as D-ribose,NADPH,IMP and UMP,in Δzwf has decreased. The current results suggest that PPP provides substrates and energy for the DNA-repair system in D. radiodurans R1 and plays an irreplaceable role in the UV radiation resistance. The result of the study provides reference for the mechanism of DNA damage reparations.