Spek E J, Wright T L, Stitt M S, Taghizadeh N R, Tannenbaum S R, Marinus M G, Engelward B P
Division of Bioengineering and Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Bacteriol. 2001 Jan;183(1):131-8. doi: 10.1128/JB.183.1.131-138.2001.
Nitric oxide (NO(.)) is critical to numerous biological processes, including signal transduction and macrophage-mediated immunity. In this study, we have explored the biological effects of NO(.)-induced DNA damage on Escherichia coli. The relative importance of base excision repair, nucleotide excision repair (NER), and recombinational repair in preventing NO(.)-induced toxicity was determined. E. coli strains lacking either NER or DNA glycosylases (including those that repair alkylation damage [alkA tag strain], oxidative damage [fpg nei nth strain], and deaminated cytosine [ung strain]) showed essentially wild-type levels of NO(.) resistance. However, apyrimidinic/apurinic (AP) endonuclease-deficient cells (xth nfo strain) were very sensitive to killing by NO(.), which indicates that normal processing of abasic sites is critical for defense against NO(.). In addition, recA mutant cells were exquisitely sensitive to NO(.)-induced killing. Both SOS-deficient (lexA3) and Holliday junction resolvase-deficient (ruvC) cells were very sensitive to NO(.), indicating that both SOS and recombinational repair play important roles in defense against NO(.). Furthermore, strains specifically lacking double-strand end repair (recBCD strains) were very sensitive to NO(.), which suggests that NO(.) exposure leads to the formation of double-strand ends. One consequence of these double-strand ends is that NO(.) induces homologous recombination at a genetically engineered substrate. Taken together, it is now clear that, in addition to the known point mutagenic effects of NO(.), it is also important to consider recombination events among the spectrum of genetic changes that NO(. ) can induce. Furthermore, the importance of recombinational repair for cellular survival of NO(.) exposure reveals a potential susceptibility factor for invading microbes.
一氧化氮（NO(.)）对众多生物过程至关重要，包括信号转导和巨噬细胞介导的免疫。在本研究中，我们探讨了NO(.)诱导的DNA损伤对大肠杆菌的生物学效应。确定了碱基切除修复、核苷酸切除修复（NER）和重组修复在预防NO(.)诱导的毒性中的相对重要性。缺乏NER或DNA糖基化酶（包括修复烷基化损伤的酶[alkA标签菌株]、氧化损伤的酶[fpg nei nth菌株]和脱氨基胞嘧啶的酶[ung菌株]）的大肠杆菌菌株显示出基本野生型水平的NO(.)抗性。然而，无嘧啶/无嘌呤（AP）内切酶缺陷细胞（xth nfo菌株）对NO(.)杀伤非常敏感，这表明无碱基位点的正常处理对于抵御NO(.)至关重要。此外，recA突变细胞对NO(.)诱导的杀伤极为敏感。SOS缺陷（lexA3）和霍利迪连接解离酶缺陷（ruvC）细胞对NO(.)都非常敏感，表明SOS和重组修复在抵御NO(.)中都发挥重要作用。此外，特别缺乏双链末端修复的菌株（recBCD菌株）对NO(.)非常敏感，这表明NO(.)暴露会导致双链末端的形成。这些双链末端的一个后果是NO(.)在基因工程底物上诱导同源重组。综上所述，现在很清楚，除了NO(.)已知的点突变效应外，在NO(.)可诱导的一系列遗传变化中考虑重组事件也很重要。此外，重组修复对NO(.)暴露后细胞存活的重要性揭示了入侵微生物的一个潜在易感因素。
