Kojima M, Morita T, Degawa M, Hashimoto Y, Tada M
Laboratory of Biochemistry, Aichi Cancer Center Research Institute, Nagoya, Japan.
Mutat Res. 1992 Jun;274(1):65-71. doi: 10.1016/0921-8777(92)90044-4.
DNA lesions produced in Escherichia coli AB2500 (uvrA) exposed to the carcinogen N-hydroxy-3-methoxy-4-aminoazobenzene (N-OH-3-MeO-AAB) or the noncarcinogen N-hydroxy-2-methoxy-4-aminoazobenzene (N-OH-2-MeO-AAB) were investigated by alkaline sucrose gradient sedimentation and 32P-postlabeling analysis. Alkali-labile sites appeared to be formed equally in cells treated with both aminoazobenzene derivatives. 32P-Postlabeling analysis revealed that the 3-MeO-AAB-DNA adduct level was 25-fold higher than that for 2-MeO-AAB-DNA adducts. In addition to major adducts, 4 minor spots were detected in N-OH-3-MeO-AAB-treated cells, while only one major adduct was found in N-OH-2-MeO-AAB-treated cells. The mutagenicities and cytotoxicities were also determined with E. coli with different repair capacities; we found that repair of 3-MeO-AAB damages is strongly dependent on the UVR repair system. Moreover, N-OH-3-MeO-AAB, but not N-OH-2-MeO-AAB, could induce recA and umuC gene expression, which was higher in uvrA strains than in the wild type.
通过碱性蔗糖梯度沉降法和³²P后标记分析法，研究了暴露于致癌物N-羟基-3-甲氧基-4-氨基偶氮苯（N-OH-3-MeO-AAB）或非致癌物N-羟基-2-甲氧基-4-氨基偶氮苯（N-OH-2-MeO-AAB）的大肠杆菌AB2500（uvrA）中产生的DNA损伤。在用两种氨基偶氮苯衍生物处理的细胞中，似乎均等地形成了碱不稳定位点。³²P后标记分析显示，3-MeO-AAB-DNA加合物水平比2-MeO-AAB-DNA加合物高25倍。除主要加合物外，在N-OH-3-MeO-AAB处理的细胞中检测到4个次要斑点，而在N-OH-2-MeO-AAB处理的细胞中仅发现1个主要加合物。还使用具有不同修复能力的大肠杆菌测定了致突变性和细胞毒性；我们发现3-MeO-AAB损伤的修复强烈依赖于UVR修复系统。此外，N-OH-3-MeO-AAB而非N-OH-2-MeO-AAB可诱导recA和umuC基因表达，uvrA菌株中的表达高于野生型。
