Nei deficient Escherichia coli are sensitive to chromate and accumulate the oxidized guanine lesion spiroiminodihydantoin
Nei deficient Escherichia coli are sensitive to chromate and accumulate the oxidized guanine lesion spiroiminodihydantoin
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DOI：
10.1021/tx0501379
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发表时间：
2005-09-01
影响因子：
4.1
通讯作者：
Sugden, KD
中科院分区：
文献类型：
--
作者：
Hailer, MK;Slade, PG;Sugden, KD
研究了碱基切除修复（BER）缺陷型大肠杆菌（Escherichia coli）的生长抑制和氧化鸟嘌呤损伤形成。大肠杆菌）。与其匹配的野生型细胞系相比，唯一表现出铬酸盐显著生长抑制的BER缺陷型细菌菌株是Nei缺陷型（TK 3D 11）。高效液相色谱-电喷雾质谱联用分析表明，Nei缺陷型E.大肠杆菌在基因组DNA中积累了进一步氧化的鸟嘌呤损伤，螺亚氨基二乙内酰脲（Sp），其水平比野生型高出20倍。然而，在Nei缺陷型菌株中没有观察到Sp的推定中间体7，8-二氢-S-氧代-2 '-脱氧鸟苷（8-oxodG）的积累。MutM（-）/MutY（-）双缺失突变体缺乏识别和修复8-oxodG的BER酶，表明对铬酸盐不敏感，也没有相关的Sp积累增加。然而，MutM-/MutY-双缺失突变体在铬酸盐暴露后确实显示出与野生型和Nei缺陷型大肠杆菌相似的20倍8-oxodG积累。杆菌这些数据表明Nei BER酶对于细菌细胞系中Sp损伤的识别和修复是关键的，并且证明了特定BER酶对由铬酸盐形成的DNA损伤的保护作用。据我们所知，这些是第一个研究表明的形成和生物学意义的Sp病变的细胞系统。这项研究具有显着的机制和毒理学的影响，铬酸盐如何可能作为致癌的发起人，并建议特定的修复酶，可能会改善铬酸盐的致癌潜力的作用。
Growth inhibition and oxidized guanine lesion formation were studied in a number of base excision repair (BER) deficient Escherichia coli (E. coli) following chromate exposure. The only BER deficient bacterial strain that demonstrated significant growth inhibition by chromate, in comparison to its matched wild-type cell line, was the Nei deficient (TK3D11). HPLC coupled with electrospray ionization mass spectrometry showed that the Nei deficient E. coli accumulated the further oxidized guanine lesion, spiroiminodihydantoin (Sp), in genomic DNA at levels that were similar to 20-fold greater than its wild-type counterpart. However, no accumulation of the putative intermediate of Sp, 7,8-dihydro-S-oxo-2 '-deoxyguanosine (8-oxodG), was observed in the Nei deficient strain. A MutM(-)/MutY(-) double deletion mutant that was deficient in BER enzymes for the recognition and repair of 8-oxodG demonstrated no sensitivity toward chromate nor was there an associated increase in Sp accumulation over that of its wild type. However, the MutM-/MutY- double deletion mutant did show similar to 20-fold accumulation of 8-oxodG upon chromate exposure over that of the wild type and the Nei deficient E. coli. These data demonstrate that the Nei BER enzyme is critical for the recognition and repair of the Sp lesion in bacterial cell lines and demonstrates the protective effect of a specific BER enzyme on DNA lesions formed by chromate. To our knowledge, these are the first studies to show the formation and biological significance of the Sp lesion in a cellular system. This study has significant mechanistic and toxicological implications for how chromate may serve as an initiator of carcinogenesis and suggests a role for specific repair enzymes that may ameliorate the carcinogenic potential of chromate.