Laspia M F, Wallace S S
Department of Microbiology, New York Medical College, Valhalla 10595.
J Bacteriol. 1988 Aug;170(8):3359-66. doi: 10.1128/jb.170.8.3359-3366.1988.
The genetic requirements for the excision repair of thymine glycols, urea residues, and apurinic (AP) sites were examined by measuring the survival in Escherichia coli mutants of phi X174 replicative form (RF) I transfecting DNA containing selectively introduced lesions. phi X RF I DNA containing thymine glycols was inactivated at a greater rate in mutants deficient in endonuclease III (nth) than in wild-type hosts, suggesting that endonuclease III is involved in the repair of thymine glycols in vivo. phi X RF I DNA containing thymine glycols was also inactivated at a greater rate in mutants that were deficient in both exonuclease III and endonuclease IV (xth nfo) than in wild-type hosts, suggesting that a class II AP endonuclease is required for the in vivo processing of thymine glycols. phi X duplex-transfecting DNA containing urea residues or AP sites was inactivated at a greater rate in xth nfo double mutants than in wild-type, but not single-mutant, hosts, suggesting that exonuclease III or endonuclease IV is required for the repair of these damages and that either activity can substitute for the other. These data are in agreement with the known in vitro substrate specificities of endonuclease III, exonuclease III, and endonuclease IV.
通过检测含有选择性引入损伤的φX174复制型（RF）I转染DNA在大肠杆菌突变体中的存活率，研究了胸腺嘧啶乙二醇、尿素残基和脱嘌呤（AP）位点切除修复的遗传要求。含有胸腺嘧啶乙二醇的φX RF I DNA在缺乏内切核酸酶III（nth）的突变体中比在野生型宿主中以更高的速率失活，这表明内切核酸酶III参与体内胸腺嘧啶乙二醇的修复。含有胸腺嘧啶乙二醇的φX RF I DNA在同时缺乏外切核酸酶III和内切核酸酶IV（xth nfo）的突变体中也比在野生型宿主中以更高的速率失活，这表明II类AP内切核酸酶是体内处理胸腺嘧啶乙二醇所必需的。含有尿素残基或AP位点的φX双链转染DNA在xth nfo双突变体中比在野生型宿主中以更高的速率失活，但在单突变体宿主中则不然，这表明外切核酸酶III或内切核酸酶IV是修复这些损伤所必需的，并且任何一种活性都可以替代另一种。这些数据与内切核酸酶III、外切核酸酶III和内切核酸酶IV已知的体外底物特异性一致。
