Photoalkylated DNA and ultraviolet-irradiated DNA are incised at cytosines by endonuclease III.
Photoalkylated DNA and ultraviolet-irradiated DNA are incised at cytosines by endonuclease III.
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光烷基化 DNA 和紫外线照射 DNA 被核酸内切酶 III 在胞嘧啶处切割。
DOI：
10.1093/nar/14.16.6621
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发表时间：
1986
影响因子：
14.9
通讯作者：
Duker,NJ
中科院分区：
文献类型：
--
作者：
Weiss,RB;Duker,NJ
光烷基化，用异丙醇和过氧化二叔丁基紫外线照射DNA，引起各种碱基改变。这些包括8-（2-羟基-2-丙基）鸟嘌呤、8-（2-羟基-2-丙基）腺嘌呤和胸腺嘧啶二聚体。通过将超螺旋PM 2噬菌体DNA转化为切口形式来测定针对光烷基化DNA的大肠杆菌核酸内切酶。在缺乏核酸外切酶III活性的菌株BW 9109（xth-）和核酸外切酶III和核酸内切酶III均缺乏的菌株BW 434（xth-，nth-）的提取物之间比较酶活性。在双突变体中对底物光烷基化DNA的核酸内切酶水平低于仅缺乏核酸外切酶III的突变体中的活性的20%。在不存在异丙醇的情况下照射DNA底物不影响在任一菌株中的活性。通过聚丙烯酰胺凝胶电泳分析，鉴定了纯化的大肠杆菌核酸内切酶III切割DNA的位点为胞嘧啶，无论是在生物学上有意义的波长照射的DNA中还是在光烷基化的DNA中。8-（2-羟基-2-丙基）嘌呤、嘧啶二聚体、尿嘧啶和6-4′-（嘧啶-2 ′-酮）嘧啶都不是该酶的底物。
Photoalkylation, the ultraviolet irradiation of DNA with isopropanol and diteit-butylperoxide, causes a variety of base alterations. These include 8-(2-hydroxy-2-propyl)guanines, 8-(2-hydroxy-2-propyl)adenines and thymine dimers. AnE.coliendonuclease against photoalkylated DNA was assayed by conversion of superhelical PM2 phage DNA to the nicked form. Enzyme activities were compared between extracts of strain BW9109 (xth−), lacking exonuclease III activity, and strain BW434 (xth−,nth−), deficient in both exonuclease III and endonuclease III. The endonuclease level in the double mutant against substrate photoalkylated DNA was under 20% of the activity in the mutant lacking only exonuclease III. Irradiation of the DNA substrate in the absence of isopropanol did not affect the activity in either strain. Analysis by polyacrylamide gel electrophoresis identified the sites of DNA cleavage by purifiedE.coliendonuclease III as cytosines, both in DNA irradiated at biologically significant wavelengths and in photoalkylated DNA. Neither 8-(2-hydroxy-2-propyl)purines, pyrimidine dimers, uracils nor 6-4′-(pyrimidin-2′-one)pyrimidines were substrates for the enzyme.