FORMATION AND STABILITY OF REPAIRABLE PYRIMIDINE PHOTOHYDRATES IN DNA
FORMATION AND STABILITY OF REPAIRABLE PYRIMIDINE PHOTOHYDRATES IN DNA
复制标题
DOI：
10.1021/bi00498a004
复制
发表时间：
1990-11-20
期刊：
影响因子：
2.9
通讯作者：
TEEBOR, GW
中科院分区：
文献类型：
--
作者：
BOORSTEIN, RJ;HILBERT, TP;TEEBOR, GW
溶液中聚（dG-dC）和聚（dA-dU）的紫外线照射产生嘧啶水合物，其被细菌和哺乳动物DNA糖基化修复[Boorstein等人（1989）Biochemistry 28，6164-6170]。大肠杆菌核酸内切酶III被用来定量的形成和稳定性，这些水合物的双链交替共聚物聚（dG-dC）和聚（dA-dU）。当在pH 8.0下用100 kJ/m2的254 nm光照射聚（dG-dC）时，2.2%的胞嘧啶残基转化为胞嘧啶水合物（6-羟基-5，6-二氢胞嘧啶），而0.09%转化为尿嘧啶水合物（6-羟基-5，6-二氢尿嘧啶）。为了测量这些产物的稳定性，聚（dG-dC）在UV照射后在溶液中孵育长达24小时。胞嘧啶水合物在4 ℃下稳定，在25、37和55 ℃下衰变，半衰期为75、25和6小时。在辐照的聚（dA-dU）中产生的尿嘧啶水合物在4 ℃和25 ℃下稳定，并且在37 ℃下以6小时的半衰期衰变，在55 ℃下以小于0.5小时的半衰期衰变。尿嘧啶水合物和尿嘧啶也形成在辐照聚（dG-dC）。这些实验表明，UV诱导的胞嘧啶水合物可以在DNA中持续延长的时间段，并且还经历脱氨基作用形成尿嘧啶水合物，尿嘧啶水合物进而经历脱水以产生尿嘧啶。这些光产物在DNA中的形成和稳定性可能促进了修复酶内切核酸酶III和类似的高等生物的DNA糖基化/内切核酸酶活性的进化发展，以及尿嘧啶-DNA糖基化的发展。
Ultraviolet irradiation of poly(dG-dC) and poly(dA-dU) in solution produces pyrimidine hydrates that are repaired by bacterial and mammalian DNA glycosylates [Boorstein et al. (1989) Biochemistry 28, 6164-6170]. Escherichia coli endonuclease III was used to quantitate the formation and stability of these hydrates in the double-stranded alternating copolymers poly(dG-dC) and poly(dA-dU). When poly(dG-dC) was irradiated with 100 kJ/m2 of 254-nm light at pH 8.0, 2.2% of the cytosine residues were converted to cytosine hydrate (6-hydroxy-5,6-dihydrocytosine) while 0.09% were converted to uracil hydrate (6-hydroxy-5,6-dihydrouracil). To measure the stability of these products, poly(dG-dC) was incubated in solution for up to 24 h after UV irradiation. Cytosine hydrate was stable at 4.degree.C and decayed at 25, 37, and 55.degree.C with half-lives of 75, 25, and 6 h. Uracil hydrate produced in irradiated poly(dA-dU) was stable at 4.degree.C and at 25.degree.C and decayed with a half-life of 6 h at 37.degree.C and less than 0.5 h at 55.degree.C. Uracil hydrate and uracil were also formed in irradiated poly(dG-dC). These experiments demonstrate that UV-induced cytosine hydrate may persist in DNA for prolonged time periods and also undergo deamination to uracil hydrate, which in turn undergoes dehydration to yield uracil. The formation and stability of these photoproducts in DNA may have promoted the evolutionary development of the repair enzyme endonuclease III and analogous DNA glycosylate/endonuclease activities of higher organisms, as well as the development of uracil-DNA glycosylate.