Duker N J, Weems K M
Department of Pathology, Temple University School of Medicine, Philadelphia, PA 19140.
Nucleic Acids Res. 1990 Apr 25;18(8):2007-10. doi: 10.1093/nar/18.8.2007.
Ultraviolet irradiation of DNA produces cytosine hydrate, released as a free base by E. coli endonuclease III. Cytosine hydrate excision was investigated by assaying photoproduct release from cytosine-radiolabeled, irradiated poly(dG-dC):poly(dG-dC). Conformational shifts between B-DNA and Z-DNA were affected by heating the polymer in either nickel chloride or cobaltous chloride, and were determined by circular dichroism. Rates of enzymic cytosine hydrate release did not differ between the different substrate conformations. Irradiation of left-handed poly(dG-dC):poly(dG-dC) resulted in cytosine hydrate formation. Therefore, neither formation nor enzymic excision of ultraviolet-induced cytosine hydrates are substantially affected by these DNA conformational states.
DNA的紫外线照射会产生胞嘧啶水合物，大肠杆菌内切酶III会将其作为游离碱基释放出来。通过检测从用放射性标记的胞嘧啶进行照射的聚（dG-dC）:聚（dG-dC）中释放的光产物，来研究胞嘧啶水合物的切除情况。在氯化镍或氯化钴中加热聚合物会影响B-DNA和Z-DNA之间的构象转变，这通过圆二色性来测定。不同底物构象之间酶促释放胞嘧啶水合物的速率没有差异。左旋聚（dG-dC）:聚（dG-dC）的照射导致了胞嘧啶水合物的形成。因此，紫外线诱导的胞嘧啶水合物的形成和酶促切除都不会受到这些DNA构象状态的显著影响。
