Hirschfeld S, Levine A S, Ozato K, Protić M
Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Mol Cell Biol. 1990 May;10(5):2041-8. doi: 10.1128/mcb.10.5.2041-2048.1990.
Using a DNA band shift assay, we have identified a DNA-binding protein complex in primate cells which is present constitutively and has a high affinity for UV-irradiated, double-stranded DNA. Cells pretreated with UV light, mitomycin C, or aphidicolin have higher levels of this damage-specific DNA-binding protein complex, suggesting that the signal for induction can either be damage to the DNA or interference with cellular DNA replication. Physiochemical modifications of the DNA and competition analysis with defined substrates suggest that the most probable target site for the damage-specific DNA-binding protein complex is a 6-4'-(pyrimidine-2'-one)-pyrimidine dimer: specific binding could not be detected with probes which contain -TT- cyclobutane dimers, and damage-specific DNA binding did not decrease after photoreactivation of UV-irradiated DNA. This damage-specific DNA-binding protein complex is the first such inducible protein complex identified in primate cells. Cells from patients with the sun-sensitive cancer-prone disease, xeroderma pigmentosum (group E), are lacking both the constitutive and the induced damage-specific DNA-binding activities. These findings suggest a possible role for this DNA-binding protein complex in lesion recognition and DNA repair of UV-light-induced photoproducts.
通过DNA条带迁移分析，我们在灵长类细胞中鉴定出一种DNA结合蛋白复合物，该复合物组成性存在，并且对紫外线照射的双链DNA具有高亲和力。用紫外线、丝裂霉素C或阿非迪霉素预处理的细胞中，这种损伤特异性DNA结合蛋白复合物的水平更高，这表明诱导信号可能是DNA损伤或对细胞DNA复制的干扰。DNA的物理化学修饰以及与特定底物的竞争分析表明，损伤特异性DNA结合蛋白复合物最可能的靶位点是6-4'-（嘧啶-2'-酮）-嘧啶二聚体：含有-TT-环丁烷二聚体的探针无法检测到特异性结合，紫外线照射的DNA光复活后损伤特异性DNA结合并未降低。这种损伤特异性DNA结合蛋白复合物是在灵长类细胞中鉴定出的首个此类可诱导蛋白复合物。患有对阳光敏感且易患癌症的疾病——着色性干皮病（E组）的患者的细胞，既缺乏组成性的也缺乏诱导性的损伤特异性DNA结合活性。这些发现表明这种DNA结合蛋白复合物在紫外线诱导的光产物的损伤识别和DNA修复中可能发挥作用。
