Cloning of Drosophila gene which code for UV-damaged DNA binding protein

环丁烷嘧啶二聚体（CPDs）和嘧啶（6-4）嘧啶光产物（（6-4）光产物）是紫外光照射细胞产生的两大类细胞毒性致突变性和致癌性DNA光产物。光再激活现象，即通过同时或随后用近紫外线或可见光照射来减少紫外线辐射的致死和诱变效应，已在若干生物体中得到确认，在某些情况下，催化这一过程的酶已得到充分详细的描述。cpd是迄今为止所分析的光再激活酶的唯一已知底物，（6-4）光产物的酶光再激活尚未报道。使用凝胶移位法，我们已经确定了两种蛋白质因子（因子1和因子2），它们与紫外线照射的DNA特异性结合。纯化后，我们测定了每个因子的酶活性。因子2是光解酶（光活化cpd）的果蝇同源物。因子1是（6-4）光产物的光活化酶。这是在任何生物体中首次报道（6-4）光产物特有的光活化活性。

Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4) photoproducts) are the two major classes of cytotoxic mutagenic and carcinogenic DNA photoproducts produced by ultraviolet light irradiation of cells. The phenomenon of photoreactivation, the reduction of the lethal and mutagenic effects of ultraviolet radiation by simultaneous or subsequent irradiation with near ultraviolet or visible light, has been identified in several organisms and in some cases the enzymes that catalyze this process have been characterized in sufficient detail. CPDs are the only known substrate for the photoreactivating enzymes so far analyzed and enzymatic photoreactivation of (6-4) photoproducts has not yet been reported.Using gel shift assay we have identified two protein factors (Factor 1 and Factor 2) which bind specifically to UV-irradiated DNA. After purification we have determined the enzymatic activity of each factor.Factor 2 is a Drosophila homologue of photolyase (which photoreactivate CPDs). Factor 1 is a photoreactivating enzyme of (6-4) photoproduct. This is the first report of such photoreactivating activity specific for (6-4) photoproduct in any organism.