Sakumi K, Shiraishi A, Hayakawa H, Sekiguchi M
Department of Biochemistry, Kyushu University, Fukuoka, Japan.
Nucleic Acids Res. 1991 Oct 25;19(20):5597-601. doi: 10.1093/nar/19.20.5597.
cDNA for O6-methylguanine-DNA methyltransferase was isolated by screening rat liver cDNA libraries, using as a probe the human cDNA sequence for methyltransferase. The rat cDNA encodes a protein with 209 amino acid residues. The predicted amino acid sequence of the rat methyltransferase exhibits considerable homology with those of the human, yeast and bacterial enzymes, especially around putative methyl acceptor sites. When the cDNA was placed under control of the lac promoter and expressed in methyltransferase-deficient Escherichia coli (ada-, ogt-) cells, a characteristic methyltransferase protein was produced. The rat DNA methyltransferase thus expressed could complement the biological defects of the E. coli cell caused by lack of its own DNA methyltransferases; e.g. increased sensitivity to alkylating agents in terms of both cell death and mutation induction.
通过用甲基转移酶的人cDNA序列作为探针筛选大鼠肝脏cDNA文库，分离出了O6-甲基鸟嘌呤-DNA甲基转移酶的cDNA。大鼠cDNA编码一种含有209个氨基酸残基的蛋白质。预测的大鼠甲基转移酶氨基酸序列与人类、酵母和细菌酶的氨基酸序列具有相当高的同源性，尤其是在假定的甲基受体位点周围。当将该cDNA置于lac启动子的控制下并在缺乏甲基转移酶的大肠杆菌（ada-，ogt-）细胞中表达时，产生了一种特征性的甲基转移酶蛋白。如此表达的大鼠DNA甲基转移酶可以弥补大肠杆菌细胞因缺乏自身DNA甲基转移酶而导致的生物学缺陷；例如，在细胞死亡和突变诱导方面对烷化剂的敏感性增加。
