Koiwai O, Yokota T, Kageyama T, Hirose T, Yoshida S, Arai K
Nucleic Acids Res. 1986 Jul 25;14(14):5777-92. doi: 10.1093/nar/14.14.5777.
We have isolated nearly full-length cDNA clones of terminal deoxynucleotidyltransferase (TdT) from calf thymus and mouse lymphoma cDNA libraries. The libraries were constructed using the pcD vector system which permits the expression of cDNA inserts in mammalian cells. The bovine TdT cDNA clone contains an open reading frame coding for 520 amino acids, Mr 59,678. The mouse TdT cDNA clone contains an open reading frame of 1,587 bp, whose translated cDNA encodes a 60,004 dalton protein. The mouse TdT cDNA clone contains 60 bp in the 3' end region of the coding sequence not found in the bovine TdT cDNA sequence, otherwise, the clones share about 80% homology. A possible nuclear-localization-sequence (Pro-Arg-Lys-Lys-Arg-Pro-Arg) was conserved in the N-terminal region in the mouse and bovine cDNA clones. Bovine and mouse cDNAs transfected into COS7 monkey fibroblasts directed the synthesis of enzymatically active protein of Mr 60,000 which was detected immunologically using polyclonal rabbit antibody against bovine TdT. Bovine TdT expressed in COS7 cells by nearly full-length cDNA clone was localized in the nucleus and the translational product of pOK103 lacking the nuclear-localization-sequence was localized in the cytoplasm.
我们从小牛胸腺和小鼠淋巴瘤cDNA文库中分离出了末端脱氧核苷酸转移酶（TdT）的近全长cDNA克隆。这些文库是使用pcD载体系统构建的，该系统允许cDNA插入片段在哺乳动物细胞中表达。牛TdT cDNA克隆包含一个编码520个氨基酸、分子量为59,678的开放阅读框。小鼠TdT cDNA克隆包含一个1587 bp的开放阅读框，其翻译后的cDNA编码一种60,004道尔顿的蛋白质。小鼠TdT cDNA克隆在编码序列的3'末端区域含有60 bp，这在牛TdT cDNA序列中未发现，否则，这些克隆具有约80%的同源性。一个可能的核定位序列（Pro-Arg-Lys-Lys-Arg-Pro-Arg）在小鼠和牛的cDNA克隆的N末端区域中是保守的。转染到COS7猴成纤维细胞中的牛和小鼠cDNA指导合成了分子量为60,000的具有酶活性的蛋白质，使用针对牛TdT的多克隆兔抗体通过免疫方法检测到了该蛋白质。通过近全长cDNA克隆在COS7细胞中表达的牛TdT定位于细胞核，而缺乏核定位序列的pOK103的翻译产物定位于细胞质。
