Tahira T, Ishizaka Y, Itoh F, Sugimura T, Nagao M
Carcinogenesis Division, National Cancer Center Research Institute, Tokyo, Japan.
Oncogene. 1990 Jan;5(1):97-102.
The ret proto-oncogene expresses four major mRNA species of different lengths in human malignant cell lines and rat tissues. We isolated ret proto-oncogene cDNA clones from a cDNA library of a human neuroblastoma line, Nagai, which over-expressed these mRNAs. Four cDNA clones differing from each other in their 3' portions were analysed. The sequence of the region common to the cDNA clones is essentially identical to a reported cDNA sequence derived from THP-1 monocytic leukemia cells, that encodes a protein with characteristic features of receptor-type tyrosine kinase. From the 3' heterogeneity, two isoforms of the ret proto-oncogene product of 1072 and 1114 residues that differed from each other in their 9 and 51 C-terminal amino acids are predicted. Comparison of the structures of cDNA clones with that of the genomic clone showed that the 3' heterogeneity is produced by alternative polyadenylation and splicing of mRNA. Northern blot analysis using various fragments of cDNA indicated that the 4.5 kb, 3.9 kb and possibly 7.0 kb transcripts may encode a protein of 1072 residues, while the 6.0 kb transcript and a (minor) 4.6 kb transcript may encode a protein of 1114 residues.
原癌基因ret在人恶性细胞系和大鼠组织中表达四种不同长度的主要mRNA种类。我们从人神经母细胞瘤系Nagai的cDNA文库中分离出ret原癌基因cDNA克隆，该细胞系过度表达这些mRNA。对在其3'部分彼此不同的四个cDNA克隆进行了分析。cDNA克隆共有的区域序列与源自THP-1单核细胞白血病细胞的报道cDNA序列基本相同，该序列编码具有受体型酪氨酸激酶特征的蛋白质。根据3'异质性，预测了ret原癌基因产物的两种异构体，分别为1072个和1114个残基，它们在9个和51个C末端氨基酸上彼此不同。将cDNA克隆的结构与基因组克隆的结构进行比较表明，3'异质性是由mRNA的可变聚腺苷酸化和剪接产生的。使用cDNA的各种片段进行的Northern印迹分析表明，4.5kb、3.9kb以及可能的7.0kb转录本可能编码一个1072个残基的蛋白质，而6.0kb转录本和一个（少量的）4.6kb转录本可能编码一个1114个残基的蛋白质。
