Lomedico P T, Rosenthal N, Kolodner R, Efstratiadis A, Gilbert W
Ann N Y Acad Sci. 1980;343:425-32. doi: 10.1111/j.1749-6632.1980.tb47271.x.
In rat there are two nonallelic insulins, I and II. We have cloned and sequenced double stranded cDNA copies of both preproinsulin mRNA I and II. Using the cloned sequence as probe, we established by the Southern blotting technique a restriction map of the two chromosomal genes. This map indicates that an intron exists within the insulin II gene. To examine this in more detail, we have isolated both genes from a library of rat DNA cloned in phage lambda. Restriction endonuclease analysis and direct DNA sequencing revealed that gene II contains two introns: a 490 base pair intron between the region encoding amino acids 38 and 39 of proinsulin, and a 119 base pair intron, which is 17 base pairs upstream from the initiation codon. Gene I is not interrupted within the protein coding region, but possesses an intron homologous to the 119 base pair intron of insulin II. We are studying the structure of insulin genes from other species to determine if the 490 base pair intron was lost or inserted in the duplicated gene. We have identified nuclear RNA molecules larger than preproinsulin mRNA which contain the transcribed intronic sequences. These molecules represent a new precursor in insulin biosynthesis.
在大鼠中存在两种非等位胰岛素，即胰岛素I和胰岛素II。我们已经克隆并测序了胰岛素原mRNA I和II的双链cDNA拷贝。以克隆的序列为探针，我们通过Southern印迹技术建立了这两个染色体基因的限制性图谱。该图谱表明胰岛素II基因内存在一个内含子。为了更详细地研究这一点，我们从克隆于噬菌体λ的大鼠DNA文库中分离出了这两个基因。限制性内切酶分析和直接DNA测序表明，基因II含有两个内含子：一个位于胰岛素原编码氨基酸38和39区域之间的490个碱基对的内含子，以及一个位于起始密码子上游17个碱基对处的119个碱基对的内含子。基因I在蛋白质编码区内没有中断，但具有一个与胰岛素II的119个碱基对内含子同源的内含子。我们正在研究其他物种胰岛素基因的结构，以确定490个碱基对的内含子是在复制基因中丢失还是插入的。我们已经鉴定出比胰岛素原mRNA更大的核RNA分子，它们包含转录的内含子序列。这些分子代表了胰岛素生物合成中的一种新前体。
