van den Heuvel R, Hendriks W, Quax W, Bloemendal H
J Mol Biol. 1985 Sep 20;185(2):273-84. doi: 10.1016/0022-2836(85)90403-6.
The eye lens contains a structural protein, alpha crystallin, composed of two homologous primary gene products alpha A2 and alpha B2. In certain rodents, still another alpha crystallin polypeptide, alpha AIns, occurs, which is identical to alpha A2 except that it contains an insertion peptide between residues 63 and 64. In this paper we describe the complete alpha A crystallin gene that has been cloned from DNA isolated from Syrian golden hamster. Evidence is provided that the alpha A gene is present as a single copy in the hamster genome. The detailed organization of the gene has been established by means of DNA sequence analysis and S1 nuclease mapping, revealing that the gene consists of four exons. The first exon contains the information for the 68 base-pair long 5' non-coding region as well as the coding information for the first 63 amino acids. The second exon encodes the 23 amino acid insertion sequence, the third exon codes for amino acid 87 to 127 of the alpha AIns chain, whereas the last exon encodes the C-terminal 69 amino acids and contains the information for the 523 base-pair long 3' non-coding region. The second exon is bordered by a 3' splice junction (A X G/G X C), which deviates from the consensus for donor splice sites (A X G/G X T). This deviation is found in both hamster and mouse. An internal duplication was detected in the first exon by using a DIAGON-generated matrix for comparison. By means of similar DIAGON-generated matrices it was confirmed that the amino acids coded for by the third and fourth exons are homologous to the small heat-shock proteins of Drosophila, Caenorhabditis and soyabean. The implications of the differential splicing and the evolutionary aspects of the detected homologies are discussed.
眼球晶状体含有一种结构蛋白——α晶状体蛋白，它由两种同源的初级基因产物αA2和αB2组成。在某些啮齿动物中，还存在另一种α晶状体蛋白多肽αAIns，它与αA2相同，只是在第63和64位残基之间含有一个插入肽。在本文中，我们描述了从叙利亚金黄地鼠分离的DNA中克隆出的完整αA晶状体蛋白基因。有证据表明，αA基因在仓鼠基因组中以单拷贝形式存在。通过DNA序列分析和S1核酸酶图谱分析确定了该基因的详细结构，结果显示该基因由四个外显子组成。第一个外显子包含68个碱基对长的5'非编码区信息以及前63个氨基酸的编码信息。第二个外显子编码23个氨基酸的插入序列，第三个外显子编码αAIns链的第87至127个氨基酸，而最后一个外显子编码C末端的69个氨基酸，并包含523个碱基对长的3'非编码区信息。第二个外显子的边界是一个3'剪接位点（AXG/GXC），它与供体剪接位点的共有序列（AXG/GXT）不同。这种差异在仓鼠和小鼠中都存在。通过使用DIAGON生成的矩阵进行比较，在第一个外显子中检测到一个内部重复。通过类似的DIAGON生成的矩阵证实，第三和第四个外显子编码的氨基酸与果蝇、秀丽隐杆线虫和大豆的小热休克蛋白同源。文中讨论了差异剪接的意义以及所检测到的同源性的进化方面。
