O'Grady P, Krueger N X, Streuli M, Saito H
Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
J Biol Chem. 1994 Oct 7;269(40):25193-9.
The structure of the human leukocyte-common antigen-related molecule (LAR) protein tyrosine phosphatase gene was elucidated using phage and cosmid genomic DNA clones. The LAR gene is composed of 33 exons spanning over 85 kilobase pairs. Exon 2 encodes the signal sequence and the first four amino acids in the mature LAR protein. The three immunoglobulin-like domains are encoded by exons 3-7, and the eight fibronectin type III (Fn-III) domains by exons 8-17. Exons 18-22 encode the juxta-membrane and transmembrane domains, and exons 23-33 encode the two conserved tyrosine phosphatase domains and the entire 3'-untranslated region. Exon 1, which presumably encodes the 5'-untranslated sequence, has not been identified. Reverse transcription-polymerase chain reaction analysis revealed the alternative splicing of a mini-exon (exon 13) in the Fn-III domain 5 of human LAR and other related genes (rat LAR, rat PTP sigma, and human PTP delta). RNase protection analysis showed that the human LAR mRNA in which exon 13 is spliced-out is the major mRNA species in all cell lines examined. Reverse transcription-polymerase chain reaction analysis revealed further alternative splicing of LAR mRNA involving the Fn-III domains 4, 5, 6, and 7 in various combinations. These findings will facilitate the understanding of the physiological functions of the LAR extracellular domain.
利用噬菌体和黏粒基因组DNA克隆阐明了人白细胞共同抗原相关分子（LAR）蛋白酪氨酸磷酸酶基因的结构。LAR基因由33个外显子组成，跨越超过85千碱基对。外显子2编码信号序列和成熟LAR蛋白的前四个氨基酸。三个免疫球蛋白样结构域由外显子3 - 7编码，八个纤连蛋白III型（Fn - III）结构域由外显子8 - 17编码。外显子18 - 22编码近膜区和跨膜区，外显子23 - 33编码两个保守的酪氨酸磷酸酶结构域和整个3'非翻译区。推测编码5'非翻译序列的外显子1尚未被鉴定。逆转录 - 聚合酶链反应分析揭示了人LAR及其他相关基因（大鼠LAR、大鼠PTP sigma和人PTP delta）的Fn - III结构域5中的一个小外显子（外显子13）的可变剪接。核糖核酸酶保护分析表明，外显子13被剪接掉的人LAR mRNA是所有检测细胞系中的主要mRNA种类。逆转录 - 聚合酶链反应分析进一步揭示了LAR mRNA在Fn - III结构域4、5、6和7中以各种组合方式的可变剪接。这些发现将有助于理解LAR细胞外结构域的生理功能。
