摘要
为了寻找新的Down’s综合征相关基因 ,利用生物信息学分析与实验技术相结合的方法 ,从定位于Down’s综合征关键区内 (2 1q2 2 3)的EST(GenBank登录号H77399)出发 ,从人类睾丸组织cDNA文库内克隆到含同源盒结构域转录因子PKNOX1 的一种新剪接型全长cDNA ,命名为PKNOX1 B ,GenBank登陆号AY14 2 115。PKNOX1 B基因跨越 5 8 4kb ,全长cDNA约 2 8kb ,有 11个外显子和 10个内含子 ,编码 4 0 5个氨基酸残基的酸性蛋白质 ,分子量为4 4 6 2 8kDa,等电点 6 2 8。PKNOX1 B与PKNOX1 的前 9个外显子及 9个内含子完全相同 ,由于PKNOX1 B在第 10与11外显子之间发生了差异剪接 ,以致其在 3′端cDNA序列被截短约 2kb ,所编码的蛋白质在C端较PKNOX1 短 30个氨基酸残基。但PKNOX1 B保留了与PKNOX1 完全相同的同源盒结构域 ,因而它可能与其他含同源盒结构域基因家族成员一样参与了发育的遗传调控。RT PCR结果显示PKNOX1 B除骨髓组织外在人体组织广泛表达。在睾丸组织中PKNOX1 可见 5kb ,2 9kb ,2kb 3种转录本 ,而在其他组织中仅发现 2个较大的转录本 ,2kb的转录本在睾丸组织呈现特异性的表达 。
Down's syndrome (DS) is the most common chromosomal abnormality in live born infants.The cloning and characterization of genes on HC21 are necessary steps for the understanding of the molecular basis of Down's syndrome.To search for new Down's syndrome related genes,we have used bioinformatics analysis and rapid amplification of cDNA ends to identify an alternatively splicing cDNA of human PKNOX_1 in Down's syndrome critical region on the long arm of human chromosome 21.The alternatively splicing full length cDNA of human PKNOX_1,named PKNOX_1B,is 2 793 bp in length and encodes a 405 amino acid protein.Bioinformatical studies show PKNOX_1B gene spans over 58 kb on chromosome 21q22.3 and contains 11 exons and 10 introns.The predicted molecule weight of PKNOX_1B is 44.628 kDa,and the deduced iso-electric point is 6.28.Compared with PKNOX_1 gene,PKNOX_1B is 30 aa shorter at the C terminus than PKNOX_1 owing to alternative splice between (10th exon and 11th exon) last two exons.PKNOX_1B posses a same homeobox-domain as PKNOX_1,so the isoform of PKNOX_1 may be involved in the genetic control of development like other members of homeobox-containing gene family.RT-PCR results showed that PKNOX_1B is expressed in all examined tissues except in marrow tissue.By Northern blot,PKNOX_1 has three transcripts in adult testis,one about 5 kb,second about 2.9 kb,and third about 2 kb.The two larger transcript is expressed in all examined tissues,but the smallest transcript is only expressed actively in adult testis,so that it may play potential roles in spermatogenesis.
基金
国家计划生育委员会科学技术研究重大项目 (编号 :1999 0 0 2 )
湖南省自然科学基金项目 (编号 :97 B 3 2 )~~
