阴道毛滴虫RRas同源基因的克隆和序列分析

Molecular Cloning and Characterization of a RRas Homologue Gene from Trichomonas vaginalis

目的克隆和分析阴道毛滴虫RRas同源基因,以探讨其在细胞内信号传导通路中的功能。方法从已构建的阴道毛滴虫cDNA表达文库中分离得到一个与人类RRas同源的cDNA克隆,用PCR扩增该cDNA克隆TvRRas相对应的基因组DNA,并对cDNA克隆及其对应的基因组DNA进行测序。利用BLASTP,RPS-BLAST和ClustalW等工具进行序列分析。结果TvRRascDNA序列全长705对碱基,读码框含615对碱基,推测蛋白质序列具205个氨基酸。序列分析显示该基因的基因组DNA序列含有5′端ATG起始密码子和3′端的终止密码子,与cDNA序列完全一致,提示该基因无内含子;进一步分析表明该基因系RRas亚家族的同源基因,其氨基酸序列与人类和小鼠的RRas同源性最高(两者的一致性均为51%,相似性均为70%),同时拥有人类RRas基因高度保守的结合GTP的结构域和完全一致的效应结构域。进化树分析表明该基因与人类的RAS原癌蛋白基因分支及RRas分支聚类。结论获得了阴道毛滴虫RRas同源基因。

Objective To clone and characterize a RRas-like gene from Trichomonas vaginalis for studying cellular signal transduction pathways in the organism. Methods A cDNA clone, which showed homology with RRas proteins of human being, was isolated and sequenced from a cDNA expression library of T. vaginalis. The genomie DNA corresponding to the cDNA sequence was amplified using PCR technique and sequenced. Sequence analysis was performed using BLASTP, RPS-BLAST and ClustalW programs. Phylogenetic tree was constructed and bootstrapped with 1 050 replicates using the software MEGA3. Results The cDNA sequence showed a length of 705 bp with an open reading frame of 615 bp. The deduced amino acid sequence from the open reading frame possesses 205 residuals. Sequencing of the PCR product of genomic DNA revealed that the genomic DNA sequence encompassing the putative 5′-ATG and 3′- stop codons was identical to the cDNA sequence. Sequence analysis demonstrated that this gene was most homologous to the RRas members of Homo sapiens and Mus rnusculus （beth having 51% identity and 70% similarity）, and the amino acid sequence contains highly conserved GTP-binding domains and a fully conserved effector domain of human RRas member. Phylogenetic analysis showed that TvRRas clustered with RAS oncoprotein branch and RRAS branch of human. Conclusion The encoding protein probably belongs to a RRas family of T. vaginalis.