家蚕丝腺组织高丰度表达基因BmeIF5A的克隆和进化分析

Cloning and Phylogenetic Analysis of Eukaryotic Initiation Factor 5A,an Abundant Gene in Tissue of Silkgland in Silkworm,Bombyx mori

从家蚕丝腺组织克隆得到2种mRNA形式的家蚕Bm eIF5A基因(GenBank登陆号:DQ202521;DQ201182),虽都具有相同的编码160个氨基酸的编码区,但却为不同长短的3′非编码区(3′UTR)。家蚕Bm eIF5A基因包含3个外显子和2个内含子。组织表达谱分析发现该基因在丝腺组织里高丰度表达。分析推导的氨基酸序列揭示该基因产物具有eIF5A家族蛋白质共有的保守区。序列同源性分析表明eIF5A家族基因在所有的真核生物中都高度保守。进化生物学的分析显示家蚕的eIF5A基因与昆虫的同源性较高。

The animo acid sequence of Drosophila eIF5A was searched against the silkworm EST database with tBLASTn program. The ESTs with high score were clustered and assembled to a consensus sequence. We cloned and indentified a gene in Bombyx mori using the primers based on the consensus sequence from assembly, termed it as BmeIF5A-1 （GeneBank accession number： DQ202521 ）. We also cloned and identified the gene in silkworm using the protocol of 3＇rapid amplification of cDNA ends（3＇RACE）,termed it as BmeIF5A-2（ GeneBank accession number. DQ201182）. It had the same ORF as the BmeIF5A-1, but a poly （A） tail. These results of the structure of the BmeIF5A-1 and BmeIF5A-2 indicated that BmeIF5A gene is likely to contain two transcriptional types and different length of 3＇untranslated region. The BmeIF5A gene was abundant in silkgland tissue in the silkworm. An alignment of the coding sequence with the silkworm genome sequences revealed that there were 3 exons in BmeIF5A. The deduced amino acid sequence of the BmeIF5A shaned a conservative domain harbored in a 12 amino acid sequence（STSKTGKHGHAK）. It showed that the silkworm eIF5A protein was conserved in almost eukaryotes comparing with other species. The phylogenetic analysis showed a higher conservation of the silkworm BmeIF5A with the Arthropoda.