藏羊白细胞介素-7基因的PCR扩增及生物信息学分析

为了获得藏羊白细胞介素-7（interleukin-7，IL-7）基因序列，并研究其序列特征及编码蛋白的结构和功能，本试验采用RT-PCR方法，从藏羊脾脏中扩增了IL-7基因，应用DNAStar软件分析该基因的核苷酸和氨基酸序列，与经BLAST比对后的参考序列进行同源性比对，并构建系统进化树，同时利用DNAStar软件和在线服务器预测该基因编码蛋白的二级结构、三级结构、亲水性、信号肽和蛋白翻译后修饰位点。结果表明，藏羊IL-7基因长度为531 bp（含终止密码子），编码176个氨基酸。藏羊IL-7基因与绵羊、山羊、藏羚羊、水牛、瘤牛、美洲草原野牛、黄牛和牦牛的IL-7基因核苷酸序列同源性在97.2%~99.8%之间，氨基酸序列同源性在94.9%~99.4%之间，藏羊与绵羊的亲缘关系最近。蛋白结构预测结果表明，IL-7蛋白主要由α螺旋组成，是一种亲水性和分泌型蛋白。该蛋白含有6种蛋白质翻译后修饰位点，包括1个N-豆蔻酰化位点、1个酰胺化位点、1个cAMP和cGMP依赖性蛋白激酶磷酸化位点、3个N-糖基化位点、4个蛋白激酶C磷酸化位点、6个酪蛋白激酶Ⅱ磷酸化位点。本研究结果可为藏羊IL-7基因的进一步研究与临床应用提供参考。

PCR Amplification and Bioinformatics Analysis of IL-7 Gene in Tibetan Sheep

In order to get the interleukin-7 (IL-7) gene sequence of Tibetan sheep, and research the characteristics of this sequence and structure and function of encoding protein, IL-7 gene was amplified from Tibetan sheep by RT-PCR. The nucleotide sequence,amino acid sequence, homology and phylogenetic tree were analyzed by the DNAStar software. The secondary and tertiary structures, hydrophilicity, signal peptide and post-translational modification site of the encoding protein were predicted by DNAStar software and online servers. The results showed that the length of IL-7 gene was 531 bp (contained termination codon), and encoded 176 amino acids. Compared with IL-7 gene of Ovis aries, Capra hircus, Pantholops hodgsonii, Bubalus bubalis, Bos indicus, Bison bison bison, Bos taurus and Bos mutus, IL-7 gene of Tibetan sheep showed a great similarity from 97.2% to 99.8%, the amino acid sequence homology varied from 94.9% to 99.4%, and the relationship was the closest between Tibetan sheep and Ovis aries. Result from protein structure prediction indicated that the IL-7 protein was mainly composed of α-helix, it was a hydrophilic and secretory protein. Furthermore, it had six kinds of post translational modification sites, including one N-myristoylation site, one amidation site, one cAMP-and cGMP-dependent protein kinase phosphorylation site, three N-glycosylation sites, four protein kinase C phosphorylation sites and six casein kinase Ⅱ phosphorylation sites. These results might provide references for further study and clinical application of IL-7 gene in Tibetan sheep.