赤点石斑鱼ICLP基因的克隆和序列分析

Cloning and Sequence Analysis of ICLP from Epinephelus akaara

MHC class II invariant chain-like proteins（ICLP）因子与免疫反应密切相关，其参与对抗原的处理，保证多肽不被进一步降鹪为氨基酸．通过RACE反应获得赤点石斑鱼ICLP2cDNA全序列，全长1837bp，包括44bp的5’UTR区，861bp的开放阅读框以及932bp的3’UTR区．编码286个氨基酸，推测的蛋白质分子量为31878u．对赤点石斑鱼10个组织的1CLP2基因进行PCR扩增和测序，结果表明赤点石斑鱼ICLP2基因的表达不存在组织特异性．此外，氨基酸序列同源比对的结果表明。赤点石斑鱼与其它16种脊椎动物ICLP2的相似度在25％～78％之间．与狼鲈和鳜鱼ICLP2因子的同源程度最高，分别为78％和74％．根据ICLP的氨基酸序列构建的脊椎动物系统进化树，表明了该分子的氨基酸序列可以作为研究鱼类物种间进化关系的良好指标．

The MHC（major histoeompatibility complex molecules）class II invariant chain-like proteins（ICLP）play an important role in the immune response to foreign protein antigens. It can prevent polypeptide from being degraded into amino acids. Using RACE methods, the full-length cDNA of ICLP2 gene from E. akaara was obtained. This full-length eDNA is 1 837 bp, which consists of a 44 bp 5＇UTR,a 932 bp 3＇UTR（ including poly（A））and an 861 bp open reading frame. The predicted protein has 286 amino acids with a molecular weight of 31 878 u. The result also shows that there is no tissue-specific transcript expression of ICLP2 gene in E. akaara. The similarity of the ICLP2 sequence between E. akaara and the other 16 vertibrate animals ranges from 25 % to 78% ,and reveals that E. akaara has the closest relationship with Dicentrarchus labrax and Siniperca chuatsi. The phylogenetic tree constructed in this paper demonstrates that the a mino acid sequences of ICLP gene are potentially informative for phylogenetic studies in fishes.