Sarcopterygians is an important vertebrate clade that includes crossopterygians and tetrapods.Crossopterygians are lobe-finned fish that include lungfish and coelacanths.Tetrapods include amphibians,reptiles,avians and mammals.To compare the interferon regulatory factor 1 (irf-1) gene structure and to explore phylogenetic relationships among sarcopterygians,we cloned the cDNA sequence of irf-1 from lungfish and compared it with irf-1 orthologs in other sarcopterygian species.The lungfish is a primitive sarcopterygian that occupies a very important position in vertebrate phylogeny.Interferon regulatory factors (IRFs) are a family of proteins involved in innate immunity.To date,11 IRF family members have been reported.All IRFs share homology in the first 115 amino acids,which encompasses a DNA binding domain containing a characteristic repeat of 5 tryptophan residues separated by 10-18 amino acids.IRF-1 and IRF-2 were the first members of this family to be reported and they have a very important role in innate immunity.However,studies of the irf-1 and irf-2 genes are mostly confined to mammals;very few non-mammalian irf-1 genes have been reported.Consistent with the irf-1 gene sequences already published,the first 345 nucleotides of lungfish irf-1 are highly conserved.At the carboxyl terminal a C-terminal transactivating region motif and an interferon associated domain (IAD2) were identified.417 million years separate the present from the closest common ancestor of lungfish and tetrapods;however,the irf-1 genes among sarcopterygians are highly conserved and have very obvious phylogenetic relationships.Also the interrelationship tree of sarcopterygians,based on IRF-1 amino acid sequences,is identical with trees produced using other data,such as morphological characteristics or mitochondrial gene sequences.
报道了短尾蝮蛇Gloydius brevicaudus干扰素调节因子2基因(IRF-2)的克隆和cDNA全序列测定分析。目前除在爬行类外,IRF-2基因在大部分的脊椎动物如鱼类、两栖类、鸟类和哺乳类都有报道。为了获得爬行类IRF-2基因的全序列,从短尾蝮蛇的肾、脾、肝和肠4种组织中使用Trizol试剂盒提取了总RNA。从已知的IRF-2基因序列比对设计了简并引物来扩增保守片段。最后使用RACE方法得到IRF-2的cDNA全序列。结果显示短尾蝮蛇的IRF-2基因开放阅读框包含有978个核苷酸,编码326个氨基酸,其3′UTR包含137个核苷酸。与脊椎动物其他四足动物序列比对分析还发现,短尾蝮蛇的IRF-2基因和推导的氨基酸序列都非常保守,与大部分四足动物的IRF-2相似。从其氨基酸序列中可以辨别出DBD、IDA2和transactivating dom ain等大部分元件和阻遏模体。
