Molecular cloning and tissue expression of IRF-7 gene of Cynoglossus semilaevis

The full-length cDNA sequence of interferon regulatory factor 7(IRF-7) of tongue sole Cynoglossus semilaevis was cloned by rapid amplification cDNA end(RACE) method.The full-length cDNA of C.semilaevis IRF-7(CsIRF-7) is 1 957bp,containing a 48 bp 5'-untranslated region(5'-UTR),1 302 bp open reading frame(ORF),and a 607 bp 3'-UTR.The putative amino acid sequence of CsIRF-7 contains 433 amino acid residues.Through protein sequence alignment of IRF-7 in vertebrates,we found that the IRF-7 contains three completely conserved residues across all species,which are DNA-binding domain(DBD),IRF associated domain(IAD) and serine-rich domain(SRD).In contrast to IRF-7 of vertebrates other than fish,the DBD which is highly conserved has five tryptophan repeats,while CsIRF-7 and other fish IRF-7s have only four tryptophans with the second tryptophan residue missing.The deduced amino acid sequence of CsIRF-7 exhibited a high-level of homology with other fish,and shared the highest similarity(83.8%) and identity(73.6%) with the IRF-7 of Paralichthys olivaceus.The CsIRF-7 shared a low-level of homology with mammalia and aves.Phylogenetic analysis revealed that the C.semilaevis IRF-7 was clustered into IRF-7 subgroup with fish IRF-7 and formed the IRF-3 subfamily with IRF-3 group and other vertebrates IRF-7.Quantitative real-time method was used to detect the CsIRF-7 mRNA expression in different tissues.The results showed that CsIRF-7 was expressed in all tested tissues including liver,kidney,spleen,gill,intestine,blood cells,and heart.The high-level expression of CsIRF-7 is detected in the intestine,heart,kidney,and spleen,while a lower-level expression in the liver,gill,and blood cells.These results will be helpful for further studies on functions of antiviral and antibacterial of CsIRF-7 gene.