Abstract: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 1957bp, containing a 48 bp 5′-untranslated region (5′-UTR), 1302 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.
