Molecular cloning and expression analysis of interferon regulatory factor 10 (IRF10) in Japanese flounder, Paralichthys olivaceus

Interferons (IFNs) are important for the defense against intracellular pathogens. Interferon regulatory factor 10 (IRF10) is a transcript factor involved in regulating IFN signaling induced by virus infections in birds, but little is know of its role in the immune response in non-avian vertebrates. Here, we identified and characterized the IRF10 gene and examined its expression pattern in a teleost fish, Japanese flounder, Paralichthys olivaceus. Japanese flounder IRF10 (PoIRF10) gene is a single copy gene, contains 8 exons and 7 introns and has 4918 nucleotides (nt) including an open reading frame (ORF) of 1212 nt encoding 404 amino acids. The deduced PoIRF10 amino acid sequence contains a DNA-binding domain (DBD), nuclear localization signal (NLS) and IRF association domain (IAD). PoIRF10 is most closely related to chicken and zebrafish IRF10 by homology search and phylogenetic analysis. Putative binding sites for activator protein-1 (AP-1), CAAT-enhancer binding protein (C/EBP), C/EBPβ, cAMP response element-binding protein (CRE-BP), IFN-stimulated response element (ISRE) and signal transducer and activator of transcription (STAT) were found in the 5′ flanking region (2.0 kb) of PoIRF10 gene. PoIRF10 mRNA was strongly expressed in gill, head kidney, heart, peripheral blood lymphocytes (PBLs), spleen and trunk kidney. PoIRF10 expression was up-regulated by Edwardsiella tarda, Streptococcus iniae and viral hemorrhagic septicemia virus (VHSV) infection in kidney. Lipopolysaccharide (LPS) and poly I:C also increased PoIRF10 expression level in PBLs. These results suggest that PoIRF10 is related to immune response in not only virus infection but also bacterial infection in teleost fish and should help to clarify the biological function of IRF10.