Molecular cloning and expression analysis of interferon regulatory factor 8 (IRF8) in turbot, Scophthalmus maximus

Interferon regulatory factor 8 (IRF8) in mammals is known to be involved in antiviral response. In this study, the gene of IRF8 was cloned from the turbot (Scophthalmus maximus) fish and its expression in response to polyinosinic:polycytidylic acid (poly I:C) and turbot reddish body irrdovirus (TRBIV) challenges was studied. Turbot (Sm)IRF8 gene is 4363bp long, comprises nine exons and eight introns and encodes a putative 420 amino acid (aa) protein. The predicted protein sequence possesses a DNA binding domain (DBD), an IRF association domain (IAD) and a nuclear localization signal (NLS). Constitutive expression of SmIRF8 was detectable in all tested organs, with higher levels observed in the spleen, kidney and head kidney. SmIRF8 transcript levels were up-regulated by both poly I:C and TRBIV treatments in the spleen, head kidney, gills and muscle in an early phase of a 7-day time course and the poly I:C was a quicker inducer. In both challenge cases, the highest and earliest inductions were detected in the spleen, while the induction in the muscle was quite faint. These results provide insights into the role of SmIRF8 in antiviral response.