Identification and characterization of lipopolysaccharide-induced TNF-alpha factor gene from Japanese flounder Paralichthys olivaceus.

Lipopolysaccharide-induced TNF-α factor (LITAF) is an important transcription factor participating in innate immunity through regulating TNF-α and other inflammatory cytokines expression. However, the expression and biological relevance of LITAF in fish is still very limited. In this study, a full-length LITAF cDNA, termed PoLITAF, was identified from Japanese flounder Paralichthys olivaceus. PoLITAF contains a 67 bp 5'-untranslated sequence, a 435 bp open reading frame, and a 647 bp 3'-untranslated sequence. PoLITAF protein is comprised of 144 amino acids with a conserved C-terminal LITAF-like domain and shows 51-76% sequence similarity and 40-65% sequence identity with other LITAF homologues. Characterization of this new gene revealed that PoLITAF mRNA was detected in all examined tissues with the highest expression in gill. In head kidney primary culture, the expression of Japanese flounder PoLITAF and TNF-α was significantly up-regulated in response to Poly(I:C) and bacterial endotoxin LPS stimulation. Further in vivo experiments demonstrated that PoLITAF expression was up-regulated in head kidney, gill and spleen post bacterial challenge with Edwardsiella tarda. Moreover, the up-regulated expression of Japanese flounder TNF-α following the enhanced expression of PoLITAF was detected as early as 4h in both gill and head kidney tissues and 12h in spleen after the bacterial infection in vivo. Our findings suggest that PoLITAF is a novel inducible gene possibly involved in Japanese flounder innate immunity.