Molecular characterization and expression analysis of a putative LPS-induced TNF-α factor (LITAF) from pearl oyster Pinctada fucata

The lipopolysaccharide-induced TNF-α factor (LITAF) is a novel transcription factor, which plays an important role in regulating the expression of TNF-α and various inflammatory cytokines in response to LPS stimulation and forms a dependent signaling pathway separated from NF-κB. Herein, we described the identification and characterization of pearl oyster Pinctada fucata LPS-induced TNF-α factor gene (designated as poLITAF). The poLITAF cDNA was 932 bp long and consisted of a 5′-untranslated region (UTR) of 45 bp, a 3′-UTR of 497 bp with two cytokine RNA instability motifs (ATTTA), and an open reading frame (ORF) of 390 bp encoding a polypeptide of 129 amino acids with an estimated molecular mass of 13.5 kDa and a theoretical isoelectric point of 8.36. A LITAF domain at C-terminal was identified in the poLITAF using SMART analysis, which contained two conserved CXXC motifs. Homology analysis of the deduced amino acid sequence of the poLITAF with other known LITAF sequences by MatGAT software revealed that the poLITAF shared 44.2–67.4% similarity and 35.4–50.0% identity to the other known LITAF sequences. The expression level of poLITAF mRNA was the highest in digestive gland and gill, moderate in adductor muscle, gonad, intestine and mantle, the lowest in haemocytes. The poLITAF mRNA expression was significantly up-regulated at 24 h in gill and at 12 h in digestive gland after LPS stimulation respectively. These results suggested that the poLITAF was a constitutive and inducible acute-phase protein that perhaps involved in the innate immune response of pearl oyster.