An interleukin-2 enhancer binding factor 2 homolog involved in immune response from Chinese mitten crab Eriocheir sinensis

As a transcription factor, Interleukin-2 enhancer binding factor 2 (ILF2) regulates IL-2 gene at level of transcription, splicing and translation in vertebrates and plays significant roles in immune system. In this study, an ILF2 homolog was identified from Chinese mitten crab Eriocheir sinensis (designated as EsILF) by expressed sequence tag (EST) analysis. The full-length cDNA of EsILF was of 2159 bp, containing a 5′ untranslated region (UTR) of 90 bp, a 3′ UTR of 866 bp with a poly (A) tail, and an open reading frame (ORF) of 1203 bp encoding a polypeptide of 400 amino acids with the predicted molecular weight of 44.3 kDa, which shared 59.6–64.5% identities with vertebrate ILF2. There were a conserved N-terminal RGG-rich single-stranded RNA-binding domain and a DZF zinc-finger nucleic acid binding domain in the primary structure, strongly suggesting that EsILF was a homolog of vertebrate ILF2. The mRNA of EsILF was constitutively expressed in all tested tissues of untreated crabs, including hepatopancreas, gill, gonad, muscle, heart and hemocytes, with highest expression in muscle and relative lower levels in hemocytes and gonad. The mRNA expression of EsILF in hemocytes was regulated differently after the crabs were stimulated by bacteria Listonella anguillarum and fungi Pichia pastoris GS115. The expression level was significantly (P < 0.05) down-regulated to 0.35- and 0.29-fold compared with blank group at 6 h and 12 h after the stimulation of L. anguillarum, while P. pastoris significantly (P < 0.05) up-regulated the expression level to 3.2-fold compared with the blank group at 6 h post treatment. The results indicated that EsILF was involved in the immune response of crab toward both L. anguillarum and P. pastoris.