Cloning, characterization, and expression analysis of orange-spotted grouper (Epinephelus coioides) ILF2 gene (EcILF2)

Interleukin-2 enhancer binding factor 2 (ILF2), also named as nuclear factor 45 (NF45), plays important roles in regulating interleukin-2 expression in mammals. In the present study, a novel ILF2 gene (designated EcILF2) was cloned and well characterized from orange-spotted grouper, Epinephelus coioides. The full-length EcILF2 cDNA is composed of 1544 bp and encodes a polypeptide of 387 amino acids with 98% identity to ILF2 of Atlantic salmon. The genomic DNA of EcILF2 consists of 14 exons and 13 introns, with a length of approximately 6.9 kb. EcILF2 contains two conserved domains including an RGG-rich single-stranded RNA-binding domain and a DZF zinc-finger nucleic acid binding domain. Recombinant EcILF2 was expressed in Escherichia coli BL21 (DE3) and purified for mouse anti-EcILF2 serum preparation. Subcellular localization analysis revealed that EcILF2 was distributed predominantly in the nucleus. Realtime quantitative PCR (RT-qPCR) analysis revealed a broad expression of EcILF2, with a relative strong expression in skin, liver, brain, head kidney and spleen. The expression of EcILF2 was differentially up-regulated after stimulation with Vibrio vulnificus, Staphylococcus aureus, Saccharomyces cerevisiae and Singapore grouper iridovirus (SGIV). Furthermore, EcILF2 was able to activate human IL-2 promoter in different cell lines and promote the endogenous IL-2 transcription in human H9 T cells. These results suggest that EcILF2 is potentially involved in grouper immune responses to invasion of bacterial and viral pathogens.