Cloning and characterisation of two natural killer enhancing factor genes (NKEF-A and NKEF-B) in pufferfish, Tetraodon nigroviridis

Natural killer cell enhancing factor (NKEF) belongs to a highly conserved peroxiredoxin (Prx) family. Its functions are involved in immune cytotoxicity, apoptosis, cell proliferation, differentiation and antioxidant activity. In present paper, two NKEF genes, NKEF-A and NKEF-B, were isolated and characterised in spotted green pufferfish, Tetraodon nigroviridis. Comparative genomic location analysis shows conserved syntenies within the NKEF-A and NKEF-B regions between Tetraodon and human, indicating that the Tetraodon NKEF-A and NKEF-B genes are orthologs for mammalian NKEF-A and NKEF-B encoding genes, respectively. The genomic organisation of the two genes is similar in different species, containing one non-coding exon, five coding exons and five introns. The deduced amino acids of the two genes are highly homologous with mammalian NKEF-A and NKEF-B proteins, including two well conserved Val-Cys-Pro (VCP) motifs. Tissue specific expression analysis by RT-PCR reveals that both genes are globally expressed. Stimulation with LPS inhibits both NKEF-A and NKEF-B gene expression in most tissues but enhances NKEF-A and NKEF-B transcriptions in spleen. This is the first report on the existence of a NKEF-B homologue in fish.