Characterization, promoter analysis and expression of the interleukin-6 gene in blunt snout bream, Megalobrama amblycephala

Interleukin-6 (IL-6) is one of the most important multifunctional cytokines, playing essential roles in mediating the innate and adaptive immune responses. In this study, il - 6 gene and its promoter from blunt snout bream, Megalobrama amblycephala , were characterized, and its expression at the transcript level in healthy fish and after bacterial infection was determined by quantitative real-time PCR. The results showed that the M. amblycephala il - 6 ( Mamil - 6 ) cDNA had an ORF of 699 bp, encoding 232 amino acids, and contained 9 instable motifs in the 3′ UTR. The deduced MamIL-6 possessed a 24-amino acid signal peptide and was located in the cytoplasm. Although sequence alignment and phylogenetic analysis revealed that IL-6 is poorly conserved in vertebrates, the protein and genomic structure of il - 6 gene was well conserved. Analysis of the Mamil - 6 promoter revealed the presence of a conserved TATA box and six major cis -regulatory elements, including C/EBPβ (NF-IL6), AP-1, CRE, GRE, GATA and NF-κB binding sites. In healthy fish, Mamil - 6 was the most abundant in the spleen. After Aeromonas hydrophila infection, Mamil - 6 was significantly up-regulated in all 6 immune-related tissues examined, suggesting that Mamil - 6 plays an important role in the blunt snout bream immune system.