Molecular characterization, recombinant expression and bioactivity analysis of the interleukin-1β from the yellowfin sea bream, Acanthopagrus latus (Houttuyn)

Interleukin-1 beta (IL-1 beta) is an important inflammatory mediator and has also the potential as an immunoadjuvant. Here we describe the isolation and characterization of yellowfin sea bream IL-1 beta (sbIL-1 beta) cDNA and gene. The sbIL-1 beta cDNA contains a 121-bp 5' untranslated region (UTR), a single open reading frame (ORF) of 762 bp that translated into a 253 amino acid protein, a 342-bp 3' UTR with six cytokine RNA instability motifs (ATTTA), and a polyadenylation signal (AATAAA) at 13 nucleotides upstream of the poly (A) tail. The organization of the genomic IL-1 beta appears to be five exons and four introns, the intron and exon boundaries all follow the GT-AG consensus. The analysis of the expression pattern showed that sbIL-1 beta was expressed weakly in the kidney, spleen, gill and intestine, but not in the Liver, heart and muscle. After injection with 150 mu g LPS, the expression analysis in vivo showed that sbIL-1 beta was induced in the kidney and spleen and expression Level was maximal. after 4 h. The predicted 253 amino acid sequence shares 23.5-88.5% identity and 43.9-93.3% similarity to known IL-1 beta. Thus, IL-1 beta is very conserved in fish of the same family. No interleukin-converting enzyme (ICE) cut site is found in sbIL-1 beta, but the alignment of the amino acid sequence with other species showed a possible cut site between Tyr(87) and Thr(88) that would give rise to a 166-amino-acid mature peptide. The putative mature peptide was expressed in E. coli, and the recombinant sbIL-1 beta could induce the transcription of sbIL-1 beta in a dose-dependent manner and the expression levels were almost equal in the samples treated with 50 ng/ml recombinant sbIL-1 beta and 5 mu g/ml LPS, which showed recombinant sbIL-1 beta was biologically active and had the potential as an immunoadjuvant. (C) 2007 Elsevier Ltd. All rights reserved.