Characterization of a Rel\NF-κB homologue in a gastropod abalone, Haliotis diversicolor supertexta

Rel\NF-κB signal transduction pathway is evolutionarily conserved and involved in numerous biological processes. We report here, for the first time that a homologue of Rel\NF-κB transcription factor, Ab-Rel, was identified and functionally characterized in a gastropod abalone, H. diversicolor supertexta. The full-length Ab-Rel cDNA consists of 1943bp with an ORF encoding a 584 amino acids protein. Amino acid sequence analysis revealed that Ab-Rel shares conserved signature motifs with other Rel proteins, including the Rel homology domain (RHD), nuclear localization signal (NLS) and phosphorylation site, RRPS. Northern hybridization and real-time PCR indicated that Ab-Rel was ubiquitously and constitutively expressed in abalone. The recombinant Ab-Rel RHD protein was confirmed to specifically bind the consensus NF-κB binding site. Furthermore, EMSA showed that NF-κB activity was induced in abalone hemocytes by stimulation with LPS. These results strongly suggest that Ab-Rel is a Rel homologue, which plays a conserved role in the immune response of the ancient invertebrate, abalone, allowing us to study the Rel\NF-κB signaling pathway in an evolutionary context.