Tumor suppressor QM-like gene from disk abalone (Haliotis discus discus): molecular characterization and transcriptional analysis upon immune challenge

Abstract

We describe molecular characterization and transcriptional analysis of the gene encoding tumor suppressor QM-like protein, AbQM, in the disk abalone Haliotis discus discus. The full-length cDNA (765-bp) of AbQM was found to consist of a 654-bp ORF coding for a 218 amino acid protein of a 25 kDa molecular mass with a 10.2 isoelectric point. Analysis of AbQM sequence revealed the presence of characteristic motifs, including the ribosomal protein L10 signature, SH3-binding motif and two antibiotic binding sites. Phylogenetic analysis confirmed that AbQM is closely related to other mollusk QM proteins, and altogether they form a mollusk QM protein sub-family which displays evolutionary conservation from yeast to human. Tissue-specific expression and transcriptional regulation of AbQM was analyzed by quantitative real-time PCR in response to bacterial (Vibrio alginolyticus and Vibrio parahemolyticus, Listeria monocytogenes) and viral (viral hemorrhagic septicemia virus, VHSV) challenge. AbQM transcripts were found to be expressed ubiquitously in all examined tissues in a constitutive manner, as similar expression levels were detected in hemocytes, mantle, digestive tract and muscle. Upon bacterial and VHSV challenge, AbQM showed significant up-regulation in gills, but not in hemocytes. Taken together, these findings suggest that AbQM in abalone-like mollusks can respond to and facilitate a defensive effect against pathogenic infection.