Molecular cloning, characterization and expression analysis of QM gene from grass carp (Ctenopharyngodon idellus) homologous to Wilms' tumor suppressor

QM, a novel gene that was originally identified as a tumor suppressor, has been cloned from species encompassing members of higher vertebrate, plant and fungal kingdoms, but it is not well documented in fish. In present study, a gene homologous to QM was obtained from grass carp (Ctenopharyngodon idellus) head kidney and spleen cDNA library. The full-length grass carp QM (GcQM) cDNA of 759 bp contains a short 5′ UTR of 22 bp, a 3′ UTR of 89 bp and an open reading frame of 648 nucleotides that translates into a 215-amino acid peptide with a molecular weight of 24.5 kDa. The predicted GcQM contains a series of functional motifs that belong to the QM family signature conserved among different species. Multiple alignment analysis reveals that GcQM shares an overall identity of 62.4%∼97.7% with other members of QM family. The fish QM has a closest genetic relationship to chicken homologue Jif-1. The GcQM expresses constitutively in spleen, heart and brain, and significantly up-regulated by Aeromonas hydrophila and grass carp haemorrhagic virus (GCHV) in head kidney, spleen and liver. The results suggest that grass carp QM homolog is an inflammatory stress inducible gene associated with anti-bacterial and viral defense, and it plays an important role in immune defense.