Molecular cloning and expression analysis of inhibitor of growth protein 3 (ING3) in the Manila clam, Ruditapes philippinarum.

Inhibitor of growth protein 3 (ING3), a new member of ING family, is involved in the regulation of various processes. In this study, a full-length cDNA of ING3 (named as RpING3) was cloned from the gill of Ruditapes philippinarum by rapid amplification of cDNA ends method for the first time. The cDNA obtained was 1442 bp exclusive of poly (A) residues with a 1248 bp open reading frame encoding 415 amino acids. The RpING3 protein has a calculated molecular weight of 46.59 kDa and isoelectric point of 6.62. Two conserved motif and some functional sites were found. Tissue distribution analysis of the RpING3 mRNA revealed that the RpING3 expression level was much higher in gill and digestive gland while lower in mantle, foot and adductor muscle. The temporal expression of RpING3 in digestive gland after lead exposure was recorded by quantitative real-time PCR. The result showed that RpING3 was rapidly up-regulated at 6 h post-exposure and reached tenfold of the control group. These results suggest that RpING3 dependent signaling pathway is present in Manila clam and RpING3 may play important roles in protecting cells from heavy metal damage in R. philippinarum.