SPECIFIC SPECIES AND TISSUE DIFFERENCES FOR THE GENE-EXPRESSION OF CALCIUM-BINDING PROTEIN REGUCALCIN

The existence and expression of gene encoding the Ca2+-binding protein regucalcin in various species and tissues were investigated with Sout hern and Northern hybridization analyses using regucalcin cDNA (0.9 kb of open reading frame). Genomic Southern hybridization analysis demon strated that regucalcin gene was widely conserved among higher animals including human, monkey, rat, mouse, dog, bovine, rabbit and chicken. The gene was not found in yeast. The Northern blot analysis of poly ( A)(+)RNAs extracted from the liver of various species showed that regu calcin mRNA was predominantly expressed in rat and mouse, although the expression was also seen in human, bovine and chicken. Furthermore, t he enzyme-linked immunoadsorbent assay (ELISA) with rabbit-anti-reguca lcin IgG indicated that hepatic regucalcin concentration was most pron ounced in rat as compared with that of guinea pig, mouse and chicken. These observations show that the gene expression of regucalcin and its protein synthesis is unique in the liver of rats, suggesting the exis tence of a specific mechanism in demonstrating regucalcin synthesis fr om gene.