Expression of a novel Ca^<2+>-binding protein regucalcin and rlation to its physiologic role

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The expression of a novel calcium-binding protein regucalcin and relation to its physiologic role was investigated. The follwing results were obtained.1. Rat regucalcin gene consisted in 7 exons. The gene was determined by direct R-banding fluorescence in situ hybridization method with the 19.9 kb clone containing four exons. The regucalcin gene was localized on rat chromosome Xq11.1-12 proximal end.2. 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. Regucalcin mRNA was predominantly expressed in rat and mouse, although the expression was also seen in human, bovine and chicken.3. The expression of regucalcin mRNA in the liver was elevated by refeeding of fasted rats. This expression was involved in the action of insulin and/or calcium as stimulating factors.4. The expression of hepatic regucalcin mRNA was decreased by phenobarbital administration in rats.5. The concentraition of regucalcin in the liver was clearly increased by calcium administration in rats.6.The expression of hepatic regucalcin mRNA was enhanced in regenerating rat liver, suggesting that regucalcin plays a role in proliferation of liver cells.7.1n the transplantable Morris hepatoma cells, the regucalcin mRNA was markedly expressed, while the albumin mRNA was expressed only slightly.