Molecular cloning, expression and chromosomal localization of a novel human REG family gene, REG III

Abstract

Regenerating gene ( Reg), first isolated from a regenerating islet cDNA library [J. Biol. Chem. 263 (1988) 2111], encodes a secretory protein with a growth stimulating effect on pancreatic β cells that ameliorates the diabetes of 90% depancreatized rats [Proc. Natl. Acad. Sci. USA 91 (1994) 3589] and non-obese diabetic mice [Diabetes 51(Suppl. 3) (2002) S478]. Reg and Reg-related genes have been revealed to constitute a multigene family, the Reg family, which consists of four subtypes (types I, II, III, IV) based on the primary structures of the encoded proteins of the genes [Diabetes 51(Suppl. 3) (2002) S462]. Plural type III Reg genes were found in mouse and rat. On the other hand, only one type III REG gene, HIP/PAP (gene expressed in hepatocellular carcinoma-intestine-pancreas/gene encoding pancreatitis-associated protein), was found in human. In the present study, we found a novel human type III REG gene, REG III. This gene is divided into six exons spanning about 3 kilobase pairs (kb), and encodes a 175 amino acid (aa) protein with 85% homology with HIP/PAP. REG III was expressed predominantly in pancreas and testis, but not in small intestine, whereas HIP/PAP was expressed strongly in pancreas and small intestine. IL-6 responsive elements existed in the 5′-upstream region of the human REG III gene indicating that the human REG III gene might be induced during acute pancreatitis. All the human REG family genes identified so far ( REG Iα, REG Iβ, HIP/PAP, REG III and REG IV) have a common gene structure with 6 exons and 5 introns, and encode homologous 158–175-aa secretory proteins. By database searching and PCR analysis using a yeast artificial chromosome clone, the human REG family genes on chromosome 2, except for REG IV on chromosome 1, were mapped to a contiguous 140 kb region of the human chromosome 2p12. The gene order from centromere to telomere was 5′ HIP/PAP 3′-5′ RS 3′-3′ REG Iα 5′-5′ REG Iβ 3′-3′ REG III 5′. These results suggest that the human REG gene family is constituted from an ancestor gene by gene duplication and forms a gene cluster on the region.