title: Cloning and characterization of the human and rat islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) genes.
abstract: Islet-specific glucose-6-phosphatase (G6Pase) catalytic subunit-related protein (IGRP) is a homolog of the catalytic subunit of G6Pase, the enzyme that catalyzes the terminal step of the gluconeogenic pathway. Its catalytic activity, however, has not been defined. Since IGRP gene expression is restricted to islets, this suggests a possible role in the regulation of islet metabolism and, hence, insulin secretion induced by metabolites. We report here a comparative analysis of the human, mouse, and rat IGRP genes. These studies aimed to identify conserved sequences that may be critical for IGRP function and that specify its restricted tissue distribution. The single copy human IGRP gene has five exons of similar length and coding sequence to the mouse IGRP gene and is located on human chromosome 2q28-32 adjacent to the myosin heavy chain 1B gene. In contrast, the rat IGRP gene does not appear to encode a protein as a result of a series of deletions and insertions in the coding sequence. Moreover, rat IGRP mRNA, unlike mouse and human IGRP mRNA, is not expressed in islets or islet-derived cell lines, an observation that was traced by fusion gene analysis to a mutation of the TATA box motif in the mouse/human IGRP promoters to TGTA in the rat sequence. The results provide a framework for the further analysis of the molecular basis for the tissue-restricted expression of the IGRP gene and the identification of key amino acid sequences that determine its biological activity.
authors: Department of Molecular Physiology and Biophysics, Vanderbilt University Medical School, Nashville, TN 37232, USA.
authors: C C
authors: CC
authors: Martin
authors: L J
authors: LJ
authors: Bischof
authors: B
authors: B
authors: Bergman
authors: L A
authors: LA
authors: Hornbuckle
authors: C
authors: C
authors: Hilliker
authors: C
authors: C
authors: Frigeri
authors: D
authors: D
authors: Wahl
authors: C A
authors: CA
authors: Svitek
authors: R
authors: R
authors: Wong
authors: J K
authors: JK
authors: Goldman
authors: J K
authors: JK
authors: Oeser
authors: F
authors: F
authors: Leprêtre
authors: P
authors: P
authors: Froguel
authors: R M
authors: RM
authors: O'Brien
authors: J C
authors: JC
authors: Hutton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain; D003001:Cloning, Molecular; D017124:Conserved Sequence; D005952:Glucose-6-Phosphatase / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D007124:Immunoenzyme Techniques; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment
chemical_list: D011506:Proteins; D012333:RNA, Messenger; D005952:Glucose-6-Phosphatase; C492194:G6PC2 protein, human; C117983:G6pc2 protein, mouse