CLONING AND CHARACTERIZATION OF THE MOUSE GLUCOKINASE GENE LOCUS AND IDENTIFICATION OF DISTAL LIVER-SPECIFIC DNASE-I HYPERSENSITIVE SITES

We cloned and characterized an 83-kb fragment of mouse genomic DNA con taining the entire glucokinase (GK) gene. The 11 exons of the gene spa n a total distance of 49 kb, with exons 1 beta and 1L being separated by 35 kb. A total of 25,266 bp of DNA sequence information was determi ned: from similar to-9.2 to similar to+15 kb (24,195 bp), relative to the hepatocyte transcription start site, and from -335 to +736 bp (107 1 bp), relative to the transcription start site in beta cells. These s equences revealed that mouse GK is >94% identical to rat and human GK. Mouse hepatic GK mRNA is regulated by fasting and refeeding, as also occurs in the rat. Alignment of the upstream and downstream promoter r egions of the mouse, rat, and human genes revealed several evolutionar ily conserved regions that may contribute to transcriptional regulatio n. However, fusion gene studies in transgenic mice indicate that the c onserved regions near the transcription start site in hepatocytes are themselves not sufficient for position-independent expression in liver . Analysis of the chromatin structure of a 48-kb region of the mouse g ene using DNase I revealed eight liver-specific hypersensitive sites w hose locations ranged from 0.1 to 36 kb upstream of the liver transcri ption start site. The availability of a single, contiguous DNA fragmen t containing the entire mouse GK gene should allow further studies of cell-specific expression of GK to be performed. (C) 1995 Academic Pres s, Inc.