title: Expression of the human glucokinase gene: important roles of the 5' flanking and intron 1 sequences.
abstract: BACKGROUND
  Glucokinase plays important tissue-specific roles in human physiology, where it acts as a sensor of blood glucose levels in the pancreas, and a few other cells of the gut and brain, and as the rate-limiting step in glucose metabolism in the liver. Liver-specific expression is driven by one of the two tissue-specific promoters, and has an absolute requirement for insulin. The sequences that mediate regulation by insulin are incompletely understood.
  
  
  RESULTS
  To better understand the liver-specific expression of the human glucokinase gene we compared the structures of this gene from diverse mammals. Much of the sequence located between the 5' pancreatic beta-cell-specific and downstream liver-specific promoters of the glucokinase genes is composed of repetitive DNA elements that were inserted in parallel on different mammalian lineages. The transcriptional activity of the liver-specific promoter 5' flanking sequences were tested with and without downstream intronic sequences in two human liver cells lines, HepG2 and L-02. While glucokinase liver-specific 5' flanking sequences support expression in liver cell lines, a sequence located about 2000 bases 3' to the liver-specific mRNA start site represses gene expression. Enhanced reporter gene expression was observed in both cell lines when cells were treated with fetal calf serum, but only in the L-02 cells was expression enhanced by insulin.
  
  
  CONCLUSIONS
  Our results suggest that the normal liver L-02 cell line may be a better model to understand the regulation of the liver-specific expression of the human glucokinase gene. Our results also suggest that sequences downstream of the liver-specific mRNA start site have important roles in the regulation of liver-specific glucokinase gene expression.
authors.affiliation: Department of Pharmacology, Peking University, Health Science Center, Beijing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Tingting
authors.initials: T
authors.lastname: Guo
authors.forename: Shuyong
authors.initials: S
authors.lastname: Zhao
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Li
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Mao
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Rongjing
authors.initials: R
authors.lastname: Song
authors.forename: Ling
authors.initials: L
authors.lastname: Jin
authors.forename: Xiuli
authors.initials: X
authors.lastname: Li
authors.forename: David M
authors.initials: DM
authors.lastname: Irwin
authors.forename: Gang
authors.initials: G
authors.lastname: Niu
authors.forename: Huanran
authors.initials: H
authors.lastname: Tan
mesh_terms: D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002460:Cell Line; D017124:Conserved Sequence; D015870:Gene Expression; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D005941:Glucokinase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000502:physiology; D007438:Introns; D008099:Liver / Q000166:cytology / Q000201:enzymology; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D044967:Serum / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D007328:Insulin; D049410:Luciferases, Renilla; D005941:Glucokinase