Characterization of the human glycerol kinase promoter: identification of a functional HNF-4alpha binding site and evidence for transcriptional activation.
Glycerol kinase (GK) is an enzyme at the interface of carbohydrate and fat metabolism. Mutations in the GK gene result in a rare inborn error of metabolism, GK deficiency (GKD), and at least one of these mutations (N288D) is associated with insulin resistance and diabetes mellitus. In an attempt to identify potential modifiers of the GKD phenotype, and to elucidate better the relationship between GKD and diabetes mellitus, we investigated the GK promoter. We examined the GK promoter using in silico methods, transient transfections of GK promoter-luciferase constructs in HepG2 hepatocellular carcinoma cells, and gel shift assays using liver nuclear extracts. We determined that the first 100 bp of the GK 5(') upstream region was sufficient for basal levels of transcription and that there was a functional HNF-4alpha binding site in the first 500 bp of the 5(') upstream region that was important for increased levels of GK expression in vitro. The involvement of both GK and HNF-4alpha in the etiology of diabetes mellitus is intriguing, and we speculate that HNF-4alpha represents a potential modifier of the GKD phenotype.
Stepanian
Sevan V
SV
Department of Pediatrics, David Geffen School of Medicine at UCLA and Mattel Children's Hospital at UCLA, Los Angeles, CA, USA.
Huyn
Steven T
ST
McCabe
Edward R B
ER
Dipple
Katrina M
KM
D024506:5' Flanking Region; D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000209:etiology; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D005991:Glycerol Kinase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics; D008661:Metabolism, Inborn Errors / Q000201:enzymology / Q000235:genetics; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D010750:Phosphoproteins; D014157:Transcription Factors; D005991:Glycerol Kinase