Transcriptional activity of domain A of the rat glucagon G3 element conferred by an islet-specific nuclear protein that also binds to similar pancreatic islet cell-specific enhancer sequences (PISCES).
A pancreatic islet cell-specific enhancer element in the rat glucagon gene, Glu-G3, contains two domains, one of which, domain A, has been shown to be necessary for Glu-G3 activity. In the present study, the functions of the isolated domain A of Glu-G3 were investigated by using transient reporter fusion gene expression and DNA binding assays. A single copy of domain A was transcriptionally inactive in glucagon-producing islet cell lines, whereas it did confer activity when combined with domain B, suggesting that Glu-G3 may be a bipartite element. Multiple copies of domain A did function independently as transcriptional enhancer in phenotypically distinct islet cell lines but not in several nonislet cell lines. Sequences (PISCES, pancreatic islet cell-specific enhancer sequences), similar to that of domain A of Glu-G3 and present in cell-specific control elements of the rat insulin I (Ins-E1) and rat somatostatin genes (SMS-UE), are shown to be required for transcriptional activity of these elements. In addition, a protein was detected in islet cell lines that bound to the PISCES motifs within Glu-G3, Ins-E1, and SMS-UE. These results support the view that cell-specific control elements of the glucagon, insulin, and somatostatin genes share a functional regulatory sequence, PISCES, and provide direct evidence for the existence of an islet-specific, PISCES-binding transcription factor or closely related proteins being involved in the coordinate expression of islet hormone genes.
Wrege
A
A
Department of Biochemical Pharmacology, University of Göttingen, Germany.
Diedrich
T
T
Hochhuth
C
C
Knepel
W
W
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D004742:Enhancer Elements, Genetic / Q000235:genetics* / Q000502:physiology; D005786:Gene Expression Regulation; D017930:Genes, Reporter / Q000502:physiology; D005934:Glucagon / Q000235:genetics* / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000502:physiology; D051381:Rats; D014162:Transfection
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D005934:Glucagon; D008156:Luciferases