Conserved sequences in a tissue-specific regulatory region of the pdx-1 gene mediate transcription in Pancreatic beta cells: role for hepatocyte nuclear factor 3 beta and Pax6.
Pancreas duodenum homeobox 1 (PDX-1) is absolutely required for pancreas development and the maintenance of islet beta-cell function. Temporal and cell-type-specific transcription of the pdx-1 gene is controlled by factors acting upon sequences found within its 5'-flanking region. Critical cis-acting transcriptional control elements are located within a nuclease hypersensitive site that contains three conserved subdomains, termed areas I, II, and III. We show that area II acts as a tissue-specific regulatory region of the pdx-1 gene, directing transgene expression to a subpopulation of islet cells. Mutation of the area II hepatocyte nuclear factor 3 (HNF3) binding element in the larger area I- and area II- containing PstBst fragment also decreases PB(hsplacZ) transgene penetrance. These two results indicate possible ontogenetic and/or functional heterogeneity of the beta-cell population. Several other potential positive- and negative-acting control elements were identified in area II after mutation of the highly conserved sequence blocks within this subdomain. Pax6, a factor essential for islet alpha-cell development and islet hormone gene expression, was shown to bind in area II in vitro. Pax6 and HNF3 beta were also found to bind to this region in vivo by using the chromatin immunoprecipitation assay. Collectively, these data suggest an important role for both HNF3 beta and Pax6 in regulating pdx-1 expression in beta cells.
Samaras
Susan E
SE
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Cissell
Michelle A
MA
Gerrish
Kevin
K
Wright
Christopher V E
CV
Gannon
Maureen
M
Stein
Roland
R
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005136:Eye Proteins; D005260:Female; D051542:Hepatocyte Nuclear Factor 3-beta; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007515:Islets of Langerhans / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D005136:Eye Proteins; C496502:FOXA2 protein, human; C496503:Foxa2 protein, mouse; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein; D051542:Hepatocyte Nuclear Factor 3-beta