Pax6 and Pdx1 form a functional complex on the rat somatostatin gene upstream enhancer.
The somatostatin upstream enhancer (SMS-UE) is a highly complex enhancer element. The distal A-element contains overlapping Pdx1 and Pbx binding sites. However, a point mutation in the A-element that abolishes both Pdxl and Pbx binding does not impair promoter activity. In contrast, a point mutation that selectively eliminates Pdx1 binding to a proximal B-element reduces the promoter activity. The B-element completely overlaps with a Pax6 binding site, the C-element. A point mutation in the C-element demonstrates that Pax6 binding is essential for promoter activity. Interestingly, a block mutation in the A-element reduces both Pax6 binding and promoter activity. In heterologous cells, Pdx1 potentiated Pax6 mediated activation of a somatostatin reporter. We conclude that the beta/delta-cell-specific activity of the SMS-UE is achieved through simultaneous binding of Pdx1 and Pax6 to the B- and C-elements, respectively. Furthermore, the A-element appears to stabilise Pax6 binding.
Andersen
F G
FG
Department of Developmental Biology, Hagedorn Research Institute, Gentofte, Denmark.
Jensen
J
J
Heller
R S
RS
Petersen
H V
HV
Larsson
L I
LI
Madsen
O D
OD
Serup
P
P
D016475:3T3 Cells; D000818:Animals; D019677:Artificial Gene Fusion; D001483:Base Sequence; D001665:Binding Sites; D000071616:CDX2 Transcription Factor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005136:Eye Proteins; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D051381:Rats; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D013004:Somatostatin / Q000235:genetics*; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics
D000071616:CDX2 Transcription Factor; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; C000605733:Pax6 protein, rat; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein; D013004:Somatostatin