The homeodomain of PAX6 is essential for PAX6-dependent activation of the rat glucagon gene promoter: evidence for a PH0-like binding that induces an active conformation.
The transcription factor PAX6 plays an important role in transcriptional regulation of the peptide hormone glucagon from pancreatic alpha-cells. PAX6 contains two DNA binding domains, the paired domain (PD) and the homeodomain (HD). While the interaction of the PD with the PAX6 responsive elements G1 and G3 in the rat glucagon gene promoter is well understood, the role of the PAX6 HD for PAX6 binding and function on G1 and G3 remains unclear. In EMSA studies the PAX6 HD was found to be mandatory for PAX6 binding to G1 but not to G3. Transient transfections with luciferase reporter gene constructs revealed the HD to be critical for proper function of PAX6 on both, G1 and G3. Transfection data with variant promoter constructs and limited proteolysis assays demonstrated that the DNA sequence located 5' to the PD binding site plays an important role for PAX6 function and its conformation on the elements G1 and G3. Taken together, our data indicate a PH0-like binding of PAX6 to the glucagon promoter elements G1 and G3 where the HD binding site is abutted directly to the PD binding motif. The data suggest that the PH0-like binding induces a transcriptionally active conformation of PAX6.
Grapp
Marcel
M
Department of Molecular Pharmacology, University of Göttingen, Göttingen, Germany.
Teichler
Sabine
S
Kitz
Julia
J
Dibaj
Payam
P
Dickel
Corinna
C
Knepel
Willhart
W
Krätzner
Ralph
R
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003627:Data Interpretation, Statistical; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D005934:Glucagon / Q000235:genetics* / Q000378:metabolism; D050416:Glucagon-Secreting Cells / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics* / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D016415:Sequence Alignment; D015533:Transcriptional Activation; D014357:Trypsin / Q000378:metabolism
D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605733:Pax6 protein, rat; D010446:Peptide Fragments; D012097:Repressor Proteins; D005934:Glucagon; D014357:Trypsin