Pancreas duodenum homeobox-1 transcriptional activation requires interactions with p300.
The homeodomain transcription factor, pancreas duodenum homeobox (PDX)-1, is essential for pancreas development, insulin production, and glucose homeostasis. Mutations in pdx-1(ipf-1) are associated both with maturity-onset diabetes of the young and type 2 diabetes. PDX-1 interacts with multiple transcription factors and coregulators, including the coactivator p300, to activate the transcription of the insulin gene and other target genes within pancreatic beta-cells. In characterizing the protein-protein interactions of PDX-1 and p300, we identified mutations in PDX-1 that disrupt its function and are associated with increased or decreased interactions with p300. Several mutant PDX-1 proteins that are associated with heritable forms of diabetes in humans, in particular the mutant P63fsdelC, exhibited increased binding to a carboxy-terminal segment of p300 in the setting of decreased DNA-binding activities, suggesting that sequestration of p300 by mutant PDX-1 proteins may be an additional mechanism by which insulin gene expression is reduced in heterozygous carriers of pdx-1(ipf-1) mutations. The introduction of the point mutations S66A/Y68A in the highly conserved amino-terminal PDX-1 transactivation domain reduced the ability of PDX-1 to interact with p300, substantially diminished the transcriptional activation of PDX-1, and reduced the synergistic activation of glucose-responsive insulin promoter enhancer sequences by PDX-1, E12, and E47. We propose that interactions of PDX-1 with p300 are required for the transcriptional activation of PDX-1 target genes. Impairment of interactions between PDX-1 and p300 in pancreatic beta-cells may limit insulin production and lead to the development of diabetes.
Stanojevic
Violeta
V
Laboratory of Molecular Endocrinology and Diabetes Unit, Massachusetts General Hospital, Wellman 340, 50 Blossom Street, Boston, Massachusetts 02114, USA.
Habener
Joel F
JF
Thomas
Melissa K
MK
D000818:Animals; D002460:Cell Line; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics; D050881:E1A-Associated p300 Protein; D018398:Homeodomain Proteins; D006801:Humans; D009154:Mutation / Q000502:physiology; D009687:Nuclear Proteins / Q000502:physiology*; D017354:Point Mutation / Q000502:physiology; D051381:Rats; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*
D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat