Intestine-specific activity of the human guanylyl cyclase C promoter is regulated by Cdx2.
OBJECTIVE
The heat-stable enterotoxin receptor, guanylyl cyclase C, exhibits an intestine-specific pattern of expression. The aim of this study was to identify the transcriptional activator that mediates intestine-specific expression of guanylyl cyclase C.


METHODS
Fragments of the promoter were assayed to isolate regions directing intestine-specific gene activation. Deoxyribonuclease I footprinting was used to identify a site of intestine-specific protection. Electrophoretic mobility shift assays (EMSAs) and supershift analyses were used to characterize the protein that bound to the protected site. The protected site was mutated to analyze its role in promoter activity.


RESULTS
Reporter gene assays revealed that intestine-specific expression of guanylyl cyclase C is directed by the proximal promoter. Deoxyribonuclease I footprinting identified a specific site in the proximal promoter that exhibited intestine-specific protection. EMSAs and supershift analyses revealed that the transcription factor Cdx2 bound to an intestine-specific site of protection. Mutation of the Cdx2-protected site of the promoter eliminated binding of Cdx2 and reduced reporter gene activity to the level of extraintestinal cells.


CONCLUSIONS
These data show that Cdx2 and its consensus-binding site in the promoter are required for intestine-specific expression of the guanylyl cyclase C gene.
Park
J
J
Division of Clinical Pharmacology, Department of Medicine and Biochemistry, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
Schulz
S
S
Waldman
S A
SA
D000071616:CDX2 Transcription Factor; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D018983:DNA Footprinting; D003850:Deoxyribonuclease I; D017353:Gene Deletion; D015870:Gene Expression / Q000502:physiology; D006162:Guanylate Cyclase / Q000235:genetics* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000201:enzymology*; D009687:Nuclear Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology*; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators; D014158:Transcription, Genetic
D000071616:CDX2 Transcription Factor; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D018000:Receptors, Peptide; D015534:Trans-Activators; D003850:Deoxyribonuclease I; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled