A duodenum-specific enhancer regulates expression along three axes in the small intestine.
Adenosine deaminase (ADA) is expressed at high levels in the epithelium of proximal small intestine. Transgenic mice were used to characterize the regulatory region governing this activation. A duodenum-specific enhancer is located in intron 2 of the human ADA gene at the central site among a cluster of seven DNase I-hypersensitive sites present in duodenal DNA. Flanking DNA, including the remaining hypersensitive sites, is required for consistent high-level enhancer function. The enhancer activates expression in a pattern identical to endogenous ADA along both the anterior-posterior axis of the small intestine and the crypt-villus differentiation axis of the intestinal epithelium. Timing of activation by the central enhancer mimics endogenous mouse ADA activation, occurring at 2-3 wk of age. However, two upstream DNA segments, one proximal and one distal, collaborate to change enhancer activation to a perinatal time point. Studies with duodenal nuclear extracts identified five distinct DNase I footprints within the enhancer. Protected regions encompass six putative binding sites for the transcription factor PDX-1, as well as proposed CDX, hepatocyte nuclear factor-4, and GATA-type sites.
Dusing
M R
MR
Division of Developmental Biology, Department of Pediatrics, University of Cincinnati College of Medicine and Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA.
Brickner
A G
AG
Lowe
S Y
SY
Cohen
M B
MB
Wiginton
D A
DA
D000243:Adenosine Deaminase / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites / Q000235:genetics; D002795:Choline O-Acetyltransferase / Q000235:genetics; D002874:Chromosome Mapping; D018983:DNA Footprinting; D004268:DNA-Binding Proteins; D003850:Deoxyribonuclease I; D004386:Duodenum / Q000502:physiology*; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D051557:Hepatocyte Nuclear Factor 4; D018398:Homeodomain Proteins; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics; D019076:Transgenes
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D051557:Hepatocyte Nuclear Factor 4; D018398:Homeodomain Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; C501970:Tcfl4 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein; D002795:Choline O-Acetyltransferase; D003850:Deoxyribonuclease I; D000243:Adenosine Deaminase