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Am J Physiol Gastrointest Liver Physiol (August 30, 2007). doi:10.1152/ajpgi.00029.2007
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Submitted on January 14, 2007
Accepted on August 27, 2007

Molecular Cloning and Promoter Analysis of Down-Regulated in Adenoma DRA

Waddah A. Alrefai1*, Xiaoming Wen2, Wen Jiang2, Jonathan P. Katz3, Kris A Steinbrecher4, Mitchell B Cohen, MD5, Ifor R. Williams6, Pradeep K. Dudeja7, and Gary D. Wu2

1 University of Illinois at Chicago, Chicago, Illinois, United States; University of Illinois at Chicago
2 Gastroenterology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States
3 Department of Medicine, Gastroenterology Division, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States
4 Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children's Hospital Medical Center, cincinnatti, Ohio, United States
5 Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children's Hospital Medical Center; Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children's Hospital Medical Center, cincinnatti, Ohio, United States
6 Pathology, Emory University School of Medicine, Atlanta, Georgia, United States
7 Dept. Medicine, WSVA Med. Ctr., U. Illinois at Chicago, Chicago, Illinois, United States

* To whom correspondence should be addressed. E-mail: walrefai{at}uic.edu.

Down Regulated in Adenoma DRA, also referred to as SLC26A3, is an intestinal anion transporter essential for intestinal chloride absorption. Mutations in DRA result in congenital chloride diarrhea (CLD). DRA expression has been shown to be induced by differentiation and to be modulated by cytokines. However, mechanisms of DRA gene transcription and its tissue-specific targeting have not yet been investigated. In this study, we cloned a 3765 bp promoter fragment of human DRA gene and characterized its activity in human colonic LS174T and Caco2 human colon cell lines. Primer extension identified a single transcriptional initiation site that was identical in both colon cancer cell lines and normal colon. While hepatic nuclear factor HNF-4 is involved in the basal activity of DRA promoter, sodium butyrate induces its activity in LS174T cells via the binding of Ying Yang (YY1) and GATA transcription factors to their respective cis-elements in promoter region. We also demonstrated a reduction in DRA promoter activity in Caco2 cells by interferon-{gamma} suggesting that regulation of DRA promoter by INF-{gamma} may contribute to the pathophysiology of intestinal inflammation. Furthermore, we showed that the DRA promoter fragment is sufficient to drive human growth hormone transgene expression specifically in villus epithelial cells of the small intestine and in differentiated upper crypt and surface epithelial cells of the colon. Our studies provide evidence for the involvement of HNF-4, YY1 and GATA transcription factors in DRA expression in intestinal differentiated epithelial cells.







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