Biochemical and Biophysical Research Communications, Vol.431, No.2, 158-163, 2013
Transcriptional regulation of PCFT by KLF4, HNF4 alpha, CDX2 and C/EBP alpha: Implication in its site-specific expression in the small intestine
Proton-coupled folate transporter (PCFT), which is responsible for the intestinal uptake of folates and analogs, is expressed only in the proximal region in the small intestine. The present study was to examine its transcriptional regulation, which may be involved in such a unique expression profile and potentially in its alteration, using dual-luciferase reporter assays in human embryonic kidney (HEK) 293 cells. The luciferase activity derived from the reporter construct containing the 5'-flanking sequence of -1695/+96 of the human PCFT gene was enhanced most extensively by the introduction of Kruppel-like factor 4 (KLF4). The KLF4-induced luciferase activity was further enhanced by hepatocyte nuclear factor 4 alpha (HNF4 alpha) synergistically. To the contrary, caudal-type homeobox transcription factor 2 (CDX2) and CCAAT/enhancer-binding protein alpha (C/EBP alpha) extensively suppressed the luciferase activity induced by KLF4 alone and also that induced by KLF4 and HNF4 alpha. Western blot analysis using the rat small intestine indicated uniform expression of KLF4 along the intestinal tract, proximal-oriented expression of HNF4 alpha, distal-oriented expression of CDX2 and C/EBP alpha. These results suggest that the activity of PCFT promoter is basically induced by KLF4 and the gradiented expression profile of PCFT may be at least in part accounted for by those of HNF4 alpha, CDX2 and C/EBP alpha. (C) 2013 Elsevier Inc. All rights reserved.