Isolation and characterization of a genomic region upstream from the ovine Na+/D-glucose cotransporter (SGLT1) cDNA

d-Glucose and non-metabolisable analogues of D-glucose regulate the expression of intestinal SGLT1 at both transcriptional and post-transcriptional levels. In order to investigate the molecular mechanisms involved in the transcriptional regulation of the ovine intestinal SGLT1 gene, we have isolated an upstream element of about 1 kb in size. This DNA fragment contains a TATA box motif, 48 bp upstream of the transcriptional start site and includes transcription factor binding sites for HNF-1 and AP-2. We have shown that the ovine SGLT1 promoter fragment can drive the transcription of a reporter gene when transfected into the epithelial cell lines STC-1 and LLC-PK1, which endogenously express SGLT1. Deletion analyses of the promoter indicate that −66/+21 bp proximal sequence directs the highest level of reporter gene activity. There are one and possibly two sites of transcriptional suppression.