Cloning and characterization of the human trefoil factor 3 gene promoter.

Human trefoil factor 3 (hTFF3) is a small-molecule peptide with potential medicinal value. Its main pharmacological function is to alleviate gastrointestinal mucosal injuries caused by various factors and promote the repair of damaged mucosa. However, how its transcription is regulated is not yet known. The aim of this study was to clone the hTFF3 gene promoter region, identify the core promoter and any transcription factors that bind to the promoter, and begin to clarify the regulation of its expression. The 5' flanking sequence of the hTFF3 gene was cloned from human whole blood genomic DNA by PCR. Truncated promoter fragments with different were cloned and inserted into the pGL3-Basic vector to determine the position of the core hTFF3 promoter. Transcription element maintaining basic transcriptional activity was assessed by mutation techniques. Protein-DNA interactions were analyzed by chromatin immunoprecipitation (ChIP). RNA interference and gene over-expression were performed to assay the effect of transcription factor on the hTFF3 expression. The results showed that approximately 1,826 bp of the fragment upstream of hTFF3 was successfully amplified, and its core promoter region was determined to be from -300 bp to -280 bp through analysis of truncated mutants. Mutation analysis confirmed that the sequence required to maintain basic transcriptional activity was accurately positioned from -300 bp to -296 bp. Bioinformatic analysis indicated that this area contained a Sp1 binding site. Sp1 binding to the hTFF3 promoter was confirmed by ChIP experiments. Sp1 over-expression and interference experiments showed that Sp1 enhanced the transcriptional activity of the hTFF3 promoter and increased hTFF3 expression. This study demonstrated that Sp1 plays an important role in maintaining the transcription of hTFF3.