| Summary: | The Hippo pathway is important for tissue homeostasis, regulation of organ size and growth in most tissues. The co-transcription factor yes-associated protein 1 (YAP1) serves as a main downstream effector of the Hippo pathway and its dysregulation increases cancer development and blocks colonic tissue repair. Nevertheless, little is known about the transcriptional regulation of <i>YAP1</i> in intestinal cells. The aim of this study to identify gene control regions in the <i>YAP1</i> gene and transcription factors important for intestinal expression. Bioinformatic analysis of caudal type homeobox 2 (CDX2) and hepatocyte nuclear factor 4 alpha (HNF4α) chromatin immunoprecipitated DNA from differentiated Caco-2 cells revealed potential intragenic enhancers in the <i>YAP1</i> gene. Transfection of luciferase-expressing <i>YAP1</i> promoter-reporter constructs containing the potential enhancer regions validated one potent enhancer of the <i>YAP1</i> promoter activity in Caco-2 and T84 cells. Two potential CDX2 and one HNF4α binding sites were identified in the enhancer by in silico transcription factor binding site analysis and protein-DNA binding was confirmed in vitro using electrophoretic mobility shift assay. It was found by chromatin immunoprecipitation experiments that CDX2 and HNF4α bind to the <i>YAP1</i> enhancer in Caco-2 cells. These results reveal a previously unknown enhancer of the <i>YAP1</i> promoter activity in the <i>YAP1</i> gene, with importance for high expression levels in intestinal epithelial cells. Additionally, CDX2 and HNF4α binding are important for the <i>YAP1</i> enhancer activity in intestinal epithelial cells.
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