HNF3 beta and GATA-4 transactivate the liver-enriched homeobox gene, Hex

The orphan homeobox gene, Hex, has a limited domain of expression which inc ludes the developing and adult mouse liver. Hex is expressed in the develop ing liver coincident with the forkhead/winged helix transcription factor, H epatocyte Nuclear Factor 3 beta (HNF3 beta). Although preliminary character ization of the mouse Hex promoter has recently been reported, the identity of the molecular regulators that drive liver expression is not known. We hy pothesized that putative HNF3 beta and GATA-4 elements within the Hex promo ter would confer liver-enriched expression. A series of Hex promoter-driven luciferase reporter constructs were transfected in liver-derived HepG2 and fibroblast-like Cos cells +/- HNF3 beta or GATA expression plasmids. The H ex promoter region from nt -235/+22 conferred basal activity in both HepG2 and Cos cells, with the region from -103/+22 conferring liver-enriched acti vity. HNF3 beta and GATA-4 transactivated the promoter via response element s located within nt -103/+22, whereas Spl activated the -235/+22 construct. Mutation of the HNF3 element significantly reduced promoter activity in He pG2 cells, whereas this element in isolation conferred HNF3 beta responsive ness to a heterologous promoter. Electrophoretic mobility shift assays were performed to confirm transcription factor:DNA binding. We conclude that HN F3 beta and GATA-4 contribute to liver-enriched expression of Hex. (C) 2000 Elsevier Science B.V. All rights reserved.