EPIDERMAL GROWTH-FACTOR STIMULATION OF THE HUMAN GASTRIN PROMOTER REQUIRES SP1

Growth factors coordinately regulate a variety of different genes to s timulate cellular proliferation. In the stomach, gastrin, epidermal gr owth factor (EGF), and transforming growth factor-a all mediate gastri c mucosal homeostasis by promoting cell renewal, We have previously sh own that EGF and phorbol esters stimulate the human gastrin promoter t hrough a novel GC-rich DNA element 5'-(-68)GGGGCGGGGTGGGGGG-53 called gERE (gastrin EGF response element). In this report, we show that thre e factors bind to this element, the transcription factor Sp1 and two f ast migrating complexes designated gastrin EGF response proteins (gERP 1 and 2). To understand how these factors bind and confer EGF respons iveness, mutations of gERE were tested in vitro for protein binding an d in vivo for promoter activation. Both gel shift assays and UV cross- linking studies revealed that the factors bind to overlapping domains, Sp1 to the 5' half-site and gERP 1 and 2 to the 3' half-site. Placing either the 5' or 3' mutations upstream of a minimal gastrin promoter abolished EGF induction. Therefore both the 5' and 3' domains were req uired to confer EGF induction. Collectively, these results demonstrate that complex interactions between Spl and other factors binding to ov erlapping gERE half-sites confer EGF responsiveness to the gastrin pro moter.