IN-VITRO ANALYSIS OF AH RECEPTOR DOMAINS INVOLVED IN LIGAND-ACTIVATEDDNA RECOGNITION

The Ah receptor (AHR) is a basic helix-loop-helix protein that mediate s the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin. In this report, we describe a rabbit reticulocyte system that allows functional expres sion of both the AHR and its dimeric partner, the AHR nuclear transloc ator protein (ARNT). By using this in vitro system, we were able to re constitute agonist binding to the AHR and agonist-induced AHR-ARNT rec ognition of a cognate DNA enhancer sequence. Expression of AHR deletio n mutants revealed the location of N-terminal domains responsible for ligand and DNA recognition and C-terminal domains that play roles in a gonist-induced DNA recognition.