In vitro analysis of Ah receptor domains involved in ligand-activated DNA recognition.

The Ah receptor (AHR) is a basic helix-loop-helix protein that mediates the effects of 2,3,7,8-tetrachloro-dibenzo-p-dioxin. In this report, we describe a rabbit reticulocyte system that allows functional expression of both the AHR and its dimeric partner, the AHR nuclear translocator protein (ARNT). By using this in vitro system, we were able to reconstitute agonist binding to the AHR and agonist-induced AHR-ARNT recognition of a cognate DNA enhancer sequence. Expression of AHR deletion mutants revealed the location of N-terminal domains responsible for ligand and DNA recognition and C-terminal domains that play roles in agonist-induced DNA recognition.