Enhanced sensitivity of an Ah-receptor system in yeast through condition modification and use of mammalian modifiers.

Proteins, such as the Ah receptor (AHR), hold potential as sensors to detect ligands in environmental and biological samples, and may also serve as tools to regulate biosynthetic and industrial processes. The AHR is also a prototype system for the PAS superfamily that can sense and mediate adaptation to signals as diverse as light, voltage, oxygen and an array of small molecules. The yeast, S. cerevisiae, has proven to be an important model to study the signal transduction of sensors like the AHR because of its ease of use, numerous available strategies for genetic manipulation, and capacity for heterologous expression. To better understand the utility of sensor proteins as components of yeast detection systems, we characterized a chimeric AHR-LexA system that drives expression from a Lex operator (LexO) driven, beta-galactosidase (β-Gal) reporter. In this report, we demonstrate that improvements in assays sensitivity and pharmacology can arise from the careful optimization of yeast growth phase and the duration of ligand exposure. We also report that the coexpression of heterotypic modifiers from mammalian cells (e.g., the ARA9 and ARA3 proteins), can improve yeast assay performance. We propose that complementing these assay improvements with previously reported yeast mutations described by others will expand the utility of the AHR for biotechnology applications.