Single plasmids expressing human steroid hormone receptors and a reporter gene for use in yeast signaling assays.

Single plasmids designed to express the six human type I steroid hormone receptors and detect signaling activity are described in this report. These stably replicating plasmids reported ligand-induced transcriptional activation via lacZ assays in Baker's yeast (Saccharomyces cerevisiae). The ligand concentrations needed to activate signaling in yeast expressing these plasmids spanned five orders of magnitude as based on comparisons of EC(50) values. Radicicol, a direct inhibitor of heat shock protein 90 (Hsp90) and an indirect inhibitor of steroid hormone receptor signaling, was used to determine the functional utility of this yeast reporter system. The inhibitory effect of radicicol was similar on the signaling of all six steroid hormone receptors and was distinguishable from cytotoxic effects that occurred with higher concentrations. These yeast plasmids provide a high throughput system for comparative assessment of steroid hormone receptor signaling and may be useful in screening for pharmacological or xenobiotic activities.