FIG. 1.
A yeast screen can identify mammalian proteins that enhance steroid hormone signaling. (A) Schematic illustration of the yeast strain and strategy. The yeast strain YNK441 expresses GR constitutively and has two reporter genes, encoding His3 and β-gal, under the control of GREs. The expression of mammalian proteins that increase the response to hormone enables the activation of the pathway in the presence of low hormone concentrations, thereby allowing for growth and β-gal expression in selective media lacking histidine (−his) and containing the His3 inhibitor 3-aminotriazole (+3AT). The star-shaped forms indicate some of the possible interaction points for the mammalian modulators. (B) Mammalian p23, LEM5, and LEM6 (hPGC-1) enhance the response to corticosterone. Yeast strain YNK441 carrying a vector alone (control) or expression plasmids for the indicated cDNAs was incubated overnight with 0, 1, or 10 μM corticosterone and assayed for β-gal activity. Data represent the mean ± standard deviation of results from six independent yeast transformants. LEMGH, HepG2 library isolate; LEM6/hPGC-1, full-length cDNA.