Nrf1-mediated transcriptional activation is repressed by MCRS2. A, MCRS2 mediates transcriptional repression on the transcriptional activity of LexA-Nrf1. Transient transfections were performed in 293 T cell using pGL3-control-L6 as the reporter containing six LexA-binding sites. The LexA-bZIP family fusion proteins and MCRS2 in each transfection are indicated below each track of the activities. Briefly, cells were transfected with pGL3-control-L6 reporter (0.2 μg), β-galactosidase reporter (0.1 μg), and either plasmid constructs expressing LexA (0.6 μg), LexA-Vp16 (0.6 μg), LexA-NFE2 (0.6 μg), or LexA-Nrf1 (0.6 μg) with or without MCRS2 (0.5 μg) or β-catenin (S33Y) (0.5 μg) as indicated. 36 hours after transfection, the activity of luciferase and β-galactosidase were determined as described under "Experimental procedures". In each experiment, luciferase activity from transfected cells was normalized with the β-galactosidase activity and expressed as relative luciferase activities compared with the control (LexA only, lane 1). The error bar represents the mean ± S.D. from three independent experiments. B, diagrams of the reporter and the activator structures.