Figure 7.

Double mutant Mi, resistant to MAPK and Rsk, is transcriptionally inactive despite enhanced stability and intact DNA binding. (A) Transactivation assays were performed using wild-type Mi and single or double mutants at ser-73 and ser-409. NIH 3T3 or 501 Mel melanoma cells were cotransfected with pEBB (empty vector) or indicated Mi constructs and luciferase reporter under control of the tyrosinase promoter. Data are normalized to cotransfected sea pansy luciferase plasmid. (B) Gel shifts of BHK cells transfected with the same Mi constructs as in A after MAPK activation with TPA and cycloheximide (CHX). Mi-specific DNA-binding activity is identified using supershifting antibody.