Figure 2. KSR1-activated BRAF phosphorylates KSR1-free MEK1.
a, Putative roles of KSR in RAF-mediated MEK phosphorylation. Model 1 was adapted from reference #7. AS stands for activation segment. b, Y2H binding analysis of WT MEK1 and activation segment mutants MEK1M219V (MV), MEK1N221Y (NY), and MEK1M219W/A220L (MW-AL) to KSR1W831R or BRAFI666R. c, MEK1M219W/A220L (MW-AL), but not WT MEK1, induces KSR1W831R-BRAF dimerization and transactivation as determined by co-IP and pMEK levels. d, MEK1M219W/A220L bound to KSR1W831R induces BRAF activity towards MEK1 free of KSR1. Experiments in b-d were repeated at least 3 times. For gel source data, see Supplementary Fig. 1.