RNA promotes MAPK signaling through direct interaction with BRAF

RNAs are increasingly recognized as direct regulators of protein function, yet whether RNA can control the activation of signaling kinases remains poorly understood. Here we identify RNA as a direct regulator of BRAF, a central kinase in the RAS-RAF-MEK-ERK (MAPK) pathway. Using complementary crosslinking and RNA-protein interaction approaches, we show that BRAF directly binds RNA in cells and that this interaction is enhanced upon MAPK pathway activation. Depletion of intracellular RNA reduces BRAF:CRAF complex assembly and impairs MEK1/2 phosphorylation, indicating that RNA contributes to RAF complex formation and MAPK signal transduction. We identify a positively charged surface within the BRAF kinase domain that mediates RNA binding. A separation-of-function RNA-binding mutant selectively attenuates BRAF-dependent MEK1/2 phosphorylation, demonstrating that RNA binding is required for efficient MAPK signaling. Moreover, artificial recruitment of the RNA-binding-deficient BRAF mutant to an RNA scaffold restores its signaling activity, supporting a direct role for RNA-mediated BRAF complex assembly. These data identify RNA as an active component of RAF kinase regulation and establish RNA-protein interactions as an additional determinant of MAPK pathway activation.