Inhibition of RAS function through targeting an allosteric regulatory site.

ABSTRACT

RAS GTPases are important mediators of oncogenesis in humans. However, pharmacological inhibition of RAS has proved challenging. Here we describe a functionally critical region, located outside the effector lobe of RAS, that can be targeted for inhibition. We developed NS1, a synthetic binding protein (monobody) that bound with high affinity to both GTP- and GDP-bound states of H-RAS and K-RAS but not N-RAS. NS1 potently inhibited growth factor signaling and oncogenic H-RAS- and K-RAS-mediated signaling and transformation but did not block oncogenic N-RAS, BRAF or MEK1. NS1 bound the α4-ß6-α5 region of RAS, which disrupted RAS dimerization and nanoclustering and led to blocking of CRAF-BRAF heterodimerization and activation. These results establish the importance of the α4-ß6-α5 interface in RAS-mediated signaling and define a previously unrecognized site in RAS for inhibiting RAS function.