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Publication Abstract from PubMed

RAF family kinases are RAS-activated switches that initiate signaling through the MAP kinase cascade to control cellular proliferation, differentiation and survival(1-3). RAF activity is tightly regulated, and inappropriate activation is a frequent cause of cancer(4-6). At present, the structural basis of RAF regulation is poorly understood. Here we describe autoinhibited and active state structures of full-length BRAF in complexes with MEK1 and a 14-3-3 dimer, determined using cryo-electron microscopy (cryo-EM). A 4.1 A resolution cryo-EM reconstruction reveals an inactive BRAF-MEK1 complex restrained in a cradle formed by the 14-3-3 dimer, which binds the phosphorylated S365 and S729 sites that flank the BRAF kinase domain. The BRAF cysteine-rich domain (CRD) occupies a central position that stabilizes this assembly, but the adjacent RAS-binding domain (RBD) is poorly ordered and peripheral. The 14-3-3 cradle maintains autoinhibition by sequestering the membrane-binding CRD and blocking dimerization of the BRAF kinase domain. In the active state, these inhibitory interactions are released and a single 14-3-3 dimer rearranges to bridge the C-terminal pS729 binding sites of two BRAFs, driving formation of an active, back-to-back BRAF dimer. Our structural snapshots provide a foundation for understanding normal RAF regulation and its mutational disruption in cancer and developmental syndromes.

Architecture of autoinhibited and active BRAF-MEK1-14-3-3 complexes.,Park E, Rawson S, Li K, Kim BW, Ficarro SB, Pino GG, Sharif H, Marto JA, Jeon H, Eck MJ Nature. 2019 Oct 3. pii: 10.1038/s41586-019-1660-y. doi:, 10.1038/s41586-019-1660-y. PMID:31581174^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.