title: Site-specific monoubiquitination activates Ras by impeding GTPase-activating protein function.
abstract: Cell growth and differentiation are controlled by growth factor receptors coupled to the GTPase Ras. Oncogenic mutations disrupt GTPase activity, leading to persistent Ras signaling and cancer progression. Recent evidence indicates that monoubiquitination of Ras leads to Ras activation. Mutation of the primary site of monoubiquitination impairs the ability of activated K-Ras (one of the three mammalian isoforms of Ras) to promote tumor growth. To determine the mechanism of human Ras activation, we chemically ubiquitinated the protein and analyzed its function by NMR, computational modeling and biochemical activity measurements. We established that monoubiquitination has little effect on the binding of Ras to guanine nucleotide, GTP hydrolysis or exchange-factor activation but severely abrogates the response to GTPase-activating proteins in a site-specific manner. These findings reveal a new mechanism by which Ras can trigger persistent signaling in the absence of receptor activation or an oncogenic mutation.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Rachael
authors.initials: R
authors.lastname: Baker
authors.forename: Steven M
authors.initials: SM
authors.lastname: Lewis
authors.forename: Atsuo T
authors.initials: AT
authors.lastname: Sasaki
authors.forename: Emily M
authors.initials: EM
authors.lastname: Wilkerson
authors.forename: Jason W
authors.initials: JW
authors.lastname: Locasale
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Cantley
authors.forename: Brian
authors.initials: B
authors.lastname: Kuhlman
authors.forename: Henrik G
authors.initials: HG
authors.lastname: Dohlman
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Campbell
mesh_terms: D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D006147:Guanine / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015398:Signal Transduction; D054875:Ubiquitination; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020703:ras GTPase-Activating Proteins; D006147:Guanine; D018631:ras Proteins