The post-translational modification of ras p21 is important for Raf-1 activation

• Published in: The Journal of biological chemistry 1994-08, Vol.269 (31), p.20054-20059
• Main Authors: KIKUCHI, A, WILLIAMS, L. T
• Format: Article
• Language: English
• Subjects: Animals; Baculoviridae - genetics; Biological and medical sciences; Cell Line; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cloning, Molecular; Enzyme Activation; Fundamental and applied biological sciences. Psychology; Glutathione Transferase - metabolism; Molecular and cellular biology; Molecular genetics; Moths; Oncogene Protein p21(ras) - genetics; Oncogene Protein p21(ras) - metabolism; Protein Processing, Post-Translational; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-raf; Recombinant Fusion Proteins - metabolism; Translation. Translation factors. Protein processing
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(17)32126-9

Raf-1, a serine/threonine kinase, is required for the mitogenic action of ras p21. It has been recently demonstrated that ras p21 directly associates with Raf-1. The C-terminal region of ras p21 is modified by farnesylation and carboxyl methylation. This modification is necessary for ras p21 function. To elucidate the role of post-translational modification of ras p21 in Raf-1 activation, we examined ras p21-dependent Raf-1 activity in baculovirus/Sf9 cells overexpressing Raf-1 and ras p21. Coexpression of Raf-1 with v-ras p21 in Sf9 cells stimulated the autophosphorylating activity of Raf-1. The activity of Raf-1, as assessed by its ability to activate extracellular signal-regulated kinase kinase (MEK) in vitro, was also increased when Raf-1 was coexpressed with v-ras p21. However, neither the autophosphorylating activity of Raf-1 nor its ability to activate MEK was stimulated by v-ras p21 mutants which are not post-translationally modified. Raf-1 formed a complex with v-ras p21 and the v-ras p21 mutants in Sf9 cells. These results indicate that the post-translational modification of ras p21 is necessary for Raf-1 activation but that the association of Raf-1 with ras p21 is not sufficient to activate Raf-1.