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Regulation of Raf-1 kinase activity by the 14-3-3 family of proteins
- Source :
- Scopus-Elsevier
- Publication Year :
- 1995
-
Abstract
- We have identified the beta (beta) isoform of the 14-3-3 family of proteins as an activator of the Raf-1 protein kinase. 14-3-3 was isolated in a yeast two-hybrid screen for Raf-1 kinase domain binding proteins. Purified bovine brain 14-3-3 interacted specifically with both c-Raf-1 and the isolated Raf-1 kinase domain. Association was sensitive to the activation status of Raf-1; 14-3-3 bound to unactivated Raf-1, but not Raf-1 activated by protein kinase C alpha or Ras and Lck. The significance of these interactions under physiological conditions was demonstrated by co-immunoprecipitation of Raf-1 and 14-3-3 from extracts of quiescent, but not mitogen-stimulated, NIH 3T3 cells. 14-3-3 was not a preferred Raf-1 substrate in vitro and did not significantly affect Raf-1 kinase activity in a purified system. However, in cell-free extracts 14-3-3 acted as a Ras-independent activator of both c-Raf-1 and the Raf-1 kinase domain. The same results were obtained in vivo using transfection assays; 14-3-3 enhanced both c-Raf-1- and Raf-1 kinase domain-stimulated expression of AP-1- and NF-kappa B-dependent reporter genes and accelerated Raf-1 kinase domain-triggered differentiation of PC12 cells. We conclude that 14-3-3 is a latent co-activator bound to unactivated Raf-1 in quiescent cells and mediates mitogen-triggered but Ras-independent regulatory effects aimed directly at the kinase domain.
- Subjects :
- Tyrosine 3-Monooxygenase
Molecular Sequence Data
Mitogen-activated protein kinase kinase
Biology
Protein Serine-Threonine Kinases
General Biochemistry, Genetics and Molecular Biology
MAP2K7
Mice
Proto-Oncogene Proteins
Animals
ASK1
c-Raf
Kinase activity
Cloning, Molecular
Growth Substances
Molecular Biology
General Immunology and Microbiology
MAP kinase kinase kinase
Base Sequence
Cell-Free System
General Neuroscience
Proteins
3T3 Cells
Cell biology
Enzyme Activation
Proto-Oncogene Proteins c-raf
Biochemistry
14-3-3 Proteins
Cyclin-dependent kinase 9
Research Article
Protein Binding
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- Scopus-Elsevier
- Accession number :
- edsair.doi.dedup.....5ec662c03d09efa59c19336b83c9ec80