A-Raf and Raf-1 work together to influence transient ERK phosphorylation and Gl/S cell cycle progression.
The Raf/MEK/ERK (extracellular regulated kinase) signal transduction pathway controls the ability of cells to respond to proliferative, apoptotic, migratory and differentiation signals. We have investigated the combined contribution of A-Raf and Raf-1 isotypes to signalling through this pathway by generating mice with knockout mutations of both A-raf and raf-1 genes. Double knockout (DKO) mice have a more severe phenotype than single null mutations of either gene, dying in embryogenesis at E10.5. The DKO embryos show no changes in apoptosis, but staining for Ki67 indicates a generalized reduction in proliferation. DKO mouse embryonic fibroblasts (MEFs) exhibit a delayed ability to enter S phase of the cell cycle. This is associated with a reduction in levels of transiently induced MEK and ERK phosphorylation and reduced expression of c-Fos and cyclin Dl. Levels of sustained ERK phosphorylation are not significantly altered. Thus, Raf-1 and A-Raf have a combined role in controlling physiological transient ERK activation and in maintenance of cell cycle progression at its usual rate.
Mercer
Kathryn
K
Department of Biochemistry, University of Leicester, Adrian Building, University Road, Leicester LEI 7RH, UK.
Giblett
Susan
S
Oakden
Anthony
A
Brown
Jane
J
Marais
Richard
R
Pritchard
Catrin
C
D000818:Animals; D017209:Apoptosis; D004622:Embryo, Mammalian / Q000166:cytology; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism* / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology; D016193:G1 Phase / Q000235:genetics / Q000502:physiology*; D018390:Gene Targeting; D051379:Mice; D018345:Mice, Knockout; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D048491:Proto-Oncogene Proteins A-raf / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology*; D016196:S Phase / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
D016760:Proto-Oncogene Proteins c-fos; D048491:Proto-Oncogene Proteins A-raf; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases