Constitutively active mutants of MAP kinase kinase (MEK1) induce growth factor-relaxation and oncogenicity when expressed in fibroblasts.

摘要: The Mitogen Activated Protein Kinase (MAPK) module operates downstream of Ras to convey cell surface signals the nucleus via nuclear translocation p42/p44 MAPKs. We have previously established that MAPK activation is obligatory and must persist in G1 phase allow resting fibroblasts exit from G0 (Pages et al., Proc. Natl. Acad. Sci.1993, 90, 8319-8323). It remained be whether was sufficient trigger proliferation. To this aim, we generated expressed Chinese hamster lung fibroblasts, constitutively active mutants MAP kinase (MAPKK). Three mutants: S218D, S222D S218D/S222D which substituted Raf1/MAPKKK-dependent regulatory phosphorylation sites by aspartic acid residues, displayed increased basal activity when fibroblasts. Two them, S218D a higher than serum-stimulated wild type-MAPKK (respectively 2- 5-fold), induced p42 growth factor-deprived cells. Interestingly, only these two led factor-independent state as judged early gene transcription (activation fos promoter), sensitivity factors for reinitiation DNA synthesis, autonomous cycling rapid tumor formation nude mice. Therefore conclude elements factor signalling cascade, MAPKK-MAPK, are both necessary promote