Interaction of activated Ras with Raf-1 alone may be sufficient for transformation of rat2 cells.
v-H-ras effector mutants have been assessed for transforming activity and for the ability of the encoded proteins to interact with Raf-1-, B-Raf-, byr2-, ralGDS-, and CDC25-encoded proteins in the yeast two-hybrid system. Transformation was assessed in rat2 cells as well as in a mutant cell line, rv68BUR, that affords a more sensitive transformation assay. Selected mutant Ras proteins were also examined for their ability to interact with an amino-terminal fragment of Raf-1 in vitro. Finally, possible cooperation between different v-H-ras effector mutants and between effector mutants and overexpressed Raf-1 was assessed. Ras transforming activity was shown to correlate best with the ability of the encoded protein to interact with Raf-1. No evidence for cooperation between v-H-ras effector mutants was found. Signaling through the Raf1-MEK-mitogen-activated protein kinase cascade may be the only effector pathway contributing to RAS transformation in these cells.
Stang
S
S
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Bottorff
D
D
Stone
J C
JC
D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000378:metabolism; D016147:Genes, Tumor Suppressor; D011905:Genes, ras / Q000235:genetics*; D066298:In Vitro Techniques; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D020726:ral Guanine Nucleotide Exchange Factor; D020668:rap GTP-Binding Proteins; D018631:ras Proteins / Q000378:metabolism*; D020666:ras-GRF1
D018797:Cell Cycle Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D020726:ral Guanine Nucleotide Exchange Factor; D020666:ras-GRF1; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D018631:ras Proteins