Serum-, TPA-, and Ras-induced expression from Ap-1/Ets-driven promoters requires Raf-1 kinase.
Raf-1 serine-threonine protein kinase has the hallmarks of a critical switch that connects growth factor receptor activation at the cell membrane with transcriptional events in the nucleus. We show by use of Raf-1 dominant-negative mutants that Raf-1 is required for serum-, TPA-, and Ras-induced expression from the oncogene-responsive element in the polyomavirus enhancer. The minimal region of Raf-1 that displays this dominant-negative phenotype (Raf-C4) contains a cysteine finger motif. Raf-C4 appears to function by titrating out a Raf-1-activating factor that is induced by Ras following serum or TPA treatment of NIH-3T3 cells. In addition, we show that Raf-1 and Ras cooperate in trans-activation through the oncogene-responsive element and that the cysteine-rich region is necessary for this effect.
Bruder
J T
JT
Laboratory of Viral Carcinogenesis, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702-1201.
Heidecker
G
G
Rapp
U R
UR
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004742:Enhancer Elements, Genetic; D015870:Gene Expression; D005814:Genes, Viral; D011905:Genes, ras; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011120:Polyomavirus / Q000235:genetics; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D012689:Sequence Homology, Nucleic Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015533:Transcriptional Activation
D011518:Proto-Oncogene Proteins; D015500:Chloramphenicol O-Acetyltransferase; D019908:Proto-Oncogene Proteins c-raf; D013755:Tetradecanoylphorbol Acetate