title: Role of protein kinase C in ras-mediated fos-expression.
abstract: HC-11 mouse mammary epithelial cells stably transfected with a glucocorticoid-inducible Ha-ras construct encoding a transforming (val12) p21Ha-ras were cotransfected with a c-fos-CAT construct containing the human c-fos promoter up to position -711 and the CAT reporter gene. Expression of Ha-ras by dexamethasone leads to a transcriptional activation of the fos-CAT construct which was found to be sensitive to the PKC inhibitor ilmofosine (BM41440) and abrogated by PKC depletion following long-term exposure to TPA. The responsiveness to Ha-ras is retained if only the portion of the fos promoter covering the serum response element (SRE) and the adjacent fos AP-1 (FAP) site are put in front of a CAT gene linked to a thymidine kinase (TK) promoter. Further depletion of the FAP-site does not affect the inducibility by Ha-ras. Transcriptional activation of the SRE-FAP-TK-CAT as well as the SRE-TK-CAT constructs by Ha-ras is sensitive to the PKC-inhibitor ilmofosine (BM41440) and blocked by long-term exposure to TPA. Long-term exposure to TPA depletes cells of PKC alpha and significantly reduces the PKC epsilon levels. Long-term exposure in bryostatin 1 selectively depletes PKC alpha. Depletion of PKC alpha by bryostatin 1 does not reduce the transcriptional activation of the SRE-FAP-TK-CAT-construct by Ha-ras. It is concluded that (i) transforming Ha-ras induces c-fos in HC-11 cells via PKC (presumably epsilon), (ii) the signal is mediated to the serum response element (SRE) of the fos promoter and (iii) the fos AP-1 (FAP) site is not required for this mechanism.
authors.affiliation: Institute of Medical Chemistry and Biochemistry, University of Innsbruck, Austria.
authors.forename: F
authors.initials: F
authors.lastname: Uberall
authors.forename: S
authors.initials: S
authors.lastname: Kampfer
authors.forename: C
authors.initials: C
authors.lastname: Schubert
authors.forename: W
authors.initials: W
authors.lastname: Doppler
authors.forename: H H
authors.initials: HH
authors.lastname: Grunicke
mesh_terms: D000818:Animals; D054713:Bryostatins; D002451:Cell Compartmentation; D002460:Cell Line; D004847:Epithelial Cells; D005786:Gene Expression Regulation / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism*; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides; D008321:Mammary Glands, Animal / Q000166:cytology; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D054713:Bryostatins; D007527:Isoenzymes; D007783:Lactones; D018942:Macrolides; D016760:Proto-Oncogene Proteins c-fos; D011994:Recombinant Proteins; C046785:bryostatin 1; D011493:Protein Kinase C; D018631:ras Proteins; D013755:Tetradecanoylphorbol Acetate