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Mol. Cells 2008; 26(5): 462-467

Published online November 30, 2008

© The Korean Society for Molecular and Cellular Biology

Induction of the Nuclear Proto-Oncogene c-fos by the Phorbol Ester TPA and c-H-Ras

Julhash U. Kazi and Jae-Won Soh

Abstract

TPA is known to cooperate with an activated Ras oncogene in the transformation of rodent fibroblasts, but the biochemical mechanisms responsible for this effect have not been established. In the present study we used c-fos promoter-luciferase constructs as reporters, in transient transfection assays, in NIH3T3 cells to assess the mechanism of this cooperation. We found a marked synergistic interaction between TPA and a transfected v-Ha-ras oncogene in the activation of c-fos promoter and SRE. SRE has binding sites for TCF and SRF. A dominant-negative Ras (ras-N17) inhibited the TPA-Ras synergy by blocking the PKC-MAPK-TCF pathway. Dominant-negative RhoA and Rac1 (but not Cdc42Hs) inhibited the TPA-Ras synergy by blocking the Ras-Rho-SRF signaling pathway. Constitutively active PKC? and PKC? showed synergy with v-Ras. These results suggest that the activation of two distinct pathways such as Ras-Raf-ERK-TCF pathway and Rho-SRF pathway are responsible for the induction of c-fos by TPA and Ras in mitogenic signaling pathways.

Keywords Cdc42, c-fos, Rac1, Ras, RhoA, PKC, Synergy, TPA

Article

Research Article

Mol. Cells 2008; 26(5): 462-467

Published online November 30, 2008

Copyright © The Korean Society for Molecular and Cellular Biology.

Induction of the Nuclear Proto-Oncogene c-fos by the Phorbol Ester TPA and c-H-Ras

Julhash U. Kazi and Jae-Won Soh

Abstract

TPA is known to cooperate with an activated Ras oncogene in the transformation of rodent fibroblasts, but the biochemical mechanisms responsible for this effect have not been established. In the present study we used c-fos promoter-luciferase constructs as reporters, in transient transfection assays, in NIH3T3 cells to assess the mechanism of this cooperation. We found a marked synergistic interaction between TPA and a transfected v-Ha-ras oncogene in the activation of c-fos promoter and SRE. SRE has binding sites for TCF and SRF. A dominant-negative Ras (ras-N17) inhibited the TPA-Ras synergy by blocking the PKC-MAPK-TCF pathway. Dominant-negative RhoA and Rac1 (but not Cdc42Hs) inhibited the TPA-Ras synergy by blocking the Ras-Rho-SRF signaling pathway. Constitutively active PKC? and PKC? showed synergy with v-Ras. These results suggest that the activation of two distinct pathways such as Ras-Raf-ERK-TCF pathway and Rho-SRF pathway are responsible for the induction of c-fos by TPA and Ras in mitogenic signaling pathways.

Keywords: Cdc42, c-fos, Rac1, Ras, RhoA, PKC, Synergy, TPA

Mol. Cells
Dec 31, 2021 Vol.44 No.12, pp. 861~919
COVER PICTURE
Structure of the fly peripheral neurons in the fly head. Flies have basic sensory organs including eyes for vision, antennae and maxillary palps for olfaction, and proboscis (magenta) for gustation which can be labelled with monoclonal antibody 22C10. The figure is a 3D reconstructed image with 30 slices of confocal sections with 3 μm interval. It shows that the proboscis is required for sensing attractive carboxylic acids such as glycolic acid, citric acid, and lactic acid (Shrestha and Lee, pp. 900-910).

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