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Molecular and Cellular Biology, December 1999, p. 8052-8065, Vol. 19, No. 12
Institute of Medical Chemistry and
Biochemistry1 and Institute of Medical
Biology and Human Genetics,2 University of
Innsbruck, A-6020 Innsbruck, Austria
Received 24 May 1999/Returned for modification 6 July 1999/Accepted 8 September 1999
Expression of constructs encoding fusion proteins of ERK1 and ERK2
containing a C-terminal farnesylation motif (CAAX) is predominantly localized at the cell membrane and was activated by coexpression of
constitutively active Ha-RasL61 and epidermal growth factor. Both
fusion proteins significantly inhibit the transcriptional activation of
a c-fos-chloramphenicol acetyltransferase reporter induced
by RasL61, constitutively active MEK1, or constitutively active RafBXB.
The corresponding SAAX chimeras or overexpression of the wild-type ERKs
did not interfere with the transcriptional activation of
c-fos. The inhibition of the Ras-mediated c-fos induction by ERK2-CAAX can in part be rescued by coexpression of a
wild-type ERK2 but not by wild-type ERK1. We find that ERK1-CAAX acts
in the same fashion, indicating that mitogen-activated protein kinase
(MAPK)-CAAX chimeras interact in an isotype-specific manner. It is
demonstrated that both ERK1-CAAX and ERK2-CAAX associate with the
corresponding endogenous ERKs, which explains the isotype-specific inhibitory effects of the ERK-CAAX chimeras. Evidence is presented that
expression of ERK-CAAX fusion proteins inhibits the nuclear translocation of the corresponding endogenous ERKs. Disruption of MAPK
translocation by membrane targeting provides additional, independent
proof that nuclear translocation of ERKs is essential for the
transcriptional activation of c-fos.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Novel Membrane-Targeted ERK1 and ERK2 Chimeras
Which Act as Dominant Negative, Isotype-Specific Mitogen-Activated
Protein Kinase Inhibitors of Ras-Raf-Mediated Transcriptional
Activation of c-fos in NIH 3T3 Cells
*
Corresponding author. Mailing address: Institute of
Medical Chemistry and Biochemistry, University of Innsbruck, Fritz
Preglstr. 3, A-6020 Innsbruck, Austria. Phone: 43-512-507-3508. Fax:
43-512-507-2872. E-mail:
Florian.Ueberall{at}uibk.ac.at.
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