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Molecular and Cellular Biology, March 2001, p. 2235-2247, Vol. 21, No. 6
Ben May Institute for Cancer
Research,1 Committee on Cancer
Biology,3 and Department of
Neurobiology, Pharmacology and Physiology,2
University of Chicago, Chicago, Illinois 60637; Quality
Controlled Biochemicals, Inc., Hopkinton, Massachusetts
017484; and Department of
Immunology, The Scripps Research Institute, La Jolla, California
920375
Received 18 July 2000/Returned for modification 21 August
2000/Accepted 21 December 2000
The proto-oncogene Raf is a major regulator of growth and
differentiation. Previous studies from a number of laboratories indicate that Raf activates a signaling pathway that is independent of
the classic MEK1,2-ERK1,2 cascade. However, no other signaling cascade
downstream of Raf has been identified. We describe a new member of the
mitogen-activated protein kinase family, p97, an ERK5-related kinase
that is activated and Raf associated when cells are stimulated by Raf.
Furthermore, p97 is selectively responsive to different growth factors,
providing a mechanism for specificity in cellular signaling. Thus, p97
is activated by the neurogenic factor fibroblast growth
factor (FGF) but not the mitogenic factor epidermal growth factor (EGF)
in neuronal cells. Conversely, the related kinase ERK5 is
activated by EGF but not FGF. p97 phosphorylates transcription
factors such as Elk-1 and Ets-2 but not MEF2C at transactivating
sites, whereas ERK5 phosphorylates MEF2C but not Elk-1 or
Ets-2. Finally, p97 is expressed in a number of cell types including
primary neural and NIH 3T3 cells. Taken together, these results
identify a new signaling pathway that is distinct from the classic
Raf-MEK1,2-ERK1,2 kinase cascade and can be selectively stimulated
by growth factors that produce discrete biological outcomes.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.6.2235-2247.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
A Novel Mitogen-Activated Protein Kinase Is Responsive to Raf
and Mediates Growth Factor Specificity
*
Corresponding author. Mailing address: Ben May
Institute for Cancer Research, University of Chicago, 5841 S. Maryland
Ave., MC 6027, Chicago, IL 60637-1470. Phone: (773) 702-0380. Fax:
(773) 702-4634. E-mail:
mrosner{at}ben-may.bsd.uchicago.edu.
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