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Mol. Cell. Biol., Jul 1997, 3850-3857, Vol 17, No. 7
H Aktas, H Cai and GM Cooper
Activation of growth factor receptors by ligand binding initiates a cascade
of events leading to cell growth and division. Progression through the cell
cycle is controlled by cyclin-dependent protein kinases (Cdks), but the
mechanisms that link growth factor signaling to the cell cycle machinery
have not been established. We report here that Ras proteins play a key role
in integrating mitogenic signals with cell cycle progression through G1.
Ras is required for cell cycle progression and activation of both Cdk2 and
Cdk4 until approximately 2 h before the G1/S transition, corresponding to
the restriction point. Analysis of Cdk-cyclin complexes indicates that Ras
signaling is required both for induction of cyclin D1 and for
downregulation of the Cdk inhibitor p27KIP1. Constitutive expression of
cyclin D1 circumvents the requirement for Ras signaling in cell
proliferation, indicating that regulation of cyclin D1 is a critical target
of the Ras signaling cascade.
Copyright © 1997, American Society for Microbiology
Ras links growth factor signaling to the cell cycle machinery via regulation of cyclin D1 and the Cdk inhibitor p27KIP1
Dana-Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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