Cell cycle progression is a tightly regulated event, the deregulation of which is a hallmark of cancer. Eukaryotic cell cycles are controlled by the temporal association of a cyclin dependent kinase (cdk) with a cyclin partner, leading to the activation of these complexes and the subsequent phosphorylation of critical substrates. The mammalian D-type cyclins and their cdk partners, cdk4 and cdk6, are important regulators of G1 phase progression; little is known about how these cdk/cyclin complexes are regulated, however. This proposal describes the molecular cloning and biochemical characterization of a novel approximate 28 kDa protein (p28) found in cdk6 immunoprecipitates containing D-type cyclins isolated from primary human T- cells in early G1 phase. Curiously, p28 immunoreacts with antibodies generated against p27KIP1, a recently identified cdk inhibitor, yet is distinct from p27KIP1. These findings raise the intriguing possibility that p28 represents a novel cdk inhibitor and that its association with cdk6/ cyclin D complexes has an important regulatory function for G1 phase control. Knowing the cDNA sequence of p28 will allow its expression and association with various cdk/ cyclin complexes as a function of the cell cycle to be analyzed. The possibility that p28 affects the kinase activity of cdk6/ cyclin D complexes or other cdk/ cyclin complexes will be investigated. The minimal domains on p28 required for p28 association with and activity towards cdk/ cyclin complexes will be mapped. Lastly, overexpression of p28 by transient transfection and functional inactivation of the protein by microinjection of anti-p28 antibodies and antisense DNA will be attempted to investigate an in vivo role for p28.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32CA069808-02
Application #
2443236
Study Section
Biological Sciences 2 (BIOL)
Project Start
1997-07-01
Project End
Budget Start
1997-07-01
Budget End
1998-06-30
Support Year
2
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02199
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Schalm, Stefanie S; Fingar, Diane C; Sabatini, David M et al. (2003) TOS motif-mediated raptor binding regulates 4E-BP1 multisite phosphorylation and function. Curr Biol 13:797-806
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Fingar, Diane C; Salama, Sofie; Tsou, Christina et al. (2002) Mammalian cell size is controlled by mTOR and its downstream targets S6K1 and 4EBP1/eIF4E. Genes Dev 16:1472-87