Fnk is a member of the polo family of cell-cycle-regulated serine/threonine kinases. We report here that it is present in serum-starved quiescent cells and that mitogenic stimulation of quiescent cells with calf serum results in the modification of a significant fraction of the Fnk pool. This modification results in a slower migrating form when analysed by SDS/PAGE. The modification is transient and by 9 h after stimulation all of the Fnk is again present as the faster migrating form. We also show that the Fnk protein increases in abundance as cells progress from G1 to mitosis and is post-translationally modified as cells enter and exit mitosis. The Fnk modification is again manifested as a slower migrating species by SDS/PAGE and is due to phosphorylation of the protein. The mitotic-specific phosphorylation of Fnk correlates with an increase in its kinase activity, and this activity is dramatically reduced by phosphatase treatment of mitotic Fnk immunoprecipitates. During the later stages of mitosis, Fnk is dephosphorylated such that, by the time the cells enter G1, it is all present as the dephosphorylated form. These results suggest that Fnk has two functions, one during the entry of cells into the cell cycle and a second during mitosis of cycling cells.
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August 1998
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Research Article|
August 01 1998
Expression and phosphorylation of fibroblast-growth-factor-inducible kinase (Fnk) during cell-cycle progression
Dan CHASE;
Dan CHASE
*NIA, NCI-FCRF, Frederick, MD 21702, U.S.A.
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Yang FENG;
Yang FENG
*NIA, NCI-FCRF, Frederick, MD 21702, U.S.A.
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Brian HANSHEW;
Brian HANSHEW
†NCI-FCRF, Frederick, MD 21702, U.S.A.
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Jeffrey A. WINKLES;
Jeffrey A. WINKLES
‡Holland Laboratory, American Red Cross, Rockville, MD 20855, U.S.A.
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Dan L. LONGO;
Dan L. LONGO
§National Institute on Aging, Baltimore, MD 21224, U.S.A.
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Douglas K. FERRIS
Douglas K. FERRIS
1
‖SAIC, NCI-FCRF, Frederick, MD 21702, U.S.A.
1To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
December 19 1997
Revision Received:
April 15 1998
Accepted:
April 27 1998
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 333 (3): 655–660.
Article history
Received:
December 19 1997
Revision Received:
April 15 1998
Accepted:
April 27 1998
Citation
Dan CHASE, Yang FENG, Brian HANSHEW, Jeffrey A. WINKLES, Dan L. LONGO, Douglas K. FERRIS; Expression and phosphorylation of fibroblast-growth-factor-inducible kinase (Fnk) during cell-cycle progression. Biochem J 1 August 1998; 333 (3): 655–660. doi: https://doi.org/10.1042/bj3330655
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