Polo-like Kinase Is a Cell Cycle-regulated Kinase Activated during Mitosis (*)
- Ryoji Hamanaka(1),
- Mark R. Smith(2),
- Patrick M. O'Connor(3),
- Sharon Maloid(2),
- Kelly Mihalic(1),
- Jerry L. Spivak(4),
- Dan L. Longo(1) and
- Douglas K. Ferris(2)(§)
- From the (1)Laboratory of Leukocyte Biology, Biological Response Modifiers Program, Division of Cancer Treatment and the
- (2)Biological Carcinogenesis and Development Program, Program Resources, Inc./DynCorp, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201, the
- (3)Laboratory of Molecular Pharmacology, Developmental Therapeutics Program, Division of Cancer Treatment, NCI, National Institutes of Health, Bethesda, Maryland 20892, and the
- (4)Division of Hematology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- § To whom correspondence should be addressed. Tel.: 301-846-1427; Fax: 301-846-5651.
Abstract
Previously, we demonstrated that expression of polo-like kinase (PLK) is required for cellular DNA synthesis and that overexpression
of PLK is sufficient to induce DNA synthesis. We now report that the endogenous levels of PLK, its phosphorylation status,
and protein kinase activity are tightly regulated during cell cycle progression. PLK protein is low in G1, accumulates during S and G2M, and is rapidly reduced after mitosis. During mitosis, PLK is phosphorylated on serine, and its serine threonine kinase
function is activated at a time close to that of p34
. The phosphorylated form of PLK migrates with reduced mobility on SDS-polyacrylamide gel electrophoresis, and dephosphorylation
by purified protein phosphatase 2A converts it to the more rapidly migrating form and reduces the total amount of PLK kinase
activity. Purified p34
-cyclin B complex can phosphorylate PLK protein in vitro but causes little increase in PLK kinase activity.
Footnotes
-
↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- CdK
-
cyclin-dependent protein kinases
- PLK
-
polo-like kinase
- PP2A
-
protein phosphatase 2A
- PAGE
-
polyacrylamide gel electrophoresis.
-
- Received April 5, 1995.
- Revision received June 12, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
