Polo-like kinase is a cell cycle-regulated kinase activated during mitosis.
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 p34cdc2. 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 p34cdc2-cyclin B complex can phosphorylate PLK protein in vitro but causes little increase in PLK kinase activity.
Hamanaka
R
R
Laboratory of Leukocyte Biology, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA.
Smith
M R
MR
O'Connor
P M
PM
Maloid
S
S
Mihalic
K
K
Spivak
J L
JL
Longo
D L
DL
Ferris
D K
DK
D000595:Amino Acid Sequence; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D007106:Immune Sera; D051379:Mice; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000276:immunology / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1
D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D007106:Immune Sera; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1