Cell cycle regulation of a Xenopus Wee1-like kinase.
Using a polymerase chain reaction-based strategy, we have isolated a gene encoding a Wee1-like kinase from Xenopus eggs. The recombinant Xenopus Wee1 protein efficiently phosphorylates Cdc2 exclusively on Tyr-15 in a cyclin-dependent manner. The addition of exogenous Wee1 protein to Xenopus cell cycle extracts results in a dose-dependent delay of mitotic initiation that is accompanied by enhanced tyrosine phosphorylation of Cdc2. The activity of the Wee1 protein is highly regulated during the cell cycle: the interphase, underphosphorylated form of Wee1 (68 kDa) phosphorylates Cdc2 very efficiently, whereas the mitotic, hyperphosphorylated version (75 kDa) is weakly active as a Cdc2-specific tyrosine kinase. The down-modulation of Wee1 at mitosis is directly attributable to phosphorylation, since dephosphorylation with protein phosphatase 2A restores its kinase activity. During interphase, the activity of this Wee1 homolog does not vary in response to the presence of unreplicated DNA. The mitosis-specific phosphorylation of Wee1 is due to at least two distinct kinases: the Cdc2 protein and another activity (kinase X) that may correspond to an MPM-2 epitope kinase. These studies indicate that the down-regulation of Wee1-like kinase activity at mitosis is a multistep process that occurs after other biochemical reactions have signaled the successful completion of S phase.
Mueller
P R
PR
Division of Biology 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA.
Coleman
T R
TR
Dunphy
W G
WG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D016384:Consensus Sequence; D016213:Cyclins / Q000378:metabolism; D004261:DNA Replication; D018076:DNA, Complementary / Q000235:genetics; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D005796:Genes; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D008969:Molecular Sequence Data; D008970:Molecular Weight; D005810:Multigene Family; D009687:Nuclear Proteins; D009865:Oocytes / Q000201:enzymology; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000502:physiology*
D018797:Cell Cycle Proteins; D016213:Cyclins; D018076:DNA, Complementary; D004527:Egg Proteins; D007527:Isoenzymes; D009687:Nuclear Proteins; D029867:Xenopus Proteins; D011494:Protein Kinases; C530005:WEE1 protein, Xenopus; D011505:Protein-Tyrosine Kinases; D016203:CDC2 Protein Kinase