Cdk2 kinase is required for entry into mitosis as a positive regulator of Cdc2-cyclin B kinase activity.
In higher eukaryotes, Cdk2 kinase plays an essential role in regulating the G1-S transition. Here, we use cycling Xenopus egg extracts to examine the requirement of Cdk2 kinase on progression into mitosis. Interestingly, when Cdk2 kinase activity is inhibited by the Cdk-specific inhibitor, p21Cip1, a block to mitosis occurs, and inactive Cdc2-cyclin B accumulates. This block occurs in the absence of nuclei and is not due to direct inhibition of Cdc2 by Cip. Importantly, this block to mitosis is reversible by restoring Cdk2-cyclin E kinase activity to a Cip-treated cycling extract. Moreover, immunodepletion of Cdk2 from interphase extracts prevents activation of Cdc2 upon the addition of exogenous cyclin B. Thus, our data show that Cdk2 kinase is a positive regulator of Cdc2-cyclin B complexes and establish a link between Cdk2 kinase and cell cycle progression into mitosis.
Guadagno
T M
TM
Department of Biology, University of California, San Diego, La Jolla 92093-0347, USA.
Newport
J W
JW
D000818:Animals; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology; D002457:Cell Extracts; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000502:physiology*; D016213:Cyclins / Q000378:metabolism* / Q000494:pharmacology; D004261:DNA Replication / Q000502:physiology; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D008938:Mitosis / Q000502:physiology*; D010063:Ovum / Q000166:cytology / Q000201:enzymology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D016196:S Phase / Q000502:physiology; D014981:Xenopus; D029867:Xenopus Proteins
D002457:Cell Extracts; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D029867:Xenopus Proteins; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases