title: p21Waf1 inhibits the activity of cyclin dependent kinase 2 by preventing its activating phosphorylation.
abstract: Prostaglandin A2 (PGA2), a potent inhibitor of the growth of many cell types, inhibits G1 phase cyclin dependent kinases (cdk). Although PGA2 suppresses cyclin D1 and elevates p21Waf1 levels, it was the failure of cdk2 to become activated by phosphorylation which correlated best with growth inhibition. In kinetic studies, cdk2 activation was inhibited efficiently only if p21Waf1 levels increased prior to the activating phosphorylation; suggesting that p21Waf1 had blocked this phosphorylation. This model was confirmed in cells from p21Waf1 knockout mice where PGA2 was completely unable to block the activating phosphorylation of cdk2, or inhibit cdk2 activity. As expected, growth inhibition of p21Waf1(-/-) cells was not observed at PGA2 concentrations which inhibited cdk2 activity and growth of p21Waf1(+/+) cells.
authors.affiliation: The Department of Molecular Biology, The Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hitomi
authors.forename: J
authors.initials: J
authors.lastname: Shu
authors.forename: M
authors.initials: M
authors.lastname: Agarwal
authors.forename: A
authors.initials: A
authors.lastname: Agarwal
authors.forename: D W
authors.initials: DW
authors.lastname: Stacey
mesh_terms: D016475:3T3 Cells; D000818:Animals; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D016213:Cyclins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006131:Growth Inhibitors / Q000494:pharmacology / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation / Q000187:drug effects; D011454:Prostaglandins A / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000097642:GADD45 Proteins
chemical_list: D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases; D016213:Cyclins; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D011454:Prostaglandins A; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000095043:Cyclin-Dependent Kinase-Activating Kinase; D000097642:GADD45 Proteins; C493957:Cdkn1a protein, mouse; C495893:Cdk2 protein, mouse; C100008:prostaglandin A2