EFFECT OF CYCLINS AND CDKS ON THE CYCLIN B1 PROMOTER ACTIVATION

To study the effect of several cyclins on cyclin B1 promoter activatio n, we cotransfected cyclin A, cyclin E and cyclin D1 expressing plasmi ds with a cyclin B1 promoter construction driving a luciferase reporte r gene into NIH 3T3 cells. All three cyclins produced activation of th e reporter gene, however, co-transfection of cyclin A with a Cdk2 domi nant negative mutant blocks activation by cyclin A. Our results sugges t that cyclin B1 activation depends on Cdk2 kinase activity associated to cyclin A. To our knowledge this is the first report showing positi ve effect of cyclin A, cyclin E and cyclin D1 on cyclin B1 activation and blocking of this activation by a Cdk2 dominant negative mutant.