CELL-CYCLE INDEPENDENT INTERACTION OF CDC2 WITH THE CENTROSOME, WHICHIS ASSOCIATED WITH THE NUCLEAR MATRIX-INTERMEDIATE FILAMENT SCAFFOLD

The cell cycle regulating Cdc2 protein kinase helps orchestrate cell c ycle dependent changes in cell structure and function, This report sho ws that Cdc2 is localized to the centrosome region and is tightly boun d to the nuclear matrix-intermediate filament scaffold, Antibodies to Cdc2 and to the centrosome-specific protein, pericentrin, label the ce ntrosome in an apparently cell cycle independent manner, Isolated cent rosomes also label similarly with both antibodies. Essentially, all ce lls show Cdc2 labeling of the centrosomes, implying an independence of the stage in the cell cycle, a conclusion supported by studies of syn chronized cells, In contrast to the labeling of every cell with the Cd c2 monoclonal antibody, fewer centrosomes were labeled with an antibod y to the PSTAIRE domain of Cdc2, Embedment-free, immunogold electron m icrographs of extracted cell whole mounts show the centrioles and a pe ricentriolar network of filaments, Both Cdc2 and pericentrin antibodie s decorate the amorphous pericentriolar material, while the Cdc2 antib odies also decorate the centrioles themselves. The constitutive presen ce of Cdc2 at the centrosome suggests a continuing role in the dynamic s of centrosome function throughout the cell cycle.