FIG. 1.

Nuclear import of the GFP-CK2 α fusion protein. (A) Schematic diagram of constructs. (B) Full-length GFP-CK2α was mutated on either K75A and K77A (GFP-CK2α2K) or K74A, K75A, K76A, and K77A (GFP-CK2α4K), and the constructs were transiently transfected. Cells were observed 24 h later using a confocal microscope. Bar, 10 μm. Cells were also scored for N/C ratio as described in Materials and Methods (error bars, standard deviations). (C) Dynamics of CK2α nuclear import. His₆-tagged fusion protein GFP-CK2α expressed in baculovirus-infected Sf9 cells was microinjected into the cytoplasm of NIH 3T3 cells in interphase in the absence or presence of wheat germ agglutinin (WGA). To identify the injected cells, GFP-CK2α was coinjected with dextran Texas Red. Fluorescence images were taken at the indicated time points after injection of the protein.