Activated GSK3 does not alter cyclin D1 levels: (A) A plasmid expressing an activated mutant of GSK3β was microinjected into the NIH3T3 cells at the right side of the area of cells photographed. 8 hrs following injection the cells were fixed and stained for GSK3, cyclin D1 and DNA. Separate fluorescence photographs of the same area of cells for of each fluorochrome are presented. (B) An injection of the GSK3 plasmid into NIH3T3 cells as above was performed and the expression of GSK3 determined by image analysis and plotted vs. the level of cyclin D1 in each cell. Injected cells are shown as small, solid circles. (C) An injection as described above was performed, but the cells were treated with MG132, and stained for phospho-Thr-286 cyclin D1 and BrdU. The average levels of phospho-cyclin D1 are plotted for each cell cycle phase for injected and neighboring uninjected cells.