(B) Quantification of the average ratio of nuclear/cytoplasmic fluorescence of COP1-3xFLAG in (A). Mean values ± S.E.M. are shown for three independent experiments where 50 individual cells per experiment were analyzed. Significance relative to GFP-COP1 with empty vector was calculated using the Student t test (*p < 0.01; **p < 0.001; ***p < 0.0001). 