Fig. 7. Nuclear ErbB3 is a full-length molecule. (A) MDA-MB-468 cells were serum-starved, and then nuclear and cytoplasmic-membrane fractions were prepared as described in Materials and Methods. The fractions were subsequently analyzed by western blotting using anti-ErbB3 antibody. The efficiency of cell fractionation was confirmed by examination of a cytoplasmic protein, -tubulin and a nuclear protein, histone H3, using anti--tubulin and anti-histone H3 antibodies, respectively. (B) CHO cells expressing ErbB3-CFP were serum-starved, and fluorescence intensities in the nucleus and cytoplasm were measured by confocal microscopy. Relative nuclear and cytoplasmic fluorescence intensities are expressed as the mean ± s.d. (n=24).