Fig. 5. Cell fractionation analysis. Cytoplasmic and nuclear fractions were prepared from NGF-mock and NGF-p25 cells, both treated for 6 hours with tetracycline. For each cell line, 10 µg cytoplasmic fraction (Cy) and an equivalent volume of the nuclear fraction (Nu) were analysed by western blotting. Subcellular distribution of the specified proteins was visualized using specific antibodies. The arrowhead shows cyclin-A immunoreactivity (lower bands), as determined by comparison with the SDS-PAGE pattern of immunoprecipitated cyclin A (not shown). Stripped membranes were reprobed with antibodies against NSE and lamin B to evaluate the purity of the cytoplasmic and nuclear fractions, respectively.