Variations in signal-mediated transport through the nuclear pores as a function of cellular activity
Previously, we utilized colloidal gold particles coated with nucleoplasmin, which contains well characterized nuclear localization signals (NLS), to study signal-mediated nuclear transport in proliferating and quiescent BALB/c 3T3 cells. The particles were injected into the cytoplasm, and nuclear uptake (N/C gold ratios) was later determined by TEM. The functional size of the transport channels was also analyzed by measuring the particles that entered the nucleoplasm. When large gold particles (110 to 270 Åin diameter) were injected, nuclear uptake was significantly greater in proliferating as compared to quiescent cells. The average fonctional pore diameter was approximately 230 Å during proliferation, and 140 Åor less in quiescent populations.