| Abstract: | Nuclear pores in cells of the yeast Saccharomyces cerevisiae were examined by using the freeze-fracture technique. Nuclear pore diameters in actively growing cells appear to be exclusively of the normal diameter (75 to 115 nm), whereas some pore diameters in abnormally small G1-arrested cells produced by nitrogen starvation are unusually wide (120 to 160 nm). There may be a correlation between nuclear pore size and nuclear envelope size, the larger pores tending to occur in the smaller envelopes. The finding suggests that nuclear pore diameter may not function in regulating the flow of informational molecules from nucleus to cytoplasm, but may be implicated in regulating the flow of substrates into the nucleus. |
