NUCLEAR-PROTEIN TRANSPORT IS FUNCTIONALLY CONSERVED BETWEEN YEAST ANDHIGHER EUKARYOTES

The ability of a yeast nuclear protein to be transported into the nucl eus of a higher eukaryotic cell was investigated. Mcm1, a transcriptio nal activator protein from Saccharomyces cerevisiae, was microinjected into the cytoplasm of Xenopus laevis frog oocytes. Mcm1 was imported into the oocyte nucleus indicating that the machinery for nuclear tran sport is conserved from yeast to higher eukaryotes. Furthermore, by co mparing the nuclear import of free proteins and protein-gold complexes , we found that protein-gold complex formation appears to partially an d specifically inactivate the nuclear transport activity of Mcm1 and t hat nucleoplasmin is an exceptionally good nuclear import substrate.