Nuclear protein transport is functionally conserved between yeast and higher eukaryotes.

The ability of a yeast nuclear protein to be transported into the nucleus of a higher eukaryotic cell was investigated. Mcm1, a transcriptional 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 transport is conserved from yeast to higher eukaryotes. Furthermore, by comparing the nuclear import of free proteins and protein-gold complexes, we found that protein-gold complex formation appears to partially and specifically inactivate the nuclear transport activity of Mcm1 and that nucleoplasmin is an exceptionally good nuclear import substrate.