CHARACTERIZATION OF A NUCLEAR-LOCALIZATION SEQUENCE IN THE POLYOMAVIRUS CAPSID PROTEIN VP1

Expression of VP1-β-galactosidase fusion proteins in the yeast Saccharomyces cerevisiae was used to identify a domain of the polyomavirus VP1 capsid protein which targets this protein to the nucleus. Fusion of the first 17 amino acids of VP1 to β-galactosidase was sufficient for nuclear localization, whereas fusion of the first 12 amino acids gave a mixed" cytoplasmic-nuclear phenotype. Mutation of a putative targetingsequence MAPKR (5) K from R to S changed the localization of a 21 amino acid fusion protein from the nucleus to cytoplasm. These results define a nuclear location signal in the amino terminus of polyomavirus VP1 and separate this functionfrom the high-affinity DNA binding function previously defined for this region. © 1991."