Identification and characterization of a nuclear localization sequence-binding protein in yeast.

Nuclear proteins contain specific regions that are required for entry into the nucleus. Using ligand blotting, we have shown that a 67-kDa yeast nuclear envelope protein (p67) recognizes synthetic peptides containing the yeast histone H2B or simian virus 40 large tumor antigen nuclear localization sequence. Both free peptide and peptide conjugated to human serum albumin are recognized. The interaction between p67 and the nuclear localization sequences is specific; neither a mutant peptide that is incompetent for nuclear transport in vivo nor HSA can interact with p67 on blots. Moreover, although the wild-type peptide competes for binding to p67, the mutant peptides do not. p67 appears to be located at the nuclear envelope and is not present in other subcellular fractions. The nuclear localization sequence-binding protein is not extracted from the nuclear envelope with nonionic detergents and only partially extracted with high-salt buffer or 8 M urea, suggestive of a tight association with the nuclear envelope. Together our results are consistent with a role for p67 in nuclear transport.