MAPPING OF A FUNCTIONAL REGION CONFERRING NUCLEAR-LOCALIZATION OF PSEUDORABIES VIRUS IMMEDIATE-EARLY PROTEIN

The immediate-early protein (IE180) of pseudorabies virus (PrV) is loc alized predominantly in the nuclei of infected cells. To define the nu clear localization signals within IE180, we prepared truncated mutants of IE180 and analyzed their localization in the transfected cells by indirect immunofluorescence. Analysis of mutants truncated from the ca rboxy-terminal end of the 1460-amino acid polypeptide showed that two regions including a short sequence of basic amino acid residues were a ssociated with the nuclear localization of IE180. To assess whether th ese regions substantially function as signals for nuclear localization of the IE180 molecule, we then constructed two deletion mutants lacki ng each region. A mutant lacking amino acids 333 to 575 was detected i n the nuclei of the transfected cells, whereas the other mutant lackin g amino acids 900 to 950 was detected mainly in the cytoplasm. These r esults suggest that the region of amino acids 900 to 950 is responsibl e for nuclear localization of IE180.