2 PROLINE-RICH NUCLEAR-LOCALIZATION SIGNALS IN THE AMINO-TERMINAL ANDCARBOXYL-TERMINAL REGIONS OF THE BORNA-DISEASE VIRUS PHOSPHOPROTEIN

Borna disease virus (BDV) uses a unique strategy of replication and tr anscription which takes place in the nucleus, unlike other known, nons egmented, negative-stranded RNA viruses of animal origin. In this proc ess, viral constituents necessary for replication must be transported to the nucleus from the cytoplasm. We report here the evidence that BD V P protein, which may play an important role in viral replication and transcription, is transported into the nucleus in the absence of othe r viral constituents. This transportation is accomplished by its own n uclear localization signals (NLSs), which are present in both N-termin al (29PRPRKIPR36) and C-terminal ((181)PPRIYPQLPSAPT(193)) regions of the protein. These two NLSs can function independently and both have s everal Pro residues as key amino acids.