|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1996 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Borna disease virus (BDV) , a nonsegmented, negative-stranded (NNS) RNA virus, is the causative agent of a progressive encephalopathy of animals such as horses and sheep. Accumulated seroepidemiological data suggested that BDV infection may be associated with certain human psychiatric disorders, and detection of BDV RNA in peripheral blood mononuclear cells of patients with psychiatric disorders lends support to this hypothesis. Three viral proteins, i.e., the N (p40, nucleoprotein) , P (p24, phosphosprotein) and a putative L polymerase, are tightly associated with the full-length viral genomic RNA to form the ribonucleoprotein complex (RNP) which is the minimal essential infectious unit for NNS-RNA viruses. However, unlike other known animal NNS-RNA viruses, BDV genome replicates in the nucleus. For viral replication to occur in the nucleus, the viral proteins of the RNP,synthesized in the cytoplasm of the BDV-infected cells, must be imported into the nucleus.
Here, we provide evidence
that BDV N is transported to the nucleus in the absence of other viral constituents. The nuclear transport of N is mediated by the 9 NH_2-terminal amino acid residues (3-PKRRLVDDA-11) and the 4-KRR-6 sequence within it is required for the nuclear targeting activity. Similar to the N protein, the P protein is imported to the nucleus. Likely the P protein possesses two nuclear localization signals, the 19-QTLRRERSGSPRPRKIPR-36 sequence at the NH_2-terminal region and an amino acid sequence (182-PRIYPQLPSAPT-193) neighboring the COOH-terminus. In addition to these findings, we have for the first time established a eukaryotic expression system of BDV X (p10) protein, which has been recently described by others. lndirect immunofluorescence with a double staining technique and immunoprecipitation by use of anti-X antibody together with anti-N or anti-P antibody suggested that the X protein binds with N and/orP proteins and is co-localized in the nucleus where the replication of viral genome takes place. Thus, the BDV X protein, as well as N and P proteins, may have an important role for the replication of viral genome. Less