Translation initiation of a bicistronic mRNA of Borna disease virus: a 16-kDa phosphoprotein is initiated at an internal start codon.
We examined translational initiation of a bicistronic 0.8-kb mRNA of Borna disease virus (BDV) using a cDNA clone of the mRNA. Upon transfection with the clone, COS-7 cells produced a 16-kDa protein (P'), in addition to the previously identified products of BDV, 24- (P) and 14.5-kDa proteins. The 16-kDa product was detected by anti-P monoclonal antibody and was shown to exist in BDV-infected cell lines as well as in infected animal brain cells. Transient expression analysis of mutated cDNA clones encoding the BDV 0.8-kb mRNA revealed that the 16-kDa protein was initiated at the second AUG codon on the same open reading frame of the P protein. The mutational analysis also demonstrated that the first AUG within the 0.8-kb mRNA is not optimal, although the signal contains a better Kozak's motif. These results demonstrated the presence of three functional AUG codons in the smallest mRNA of BDV and also suggested that a leaky scanning mechanism is involved in translational initiation at AUG codons downstream of the bicistronic mRNA of BDV. Furthermore, the 16-kDa protein was located in the BDV-specific nuclear foci and was found to associate with the other viral proteins in BDV-infected cells, demonstrating an important role of the novel identified BDV protein in viral replication.
Kobayashi
T
T
Department of Virology, Research Institute for Microbial Diseases, Suita, Osaka 565-0871, Japan.
Watanabe
M
M
Kamitani
W
W
Tomonaga
K
K
Ikuta
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001891:Borna disease virus / Q000235:genetics*; D001921:Brain / Q000821:virology; D019556:COS Cells; D002460:Cell Line; D018387:Codon, Initiator; D018076:DNA, Complementary / Q000235:genetics; D005455:Fluorescent Antibody Technique; D005849:Gerbillinae; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D009876:Operon; D010442:Peptide Chain Initiation, Translational / Q000235:genetics; D010750:Phosphoproteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics*; D014162:Transfection; D014764:Viral Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D014779:Virus Replication
D018387:Codon, Initiator; D018076:DNA, Complementary; D010750:Phosphoproteins; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins