Bovine papillomavirus with a mutation in the E2 serine 301 phosphorylation site replicates at a high copy number.
The E2 open reading frame of bovine papillomavirus type 1 (BPV-1) encodes at least three proteins with transcriptional regulatory properties. The full-length E2 open reading frame encodes a transcriptional transactivator, and the 3' region encodes two smaller polypeptides that repress E2-mediated transactivation. The full-length gene product is also required for viral DNA replication. We have demonstrated that the BPV-1 E2 polypeptides are phosphorylated primarily on two serine residues at a site adjacent to the carboxy-terminal DNA binding domain, which is common to all three E2 proteins (A. A. McBride, J. B. Bolen, and P. M. Howley, J. Virol. 63:5076-5085, 1989). These serine residues, at amino acid positions 298 and 301, were substituted with alanine residues in the context of the entire BPV-1 genome. The mutated BPV-1 genomes were introduced into rodent cell lines and assayed for focus formation, viral gene expression, and extrachromosomal viral DNA replication. Viral DNAs containing the E2 serine-to-alanine substitution mutants transformed C127 cells with efficiencies comparable to that of wild-type BPV-1. However, the viral genome containing the serine-to-alanine substitution at position 301 of the E2 polypeptide replicated to a copy number 20-fold higher than that of wild-type DNA.
McBride
A A
AA
Laboratory of Tumor Virus Biology, National Cancer Institute, Bethesda, Maryland 20892.
Howley
P M
PM
D000595:Amino Acid Sequence; D000818:Animals; D052688:Bovine papillomavirus 1 / Q000235:genetics* / Q000502:physiology*; D002460:Cell Line; D002461:Cell Line, Transformed; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D015967:Gene Expression Regulation, Viral; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016366:Open Reading Frames; D010641:Phenotype; D010766:Phosphorylation; D010957:Plasmids; D012694:Serine; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics*; D014779:Virus Replication
D004279:DNA, Viral; D014764:Viral Proteins; D012694:Serine; D004247:DNA