Characterization of φ12, a Bacteriophage Related to φ6: Nucleotide Sequence of the Large Double-Stranded RNA

Abstract

The isolation of additional bacteriophages besides φ6 containing segmented double-stranded RNA genomes (dsRNA) has expanded the Cystoviridae family to nine members. Comparing the genomic sequences of these viruses has allowed evaluation of important genetic as well as structural motifs. These comparative studies are resulting in greater understanding of viral evolution and the role played by genetic and structural variation in the assembly mechanisms of the cystoviruses. In this regard, the large double-stranded RNA genomic segment of bacteriophage φ12 was copied as cDNA and its nucleotide sequence determined. This genome's organization is similar to that of the large segment of bacteriophages φ6, φ8, and φ13. In the amino acid sequence of the viral RNA-dependent RNA polymerase (P2), similarity was found to the comparable proteins of φ6, φ8, and φ13. Amino acid sequence similarity was also noted in the nucleotide triphosphate phosphorylase (P4) to the comparable proteins of φ8 and φ13.