SEQUENCE, FUNCTION, AND PHYLOGENETIC ANALYSIS OF AN ASCOVIRUS DNA-POLYMERASE GENE

We have sequenced a 5.5-kb region of the DNA genome of the Spodoptera Ascovirus (SAV) containing a DNA polymerase gene. The gene codes for a 1104-amino-acid polypeptide with seven motifs characteristic of DNA p olymerases and three additional motifs associated with polymerases pos sessing 3' to 5' exonuclease activity. The SAV DNA polymerase gene was able to functionally substitute for a baculovirus DNA polymerase gene in a transient assay that relies on origin-specific reporter plasmid DNA replication. Analysis of the predicted DNA polymerase sequence usi ng neighbor-joining and protein parsimony algorithms indicated that th is gene was only distantly related to other known viral and cellular D NA polymerases. The SAV DNA polymerase gene is the first ascovirus gen e to be identified and sequenced. The molecular phylogenetic analyses of this gene supports the placement of insect ascoviruses in a separat e virus family. (C) lees Academic Press, Inc.