Identification, Localization, Transcription, and Sequence Analysis of the Choristoneura Fumiferana Nuclear Polyhedrosis Virus DNA Polymerase Gene

The location of the Choristoneura fumiferana baculovirus DNA polymerase gene was determined by hybridization analysis using a probe prepared from the previously identified polymerase gene from the Autographa californica multiple nuclear polyhedrosis virus. DNA sequence analysis revealed that the Choristoneura fumiferana baculovirus DNA polymerase gene consists of 2970 base pairs encoding 990 amino acids (114.2 kDa). Transcriptional analysis demonstrated that overlapping transcripts of 3.2 and 4.6 kb, first detected at 6 hr postinfection, potentially coded for the DNA polymerase gene. The major transcription starts sites, identified at 6 hr postinfection, mapped to baculovirus consensus early start sites CGTGCTCA and CAGT. The relatively low level and late initiation of the DNA polymerase gene coupled with our previous data on the temporal control of DNA replication and late gene synthesis (Liu and Carstens, 1993) suggests that the low virulence of the spruce budworm baculovirus may be related to the regulation of its gene expression at the transcriptional level.