Identification and molecular characterization of the baculovirus CfMNPV early genes: ie-1, ie-2 and pe38

Three early virus genes, ie-1, ie-2 and pe38, were identified and localized in the XbaI G region (91.2–98.6 m.u.) of the genome of Choristoneura fumiferana nucleopolyhedrovirus (CfMNPV), a baculovirus pathogenic to spruce budworm. Nucleotide sequence analysis indicated that these genes share varied sequence similarity with their homologues in other baculoviruses where they are involved in regulating virus gene expression and DNA replication. Sequence motifs characteristic of DNA binding and transactivation found in other baculovirus regulatory genes were conserved in the CfMNPV genes. Northern analysis demonstrated that all three CfMNPV genes were transcriptionally active in virus infected cells and followed the temporal expression pattern of immediate early baculovirus genes. Primer extension experiments revealed that typical baculovirus early transcription start sites (CAGT) were used for ie-1 and pe38 transcription initiation. Two regions of highly repetitive DNA were found in the odv-e56 to ie-2 and ie-2 and pe38 intergenic regions. These sequences are predicted to function as transcriptional enhancers and viral origins of DNA replication.