Baculovirus transcription in the presence of inhibitors and in nonpermissive Drosophila cells

Regulation of transcription within four well-defined regions of the DNA genome of the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) was studied in a permissive lepidopteran cell line. Spodoptera frugiperda IPLB-SF-21 and a nonpermissive dipteran cell line, Drosophila melanogaster DL-1. Cycloheximide, an inhibitor of protein synthesis, was used to identify immediate early transcripts and aphidicolin, an effective inhibitor of DNA replication, was used to distinguish early and late transcripts in S. frugiperda cells. Immediate early transcripts were identified in the HindIII-K (85 to 87.5%), the HindIII-I/EcoRI-F (I/F from 35 to 37%) and the HindIII-P/EcoRI-P (p10 from 88.5 to 89.5%) regions of the genome. Late RNAs, defined by their sensitivity to aphidicolin as well as cycloheximide, overlapped the immediate early RNAs. Specific viral transcripts were synthesized in nonpermissive D. melanogaster cells infected with AcNPV but late viral transcripts were not observed.