Time Course Analysis and Mapping of Autographa californica Nuclear Polyhedrosis Virus Transcripts

To study the expression of the Autographa californica nuclear polyhedrosis virus (AcNPV) genome, intracellular virus-specific proteins and mRNAs were pulsed-labeled, extracted, and analyzed at 6-h intervals during the replicative cycle. Most RNAs were detected between 12 and 24 h postinfection (p.i.), but many continued to be synthesized until late in infection. Polyhedrin and p8 mRNAs were the two most abundant late viral RNA transcripts, and they were synthesized at high rates until late in the infection cycle (60 h p.i.). The abundancy control of polyhedrin and p8 polypeptides was considered to be at the level of transcription. Two other major mRNAs in infected cells were 0.6-kilobase RNA, which was synthesized at its highest rate 12 to 18 h p.i., and 2.8-kilobase RNA, which was synthesized from 12 h p.i. until 48 h p.i. Cytoplasmic polyadenylic acid-containing RNA was isolated at 6-h intervals and was analyzed by Northern blot hybridization. At least 50 virus RNA transcripts were recognized, sized, and mapped onto the genome. Six RNAs hybridized to EcoRI-H, -I, and -J, and HindIII-Q AcNPV DNA restriction fragments, seven RNAs hybridized to EcoRI-B and -D DNA fragments, five RNAs hybridized to EcoRI-A and -E regions of the genome, four RNAs hybridized to EcoRI-C and -N DNA fragments, and one RNA species hybridized to EcoRI-O AcNPV DNA. A transcription map of the AcNPV genome was constructed, and the data were correlated with previously published translation maps.