Divergent transcription of early 35- and 94-kilodalton protein genes encoded by the HindIII K genome fragment of the baculovirus Autographa californica nuclear polyhedrosis virus.

The organization of viral genes within the 3.7-kilobase-pair HindIII-K/EcoRI-S region of the Autographa californica nuclear polyhedrosis virus genome (85 to 88 map units) was determined by using a combination of nucleotide sequencing, transcriptional mapping, and in vitro translation of hybrid selected RNA. Two nonoverlapping genes, extending in opposite directions and encoding polypeptides with molecular weights of 35,000 and 94,000 (35K and 94K polypeptides), were identified. Unspliced, messenger-active RNAs were transcribed from both genes early (2 h) after infection. Indicative of immediate-early genes, transcription of the divergent RNAs was unaffected by the protein synthesis inhibitor, cycloheximide. Late in infection, abundant RNAs were transcribed from promoters located at least 2.5 kilobase pairs upstream from the gene encoding the 35K polypeptide. These transcripts completely overlapped both the 35K and 94K polypeptide genes but apparently lacked protein-coding potential, suggesting that the transcripts may play a role in the suppression of early viral gene expression.