Overlapping divergent transcripts mapping to the HindIII F region of the Autographa californica nuclear polyhedrosis virus.

We have mapped a set of transcripts that cross the XhoI site in the HindIII F fragment of the genome of the Autographa californica nuclear polyhedrosis virus. These transcripts overlap at their 5' ends by about 550 bases and run in opposite directions. We have tentatively identified two open reading frames corresponding to the leftward transcript. The rightward transcript is present from 8 h post-infection (p.i.) to 24 h p.i.; the leftward transcripts are present from 2 h p.i. to 24 h p.i. The early (2 h) transcript is about 2.1 kb in size and its 5' end maps about 504 bp to the right of the XhoI site. Beginning at about 8 h p.i. a new transcription start site is used, about 80 bp downstream (to the left) of the first. The late (rightward) transcript is about 1.2 kb in size; its 5' end seems to be heterogeneous and maps about 44 to 60 bp to the left of the XhoI site. Late in infection transcription proceeds in both directions at the same time through the overlapping region of the DNA encoding these transcripts.