Overlapping Divergent Transcripts Mapping to the HindIII F Region of the Autographa Californica Nuclear Polyhedrosis Virus

Department of Biochemistry, University of Kansas, Lawrence, Kansas 66045, U.S.A. We have mapped a set of transcripts that cross the Xho I site in the Hin dIII 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 Xho I 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 Xho I site. Late in infection transcription proceeds in both directions at the same time through the overlapping region of the DNA encoding these transcripts. Present address: Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, U.S.A. Received 12 April 1989; accepted 12 September 1989.