Physical mapping of temporally regulated, overlapping transcripts in the region of the 10K protein gene in Autographa californica nuclear polyhedrosis virus.

We investigated transcriptional activity in the region of a gene for a major late protein (10 kilodaltons) of Autographa californica nuclear polyhedrosis virus. This 10K protein gene spans an HindIII cleavage site, with the 5' end of the gene located in the HindIII-Q fragment and the 3' end in the HindIII-P fragment. Northern blot analysis showed that there were at least four transcripts mapping in this region, two that are present maximally at 12 h (1,500 and 1,100 bases in length) and two that are present at 24 h (750 and 2,500 bases in length). Northern blot analysis also suggested that these transcripts overlap. S1 mapping identified the precise positions of the transcripts and confirmed the overlap. The 1,500- and 1,100-base transcripts share a common 5' end, about 1,056 bases upstream from the HindIII-P-Q boundary; the 750- and 2,500-base transcripts share a common 5' end, about 303 bases upstream from the HindIII-P-Q boundary. The 1,100-base transcript terminates in the Q fragment, about 234 bases from the HindIII-P-Q boundary. The other three transcripts all end in the P fragment. Both the 1,500- and the 750-base transcripts terminate approximately 240 bases from the HindIII-P-Q boundary. The 2,500-base transcript exhibits 3'-end heterogeneity, ending around 2,046 bases from the HindIII-P-Q boundary. Therefore, three different transcripts (1,500, 750, and 2,500 bases in length) contain the complete 10K protein coding region. A fourth transcript (1,100 bases in length) overlaps the 750-base 10K protein gene transcript by 70 bases.