Comparisons of host cell DNA insertions and altered transcription at the site of insertions in few polyhedra bacilovirus mutants.

Few polyhedgra (FP) mutants of Autographa californica nuclear polyhedrosis virus (AcNPV) and the closely related strain Galleria mellonella (Gm)NPV have been reported which contain Trichoplusia ni host cell DNA sequences inserted into the viral genome between map units 35.0 and 37.7. New FP mutants are described with alterations of the HindIII-I restriction enzyme fragment (33.8 to 37.7 map units) of AcNPV, either deletions of viral DNA sequences or insertions of spodoptera frugiperda host cell DNA sequences. S. frugiperda DNA insertions from FP mutants were compared to T. ni host DNA insertions from FP mutants previously isolated (M.J. Fraser, G.E. Smith, and M.D. Summers (1983) J. Virol. 47, 287-300). Two host cell DNA sequences isolated from FP mutants, one of T. ni origin and one from S. frugiperda DNA, were transcribed in infected cells. Deletions of viral DNA sequences and insertions of host DNA sequences produce altered transcripts at the site of mutation as determined by both Northern and S1 nuclease analysis. Cell-free translation of cRNAs transcribed from wild-type viral DNA revealed an open reading frame coding for a 25-kDa protein at the site where host cell DNA insertions have been mapped. This was the same size as an infected-cell protein missing from most FP mutants examined.