CHARACTERIZATION OF A DOMAIN OF THE GENOME OF BMNPV CONTAINING A FUNCTIONAL GENE FOR A SMALL CAPSID PROTEIN AND HARBORING DELETIONS ELIMINATING 3 OPEN READING FRAMES THAT ARE PRESENT IN ACNPV

The nucleotide sequence of a 1.5-kb fragment of the genome of Bombyx m ori nuclear polyhedrosis virus (BmNPV) has been determined. An open re ading frame (ORF) has been identified, which encodes a protein of a pr edicted molecular mass of 15 kDa (p15). Analysis of the p15 sequence r evealed that it shares significant similarities with a number of previ ously characterized viral capsid proteins. Two mRNAs, 0.7- and 1.3-kb, are transcribed from the p15 gene. The 0.7-kb transcript appears befo re BmNPV DNA replication, while the 1.3-kb transcript is transcribed o nly after viral DNA replication. The transcription start sites for the 0.7- or 1.3-kb transcripts have been localized into two areas mapping 114 and 557/559 bp upstream of the p15 translation initiation codon, respectively, and the two transcripts appear to share a common poly(A) addition site located 114 bp downstream of the translation terminatio n codon. Comparisons of the nucleotide sequence of the 1.5-kb BmNPV fr agment with that of another isolate of BmNPV and with Autographa calif ornica NPV (AcNPV) genomic DNA reveal that the corresponding region of AcNPV encompasses 4.1 kb of DNA and three additional ORFs that are ab sent from the BmNPV genome. These findings raise questions about the o rigin and functional relevance of the putative polypeptides encoded by the three ORFs of AcNPV.