The p6.5 gene region of a nuclear polyhedrosis virus of Orgyia pseudotsugata: DNA sequence and transcriptional analysis of four late genes.

The gene encoding the basic DNA-binding protein (p6.5) of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (OpMNPV) was localized by Southern blot analysis using a cDNA probe containing the Autographa californica virus (AcMNPV) p6.9 gene. The OpMNPV p6.5 gene was mapped to the HindIII G fragment at map unit 67. Nucleotide sequence and transcriptional analysis of a 3.26 kb region encompassing this area revealed four open reading frames (ORFs 1 to 4) oriented in the same direction. ORF 1 demonstrated a seven codon overlap with ORF 2. Messenger RNAs initiated upstream of each of the four ORFs late in infection and were coterminal at a single site downstream of the fourth ORF. The conserved late gene promoter/mRNA start site sequence (ATAAG) was present upstream of all the ORFs, but did not appear to be the major site of mRNA initiation for the third ORF, as determined by primer extension analysis. The fourth ORF in this series encoded a predicted peptide of 51 amino acids (6.5K), which was 80% similar to the p6.9 basic DNA-binding protein of AcMNPV.