Nucleotide sequence and transcriptional analysis of a putative basic DNA-binding protein of Helicoverpa armigera nucleopolyhedrovirus

A putative basic DNA-binding protein (BDBP) gene was identified in the frag ment EcoRI-K of the Helicoverpa armigera single-nucleocapsid nucleopolyhedr ovirus (HearNPV) genome. The ORF is 330 nucleotides long encoding a basic p rotein of 109 amino acids with a molecular mass of 11.6 kDa. It is the firs t BDBP identified in single nucleocapsid NPVs and a homologue of Autographa californica MNPV (AcMNPV) P6.9. A consensus late transcription motif, ATAA G, was found at 57 nt upstream of the translational start codon and a polya denylation signal was observed at 172 nt downstream of the stop codon. A ma jor transcript of 620 nt was first observed in HearNPV-infected Hz2e5 cells 16 h post infection. Primer extension analysis revealed that this transcri pt initiated from the first residue of the consensus ATAAG late transcripti on start motif. Comparison with other baculoviral BDBPs showed that they al l contained two conserved cAMP- and cGMP-dependent protein kinase phosphory lation motifs, R-R-R-S. The HearNPV P6.9 homologue is the longest BDBP foun d so far in baculoviruses.