Characterization of bro-a gene of Spodoptera litura multicapsid nucleopolyhedrovirus

Spodoptera litura multicapsid nucleopolyhedrovirus (SpltMNPV) ORF120 (designated as the bro-a gene) is a member of the unique multigene family called the baculovirus repeated ORFs (bro) family. Computer-assisted analysis revealed that BRO-A does not contain the conserved Bro-N domain in its N-terminus, but contains a single-stranded DNA binding motif near its C-terminus. Transcriptional analysis indicated that bro-a transcript initiated within a baculovirus consensus early start site motif (ATCAGT). In vitro the bro-a gene transcript was present at 12 h post infection (p.i.) and remained detectable up to 96 h p.i. Western blot analysis of BRO-A expression in SpltMNPV infected S. litura cells showed that it was present from 72 h to 96 h p.i. in vitro. Analysis of extracts from nuclear structures indicated that BRO-A could not be extracted with DNA or proteins which bind to DNA.