Characterization of an early gene orf122 from Bombyx mori nucleopolyhedrovirus

The open reading frame 122 of Bombyx mori nucleopolyhedrovirus (BmNPV) (Bm122) has been observed to be a conserved gene in the lepidopteran baculoviruses that have been completely sequenced so far. Its transcript was detected at 3 h post infection (h p.i.) and remained detectable at up to 96 h p.i. Temporal transcription analysis indicated that Bm122 is transcribed by host RNA polymerase. The size of the translational product of the Bm122 gene in Tn5B-1-4 cells was approximately 23 kDa, which is in agreement with the predicted value of 22.9 kDa, suggesting that no major posttranslational modification occurred in the primary protein product. The subcellular localization of Bm122 was studied using EGFP-Bm122, which revealed that Bm122 protein was accumulated within the nuclear region of virus-infected BmN cells. All these results suggest that Bm122 is an early gene encoding a protein that functions in the nucleus.