Characterization of Ha29, a specific gene for Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus

Open reading frame 29 (ha29) is a gene specific for Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HearSNPV). Sequence analyses showed that the transcription factor Tfb2 motif, bromodomain and Half-A-TPR (HAT) repeat were present at aa 66-82, 4-76, 55-90 of the Ha29 protein respectively. The product of Ha29 was detected in HearSNPV-infected HzAM1 cells at 3 h post-infection. Western blot analysis using a polyclonal antibody produced by immunizing a rabbit with purified GST-Ha29 fusion protein indicates that Ha29 is an early gene. The size of Ha29 product in infected HzAM1 cells was about 25 kDa, which was larger than the presumed size of 20.4 kDa. Tunicamycin treatment of HearSNPV-infected HzAM1 cells suggested that the Ha29 protein is N-glycosylated. Fluorescent confocal laser scanning microscope examination, and Western blot analysis of purified budded virus (BVs), occlusion-derived virus (ODVs), cell nuclear and cytoplasmic fraction, showed that the Ha29 protein was localized in the nucleus. Our results suggested that ha29 of HearSNPV encodes a non-structurally functional protein that may be associated with virus gene transcription in Helicoverpa hosts.