Characterization of a late expression gene, Open reading frame 128 of Helicoverpa armigera single nucleocapsid...

Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HearSNPV) is a single embedded NPV pathogenic to the bollworm, which is a major agricultural pest in many areas around the world. Ha128 homologues have been identified in all completely sequenced lepidopteran NPV's, but no homologue has been found in a granulovirus (GV) and it is thus considered as a lepidopteran NPV-specific gene. In the HearSNPV-C1 genome Ha128 is located between 120,252 and 121,052 bp and encodes a putative protein of 266 amino acid residues with a predicted molecular weight of 30.5 kDa. Ha128 transcripts in HearSNPV-infected HzAM1 cells could be detected from 24 to 120 h post-infection (p.i.) by Northern blot. The Ha128 protein was detected at 24 h p.i. and remained detectable until 120 h p.i. by western blot using an anti-GST-Ha128 antiserum. The expression of Ha128 was inhibited in the presence of Ara-C, an inhibitor of viral DNA synthesis. These results together indicated that Ha128 was a late gene. The product of Ha128 was found to have an Mr of about 31 kDa, in agreement with the predicted molecular weight. Immunoflorescence using anti-GST-Ha128 serum showed that Ha128 was located in cytoplasm. GST pull-down and co-immunoprecipitation showed that at least two potential host proteins interacted with Ha128. In conclusion, Ha128 is a late protein localized in the cytoplasm of infected cells that may interact with host proteins.