Abstract
In transient expression assays, hycu-hr6, the largest homologous region (hr) among the six hrs identified in the genome of Hyphantria cunea nucleopolyhedrovirus (HycuNPV) has been shown to stimulate the activity of an early promoter of the HycuNPV gp64 gene (hycu-gp64) which is located immediately downstream of hycu-hr6. In this study, we generated a recombinant HycuNPV defective in hycu-hr6 (vHycuΔhr6) and characterized its biological properties in permissive SpIm cells. Analyses by Northern blotting and immunoblotting showed that the transcription of hycu-gp64 in vHycuΔhr6-infected SpIm cells was significantly lower than that in HycuNPV-infected SpIm cells until 12 h postinfection, and the observed difference in hycu-gp64 transcription was reflected in the production of Hycu-GP64 protein in the infected cells. In later stages of viral infection, however, no substantial difference was observed between vHycuΔhr6 and HycuNPV in both hycu-gp64 transcription and Hycu-GP64 protein production. Viral DNA replication also showed no substantial difference between vHycuΔhr6 and HycuNPV throughout the experiments. Furthermore, there were little, if any, differences in the ultimate yields of budded virions (BVs) and polyhedrin between vHycuΔhr6 and HycuNPV. These results demonstrate that vHycuΔhr6 is able to complete its infection cycle in SpIm cells and yields BVs and polyhedrin at levels comparable to those of HycuNPV, indicating that hycu-hr6 is a dispensable viral element for HycuNPV replication in SpIm cells.
© 2006 by Japan Academic Association for Copyright Clearance (Except in the USA), Copyright Clearance Center, Inc. (In the USA)
