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Journal of Virology, December 2008, p. 12356-12364, Vol. 82, No. 24
0022-538X/08/$08.00+0 doi:10.1128/JVI.00948-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, China,1 Department of Biochemistry and Center for Cancer Research, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China2
Received 6 May 2008/ Accepted 6 October 2008
It has been shown that the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) 38K (ac98) is required for nucleocapsid assembly. However, the exact role of 38K in nucleocapsid assembly remains unknown. In the present study, we investigated the relationship between 38K and the nucleocapsid. Western blotting using polyclonal antibodies raised against 38K revealed that 38K was expressed in the late phase of infection in AcMNPV-infected Spodoptera frugiperda cells and copurified with budded virus (BV) and occlusion-derived virus (ODV). Biochemical fractionation of BV and ODV into the nucleocapsid and envelope components followed by Western blotting showed that 38K was associated with the nucleocapsids. Immunoelectron microscopic analysis revealed that 38K was specifically localized to the nucleocapsids in infected cells and appeared to be distributed over the cylindrical capsid sheath of nucleocapsid. Yeast two-hybrid assays were performed to examine potential interactions between 38K and nine known nucleocapsid shell-associated proteins (PP78/83, PCNA, VP1054, FP25, VLF-1, VP39, BV/ODV-C42, VP80, and P24), three non-nucleocapsid shell-associated proteins (P6.9, PP31, and BV/ODV-E26), and itself. The results revealed that 38K interacted with the nucleocapsid proteins VP1054, VP39, VP80, and 38K itself. These interactions were confirmed by coimmunoprecipitation assays in vivo. These data demonstrate that 38K is a novel nucleocapsid protein and provide a rationale for why 38K is essential for nucleocapsid assembly.
Published ahead of print on 15 October 2008.
Supplemental material for this article may be found at http://jvi.asm.org/.
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