UBC Theses and Dissertations

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UBC Theses and Dissertations

Functional comparison and analysis of protein-protein interactions of Autographa californica multiple nucleopolyhedrovirus transregulatory proteins IE0 and IE1 Nie, Yingchao


Autographa californica multiple nucleopolyhedrovirus expresses two major transregulatory proteins IE0 and IE1 immediately upon infection. IE0 differs from IE1 only by 54 additional N-terminal amino acids (aa). Either IE0 or IE1 can support viral replication; however both are required for a wild-type infection. It is unknown what the different functions of IE0 and IE1. Both IE0 and IE1 can transactivate viral early genes and support viral DNA replication. It is therefore hypothesized that by the addition of Nterminal 54 aa, IE0 acquires different transactivation activity on viral genes and interacts with different viral or host partners. To test this hypothesis, functional comparisons between IE0 and IE1 and the identification of their interaction partners in infected cells were performed. Comparisons of subcellular localization and transactivation activities between IE0 and IE1 showed no difference. However analyses of the nucleocapsid content of occlusion derived virions (ODV) revealed that IE0 and IE1 appear to regulate the number of nucleocapsids per ODV. Deletion within the IE0 specific N-terminal 54 aa did not affect IE0 transactivation dramatically but reduced its ability to support viral DNA replication. Analyses of interacting proteins did not identify any proteins that were specific to either with IE0 or IE1. However, the viral protein AC16 (BV/ODV-E26) was shown to bind to both IE0 and IE1 via a binding domain at IE1 72-99 aa. Mutation of the binding domain enhanced budded virus (BV) production by viruses expressing only IE0 but not IE1. Deletion of ac16 however resulted in increased levels of IE0 relative to IE1 as the only observable impact. These results would therefore indicate that AC16 regulates ie0 expression. Deletion of ac16 and the overlapping gene ac17, interestingly resulted in a significant delay of viral gene expression for up to 12 hours. However, the delay of viral gene expression was only observed with BV-infected cells and not in cells infected by transfecting viral DNA. AC16 and AC17 are therefore critical for rapid gene expression during the very early events of infection, and highlight the fact that proteins interacting with IE0 and IE1 play key roles in baculovirus biology.

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