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Overexpression of actin in AcMNPV-infected cells interferes with polyhedrin synthesis and polyhedra formation
L Volkman1, K Storm, V Aivazachvili
1Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA. lvolkman@nature.berkeley.edu.
Abstract:
Autographa californica M nuclear polyhedrosis virus (AcMNPV) terminates host protein synthesis during the late stage of infection, at approximately 14 hr postinfection (hpi). If infection takes place in the presence of cytochalasin D (CD), however, host actin synthesis is transiently stimulated and continues to be synthesized until approximately 30 hpi, and the hyperexpression of polyhedrin is delayed from about 20 hpi until about 36 hpi (S. N. Talhouk and L. E. Volkman, Virology 182, 626-634, 1991; N. Wei and L. E. Volkman, Virology 191, 42-48, 1992). To investigate whether these events are causally related, i.e., whether actin synthesis negatively affects polyhedrin synthesis, we constructed recombinant viruses that expressed actin at various levels during infection. We found that the expression of actin by a strong promoter interfered with polyhedrin synthesis at a posttranscriptional level. It also interfered with polyhedra formation, which may suggest a mechanism for the observed paucity of polyhedra in infected midgut columnar epithelial cells in vivo.
Insights
Autographa californica M nuclear polyhedrosis virus (AcMNPV) normally stops host protein synthesis. However, increased actin synthesis delays viral polyhedrin production and affects polyhedron formation.
Area of Science:
- Virology
- Molecular Biology
- Insect Pathology
Background:
- Autographa californica M nuclear polyhedrosis virus (AcMNPV) inhibits host protein synthesis late in infection.
- Cytochalasin D treatment prolongs host actin synthesis and delays viral polyhedrin overexpression.
Purpose of the Study:
- To investigate the causal relationship between actin synthesis and polyhedrin synthesis during AcMNPV infection.
- To determine if elevated actin levels negatively impact viral polyhedrin production and polyhedron formation.
Main Methods:
- Construction of recombinant viruses engineered to express actin at varying levels.
- Analysis of polyhedrin synthesis and polyhedron formation in infected cells.
Main Results:
- Expression of actin via a strong promoter significantly interfered with polyhedrin synthesis at a posttranscriptional level.
- Increased actin expression also inhibited the formation of viral polyhedra.
Conclusions:
- Actin synthesis negatively regulates viral polyhedrin production and polyhedron assembly.
- This mechanism may explain the limited polyhedron formation observed in vivo.