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Autographa californica MNPV nucleocapsid assembly: inhibition by cytochalasin D
1Department of Entomology, University of California, Berkeley 94720.
Abstract:
Autographa californica nuclear polyhedrosis virus (AcMNPV) is a large, double-stranded DNA virus of lepidopteran insects. It replicates in the nucleus of host cells and produces two different infectious forms. One of them buds from the plasma membrane and is responsible for systemic infection in insects and for the spread of infection in cell culture. Earlier we reported that cytochalasin D (CD) inhibited the production of this form of the virus in infected IPLB-SF-21 cells by a mechanism other than the prevention of budding [L. E. Volkman, P. A. Goldsmith, and R. T. Hess (1987). Virology 156, 32-39]. Herein we present evidence that CD interferes with proper nucleocapsid assembly which indicates that microfilaments are involved in this nuclear process. The observation that phalloidin localizes in the nuclei of 24-hr infected cells in the absence, but not in the presence, of CD supports this hypothesis. Viral DNA replication and synthesis of the major capsid antigen and its transport to the nucleus are not inhibited by CD.
Insights
Cytochalasin D (CD) disrupts Autographa californica nuclear polyhedrosis virus (AcMNPV) nucleocapsid assembly in insect cells. This suggests microfilaments play a role in the nuclear process of viral replication.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Autographa californica nuclear polyhedrosis virus (AcMNPV) is a significant pathogen of lepidopteran insects.
- AcMNPV replicates within host cell nuclei, producing infectious virions.
- Previous research indicated cytochalasin D (CD) inhibits AcMNPV production without preventing viral budding.
Purpose of the Study:
- To investigate the mechanism by which cytochalasin D (CD) affects Autographa californica nuclear polyhedrosis virus (AcMNPV) replication.
- To determine if microfilaments are involved in the nuclear assembly of AcMNPV.
Main Methods:
- Treatment of infected IPLB-SF-21 cells with cytochalasin D (CD).
- Localization studies using phalloidin to detect microfilaments in infected cells.
- Assessment of viral DNA replication, major capsid antigen synthesis, and nuclear transport.
Main Results:
- Cytochalasin D (CD) was found to interfere with proper nucleocapsid assembly.
- Phalloidin staining indicated microfilament localization within the nuclei of infected cells, which was reduced by CD treatment.
- CD did not inhibit viral DNA replication, major capsid antigen synthesis, or antigen transport to the nucleus.
Conclusions:
- Microfilaments are implicated in the nuclear process of AcMNPV nucleocapsid assembly.
- CD's inhibition of AcMNPV production is likely due to its interference with nucleocapsid assembly, not budding.
- This study highlights a novel role for microfilaments in viral nuclear processes.