Nuclear F-actin is required for AcMNPV nucleocapsid morphogenesis.

During nucleocapsid assembly, filamentous actin (F-actin) colocalizes with the major capsid protein of Autographa californica M nucleopolyhedrovirus (AcMNPV) within nuclei of infected lepidopteran host cells. Cytochalasin D (CD) disrupts actin filaments and prevents assembly of progeny AcMNPV, suggesting that nuclear F-actin is essential for nucleocapsid morphogenesis. Direct proof for this hypothesis was provided by the demonstration that two AcMNPV recombinants engineered to express either wild-type- or CD-resistant actin at equivalent rates were differentially sensitive to CD. The AcMNPV requirement for nuclear F-actin is unique among intracellular pathogens and may constitute a significant host range factor.