Membrane targeting of an alpha-like tetravirus replicase is directed by a region within the RNA-dependent RNA polymerase domain.

The members of the family Tetraviridae are small positive-sense insect RNA viruses that exhibit stringent host specificity and a high degree of tissue tropism, suggesting that complex virus-host interactions are likely to occur during infection and viral replication. The alpha-like replicase of Helicoverpa armigera stunt virus (HaSV) (genus Omegatetravirus) has been proposed to associate with membranes of the endocytic pathway, which is similar to Semliki Forest virus, Sindbis virus and rubella virus. Here, we have used replicase-EGFP fusion proteins and recombinant baculovirus expression to demonstrate that the HaSV replicase associates strongly with cellular membranes, including detergent-resistant membranes, and that this association is maintained through a novel membrane targeting domain within the C-terminal region of the RNA-dependent RNA polymerase domain. We show a similar subcellular localization and strong association with detergent-resistant membranes for the carmo-like replicase of another tetravirus, Providence virus, in replicating cells, suggesting a common site of replication for these two tetraviruses.