Host factors with regulatory roles in tombusvirus replication.

Similar to animal viruses, the abundant plant positive-strand RNA viruses replicate in infected cells by exploiting the vast resources of the host. This review focuses on virus-host interactions during tombusvirus replication. The multifunctional tombusvirus p33 replication protein not only interacts with itself, the viral p92(pol) polymerase, and viral RNA, but also with approximately 100 cellular proteins and subcellular membranes. Several negative regulatory host proteins, such as cyclophilins and WW motif containing proteins, also bind to p33 and interfere with p33's functions. To explain how p33 can perform multiple functions, we propose that a variety of interactions involving p33 result in the commitment of p33 molecules to specific tasks. This facilitates tight spatial and temporal organization of viral replication in infected cells.