Interaction between zucchini yellow mosaic potyvirus RNA-dependent RNA polymerase and host poly-(A) binding protein

Viral replication depends on compatible interactions between a virus and its host. For RNA viruses, the viral replicases (RNA-dependent RNA polymerases; RdRps) often associate with components of the host translational apparatus. To date, host factors interacting with potyvirus replicases have not been identified. The Potyviridae, which form the largest and most economically important plant virus family, have numerous similarities with the animal virus family, the Picornaviridae. Potyviruses have a single-stranded, plus sense genome; replication initiates at the viral-encoded, 3' poly-(A) terminus. The yeast two-hybrid system was used to identify host plant proteins associating with the RdRp of zucchini yellow mosaic potyvirus (ZYMV). Several cDNA clones representing a single copy of a poly-(A) binding protein (PABP) gene were isolated from a cucumber (Cucumis sativus L.) leaf cDNA library. Deletion analysis indicated that the C-terminus of the PABP is necessary and sufficient for interaction with the RdRp. Full-length cucumber PABP cDNA was obtained using 5' RACE; in vitro and Escherichia coli-expressed PABP bound to poly-(A)-Sepharose and ZYMY RdRp with or without the presence of poly-(A). This is the first report of an interaction between a viral replicase and PABP and may implicate a role for host PABP in the potyviral infection process.