Tombusviruses, similar to other (+)RNA viruses, subvert a yet unknown number of host-coded proteins to facilitate robust virus replication in infected cells. The co-opted host proteins could be part of the viral replicase complexes and provide many yet undefined functions. Translation factors, such as eEF1Bc and eEF1A, are among the most common host factors recruited for (+)RNA virus replication [23, 24] . While eEF1A is an integral component of the tombusvirus replicase complex [23, 24] and several other viral replicases [44, 45, 46] , the function of eEF1Bc in tombusvirus replication is studied in this paper. Co-purification experiments with the p33 replication protein, which is the most abundant protein component in the tombusvirus replicase complex [21, 22] , revealed that eEF1Bc is a permanent member of the replicase ( Figure 5A ). eEF1Bc is likely recruited into the viral replicase via the viral (+)RNA, which is bound to eEF1Bc in both cytosolic and membranous fractions ( Figure 5B ). The possible role of host proteins or membrane lipids in assisting the recruitment of eEF1Bc for TBSV replication cannot be excluded. Accordingly, eEF1Bc has been shown to bind to a large number of host proteins (www.yeastgenome.org). For example, eEF1A, which is also a permanent member of the tombusvirus replicase, is known to interact with eEF1Bc [47, 48, 49] and eEF1A might facilitate the recruitment of eEF1Bc and possibly other translation factors. The binding of eEF1Bc to intracellular membranes has also been shown before [32] . Altogether, our model predicts that the viral (+)RNA could be involved in recruitment of eEF1Bc into viral replication ( Figure 5) . However, the opposite model that eEF1Bc facilitates the recruitment of the TBSV (+)RNA into replication is not supported by our in vitro data ( Figure S2) . Indeed, addition of eEF1Bc to the CFE assay did not increase the membrane-bound fraction of TBSV (+)repRNA in the absence or presence of the viral replication proteins ( Figure S2 ). eEF1Bc selectively enhances minus-strand synthesis by opening the closed 39-terminus during TBSV RNA replication