To obtain direct evidence on the involvement of eEF1Bc in TBSV replication, we prepared cell-free extracts (CFE) from a yeast strain lacking the TEF4 gene or from wt yeast. These yeast extracts contained comparable amount of total proteins ( Figure 1C , right panel). The CFE extracts were programmed with the TBSV (+)repRNA and purified recombinant p33 and p92 pol obtained from E. coli. Under these conditions, the CFE supports the in vitro assembly of the viral replicase, followed by a single cycle of complete TBSV replication, resulting in both (-)-stranded repRNA and excess amount of (+)-stranded progeny [20, 34] . Importantly in the case of a translation factor, this assay uncouples the translation of the viral proteins from viral replication, which are interdependent during (+)RNA virus infections. CFE obtained from tef4D yeast supported only 29% of TBSV repRNA replication when compared with the extract obtained from wt yeast ( Figure 1C , lane 2 versus 4). These data demonstrate that Tef4p plays an important role in the activity of the viral replicase complex.