To examine if Ded1p is present within the tombusvirus replicase complex, we FLAG affinity-purified the tombusvirus replicase from yeast cells actively replicating TBSV repRNA [14, 28] . This yeast also expressed HA-tagged Ded1p from yeast chromosome based on the native promoter. We found that the tombusvirus replicase preparation, which is highly active on added templates in vitro (not shown), contained Ded1p ( Figure 1 , lane 4), while Ded1p was undetectable in the control yeast sample obtained using the same affinity purification ( Figure 1 , lane 3). The control yeast also expressed the tombusvirus replication proteins (including the 66His-tagged p33, but lacking FLAG-tag) and the HA-tagged Ded1p from yeast chromosome based on the native promoter and supported TBSV repRNA replication (not shown).