Co-purification experiments revealed that Ded1p is present in the tombusviral VRC (Figure 1 ). In addition, Ded1p affected (+)strand synthesis, but not the assembly of the VRC in vitro (Figures 2-4) , indicating that Ded1p is likely present in the VRC. Surprisingly, Ded1p, unlike other previously tested host factors Hsp70, GAPDH, or eEF1A [21] [22] [23] 27, 54] , was able to affect TBSV repRNA replication even after the replicase assembly step took place in vitro (Figure 3 ). This suggests that Ded1p can enter the membrane-bound VRC, possibly due to its interaction with p33 ( Figure S6 ) and the helicase activity of Ded1p might lead to some remodeling of VRC.