To test if the decrease in TBSV repRNA replication in vitro was due to reduced (+) or (-)-strand synthesis, we measured the replication products under non-denaturing versus denaturing conditions ( Figure 1C ). We found that the amount of dsRNA [representing the newly-synthesized 32 P-labeled (-)RNA product hybridized with the input (+)RNA; lane 1, Figure 1C , see also ref. [23] ] and the newly-synthesized (+)RNA both decreased by ,3fold in CFE obtained from tef4D yeast in comparison with those products in the wt CFE (lane 3). Since the ratio of dsRNA and ssRNA did not change much in the CFEs ( Figure 1C ), the obtained data are consistent with the model that Tef4p (eEF1Bc) affects the level of (-)RNA production, which then leads to proportionately lower level of (+)RNA progeny.