To test whether there is a direct interaction between Sbp1 and Pab1, we performed a glutathione S-transferase (GST) pull-down assay using purified GST-Pab1 and Sbp1 proteins. As shown in Figure 3A (lane 3), Sbp1 is pulled down by Pab1 only in the presence of 5′UTRPab1 RNA. Addition of RNase A abolishes the protein–protein interaction (Fig. 3A, cf. lanes 3 and 4), suggesting that the interaction between Pab1 and Sbp1 is RNA-dependent.