Consistent with this hypothesis on the importance of RNA binding, the distribution patterns of Sbp1 and Sbp1m (arginine methylated Sbp1) in polysome profiles of 5′UTRPab1 differ substantially, as shown in Figure 8. In this experiment, in vitro translations of 5′UTRPab1 in-frame with the firefly luciferase reporter were carried out in the ΔSbp1 cell extracts in the presence of Sbp1 or methylated Sbp1m. Polysome profiles on the transcript were studied and presence of the protein in different fractions was detected by western blot (see Materials and Methods). As shown in Figure 8, Sbp1 mainly cosediments with RNP and 40S fractions. A small portion of the protein also cosediments with the 80S and polysome fractions. These results are consistent with the observation that tagged Sbp1 was pulled down with 80S and polysomes (Zhang et al. 2014; Wang et al. 2016).