Importantly, a substitution of the RGG repeats of Sbp1 with GS repeats (column 2 in Fig. 6A,C), or methylation of the RGG domain (column 3 in Fig. 6A,C), or deletion of the internal poly(A) sequence (Fig. 6F, columns 2 and 3), diminishes the inhibitory effect of Sbp1 on the Pab1 mRNA. Taken together, our results show that both the RGG domain and poly(A)-sequence of 5′UTRPab1 are important for Sbp1's function in translation of the Pab1 mRNA.