In addition to RNA binding, the RGG domain of Sbp1 is important for the function of Sbp1. Substitution of the RGG repeats with GS repeats, or methylation of arginines in the RGG repeats, abolishes the inhibitory function of Sbp1 on the Pab1 mRNA in both cap-dependent and cap-independent initiation pathways (Fig. 6A,C).