5′UTRs of mRNAs regulate translation via a diverse set of mechanisms (Sonenberg and Hinnebusch 2009; Jackson et al. 2010; Ingolia et al. 2011; Brar et al. 2012; Hinnebusch and Lorsch 2012; Archer et al. 2016; Hinnebusch et al. 2016). Most notably, the 5′UTR of an mRNA often harbors binding sites for regulatory proteins and translational factors. These RNA-binding proteins (RBPs) are versatile not only in their ways of recognizing partner RNAs but also in interacting with other proteins, which enables them broad yet unique functions in regulating post-transcriptional gene expression (Keene and Tenenbaum 2002; Hogan et al. 2008).