Functional antagonism model of effects of CELF and MBNL proteins on mRNA fates. (A) Summary of known nonsplicing activities: CELF1 binding to 3′ UTRs promotes mRNA deadenylation and decay (Vlasova and Bohjanen 2008), while MBNL1 binding to 3′ UTRs promotes localization to membrane compartments (Wang et al. 2012). (B) Binding of both proteins to the same mRNA is expected to result in a functional tug-of-war. For mRNAs containing distal MBNL and CELF binding sites, MBNL promotes targeting of the mRNA for localization and stabilization, while CELF binding promotes decay. For mRNAs containing proximal MBNL and CELF binding sites, CELF1 may directly antagonize MBNL1 function, e.g., by preventing recruitment of complexes associated with localization or inhibiting their function.
