ABSTRACT N6 -methyladenosine (m 6 A) exerts many of its regulatory effects on eukaryotic mRNAs by recruiting cytoplasmic YT521-B homology domain family (YTHDF) proteins. Here, we show that in Arabidopsis, the interaction between m 6 A and the major YTHDF protein ECT2 also involves the mRNA-binding ALBA protein family. ALBA and YTHDF proteins physically associate via a deeply conserved short linear motif in the intrinsically disordered region of YTHDF proteins, their mRNA target sets overlap, and ALBA4 binding sites are juxtaposed to m 6 A sites. These binding sites correspond to pyrimidine-rich elements previously found to be important for m 6 A binding of ECT2. Accordingly, both biological functions of ECT2 and its binding to m 6 A targets in vivo require ALBA association. Our results introduce the YTHDF-ALBA complex as the functional cytoplasmic m 6 A-reader in plants and define a molecular foundation for the concept of facilitated m 6 A reading that increases the potential for combinatorial control of biological m 6 A effects.

ALBA proteins facilitate cytoplasmic YTHDF-mediated reading of m6A in plants