A paradigm for regulation at the effector interface with RNA-binding proteins.

RNA-binding proteins (RBPs) are key regulators of gene expression, but how RBPs convey regulatory instructions to the core effectors of RNA processing is unclear. We address this problem by dissecting the effector interface responsible for regulation by a developmentally essential RBP. We show that the sequence-specific RBP Unkempt, in addition to its RNA-binding domain, contains an extensive intrinsically disordered region (IDR) and a dimerization domain, all of which distinctly contribute to Unkempt's function. Within IDR, we identify an array of linear motifs that support direct contact with two central effectors, the CCR4-NOT complex and PABPC. The spatial arrangement, dual-purpose motifs, and obligate homodimerization allow for high-avidity effector interactions that are mandatory for the accuracy of RNA targeting, translational repression, and control of cell morphology by Unkempt. Our study establishes the molecular assembly and functional principles of an RBP- effector interface, with general implications for the evolution and function of RBP-operated regulatory networks.