Multimerization of ELAV is essential for directing neuronal alternative splicing and polyadenylation programs

How ELAV/Hu RBPs achieve gene-specific regulation by recognizing spaced U-rich motifs through multimerization, remains uncertain. We determined X-ray crystal structures of ELAV RNA recognition motif 3 (RRM3) to reveal that multimerization is mediated by two evolutionary-conserved interfaces in non-RNA binding parts of the RRM to form a tetramer.

Mutational probing of these two interfaces in photoreceptor neurons shows that both contribute to ELAV function in development. Although RRM3 binds RNA, this feature is not required for neuronal alternative splicing in this assay in contrast to multimerization. Notably, multimerization defective elav mutants are embryonic lethal.