ELAVL1 and ELAVL4 are required for Musashi-dependent translational activation

The RNA-binding proteins Musashi1 and Musashi2 (MSI1 and MSI2) regulate stem cell function and tissue plasticity by modulating mRNA translation. While typically known as translational repressors, the MSI1 and MSI2 proteins can also act as context-dependent activators of mRNA translation, although the mechanism of MSI-mediated translational activation are unknown. Here, we identify Embryonic Lethal Abnormal Vision-like (ELAVL) proteins as essential co-regulators of MSI1-dependent translational activation. In Xenopus laevis oocytes, antisense oligonucleotide knockdown of Elavl4 inhibited progesterone-stimulated maturation and blocked polyadenylation and translation of key MSI target mRNAs, inc