40LoVe interacts with Vg1RBP/Vera and hnRNP I in binding the Vg1-localization element.

Localizing mRNAs within the cytoplasm gives cells the ability to spatially restrict protein production, a powerful means to regulate gene expression. Localized mRNA is often visible in microscopically observable particles or granules, and the association of mRNA localization with these structures is an indication that particles or granules may be essential to the localization process. Understanding how such structures form will therefore be important for understanding the function of localization RNPs (L-RNPs). We previously identified a novel component of an L-RNP from the Vg1 mRNA from Xenopus oocytes called 40LoVe. 40LoVe interaction with the Vg1-localization element (Vg1LE) was previously shown to be dependent on the VM1 and E2 sequence motifs within the Vg1LE that cross-link to hnRNP I and Vg1RBP/Vera, respectively. We report interaction of these motif-binding proteins with 40LoVe and identify a 40LoVe-Xenopus hnRNP D/AUF1 interaction. We further demonstrate that titration of VM1 and E2 motif binding activity in vivo surprisingly suggests that the motif binding proteins have differing roles during Vg1LE-dependent mRNA localization.