Abstract
Directional transport of specific mRNAs is of primary biological relevance. In Xenopus oocytes, mRNA localization to the vegetal pole is important for germ layer formation and germ cell development. Using a biochemical approach, we identified Xenopus Elr-type proteins, homologs of the Hu/ELAV proteins, as novel components of the vegetal mRNA localization machinery. They bind specifically to the localization elements of several different vegetally localizing Xenopus mRNAs, and they are part of one RNP together with other localization proteins, such as Vg1RBP and XStaufen 1. Blocking Elr-type protein binding by either localization element mutagenesis or antisense morpholino oligonucleotide-mediated masking of their target RNA structures, as well as overexpression of wild type and mutant ElrB proteins, interferes with vegetal localization in Xenopus oocytes.