fatvg encodes a new localized RNA that uses a 25-nucleotide element (FVLE1) to localize to the vegetal cortex of Xenopus oocytes

Vegetally localized transcripts have been implicated in a number of importa nt biological functions, including cell fate determination and embryonic pa tterning. We have isolated a cDNA,fatvg, which encodes a localized maternal transcript that exhibits a localization pattern reminiscent of Vg1 mRNA.fa tvg is the homologue of a mammalian gene expressed in adipose tissues, The fatvg transcript, unlike Vg1 which localizes strictly through the Late path way, also associates with the mitochondrial cloud that is characteristic of the METRO or Early pathway. This suggests that fatvg mRNA may utilize both the METRO and Late pathways to localize to the vegetal cortex during oogen esis, We have dissected the cis-acting localization elements of fatvg mRNA and compared these elements with Vg1 mRNA. Our results indicate that, like most localized RNAs, in a variety of systems, transcripts of fatvg contain localization elements in the 3'UTR, The 3'UTR of fatvg mRNA contains multip le elements that are able to function independently; however, it functions most efficiently when all of the elements are present, We have defined a sh ort 25-nucleotide element that can direct vegetal localization as a single copy. This element differs in sequence from previously described Vg1 locali zation elements, suggesting that different localization elements are involv ed in the localization of RNAs through the Late pathway.