Localization of Germes RNA in Xenopus Oocytes

A Xenopus maternally expressed gene Germes , whose mRNA associates with germ plasm, has been previously identified. In the present study, the cis - and trans -acting factors that regulate the localization of Germes RNA within the developing oocyte have been characterized. Injection of fluorescently labeled RNA corresponding to various parts of the Germes message demonstrated that the sequence information necessary and sufficient for correct localization in the mitochondrial cloud region of the early oocyte is located in the 3'UTR. A domain rich in CAC motifs identified in the distal part of the 3'UTR was found to be sufficient to mediate RNA localization. Within this domain, one nonessential ( a ) and two essential ( b and c ) subdomains were identified. A 37-base region of the c subdomain adjacent to the poly(A) tail was found to be important for localization since its removal from several tested constructs abolished their localization capacity. Analysis of the 3'UTR sequence showed the presence of three different motifs for RNA localization in the oocyte.