Nup153 is a molecular constituent of the nuclear basket of the nuclear pore 
complex (NPC) that plays a critical role in nuclear export of RNAs and proteins. 
In an effort to map this nucleoporin more precisely within the nuclear basket we 
have developed an experimental approach for localizing Nup153 expressed and 
incorporated in vivo into Xenopus oocyte NPCs. This approach involves the 
microinjection into the cytoplasm of Xenopus oocytes of in vitro synthesized 
mRNA from a vector encoding an epitope-tagged cDNA. Here we present results 
obtained by Western blots, fluorescence microscopy, and immuno-electron 
microscopy, which clearly document that the heterologous protein is properly 
expressed, targeted, and incorporated into preexisting Xenopus NPCs. This new 
approach for localizing nucleoporins within the structure of the NPC overcomes 
limitations of previous techniques and allows for greater specificity and 
resolution than have been possible with previous methods.