Evidence for a localisation signal in the 3'-untranslated region from vimentin messenger RNA

There is increasing evidence that some mRNAs are localised in eukaryotic somatic cells, but it is unclear what proportion of mRNAs are localised and whether this sorting involves 3'-untranslated sequences. The presence of a localisation signal within the 3'-untranslated region of vimentin mRNA was investigated by studying mRNA distribution in fibroblasts transfected with beta-globin and hybrid globin-vimentin gene constructs. In cells transfected with constructs containing either a fragment of the rabbit beta-globin gene containing both coding sequences and 3'untranslated region or the beta-globin coding sequences alone in situ hybridisation showed that beta-globin mRNA was distributed throughout the cytoplasm without any evident localisation. In contrast, in cells transfected with globin coding sequences linked to the vimentin 3'-untranslated region there was a strong perinuclear localisation of the hybrid mRNA. The results show that loss of its endogenous 3'-untranslated region does not affect distribution of beta-globin mRNA whereas the vimentin 3'-untranslated region causes an altered localisation of beta-globin mRNA. We conclude that the vimentin 3'-untranslated region contains a localisation signal which can direct reporter sequences to the perinuclear cytoplasm.