Anti-idiotype RNAs that mimic the leucine-rich nuclear export signal and specifically bind to CRM1/exportin 1 Original Research Article

Abstract Background: Anti-idiotype approaches are based on the assumption that an antibody recognising a ligand can be structurally related to the receptor. Recently we have generated anti-idiotype RNA aptamers designed to mimic the human immunodeficiency virus-1 (HIV-1) Rev nuclear export signal (NES). Nuclear injection of either NES–peptide conjugates or aptamer causes the inhibition of Rev-mediated export. This implied that NES mimics and export substrate might compete for binding to the NES receptor. The mechanism of inhibition, however, is unknown. Results: The interaction between the export aptamer and CRM1 was characterised in vitro. The aptamer binds specifically to CRM1 and this interaction is sensitive to competition by Rev NES–peptide conjugates. The recognition domain of CRM1 has been mapped and includes residues found previously to affect binding of leptomycin B, a fungicide interfering with nuclear export. Conclusions: Inhibition of Rev-mediated export in vivo by export aptamers appears to result from the binding of the aptamers to the NES-recognition domain of CRM1. This observation demonstrates that anti-idiotype RNA can mimic faithfully structural and functional properties of a protein and can be used to map ligand-binding domains of receptors. Article Outline