PROTEIN-SYNTHESIS EDITING BY A DNA APTAMER

Potential errors in decoding genetic information are corrected by tRNA -dependent amino acid recognition processes manifested through editing reactions. One example is the rejection of difficult-to-discriminate misactivated amino acids by tRNA synthetases through hydrolytic reacti ons. Although several crystal structures of tRNA synthetases and synth etase-tRNA complexes exist, none of them have provided insight into th e editing reactions. Other work suggested that editing required active amino acid acceptor hydroxyl groups at the 3' end of a tRNA effector. We describe here the isolation of a DNA aptamer that specifically ind uced hydrolysis of a misactivated amino acid bound to a tRNA synthetas e. The aptamer had no effect on the stability of the correctly activat ed amino acid and was almost as efficient as the tRNA for inducing edi ting activity. The aptamer has no sequence similarity to that of the t RNA effector and cannot be folded into a tRNA-like structure. These an d additional data show that active acceptor hydroxyl groups in a tRNA effector and a tRNA-like structure are not essential for editing, Thus , specific bases in a nucleic acid effector trigger the editing respon se.