Unraveling the structural complexity in a single-stranded RNA tail: implications for efficient ligand binding in the prequeuosine riboswitch

Eichhorn, Catherine D.; Feng, Jun; Suddala, Krishna C.; Walter, Nils G.; Brooks, Charles L.; Al-Hashimi, Hashim M.

Single-stranded RNAs (ssRNAs), typically located at the ends of RNA hairpins and consisting of more than three unpaired residues, serve diverse structural and functional roles. They can fold onto neighboring RNA hairpins to form pseudoknots, essential architectural RNA elements involved in ribosomal frameshifting (1, 2) , hepatitis C internal ribosomal entry site (IRES) recognition (3, 4) and telomerase activity (5) . Messenger RNA (mRNA) degradation is prevented or promoted by 3 0 addition of a polyadenylated tail, which recruits essential protein cofactors (6) . Cleavage of the 5 0 transfer RNA (tRNA) leader by RNase P is a key step in tRNA maturation (7) . In riboswitches, ssRNA links the ligand-binding aptamer domain to the expression platform, providing the basis for communication between the two (8) (9) (10) .