Download MendeleyUnusual Base Pair between Two 2-Thiouridines and Its Implication for Nonenzymatic RNA Copying.
Ding, D., Fang, Z., Kim, S.C., O'Flaherty, D.K., Jia, X., Stone, T.B., Zhou, L., Szostak, J.W.(2024) J Am Chem Soc 146: 3861-3871
- PubMed: 38293747
- DOI: https://doi.org/10.1021/jacs.3c11158
- Primary Citation of Related Structures:
8FEO, 8FEP, 8FEQ, 8FER - PubMed Abstract:
2-Thiouridine (s 2 U) is a nucleobase modification that confers enhanced efficiency and fidelity both on modern tRNA codon translation and on nonenzymatic and ribozyme-catalyzed RNA copying. We have discovered an unusual base pair between two 2-thiouridines that stabilizes an RNA duplex to a degree that is comparable to that of a native A:U base pair. High-resolution crystal structures indicate similar base-pairing geometry and stacking interactions in duplexes containing s 2 U:s 2 U compared to those with U:U pairs. Notably, the C═O···H-N hydrogen bond in the U:U pair is replaced with a C═S···H-N hydrogen bond in the s 2 U:s 2 U base pair. The thermodynamic stability of the s 2 U:s 2 U base pair suggested that this self-pairing might lead to an increased error frequency during nonenzymatic RNA copying. However, competition experiments show that s 2 U:s 2 U base-pairing induces only a low level of misincorporation during nonenzymatic RNA template copying because the correct A:s 2 U base pair outcompetes the slightly weaker s 2 U:s 2 U base pair. In addition, even if an s 2 U is incorrectly incorporated, the addition of the next base is greatly hindered. This strong stalling effect would further increase the effective fidelity of nonenzymatic RNA copying with s 2 U. Our findings suggest that s 2 U may enhance the rate and extent of nonenzymatic copying with only a minimal cost in fidelity.
Organizational Affiliation:
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
