The helix 69 (H69) region of the large subunit (28S) rRNA of Homo sapiens contains five pseudouridine (C) residues out of 19 total nucleotides (26%), three of which are universally or highly conserved. In this study, the effects of this abundant modified nucleotide on the structure and stability of H69 were compared with those of uridine. The role of a loop nucleotide substitution from A in bacteria (position 1918 in Escherichia coli 23S rRNA) to G in eukaryotes (position in 3734 in H. sapiens) was also examined. The thermodynamic parameters were obtained through UV melting studies, and differences in the modified and unmodified RNA structures were examined by 1 H NMR and circular dichroism spectroscopy. In addition, a [1,3-15 N]C phosphoramidite was used to generate H69 analogs with site-specific 15 N labels. By using this approach, different C residues can be clearly distinguished from one another in 1 H NMR experiments. The effects of pseudouridine on H. sapiens H69 are consistent with previous studies on tRNA, rRNA, and snRNA models in which the nucleotide offers stabilization of duplex regions through CN1H-mediated hydrogen bonds. The overall secondary structure and base-pairing patterns of human H69 are similar to the bacterial RNA, consistent with the idea that ribosome structure and function are highly conserved. Nonetheless, pseudouridine-containing RNAs have subtle differences in their structures and stabilities compared to the corresponding uridine-containing analogs, suggesting possible roles for C such as maintaining translation fidelity.

No abstract

No abstract

No abstract

Nucleic acidsNucleic acids U 0700 Synthesis of Helix 69 of Escherichia coli 23S rRNA Containing Its Natural Modified Nucleosides, m 3 Ψ and Ψ. -(CHUI, H. M.-P.; DESAULNIERS, J.-P.; SCARINGE, S. A.; CHOW*, C. S.; J. Org. Chem. 67 (2002) 25, 8847-8854; Dep. Chem., Wayne State Univ., Detroit, MI 48202, USA; Eng.) -Klein 15-205