Demonstration of the GC-Rich Common Arm in Yeast Ribosomal 5.8S RNA via 500-MHz Proton Nuclear Magnetic Resonance and Overhauser Enhancements

In this paper we report the first ¹H NMR study of the base-paired secondary structure of yeast 5.8S RNA. On the basis of a combination of homonuclear Overhauser enhancements and temperature dependence of the proton 500-MHz NMR spectrum, we are able to identify and assign eight of the nine base pairs in the most thermally stable helical arm: G₁₁₆*C₁₃₇-C₁₁₇*G₁₃₆-C₁₁₈*G₁₃₅-C_ll9*G₁₃₄-C₁₂₀-G₁₃₃-U₁₂₁*G₁₃₂-U₁₂₂*A₁₃₁-G_123*C₁₃₀. This arm contains an unusually temperature-stable (to 71 °C) segment of four consecutive G*C base pairs. This work constitutes the most direct evidence to date for the existence and base-pair sequence of the GC-rich helix, which is common to most currently popular secondary structural models for eukaryotic 5.8S ribosomal RNA.