Profusion of G-quadruplexes on both subunits of metazoan ribosomes
(a) The expanded secondary structure of the G-quadruplex regions on es3 or es12 of the human SSU rRNA. Schematic diagram of a single G-quartet, a 3 x 4 G-quadruplex (with tracts of at least three guanine residues), and a 2 x 4 G-quadruplex (with tracts of at least two guanine residues). (b) CD spectra of SSU G-quadruplex regions GQes3 and GQes12 and control RNAs mutes3 and mutes12. (c) Changes in CD amplitude at 260 nm as a function of temperature for GQes3 and GQes12. (d) ThT fluorescence in solutions of GQes3, GQes12, mutes3 or mutes12 annealed in the presence of potassium ions. (e) ThT/PDS competition assay. After annealing, the rRNA oligomers were incubated with increasing concentrations of PDS and then fluorescence was recorded at 490 nm. (f) ThT fluorescence of LSU oligomers GQES7-a and GQES7-b and SSU oligomers GQes3 and GQes12. (g) Sedimentation velocities of GQes3, GQes12, mutes3 or mutes12. Data are shown as c(s) plots that show the distribution of sedimentation coefficients obtained by analysis using the program SEDFIT . The statistical significance relative to GQES7-a-ThT fluorescence is indicated by asterisks using an ordinary one-way ANOVA with Dunnett’s post-hoc test. **** P < 0.0001.