PrP octa-repeat mRNA is largely double-stranded. (a) SHAPE analysis of wt and ΔG4 PrP octa-repeat mRNA in 100 mM LiCl or KCl without (−) or with SHAPE reagent NMIA (+). The mRNA in the negative control (−) was incubated with DMSO. Red boxes indicate regions of putative G-quadruplex motifs. (b) RNA secondary structure representations from RNAfold. Single-stranded nucleotides from (a) are color coded in green. G’s crucial for a G-quadruplex formation are designated in red.