Mutagenesis Reveals an Unusual Combination of Guanines in RNA G-Quadruplex Formation

[Image: see text] The classic G-quadruplex motif consists of a continuous array of 3–4 guanine residues with an intermittent loop size of 1–7 nucleotides (G(3–4)N(1–7)G(3–4)N(1–7)G(3–4)N(1–7)G(3–4)). An RNA G-quadruplex is able to attain only one parallel G-quadruplex topology owing to steric constraints. Investigating the possibilities of the formation of RNA G-quadruplexes with a stretch of sequences deviating from this classic motif will add to the overall conformations of RNA G-quadruplexes, bestowing diversity to this structure. Here, we report unusual combinations of guanine residues involved in RNA G-quadruplex formation in the 5′ untranslated region (UTR) of the von Willebrand factor (VWF) mRNA using the mutagenesis approach. Different permutations and combinations of guanine residues form G-quadruplexes. Upon investigation, G-quadruplexes in 5′ UTR of VWF mRNA are shown to exhibit an inhibitory function.