The G-quadruplex is one of the non-canonical structures formed by nucleic acids, which
can be formed by guanine-rich sequences. They became the focus of much research when
they were found in several oncogene promoter regions and also in the telomeres. Later
on, they were discovered in viruses as well. Various ligands have been developed in
order to stabilize DNA G-quadruplexes, which were believed to have an anti-cancer
or antiviral effect. We investigated three of these ligands, and whether they can
also affect the stability of the G-quadruplex-forming sequences of the RNA genome
of SARS-CoV-2. All three investigated oligonucleotides showed the G-quadruplex form.
We characterized their stability and measured their thermodynamic parameters using
the Förster resonance energy transfer method. The addition of the ligands caused an
increase in the unfolding temperature, but this effect was smaller compared to that
found earlier in the case of G-quadruplexes of the hepatitis B virus, which has a
DNA genome.
