Fig. 4

Characterization of G4 structures present in HIV-1 LTR. A HIV-1 promoter sequence and previously characterized G4s (LTR I to IV [50, 53, 55]) present along this sequence. B Oligonucleotides covering HIV-1 and c-myc G4s used in this study. Name, sequence and G4 folding scores (G4hunter and QGRS) of oligonucleotides covering PQSs present in HIV-1 LTR (LTR I, LTR II and LTR III, LTR III Short and LTR IV Short), mutated PQS LTR III (Mut1 to Mut6) and a PQS present in c-myc promoter. These oligonucleotides were used in the biophysical and structural studies presented below. C–F Biophysical and structural characterization of WT and mutated HIV-1 LTR III oligonucleotides G4 sequences. C Isothermal difference spectra with and without 100 mM KCl. D Thioflavin (ThT) fluorescence assay. E Circular dichroism (CD) spectra measured in 100 mM KCl. Oligonucleotides used in these studies are described in Additional file 5: Table S1