Bio-Layer Interferometry (BLI): a useful tool to investigate the interactions of i-motif DNA with small molecules and proteins
Résumé
i-Motifs of DNA (hereafter, i-DNA), known in vitro for nearly three decades, are unusual, four-stranded structures, in which cytosines are intercalated via a stack of hemi-protonated C–C base pairs (CH+:C) (Fig. 1A, B). Some of these structures have been well characterized in vitro and, because i-DNA may mirror other four-stranded G-rich structures (G-quadruplexes) present in gene promoters or at telomeres, their biological relevance is being investigated. Relatively few molecules were reported to interact with i-DNA. The main issues in this regard are the strong pH-dependency, flexibility, polymorphism and complex folding behavior of i-DNA, which introduce potential bias into screening methods. In particular, low-pH conditions used to induce the formation of i-DNA lead to the protonation of many ligands, which can strongly increase their non-specific nucleic acid binding. This latter point is particularly critical because the use of small molecules to study the biological functions of such structures is essential. In this context, we are developed a method using the Bio-Layer Interferometry (BLI) to screen and to study the interactions between the i-motif and already reported ligands (TMPyP4, mitoxantrone, IMC-48, berberine, etc) at physiologically relevant pH. We demonstrated that none of the reported ligands were shown to discriminate between folded and unfolded i-motif structures.[1,2]
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