Figure 3.

Principle of the NC inhibitor screening assay. This assay is based on the use of a HIV-1 TAR DNA (cTAR) sequence labeled at its 5' and 3' ends, by a fluorophore (D) and a quencher (Q), respectively. In the absence of NC, Q is close to D, leading to a small residual fluorescence of D. Due to its nucleic acid destabilizing properties, NC melts the cTAR structure up to the middle of the stem, leading Q to move away from D, thus causing a large fluorescence increase. A positive hit is detected through the restoration of the initial low fluorescence level.