Assessing chromatin condensation for epigenetics with a DNA-targeting sensor by FRET and FLIM techniques

Here we propose a fluorescent sensor, Chroma-V, consisted of a Hoechst ligand (Hoe) to target chromatin DNA and a BODIPY rotor (BDP) to sense the local viscosity that reflects chromatin condensation state. Within Chroma-V, efficient FRET process from Hoe to BDP facilitated a single-excitation ratiometric imaging of nucleus DNA under fluorescence confocal microscope, which utilized the ratio of two channels to enable an intuitive visualization of chromatin condensation state. And fluorescence lifetime imaging (FLIM) based on fluorescent signal from BDP proved to be a more accurate method to quantify the changes of chromatin condensation state under different epigenetic states, including histone acetylation regulated by deacetylase inhibitors, cell apoptosis induced by DNA-bining drugs, and the epithelial-mesenchymal transition of HUVEC cells induced by TGF-β.