Working on transcription factors requires studying interactions between protein and DNA. After identification of putative binding-sequences and motifs, Electrophoretic Mobility Shift Assay (EMSA) experiment is classically used to determine specific interactions of proteins and nucleic acids. This lengthy process is rather heavy-handed because of radioisotopically labeled DNA and autoradiographic visualization that are required for the experiments.
Liquid luminescent DNA precipitation assay provides rapid, reliable and quantitative results concerning protein-DNA interactions. This protein-DNA binding assay is based on solution hybridization between Digoxigenin-labeled (DIG) DNA and glutathione S-transferase (GST)-fused DNA binding protein bound to Glutathione Sepharose 4B beads (Figure 1), without electrophoresis (Toshiharu
et al., 2008).
Digoxigenin is a steroid found in plants. It is increasingly used as a label for nonradioactive detection of nucleic acids and proteins.
Figure 1. Representation of liquid chemiluminescent DNA pull-down assay. A Glutathione
S-transferase (GST)-fused NLRP3 (GST-NLRP3) bound to Glutathione Sepharose 4B beads is incubated with a DIG-labeled double-stranded DNA fragment containing putative NLRP3 Binding Site (NBS) in protein-DNA binding buffer. After extensive washing, protein-DNA binding on beads is detected using anti-DIG antibody conjugated to alkaline phosphatase, which is measured by a chemiluminescent reaction using a luminometer Disodium 3-(4-methoxyspiro {1,2-dioxetane-3,2′-(5′-chloro) tricyclo [3.3.1.1
3, 7] decan}-4-yl) phenyl phosphate(CSPD).
Here, we described how we used this technique to demonstrate the interaction between NLRP3 protein and its DNA binding site (Bruchard
et al., 2015).