Fluorescence sensing of protein-DNA interactions using conjugated polymers and graphene oxide

Protein-DNA binding, particularly transcription factor-DNA binding, is one of the main molecular interactions involved in gene regulation. These interactions are sequence-specific, play a key role in many fundamental biological processes, and are deregulated in the pathogenesis of several diseases. In this study, a robust analytical bioassay to characterize protein-DNA binding was built by combining the optical properties of water soluble conjugated polymers, and graphene oxide's superquenching capabilities. Cationic conjugated polymers bind strongly to double stranded DNA through electrostatic interactions, and provide fluorescent signals to track the DNA without any chemical modification. In addition, the labeled DNA retains its protein binding ability. An important oncogenic transcription factor (i.e. estrogen receptor α) was used to demonstrate the concept, and two collaborative factors involved in the estrogen gene transcription (i.e. forkhead box A1 and activating enhancer binding protein 2 gamma) were employed as controls. This method overcame the main limitations of previous nanomaterial-based bioassays, while keeping the sensitivity and precision of the gold standard techniques. These benefits, combined with the high versatility and low-costs, could lead this bioassay to be used in several fundamental biomedical research lines, such as large scale protein-DNA binding studies and drug discovery.