title: Gold-nanoparticle-based assay for instantaneous detection of nuclear hormone receptor-response elements interactions.
abstract: Gold nanoparticles (AuNPs) are widely used as colorimetric probes for biosensing, relying on their unique particle size-dependent and/or interparticle distance-dependent extinction spectrum and solution color. Herein, we describe an AuNP-based colorimetric assay to detect binding interactions between nuclear hormone receptors and their corresponding DNA-binding elements, particularly the human estrogen receptors (ERalpha and ERbeta) and their cognate estrogen response elements (EREs). We found that the protein-DNA (ER-ERE) complexes can stabilize citrate anion-capped AuNPs against salt-induced aggregation to a larger extent than the protein (ER) or the DNA (ERE) alone, due to their unique molecular size and charge properties that provide a strong electrosteric protection. Moreover, our results show that the extent of stabilization is sequence-dependent and can distinguish a single base variation in the ERE associated with minor changes in protein-DNA binding affinity. With this assay, many important parameters of protein-DNA binding events (e.g., sequence selectivity, distinct DNA binding properties of protein subtypes, binding stoichiometry, and sequence-independent transient binding) can be determined instantly without using labels, tedious sample preparations, and sophisticated instrumentation. These benefits, in particular the high-throughput potential, could enable this assay to become the assay of choice to complement conventional techniques for large scale characterization of protein-DNA interactions, a key aspect in biological research.
authors.affiliation: Institute of Material Research and Engineering, ASTAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602.
authors.forename: Yen Nee
authors.initials: YN
authors.lastname: Tan
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Su
authors.forename: Edison T
authors.initials: ET
authors.lastname: Liu
authors.forename: Jane S
authors.initials: JS
authors.lastname: Thomsen
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D047628:Estrogen Receptor alpha / Q000737:chemistry* / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000737:chemistry* / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D011485:Protein Binding; D020218:Response Elements; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D006046:Gold; D004247:DNA