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We have developed a colorimetric assay using gold nanoparticles (AuNPs) to assess the cooperative binding interactions between two transcription factors related to breast cancer development, i.e., estrogen receptor (ER) and specificity protein 1 (Sp1), with composite DNA elements. The composite DNA contains an estrogen response element (ERE) half-site and Sp1/GC-rich binding sites with a four nucleotides spacer. The assay design was conceptualised based on our previous findings that the size of protein-DNA complex is the determining factor to stabilize citrate anion-capped AuNPs from salt-induced aggregation, demonstrated using binary ER-ERE complexes. In this study, we have further proven that this concept is effective for detecting ternary protein-DNA complex of ER/Sp1-DNA, where the multiprotein-DNA complexes foster a better particle stabilization effect than the ER-DNA complex and/or protein (ER or Sp1) alone due predominantly to their distinct size differences. Based on the particle size and/or interparticle-distance dependent color and UV-vis spectroscopic properties of AuNPs, the formation of a ternary complex between ERα, Sp1, and the half-ERE/Sp1 composite element in the promoter A of the human PR gene can be detected. With this assay, we have also confirmed the cooperative binding of ERβ with Sp1, which has been less well characterized before in term of their cooperative effect in estrogen regulation. This homogenous 'mix-and-test' AuNPs assay is easy to use that can facilitate further understanding on how ER and Sp1 influence and activate gene transcription by forming cooperative binding compound to DNA, a key aspect in breast cancer biology.
Author(s): Tan YN, Lai AJ, Su X
Publication type: Article
Publication status: Published
Journal: Science of Advanced Materials
Year: 2014
Volume: 6
Issue: 7
Pages: 1460-1466
Online publication date: 01/07/2014
Acceptance date: 01/07/2014
ISSN (print): 1947-2935
ISSN (electronic): 1947-2943
Publisher: American Scientific Publishers
URL: https://doi.org/10.1166/sam.2014.1820
DOI: 10.1166/sam.2014.1820
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