Ultrasensitive Detection of Transcription Factors Using Transcription-Mediated
Isothermally Exponential Amplification-Induced Chemiluminescence
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Abstract
Transcription factors (TFs) are important
cellular components that
modulate gene expression, and the malregulation of transcription will
lead to a variety of diseases such as cancer and developmental syndromes.
However, the conventional methods for transcription factor assay are
generally cumbersome and costly with low sensitivity. Here, we develop
a label-free strategy for ultrasensitive detection of transcription
factors using a cascade signal amplification of RNA transcription,
dual isothermally exponential amplification reaction (EXPAR), and
G-quadruplex DNAzyme-driven chemiluminescence. Briefly, the specific
binding of TF with the detecting probe prevents the cleavage of the
detecting probe by exonuclease and subsequently facilitates the conversion
of TF signal to abundant RNA triggers in the presence of T7 RNA polymerase.
The obtained RNA triggers can initiate the strand displacement amplification
to yield abundant DNAzymes and DNA triggers, and the released DNA
triggers can further initiate the next rounds of EXPAR reaction. The
synergistic operation of dual EXPAR reaction can produce large amounts
of DNAzymes, which subsequently catalyze the oxidation of luminol
by H<sub>2</sub>O<sub>2</sub> to yield an enhanced chemiluminescence
signal with the assistance of cofactor hemin. Conversely, in the absence
of target TF, the naked detecting probes will be completely digested
by exonucleases, leading to neither the transcription-mediated EXPAR
nor the DNAzyme-driven chemiluminescence signal. This method has a
low detection limit of as low as 6.03 × 10<sup>–15</sup> M and a broad dynamic range from 10 fM to 1 nM and can even measure
the NF-κB p50 of crude cell nuclear extracts. Moreover, this
method can be used to measure a variety of DNA-binding proteins by
simply substituting the target-specific binding sequence in the detecting
probes