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  • Title: Direct evidence for a G-quadruplex in a promoter region and its targeting with a small molecule to repress c-MYC transcription.
    Author: Siddiqui-Jain A, Grand CL, Bearss DJ, Hurley LH.
    Journal: Proc Natl Acad Sci U S A; 2002 Sep 03; 99(18):11593-8. PubMed ID: 12195017.
    Abstract:
    The nuclease hypersensitivity element III(1) upstream of the P1 promoter of c-MYC controls 85-90% of the transcriptional activation of this gene. We have demonstrated that the purine-rich strand of the DNA in this region can form two different intramolecular G-quadruplex structures, only one of which seems to be biologically relevant. This biologically relevant structure is the kinetically favored chair-form G-quadruplex, which is destabilized when mutated with a single G --> A transition, resulting in a 3-fold increase in basal transcriptional activity of the c-MYC promoter. The cationic porphyrin TMPyP4, which has been shown to stabilize this G-quadruplex structure, is able to suppress further c-MYC transcriptional activation. These results provide compelling evidence that a specific G-quadruplex structure formed in the c-MYC promoter region functions as a transcriptional repressor element. Furthermore, we establish the principle that c-MYC transcription can be controlled by ligand-mediated G-quadruplex stabilization.
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