Fig. 6.

Effect of Nuc-1,2,3,4-RGG, Nuc-3,4-RGG, and Nuc-RGG on c-MYC promoter activity as determined by in vitro transcription. (A) Diagram of the pMYC-Luc reporter construct containing the c-MYC NHE III₁ region that can assemble into a G-quadruplex structure. (B) Effect of Nuc-1,2,3,4-RGG (lanes 1–4), Nuc-3,4-RGG (lanes 5–8), and Nuc-RGG (lanes 9–12) on c-MYC promoter activity as determined by in vitro transcription assay. Reactions contained 1 μg of pMYC-WT (Del-4) plasmid and the indicated concentrations of nucleolin per reaction. Plasmid and the recombinant protein were incubated for 1 h at 4 °C prior to the addition of HeLa nuclear extract. In vitro transcription reactions were carried out at 42 °C for exactly 60 min, after which all reactions were stopped by the addition of stop buffer, as described in Materials and Methods. The multiple bands correspond to the transcripts from the several transcription initiation sites found in the luciferase coding region (44).