Schematic of mechanisms of action for the Pu27-HS to inhibit c-MYC expression in U937.

The silencer NHEIII₁ in the c-MYC promoter is in equilibrium between the OFF position when it forms G-quadruplex structure or ON when in duplex resulting in mRNA and protein production. In the presence of Pu27-HS (blue) the protein can be inhibited after several possibilities of binding: 1) Pu27-HS bind to the C-rich strand and stabilize the G-quadruplex and inhibit transcription. 2) Pu27-HS bind to C-rich duplex and induce error in the mRNA and inhibit translation. 3) Pu27-HS bind to the C-rich complementary sequence in the 5’UTRmRNA and inhibit translation. 4) Pu27-HS bind to the G-rich, stabilize the G-quadruplex and inhibit transcription.