A newly identified G-quadruplex as a potential target regulating Bcl-2 expression

• A new G-quadruplex located in the Bcl-2 P1 promoter is researched.
• The G-quadruplex is a hybrid-type intramolecular structure.
• PD can induce the G-quadruplex to show antiparallel feature.
• PD down-regulates Bcl-2 expression by interacting with the G-quadruplex.
• The G-quadruplex structure is related with Bcl-2 expression.

BackgroundA new G-quadruplex structure located in the B-cell CLL/lymphoma 2 (Bcl-2) P1 promoter and its physiological function related to Bcl-2 transcription have been studied to find a potential anticancer therapeutic target.MethodsAbsorption, polyacrylamide gel electrophoresis, fluorescence, circular dichroism, and nuclear magnetic resonance spectra have been employed to determine G-quadruplex structure and the interaction between G-quadruplex and phenanthrolin-dicarboxylate. Real time polymerase chain reaction and luciferase assay were done to assess the physiological function of the G-quadruplex structure.ResultsThe UV-melting and polyacrylamide gel electrophoresis studies show that the p32 DNA sequence forms an intramolecular G-quadruplex structure. Circular dichroism and nuclear magnetic resonance spectra indicate that the G-quadruplex is a hybrid-type structure with four G-tetrads. Fluorescence spectra show that a phenanthroline derivative has a higher binding affinity for p32 G-quadruplex than duplex. Further circular dichroism and nuclear magnetic resonance studies indicate that the phenanthroline derivative can regulate p32 G-quadruplex conformation. Real time polymerase chain reaction and luciferase assays show that the phenanthroline derivative has down-modulated Bcl-2 transcription activity in a concentration-dependent manner. However, no such effect was observed when p32 G-quadruplex was denatured through base mutation.ConclusionThe newly identified G-quadruplex located in the P1 promoter of Bcl-2 oncogene is intimately related with Bcl-2 transcription activity, which may be a promising anticancer therapeutic target.General significanceThe newly identified G-quadruplex in the Bcl-2 P1 promoter may be a novel anticancer therapeutic target.