AKT1 is positively regulated by G-quadruplexes in its promoter and 3'-UTR

AKT1 plays a key role in cell growth and survival, and its activation in cancers is mediated by different mechanisms. In this study, we investigated the potential of G-quadruplex (G4) formation by multiple consecutive G-tracts in the AKT1 promoter and its 3'-UTR. In circular dichroism analyses, synthetic oligonucleotides based on these G-tract regions showed molar ellipticity peaks at specific wavelengths of G4 structures. We verified G4 forming potential of these oligonucleotides using dimethyl sulfate footprinting, gel-shift and immunostaining assays. In reporter assays, mutations of the G-tracts in either the promoter or the 3'-UTR of AKT1 reduced expression mediated by these G-rich regions, suggesting positive regulation of AKT1 gene expression by these G4 structures. Furthermore, SP1 bound to its consensus sites regardless of the presence of G4 motifs in the AKT1 promoter, and both the G4 motifs and SP1 binding sites were needed to reach the strongest promoter strength.