G-quadruplex and 8-oxo-7,8-dihydroguanine across the genome: methodologies and crosstalk

G-quadruplex (G4) is a non-canonical DNA second structure formed on specific G-rich sequences which are enriched in transcriptional regulatory regions and telomeres. This structure is involved in multiple cellular processes including transcription regulation and genome integrity. On the other hand, G-rich regions are hotspots of oxidative damage, since G has the lowest redox potential among the four nucleobases, and the 5’G of a G stretch has an even lower ionization potential. Evidence emerged recently that the most common oxidative damage, 8-oxo-7,8-dihydroguanine (OG), plays an epigenetic-like role to regulate transcription. Therefore, G4 and OG may co-localize at G-rich regions and interact with each other to regulate transcription. In this review, we summarize recent advantages about genome-wide mapping of G4 and OG, and discuss their crosstalk at genomic level.