Effects of natural lesions formed in human telomere G4 tetrads and loops are reviewed.
8-oxoG and AP sites formed in G-tetrads significantly destabilize the quadruplex.
G4 destabilization is more dependent on lesion position than on its type.
8-oxoA, 5-hmU or AP site in loops affect G4 stability less but can change its folding.
The effect of loop lesions depends more on the type than on the position in the loop.