FIGURE 1.

Telomere structure and sensitivity to oxidative damage. Telomeres are nucleoprotein structures composed of repetitive TTAGGG sequence and associated telomere-specific proteins, named shelterin. Telomeric DNA terminates in a 3′ single stranded overhang, which invades the double stranded telomeric DNA to form a lariat-like t-loop. The formation of the t-loop is mediated by the protective shelterin complex, which consists of TRF1, TRF2, RAP1, TIN2, TPP1 and POT1. The highly repetitive G-rich telomeric repeats are preferred sites for production 8-oxoG (indicated by the lightning bolts), therefore, telomeric DNA is remarkably susceptible to oxidative stress.