Figure 1.

Schematic illustration of the structure of telomeres. The telomere repeats are coated by shelterin, a complex of six proteins that bind to DNA either directly (TRF1, TRF2, and POT1) or indirectly (TIN2, RAP1, and TPP1). The shelterin induces the formation of a T-loop by invasion of the single-stranded overhang into double-stranded telomeric DNA. TRF: telomeric repeat-binding factor; POT1: protection of telomeres 1; TIN2: TRF1-interacting nuclear factor 2; RAP1: repressor-activator protein 1.