Figure 1.

Mechanism of telomere repeat elongation by DNA nanocircles. (A) Circular, single-stranded DNA composed of the C-rich human telomeric sequence binds to the 3′ end of the G-rich complement, corresponding to the sequence at the end of a telomere. When incubated with DNA polymerases, the nanocircles act as templates in a rolling circle replication, resulting in elongation of the G-rich telomeric sequence by hundreds or thousands of nucleotides. (B) DNA nanocircles consisting of 6 to 10 repeats of the hexameric sequence (resulting in circle sizes of 36, 42, 48, 54 and 60 nt) were characterized. Sequences of circles 36, 48 and 60 are shown.