FIGURE 2: Recombination activities mediate a variety of telomere processes.

(A) Strand invasion of a telomere into interstitial telomere sequence (green) located on the same (not shown) or different chromosome can lead to genome rearrangement. Depicted here, a segment of the invaded chromosome (black) is duplicated.

(B) Replication of a telomere leads to two sister telomeres. The one synthesized by the lagging strand replication machinery will have an RNA primer (purple zigzag line) at its 5’ terminus, while the other will have a blunt end (circled in green). Removal of the RNA primer on the former will lead to the regeneration of a 3’ overhang while the latter must be 5’ end resected.

(C) A model for a T-SCE event. The blue and red lines depict sister telomeres.

(D) A t-loop forms via the strand invasion of the telomeric 3’ single-stranded overhang into double-stranded telomeric DNA of the same telomere. Excision of a t-loop yields a truncated telomere. Rolling circle DNA replication can be used to extend a telomere in a t-loop configuration, or a telomere (red) that has strand invaded a DNA circle containing telomeric repeats. Dashed lines indicate newly synthesize DNA.