Fig. 1

DNA–PK facilitates G–overhang production and telomeric capping. a DNA–PKcs phosphorylation at the Thr2609 cluster promotes dissociation of the DNA–PK complex at newly replicated blunt–ended leading telomeres. This enables G–overhang production through i) telomerase–mediated telomere extension, or ii) Snm1b/Apollo exonuclease–mediated end–resection. b DNA–PK–dependent hnRNP–A1 phosphorylation improves hnRNP–A1’s ability to displace RPA and favor POT1 loading at single–stranded telomeric DNA. This supports T–loop formation. TERRA negatively regulates T–loop formation by trapping hnRNP–A1 away from telomere overhangs. The RPA–to–POT1 displacement also prevents ATR signaling activation at single–stranded telomeric DNA