Abstract:
:Human telomeres terminate with a single-stranded 3' G overhang, which can be recognized as a DNA damage site by replication protein A (RPA). The protection of telomeres (POT1)/POT1-interacting protein 1 (TPP1) heterodimer binds specifically to single-stranded telomeric DNA (ssTEL) and protects G overhangs against RPA binding. The G overhang spontaneously folds into various G-quadruplex (GQ) conformations. It remains unclear whether GQ formation affects the ability of POT1/TPP1 to compete against RPA to access ssTEL. Using single-molecule Förster resonance energy transfer, we showed that POT1 stably loads to a minimal DNA sequence adjacent to a folded GQ. At 150 mM K(+), POT1 loading unfolds the antiparallel GQ, as the parallel conformation remains folded. POT1/TPP1 loading blocks RPA's access to both folded and unfolded telomeres by two orders of magnitude. This protection is not observed at 150 mM Na(+), in which ssTEL forms only a less-stable antiparallel GQ. These results suggest that GQ formation of telomeric overhangs may contribute to suppression of DNA damage signals.
journal_name
Proc Natl Acad Sci U S Aauthors
Ray S,Bandaria JN,Qureshi MH,Yildiz A,Balci Hdoi
10.1073/pnas.1321436111subject
Has Abstractpub_date
2014-02-25 00:00:00pages
2990-5issue
8eissn
0027-8424issn
1091-6490pii
1321436111journal_volume
111pub_type
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