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Nature. 2016 Nov 3;539(7627):54-58. doi: 10.1038/nature20099. Epub 2016 Oct 19.

Break-induced telomere synthesis underlies alternative telomere maintenance.

Author information

1
Department of Cancer Biology, Abramson Family Cancer Research Institute, Basser Research Center for BRCA, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
2
Department of Pathology, Abramson Family Cancer Research Institute, Basser Research Center for BRCA, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.

Abstract

Homology-directed DNA repair is essential for genome maintenance through templated DNA synthesis. Alternative lengthening of telomeres (ALT) necessitates homology-directed DNA repair to maintain telomeres in about 10-15% of human cancers. How DNA damage induces assembly and execution of a DNA replication complex (break-induced replisome) at telomeres or elsewhere in the mammalian genome is poorly understood. Here we define break-induced telomere synthesis and demonstrate that it utilizes a specialized replisome, which underlies ALT telomere maintenance. DNA double-strand breaks enact nascent telomere synthesis by long-tract unidirectional replication. Proliferating cell nuclear antigen (PCNA) loading by replication factor C (RFC) acts as the initial sensor of telomere damage to establish predominance of DNA polymerase δ (Pol δ) through its POLD3 subunit. Break-induced telomere synthesis requires the RFC-PCNA-Pol δ axis, but is independent of other canonical replisome components, ATM and ATR, or the homologous recombination protein Rad51. Thus, the inception of telomere damage recognition by the break-induced replisome orchestrates homology-directed telomere maintenance.

PMID:
27760120
PMCID:
PMC5384111
DOI:
10.1038/nature20099
[Indexed for MEDLINE]
Free PMC Article

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