Article | Published:

TRF2 binds branched DNA to safeguard telomere integrity

Nature Structural & Molecular Biology volume 24, pages 734742 (2017) | Download Citation

Abstract

Although t-loops protect telomeres, they are at risk of cleavage by Holliday junction (HJ) resolvases if branch migration converts the three-way t-loop junction into four-way HJs. T-loop cleavage is repressed by the TRF2 basic domain, which binds three- and four-way junctions and protects HJs in vitro. By replacing the basic domain with bacterial-protein domains binding three- and four-way junctions, we demonstrated the in vivo relevance of branched-DNA binding. Branched-DNA binding also repressed PARP1, presumably by masking the PARP1 site in the t-loop junction. Although PARP1 recruits HJ resolvases and promotes t-loop cleavage, PARP1 activation alone did not result in t-loop cleavage, thus suggesting that the basic domain also prevents formation of HJs. Concordantly, removal of HJs by BLM helicase mitigated t-loop cleavage in response to loss of the basic domain. We propose that TRF2 masks and stabilizes the t-loop three-way junction, thereby protecting telomeres from detrimental deletions and PARP1 activation.

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Acknowledgements

We thank D. White for expert mouse husbandry and the members of the laboratory of T.d.L. for sharing cell lines, for discussion and for comments on the manuscript. I.S. was supported by funds from a Women & Science Irene Diamond Fellowship in Breast Cancer Research at the Rockefeller University and by Mobility fellowships from the Swiss National Science foundation (Early Mobility fellowships PBFRP3-137230 and PBFRP3_142824, and Advanced Mobility fellowship P300PA_161006). L.T. was supported by an Anderson Center for Cancer Research Graduate Fellowship (contract FA9550-11-C-0028, awarded by the Department of Defense, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship 32 CFR 168a). This work was supported by grants from the NIH (AG016642) to T.d.L. and (GM104962) to D.J.P., and by a Memorial Sloan-Kettering Cancer Center NIH Core Grant (P30 CA008748). T.d.L. is supported as an American Cancer Society Rose Zarucki Trust Research Professor. SPR experiments were performed at the RU High-Throughput and Spectroscopy Resource Center with expert assistance from A. Alcaino. OMX-SI imaging experiments were supported by a grant (S10RR031855) from the National Center For Research Resources to the Bio-Imaging Center at RU. The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the National Center For Research Resources or the National Institutes of Health. We thank G. Hannon (Cancer Research UK Cambridge Institute) for reagents.

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Affiliations

  1. Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York, USA.

    • Isabelle Schmutz
    • , Leonid Timashev
    •  & Titia de Lange
  2. Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.

    • Wei Xie
    •  & Dinshaw J Patel

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Contributions

I.S. and T.d.L. designed the experiments and wrote the manuscript. I.S. performed all in vivo experiments, except for the t-loop assays, which were performed by L.T. W.X. and D.J.P. performed the in vitro binding studies.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Titia de Lange.

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https://doi.org/10.1038/nsmb.3451

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