We aim to understand how telomeres solve the end-protection problem. Specifically, this proposal describes experiments to gain insight Into the mechanism by which the telomeric protein complex, shelterin, represses the two main DNA repair reactions, NHEJ and HDR at chromosome ends.
Our aim I s to delineate the nature of the repair reactions at telomeres, their outcomes, what factors are involved, how these pathways are regulated, and how telomeres prevent inappropriate processing by repair pathways. Telomere dysfunction is thought to be main source of genome instability in human cancer, has been implicated in aging, and is at the core of several human diseases that are caused by loss of telomeric DNA (e.g. dyskeratosis congenita, anaplastic anemia). When telomeres become dysfunctional, inappropriate repair at chromosome ends is a major determinant of the pathological outcomes. Detailed understanding of the repair pathways at dysfunctional telomeres is therefore expected to impact the treatment and prevention human disease. We will use genetic, molecular genetic, and cell biological techniques to address the mechanism by which telomeres repress inappropriate repair and define the pathological repair reactions at dysfunctional telomeres. The experimental approaches will involve the tools for studying mammalian telomeres that we have developed under the auspices of this grant over the past 16 years. Specifically, we will use mouse embryo fibroblast cell lines from which shelterin components can be deleted with the Cre recombinase. By changing the genetic background of these cells, using compound genotypes, we can monitor the repair at dysfunctional telomere, delineate the genes involved In the reactions, and define how shelterin represses these reactions at functional telomeres.

Public Health Relevance

A growing number of human disease states are now understood to involve a failure in the function of telomeres, the protective elements at the ends of human chromosomes. This project is aimed at gaining Insight into how telomeres protect chromosome ends and what happens when this protection is lost. The work is expected to be significant in the context of cancer, aging, and telomere-related diseases such as dyskeratosis congetica.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Method to Extend Research in Time (MERIT) Award (R37)
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Study Section
Special Emphasis Panel (NSS)
Program Officer
Carter, Anthony D
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Rockefeller University
Anatomy/Cell Biology
Other Domestic Higher Education
New York
United States
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Kibe, Tatsuya; Zimmermann, Michal; de Lange, Titia (2016) TPP1 Blocks an ATR-Mediated Resection Mechanism at Telomeres. Mol Cell 61:236-46
Frescas, David; de Lange, Titia (2014) TRF2-tethered TIN2 can mediate telomere protection by TPP1/POT1. Mol Cell Biol 34:1349-62
Kabir, Shaheen; Hockemeyer, Dirk; de Lange, Titia (2014) TALEN gene knockouts reveal no requirement for the conserved human shelterin protein Rap1 in telomere protection and length regulation. Cell Rep 9:1273-80
Zimmermann, Michal; Kibe, Tatsuya; Kabir, Shaheen et al. (2014) TRF1 negotiates TTAGGG repeat-associated replication problems by recruiting the BLM helicase and the TPP1/POT1 repressor of ATR signaling. Genes Dev 28:2477-91
Frescas, David; de Lange, Titia (2014) A TIN2 dyskeratosis congenita mutation causes telomerase-independent telomere shortening in mice. Genes Dev 28:153-66
Frescas, David; de Lange, Titia (2014) Binding of TPP1 protein to TIN2 protein is required for POT1a,b protein-mediated telomere protection. J Biol Chem 289:24180-7
Zimmermann, Michal; de Lange, Titia (2014) 53BP1: pro choice in DNA repair. Trends Cell Biol 24:108-17
Doksani, Ylli; Wu, John Y; de Lange, Titia et al. (2013) Super-resolution fluorescence imaging of telomeres reveals TRF2-dependent T-loop formation. Cell 155:345-356
Zimmermann, Michal; Lottersberger, Francisca; Buonomo, Sara B et al. (2013) 53BP1 regulates DSB repair using Rif1 to control 5' end resection. Science 339:700-4
Ahmed, Emad A; Sfeir, Agnel; Takai, Hiroyuki et al. (2013) Ku70 and non-homologous end joining protect testicular cells from DNA damage. J Cell Sci 126:3095-104

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