# DNA double-strand break chromatin alterations and genome integrity

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2022 · $334,749

## Abstract

Contact PD/PI: Greenberg, Roger A.
Summary
Evolutionary conserved DNA repair mechanisms cooperate throughout the cell cycle to faithfully maintain
genome integrity. However, a minimal understanding exists for how damaged chromatin directs the series of
events that dictate ensuing repair mechanism. This gap in knowledge is particularly relevant to a poorly
understood homology directed repair mechanism that becomes active to maintain telomere length in
approximately 15% of human cancers. Alternative lengthening of telomeres (ALT) occurs by noncanonical
homology directed DNA repair mechanism in cancers of mesenchymal origin. The recombination mechanisms
responsible for telomere maintenance represent a unique vulnerability in ALT reliant cancers.
We have developed experimental systems that enable quantitative, real-time visualization of each step in the
homology directed repair of damaged telomeres. Our published studies reveal that ALT is initiated by DNA
damage dependent homology directed repair synthesis that proceeds unidirectionally to the end of the
chromosome. We named this mechanism Break Induced Telomere Synthesis and showed that it is critical for
telomere lengthening in cells that utilize ALT. Here, we examine the question of how DNA damage responses
assemble on telomeric chromatin to direct long-tract homology directed repair telomere synthesis.
We hypothesize that Break Induced Telomere Synthesis occurs by assembling elements of several different
DNA repair mechanisms on telomeric chromatin to achieve homology directed repair synthesis. Our unpublished
results definitively support this premise, showing extensive PCNA- ubiquitination and recruitment of the 5’-3’
nuclease SNM1A and 5’-3’ helicase FANCJ at damaged telomeres to promote DNA repair synthesis and
telomere integrity. We will investigate the basis for their damage dependent association with telomeres and
functions in recombination dependent repair synthesis at telomeres using a multifaceted approach that allows
us to examine each step of the telomere damage response in cells and in vitro in highly purified systems that
assemble the break induced replisome on defined substrates. These fundamental studies are designed to
understand the critical elements of Break Induced Telomere Synthesis and how it allows telomere lengthening
for sustained proliferation in cells that rely on ALT.

## Key facts

- **NIH application ID:** 10464271
- **Project number:** 2R01GM101149-09A1
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Roger A Greenberg
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $334,749
- **Award type:** 2
- **Project period:** 2013-06-01 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10464271

## Citation

> US National Institutes of Health, RePORTER application 10464271, DNA double-strand break chromatin alterations and genome integrity (2R01GM101149-09A1). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10464271. Licensed CC0.

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