# Roles of Telomeric Oxidative DNA Lesions in Telomere Length Regulation

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2024 · $441,523

## Abstract

The goals of this project are to determine how oxidative DNA damage regulates the homology-directed repair
(HDR) pathways that enable telomere maintenance by the alternative lengthening of telomeres (ALT)
mechanisms. Dysfunctional redox regulation is common among cancers and elevates reactive oxygen
species, which generate DNA lesions. Telomeres are highly susceptible to oxidative damage but are essential
for genome stability and sustained cell proliferation. Dysfunctional telomeres arrest cell division or drive excess
chromosomal instability in pre-malignant cells that can cause cell death. To survive and achieve unlimited
proliferation, cancer cells elongate and stabilize telomeres by activating telomerase or ALT. Although less
common, ALT-driven cancers are highly aggressive with poor prognosis. Telomeric single-stranded overhangs
are substrates for both telomerase and ALT-mediated telomere elongation but can self-fold into stable
secondary structures. Previously, we found that low 8oxoG levels stimulate telomerase by altering structure
and overhang accessibility, but that excess 8oxoG damage impairs telomere replication. In this project we will
test the hypothesis that 8oxoG formation and processing at telomeres modulate ALT by promoting replication
fork stalling and altering telomere structures. Using an innovative targeting tool to selectively induce 8oxoG at
telomeres, we obtained preliminary data that 8oxoG increases numerous ALT hallmarks including C-circles,
ALT-associated PML bodies, and telomeric sister chromatid exchanges and mitotic DNA synthesis. Aim 1 will
determine how oxidative base damage modulates ALT and HDR activity in human cancer cell lines, proficient
and deficient for repair. We will induce telomere specific damage or general oxidative stress in ALT and
telomerase positive cells, and will measure cell survival, ALT phenotypes, and various telomere parameters.
ALT requires RAD51 or RAD52 and is regulated by a variety of telomeric structures. Aim 2 will examine how
oxidative lesions modulate telomeric RNA (TERRA) invasion and R-loop formation into telomeres. Using a
single molecule fluorescence resonance energy transfer detection system, we discovered 8oxoG in telomeric
duplex facilitates TERRA association. We will use complementary cellular studies to examine TERRA
recruitment to telomeres after oxidative damage. Aim 3 will examine how oxidative damage in the telomere
overhang modulates D-loop formation by RAD51-mediated strand invasion, or RAD52-mediated strand
annealing, by using complementary single molecule and biochemical experiments. We will conduct cellular
studies to determine how RAD51 or RAD52 deficiency influence 8oxoG-induced ALT phenotypes. This project
will fill a significant void in our understanding of how general oxidative stress and 8oxoG, in particular, alter
telomere restoration by homology-directed repair and ALT. Ultimately, this knowledge will be highly valuable
for developing new strategies that 1)...

## Key facts

- **NIH application ID:** 10829460
- **Project number:** 5R01CA207342-07
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Sua Myong
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $441,523
- **Award type:** 5
- **Project period:** 2017-03-08 → 2028-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10829460

## Citation

> US National Institutes of Health, RePORTER application 10829460, Roles of Telomeric Oxidative DNA Lesions in Telomere Length Regulation (5R01CA207342-07). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10829460. Licensed CC0.

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