Biology subjects

Barnes, R. P.

Publications and source records attributed to Barnes, R. P..

3 recordsLinked to original sources

bioRxiv2025

Oxidative Base Damage to Telomeres Sensitizes Cancer Cells to ATR Inhibition

Targeted inhibition of DNA damage response proteins has received significant clinical attention owing to the success of PARP inhibitors. Due to the loss of the G1/S checkpoint, cancer cells are reliant on the G2/M checkpoint to cope with elevated DNA replication stress. We previously demonstrated a single induction of 8-oxo-guanine at telomeres in cancer cells was sufficient to induce replication stress, but was well tolerated at the cellular level. Here, we found inhibition of ATR, Chk1, or Wee1 after induction of telomere oxidative stress significantly induced genome instability and reduced cell viability. This occurred at doses markedly less than those required to increase instability in non-cancer cells. We determined the mechanism of this instability is due to cells progressing through S-phase with telomere damage and exiting G2-phase prematurely, prolonging their mitosis. This study demonstrates targeted oxidative base damage at telomeres can enhance the therapeutic efficacy of ATR inhibition in cancer.

cancer biology↗

bioRxiv2023

OGG1 and MUTYH repair activities promote telomeric 8-oxoguanine induced cellular senescence

Telomeres are prone to formation of the common oxidative lesion 8-oxoguanine (8oxoG), and the acute production of 8oxoG damage at telomeres is sufficient to drive rapid cellular senescence. OGG1 and MUTYH glycosylases initiate base excision repair (BER) at 8oxoG sites to remove the lesion or prevent mutation. Here, we show OGG1 loss or inhibition, or MUTYH loss, partially rescues telomeric 8oxoG-induced senescence, and loss of both glycosylases results in a near complete rescue. Loss of these glycosylases also suppresses 8oxoG-induced telomere fragility and dysfunction, indicating that single-stranded break (SSB) intermediates arising downstream of glycosylase activity impair telomere replication. The failure to initiate BER in glycosylase-deficient cells suppresses PARylation at SSB intermediates and confers resistance to the synergistic effects of PARP inhibitors on damage-induced senescence. Our studies reveal that inefficient completion of 8oxoG BER at telomeres triggers cellular senescence via SSB intermediates which impair telomere replication and stability.

molecular biology↗

bioRxiv2021

Telomeric 8-oxoguanine drives rapid premature senescence in the absence of telomere shortening

Oxidative stress is a primary cause of cellular senescence and contributes to the pathogenesis of numerous human diseases. Oxidative damage to telomeric DNA is proposed to trigger premature senescence by accelerating telomere shortening. Here we tested this model directly using a precision tool to produce the common base lesion 8-oxo-guanine (8oxoG) exclusively at telomeres in human fibroblast and epithelial cells. A single induction of telomeric 8oxoG is sufficient to trigger multiple hallmarks of p53-dependent senescence. Telomeric 8oxoG activates ATM and ATR signaling, and enriches for markers of telomere dysfunction in replicating, but not quiescent cells. Acute 8oxoG production fails to shorten telomeres, but rather generates fragile sites and delayed mitotic DNA synthesis at telomeres, indicative of impaired replication. Based on our results we propose that oxidative stress promotes rapid senescence by producing oxidative base lesions which drive replication-dependent telomere fragility and dysfunction in the absence of shortening and shelterin loss.

molecular biology↗