DNA-PK enforces the S/G2 checkpoint in ATM-deficient cells to limit ATR inhibitor efficacy
Abstract
ATR inhibition has been proposed as a strategy for tumors under replication stress or those harboring ATM deficiency. However, anti-tumor activity is limited by DNA-PK and ATM compensation. Here, we have delineated distinct roles for DNA-PK and ATM during ATR inhibitor exposure. Both kinases are activated in a cell cycle-dependent manner at the S/G2 boundary following ATR inhibition. DNA-PK imposes the S/G2 checkpoint and promotes completion of DNA replication, whereas ATM detects persistent aberrant DNA replication structures with associated DNA damage in late S and G2/M to establish a G2/M checkpoint promoting DNA repair. In ATM-deficient cells and patient tumors, DNA-PK is activated following ATR inhibition and assumes greater versatility by not only enforcing the S/G2 checkpoint but also by detecting aberrant replication structures in S phase in place of ATM, allowing cells to tolerate ATR inhibition. Consequently, DNA-PK inhibition synergizes with ATR inhibition in ATM-deficient cells and enhances ATR inhibitor efficacy in ATM-deficient PDX models. These data support clinical evaluation of combined ATR and DNA-PK inhibition in ATM-deficient cancers.
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BibTeX
@misc{branigan2026dnapk,
title = {{DNA-PK enforces the S/G2 checkpoint in ATM-deficient cells to limit ATR inhibitor efficacy}},
author = {Timothy B. Branigan and Roshen Alharthi and Bose S. Kochupurakkal and Jie Hao and Steffie Revia and Joachim Albers and Mu-Yan Cai and Yuqing Jiao and Kelsey McQueen and Sirisha Mukkavalli and Ian A. Roundtree and Gregory M. Cote and Prafulla C. Gokhale and Kalindi Parmar and Alan D. D’Andrea and Astrid Zimmermann and Geoffrey I. Shapiro},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.25.761677},
url = {https://www.biorxiv.org/content/10.64898/2026.10.25.761677v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - DNA-PK enforces the S/G2 checkpoint in ATM-deficient cells to limit ATR inhibitor efficacy
AU - Timothy B. Branigan
AU - Roshen Alharthi
AU - Bose S. Kochupurakkal
AU - Jie Hao
AU - Steffie Revia
AU - Joachim Albers
AU - Mu-Yan Cai
AU - Yuqing Jiao
AU - Kelsey McQueen
AU - Sirisha Mukkavalli
AU - Ian A. Roundtree
AU - Gregory M. Cote
AU - Prafulla C. Gokhale
AU - Kalindi Parmar
AU - Alan D. D’Andrea
AU - Astrid Zimmermann
AU - Geoffrey I. Shapiro
PY - 2026
DA - 2026/10/25
PB - bioRxiv
DO - 10.64898/2026.10.25.761677
UR - https://www.biorxiv.org/content/10.64898/2026.10.25.761677v1
AB - ATR inhibition has been proposed as a strategy for tumors under replication stress or those harboring ATM deficiency. However, anti-tumor activity is limited by DNA-PK and ATM compensation. Here, we have delineated distinct roles for DNA-PK and ATM during ATR inhibitor exposure. Both kinases are activated in a cell cycle-dependent manner at the S/G2 boundary following ATR inhibition. DNA-PK imposes the S/G2 checkpoint and promotes completion of DNA replication, whereas ATM detects persistent aberrant DNA replication structures with associated DNA damage in late S and G2/M to establish a G2/M checkpoint promoting DNA repair. In ATM-deficient cells and patient tumors, DNA-PK is activated following ATR inhibition and assumes greater versatility by not only enforcing the S/G2 checkpoint but also by detecting aberrant replication structures in S phase in place of ATM, allowing cells to tolerate ATR inhibition. Consequently, DNA-PK inhibition synergizes with ATR inhibition in ATM-deficient cells and enhances ATR inhibitor efficacy in ATM-deficient PDX models. These data support clinical evaluation of combined ATR and DNA-PK inhibition in ATM-deficient cancers.
SN - 2692-8205
ER -