Abstract

Mutations in the global transcriptional activator EP300/KAT3B are being reported in aggressive malignancies. However, the mechanistic contribution of EP300 dysregulation to cancer is currently unknown. While EP300 has been implicated in regulating cell cycle and DNA replication, the role of EP300 in maintaining replication fork integrity has not been studied. Here, using EP300-mutated adult T-cell leukemia/lymphoma cells and an EP300-selective degrader, we reveal that EP300 loss leads to pronounced dysregulations in DNA replication dynamics and persistent genomic instability. Aberrant DNA replication in EP300-mutated cells is characterized by elevated replication origin firing due to replisome pausing. EP300 deficiency results in a prominent defect in fork protection resulting in the accumulation of single-stranded DNA gaps. Importantly, we find that the loss of EP300 results in decreased expression of BRCA2 protein leading to sensitivity to treatments that are cytotoxic to BRCA-deficient cancers. Overall, we demonstrate that EP300-mutated cells recapitulate features of BRCA-deficient cancers.

Data availability

All RNA sequencing data discussed in this study have been deposited at NCBI’s Gene Expression Omnibus under the GEO series accession number GSE303280. Source data are provided with this paper.

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Acknowledgements

We thank the Rutgers Cancer Institute, Immune Monitoring and Flow Cytometry Shared Resource, which is supported, in part, with funding from the NCI-CCSG P30CA072770-5920 for their support. We also thank Dr. Tzeh Keong Foo for his valuable discussions. The work was supported by an American Cancer Society pilot award to A.M, R00HL136870 to A.M, R01CA266847 to B.H.Y., K08CA245251 to A.D.D., R37CA286444 to A.D.D., and R01CA275187 to A.D.D., the V Foundation for Cancer Research to A.D.D., the Hyundai Hope on Wheels Foundation and the American Lebanese Syrian Associated Charities to A.D.D., ALSF to J.Q., Curing Kids Cancer to J.Q., Wong Family foundation grant to J.Q., R35GM152228 to J.G. R01ES034733 to J.G., R01CA138804 to B.X., R01CA262227 to B.X., and P01250957-9485 to B.X.

Author information

Author notes

These authors contributed equally: Angelica Barreto-Galvez, Mrunmai Niljikar.

Authors and Affiliations

Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA

Angelica Barreto-Galvez, Mrunmai Niljikar, Julia Elizabeth Gagliardi, Carolina Plasencia Guzman, Ranran Zhang, Vasudha Kumar, Aastha Juwarwala, Archana Pradeep, Ankit Saxena, Cristina Montagna, Jian Cao & Advaitha Madireddy 1.

Department of Genetics, Albert Einstein College of Medicine, Bronx, NY, USA

Cristina Montagna 1.

Center of Excellence in Neuro-Oncology Sciences (CENOS), St. Jude Children’s Research Hospital, Memphis, TN, USA

Priya Mittal 1.

Department of Obstetrics and Gynecology, Weill Cornell Medicine, New York, NY, USA

Jeannine Gerhardt 1.

Department of Radiation Oncology, Rutgers University, New Brunswick, NJ, USA

Bing Xia 1.

Department of Medicine, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, USA

Jian Cao 1.

Division of Molecular Oncology, National Cancer Center Research Institute, Tokyo, Japan

Keisuke Kataoka 1.

Department of Oncology, St. Jude Comprehensive Cancer Center, Memphis, TN, USA

Adam David Durbin 1.

Department of Cancer Biology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA

Jun Qi 1.

Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY, USA

B. Hilda Ye 1.

Department of Pediatrics Hematology/Oncology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, USA

Advaitha Madireddy

Authors

1. Angelica Barreto-Galvez
2. Mrunmai Niljikar
3. Julia Elizabeth Gagliardi
4. Carolina Plasencia Guzman
5. Ranran Zhang
6. Vasudha Kumar
7. Aastha Juwarwala
8. Archana Pradeep
9. Ankit Saxena
10. Cristina Montagna
11. Priya Mittal
12. Jeannine Gerhardt
13. Bing Xia
14. Jian Cao
15. Keisuke Kataoka
16. Adam David Durbin
17. Jun Qi
18. B. Hilda Ye
19. Advaitha Madireddy

Contributions

The project was conceived by A.M. Most of the experiments were conducted by A.B.G. and M.N. A.B.G. and M.N. contributed equally to this manuscript and hence share co-first authorship. The Comet assay was conducted by J.E.G.; Some of the EP300 and CBP immunoblots were carried out by A.D.D.; Data analysis was carried out by A.B.G., M.N., J.E.G., R.Z., V.K., A.J., A.P., P.M., and I.S. The NA-ATLL and J-ATLL cell lines were provided by B.H.Y. The JQAD1 compound was provided by J.Q. The data was analyzed and discussed by A.M., J.G., J.C., K.K., A.D.D., P.M., C.M., and B.H.Y. The manuscript was written by A.M.

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Correspondence to Advaitha Madireddy.

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Barreto-Galvez, A., Niljikar, M., Gagliardi, J.E. et al. EP300 deficiency leads to chronic replication stress mediated by defective replication fork protection. Nat Commun (2025). https://doi.org/10.1038/s41467-025-67171-z

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Received: 22 September 2023

Accepted: 21 November 2025

Published: 07 December 2025

DOI: https://doi.org/10.1038/s41467-025-67171-z