CTC1-STN1-TEN1 controls DNA break repair pathway choice via DNA end resection blockade
- Cody M. Rogers
- Hardeep Kaur
- Michelle L. Swift
- Vivek B. Raina
- Shuo Zhou
- Ajinkya S. Kawale
- Shahrez Syed
- Korilynn G. Kelly
- Angela M. Jasper
- Sameer Salunkhe
- Youngho Kwon
- Jeffrey Wang
- Aida Badamchi Shabestari
- James M. Daley
- Adam Sacks
- Maria E. Gaczynska
- Pawel A. Osmulski
- Yashpal Rawal
- Nozomi Tomimatsu
- Simon A. Gayther
- Kate Lawrenson
- Sandeep Burma
- Elizabeth V. Wasmuth
- Shaun K. Olsen
- Weixing Zhao
- Robert Hromas
- David S. Libich
- Alexander V. Mazin
- Daohong Zhou
- Eric C. Greene
- Dipanjan Chowdhury
- Patrick Sung
2025-05-23
Antagonistic activities of the 53BP1 axis and the tumor suppressor BRCA1-BARD1 determine whether DNA double-strand breaks (DSBs) are repaired by end joining or homologous recombination. We show that the CTC1-STN1-TEN1 (CST) complex, a central 53BP1 axis component, suppresses DNA end resection by EXO1 and the BLM-DNA2 helicase-nuclease complex but acts by distinct mechanisms in restricting these entities. Whereas BRCA1-BARD1 alleviates the CST-imposed EXO1 blockade, it has little effect on BLM-DNA2 restriction. CST mutants impaired for DNA binding or BLM–EXO1 interaction exhibit a hyper-resection phenotype and render BRCA1-deficient cells resistant to poly(ADP–ribose) polymerase (PARP) inhibitors. Our findings mechanistically define the crucial role of CST in DNA DSB repair pathway choice and have implications for understanding cancer therapy resistance stemming from dysfunction of the 53BP1 axis.