Synergistic protection of nascent DNA at stalled forks by MSANTD4 and BRCA1/2-RAD51

Haihua Xie; Lizhi Song; Genxiang Mao; Jinhua Han; Jiali Pu; Zhibing Wu; Jun Chen; Jianwei Zhou; Jun Huang; Dong Fang; Ting Liu

doi:10.1038/s41589-024-01833-9

Synergistic protection of nascent DNA at stalled forks by MSANTD4 and BRCA1/2-RAD51

Nat Chem Biol. 2025 Jan 14. doi: 10.1038/s41589-024-01833-9. Online ahead of print.

Authors

Haihua Xie^#^{1

2

3}, Lizhi Song^#^{4

5}, Genxiang Mao³, Jinhua Han³, Jiali Pu⁶, Zhibing Wu³, Jun Chen³, Jianwei Zhou¹, Jun Huang^{7

8

9}, Dong Fang¹⁰, Ting Liu^{11

12

13}

Affiliations

¹ Department of Gynecology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
² Department of Cell Biology, Zhejiang University School of Medicine, Hangzhou, China.
³ Zhejiang Key Laboratory of Geriatrics and Geriatrics Institute of Zhejiang Province, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, China.
⁴ MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, China.
⁵ Center for Life Sciences, Shaoxing Institute, Zhejiang University, Shaoxing, China.
⁶ Department of Neurology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
⁷ Zhejiang Key Laboratory of Geriatrics and Geriatrics Institute of Zhejiang Province, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, China. jhuang@zju.edu.cn.
⁸ MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, China. jhuang@zju.edu.cn.
⁹ Center for Life Sciences, Shaoxing Institute, Zhejiang University, Shaoxing, China. jhuang@zju.edu.cn.
¹⁰ MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, Life Sciences Institute, Zhejiang University, Hangzhou, China. dfang@zju.edu.cn.
¹¹ Department of Gynecology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China. liuting518@zju.edu.cn.
¹² Department of Cell Biology, Zhejiang University School of Medicine, Hangzhou, China. liuting518@zju.edu.cn.
¹³ Zhejiang Key Laboratory of Geriatrics and Geriatrics Institute of Zhejiang Province, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, China. liuting518@zju.edu.cn.

^# Contributed equally.

PMID: 39809895
DOI: 10.1038/s41589-024-01833-9

Abstract

The regressed arms of reversed replication forks exhibit structural similarities to one-ended double-stranded breaks and need to be protected against uncontrolled nucleolytic degradation. Here, we identify MSANTD4 (Myb/SANT-like DNA-binding domain-containing protein 4), a functionally uncharacterized protein that uniquely counters the replication protein A (RPA)-Bloom (BLM)/Werner syndrome helicase (WRN)-DNA replication helicase/nuclease 2 (DNA2) complex to safeguard reversed replication forks from detrimental degradation, independently of the breast cancer susceptibility proteins (BRCA1/2)-DNA repair protein RAD51 pathway. MSANTD4 specifically interacts with the junctions between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in DNA substrates harboring a 3' overhang, which resemble the structural features of regressed arms processed by WRN-DNA2. This DNA-binding capability allows MSANTD4 to accumulate at reversed forks, strategically antagonizing the RPA-BLM/WRN-DNA2 complex by impeding its access to the ssDNA-dsDNA junction of the regressed arms. Loss of MSANTD4 exacerbates genome instability induced by replication stress in BRCA1/2-deficient cells. Our findings unveil a collaborative defense mechanism orchestrated by MSANTD4 and BRCA1/2-RAD51, effectively counteracting nucleolytic attacks on the regressed arms and synergistically preserving the integrity of reversed forks.