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Crosstalk between CST and RPA regulates RAD51 activity during replication stress
Kai-Hang Lei1, Han-Lin Yang2, Hao-Yen Chang1
1Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
Nature Communications
|November 6, 2021
Summary
The CTC1-STN1-TEN1 (CST) complex targets RAD51 to RPA-coated ssDNA during replication stress. CST facilitates RAD51 activity on ssDNA, crucial for DNA repair pathways.
Area of Science:
- Molecular Biology
- DNA Replication
- DNA Repair
Background:
- Replication stress leads to stalled replication forks and single-stranded DNA (ssDNA) accumulation.
- Replication protein A (RPA) and the CTC1-STN1-TEN1 (CST) complex bind ssDNA at stalled forks.
- Both complexes play roles in regulating RAD51 recruitment and foci formation.
Purpose of the Study:
- To investigate the crosstalk and interplay between RPA, CST, and RAD51.
- To elucidate the mechanism by which CST targets RAD51 to RPA-coated ssDNA.
Main Methods:
- Cellular localization studies to assess proximity of CST and RPA.
- In vitro binding assays to analyze CST-ssDNA interactions under varying ionic strengths.
- Biochemical assays to evaluate RAD51 filament formation and strand-exchange activity on CST- and RPA-coated ssDNA.
Main Results:
- CST and RPA are found in close proximity within cells.
- CST binding to ssDNA is dynamic and facilitated for dissociation at high ionic strength.
- CST can coexist with RPA on ssDNA and directs RAD51 to RPA-coated ssDNA.
- RAD51 activity is inhibited on RPA-coated ssDNA but functional on CST-coated ssDNA at high ionic strength.
Conclusions:
- CST acts as a crucial mediator, targeting and tethering RAD51 to RPA-bound ssDNA during replication stress.
- The dynamic interaction of CST with ssDNA, particularly at high ionic strength, is key for facilitating RAD51 assembly and function.
- These findings provide mechanistic insights into DNA repair regulation following replication fork stalling.
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