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Updated: Oct 16, 2025
Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Non-Recombinogenic Functions of Rad51, BRCA2, and Rad52 in DNA Damage Tolerance
1Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Universidad Pablo de Olavide, 41092 Seville, Spain.
Abstract:
The DNA damage tolerance (DDT) response is aimed to timely and safely complete DNA replication by facilitating the advance of replication forks through blocking lesions. This process is associated with an accumulation of single-strand DNA (ssDNA), both at the fork and behind the fork. Lesion bypass and ssDNA filling can be performed by translation synthesis (TLS) and template switching mechanisms. TLS uses low-fidelity polymerases to incorporate a dNTP opposite the blocking lesion, whereas template switching uses a Rad51/ssDNA nucleofilament and the sister chromatid to bypass the lesion. Rad51 is loaded at this nucleofilament by two mediator proteins, BRCA2 and Rad52, and these three factors are critical for homologous recombination (HR). Here, we review recent advances showing that Rad51, BRCA2, and Rad52 perform some of these functions through mechanisms that do not require the strand exchange activity of Rad51: the formation and protection of reversed fork structures aimed to bypass blocking lesions, and the promotion of TLS. These findings point to the central HR proteins as potential molecular switches in the choice of the mechanism of DDT.
Insights
The DNA damage tolerance (DDT) response ensures DNA replication completion through mechanisms like translesion synthesis (TLS) and template switching. Central homologous recombination (HR) proteins, Rad51, BRCA2, and Rad52, act as molecular switches in choosing DDT pathways.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- DNA damage tolerance (DDT) is crucial for completing DNA replication past lesions.
- DDT involves translesion synthesis (TLS) and template switching.
- Homologous recombination (HR) proteins Rad51, BRCA2, and Rad52 are key in DNA repair.
Purpose of the Study:
- To review recent advances in understanding the roles of Rad51, BRCA2, and Rad52 in DDT.
- To explore how these proteins function in lesion bypass and replication fork stabilization.
- To highlight the potential of HR proteins as regulators of DDT pathway choice.
Main Methods:
- Literature review of recent research on DNA damage tolerance.
- Analysis of the mechanisms employed by Rad51, BRCA2, and Rad52 in DNA replication.
- Examination of the interplay between HR proteins and TLS polymerases.
Main Results:
- Rad51, BRCA2, and Rad52 facilitate DDT through mechanisms independent of Rad51's strand exchange activity.
- These proteins protect and stabilize reversed replication fork structures.
- They also promote translesion synthesis (TLS) for lesion bypass.
Conclusions:
- Central HR proteins (Rad51, BRCA2, Rad52) play multifaceted roles in DNA damage tolerance.
- These proteins act as molecular switches, directing the cell towards specific DDT pathways.
- Understanding these mechanisms is vital for comprehending genome stability and cancer biology.
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