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Double-strand break repair-independent role for BRCA2 in blocking stalled replication fork degradation by MRE11.
Cell. 2011 May 13; 145(4):529-42
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24 May 2011
New Finding
DOI: 10.3410/f.10727956.11620054
This is the first study to demonstrate that BRCA2 inhibits the degradation of stalled replication forks by the MRE11 nuclease.
In the absence of BRCA2, hydroxyurea (HU)-induced stalled replication forks are degraded by an MRE11-dependent process. This novel function of BRCA2 in fork protection requires...Continue reading
In the absence of BRCA2, hydroxyurea (HU)-induced stalled replication forks are degraded by an MRE11-dependent process. This novel function of BRCA2 in fork protection requires...Continue reading
This is the first study to demonstrate that BRCA2 inhibits the degradation of stalled replication forks by the MRE11 nuclease.
In the absence of BRCA2, hydroxyurea (HU)-induced stalled replication forks are degraded by an MRE11-dependent process. This novel function of BRCA2 in fork protection requires the C-terminal RAD51-interacting domain and is distinct from the role of BRCA2 in homologous recombination. Stabilization of RAD51 filaments with a RAD51 ATPase mutant suppresses the degradation of stalled forks in BRCA2 deficient cells. Cells expressing a BRCA2 mutant unable to inhibit degradation of stalled forks are only modestly sensitive to HU and not sensitive to poly (ADP-ribose) polymerase (PARP) inhibition.
In the absence of BRCA2, hydroxyurea (HU)-induced stalled replication forks are degraded by an MRE11-dependent process. This novel function of BRCA2 in fork protection requires the C-terminal RAD51-interacting domain and is distinct from the role of BRCA2 in homologous recombination. Stabilization of RAD51 filaments with a RAD51 ATPase mutant suppresses the degradation of stalled forks in BRCA2 deficient cells. Cells expressing a BRCA2 mutant unable to inhibit degradation of stalled forks are only modestly sensitive to HU and not sensitive to poly (ADP-ribose) polymerase (PARP) inhibition.
Disclosures
None declared
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Zou L: F1000Prime Recommendation of [Schlacher K et al., Cell 2011, 145(4):529-42]. In F1000Prime, 24 May 2011; DOI: 10.3410/f.10727956.11620054. F1000Prime.com/10727956#eval11620054
02 Jun 2011
New Finding
DOI: 10.3410/f.10727956.11823055
This article reports the interesting new finding that the breast cancer tumor suppressor BRCA2 protects stalled DNA replication forks from degradation, an activity different from its role in homologous recombination.
The nucleoprotein filament formed when RAD51 recombinase polymerizes along single-stranded...Continue reading
The nucleoprotein filament formed when RAD51 recombinase polymerizes along single-stranded...Continue reading
This article reports the interesting new finding that the breast cancer tumor suppressor BRCA2 protects stalled DNA replication forks from degradation, an activity different from its role in homologous recombination.
The nucleoprotein filament formed when RAD51 recombinase polymerizes along single-stranded DNA (ssDNA) is the active catalyst in promoting homologous pairing and DNA strand exchange, the central reaction in the homology-directed DNA repair (HR) pathway. Regulation of filament formation and stabilization are key aspects to the control of HR. The breast cancer tumor suppressor BRCA2, which has capacities to bind RAD51 and ssDNA, serves an essential function in this process by enabling RAD51 to gain access to ssDNA. Here, the Jasin laboratory reports a novel function for BRCA2 in a process beyond HR. Using DNA fiber analysis to visualize single molecules, the Jasin laboratory demonstrated that nascent DNA replication tracts are degraded when fork progression stalls in the absence of BRCA2. This fork protection depends on the RAD51-interaction motif BRC and the unrelated RAD51-interaction domain at the extreme C-terminus of BRCA2, but not the DNA-binding domain. The mechanism of BRCA2-enhanced replication fork maintenance appears to be due to stabilization of RAD51 filaments formed on exposed ssDNA at the fork through association with the C-terminal RAD-interaction region of BRCA2. The investigators propose a model in which BRCA2 prevents degradation of stalled replication fork intermediates that have reversed to form a regressed fork structure.
The nucleoprotein filament formed when RAD51 recombinase polymerizes along single-stranded DNA (ssDNA) is the active catalyst in promoting homologous pairing and DNA strand exchange, the central reaction in the homology-directed DNA repair (HR) pathway. Regulation of filament formation and stabilization are key aspects to the control of HR. The breast cancer tumor suppressor BRCA2, which has capacities to bind RAD51 and ssDNA, serves an essential function in this process by enabling RAD51 to gain access to ssDNA. Here, the Jasin laboratory reports a novel function for BRCA2 in a process beyond HR. Using DNA fiber analysis to visualize single molecules, the Jasin laboratory demonstrated that nascent DNA replication tracts are degraded when fork progression stalls in the absence of BRCA2. This fork protection depends on the RAD51-interaction motif BRC and the unrelated RAD51-interaction domain at the extreme C-terminus of BRCA2, but not the DNA-binding domain. The mechanism of BRCA2-enhanced replication fork maintenance appears to be due to stabilization of RAD51 filaments formed on exposed ssDNA at the fork through association with the C-terminal RAD-interaction region of BRCA2. The investigators propose a model in which BRCA2 prevents degradation of stalled replication fork intermediates that have reversed to form a regressed fork structure.
Disclosures
None declared
Holloman W: F1000Prime Recommendation of [Schlacher K et al., Cell 2011, 145(4):529-42]. In F1000Prime, 02 Jun 2011; DOI: 10.3410/f.10727956.11823055. F1000Prime.com/10727956#eval11823055
16 Jun 2011
New Finding
DOI: 10.3410/f.10727956.12306054
BRCA2, a breast cancer suppressor, is known to be involved in error-free repair of DNA double-strand breaks by homologous recombination (HR). This article puts forth a novel function of BRAC2 in maintaining genomic integrity by preventing the degradation of stalled replication forks.
The role of BRCA2...Continue reading
The role of BRCA2...Continue reading
BRCA2, a breast cancer suppressor, is known to be involved in error-free repair of DNA double-strand breaks by homologous recombination (HR). This article puts forth a novel function of BRAC2 in maintaining genomic integrity by preventing the degradation of stalled replication forks.
The role of BRCA2 in DNA damage repair by HR is known to be mediated by the formation of the RAD51 nucleoprotein filament on single-stranded DNA {1}. BRCA2 protein binds RAD51 through its BRC motifs and the C-terminal, though the interaction through the latter is dispensable for HR function. By performing single-molecule DNA fiber studies, the authors very elegantly show that nascent strands generated before stalling of the fork by replication inhibitor (hydroxyurea) are degraded in the absence of BRCA2. This protective function of BRCA2 is facilitated by its C-terminal motif that interacts and stabilizes the RAD51 filaments at stalled forks. In the absence of BRCA2, or mutation of its C-terminal, nucleolytic degradation of the stalled fork occurs by the nuclease activity of MRE11. This degradation increases the breaks and gaps in the chromosomes, eventually leading to aberrant inter-chromosomal end-joining. These findings are novel as, in addition to the existing DNA damage repair function of BRCA2 {2}, this paper highlights a new preventive mechanism by which this molecule helps maintain genome integrity.
The role of BRCA2 in DNA damage repair by HR is known to be mediated by the formation of the RAD51 nucleoprotein filament on single-stranded DNA {1}. BRCA2 protein binds RAD51 through its BRC motifs and the C-terminal, though the interaction through the latter is dispensable for HR function. By performing single-molecule DNA fiber studies, the authors very elegantly show that nascent strands generated before stalling of the fork by replication inhibitor (hydroxyurea) are degraded in the absence of BRCA2. This protective function of BRCA2 is facilitated by its C-terminal motif that interacts and stabilizes the RAD51 filaments at stalled forks. In the absence of BRCA2, or mutation of its C-terminal, nucleolytic degradation of the stalled fork occurs by the nuclease activity of MRE11. This degradation increases the breaks and gaps in the chromosomes, eventually leading to aberrant inter-chromosomal end-joining. These findings are novel as, in addition to the existing DNA damage repair function of BRCA2 {2}, this paper highlights a new preventive mechanism by which this molecule helps maintain genome integrity.
References
Disclosures
None declared
Dutta A and Karnani N: F1000Prime Recommendation of [Schlacher K et al., Cell 2011, 145(4):529-42]. In F1000Prime, 16 Jun 2011; DOI: 10.3410/f.10727956.12306054. F1000Prime.com/10727956#eval12306054
21 Dec 2012
Good for Teaching, Interesting Hypothesis, New Finding, Technical Advance
DOI: 10.3410/f.10727956.793467393
Jasin, Schlacher and their colleagues have developed and applied single-molecule analyses of DNA replication forks to reveal novel fork-protection pathway functions, independent of the known BRCA2 functions.
Specifically, they discovered that BRCA2 pathway members protect stalled replication forks...Continue reading
Specifically, they discovered that BRCA2 pathway members protect stalled replication forks...Continue reading
Jasin, Schlacher and their colleagues have developed and applied single-molecule analyses of DNA replication forks to reveal novel fork-protection pathway functions, independent of the known BRCA2 functions.
Specifically, they discovered that BRCA2 pathway members protect stalled replication forks from MRE11-dependent degradation to prevent chromosomal instability.
The concept of protection pathways in addition to the DNA repair pathways provides a paradigm shift in understanding cellular responses to stress and ways to intervene in cancer.
Specifically, they discovered that BRCA2 pathway members protect stalled replication forks from MRE11-dependent degradation to prevent chromosomal instability.
The concept of protection pathways in addition to the DNA repair pathways provides a paradigm shift in understanding cellular responses to stress and ways to intervene in cancer.
Disclosures
John Tainer has personal relationships with Dr Maria Jasin and Dr Katharina Schlacher, two authors of the recommended article. John Tainer was not involved with the current study in any way, which was selected for recommendation based entirely on its scientific merit.
Tainer J: F1000Prime Recommendation of [Schlacher K et al., Cell 2011, 145(4):529-42]. In F1000Prime, 21 Dec 2012; DOI: 10.3410/f.10727956.793467393. F1000Prime.com/10727956#eval793467393
F1000Prime Recommendations, Dissents and Comments for [Schlacher K et al., Cell 2011, 145(4):529-42]. In F1000Prime, 26 May 2013; F1000Prime.com/10727956
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Breast cancer suppressor BRCA2 is critical for maintenance of genomic integrity and resistance to agents that damage DNA or collapse replication forks, presumably through homology-directed repair of double-strand breaks (HDR). Using single-molecule DNA fiber analysis, we show here that nascent replication tracts created before fork stalling with hydroxyurea are degraded in the absence of BRCA2 but are stable in wild-type cells. BRCA2 mutational analysis reveals that a conserved C-terminal site involved in stabilizing RAD51 filaments, but not in loading RAD51 onto DNA, is essential for this fork protection but dispensable for HDR. RAD51 filament disruption in wild-type cells phenocopies BRCA2 deficiency. BRCA2 prevents chromosomal aberrations on replication stalling, which are alleviated by inhibition of MRE11, the nuclease responsible for this form of fork instability. Thus, BRCA2 prevents rather than repairs nucleolytic lesions at stalled replication forks to maintain genomic integrity and hence likely suppresses tumorigenesis through this replication-specific function.
Copyright © 2011 Elsevier Inc. All rights reserved.
DOI: 10.1016/j.cell.2011.03.041
PMID: 21565612
