CryoEM micrographs of RAD51 filaments on ssDNA bound by the BRCA2 c-terminus
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ABSTRACT:
SUBMITTER: Luca Pellegrini
PROVIDER: EMPIAR-11790 | biostudies-other |
REPOSITORIES: biostudies-other
Publications
Structural basis for stabilisation of the RAD51 nucleoprotein filament by BRCA2.
Appleby Robert R Joudeh Luay L Cobbett Katie K Pellegrini Luca L
Nature communications 20231102 1
The BRCA2 tumour suppressor protein preserves genomic integrity via interactions with the DNA-strand exchange RAD51 protein in homology-directed repair. The RAD51-binding TR2 motif at the BRCA2 C-terminus is essential for protection and restart of stalled replication forks. Biochemical evidence shows that TR2 recognises filamentous RAD51, but existing models of TR2 binding to RAD51 lack a structural basis. Here we used cryo-electron microscopy and structure-guided mutagenesis to elucidate the me ...[more]
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Project description: Not available
| EMPIAR-11794 | biostudies-other
Project description:BRCA2 has an essential function in DNA repair by homologous recombination, interacting with RAD51 via short motifs in the middle and at the C terminus of BRCA2. Here, we report that a conserved 36-residue sequence of human BRCA2 encoded by exon 27 (BRCA2Exon27) interacts with RAD51 through the specific recognition of oligomerized RAD51 ATPase domains. BRCA2Exon27 binding stabilizes the RAD51 nucleoprotein filament against disassembly by BRC repeat 4. The protection is specific for RAD51 filaments formed on single-stranded DNA and is lost when BRCA2Exon27 is phosphorylated on Ser3291. We propose that productive recombination results from the functional balance between the different RAD51-binding modes [corrected] of the BRC repeat and exon 27 regions of BRCA2. Our results further suggest a mechanism in which CDK phosphorylation of BRCA2Exon27 at the G2-M transition alters the balance in favor of RAD51 filament disassembly, thus terminating recombination.
| S-EPMC2096194 | biostudies-literature
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| EMPIAR-11696 | biostudies-other
Project description:BackgroundThe Rad51 recombinase assembles on DNA to execute homologous DNA recombination (HR). This process is essential to repair replication-associated genomic lesions before cells enter mitosis, but how it is started and stopped during the cell cycle remains poorly understood. Rad51 assembly is regulated by the breast cancer suppressor Brca2, via its evolutionarily conserved BRC repeats, and a distinct carboxy (C)-terminal motif whose biological function is uncertain. Using "hit-and-run" gene targeting to insert single-codon substitutions into the avian Brca2 locus, we report here a previously unrecognized role for the C-terminal motif.ResultsWe show that the avian C-terminal motif is functionally cognate with its human counterpart and identify point mutations that either abolish or enhance Rad51 binding. When these mutations are introduced into Brca2, we find that they affect neither the assembly of Rad51 into nuclear foci on damaged DNA nor DNA repair by HR. Instead, foci disassemble more rapidly in a point mutant that fails to bind Rad51, associated with faster mitotic entry. Conversely, the slower disassembly of foci in a point mutant that constitutively binds Rad51 correlates with delayed mitosis. Indeed, Rad51 foci do not persist in mitotic cells even after G2 checkpoint suppression, suggesting that their disassembly is a prerequisite for chromosome segregation.ConclusionsWe conclude that Rad51 binding by the C-terminal Brca2 motif is dispensable for the execution of HR but instead links the disassembly of Rad51 complexes to mitotic entry. This mechanism may ensure that HR terminates before chromosome segregation. Our findings assign a biological function for the C-terminal Brca2 motif in a mechanism that coordinates DNA repair with the cell cycle.
| S-EPMC2719694 | biostudies-literature
Project description:Homologous recombination is essential for the preservation of genome stability, thereby preventing cancer. The recombination protein RAD51 drives DNA strand exchange, which requires the assembly, rearrangement and disassembly of a RAD51 filament on DNA, coupled to ATP binding and hydrolysis. This process is facilitated and controlled by recombination mediators and accessory factors. Here, we have employed a range of single molecule techniques to determine the influence of the C-terminal RAD51 interaction domain (CTRD) of the breast cancer tumor suppressor BRCA2 on intrinsic aspects of RAD51-DNA interactions. We show that at high concentration the CTRD entangles RAD51 filaments and reduces RAD51 filament formation in a concentration dependent manner. It does not affect the rate of filament disassembly measured as the loss of fluorescent signal due to intrinsic RAD51 protein dissociation from double-stranded DNA (dsDNA). We conclude that, outside the context of the full-length protein, the CTRD does not reduce RAD51 dissociation kinetics, but instead hinders filament formation on dsDNA. The CTRDs mode of action is most likely sequestration of multiple RAD51 molecules thereby rendering them inactive for filament formation on dsDNA.
| S-EPMC3159462 | biostudies-literature
Project description: Not available
| EMPIAR-10261 | biostudies-other
Project description:The bypass of DNA lesions that block replicative polymerases during DNA replication relies on DNA damage tolerance pathways. The error-prone translesion synthesis (TLS) pathway depends on specialized DNA polymerases that incorporate nucleotides in front of base lesions, potentially inducing mutagenesis. Two error-free pathways can bypass the lesions: the template switching pathway, which uses the sister chromatid as a template, and the homologous recombination pathway (HR), which also can use the homologous chromosome as template. The balance between error-prone and error-free pathways controls the mutagenesis level. Therefore, it is crucial to precisely characterize factors that influence the pathway choice to better understand genetic stability at replication forks. In yeast, the complex formed by the Rad51 paralogs Rad55 and Rad57 promotes HR and template-switching at stalled replication forks. At DNA double-strand breaks (DSBs), this complex promotes Rad51 filament formation and stability, notably by counteracting the Srs2 anti-recombinase. To explore the role of the Rad55-Rad57 complex in error-free pathways, we monitored the genetic interactions between Rad55-Rad57, the translesion polymerases Polζ or Polη, and Srs2 following UV radiation that induces mostly single-strand DNA gaps. We found that the Rad55-Rad57 complex was involved in three ways. First, it protects Rad51 filaments from Srs2, as it does at DSBs. Second, it promotes Rad51 filament stability independently of Srs2. Finally, we observed that UV-induced HR is almost abolished in Rad55-Rad57 deficient cells, and is partially restored upon Polζ or Polη depletion. Hence, we propose that the Rad55-Rad57 complex is essential to promote Rad51 filament stability on single-strand DNA gaps, notably to counteract the error-prone TLS polymerases and mutagenesis.
| S-EPMC9937489 | biostudies-literature
Project description:The tumor suppressor BRCA2 plays a key role in initiating homologous recombination by facilitating RAD51 filament formation on single-stranded DNA. The small acidic protein DSS1 is a crucial partner to BRCA2 in this process. In vitro and in cells (1,2), BRCA2 associates into oligomeric complexes besides also existing as monomers. A dimeric structure was further characterized by electron microscopic analysis (3), but the functional significance of the different BRCA2 assemblies remains to be determined. Here, we used biochemistry and electron microscopic imaging to demonstrate that the multimerization of BRCA2 is counteracted by DSS1 and ssDNA. When validating the findings, we identified three self-interacting regions and two types of self-association, the N-to-C terminal and the N-to-N terminal interactions. The N-to-C terminal self-interaction of BRCA2 is sensitive to DSS1 and ssDNA. The N-to-N terminal self-interaction is modulated by ssDNA. Our results define a novel role of DSS1 to regulate BRCA2 in an RPA-independent fashion. Since DSS1 is required for BRCA2 function in recombination, we speculate that the monomeric and oligomeric forms of BRCA2 might be active for different cellular events in recombinational DNA repair and replication fork stabilization.
| S-EPMC7641332 | biostudies-literature
Project description:Repair of DNA double strand breaks by homologous recombination (HR) is initiated by Rad51 filament nucleation on single-stranded DNA (ssDNA), which catalyzes strand exchange with homologous duplex DNA. BRCA2 and the Rad51 paralogs are tumor suppressors and critical mediators of Rad51. To gain insight into Rad51 paralog function, we investigated a heterodimeric Rad51 paralog complex, RFS-1/RIP-1, and uncovered the molecular basis by which Rad51 paralogs promote HR. Unlike BRCA2, which nucleates RAD-51-ssDNA filaments, RFS-1/RIP-1 binds and remodels pre-synaptic filaments to a stabilized, "open," and flexible conformation, in which the ssDNA is more accessible to nuclease digestion and RAD-51 dissociation rate is reduced. Walker box mutations in RFS-1, which abolish filament remodeling, fail to stimulate RAD-51 strand exchange activity, demonstrating that remodeling is essential for RFS-1/RIP-1 function. We propose that Rad51 paralogs stimulate HR by remodeling the Rad51 filament, priming it for strand exchange with the template duplex.
| S-EPMC4518479 | biostudies-literature
Project description:RAD51 DNA strand exchange protein catalyzes the central step in homologous recombination, a cellular process fundamentally important for accurate repair of damaged chromosomes, preservation of the genetic integrity, restart of collapsed replication forks and telomere maintenance. BRCA2 protein, a product of the breast cancer susceptibility gene, is a key recombination mediator that interacts with RAD51 and facilitates RAD51 nucleoprotein filament formation on single-stranded DNA generated at the sites of DNA damage. An accurate atomistic level description of this interaction, however, is limited to a partial crystal structure of the RAD51 core fused to BRC4 peptide. Here, by integrating homology modeling and molecular dynamics, we generated a structure of the full-length RAD51 in complex with BRC4 peptide. Our model predicted previously unknown hydrogen bonding patterns involving the N-terminal domain (NTD) of RAD51. These interactions guide positioning of the BRC4 peptide within a cavity between the core and the NTDs; the peptide binding separates the two domains and restricts internal dynamics of RAD51 protomers. The model's depiction of the RAD51-BRC4 complex was validated by free energy calculations and in vitro functional analysis of rationally designed mutants. All generated mutants, RAD51(E42A), RAD51(E59A), RAD51(E237A), RAD51(E59A/E237A) and RAD51(E42A/E59A/E237A) maintained basic biochemical activities of the wild-type RAD51, but displayed reduced affinities for the BRC4 peptide. Strong correlation between the calculated and experimental binding energies confirmed the predicted structure of the RAD51-BRC4 complex and highlighted the importance of RAD51 NTD in RAD51-BRCA2 interaction.
| S-EPMC3799448 | biostudies-literature