scholarly journals Homologous Recombination Is Necessary for Normal Lymphocyte Development

2008 ◽  
Vol 28 (7) ◽  
pp. 2295-2303 ◽  
Author(s):  
Lura B. Caddle ◽  
Muneer G. Hasham ◽  
William H. Schott ◽  
Bobbi-Jo Shirley ◽  
Kevin D. Mills
Keyword(s):  
Homologous Recombination ◽  
Molecular Model ◽  
Strand Break ◽  
Primary Immunodeficiencies ◽  
Lymphocyte Development ◽  
Normal Lymphocyte ◽  
End Joining ◽  
Dsb Repair ◽  
Lymphoid Development ◽  
Dna Double Strand Break

ABSTRACT Primary immunodeficiencies are rare but serious diseases with diverse genetic causes. Accumulating evidence suggests that defects in DNA double-strand break (DSB) repair can underlie many of these syndromes. In this context, the nonhomologous end joining pathway of DSB repair is absolutely required for lymphoid development, but possible roles for the homologous recombination (HR) pathway have remained more controversial. While recent evidence suggests that HR may indeed be important to suppress lymphoid transformation, the specific relationship of HR to normal lymphocyte development remains unclear. We have investigated roles of the X-ray cross-complementing 2 (Xrcc2) HR gene in lymphocyte development. We show that HR is critical for normal B-cell development, with Xrcc2 nullizygosity leading to p53-dependent early S-phase arrest. In the absence of p53 (encoded by Trp53), Xrcc2-null B cells can fully develop but show high rates of chromosome and chromatid fragmentation. We present a molecular model wherein Xrcc2 is important to preserve or restore replication forks during rapid clonal expansion of developing lymphocytes. Our findings demonstrate a key role for HR in lymphoid development and suggest that Xrcc2 defects could underlie some human primary immunodeficiencies.

scholarly journals The deSUMOylase SENP2 coordinates homologous recombination and non-homologous end joining by independent mechanisms

2018 ◽  
Author(s):  
Alexander J. Garvin ◽  
Alexandra K. Walker ◽  
Ruth M. Densham ◽  
Anoop Singh Chauhan ◽  
Helen R. Stone ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Strand Break ◽  
Double Strand Break ◽  
End Joining ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Non Homologous End Joining

AbstractSUMOylation in the DNA double-strand break (DSB) response regulates recruitment, activity and clearance of repair factors. However, our understanding of a role for deSUMOylation in this process is limited. Here we identify different mechanistic roles for deSUMOylation in homologous recombination (HR) and non-homologous enjoining (NHEJ) through the investigation of the deSUMOylase SENP2. We find regulated deSUMOylation of MDC1 prevents excessive SUMOylation and its RNF4-VCP mediated clearance from DSBs, thereby promoting NHEJ. In contrast we show HR is differentially sensitive to SUMO availability and SENP2 activity is needed to provide SUMO. SENP2 is amplified as part of the chromosome 3q amplification in many cancers. Increased SENP2 expression prolongs MDC1 foci retention and increases NHEJ and radioresistance. Collectively our data reveal that deSUMOylation differentially primes cells for responding to DSBs and demonstrates the ability of SENP2 to tune DSB repair responses.

scholarly journals MicroRNAs down-regulate homologous recombination in the G1 phase of cycling cells to maintain genomic stability

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Young Eun Choi ◽  
Yunfeng Pan ◽  
Eunmi Park ◽  
Panagiotis Konstantinopoulos ◽  
Subhajyoti De ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Strand Break ◽  
G1 Phase ◽  
End Joining ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Dna End Resection ◽  
Non Homologous End Joining ◽  
Brca1 Brca2 ◽  
G1 Cells

Homologous recombination (HR)-mediated repair of DNA double-strand break (DSB)s is restricted to the post-replicative phases of the cell cycle. Initiation of HR in the G1 phase blocks non-homologous end joining (NHEJ) impairing DSB repair. Completion of HR in G1 cells can lead to the loss-of-heterozygosity (LOH), which is potentially carcinogenic. We conducted a gain-of-function screen to identify miRNAs that regulate HR-mediated DSB repair, and of these miRNAs, miR-1255b, miR-148b*, and miR-193b* specifically suppress the HR-pathway in the G1 phase. These miRNAs target the transcripts of HR factors, BRCA1, BRCA2, and RAD51, and inhibiting miR-1255b, miR-148b*, and miR-193b* increases expression of BRCA1/BRCA2/RAD51 specifically in the G1-phase leading to impaired DSB repair. Depletion of CtIP, a BRCA1-associated DNA end resection protein, rescues this phenotype. Furthermore, deletion of miR-1255b, miR-148b*, and miR-193b* in independent cohorts of ovarian tumors correlates with significant increase in LOH events/chromosomal aberrations and BRCA1 expression.

scholarly journals RAD6 Promotes Homologous Recombination Repair by Activating the Autophagy-Mediated Degradation of Heterochromatin Protein HP1

2014 ◽  
Vol 35 (2) ◽  
pp. 406-416 ◽  
Author(s):  
Su Chen ◽  
Chen Wang ◽  
Luxi Sun ◽  
Da-Liang Wang ◽  
Lu Chen ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Genome Stability ◽  
Chromosomal Rearrangements ◽  
Strand Break ◽  
Open Chromatin ◽  
Dsb Repair ◽  
Heterochromatin Protein ◽  
Dna Double Strand Break ◽  
Recombination Repair ◽  
Ubiquitin Conjugating Enzyme

Efficient DNA double-strand break (DSB) repair is critical for the maintenance of genome stability. Unrepaired or misrepaired DSBs cause chromosomal rearrangements that can result in severe consequences, such as tumorigenesis. RAD6 is an E2 ubiquitin-conjugating enzyme that plays a pivotal role in repairing UV-induced DNA damage. Here, we present evidence that RAD6 is also required for DNA DSB repair via homologous recombination (HR) by specifically regulating the degradation of heterochromatin protein 1α (HP1α). Our study indicates that RAD6 physically interacts with HP1α and ubiquitinates HP1α at residue K154, thereby promoting HP1α degradation through the autophagy pathway and eventually leading to an open chromatin structure that facilitates efficient HR DSB repair. Furthermore, bioinformatics studies have indicated that the expression of RAD6 and HP1α exhibits an inverse relationship and correlates with the survival rate of patients.

scholarly journals RAP80 suppresses the vulnerability of R-loops during DNA double-strand break repair

2021 ◽  
Author(s):  
Takaaki Yasuhara ◽  
Reona Kato ◽  
Motohiro Yamauchi ◽  
Yuki Uchihara ◽  
Lee Zou ◽  
...  
Keyword(s):  
Active Regions ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Critical Component ◽  
Dna Double Strand Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Chromosome Translocations ◽  
Dna Double Strand Break

AbstractR-loops, consisting of ssDNA and DNA-RNA hybrids, are potentially vulnerable unless they are appropriately processed. Recent evidence suggests that R-loops can form in the proximity of DNA double-strand breaks (DSBs) within transcriptionally active regions. Yet, how the vulnerability of R-loops is overcome during DSB repair remains unclear. Here, we identify RAP80 as a factor suppressing the vulnerability of ssDNA in R-loops and chromosome translocations and deletions during DSB repair. Mechanistically, RAP80 prevents unscheduled nucleolytic processing of ssDNA in R-loops by CtIP. This mechanism promotes efficient DSB repair via transcription-associated end-joining dependent on BRCA1, Polθ, and LIG1/3. Thus, RAP80 suppresses the vulnerability of R-loops during DSB repair, thereby precluding genomic abnormalities in a critical component of the genome caused by deleterious R-loop processing.

scholarly journals Human SIRT6 Promotes DNA End Resection Through CtIP Deacetylation

Science ◽  
2010 ◽  
Vol 329 (5997) ◽  
pp. 1348-1353 ◽  
Author(s):  
Abderrahmane Kaidi ◽  
Brian T. Weinert ◽  
Chunaram Choudhary ◽  
Stephen P. Jackson
Keyword(s):  
Homologous Recombination ◽  
Genome Stability ◽  
Protein A ◽  
Strand Break ◽  
Dsb Repair ◽  
Interacting Protein ◽  
Dna Double Strand Break ◽  
Dna End Resection ◽  
Lysine Deacetylases ◽  
End Resection

SIRT6 belongs to the sirtuin family of protein lysine deacetylases, which regulate aging and genome stability. We found that human SIRT6 has a role in promoting DNA end resection, a crucial step in DNA double-strand break (DSB) repair by homologous recombination. SIRT6 depletion impaired the accumulation of replication protein A and single-stranded DNA at DNA damage sites, reduced rates of homologous recombination, and sensitized cells to DSB-inducing agents. We identified the DSB resection protein CtIP [C-terminal binding protein (CtBP) interacting protein] as a SIRT6 interaction partner and showed that SIRT6-dependent CtIP deacetylation promotes resection. A nonacetylatable CtIP mutant alleviated the effect of SIRT6 depletion on resection, thus identifying CtIP as a key substrate by which SIRT6 facilitates DSB processing and homologous recombination. These findings further clarify how SIRT6 promotes genome stability.

scholarly journals RecF and RecR Play Critical Roles in the Homologous Recombination and Single-Strand Annealing Pathways of Mycobacteria

2015 ◽  
Vol 197 (19) ◽  
pp. 3121-3132 ◽  
Author(s):  
Richa Gupta ◽  
Stewart Shuman ◽  
Michael S. Glickman
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Strand Break ◽  
Single Strand ◽  
Central Position ◽  
End Joining ◽  
Dna Double Strand Break ◽  
Single Strand Annealing ◽  
Strand Annealing

ABSTRACTMycobacteria encode three DNA double-strand break repair pathways: (i) RecA-dependent homologous recombination (HR), (ii) Ku-dependent nonhomologous end joining (NHEJ), and (iii) RecBCD-dependent single-strand annealing (SSA). Mycobacterial HR has two presynaptic pathway options that rely on the helicase-nuclease AdnAB and the strand annealing protein RecO, respectively. Ablation ofadnABorrecOindividually causes partial impairment of HR, but loss ofadnABandrecOin combination abolishes HR. RecO, which can accelerate annealing of single-stranded DNAin vitro, also participates in the SSA pathway. The functions of RecF and RecR, which, in other model bacteria, function in concert with RecO as mediators of RecA loading, have not been examined in mycobacteria. Here, we present a genetic analysis ofrecFandrecRin mycobacterial recombination. We find that RecF, like RecO, participates in the AdnAB-independent arm of the HR pathway and in SSA. In contrast, RecR is required for all HR in mycobacteria and for SSA. The essentiality of RecR as an agent of HR is yet another distinctive feature of mycobacterial DNA repair.IMPORTANCEThis study clarifies the molecular requirements for homologous recombination in mycobacteria. Specifically, we demonstrate that RecF and RecR play important roles in both the RecA-dependent homologous recombination and RecA-independent single-strand annealing pathways. Coupled with our previous findings (R. Gupta, M. Ryzhikov, O. Koroleva, M. Unciuleac, S. Shuman, S. Korolev, and M. S. Glickman, Nucleic Acids Res 41:2284–2295, 2013,http://dx.doi.org/10.1093/nar/gks1298), these results revise our view of mycobacterial recombination and place the RecFOR system in a central position in homology-dependent DNA repair.

scholarly journals RAD-51-Dependent and -Independent Roles of a Caenorhabditis elegans BRCA2-Related Protein during DNA Double-Strand Break Repair

2005 ◽  
Vol 25 (8) ◽  
pp. 3127-3139 ◽  
Author(s):  
Julie S. Martin ◽  
Nicole Winkelmann ◽  
Mark I. R. Petalcorin ◽  
Michael J. McIlwraith ◽  
Simon J. Boulton
Keyword(s):  
Caenorhabditis Elegans ◽  
Strand Break ◽  
Double Strand Break ◽  
Nonhomologous End Joining ◽  
Related Protein ◽  
End Joining ◽  
Dsb Repair ◽  
Phenotypic Differences ◽  
Dna Double Strand Break ◽  
Radiation Induced

ABSTRACT The BRCA2 tumor suppressor is implicated in DNA double-strand break (DSB) repair by homologous recombination (HR), where it regulates the RAD51 recombinase. We describe a BRCA2-related protein of Caenorhabditis elegans (CeBRC-2) that interacts directly with RAD-51 via a single BRC motif and that binds preferentially to single-stranded DNA through an oligonucleotide-oligosaccharide binding fold. Cebrc-2 mutants fail to repair meiotic or radiation-induced DSBs by HR due to inefficient RAD-51 nuclear localization and a failure to target RAD-51 to sites of DSBs. Genetic and cytological comparisons of Cebrc-2 and rad-51 mutants revealed fundamental phenotypic differences that suggest a role for Cebrc-2 in promoting the use of an alternative repair pathway in the absence of rad-51 and independent of nonhomologous end joining (NHEJ). Unlike rad-51 mutants, Cebrc-2 mutants also accumulate RPA-1 at DSBs, and abnormal chromosome aggregates that arise during the meiotic prophase can be rescued by blocking the NHEJ pathway. CeBRC-2 also forms foci in response to DNA damage and can do so independently of rad-51. Thus, CeBRC-2 not only regulates RAD-51 during HR but can also function independently of rad-51 in DSB repair processes.

scholarly journals Nucleosome disassembly during human non-homologous end joining followed by concerted HIRA- and CAF-1-dependent reassembly

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Xuan Li ◽  
Jessica K Tyler
Keyword(s):  
Strand Break ◽  
End Joining ◽  
Efficient Removal ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Dna End Resection ◽  
Non Homologous End Joining ◽  
Nucleosome Disassembly ◽  
End Resection ◽  
Assembly Pathways

The cell achieves DNA double-strand break (DSB) repair in the context of chromatin structure. However, the mechanisms used to expose DSBs to the repair machinery and to restore the chromatin organization after repair remain elusive. Here we show that induction of a DSB in human cells causes local nucleosome disassembly, apparently independently from DNA end resection. This efficient removal of histone H3 from the genome during non-homologous end joining was promoted by both ATM and the ATP-dependent nucleosome remodeler INO80. Chromatin reassembly during DSB repair was dependent on the HIRA histone chaperone that is specific to the replication-independent histone variant H3.3 and on CAF-1 that is specific to the replication-dependent canonical histones H3.1/H3.2. Our data suggest that the epigenetic information is re-established after DSB repair by the concerted and interdependent action of replication-independent and replication-dependent chromatin assembly pathways.

scholarly journals Homologous recombination defects in Shwachman-Diamond syndrome and Diamond-Blackfan anemia

2020 ◽  
Author(s):  
Elif Asik ◽  
Nimrat Chatterjee ◽  
Alison A. Bertuch
Keyword(s):  
Homologous Recombination ◽  
Ribosome Biogenesis ◽  
Strand Break ◽  
Cancer Predisposition ◽  
Parp Inhibition ◽  
Dsb Repair ◽  
Diamond Blackfan Anemia ◽  
Dna Double Strand Break ◽  
Damage Response ◽  
Shwachman Diamond Syndrome

ABSTRACTShwachman-Diamond syndrome (SDS) and Diamond-Blackfan anemia (DBA) are ribosomopathies characterized by impaired hematopoiesis and cancer predisposition. The mechanisms underlying cancer predisposition in these disorders are not well understood. We found that LCLs derived from patients with SDS or DBA had a prolonged DNA damage response and hypersensitivity to ionizing radiation, suggesting impaired DNA double strand break (DSB) repair. Consistent with this, depletion of SBDS and RPS19, the most common etiologic factors in SDS and DBA, respectively, resulted in reduced homologous recombination (HR) in HCT116 and U2OS cells. Surprisingly, depletion of EFL1, which functions with SBDS in ribosome biogenesis, did not impair HR and depletion of eIF6, which restores ribosome joining in SBDS-depleted cells, did not rescue the HR defect associated with SBDS depletion. Instead, we found SBDS and RPS19 recruitment to sites of DSBs suggesting that SBDS and RPS19 have more proximate roles in regulating HR, independent of their ribosomal functions. We propose that reduced HR shifts DSB repair toward error-prone NHEJ and this may contribute to oncogenesis in SDS and DBA. Additionally, we found SBDS and RPS19 depleted cells were hypersensitive to PARP inhibition, potentially uncovering a therapeutic target for SDS- and DBA-associated malignancies.

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