scholarly journals Homologous Recombination Subpathways: A Tangle to Resolve

2021 ◽  
Vol 12 ◽  
Author(s):  
Amira Elbakry ◽  
Markus Löbrich
Keyword(s):  
Homologous Recombination ◽  
Cell Types ◽  
Strand Break ◽  
Human Cells ◽  
Dsb Repair ◽  
New Developments ◽  
Alternative Models ◽  
Dna Double Strand Break ◽  
Different Cell Types ◽  
The Impact

Homologous recombination (HR) is an essential pathway for DNA double-strand break (DSB) repair, which can proceed through various subpathways that have distinct elements and genetic outcomes. In this mini-review, we highlight the main features known about HR subpathways operating at DSBs in human cells and the factors regulating subpathway choice. We examine new developments that provide alternative models of subpathway usage in different cell types revise the nature of HR intermediates involved and reassess the frequency of repair outcomes. We discuss the impact of expanding our understanding of HR subpathways and how it can be clinically exploited.

scholarly journals The Over-expression of the β2 Catalytic Subunit of the Proteasome Decreases Homologous Recombination and Impairs DNA Double-Strand Break Repair in Human Cells

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Anita Collavoli ◽  
Laura Comelli ◽  
Tiziana Cervelli ◽  
Alvaro Galli
Keyword(s):  
Homologous Recombination ◽  
Active Role ◽  
Strand Break ◽  
Double Strand Break ◽  
Human Cells ◽  
Proteasome Activity ◽  
Dsb Repair ◽  
Catalytic Subunits ◽  
Over Expression ◽  
Dna Double Strand Break

By a human cDNA library screening, we have previously identified two sequences coding two different catalytic subunits of the proteasome which increase homologous recombination (HR) when overexpressed in the yeastSaccharomyces cerevisiae. Here, we investigated the effect of proteasome on spontaneous HR and DNA repair in human cells. To determine if the proteasome has a role in the occurrence of spontaneous HR in human cells, we overexpressed the β2 subunit of the proteasome in HeLa cells and determined the effect on intrachromosomal HR. Results showed that the overexpression of β2 subunit decreased HR in human cells without altering the cell proteasome activity and the Rad51p level. Moreover, exposure to MG132 that inhibits the proteasome activity reduced HR in human cells. We also found that the expression of the β2 subunit increases the sensitivity to the camptothecin that induces DNA double-strand break (DSB). This suggests that the β2 subunit has an active role in HR and DSB repair but does not alter the intracellular level of the Rad51p.

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 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 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.

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.

Impact of chromatin context on Cas9-induced DNA double-strand break repair pathway balance

2020 ◽  
Author(s):  
Ruben Schep ◽  
Eva K. Brinkman ◽  
Christ Leemans ◽  
Xabier Vergara ◽  
Ben Morris ◽  
...  
Keyword(s):  
Genome Editing ◽  
Strand Break ◽  
Double Strand Break ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Repair Pathways ◽  
Non Homologous End Joining ◽  
The Impact

AbstractDNA double-strand break (DSB) repair is mediated by multiple pathways, including classical non-homologous end-joining pathway (NHEJ) and several homology-driven repair pathways. This is particularly important for Cas9-mediated genome editing, where the outcome critically depends on the pathway that repairs the break. It is thought that the local chromatin context affects the pathway choice, but the underlying principles are poorly understood. Using a newly developed multiplexed reporter assay in combination with Cas9 cutting, we systematically measured the relative activities of three DSB repair pathways as function of chromatin context in >1,000 genomic locations. This revealed that NHEJ is broadly biased towards euchromatin, while microhomology-mediated end-joining (MMEJ) is more efficient in specific heterochromatin contexts. In H3K27me3-marked heterochromatin, inhibition of the H3K27 methyltransferase EZH2 shifts the balance towards NHEJ. Single-strand templated repair (SSTR), often used for precise CRISPR editing, competes with MMEJ, and this competition is weakly associated with chromatin context. These results provide insight into the impact of chromatin on DSB repair pathway balance, and guidance for the design of Cas9-mediated genome editing experiments.

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 Live imaging of induced and controlled DNA double-strand break formation reveals extremely low repair by homologous recombination in human cells

Oncogene ◽  
2011 ◽  
Vol 31 (30) ◽  
pp. 3495-3504 ◽  
Author(s):  
O D Shahar ◽  
E V S Raghu Ram ◽  
E Shimshoni ◽  
S Hareli ◽  
E Meshorer ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Strand Break ◽  
Live Imaging ◽  
Double Strand Break ◽  
Human Cells ◽  
Dna Double Strand Break ◽  
Break Formation

scholarly journals NMDA Receptor-Mediated Signaling Pathways Enhance Radiation Resistance, Survival and Migration in Glioblastoma Cells—A Potential Target for Adjuvant Radiotherapy

Cancers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 503 ◽  
Author(s):  
Müller-Längle ◽  
Lutz ◽  
Hehlgans ◽  
Rödel ◽  
Rau ◽  
...  
Keyword(s):  
Functional Expression ◽  
Strand Break ◽  
Therapeutic Interventions ◽  
Ionotropic Glutamate Receptors ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Glutamatergic Signaling ◽  
And Migration ◽  
The Impact ◽  
The Brain

Glioblastoma is one of the most aggressive malignant brain tumors, with a survival time less than 15 months and characterized by a high radioresistance and the property of infiltrating the brain. Recent data indicate that the malignancy of glioblastomas depends on glutamatergic signaling via ionotropic glutamate receptors. In this study we revealed functional expression of Ca2+-permeable NMDARs in three glioblastoma cell lines. Therefore, we investigated the impact of this receptor on cell survival, migration and DNA double-strand break (DSB) repair in the presence of both, glutamate and NMDAR antagonists, and after clinically relevant doses of ionizing radiation. Our results indicate that treatment with NMDAR antagonists slowed the growth and migration of glutamate-releasing LN229 cells, suggesting that activation of NMDARs facilitate tumor expansion. Furthermore, we found that DSB-repair upon radiation was more effective in the presence of glutamate. In contrast, antagonizing the NMDAR or the Ca2+-dependent transcription factor CREB impaired DSB-repair similarly and resulted in a radiosensitizing effect in LN229 and U-87MG cells, indicating a common link between NMDAR signaling and CREB activity in glioblastoma. Since the FDA-approved NMDAR antagonists memantine and ifenprodil showed differential radiosensitizing effects, these compounds may constitute novel optimizations for therapeutic interventions in glioblastoma.

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