scholarly journals RAD50 promotes DNA repair by homologous recombination and restrains antigenic variation in African trypanosomes

2020 ◽  
Author(s):  
Ann-Kathrin Mehnert ◽  
Marco Prorocic ◽  
Annick Dujeancourt-Henry ◽  
Sebastian Hutchinson ◽  
Richard McCulloch ◽  
...  
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Antigenic Variation ◽  
Strand Break ◽  
Surface Glycoprotein ◽  
Histone H2a ◽  
African Trypanosomes ◽  
Mrn Complex ◽  
Dna Double Strand Break ◽  
Damage Response

ABSTRACTHomologous recombination dominates as the major form of DNA repair in Trypanosoma brucei, and is especially important for recombination of the subtelomeric variant surface glycoprotein during antigenic variation. RAD50, a component of the MRN complex (MRE11, RAD50, NBS1), is central to homologous recombination through facilitating resection and governing the DNA damage response. The function of RAD50 in trypanosomes is untested. Here we report that RAD50 is required for RAD51-dependent homologous recombination, phosphorylation of histone H2A and controlled resection following a DNA double strand break (DSB). Perhaps surprisingly, DSB resection in the rad50 nulls was not impaired and appeared to peak earlier than in the parental strains. Finally, we show that RAD50 suppresses DNA repair using donors with short stretches of homology at a subtelomeric locus, with null strains producing a greater diversity of expressed VSG variants following DSB repair. We conclude that RAD50 promotes stringent homologous recombination at subtelomeric loci and restrains antigenic variation.

scholarly journals Schizosaccharomyces pombe KAT5 contributes to resection and repair of a DNA double strand break

Genetics ◽  
2021 ◽  
Author(s):  
Tingting Li ◽  
Ruben C Petreaca ◽  
Susan L Forsburg
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Chromatin Remodeling ◽  
Dna Damage Response ◽  
Histone Acetyltransferase ◽  
Strand Break ◽  
Double Strand Break ◽  
Dna Damage Checkpoint ◽  
Dna Double Strand Break ◽  
Damage Response

Abstract Chromatin remodeling is essential for effective repair of a DNA double strand break. KAT5 (S. pombe Mst1, human TIP60) is a MYST family histone acetyltransferase conserved from yeast to humans that coordinates various DNA damage response activities at a DNA double strand break (DSB), including histone remodeling and activation of the DNA damage checkpoint. In S. pombe, mutations in mst1+ causes sensitivity to DNA damaging drugs. Here we show that Mst1 is recruited to DSBs. Mutation of mst1+ disrupts recruitment of repair proteins and delays resection. These defects are partially rescued by deletion of pku70, which has been previously shown to antagonize repair by homologous recombination. These phenotypes of mst1 are similar to pht1-4KR, a non-acetylatable form of histone variant H2A.Z, which has been proposed to affect resection. Our data suggest that Mst1 functions to direct repair of DSBs towards homologous recombination pathways by modulating resection at the double strand break.

scholarly journals Escaping the immune system by DNA repair and recombination in African trypanosomes

Open Biology ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 190182 ◽  
Author(s):  
Núria Sima ◽  
Emilia Jane McLaughlin ◽  
Sebastian Hutchinson ◽  
Lucy Glover
Keyword(s):  
Immune Response ◽  
Dna Repair ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Surface Coat ◽  
African Trypanosomes ◽  
Active Expression ◽  
Expression Site

African trypanosomes escape the mammalian immune response by antigenic variation—the periodic exchange of one surface coat protein, in Trypanosoma brucei the variant surface glycoprotein (VSG), for an immunologically distinct one. VSG transcription is monoallelic, with only one VSG being expressed at a time from a specialized locus, known as an expression site. VSG switching is a predominantly recombination-driven process that allows VSG sequences to be recombined into the active expression site either replacing the currently active VSG or generating a ‘new’ VSG by segmental gene conversion. In this review, we describe what is known about the factors that influence this process, focusing specifically on DNA repair and recombination.

scholarly journals The VEGF receptor neuropilin 2 promotes homologous recombination by stimulating YAP/TAZ-mediated Rad51 expression

2019 ◽  
Vol 116 (28) ◽  
pp. 14174-14180 ◽  
Author(s):  
Ameer L. Elaimy ◽  
John J. Amante ◽  
Lihua Julie Zhu ◽  
Mengdie Wang ◽  
Charlotte S. Walmsley ◽  
...  
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Strand Break ◽  
Vegf Receptor ◽  
Vegf Signaling ◽  
Dna Double Strand Break ◽  
Essential Enzyme ◽  
And Function ◽  
Platinum Chemotherapy ◽  
Endothelial Growth Factor

Vascular endothelial growth factor (VEGF) signaling in tumor cells mediated by neuropilins (NRPs) contributes to the aggressive nature of several cancers, including triple-negative breast cancer (TNBC), independently of its role in angiogenesis. Understanding the mechanisms by which VEGF–NRP signaling contributes to the phenotype of such cancers is a significant and timely problem. We report that VEGF–NRP2 promote homologous recombination (HR) in BRCA1 wild-type TNBC cells by contributing to the expression and function of Rad51, an essential enzyme in the HR pathway that mediates efficient DNA double-strand break repair. Mechanistically, we provide evidence that VEGF–NRP2 stimulates YAP/TAZ-dependent Rad51 expression and that Rad51 is a direct YAP/TAZ–TEAD transcriptional target. We also discovered that VEGF–NRP2–YAP/TAZ signaling contributes to the resistance of TNBC cells to cisplatin and that Rad51 rescues the defects in DNA repair upon inhibition of either VEGF–NRP2 or YAP/TAZ. These findings reveal roles for VEGF–NRP2 and YAP/TAZ in DNA repair, and they indicate a unified mechanism involving VEGF–NRP2, YAP/TAZ, and Rad51 that contributes to resistance to platinum chemotherapy.

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 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 DNA double strand break position leads to distinct gene expression changes and regulates VSG switching pathway choice.

2021 ◽  
Author(s):  
Alix Thivolle ◽  
Ann-Kathrin Mehnert ◽  
Eliane Tihon ◽  
Emilia McLaughlin ◽  
Annick Dujeancourt-Henry ◽  
...  
Keyword(s):  
Gene Expression ◽  
Antigenic Variation ◽  
Surface Protein ◽  
Strand Break ◽  
Surface Glycoprotein ◽  
Dna Double Strand Breaks ◽  
African Trypanosomes ◽  
Distinct Gene ◽  
Active Expression ◽  
Expression Site

Antigenic variation is an immune evasion strategy used by Trypanosoma brucei that results in the periodic exchange of the surface protein coat. Underlying this process is the movement of variant surface glycoprotein genes in or out of a specialized locus known as bloodstream form expression site by homologous recombination, facilitated by blocks of repetitive sequence known as the 70-bp repeats, that provide homology for gene conversion events. DNA double strand breaks are potent drivers of antigenic variation, however where these breaks must fall to elicit a switch is not well understood. To understand how the position of a break influences antigenic variation we established a series of cell lines to study the effect of an I-SceI meganuclease break in the active expression site. We found that a DNA break within repetitive regions is not productive for VSG switching, and show that the break position leads to a distinct gene expression profile and DNA repair response which dictates how antigenic variation proceeds in African trypanosomes.

scholarly journals Fanconi Anemia Protein FANCD2 Promotes Immunoglobulin Gene Conversion and DNA Repair through a Mechanism Related to Homologous Recombination

2005 ◽  
Vol 25 (1) ◽  
pp. 34-43 ◽  
Author(s):  
Kazuhiko Yamamoto ◽  
Seiki Hirano ◽  
Masamichi Ishiai ◽  
Kenichi Morishima ◽  
Hiroyuki Kitao ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Gene Conversion ◽  
Fanconi Anemia ◽  
Strand Break ◽  
Immunoglobulin Gene ◽  
Dna Double Strand Break ◽  
Mutant Cells ◽  
Light Chain Locus

ABSTRACT Recent studies show overlap between Fanconi anemia (FA) proteins and those involved in DNA repair mediated by homologous recombination (HR). However, the mechanism by which FA proteins affect HR is unclear. FA proteins (FancA/C/E/F/G/L) form a multiprotein complex, which is responsible for DNA damage-induced FancD2 monoubiquitination, a key event for cellular resistance to DNA damage. Here, we show that FANCD2-disrupted DT40 chicken B-cell line is defective in HR-mediated DNA double-strand break (DSB) repair, as well as gene conversion at the immunoglobulin light-chain locus, an event also mediated by HR. Gene conversions occurring in mutant cells were associated with decreased nontemplated mutations. In contrast to these defects, we also found increased spontaneous sister chromatid exchange (SCE) and intact Rad51 foci formation after DNA damage. Thus, we propose that FancD2 promotes a subpathway of HR that normally mediates gene conversion by a mechanism that avoids crossing over and hence SCEs.

scholarly journals Exploring the Structures and Functions of Macromolecular SLX4-Nuclease Complexes in Genome Stability

2021 ◽  
Vol 12 ◽  
Author(s):  
Brandon J. Payliss ◽  
Ayushi Patel ◽  
Anneka C. Sheppard ◽  
Haley D. M. Wyatt
Keyword(s):  
Dna Repair ◽  
Homologous Recombination ◽  
Genome Stability ◽  
Genome Instability ◽  
Strand Break ◽  
Biochemical Properties ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
Recent Developments ◽  
And Function

All organisms depend on the ability of cells to accurately duplicate and segregate DNA into progeny. However, DNA is frequently damaged by factors in the environment and from within cells. One of the most dangerous lesions is a DNA double-strand break. Unrepaired breaks are a major driving force for genome instability. Cells contain sophisticated DNA repair networks to counteract the harmful effects of genotoxic agents, thus safeguarding genome integrity. Homologous recombination is a high-fidelity, template-dependent DNA repair pathway essential for the accurate repair of DNA nicks, gaps and double-strand breaks. Accurate homologous recombination depends on the ability of cells to remove branched DNA structures that form during repair, which is achieved through the opposing actions of helicases and structure-selective endonucleases. This review focuses on a structure-selective endonuclease called SLX1-SLX4 and the macromolecular endonuclease complexes that assemble on the SLX4 scaffold. First, we discuss recent developments that illuminate the structure and biochemical properties of this somewhat atypical structure-selective endonuclease. We then summarize the multifaceted roles that are fulfilled by human SLX1-SLX4 and its associated endonucleases in homologous recombination and genome stability. Finally, we discuss recent work on SLX4-binding proteins that may represent integral components of these macromolecular nuclease complexes, emphasizing the structure and function of a protein called SLX4IP.

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