scholarly journals The Chromatin Response to Double-Strand DNA Breaks and Their Repair

Cells ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1853
Author(s):  
Radoslav Aleksandrov ◽  
Rossitsa Hristova ◽  
Stoyno Stoynov ◽  
Anastas Gospodinov
Keyword(s):  
Dna Repair ◽  
Cancer Progression ◽  
Repair Process ◽  
Dna Breaks ◽  
Dsb Repair ◽  
Double Strand Dna Breaks ◽  
Dna Repair Proteins ◽  
Dna Strands ◽  
Cellular Dna ◽  
Double Strand Dna

Cellular DNA is constantly being damaged by numerous internal and external mutagenic factors. Probably the most severe type of insults DNA could suffer are the double-strand DNA breaks (DSBs). They sever both DNA strands and compromise genomic stability, causing deleterious chromosomal aberrations that are implicated in numerous maladies, including cancer. Not surprisingly, cells have evolved several DSB repair pathways encompassing hundreds of different DNA repair proteins to cope with this challenge. In eukaryotic cells, DSB repair is fulfilled in the immensely complex environment of the chromatin. The chromatin is not just a passive background that accommodates the multitude of DNA repair proteins, but it is a highly dynamic and active participant in the repair process. Chromatin alterations, such as changing patterns of histone modifications shaped by numerous histone-modifying enzymes and chromatin remodeling, are pivotal for proficient DSB repair. Dynamic chromatin changes ensure accessibility to the damaged region, recruit DNA repair proteins, and regulate their association and activity, contributing to DSB repair pathway choice and coordination. Given the paramount importance of DSB repair in tumorigenesis and cancer progression, DSB repair has turned into an attractive target for the development of novel anticancer therapies, some of which have already entered the clinic.

scholarly journals TLP-mediated global transcriptional repression after double-strand DNA breaks slows down DNA repair and induces apoptosis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hidefumi Suzuki ◽  
Mayumi Okamoto-Katsuyama ◽  
Tetsufumi Suwa ◽  
Ryo Maeda ◽  
Taka-aki Tamura ◽  
...  
Keyword(s):  
Dna Repair ◽  
Transcriptional Repression ◽  
Dna Breaks ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

scholarly journals Global detection of DNA repair outcomes induced by CRISPR-Cas9

2021 ◽  
Author(s):  
Mengzhu Liu ◽  
Weiwei Zhang ◽  
Changchang Xin ◽  
Jianhang Yin ◽  
Yafang Shang ◽  
...  
Keyword(s):  
Dna Repair ◽  
Genome Editing ◽  
Target Genes ◽  
Chromosomal Translocations ◽  
Dna Breaks ◽  
Dsb Repair ◽  
Large Deletions ◽  
Mouse Cells ◽  
Repair Pathways ◽  
Cellular Dna

AbstractCRISPR-Cas9 generates double-stranded DNA breaks (DSBs) to activate cellular DNA repair pathways for genome editing. The repair of DSBs leads to small insertions or deletions (indels) and other complex byproducts, including large deletions and chromosomal translocations. Indels are well understood to disrupt target genes, while the other deleterious byproducts remain elusive. We developed a new in silico analysis pipeline for the previously described primer-extension-mediated sequencing assay to comprehensively characterize CRISPR-Cas9-induced DSB repair outcomes in human or mouse cells. We identified tremendous deleterious DSB repair byproducts of CRISPR-Cas9 editing, including large deletions, plasmid integrations, and chromosomal translocations. We further elucidated the important roles of microhomology, chromosomal interaction, recurrent DSBs, and DSB repair pathways in the generation of these byproducts. Our findings provide an extra dimension for genome editing safety besides off-targets. And caution should be exercised to avoid not only off-target damages but also deleterious DSB repair byproducts during genome editing.

scholarly journals Quantitative analysis shows that repair of Cas9-induced double-strand DNA breaks is slow and error-prone

2017 ◽  
Author(s):  
Eva K. Brinkman ◽  
Tao Chen ◽  
Marcel de Haas ◽  
Hanna A. Holland ◽  
Waseem Akhtar ◽  
...  
Keyword(s):  
Repair Process ◽  
Strand Break ◽  
Double Strand Break ◽  
Dna Breaks ◽  
End Joining ◽  
Dsb Repair ◽  
Double Strand Dna Breaks ◽  
Chemical Inhibition ◽  
Changes Over Time ◽  
Kinetics Of

SummaryThe RNA-guided DNA endonuclease Cas9 is a powerful tool for genome editing. Little is known about the kinetics and fidelity of the double-strand break (DSB) repair process that follows a Cas9 cutting event in living cells. Here, we developed a strategy to measure the kinetics of DSB repair for single loci in human cells. Quantitative modeling of repaired DNA in time series after Cas9 activation reveals a relatively slow repair rate (~6h). Furthermore, the double strand break is predominantly repaired in an error-prone fashion (at least 70%). Both classical and microhomology-mediated end-joining pathways are active and contribute to the repair in a stochastic manner. However, the balance between these two pathways changes over time and can be altered by chemical inhibition of DNAPKcs or additional ionizing radiation. Our strategy is generally applicable to study DSB repair kinetics and fidelity in single loci, and demonstrates that Cas9-induced DSBs are repaired in an unusual manner.

scholarly journals Fine-Structure Mapping of Meiosis-Specific Double-Strand DNA Breaks at a Recombination Hotspot Associated With an Insertion of Telomeric Sequences Upstream of the HIS4 Locus in Yeast

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1115-1125 ◽  
Author(s):  
Fei Xu ◽  
Thomas D Petes
Keyword(s):  
Meiotic Recombination ◽  
Hydroxyl Groups ◽  
Sequence Specificity ◽  
Structure Mapping ◽  
Dna Breaks ◽  
Exonuclease Iii ◽  
Recombination Hotspot ◽  
Telomeric Sequences ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Abstract Meiotic recombination in Saccharomyces cerevisiae is initiated by double-strand DNA breaks (DSBs). Using two approaches, we mapped the position of DSBs associated with a recombination hotspot created by insertion of telomeric sequences into the region upstream of HIS4. We found that the breaks have no obvious sequence specificity and localize to a region of ~50 bp adjacent to the telomeric insertion. By mapping the breaks and by studies of the exonuclease III sensitivity of the broken ends, we conclude that most of the broken DNA molecules have blunt ends with 3′-hydroxyl groups.

Expression of double strand DNA breaks repair genes in pterygium

2010 ◽  
Vol 32 (1) ◽  
pp. 39-47 ◽  
Author(s):  
Anna Łękawa–Ilczuk ◽  
Halina Antosz ◽  
Beata Rymgayłło–Jankowska ◽  
Tomasz Żarnowski
Keyword(s):  
Dna Breaks ◽  
Double Strand Dna Breaks ◽  
Repair Genes ◽  
Double Strand Dna

Inside Back Cover: Double-Strand DNA Breaks Induced by Paracyclophane Gold(I) Complexes (Chem. Eur. J. 26/2017)

2017 ◽  
Vol 23 (26) ◽  
pp. 6459-6459
Author(s):  
Sebastian Bestgen ◽  
Carmen Seidl ◽  
Thomas Wiesner ◽  
Andreas Zimmer ◽  
Martina Falk ◽  
...  
Keyword(s):  
Dna Breaks ◽  
Back Cover ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Roles of Caenorhabditis elegans WRN Helicase in DNA Damage Responses, and a Comparison with Its Mammalian Homolog: A Mini-Review

Gerontology ◽  
2015 ◽  
Vol 62 (3) ◽  
pp. 296-303 ◽  
Author(s):  
Jin-Sun Ryu ◽  
Hyeon-Sook Koo
Keyword(s):  
Dna Damage ◽  
Caenorhabditis Elegans ◽  
Werner Syndrome ◽  
Model Organisms ◽  
Current Status ◽  
Helicase Domain ◽  
Replication Forks ◽  
Dna Breaks ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Werner syndrome protein (WRN) is unusual among RecQ family DNA helicases in having an additional exonuclease activity. WRN is involved in the repair of double-strand DNA breaks via the homologous recombination and nonhomologous end joining pathways, and also in the base excision repair pathway. In addition, the protein promotes the recovery of stalled replication forks. The helicase activity is thought to unwind DNA duplexes, thereby moving replication forks or Holliday junctions. The targets of the exonuclease could be the nascent DNA strands at a replication fork or the ends of double-strand DNA breaks. However, it is not clear which enzyme activities are essential for repairing different types of DNA damage. Model organisms such as mice, flies, and worms deficient in WRN homologs have been investigated to understand the physiological results of defects in WRN activity. Premature aging, the most remarkable characteristic of Werner syndrome, is also seen in the mutant mice and worms, and hypersensitivity to DNA damage has been observed in WRN mutants of all three model organisms, pointing to conservation of the functions of WRN. In the nematode Caenorhabditis elegans, the WRN homolog contains a helicase domain but no exonuclease domain, so that this animal is very useful for studying the in vivo functions of the helicase without interference from the activity of the exonuclease. Here, we review the current status of investigations of C. elegans WRN-1 and discuss its functional differences from the mammalian homologs.

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