scholarly journals Mre11 exonuclease activity removes the chain-terminating nucleoside analog gemcitabine from the nascent strand during DNA replication

2020 ◽  
Vol 6 (22) ◽  
pp. eaaz4126 ◽  
Author(s):  
L. Boeckemeier ◽  
R. Kraehenbuehl ◽  
A. Keszthelyi ◽  
M. U. Gasasira ◽  
E. G. Vernon ◽  
...  
Keyword(s):  
Strand Break ◽  
Nucleoside Analog ◽  
Exonuclease Activity ◽  
Aberrant Expression ◽  
Gemcitabine Resistance ◽  
Dna Double Strand Break ◽  
A Cell ◽  
Chain Terminator ◽  
Made In

The Mre11 nuclease is involved in early responses to DNA damage, often mediated by its role in DNA end processing. MRE11 mutations and aberrant expression are associated with carcinogenesis and cancer treatment outcomes. While, in recent years, progress has been made in understanding the role of Mre11 nuclease activities in DNA double-strand break repair, their role during replication has remained elusive. The nucleoside analog gemcitabine, widely used in cancer therapy, acts as a replication chain terminator; for a cell to survive treatment, gemcitabine needs to be removed from replicating DNA. Activities responsible for this removal have, so far, not been identified. We show that Mre11 3′ to 5′ exonuclease activity removes gemcitabine from nascent DNA during replication. This contributes to replication progression and gemcitabine resistance. We thus uncovered a replication-supporting role for Mre11 exonuclease activity, which is distinct from its previously reported detrimental role in uncontrolled resection in recombination-deficient cells.

scholarly journals Repair Kinetics of Genomic Interstrand DNA Cross-Links: Evidence for DNA Double-Strand Break-Dependent Activation of the Fanconi Anemia/BRCA Pathway

2004 ◽  
Vol 24 (1) ◽  
pp. 123-134 ◽  
Author(s):  
Andreas Rothfuss ◽  
Markus Grompe
Keyword(s):  
Fanconi Anemia ◽  
Strand Break ◽  
S Phase ◽  
Dna Double Strand Breaks ◽  
Subsequent Formation ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
Cross Links ◽  
Kinetics Of

ABSTRACT The detailed mechanisms of DNA interstrand cross-link (ICL) repair and the involvement of the Fanconi anemia (FA)/BRCA pathway in this process are not known. Present models suggest that recognition and repair of ICL in human cells occur primarily during the S phase. Here we provide evidence for a refined model in which ICLs are recognized and are rapidly incised by ERCC1/XPF independent of DNA replication. However, the incised ICLs are then processed further and DNA double-strand breaks (DSB) form exclusively in the S phase. FA cells are fully proficient in the sensing and incision of ICL as well as in the subsequent formation of DSB, suggesting a role of the FA/BRCA pathway downstream in ICL repair. In fact, activation of FANCD2 occurs slowly after ICL treatment and correlates with the appearance of DSB in the S phase. In contrast, activation is rapid after ionizing radiation, indicating that the FA/BRCA pathway is specifically activated upon DSB formation. Furthermore, the formation of FANCD2 foci is restricted to a subpopulation of cells, which can be labeled by bromodeoxyuridine incorporation. We therefore conclude that the FA/BRCA pathway, while being dispensable for the early events in ICL repair, is activated in S-phase cells after DSB have formed.

scholarly journals DNA double-strand break repair: a theoretical framework and its application

2016 ◽  
Vol 13 (114) ◽  
pp. 20150679 ◽  
Author(s):  
Philip J. Murray ◽  
Bart Cornelissen ◽  
Katherine A. Vallis ◽  
S. Jon Chapman
Keyword(s):  
Dna Damage ◽  
Auger Electron ◽  
Strand Break ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Histone H2ax ◽  
Dna Double Strand Break ◽  
A Cell

DNA double-strand breaks (DSBs) are formed as a result of genotoxic insults, such as exogenous ionizing radiation, and are among the most serious types of DNA damage. One of the earliest molecular responses following DSB formation is the phosphorylation of the histone H2AX, giving rise to γ H2AX. Many copies of γ H2AX are generated at DSBs and can be detected in vitro as foci using well-established immuno-histochemical methods. It has previously been shown that anti- γ H2AX antibodies, modified by the addition of the cell-penetrating peptide TAT and a fluorescent or radionuclide label, can be used to visualize and quantify DSBs in vivo . Moreover, when labelled with a high amount of the short-range, Auger electron-emitting radioisotope, 111 In, the amount of DNA damage within a cell can be increased, leading to cell death. In this report, we develop a mathematical model that describes how molecular processes at individual sites of DNA damage give rise to quantifiable foci. Equations that describe stochastic mean behaviours at individual DSB sites are derived and parametrized using population-scale, time-series measurements from two different cancer cell lines. The model is used to examine two case studies in which the introduction of an antibody (anti- γ H2AX-TAT) that targets a key component in the DSB repair pathway influences system behaviour. We investigate: (i) how the interaction between anti- γ H2AX-TAT and γ H2AX effects the kinetics of H2AX phosphorylation and DSB repair and (ii) model behaviour when the anti- γ H2AX antibody is labelled with Auger electron-emitting 111 In and can thus instigate additional DNA damage. This work supports the conclusion that DSB kinetics are largely unaffected by the introduction of the anti- γ H2AX antibody, a result that has been validated experimentally, and hence the hypothesis that the use of anti- γ H2AX antibody to quantify DSBs does not violate the image tracer principle. Moreover, it provides a novel model of DNA damage accumulation in the presence of Auger electron-emitting 111 In that is supported qualitatively by the available experimental data.

scholarly journals The balancing act of R-loop biology: The good, the bad, and the ugly

2019 ◽  
Vol 295 (4) ◽  
pp. 905-913 ◽  
Author(s):  
Youssef A. Hegazy ◽  
Chrishan M. Fernando ◽  
Elizabeth J. Tran
Keyword(s):  
Genome Instability ◽  
Strand Break ◽  
Biological Processes ◽  
Physiological Importance ◽  
Future Goals ◽  
Dna Double Strand Break ◽  
Positive Functions ◽  
Acid Structure

An R-loop is a three-stranded nucleic acid structure that consists of a DNA:RNA hybrid and a displaced strand of DNA. R-loops occur frequently in genomes and have significant physiological importance. They play vital roles in regulating gene expression, DNA replication, and DNA and histone modifications. Several studies have uncovered that R-loops contribute to fundamental biological processes in various organisms. Paradoxically, although they do play essential positive functions required for important biological processes, they can also contribute to DNA damage and genome instability. Recent evidence suggests that R-loops are involved in a number of human diseases, including neurological disorders, cancer, and autoimmune diseases. This review focuses on the molecular basis for R-loop–mediated gene regulation and genomic instability and briefly discusses methods for identifying R-loops in vivo. It also highlights recent studies indicating the role of R-loops in DNA double-strand break repair with an updated view of much-needed future goals in R-loop biology.

scholarly journals Role of DNA Double-strand Break Repair Genes in Cell Proliferation under Low Dose-rate Irradiation Conditions

2008 ◽  
Vol 49 (5) ◽  
pp. 557-564 ◽  
Author(s):  
Masanori TOMITA ◽  
Fumiko MOROHOSHI ◽  
Yoshihisa MATSUMOTO ◽  
Kensuke OTSUKA ◽  
Kazuo SAKAI
Keyword(s):  
Cell Proliferation ◽  
Dose Rate ◽  
Low Dose ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
Low Dose Rate ◽  
Dna Double Strand Break ◽  
Repair Genes

scholarly journals Role of 53BP1 in the Regulation of DNA Double-Strand Break Repair Pathway Choice

2014 ◽  
Vol 181 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Arun Gupta ◽  
Clayton R. Hunt ◽  
Sharmistha Chakraborty ◽  
Raj K. Pandita ◽  
John Yordy ◽  
...  
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
Repair Pathway ◽  
Dna Double Strand Break ◽  
Pathway Choice ◽  
Break Repair

DNA double-strand break repair within heterochromatic regions

2012 ◽  
Vol 40 (1) ◽  
pp. 173-178 ◽  
Author(s):  
Johanne M. Murray ◽  
Tom Stiff ◽  
Penny A. Jeggo
Keyword(s):  
Chromatin Structure ◽  
Mammalian Cells ◽  
Strand Break ◽  
Higher Order ◽  
End Joining ◽  
Strand Breaks ◽  
Dna Double Strand Break ◽  
Dna Dsbs ◽  
A Cell ◽  
Non Homologous End Joining

DNA DSBs (double-strand breaks) represent a critical lesion for a cell, with misrepair being potentially as harmful as lack of repair. In mammalian cells, DSBs are predominantly repaired by non-homologous end-joining or homologous recombination. The kinetics of repair of DSBs can differ widely, and recent studies have shown that the higher-order chromatin structure can dramatically affect the pathway utilized, the rate of repair and the genetic factors required for repair. Studies of the repair of DSBs arising within heterochromatic DNA regions have provided insight into the constraints that higher-order chromatin structure poses on repair and the processing that is uniquely required for the repair of such DSBs. In the present paper, we provide an overview of our current understanding of the process of heterochromatic DSB repair in mammalian cells and consider the evolutionary conservation of the processes.

scholarly journals Tumor Cell Kill by c-MYC Depletion: Role of MYC-Regulated Genes that Control DNA Double-Strand Break Repair

2010 ◽  
Vol 70 (21) ◽  
pp. 8748-8759 ◽  
Author(s):  
Kaisa R. Luoto ◽  
Alice X. Meng ◽  
Amanda R. Wasylishen ◽  
Helen Zhao ◽  
Carla L. Coackley ◽  
...  
Keyword(s):  
Tumor Cell ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
Dna Double Strand Break ◽  
Cell Kill ◽  
Break Repair
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