scholarly journals Double Strand Breaks (DSBs) as Indicators of Genomic Instability in PATRR-mediated Translocations

2020 ◽  
Author(s):  
Sarah Correll-Tash ◽  
Brenna Lilley ◽  
I V Harold Salmons ◽  
Elisabeth Mlynarski ◽  
Colleen P Franconi ◽  
...  
Keyword(s):  
Genomic Instability ◽  
Quantitative Polymerase Chain Reaction ◽  
Sister Chromatid Exchanges ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Polymerase Chain ◽  
Elevated Rate ◽  
Chromatid Exchanges ◽  
Initial Results

Abstract Genomic instability contributes to a variety of potentially damaging conditions, including DNA-based rearrangements. Breakage in the form of double strand breaks (DSBs) increases the likelihood of DNA damage, mutations, and translocations. Certain human DNA regions are known to be involved in recurrent translocations, such as the palindrome-mediated rearrangements that have been identified at the breakpoints of several recurrent constitutional translocations: t(11;22)(q23;q11), t(17;22)(q11;q11), and t(8;22) (q24;q11). These breakpoints occur at the center of palindromic AT-rich repeats (PATRRs), which suggests that the structure of the DNA may play a contributory role, potentially through the formation of secondary cruciform structures. The current study analyzed the DSB propensity of these PATRR regions in both lymphoblastoid (mitotic) and spermatogenic cells (meiotic). Initial results found an increased association of sister chromatid exchanges (SCEs) at PATRR regions in experiments that used SCEs to assay DSBs, combining SCE staining with fluorescence in situ hybridization (FISH). Additional experiments used chromatin immunoprecipitation (ChIP) with antibodies for either markers of DSBs or proteins involved in DSB repair along with quantitative polymerase chain reaction (qPCR) to quantify the frequency of DSBs occurring at PATRR regions. The results indicate an increased rate of DSBs at PATRR regions. Additional ChIP experiments with the cruciform binding 2D3 antibody indicate an increased rate of cruciform structures at PATRR regions in both mitotic and meiotic samples. Overall, these experiments demonstrate an elevated rate of DSBs at PATRR regions, an indication that the structure of PATRR containing DNA may lead to increased breakage in multiple cellular environments.

Saccharomyces cerevisiae rad51 Mutants Are Defective in DNA Damage-Associated Sister Chromatid Exchanges but Exhibit Increased Rates of Homology-Directed Translocations

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 959-972
Author(s):  
Michael Fasullo ◽  
Peter Giallanza ◽  
Zheng Dong ◽  
Cinzia Cera ◽  
Thomas Bennett
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Sister Chromatid ◽  
Sister Chromatid Exchanges ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Damaging Agents ◽  
Break Induced Replication ◽  
Chromatid Exchanges

Abstract Saccharomyces cerevisiae Rad51 is structurally similar to Escherichia coli RecA. We investigated the role of S. cerevisiae RAD51 in DNA damage-associated unequal sister chromatid exchanges (SCEs), translocations, and inversions. The frequency of these rearrangements was measured by monitoring mitotic recombination between two his3 fragments, his3-Δ5′ and his3-Δ3′::HOcs, when positioned on different chromosomes or in tandem and oriented in direct or inverted orientation. Recombination was measured after cells were exposed to chemical agents and radiation and after HO endonuclease digestion at his3-Δ3′::HOcs. Wild-type and rad51 mutant strains showed no difference in the rate of spontaneous SCEs; however, the rate of spontaneous inversions was decreased threefold in the rad51 mutant. The rad51 null mutant was defective in DNA damage-associated SCE when cells were exposed to either radiation or chemical DNA-damaging agents or when HO endonuclease-induced double-strand breaks (DSBs) were directly targeted at his3-Δ3′::HOcs. The defect in DNA damage-associated SCEs in rad51 mutants correlated with an eightfold higher spontaneous level of directed translocations in diploid strains and with a higher level of radiation-associated translocations. We suggest that S. cerevisiae RAD51 facilitates genomic stability by reducing nonreciprocal translocations generated by RAD51-independent break-induced replication (BIR) mechanisms.

scholarly journals Human papillomavirus E7 oncoprotein targets RNF168 to hijack the host DNA damage response

2019 ◽  
Vol 116 (39) ◽  
pp. 19552-19562 ◽  
Author(s):  
Justine Sitz ◽  
Sophie Anne Blanchet ◽  
Steven F. Gameiro ◽  
Elise Biquand ◽  
Tia M. Morgan ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Genomic Instability ◽  
E3 Ligase ◽  
Human Papillomaviruses ◽  
Double Strand Breaks ◽  
Nuclear Bodies ◽  
Dna Double Strand Breaks ◽  
Strand Breaks

High-risk human papillomaviruses (HR-HPVs) promote cervical cancer as well as a subset of anogenital and head and neck cancers. Due to their limited coding capacity, HPVs hijack the host cell’s DNA replication and repair machineries to replicate their own genomes. How this host–pathogen interaction contributes to genomic instability is unknown. Here, we report that HPV-infected cancer cells express high levels of RNF168, an E3 ubiquitin ligase that is critical for proper DNA repair following DNA double-strand breaks, and accumulate high numbers of 53BP1 nuclear bodies, a marker of genomic instability induced by replication stress. We describe a mechanism by which HPV E7 subverts the function of RNF168 at DNA double-strand breaks, providing a rationale for increased homology-directed recombination in E6/E7-expressing cervical cancer cells. By targeting a new regulatory domain of RNF168, E7 binds directly to the E3 ligase without affecting its enzymatic activity. As RNF168 knockdown impairs viral genome amplification in differentiated keratinocytes, we propose that E7 hijacks the E3 ligase to promote the viral replicative cycle. This study reveals a mechanism by which tumor viruses reshape the cellular response to DNA damage by manipulating RNF168-dependent ubiquitin signaling. Importantly, our findings reveal a pathway by which HPV may promote the genomic instability that drives oncogenesis.

scholarly journals Targeted-Antibacterial-Plasmids (TAPs) combining conjugation and CRISPR/Cas systems achieve strain-specific antibacterial activity

2020 ◽  
Author(s):  
Audrey Reuter ◽  
Cécile Hilpert ◽  
Annick Dedieu-Berne ◽  
Sophie Lematre ◽  
Erwan Gueguen ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Carbapenem Resistance ◽  
Double Strand Breaks ◽  
Resistant Bacteria ◽  
Innovative Strategy ◽  
Strand Breaks ◽  
Drug Resistant Bacteria

AbstractThe global emergence of drug-resistant bacteria leads to the loss of efficacy of our antibiotics arsenal and severely limits the success of currently available treatments. Here, we developed an innovative strategy based on Targeted-Antibacterial-Plasmids (TAPs) that use bacterial conjugation to deliver CRISPR/Cas systems exerting a strain-specific antibacterial activity. TAPs are highly versatile as they can be directed against any specific genomic or plasmid DNA using the custom algorithm (CSTB) that identifies appropriate targeting spacer sequences. We demonstrate the ability of TAPs to induce strain-selective killing by introducing lethal double strand breaks (DSBs) into the targeted genomes. TAPs directed against a plasmid-born carbapenem resistance gene efficiently resensitise the strain to the drug. This work represents an essential step towards the development of an alternative to antibiotic treatments, which could be used for in situ microbiota modification to eradicate targeted resistant and/or pathogenic bacteria without affecting other non-targeted bacterial species.

scholarly journals Molecular Mechanisms of H. pylori-Induced DNA Double-Strand Breaks

2018 ◽  
Vol 19 (10) ◽  
pp. 2891 ◽  
Author(s):  
Dawit Kidane
Keyword(s):  
Genomic Instability ◽  
Oxidative Dna Damage ◽  
Molecular Mechanisms ◽  
Excision Repair ◽  
Current Knowledge ◽  
Significant Risk ◽  
Significant Risk Factor ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
H Pylori

Infections contribute to carcinogenesis through inflammation-related mechanisms. H. pylori infection is a significant risk factor for gastric carcinogenesis. However, the molecular mechanism by which H. pylori infection contributes to carcinogenesis has not been fully elucidated. H. pylori-associated chronic inflammation is linked to genomic instability via reactive oxygen and nitrogen species (RONS). In this article, we summarize the current knowledge of H. pylori-induced double strand breaks (DSBs). Furthermore, we provide mechanistic insight into how processing of oxidative DNA damage via base excision repair (BER) leads to DSBs. We review recent studies on how H. pylori infection triggers NF-κB/inducible NO synthase (iNOS) versus NF-κB/nucleotide excision repair (NER) axis-mediated DSBs to drive genomic instability. This review discusses current research findings that are related to mechanisms of DSBs and repair during H. pylori infection.

scholarly journals Long Palindromic Sequences Induce Double-Strand Breaks during Meiosis in Yeast

2000 ◽  
Vol 20 (10) ◽  
pp. 3449-3458 ◽  
Author(s):  
Farooq Nasar ◽  
Craig Jankowski ◽  
Dilip K. Nag
Keyword(s):  
Homologous Recombination ◽  
Genomic Instability ◽  
Double Strand Breaks ◽  
Gene Products ◽  
Strand Breaks ◽  
Hairpin Formation ◽  
Palindromic Sequences ◽  
Normal Meiosis ◽  
Eukaryotic Genomes

ABSTRACT Inverted-repeated or palindromic sequences have been found to occur in both prokaryotic and eukaryotic genomes. Such repeated sequences are usually short and present at several functionally important regions in the genome. However, long palindromic sequences are rare and are a major source of genomic instability. The palindrome-mediated genomic instability is believed to be due to cruciform or hairpin formation and subsequent cleavage of this structure by structure-specific nucleases. Here we present both genetic and physical evidence that long palindromic sequences (>50 bp) generate double-strand breaks (DSBs) at a high frequency during meiosis in the yeast Saccharomyces cerevisiae. The palindrome-mediated DSB formation depends on the primary sequence of the inverted repeat and the location and length of the repeated units. The DSB formation at the palindrome requires all of the gene products that are known to be responsible for DSB formation at the normal meiosis-specific sites. Since DSBs are initiators of nearly all meiotic recombination events, most of the palindrome-induced breaks appear to be repaired by homologous recombination. Our results suggest that short palindromic sequences are highly stable in vivo. In contrast, long palindromic sequences make the genome unstable by inducing DSBs and such sequences are usually removed from the genome by homologous recombination events.

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