scholarly journals RNase H enables efficient repair of R-loop induced DNA damage

2016 ◽  
Author(s):  
Jeremy D. Amon ◽  
Douglas Koshland
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Ribosomal Dna ◽  
Genome Instability ◽  
Rnase H ◽  
Rna Polymerase I ◽  
Chromosomal Dna ◽  
Polymerase I ◽  
Break Induced Replication ◽  
Kinetics Of

AbstractR-loops, three-stranded structures that form when transcripts hybridize to chromosomal DNA, are potent agents of genome instability. This instability has been explained by the ability of R-loops to induce DNA damage. Here, we show that persistent R-loops also compromise DNA repair. Depleting endogenous RNase H activity impairs R-loop removal in budding yeast, causing DNA damage that occurs preferentially in the repetitive ribosomal DNA locus (rDNA). We analyzed the repair kinetics of this damage and identified mutants that modulate repair. Our results indicate that persistent R-loops in the rDNA induce damage that is slowly repaired by break-induced replication (BIR). Furthermore, R-loop induced BIR at the rDNA leads to lethal repair intermediates when RNA polymerase I elongation is compromised. We present a model to explain how removal of R-loops by RNase H is critical in ensuring the efficient repair of R-loop induced DNA damage by pathways other than BIR.

scholarly journals RNase H enables efficient repair of R-loop induced DNA damage

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Jeremy D Amon ◽  
Douglas Koshland
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Dna Repair ◽  
Genome Instability ◽  
Rnase H ◽  
Rna Polymerase I ◽  
Chromosomal Dna ◽  
Polymerase I ◽  
Break Induced Replication ◽  
Kinetics Of

R-loops, three-stranded structures that form when transcripts hybridize to chromosomal DNA, are potent agents of genome instability. This instability has been explained by the ability of R-loops to induce DNA damage. Here, we show that persistent R-loops also compromise DNA repair. Depleting endogenous RNase H activity impairs R-loop removal in Saccharomyces cerevisiae, causing DNA damage that occurs preferentially in the repetitive ribosomal DNA locus (rDNA). We analyzed the repair kinetics of this damage and identified mutants that modulate repair. We present a model that the persistence of R-loops at sites of DNA damage induces repair by break-induced replication (BIR). This R-loop induced BIR is particularly susceptible to the formation of lethal repair intermediates at the rDNA because of a barrier imposed by RNA polymerase I.

scholarly journals β-Actin and Nuclear Myosin I are responsible for nucleolar reorganization during DNA Repair

2019 ◽  
Author(s):  
Elena Cerutti ◽  
Laurianne Daniel ◽  
Lise-Marie Donnio ◽  
Damien Neuillet ◽  
Charlene Magnani ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Rna Polymerase I ◽  
Dna And Rna ◽  
Beta Actin ◽  
Myosin I ◽  
Nuclear Myosin I ◽  
Polymerase I

AbstractDuring DNA Repair, ribosomal DNA and RNA polymerase I (rDNA/RNAP1) are reorganized within the nucleolus. Until now, the proteins and the molecular mechanism governing this reorganisation remained unknown.Here we show that Nuclear Myosin I (NMI) and Nuclear Beta Actin (ACTβ) are essential for the proper reorganisation of the nucleolus, after completion of the DNA Repair reaction.In NMI and ACTβ depleted cells, the rDNA/RNAP1 complex can be displaced at the periphery of the nucleolus after DNA damage but cannot re-enter within the nucleolus after completion of the DNA Repair. Both proteins act concertedly in this process. NMI binds the damaged rDNA at the periphery of the nucleolus, while ACTβ brings the rDNA back within the nucleolus after DNA repair completion. Our results reveal a previously unidentified function for NMI and ACTβ and disclose how these two proteins work in coordination to re-establish the proper rDNA position after DNA repair.

Kinetics of DNA Repair Under Chronic Irradiation at Low and Medium Dose Rates in Repair Proficient and Repair Compromised Normal Fibroblasts

2021 ◽  
Author(s):  
Elena K. Zaharieva ◽  
Megumi Sasatani ◽  
Kenji Kamiya
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dose Rate ◽  
Dose Response ◽  
Chronic Irradiation ◽  
Dose Rates ◽  
Chronic Radiation ◽  
Damage Repair ◽  
Kinetics Of ◽  
Medium Dose

We present time and dose dependencies for the formation of 53BP1 and γH2AX DNA damage repair foci after chronic radiation exposure at dose rates of 140, 250 and 450 mGy/day from 3 to 96 h, in human and mouse repair proficient and ATM or DNA-PK deficient repair compromised cell models. We describe the time/dose-response curves using a mathematical equation which contains a linear component for the induction of DNA damage repair foci after irradiation, and an exponential component for their resolution. We show that under conditions of chronic irradiation at low and medium dose rates, the processes of DNA double-strand breaks (DSBs) induction and repair establish an equilibrium, which in repair proficient cells manifests as a plateau-shaped dose-response where the plateau is reached within the first 24 h postirradiation, and its height is proportionate to the radiation dose rate. In contrast, in repair compromised cells, where the rate of repair may be exceeded by the DSB induction rate, DNA damage accumulates with time of exposure and total absorbed dose. In addition, we discuss the biological meaning of the observed dependencies by presenting the frequency of micronuclei formation under the same irradiation conditions as a marker of radiation-induced genomic instability. We believe that the data and analysis presented here shed light on the kinetics of DNA repair under chronic radiation and are useful for future studies in the low-to-medium dose rate range.

scholarly journals Advances and perspectives of PARP inhibitors

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Ming Yi ◽  
Bing Dong ◽  
Shuang Qin ◽  
Qian Chu ◽  
Kongming Wu ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Cancer Cells ◽  
Genome Instability ◽  
Single Gene ◽  
High Sensitivity ◽  
Lethal Effect ◽  
Single Strand Break ◽  
Synthetic Lethal ◽  
Increased Risk

Abstract DNA damage repair deficiency leads to the increased risk of genome instability and oncogenic transformation. In the meanwhile, this deficiency could be exploited for cancer treatment by inducing excessive genome instability and catastrophic DNA damage. Continuous DNA replication in cancer cells leads to higher demand of DNA repair components. Due to the oncogenic loss of some DNA repair effectors (e.g. BRCA) and incomplete DNA repair repertoire, some cancer cells are addicted to certain DNA repair pathways such as Poly (ADP-ribose) polymerase (PARP)-related single-strand break repair pathway. The interaction between BRCA and PARP is a form of synthetic lethal effect which means the simultaneously functional loss of two genes lead to cell death, while defect in any single gene has a slight effect on cell viability. Based on synthetic lethal theory, Poly (ADP-ribose) polymerase inhibitor (PARPi) was developed aiming to selectively target cancer cells harboring BRCA1/2 mutations. Recently, a growing body of evidence indicated that a broader population of patients could benefit from PARPi therapy far beyond those with germline BRCA1/2 mutated tumors. Numerous biomarkers including homologous recombination deficiency and high level of replication pressure also herald high sensitivity to PARPi treatment. Besides, a series of studies indicated that PARPi-involved combination therapy such as PARPi with additional chemotherapy therapy, immune checkpoint inhibitor, as well as targeted agent had a great advantage in overcoming PARPi resistance and enhancing PARPi efficacy. In this review, we summarized the advances of PARPi in clinical application. Besides, we highlighted multiple promising PARPi-based combination strategies in preclinical and clinical studies.

scholarly journals Deciphering Kinetics of RNA Polymerase I Multi-Nucleotide Transcription

2020 ◽  
Vol 118 (3) ◽  
pp. 543a
Author(s):  
Zachariah Ingram ◽  
David A. Schneider ◽  
Aaron L. Lucius
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Polymerase I ◽  
Kinetics Of

scholarly journals Recent advances in the nucleolar responses to DNA double-strand breaks

2020 ◽  
Vol 48 (17) ◽  
pp. 9449-9461
Author(s):  
Lea Milling Korsholm ◽  
Zita Gál ◽  
Blanca Nieto ◽  
Oliver Quevedo ◽  
Stavroula Boukoura ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Damage Response ◽  
Ribosomal Dna ◽  
Repetitive Sequences ◽  
Dna Lesions ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Damage Response

Abstract DNA damage poses a serious threat to human health and cells therefore continuously monitor and repair DNA lesions across the genome. Ribosomal DNA is a genomic domain that represents a particular challenge due to repetitive sequences, high transcriptional activity and its localization in the nucleolus, where the accessibility of DNA repair factors is limited. Recent discoveries have significantly extended our understanding of how cells respond to DNA double-strand breaks (DSBs) in the nucleolus, and new kinases and multiple down-stream targets have been identified. Restructuring of the nucleolus can occur as a consequence of DSBs and new data point to an active regulation of this process, challenging previous views. Furthermore, new insights into coordination of cell cycle phases and ribosomal DNA repair argue against existing concepts. In addition, the importance of nucleolar-DNA damage response (n-DDR) mechanisms for maintenance of genome stability and the potential of such factors as anti-cancer targets is becoming apparent. This review will provide a detailed discussion of recent findings and their implications for our understanding of the n-DDR. The n-DDR shares features with the DNA damage response (DDR) elsewhere in the genome but is also emerging as an independent response unique to ribosomal DNA and the nucleolus.

Abstract A46: Wnt5a signals through DVL1 to repress ribosomal DNA transcription by RNA polymerase I

2017 ◽  
Author(s):  
Randall Dass ◽  
Aishe Sarshad ◽  
Brittany Carson ◽  
Jennifer Feenstra ◽  
Amanpreet Kaur ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Ribosomal Dna ◽  
Rna Polymerase I ◽  
Dna Transcription ◽  
Polymerase I

scholarly journals Mechanistic insight into the role of Poly(ADP-ribosyl)ation in DNA topology modulation and response to DNA damage

Mutagenesis ◽  
2019 ◽  
Vol 35 (1) ◽  
pp. 107-118
Author(s):  
Bakhyt T Matkarimov ◽  
Dmitry O Zharkov ◽  
Murat K Saparbaev
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Genotoxic Stress ◽  
Strand Break ◽  
Dna Supercoiling ◽  
Dna Strand Breaks ◽  
Chromosomal Dna ◽  
Dna Breaks ◽  
Strand Breaks ◽  
Dna Strand

Abstract Genotoxic stress generates single- and double-strand DNA breaks either through direct damage by reactive oxygen species or as intermediates of DNA repair. Failure to detect and repair DNA strand breaks leads to deleterious consequences such as chromosomal aberrations, genomic instability and cell death. DNA strand breaks disrupt the superhelical state of cellular DNA, which further disturbs the chromatin architecture and gene activity regulation. Proteins from the poly(ADP-ribose) polymerase (PARP) family, such as PARP1 and PARP2, use NAD+ as a substrate to catalyse the synthesis of polymeric chains consisting of ADP-ribose units covalently attached to an acceptor molecule. PARP1 and PARP2 are regarded as DNA damage sensors that, upon activation by strand breaks, poly(ADP-ribosyl)ate themselves and nuclear acceptor proteins. Noteworthy, the regularly branched structure of poly(ADP-ribose) polymer suggests that the mechanism of its synthesis may involve circular movement of PARP1 around the DNA helix, with a branching point in PAR corresponding to one complete 360° turn. We propose that PARP1 stays bound to a DNA strand break end, but rotates around the helix displaced by the growing poly(ADP-ribose) chain, and that this rotation could introduce positive supercoils into damaged chromosomal DNA. This topology modulation would enable nucleosome displacement and chromatin decondensation around the lesion site, facilitating the access of DNA repair proteins or transcription factors. PARP1-mediated DNA supercoiling can be transmitted over long distances, resulting in changes in the high-order chromatin structures. The available structures of PARP1 are consistent with the strand break-induced PAR synthesis as a driving force for PARP1 rotation around the DNA axis.

scholarly journals Physiological Responses of the Hyperthermophilic Archaeon “Pyrococcus abyssi” to DNA Damage Caused by Ionizing Radiation

2003 ◽  
Vol 185 (13) ◽  
pp. 3958-3961 ◽  
Author(s):  
Edmond Jolivet ◽  
Fujihiko Matsunaga ◽  
Yoshizumi Ishino ◽  
Patrick Forterre ◽  
Daniel Prieur ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Ionizing Radiation ◽  
Dna Synthesis ◽  
Gamma Ray ◽  
Pyrococcus Furiosus ◽  
Repair System ◽  
Cell Fractionation ◽  
Chromosomal Dna ◽  
Pyrococcus Abyssi

ABSTRACT The mechanisms by which hyperthermophilic Archaea, such as “Pyrococcus abyssi” and Pyrococcus furiosus, survive high doses of ionizing gamma irradiation are not thoroughly elucidated. Following gamma-ray irradiation at 2,500 Gy, the restoration of “P. abyssi” chromosomes took place within chromosome fragmentation. DNA synthesis in irradiated “P. abyssi” cells during the DNA repair phase was inhibited in comparison to nonirradiated control cultures, suggesting that DNA damage causes a replication block in this organism. We also found evidence for transient export of damaged DNA out of irradiated “P. abyssi” cells prior to a restart of chromosomal DNA synthesis. Our cell fractionation assays further suggest that “P. abyssi” contains a highly efficient DNA repair system which is continuously ready to repair the DNA damage caused by high temperature and/or ionizing radiation.

Sign in / Sign up

Export Citation Format

Share Document