scholarly journals En Guard! The Interactions between Adenoviruses and the DNA Damage Response

Viruses ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 996 ◽  
Author(s):  
Tamar Kleinberger
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Core Protein ◽  
Large Body ◽  
Mrn Complex ◽  
Downstream Effectors ◽  
Damage Response ◽  
Host Cell Interactions ◽  
Dependent Protein ◽  
Atr Kinases

Virus–host cell interactions include several skirmishes between the virus and its host, and the DNA damage response (DDR) network is one of their important battlegrounds. Although some aspects of the DDR are exploited by adenovirus (Ad) to improve virus replication, especially at the early phase of infection, a large body of evidence demonstrates that Ad devotes many of its proteins, including E1B-55K, E4orf3, E4orf4, E4orf6, and core protein VII, and utilizes varied mechanisms to inhibit the DDR. These findings indicate that the DDR would strongly restrict Ad replication if allowed to function efficiently. Various Ad serotypes inactivate DNA damage sensors, including the Mre11-Rad50-Nbs1 (MRN) complex, DNA-dependent protein kinase (DNA-PK), and Poly (ADP-ribose) polymerase 1 (PARP-1). As a result, these viruses inhibit signaling via DDR transducers, such as the ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, to downstream effectors. The different Ad serotypes utilize both shared and distinct mechanisms to inhibit various branches of the DDR. The aim of this review is to understand the interactions between Ad proteins and the DDR and to appreciate how these interactions contribute to viral replication.

scholarly journals DNA-PKcs: A Multi-Faceted Player in DNA Damage Response

2020 ◽  
Vol 11 ◽  
Author(s):  
Xiaoqiao Yue ◽  
Chenjun Bai ◽  
Dafei Xie ◽  
Teng Ma ◽  
Ping-Kun Zhou
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Cell Cycle Checkpoints ◽  
Dna Double Strand Breaks ◽  
Phosphatidylinositol 3 Kinase ◽  
Strand Breaks ◽  
Damage Response ◽  
Functional Complex ◽  
Dependent Protein ◽  
Cellular Dna

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a member of the phosphatidylinositol 3-kinase related kinase family, which can phosphorylate more than 700 substrates. As the core enzyme, DNA-PKcs forms the active DNA-PK holoenzyme with the Ku80/Ku70 heterodimer to play crucial roles in cellular DNA damage response (DDR). Once DNA double strand breaks (DSBs) occur in the cells, DNA-PKcs is promptly recruited into damage sites and activated. DNA-PKcs is auto-phosphorylated and phosphorylated by Ataxia-Telangiectasia Mutated at multiple sites, and phosphorylates other targets, participating in a series of DDR and repair processes, which determine the cells’ fates: DSBs NHEJ repair and pathway choice, replication stress response, cell cycle checkpoints, telomeres length maintenance, senescence, autophagy, etc. Due to the special and multi-faceted roles of DNA-PKcs in the cellular responses to DNA damage, it is important to precisely regulate the formation and dynamic of its functional complex and activities for guarding genomic stability. On the other hand, targeting DNA-PKcs has been considered as a promising strategy of exploring novel radiosensitizers and killing agents of cancer cells. Combining DNA-PKcs inhibitors with radiotherapy can effectively enhance the efficacy of radiotherapy, offering more possibilities for cancer therapy.

scholarly journals Temporal Regulation of the Mre11-Rad50-Nbs1 Complex during Adenovirus Infection

2009 ◽  
Vol 83 (9) ◽  
pp. 4565-4573 ◽  
Author(s):  
Kasey A. Karen ◽  
Peter J. Hoey ◽  
C. S. H. Young ◽  
Patrick Hearing
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Dna Damage Response ◽  
Adenovirus Infection ◽  
Viral Dna ◽  
Terminal Protein ◽  
Viral Dna Replication ◽  
Mrn Complex ◽  
Viral Dnas ◽  
Damage Response

ABSTRACT Adenovirus infection induces a cellular DNA damage response that can inhibit viral DNA replication and ligate viral genomes into concatemers. It is not clear if the input virus is sufficient to trigger this response or if viral DNA replication is required. Adenovirus has evolved two mechanisms that target the Mre11-Rad50-Nbs1 (MRN) complex to inhibit the DNA damage response. These include E4-ORF3-dependent relocalization of MRN proteins and E4-ORF6/E1B-55K-dependent degradation of MRN components. The literature suggests that degradation of the MRN complex due to E4-ORF6/E1B-55K does not occur until after viral DNA replication has begun. We show that, by the time viral DNA accumulates, the MRN complex is inactivated by either of the E4-induced mechanisms and that, with E4-ORF6/E1B-55K, this inactivation is due to MRN degradation. Our data are consistent with the conclusion that input viral DNA is sufficient to induce the DNA damage response. Further, we demonstrate that when the DNA damage response is active in E4 mutant virus infections, the covalently attached terminal protein is not cleaved from viral DNAs, and the viral origins of replication are not detectably degraded at a time corresponding to the onset of viral replication. The sequences of concatemeric junctions of viral DNAs were determined, which supports the conclusion that nonhomologous end joining mediates viral DNA ligation. Large deletions were found at these junctions, demonstrating nucleolytic procession of the viral DNA; however, the lack of terminal protein cleavage and terminus degradation at earlier times shows that viral genome deletion and concatenation are late effects.

scholarly journals Differential Requirements of the C Terminus of Nbs1 in Suppressing Adenovirus DNA Replication and Promoting Concatemer Formation

2008 ◽  
Vol 82 (17) ◽  
pp. 8362-8372 ◽  
Author(s):  
Seema S. Lakdawala ◽  
Rachel A. Schwartz ◽  
Kevin Ferenchak ◽  
Christian T. Carson ◽  
Brian P. McSharry ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Viral Replication ◽  
Dna Damage Response ◽  
Viral Genomes ◽  
Mrn Complex ◽  
E4 Region ◽  
C Terminus ◽  
Damage Response ◽  
Cellular Dna

ABSTRACT Adenoviruses (Ad) with the early region E4 deleted (E4-deleted virus) are defective for DNA replication and late protein synthesis. Infection with E4-deleted viruses results in activation of a DNA damage response, accumulation of cellular repair factors in foci at viral replication centers, and joining together of viral genomes into concatemers. The cellular DNA repair complex composed of Mre11, Rad50, and Nbs1 (MRN) is required for concatemer formation and full activation of damage signaling through the protein kinases Ataxia-telangiectasia mutated (ATM) and ATM-Rad3-related (ATR). The E4orf3 and E4orf6 proteins expressed from the E4 region of Ad type 5 (Ad5) inactivate the MRN complex by degradation and mislocalization, and prevent the DNA damage response. Here we investigated individual contributions of the MRN complex, concatemer formation, and damage signaling to viral DNA replication during infection with E4-deleted virus. Using virus mutants, short hairpin RNA knockdown and hypomorphic cell lines, we show that inactivation of MRN results in increased viral replication. We demonstrate that defective replication in the absence of E4 is not due to concatemer formation or DNA damage signaling. The C terminus of Nbs1 is required for the inhibition of Ad DNA replication and recruitment of MRN to viral replication centers. We identified regions of Nbs1 that are differentially required for concatemer formation and inhibition of Ad DNA replication. These results demonstrate that targeting of the MRN complex explains the redundant functions of E4orf3 and E4orf6 in promoting Ad DNA replication. Understanding how MRN impacts the adenoviral life cycle will provide insights into the functions of this DNA damage sensor.

scholarly journals ATM Activation and Signaling under Hypoxic Conditions

2008 ◽  
Vol 29 (2) ◽  
pp. 526-537 ◽  
Author(s):  
Zuzana Bencokova ◽  
Muriel R. Kaufmann ◽  
Isabel M. Pires ◽  
Philip S. Lecane ◽  
Amato J. Giaccia ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Hypoxia Inducible Factor ◽  
Dna Breaks ◽  
Focus Formation ◽  
Atm Kinase ◽  
Mrn Complex ◽  
Hypoxic Conditions ◽  
Damage Response ◽  
Dependent Cell

ABSTRACT The ATM kinase has previously been shown to respond to the DNA damage induced by reoxygenation following hypoxia by initiating a Chk 2-dependent cell cycle arrest in the G2 phase. Here we show that ATM is both phosphorylated and active during exposure to hypoxia in the absence of DNA damage, detectable by either comet assay or 53BP1 focus formation. Hypoxia-induced activation of ATM correlates with oxygen concentrations low enough to cause a replication arrest and is entirely independent of hypoxia-inducible factor 1 status. In contrast to damage-activated ATM, hypoxia-activated ATM does not form nuclear foci but is instead diffuse throughout the nucleus. The hypoxia-induced activity of both ATM and the related kinase ATR is independent of NBS1 and MRE11, indicating that the MRN complex does not mediate the DNA damage response to hypoxia. However, the mediator MDC1 is required for efficient activation of Kap1 by hypoxia-induced ATM, indicating that similarly to the DNA damage response, there is a requirement for MDC1 to amplify the ATM response to hypoxia. However, under hypoxic conditions, MDC1 does not recruit BRCA1/53BP1 or RNF8 activity. Our findings clearly demonstrate that there are alternate mechanisms for activating ATM that are both stress-specific and independent of the presence of DNA breaks.

scholarly journals Insight into the Mechanism of Inhibition of Adeno-Associated Virus by the Mre11/Rad50/Nbs1 Complex

2014 ◽  
Vol 89 (1) ◽  
pp. 181-194 ◽  
Author(s):  
Thomas B. Lentz ◽  
R. Jude Samulski
Keyword(s):  
Gene Expression ◽  
Dna Damage ◽  
Dna Synthesis ◽  
Dna Damage Response ◽  
Helper Virus ◽  
Productive Infection ◽  
Adeno Associated Virus ◽  
Mrn Complex ◽  
Mechanism Of Inhibition ◽  
Damage Response

ABSTRACTAdeno-associated virus (AAV) is a dependent virus of the familyParvoviridae. The gene expression and replication of AAV and derived recombinant AAV (rAAV) vectors are severely limited (>10-fold) by the cellular DNA damage-sensing complex made up of Mre11, Rad50, and Nbs1 (MRN). The AAV genome does not encode the means to circumvent this block to productive infection but relies on coinfecting helper virus to do so. Using adenovirus helper proteins E1B55k and E4orf6, which enhance the transduction of AAV via degradation of MRN, we investigated the mechanism through which this DNA damage complex inhibits gene expression from rAAV. We tested the substrate specificity of inhibition and the contribution of different functions of the MRN complex. Our results demonstrate that both single- and double-stranded rAAV vectors are inhibited by MRN, which is in contrast to the predominant model that inhibition is the result of a block to second-strand synthesis. Exploring the contribution of known functions of MRN, we found that inhibition of rAAV does not require downstream DNA damage response factors, including signaling kinases ATM and ATR. The nuclease domain of Mre11 appears to play only a minor role in inhibition, while the DNA binding domain makes a greater contribution. Additionally, mutation of the inverted terminal repeat of the rAAV genome, which has been proposed to be the signal for interaction with MRN, is tolerated by the mechanism of inhibition. These results articulate a model of inhibition of gene expression in which physical interaction is more important than enzymatic activity and several key downstream damage repair factors are dispensable.IMPORTANCEMany viruses modulate the host DNA damage response (DDR) in order to create a cellular environment permissive for infection. The MRN complex is a primary sensor of damage in the cell but also responds to invading viral genomes, often posing a block to infection. AAV is greatly inhibited by MRN and dependent on coinfecting helper virus, such as adenovirus, to remove this factor. Currently, the mechanism through which MRN inhibits AAV and other viruses is poorly understood. Our results reform the predominant model that inhibition of rAAV by MRN is due to limiting second-strand DNA synthesis. Instead, a novel mechanism of inhibition of gene expression independent of a block in rAAV DNA synthesis or downstream damage factors is indicated. These findings have clear implications for understanding this restriction to transduction of AAV and rAAV vectors, which have high therapeutic relevance and likely translate to other viruses that must navigate the DDR.

scholarly journals Nuclear localized Raf1 isoform alters DNA‐dependent protein kinase activity and the DNA damage response

2018 ◽  
Vol 33 (1) ◽  
pp. 1138-1150 ◽  
Author(s):  
Benjamin R. Nixon ◽  
Sara C. Sebag ◽  
Michael S. Glennon ◽  
Eric J. Hall ◽  
Emily S. Kounlavong ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Kinase ◽  
Dna Damage Response ◽  
Kinase Activity ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Damage Response ◽  
Dependent Protein

scholarly journals Analysis of DNA breaks, DNA damage response, and apoptosis produced by high NaCl

2008 ◽  
Vol 295 (6) ◽  
pp. F1678-F1688 ◽  
Author(s):  
Natalia I. Dmitrieva ◽  
Maurice B. Burg
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dna Damage Response ◽  
Hela Cells ◽  
Cell Types ◽  
Dna Breaks ◽  
Main Subject ◽  
Mrn Complex ◽  
Damage Response

We previously reported that, both in cell culture and in the renal inner medulla in vivo, elevating NaCl increased the number of DNA breaks, which persisted as long as NaCl remained high but were rapidly repaired when NaCl was lowered. Furthermore, those breaks did not induce the DNA repair protein γH2AX or cause activation of the MRN (Mre11, Rad50, Nbs1) complex. In contrast, others recently reported that high NaCl does induce γH2AX and MRN complex formation and concluded that these activities are associated with repair of the DNA (Sheen MR, Kim SW, Jung JY, Ahn JY, Rhee JG, Kwon HM, Woo SK. Am J Physiol Renal Physiol 291: F1014–F1020, 2006). The purpose of the present studies was to resolve the disparity. The important difference is that HeLa cells, which were the main subject of the later report, are much less tolerant of high NaCl than are the mIMCD3 cells, which were our main subject. mIMCD3 cells survive levels of NaCl that kill HeLa cells by apoptosis. Here we demonstrate that in both cell types raising NaCl to a level that the cells survive (higher for mIMCD3 than HeLa) increases DNA breaks without inducing γH2AX or activating the MRN complex and that the DNA breaks persist as long as NaCl remains elevated, but are rapidly repaired when it is lowered. Importantly, in both cell types, raising NaCl further to cause apoptosis activates these DNA damage response proteins and greatly fragments DNA, associated with cell death. We conclude that γH2AX induction and MRN activation in response to high NaCl are associated with apoptosis, not DNA repair.

scholarly journals Adenovirus Regulates Sumoylation of Mre11-Rad50-Nbs1 Components through a Paralog-Specific Mechanism

2012 ◽  
Vol 86 (18) ◽  
pp. 9656-9665 ◽  
Author(s):  
Sook-Young Sohn ◽  
Patrick Hearing
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Late Phase ◽  
Cell Nuclei ◽  
Reading Frame ◽  
Orf3 Protein ◽  
Mrn Complex ◽  
Sumo Conjugation ◽  
Damage Response ◽  
Cellular Dna

The Mre11-Rad50-Nbs1 (MRN) complex plays a key role in the DNA damage response, presenting challenges for DNA viruses and retroviruses. To inactivate this complex, adenovirus (Ad) makes use of the E1B-55K and E4-open reading frame 6 (ORF6) proteins for ubiquitin (Ub)-mediated, proteasome-dependent degradation of MRN and the E4-ORF3 protein for relocalization and sequestration of MRN within infected-cell nuclei. Here, we report that Mre11 is modified by the Ub-related modifier SUMO-2 and Nbs1 is modified by both SUMO-1 and SUMO-2. We found that Mre11 and Nbs1 are sumoylated during Ad5 infection and that the E4-ORF3 protein is necessary and sufficient to induce SUMO conjugation. Relocalization of Mre11 and Nbs1 into E4-ORF3 nuclear tracks is required for this modification to occur. E4-ORF3-mediated SUMO-1 conjugation to Nbs1 and SUMO-2 conjugation to Mre11 and Nbs1 are transient during wild-type Ad type 5 (Ad5) infection. In contrast, SUMO-1 conjugation to Nbs1 is stable in cells infected with E1B-55K or E4-ORF6 mutant viruses, suggesting that Ad regulates paralog-specific desumoylation of Nbs1. Inhibition of viral DNA replication blocks deconjugation of SUMO-2 from Mre11 and Nbs1, indicating that a late-phase process is involved in Mre11 and Nbs1 desumoylation. Our results provide direct evidence of Mre11 and Nbs1 sumoylation induced by the Ad5 E4-ORF3 protein and an important example showing that modification of a single substrate by both SUMO-1 and SUMO-2 is regulated through distinct mechanisms. Our findings suggest how E4-ORF3-mediated relocalization of the MRN complex influences the cellular DNA damage response.

scholarly journals HTLV-1 Tax Oncoprotein Subverts the Cellular DNA Damage Response via Binding to DNA-dependent Protein Kinase

2008 ◽  
Vol 283 (52) ◽  
pp. 36311-36320 ◽  
Author(s):  
Sarah S. Durkin ◽  
Xin Guo ◽  
Kimberly A. Fryrear ◽  
Valia T. Mihaylova ◽  
Saurabh K. Gupta ◽  
...  
Keyword(s):  
Dna Damage ◽  
Protein Kinase ◽  
Dna Damage Response ◽  
Dependent Protein Kinase ◽  
Damage Response ◽  
Dependent Protein ◽  
Cellular Dna
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