scholarly journals CSIG-19. THE DEUBIQUITINASE BRCC3 LINKS ALT TELOMERES TO SUPPRESSION OF INNATE IMMUNITY IN IDH1-MUTANT GLIOMA

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii31-ii32
Author(s):  
Joydeep Mukherjee ◽  
Yongjian Tang ◽  
Tor-Christian Johanessen ◽  
Ajay Pandita ◽  
Shigeo Ohba ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Lower Grade ◽  
Astrocytoma Cells ◽  
Double Stranded Dna ◽  
Alternative Lengthening ◽  
Lower Grade Glioma ◽  
Exogenous Expression ◽  
Sting Pathway

Abstract Approximately 10% of tumors including all IDH1-mutant lower-grade glioma resolve telomeric shortening using Alternative Lengthening of Telomere (ALT) mechanism. Although the ALT process lengthens telomeres, it also generates small bits of extrachromosomal, telomere-containing DNA (ECTRs). These ECTRs can bind and activate cyclic GMP-AMP synthase (cGAS), the major cytosolic sensor of double-stranded DNA, which in turn can activate expression of stimulator of IFN genes (STING) and the interferon-based innate immune response. To limit the immune response, ALT cells inactivate the cGAS-STING pathway, although the mechanism by which this occurs is unknown. Here we show that the deubiquitinase BRCC3 links ALT telomeres to suppression of the cGAS-STING pathway and the innate immune response. Astrocytoma cells dependent on the ALT-mechanism (IDH1-mutant and ATRX-deficient genetically-modified human astrocytes and MGG119 PDX) contained ECTR and had reduced expression of the cGAS and the downstream components of the cGAS-STING pathway (STING, and IFN-β) relative to matched non-ALT (isogenic ATRX WT astrocytes and MGG152 PDX) cells lacking ECTRs. Decreased levels of cGAS in ALT cells were in turn associated with deubiquitiantion and destabilization of cGAS. The telomere-derived ECTR in ALT-dependent cells lacked two proteins normally found in ALT telomeres (TRF2 or PARP), but retained two other proteins, Mre11 and its binding partner, normally nuclear deubiquitinase BRCC3. Furthermore, either pharmacologic inhibition or genetic suppression of BRCC3 levels had no effect on ECTR levels but stabilized cGAS and activated the cGAS-STING pathway. This cGAS-mediated activation could be blocked by exogenous expression of WT BRCC3, but not by expression of a mutant BRCC3 incapable of deubiquitination. These results show that BRCC3 translocated along with ECTRs to the cytoplasm degrades cGAS and protects ALT-dependent cells from activating the innate immune response. The BRCC3-controlled cGAS-STING pathway may therefore represent a therapeutically targetable means to enhance the immune response in IDH1-mutant lower grade glioma.

scholarly journals Innate immunity mediator STING modulates nascent DNA metabolism at stalled forks in human cells

2021 ◽  
Author(s):  
Vy N. Nguyen ◽  
Salomé Brunon ◽  
Maria N. Pavlova ◽  
Pavlo Lazarchuk ◽  
Roya D. Sharifian ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immunity ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Replication Forks ◽  
Wild Type ◽  
Feedback Connection ◽  
Pathway Activation ◽  
Foreign Dna ◽  
Sting Pathway

The cGAS/STING pathway, part of the innate immune response to foreign DNA, is known to be activated by cell's own DNA arising from the processing of the genome, including the excision of nascent DNA at arrested replication forks. We found STING activation to affect nascent DNA processing, suggesting a novel, unexpected feedback connection between the two events. Depletion of STING suppressed and re-expression of the protein in STING-deficient cells upregulated degradation of nascent DNA. Fork arrest was accompanied by the STING pathway activation, and a STING mutant that does not activate the pathway failed to upregulate nascent strand degradation. Consistent with this, cells expressing the STING mutant had a reduced level of RPA on parental and nascent DNA of arrested forks as well as a reduced CHK1 activation compared to the cells with wild type STING. Together our findings reveal a novel connection between replication stress and innate immunity.

scholarly journals The Role of Transglutaminase in Double-stranded DNA-Triggered Antiviral Innate Immune Response

2011 ◽  
Vol 32 (11) ◽  
pp. 3893-3898
Author(s):  
Jae-Wook Yoo ◽  
Sun-Woo Hong ◽  
Shambhunath Bose ◽  
Ho-Jun Kim ◽  
Soo-Youl Kim ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Innate Immune ◽  
Double Stranded Dna

scholarly journals RNF111-facilitated neddylation potentiates cGAS-mediated antiviral innate immune response

2021 ◽  
Vol 17 (3) ◽  
pp. e1009401
Author(s):  
Chenhui Li ◽  
Lele Zhang ◽  
Dong Qian ◽  
Mingxing Cheng ◽  
Haiyang Hu ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
E3 Ligase ◽  
Vital Role ◽  
Innate Immune ◽  
Type I ◽  
Pathway Activation ◽  
Sting Pathway ◽  
Signaling Activation

The cytosolic DNA sensor cyclic GMP-AMP (cGAMP) synthetase (cGAS) has emerged as a fundamental component fueling the anti-pathogen immunity. Because of its pivotal role in initiating innate immune response, the activity of cGAS must be tightly fine-tuned to maintain immune homeostasis in antiviral response. Here, we reported that neddylation modification was indispensable for appropriate cGAS-STING signaling activation. Blocking neddylation pathway using neddylation inhibitor MLN4924 substantially impaired the induction of type I interferon and proinflammatory cytokines, which was selectively dependent on Nedd8 E2 enzyme Ube2m. We further found that deficiency of the Nedd8 E3 ligase Rnf111 greatly attenuated DNA-triggered cGAS activation while not affecting cGAMP induced activation of STING, demonstrating that Rnf111 was the Nedd8 E3 ligase of cGAS. By performing mass spectrometry, we identified Lys231 and Lys421 as essential neddylation sites in human cGAS. Mechanistically, Rnf111 interacted with and polyneddylated cGAS, which in turn promoted its dimerization and enhanced the DNA-binding ability, leading to proper cGAS-STING pathway activation. In the same line, the Ube2m or Rnf111 deficiency mice exhibited severe defects in innate immune response and were susceptible to HSV-1 infection. Collectively, our study uncovered a vital role of the Ube2m-Rnf111 neddylation axis in promoting the activity of the cGAS-STING pathway and highlighted the importance of neddylation modification in antiviral defense.

scholarly journals DDX41 Recognizes RNA/DNA Retroviral Reverse Transcripts and Is Critical forIn VivoControl of Murine Leukemia Virus Infection

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Spyridon Stavrou ◽  
Alexya N. Aguilera ◽  
Kristin Blouch ◽  
Susan R. Ross
Keyword(s):  
Immune Response ◽  
Immune Responses ◽  
Innate Immune Response ◽  
Reverse Transcription ◽  
Leukemia Virus ◽  
Innate Immune ◽  
Innate Immune Responses ◽  
Retroviral Infection ◽  
Double Stranded Dna

ABSTRACTHost recognition of viral nucleic acids generated during infection leads to the activation of innate immune responses essential for early control of virus. Retrovirus reverse transcription creates numerous potential ligands for cytosolic host sensors that recognize foreign nucleic acids, including single-stranded RNA (ssRNA), RNA/DNA hybrids, and double-stranded DNA (dsDNA). We and others recently showed that the sensors cyclic GMP-AMP synthase (cGAS), DEAD-box helicase 41 (DDX41), and members of the Aim2-like receptor (ALR) family participate in the recognition of retroviral reverse transcripts. However, why multiple sensors might be required and their relative importance inin vivocontrol of retroviral infection are not known. Here, we show that DDX41 primarily senses the DNA/RNA hybrid generated at the first step of reverse transcription, while cGAS recognizes dsDNA generated at the next step. We also show that both DDX41 and cGAS are needed for the antiretroviral innate immune response to murine leukemia virus (MLV) and HIV in primary mouse macrophages and dendritic cells (DCs). Using mice with cell type-specific knockout of theDdx41gene, we show that DDX41 sensing in DCs but not macrophages was critical for controllingin vivoMLV infection. This suggests that DCs are essentialin vivotargets for infection, as well as for initiating the antiviral response. Our work demonstrates that the innate immune response to retrovirus infection depends on multiple host nucleic acid sensors that recognize different reverse transcription intermediates.IMPORTANCEViruses are detected by many different host sensors of nucleic acid, which in turn trigger innate immune responses, such as type I interferon (IFN) production, required to control infection. We show here that at least two sensors are needed to initiate a highly effective innate immune response to retroviruses—DDX41, which preferentially senses the RNA/DNA hybrid generated at the first step of retrovirus replication, and cGAS, which recognizes double-stranded DNA generated at the second step. Importantly, we demonstrate using mice lacking DDX41 or cGAS that both sensors are needed for the full antiviral response needed to controlin vivoMLV infection. These findings underscore the need for multiple host factors to counteract retroviral infection.

scholarly journals The E3 ubiquitin ligase TRIM21 negatively regulates the innate immune response to intracellular double-stranded DNA

2012 ◽  
Vol 14 (2) ◽  
pp. 172-178 ◽  
Author(s):  
Zhiqiang Zhang ◽  
Musheng Bao ◽  
Ning Lu ◽  
Leiyun Weng ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Innate Immune ◽  
Double Stranded Dna

scholarly journals Activation of the Interferon Response by Human Cytomegalovirus Occurs via Cytoplasmic Double-Stranded DNA but Not Glycoprotein B

2010 ◽  
Vol 84 (17) ◽  
pp. 8913-8925 ◽  
Author(s):  
Victor R. DeFilippis ◽  
Tina Sali ◽  
David Alvarado ◽  
Laura White ◽  
Wade Bresnahan ◽  
...  
Keyword(s):  
Immune Response ◽  
Innate Immune Response ◽  
Human Cytomegalovirus ◽  
Sendai Virus ◽  
Fibroblast Cell ◽  
Innate Immune ◽  
Glycoprotein B ◽  
Interferon Response ◽  
Double Stranded Dna

ABSTRACT In vitro infection of cells with the betaherpesvirus human cytomegalovirus (HCMV) stimulates an innate immune response characterized by phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3) and subsequent expression of IRF3-dependent genes. While previous work suggests that HCMV envelope glycoprotein B is responsible for initiating this reaction, the signaling pathways stimulated by virus infection that lead to IRF3 phosphorylation have largely been uncharacterized. Recently, we identified Z DNA binding protein 1 (ZBP1), a sensor of cytoplasmic DNA, as an essential protein for this response. We now describe a human fibroblast cell line exhibiting a recessive defect that results in the absence of activation of IRF3 following treatment with HCMV but not Sendai virus or double-stranded RNA. In addition, we show that while exposure of these cells to soluble HCMV glycoprotein B is capable of triggering IRF3-dependent gene transcription, transfection of the cells with double-stranded DNA is not. Furthermore, we show that overexpression of ZBP1 in these cells reestablishes their ability to secrete interferon in response to HCMV and that multiple ZBP1 transcriptional variants exist in both wild-type and mutant cells. These results have two major implications for the understanding of innate immune stimulation by HCMV. First, they demonstrate that HCMV glycoprotein B is not the essential molecular pattern that induces an IRF3-dependent innate immune response. Second, IRF3-terminal signaling triggered by HCMV particles closely resembles that which is activated by cytoplasmic double-stranded DNA.

scholarly journals Sensing of cytoplasmic chromatin by cGAS activates innate immune response in SARS-CoV-2 infection

2021 ◽  
Author(s):  
Zhuo Zhou ◽  
Xinyi Zhang ◽  
Xiaobo Lei ◽  
Xia Xiao ◽  
Tao Jiao ◽  
...  
Keyword(s):  
Immune Response ◽  
Immune System ◽  
Cell Fusion ◽  
Innate Immune Response ◽  
Rna Virus ◽  
Cellular Level ◽  
Innate Immune ◽  
Host Cells ◽  
Host Immune System ◽  
Sting Pathway

Abstract The global coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a positive-sense RNA virus. How the host immune system senses and responds to SARS-CoV-2 infection remain to be determined. Here, we report that SARS-CoV-2 infection activates the innate immune response through the cytosolic DNA sensing cGAS-STING pathway. SARS-CoV-2 infection induces the cellular level of 2'3'-cGAMP associated with STING activation. cGAS recognizes chromatin DNA shuttled from the nucleus as a result of cell-to-cell fusion upon SARS-CoV-2 infection. We further demonstrate that the expression of spike protein from SARS-CoV-2 and ACE2 from host cells is sufficient to trigger cytoplasmic chromatin upon cell fusion. Furthermore, cytoplasmic chromatin-cGAS-STING pathway, but not MAVS mediated viral RNA sensing pathway, contributes to interferon and pro-inflammatory gene expression upon cell fusion. Finally, we show that cGAS is required for host antiviral responses against SARS-CoV-2, and a STING-activating compound potently inhibits viral replication. Together, our study reported a previously unappreciated mechanism by which the host innate immune system responds to SARS-CoV-2 infection, mediated by cytoplasmic chromatin from the infected cells. Targeting the cytoplasmic chromatin-cGAS-STING pathway may offer novel therapeutic opportunities in treating COVID-19. In addition, these findings extend our knowledge in host defense against viral infection by showing that host cells’ self-nucleic acids can be employed as a “danger signal” to alarm the immune system.

scholarly journals DDX41 recognizes RNA/DNA retroviral reverse transcripts and is critical forin vivocontrol of MLV infection

2018 ◽  
Author(s):  
Spyridon Stavrou ◽  
Alexya Aguilera ◽  
Kristin Blouch ◽  
Susan R. Ross
Keyword(s):  
Immune Response ◽  
Nucleic Acid ◽  
Immune Responses ◽  
Innate Immune Response ◽  
Reverse Transcription ◽  
Innate Immune ◽  
Innate Immune Responses ◽  
Retroviral Infection ◽  
Double Stranded Dna

AbstractHost recognition of viral nucleic acids generated during infection leads to the activation of innate immune responses essential for early control of virus. Retrovirus reverse transcription creates numerous potential ligands for cytosolic host sensors that recognize foreign nucleic acids, including single-stranded RNA (ssRNA), RNA/DNA hybrids and double stranded DNA (dsDNA). We and others recently showed that the sensors cyclic GMP-AMP synthase (cGAS), dead-box helicase 41 (DDX41) and members of the Aim2-like receptor (ALR) family participate in the recognition of retroviral reverse transcripts. However, why multiple sensors might be required and their relative importance inin vivocontrol of retroviral infection is not known. Here we show that DDX41 primarily senses the DNA/RNA hybrid generated at the first step of reverse transcription, while cGAS recognizes dsDNA generated at the next step. We also show that both DDX41 and cGAS are needed for the anti-retroviral innate immune response to MLV and HIV in primary mouse macrophages and dendritic cells (DC). Using mice with macrophage- or -specific knockout of the DDX41 gene, we show that DDX41 sensing in DCs but not macrophages was critical for controllingin vivoMLV infection. This suggests that DCs are essentialin vivotargets for infection, as well as for initiating the antiviral response. Our work demonstrates that the innate immune response to retrovirus infection depends on multiple host nucleic acid sensors that recognize different reverse transcription intermediates.ImportanceViruses are detected by many different host sensors of nucleic acid, which in turn trigger innate immune responses, such as type I IFN production, required to control infection. We show here that at least two sensors are needed to initiate a highly effective innate immune response to retroviruses – DDX41, which preferentially senses the RNA/DNA hybrid generated at the first step of retrovirus replication and cGAS, which recognizes double-stranded DNA generated at the 2ndstep. Importantly, we demonstrate using mice lacking DDX41 or cGAS, that both sensors are needed for the full antiviral response needed to controlin vivoMLV infection. These findings underscore the need for multiple host factors to counteract retroviral infection.

scholarly journals Sensing of cytoplasmic chromatin by cGAS activates innate immune response in SARS-CoV-2 infection

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Zhuo Zhou ◽  
Xinyi Zhang ◽  
Xiaobo Lei ◽  
Xia Xiao ◽  
Tao Jiao ◽  
...  
Keyword(s):  
Immune Response ◽  
Immune System ◽  
Cell Fusion ◽  
Innate Immune Response ◽  
Rna Virus ◽  
Cellular Level ◽  
Innate Immune ◽  
Host Cells ◽  
Host Immune System ◽  
Sting Pathway

AbstractThe global coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a positive-sense RNA virus. How the host immune system senses and responds to SARS-CoV-2 infection remain largely unresolved. Here, we report that SARS-CoV-2 infection activates the innate immune response through the cytosolic DNA sensing cGAS-STING pathway. SARS-CoV-2 infection induces the cellular level of 2′3′-cGAMP associated with STING activation. cGAS recognizes chromatin DNA shuttled from the nucleus as a result of cell-to-cell fusion upon SARS-CoV-2 infection. We further demonstrate that the expression of spike protein from SARS-CoV-2 and ACE2 from host cells is sufficient to trigger cytoplasmic chromatin upon cell fusion. Furthermore, cytoplasmic chromatin-cGAS-STING pathway, but not MAVS-mediated viral RNA sensing pathway, contributes to interferon and pro-inflammatory gene expression upon cell fusion. Finally, we show that cGAS is required for host antiviral responses against SARS-CoV-2, and a STING-activating compound potently inhibits viral replication. Together, our study reported a previously unappreciated mechanism by which the host innate immune system responds to SARS-CoV-2 infection, mediated by cytoplasmic chromatin from the infected cells. Targeting the cytoplasmic chromatin-cGAS-STING pathway may offer novel therapeutic opportunities in treating COVID-19. In addition, these findings extend our knowledge in host defense against viral infection by showing that host cells’ self-nucleic acids can be employed as a “danger signal” to alarm the immune system.

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