Project description:RNAseq analysis of cell lines with ADAR1-p150 and ADAR1-p110 knock-outs and primary human tissue samples (from GSE57353 and GSE99392 data sets) to identify sites of ADAR1 editing
Project description:RNA editing by adenosine deaminases acting on RNA (ADARs) is an evolutionarily conserved posttranscriptional modification essential for organismal development and normal cell function. Three catalytically active ADARs are conserved in mammals: two isoforms of ADAR1 referred to as ADAR1-p150 and ADAR1-p110, as well as ADAR2. All recognize and edit double-stranded RNA (dsRNA) structures but demonstrate target specificity and selectivity that dictate the unique essential biological functions of the three enzymes. The editing activity of ADAR1-p150 suppresses autoimmune responses against self-RNA structures, whereas ADAR1-p110 and ADAR2 have other primary functions. To better understand the mechanism of target selection by ADARs, we developed TSniffer, which allows accurate de novo identification of edited transcripts and quantification of the extent of editing within each transcript. We found that 17-40% of protein coding transcripts in mice, ferrets, and humans are edited by ADARs. Individual transcripts can harbor hundreds and thousands of editing sites, mostly within inverted retrotransposable elements. For human transcripts, we found differential editing by ADAR1 and ADAR2, aligning with a supportive role for ADAR2, while some targets were dominantly edited by ADAR1. Relying only on RNA-seq data and reference genome, TSniffer represents a novel tool to decipher the role of ADAR editing in different physiological states including disease models. Its unbiased approach is suitable for any organism.
Project description:RNA editing by adenosine deaminases acting on RNA (ADARs) is an evolutionarily conserved posttranscriptional modification essential for organismal development and normal cell function. Three catalytically active ADARs are conserved in mammals: two isoforms of ADAR1 referred to as ADAR1-p150 and ADAR1-p110, as well as ADAR2. All recognize and edit double-stranded RNA (dsRNA) structures but demonstrate target specificity and selectivity that dictate the unique essential biological functions of the three enzymes. The editing activity of ADAR1-p150 suppresses autoimmune responses against self-RNA structures, whereas ADAR1-p110 and ADAR2 have other primary functions. To better understand the mechanism of target selection by ADARs, we developed TSniffer, which allows accurate de novo identification of edited transcripts and quantification of the extent of editing within each transcript. We found that 17-40% of protein coding transcripts in mice, ferrets, and humans are edited by ADARs. Individual transcripts can harbor hundreds and thousands of editing sites, mostly within inverted retrotransposable elements. For human transcripts, we found differential editing by ADAR1 and ADAR2, aligning with a supportive role for ADAR2, while some targets were dominantly edited by ADAR1. Relying only on RNA-seq data and reference genome, TSniffer represents a novel tool to decipher the role of ADAR editing in different physiological states including disease models. Its unbiased approach is suitable for any organism.
Project description:Adenosine deaminase acting on RNA 1 (ADAR1), is an enzyme that catalyzes the conversion of adenosine to inosine in double-stranded RNA, a process critical for regulation of innate immune response and distinguishing between ‘self and non-self RNA’. It is expressed as two isoforms: nucleolar p110 and cytoplasmic, interferon (IFN)-inducible, p150. The interactome of the p110 under steady-state conditions is well-studied; however, less is known about the interactions of the p150 isoform, particularly during IFN response. To elucidate ADAR1's protein interactions during IFN stimulation, alongside steady-state conditions, three distinct methods of enrichment were used followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These included: immunoprecipitation (IP) of endogenous ADAR1, IP of Strep II-tagged ADAR1, and proximity labeling using BioID. Individual ADAR1 isoforms (p110 and p150) and their respective dsRNA binding-deficient mutants were created to discern isoform-specific and dsRNA-dependent interactions. Altogether, our results reveal a comprehensive ADAR1 interaction map, identifying both known and novel partners, and highlighting the isoform-specific and dsRNA-binding-dependent nature of ADAR1 interactions. Under IFN stimulation, ADAR1's interaction spectrum encompasses viral replication inhibitors and LINE-1 regulators. Mimicking viral infection with HMW poly(I:C) changed the proximal network of proteins for both isoforms. Our findings provide new insights into ADAR1's roles and its dynamic during IFN response.
Project description:Adenosine deaminase acting on RNA 1 (ADAR1), is an enzyme that catalyzes the conversion of adenosine to inosine in double-stranded RNA, a process critical for regulation of innate immune response and distinguishing between ‘self and non-self RNA’. It is expressed as two isoforms: nucleolar p110 and cytoplasmic, interferon (IFN)-inducible, p150. The interactome of the p110 under steady-state conditions is well-studied; however, less is known about the interactions of the p150 isoform, particularly during IFN response. To elucidate ADAR1's protein interactions during IFN stimulation, alongside steady-state conditions, three distinct methods of enrichment were used followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These included: immunoprecipitation (IP) of endogenous ADAR1, IP of Strep II-tagged ADAR1, and proximity labeling using BioID. Individual ADAR1 isoforms (p110 and p150) and their respective dsRNA binding-deficient mutants were created to discern isoform-specific and dsRNA-dependent interactions. Altogether, our results reveal a comprehensive ADAR1 interaction map, identifying both known and novel partners, and highlighting the isoform-specific and dsRNA-binding-dependent nature of ADAR1 interactions. Under IFN stimulation, ADAR1's interaction spectrum encompasses viral replication inhibitors and LINE-1 regulators. Mimicking viral infection with HMW poly(I:C) changed the proximal network of proteins for both isoforms. Our findings provide new insights into ADAR1's roles and its dynamic during IFN response.
Project description:Adenosine deaminase acting on RNA 1 (ADAR1), is an enzyme that catalyzes the conversion of adenosine to inosine in double-stranded RNA, a process critical for regulation of innate immune response and distinguishing between ‘self and non-self RNA’. It is expressed as two isoforms: nucleolar p110 and cytoplasmic, interferon (IFN)-inducible, p150. The interactome of the p110 under steady-state conditions is well-studied; however, less is known about the interactions of the p150 isoform, particularly during IFN response. To elucidate ADAR1's protein interactions during IFN stimulation, alongside steady-state conditions, three distinct methods of enrichment were used followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These included: immunoprecipitation (IP) of endogenous ADAR1, IP of Strep II-tagged ADAR1, and proximity labeling using BioID. Individual ADAR1 isoforms (p110 and p150) and their respective dsRNA binding-deficient mutants were created to discern isoform-specific and dsRNA-dependent interactions. Altogether, our results reveal a comprehensive ADAR1 interaction map, identifying both known and novel partners, and highlighting the isoform-specific and dsRNA-binding-dependent nature of ADAR1 interactions. Under IFN stimulation, ADAR1's interaction spectrum encompasses viral replication inhibitors and LINE-1 regulators. Mimicking viral infection with HMW poly(I:C) changed the proximal network of proteins for both isoforms. Our findings provide new insights into ADAR1's roles and its dynamic during IFN response.
Project description:Adenosine deaminase acting on RNA 1 (ADAR1), is an enzyme that catalyzes the conversion of adenosine to inosine in double-stranded RNA, a process critical for regulation of innate immune response and distinguishing between ‘self and non-self RNA’. It is expressed as two isoforms: nucleolar p110 and cytoplasmic, interferon (IFN)-inducible, p150. The interactome of the p110 under steady-state conditions is well-studied; however, less is known about the interactions of the p150 isoform, particularly during IFN response. To elucidate ADAR1's protein interactions during IFN stimulation, alongside steady-state conditions, three distinct methods of enrichment were used followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These included: immunoprecipitation (IP) of endogenous ADAR1, IP of Strep II-tagged ADAR1, and proximity labeling using BioID. Individual ADAR1 isoforms (p110 and p150) and their respective dsRNA binding-deficient mutants were created to discern isoform-specific and dsRNA-dependent interactions. Altogether, our results reveal a comprehensive ADAR1 interaction map, identifying both known and novel partners, and highlighting the isoform-specific and dsRNA-binding-dependent nature of ADAR1 interactions. Under IFN stimulation, ADAR1's interaction spectrum encompasses viral replication inhibitors and LINE-1 regulators. Mimicking viral infection with HMW poly(I:C) changed the proximal network of proteins for both isoforms. Our findings provide new insights into ADAR1's roles and its dynamic during IFN response.
Project description:Sensing of double-stranded RNA (dsRNA) is an important component of innate immunity. Proteins like PKR and MDA5 recognize dsRNA and activate various pathways to fight viral infection. In addition to viral dsRNA, many endogenous RNAs containing double-stranded regions can be misrecognized as immunogenic. The RNA editing enzyme ADAR1, specifically its p150 isoform, has been shown to suppress activation of PKR and MDA5 through its A-to-I editing activity. While the cytoplasmic ADAR1-p150 isoform has been well established within this role, the functions of the nuclear ADAR1-p110 isoform are less understood. To address this knowledge gap, we utilized proximity labeling by APEX2 to identify putative ADAR1-p110 interacting proteins. We identified 110 proteins across three breast cancer cell lines that either interact with p110 or are within close proximity. Many of these proteins have known roles in RNA metabolism. Nine of the identified proteins belong to the DEAD or DEAH box families of RNA helicases, including DHX9. DHX9 is overexpressed in breast cancer, with expression closely correlated with that of p110. By co-immunoprecipitation we confirmed that p110 interacts with DHX9. Knockdown of DHX9 in several triple-negative breast cancer cell lines caused cell death and activation of the dsRNA sensor PKR. In two cell lines that are refractory to knockdown of ADAR1, the combined knockdown of DHX9 and ADAR1 caused a substantial increase in PKR activity, where knockdown of either alone had no effect. Knockdown of DHX9 and ADAR1 caused activation of the type I IFN pathway, RNase L and NF-KB signaling. Activation of these proteins and pathways was not seen with individual knockdown of ADAR1 or DHX9. Activation of PKR following combined knockdown of ADAR1 and DHX9 could be rescued by expression of p110, p150, DHX9, and catalytically inactive DHX9. Additionally PKR activation could be rescued by the dsRBM of DHX9, revealing an important role for dsRBMs in suppressing PKR activation. Together these results reveal an important role for DHX9 in suppressing dsRNA sensing by multiple pathways.
Project description:This study aims to delineate the role of ADAR1 in human cells beyond its canonical function as an interferon-stimulated gene (ISG). Human monocyte-derived macrophages were subjected to RNA interference targeting either pan-ADAR1 (both isoforms) or the p150 isoform specifically. Quantitative proteomic analyses were performed using state-of-the-art isobaric tandem mass tag (TMT) labeling coupled with liquid chromatography–tandem mass spectrometry (LC-MS/MS). Strikingly, silencing of ADAR1 significantly impacted prototypical macrophage functions, including endocytosis, cholesterol metabolism, and lysosomal processing, without concurrent induction of pro-inflammatory or ISG responses. Pan-ADAR1 silencing resulted in upregulation of proteins involved in lysosomal function and cholesterol processing, whereas selective depletion of ADAR1-p150 led to downregulation of pathways associated with phagocytosis and endocytosis. Moreover, loss of pan-ADAR1 caused a marked downregulation of cell-cycle and p53 signaling pathways, suggesting a potential role for the ADAR1-p110 isoform in regulating cell proliferation. Collectively, these data define previously unappreciated proteomic alterations driven by ADAR1 that influence fundamental macrophage functions beyond its established ISG role.
Project description:Cancer immunotherapy efficacy is often limited by primary and acquired resistance. The RNA- editing enzyme ADAR1 has emerged as a key regulator of tumor immune evasion, yet therapeutic targeting is challenged by the essential physiological roles of its constitutively expressed p110 isoform. Here, we identify the interferon-inducible p150 isoform and its Zα domain as a critical therapeutic vulnerability. We demonstrate that ADAR1 p150 is frequently overexpressed in human cancers and correlates with an immunosuppressive tumor microenvironment. Genetic ablation of ADAR1 p150 intrinsically inhibits tumor proliferation and extrinsically triggers a robust type I interferon response and profound remodeling of the tumor immune landscape, converting immunologically "cold" tumors to "hot." Furthermore, we establish that myeloid-specific ADAR1 deletion synergizes with anti-PD-1 therapy by enhancing antigen presentation and fostering a pro-inflammatory microenvironment. Crucially, we delineate the Zα domain as the essential structural determinant for dsRNA editing selectivity. Targeted disruption of this domain alone, without affecting the catalytic deaminase domain, is sufficient to recapitulate the potent antitumor effects of complete ADAR1 ablation, leading to accumulation of immunogenic dsRNA, activation of cytosolic sensors (MDA5/PKR), and potent anti-tumor immunity. Our work provides a compelling rationale for selectively targeting the ADAR1 p150-Zα axis to reverse malignant RNA editing and overcome resistance to immunotherapy, offering a refined strategy with a potentially superior therapeutic index.