Project description:Endogenous double-stranded RNA (dsRNA) triggers pro-inflammatory signaling and has been shown to accumulate in Alzheimer’s disease (AD), but the origins of this dsRNA are incompletely understood. Transposable elements (TEs), which are non-coding DNA sequences capable of forming dsRNA, are a potential endogenous source of dsRNA in AD. We generated dsRNA immunoprecipitation (J2 dsRNA antibody) data on astrocytes treated with or without a siRNA to knock down the dsRNA editing enzyme ADAR1. We analyzed TE transcripts enriched in dsRNA pools when ADAR1 was knocked down, and we identified putative dsRNA-prone TEs, which were also present in secondary analyses of datasets profiling RNAs bound to PKR, MDA5, and the p110 isoform of ADAR1.
Project description:The antiviral defense in vertebrates requires the innate immune system to sense foreign “non-self” nucleic acids while avoiding “self” nucleic acids, which is accomplished by an intricate system. Cellular double-stranded RNAs (dsRNAs) are edited by the RNA editing enzyme ADAR1 to prevent their dsRNA structure pattern from being recognized as viral dsRNA. Lack of RNA editing by ADAR1 enables activation of MDA5, a cytosolic dsRNA sensor, by cellular dsRNA. Additional RNA editing- independent functions of ADAR1 have been proposed, but the specific mechanism remains elusive. Here we demonstrate that RNA binding by ADAR1, independent of its editing activity, restricts the activation of PKR, another cytosolic dsRNA sensor, by cellular dsRNA. Mechanistically, the loss of ADAR1 editing caused MDA5 activation to induce interferon signaling, while a lack of ADAR1 protein or its dsRNA binding ability led to PKR activation, with subsequent stress granule formation and proliferation arrest. Based on these findings we rescued the Adar1−/− mice from embryonic lethality to adulthood by deleting both MDA5 and PKR, in contrast to the limited rescue of Adar1−/− mice by removing MDA5 or PKR alone. Our findings reveal a multifaceted contribution of ADAR1 in regulating the immunogenicity of “self” dsRNAs. Furthermore, ADAR1 is an immuno-oncology target for drug development, and the separation of ADAR1’s RNA editing and binding functions provides mechanistic insights for such developments.
Project description:ADAR1 regulates the accumulation of endeognouse double-stranded RNA (dsRNA), a pro-inflammatory/innate immune activator. The purpose of this study was to measure the effects of ADAR1 suppression in human astrocytes and determine RNAs regulated by ADAR1. Primary human astrocytes were culture and transfected with a scramble or ADAR1 siRNA. RNA was isolated from these cells for total RNA-seq to analyze changes in gene/repetitive element expression and RNA editing.
Project description:Adenosine-to-Inosine (A-to-I) editing of double stranded RNA (dsRNA) is an essential modifier of dsRNA immunogenicity. Loss of Adenosine deaminase acting on RNA 1 (ADAR1), or its A-to-I editing activity, triggers a lethal MDA5-dependent autoinflammatory response to endogenous unedited dsRNA. We performed a genome-wide suppressor screen to map the genetic landscape regulating the response to a loss of ADAR1 mediated A-to-I editing. This identified that the interacting proteins GGNBP2, CNOT10 and CNOT11 regulate immunogenic sensing following loss of A-to-I editing. GGNBP2 acts between transcription and cytoplasmic MDA5 sensing. Loss of GGNBP2 modified the distribution of dsRNA within cells, reducing the cytoplasmic dsRNA load and preventing induction of type I IFN and lethal autoinflammation. GGNBP2, CNOT10 and CNOT11 are novel regulators of the cellular response to unedited dsRNA.
Project description:Adenosine deaminase acting on RNA 1 (ADAR1) is the master RNA editor, catalyzing the deamination of adenosine to inosine. RNA editing is vital for preventing abnormal activation of cytosolic nucleic acid sensing pathways by self-double-stranded RNAs. Here we determine by parallel analysis of RNA secondary structure sequencing (PARS-seq), the global RNA secondary structure changes in ADAR1 deficient cells. Surprisingly, ADAR1 silencing resulted in a lower global double-stranded to single-stranded RNA ratio, suggesting that A-to-I editing can stabilize a large subset of imperfect RNA duplexes. The duplexes destabilized by editing are composed of vastly complementary inverted Alus found in untranslated regions of genes with vital biological processes, including housekeeping functions and type-I interferon responses. They are predominantly cytoplasmic and generally demonstrate higher ribosomal occupancy. Our findings imply that the editing effect on RNA secondary structure is context dependent and underline the intricate regulatory role of ADAR1 on global RNA secondary structure.
Project description:Although recent evidence suggests that overlapping sense/antisense transcription is a common feature in higher eukaryotes, the possibility that overlapping transcripts could interact to each other and bear a specific biological function has not been explored. Here we show that a plethora of sense/antisense transcript pairs are co-expressed from 8q24.21 within the same cell and acquire a stable double-stranded RNA conformation. Interestingly, these molecules display predominantly nuclear localization and establish specific interactions with nuclear components. A detailed characterization of a particular sense/antisense pair (ndsRNA-2a) revealed that this molecule displays differential localization throughout the cell cycle, interacts with RCC1 and RAN and through the latter with the mitotic RANGAP1-SUMO1/RANBP2 complex. Notably, an increased number of bi/multi-nucleated cells and chromatin bridges were observed upon ndsRNA-2a overexpression, whereas strand-specific ndsRNA-2a knockdown leads to mitotic catastrophe and cell death. This suggests a functional role of ndsRNA-2a in cell cycle progression that critically requires its double stranded nature. Finally, the identification of hundreds of sense/antisense transcripts pairs harboring ndsRNA profile signatures and their regulation by cellular cues suggests that ndsRNAs constitute a novel class of regulatory molecules that are likely to be involved in a plethora of biological processes. PLB985 long (3x datasets) and small (3x datasets) strand specific RNA-Seq for captured RNAs. Global PLB985 for long (2x datasets) and small RNAs (2x datasets). Global libraries for EtOH (vehicle) treated (1x dataset) or retinoic acid induced differentiated PLB985 cells (1x dataset).