Study functions of ADAR proteins using next generation sequencing of genome and transcriptome
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE38233 | GEO | 2013/09/20
SECONDARY ACCESSION(S): PRJNA167698
REPOSITORIES: GEO
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Project description:Adenosine deaminases, RNA specific (ADAR) are proteins that deaminate adenosine to inosine which is then recognized in translation as guanosine. To study the roles of ADAR proteins in RNA editing and gene regulation, we carried out DNA and RNA sequencing, RNA interference and RNA-immunoprecipitation in human B-cells. We also characterized the ADAR protein complex by mass spectrometry. The results uncovered over 60,000 sites where the adenosines (A) are edited to guanosine (G) and several thousand genes whose expression levels are influenced by ADAR. We also identified more than 100 proteins in the ADAR protein complex; these include splicing factors, heterogeneous ribonucleoproteins and several members of the dynactin protein family. Our findings show that in human B-cells, ADAR proteins are involved in two independent functions: A-to-G editing and gene expression regulation. In addition, we showed that other types of RNA-DNA sequence differences are not mediated by ADAR proteins, and thus there are co- or post-transcriptional mechanisms yet to be determined. Here we studied human B-cells where ADAR proteins (ADAR1 and ADAR2) are expressed but APOBECs are not. We identified the sequence differences between DNA and the corresponding RNA in B-cells from two individuals. Then, we carried out RNA interference, RNA-immunoprecipitation and next generation sequencing to determine the contribution of ADAR proteins in mediating A-to-G editing and other types of RNA-DNA sequence differences.
2013-09-20 | E-GEOD-38233 | biostudies-arrayexpress
Project description:Adenosine deaminases acting on RNA (ADAR) are proteins that deaminate adenosine to inosine, which is then recognized by the ribosome as guanosine. To study the genetic basis of RNA editing efficiency by ADAR, we carried out deep RNA sequencing (RNA-Seq) in human B-cells and uncovered more than 100,000 RNA editing sites. Next, we evaluated the extent of individual variation in the RNA editing among unrelated individuals from Centre d'Etude du Polymorphisme Humain (CEPH) and found significant variation in the levels of editing. To understand whether there exists a genetic component to the variation in RNA editing levels, we obtained RNA-Seq data from 10 pairs of monozygotic twins. These results revealed that there exists a significant genetic component to variation in RNA editing.
2017-07-01 | GSE39167 | GEO
Project description:The ADAR RNA editing enzymes deaminate adenosine bases to inosines in cellular RNAs, recoding open reading frames. Human ADAR1 mutations cause Aicardi-Goutieres Syndrome (AGS) and Adar1 mutant mice showing an aberrant interferon response and death by embryonic day E12.5 model the human disease. Searches have not identified key ADAR1 RNA editing sites recoding immune/haematopoietic proteins but editing is widespread in Alu sequences. We show that Adar1 embryonic lethality is rescued in Adar1; Mavs double mutant mice in which general antiviral responses to cytoplasmic dsRNA are prevented. We propose that inosine bases are epigenetic marks identifying cellular RNA as innate immune ÒselfÓ. Consistent with this idea we show that an editing-active cytoplasmic ADAR is required to prevent aberrant immune responses in Adar1 mutant mouse embryo fibroblasts. No dramatic increase in repetitive transcripts is observed. AGS mutations in ADAR1 affect editing by the interferon-inducible cytoplasmic ADAR1 isoform. RNA-seq expression profiling in Adar1 and Adar1/Mavs knockout mice embryos.
2014-12-19 | E-GEOD-62917 | biostudies-arrayexpress
Project description:RNA base editing applies endogenous or engineered adenosine deaminases to introduce adenosine-to-inosine changes into a target RNA in a highly programmable manner. Recently, notable success was achieved for the repair of disease-causing guanosine-to-adenosine mutations by means of RNA base editing. Here, we propose that RNA base editing could be broadly applied to perturb protein function by removal of regulatory sites of post-translational modification (PTM), like phosphorylation and/or acetylation sites. We demonstrate the feasibility of PTM interference (PTMi) on more than 70 PTM sites in various signaling proteins and identify key determinants for high editing efficiency and potent down-stream effects. Specifically, we demonstrate both negative and positive regulation of the JAK/STAT pathway by PTMi. To identify potent regulatory sites for PTMi, we applied an improved version of the SNAP-ADAR tool, which achieved high editing efficiency over a broad codon scope with tight control of bystander editing. The transient nature of RNA base editing enables the fast, dose-dependent (thus partial) and reversible manipulation of PTM sites, which is a key advantage over DNA editing approaches, where genetic compensation or lethality can conceal a phenotype. In summary, PTM interference might become a valuable field of application of RNA base editing in basic biology and medicine.
2024-04-19 | GSE264114 | GEO
Project description:Alternative mRNA splicing is a major mechanism for gene regulation and transcriptome diversity. Despite the extent of the phenomenon, the regulation and specificity of the splicing machinery are only partially understood. Adenosine-to-inosine (A-to-I) RNA editing of pre-mRNA by ADAR enzymes has been linked to splicing regulation in several cases. Here we used bioinformatics approaches, RNA-seq and exon-specific microarray of ADAR knockdown cells to globally examine how ADAR and its A-to-I RNA editing activity influence alternative mRNA splicing. Although A-to-I RNA editing only rarely targets canonical splicing acceptor, donor, and branch sites, it was found to affect splicing regulatory elements (SREs) within exons. Cassette exons were found to be significantly enriched with A-to-I RNA editing sites compared with constitutive exons. RNA-seq and exon-specific microarray revealed that ADAR knockdown in hepatocarcinoma and myelogenous leukemia cell lines leads to global changes in gene expression, with hundreds of genes changing their splicing patterns in both cell lines. This global change in splicing pattern cannot be explained by putative editing sites alone. Genes showing significant changes in their splicing pattern are frequently involved in RNA processing and splicing activity. Analysis of recently published RNA-seq data from glioblastoma cell lines showed similar results. Our global analysis reveals that ADAR plays a major role in splicing regulation. Although direct editing of the splicing motifs does occur, we suggest it is not likely to be the primary mechanism for ADAR-mediated regulation of alternative splicing. Rather, this regulation is achieved by modulating trans-acting factors involved in the splicing machinery. HepG2 and K562 cell lines were stably transfected with plasmids containing siRNA designed to specifically knock down ADAR expression (ADAR KD). This in order to examine how ADAR affects alternative splicing globally.
2013-06-15 | E-GEOD-47945 | biostudies-arrayexpress
Project description:Alternative mRNA splicing is a major mechanism for gene regulation and transcriptome diversity. Despite the extent of the phenomenon, the regulation and specificity of the splicing machinery are only partially understood. Adenosine-to-inosine (A-to-I) RNA editing of pre-mRNA by ADAR enzymes has been linked to splicing regulation in several cases. Here we used bioinformatics approaches, RNA-seq and exon-specific microarray of ADAR knockdown cells to globally examine how ADAR and its A-to-I RNA editing activity influence alternative mRNA splicing. Although A-to-I RNA editing only rarely targets canonical splicing acceptor, donor, and branch sites, it was found to affect splicing regulatory elements (SREs) within exons. Cassette exons were found to be significantly enriched with A-to-I RNA editing sites compared with constitutive exons. RNA-seq and exon-specific microarray revealed that ADAR knockdown in hepatocarcinoma and myelogenous leukemia cell lines leads to global changes in gene expression, with hundreds of genes changing their splicing patterns in both cell lines. This global change in splicing pattern cannot be explained by putative editing sites alone. Genes showing significant changes in their splicing pattern are frequently involved in RNA processing and splicing activity. Analysis of recently published RNA-seq data from glioblastoma cell lines showed similar results. Our global analysis reveals that ADAR plays a major role in splicing regulation. Although direct editing of the splicing motifs does occur, we suggest it is not likely to be the primary mechanism for ADAR-mediated regulation of alternative splicing. Rather, this regulation is achieved by modulating trans-acting factors involved in the splicing machinery. HepG2 and K562 cell lines were stably transfected with plasmids containing siRNA designed to specifically knock down ADAR expression (ADAR KD). This in order to examine how ADAR affects alternative splicing globally.
2013-06-17 | E-GEOD-47997 | biostudies-arrayexpress
Project description:Endogenous double-stranded RNA is prevented from activating the cytosolic antiviral receptor MDA5 by adenosine-to-inosine editing by ADAR. Consequently, CRISPR/cas9 targeting ADAR in the human monocytic cell line THP-1 induces a spontaneous MDA5-dependent interferon response. This response is synergistically enhanced by concomitant CRISPR/cas9 targeting of hnRNPC. For this study, cas9 transgenic THP-1 were nucleofected with combinations of control gRNA, ADAR gRNA or hnRNPC gRNA to elucidate the basis for synergistic interferon-stmulated gene induction by combined ADAR and hnRNPC targeting. As a control for interferon-stimulated gene induction, IFN-alpha treated THP-1 were included, as well. To investigate potential interferon inducing mechanisms, we quantified gene expression, intron expression as well as the expression of regions rich in adenosine-to-inosine editing clusters. In a second part, nuclear vs cytosolic distribution of RNA rich in adenosine-to-inosine clusters was investigated by sequencing of total RNA or RNA from cytosolic and nuclear extracts of ADAR and/or hnRNPC targeted cells. In the first part of the study, STING-deficient, cas9 transgenic THP-1 were nucleofected with combinations of control, GFP-targeting, ADAR-targeting or hnRNPC-targeting gRNA and cells collected for total RNA extraction on days three, four and five after nucleofection. In addition, another control-nucleofected sample was treated on day 3 for 24 h. The experiment was repeated three times leading to three replicates per condition. In the second part, WT cas9-transgenic THP-1 were nucleofected with combinations of control, ADAR-targeting or hnRNPC-targeting gRNA and cells were either collected for total RNA extraction or separated into digitonin-soluble (cytosolic) and digitonin-resistant (nuclear and mitochondrial) compartments and then RNA extracted. The experiment was repeated twice leading to two replicates per condition. Differential gene expression analysis confirmed synergistic induction of interferon-stimulated genes. RNA-seq analysis demonstrated dysregulation of Alu-containing introns in hnRNPC-deficient cells via utilization of unmasked cryptic splice sites, including introns containing ADAR-dependent A-to-I editing clusters or regions enriched in editing clusters (ECRs) in general. These putative MDA5 ligands showed reduced editing in the absence of ADAR, providing a plausible mechanism for the combined effects of hnRNPC and ADAR. Part 2 of the study confirmed cytosolic access of a subset of ECRs to the cytosol.
2021-07-16 | GSE176012 | GEO
Project description:The ADAR RNA editing enzymes deaminate adenosine bases to inosines in cellular RNAs, recoding open reading frames. Human ADAR1 mutations cause Aicardi-Goutieres Syndrome (AGS) and Adar1 mutant mice showing an aberrant interferon response and death by embryonic day E12.5 model the human disease. Searches have not identified key ADAR1 RNA editing sites recoding immune/haematopoietic proteins but editing is widespread in Alu sequences. We show that Adar1 embryonic lethality is rescued in Adar1; Mavs double mutant mice in which general antiviral responses to cytoplasmic dsRNA are prevented. We propose that inosine bases are epigenetic marks identifying cellular RNA as innate immune ÒselfÓ. Consistent with this idea we show that an editing-active cytoplasmic ADAR is required to prevent aberrant immune responses in Adar1 mutant mouse embryo fibroblasts. No dramatic increase in repetitive transcripts is observed. AGS mutations in ADAR1 affect editing by the interferon-inducible cytoplasmic ADAR1 isoform.
2014-12-19 | GSE62917 | GEO
Project description:The RNA editing enzyme ADAR chemically modifies adenosine (A) to inosine (I), which is interpreted by the ribosome as a guanosine. Here we assess cotranscriptional A-to-I editing in Drosophila, by isolating nascent RNA from adult fly heads and subjecting samples to high-throughput sequencing. There are a large number of edited sites within nascent exons. Nascent RNA from an ADAR null mutant strain was also sequenced, indicating that almost all A-to-I events require ADAR. Moreover, mRNA editing levels correlate with editing levels within the cognate nascent RNA sequence, indicating that the extent of editing is set cotranscriptionally. Surprisingly, the nascent data also identify an excess of intronic over exonic editing sites. These intronic sites occur preferentially within introns that are poorly spliced cotranscriptionally, suggesting a link between editing and splicing. We conclude that ADAR-mediated editing is more widespread than previously indicated and largely occurs cotranscriptionally.
2012-05-31 | GSE37232 | GEO
Project description:ADAR proteins alter gene expression both via catalyzing adenosine-to-inosine RNA editing and in an editing-independent manner by binding to target RNAs. Loss of ADARs affects neuronal function in all animals studied to date. To identify important neuronal targets in C. elegans, we performed the first unbiased assessment of the effects of ADR-2, the C. elegans editing enzyme, on the neural transcriptome. We identified the neural editome and gene expression changes associated with the loss of adr-2. As C. elegans lacking adr-2 exhibit reduced chemotaxis, our studies focused on targets that regulate this process. We identified an edited mRNA, clec-41, whose expression is dependent on ADR-2. Expressing clec-41 in adr-2 deficient neural cells restored chemotaxis. This study is the first of its kind in the RNA editing field to span from developing novel methodology for tissue-specific target identification to organismal behavior, significantly advancing our understanding of ADAR functions in neural cells.
2017-06-13 | GSE98869 | GEO