Project description:RNA binding proteins (RBPs) perform a myriad of functions and are implicated in numerous neurological diseases. To identify the targets of RBPs in small numbers of cells, we developed TRIBE, in which the catalytic domain of the RNA editing enzyme ADAR (ADARcd) is fused to a RBP. In STAMP, the ADARcd is replaced by the RNA editing enzyme Apobec (REF). Here we compared the two enzymes fused to the RBP TDP43 in human cells. Although they both identified TDP43 target mRNAs, combining the two methods more successfully identified high confidence targets. We also assayed the two enzymes in Drosophila cells in which RBP-Apobec fusions generated only low numbers of editing sites comparable to the level of control editing. This was true for two different RBPs, Hrp48 and Thor (Drosophila EIF4E-BP), and contrasted with successful RBP-ADARcd fusions. The results indicate that TRIBE is the method of choice in Drosophila.
Project description:RNA binding proteins (RBPs) perform a myriad of functions and are implicated in numerous neurological diseases. To identify the targets of RBPs in small numbers of cells, we developed TRIBE, in which the catalytic domain of the RNA editing enzyme ADAR (ADARcd) is fused to a RBP. In STAMP, the ADARcd is replaced by the RNA editing enzyme Apobec (REF). Here we compared the two enzymes fused to the RBP TDP43 in human cells. Although they both identified TDP43 target mRNAs, combining the two methods more successfully identified high confidence targets. We also assayed the two enzymes in Drosophila cells in which RBP-Apobec fusions generated only low numbers of editing sites comparable to the level of control editing. This was true for two different RBPs, Hrp48 and Thor (Drosophila EIF4E-BP), and contrasted with successful RBP-ADARcd fusions. The results indicate that TRIBE is the method of choice in Drosophila.
Project description:RNA transcripts are bound and regulated by RNA-binding proteins (RBPs). Current methods for identifying in vivo targets of a RBP are imperfect and not amenable to examining small numbers of cells. To address these issues, we developed TRIBE (Targets of RNA-binding proteins Identified By Editing), a technique that couples an RBP to the catalytic domain of the Drosophila RNA editing enzyme ADAR and expresses the fusion protein in vivo. RBP targets are marked with novel RNA editing events and identified by sequencing RNA. We have used TRIBE to identify the targets of three RBPs (Hrp48, dFMR1 and NonA). TRIBE compares favorably to other methods, including CLIP, and we have identified RBP targets from as little as 150 specific fly neurons. TRIBE can be performed without an antibody and in small numbers of specific cells.
Project description:Nearly every step of RNA regulation is mediated by binding proteins (RBPs). The most common method to identify specific RBP target transcripts in vivo is by crosslinking (“CLIP” and its variants), which rely on protein-RNA crosslinking and specific antibodies. Another recently introduced method exploits RNA editing, with the hyperactive mutant catalytic domain of ADAR covalently attached to a specific RBP (“HyperTRIBE”). Both CLIP and TRIBE approaches suffer from difficulties in distinguishing real RNA targets from false negative and especially false positive signals. To critically evaluate this problem, we used fibroblasts from a mouse where every endogenous β-actin mRNA molecule was tagged with the bacteriophage MS2 RNA stem loops in the β-actin 3’ UTR; hence there is only a single bona fide target mRNA for the MS2 capsid protein (MCP). CLIP and HyperTRIBE (hereafter referred to as TRIBE) could both detect the single RNA target, albeit with some false positives (transcripts lacking the MS2 stem loops). Consistent false positive CLIP signals could be attributed to nonspecific antibody interactions. However, to our surprise the putative false positive TRIBE targets correlated with the location of genes spatially proximal to the β-actin gene. This result indicates that MCP-ADAR bound to β-actin mRNA contacted and edited nearby nascent transcripts, as evidenced by frequent intronic editing. Importantly, nascent transcripts on nearby chromosomes were also edited, agreeing with the interchromosomal contacts observed in chromosome paint and Hi-C. These results were repeated in human osteosarcoma cells with a randomly integrated and inducible MS2 reporter and indicated that MS2-TRIBE can be applied to a broad array of cells and transcripts. The identification of nascent RNA-RNA contacts imply that RNA-regulatory proteins such as splicing factors can associate with multiple nascent transcripts and thereby form domains of post-transcriptional activity, which increase their local concentrations. These results indicate that TRIBE combined with the MS2 system, MS2-TRIBE, is a new tool to study nuclear RNA organization and regulation.
Project description:Identification of RNA targets of RNA-binding proteins (RBPs) is essential for complete understanding of their biological functions. However, it is still a challenge to identify the biologically relevant targets of RBPs through in vitro strategies of RIP-seq, HITS-CLIP, or GoldCLIP due to the potentially high background and complicated manipulation. In malaria parasites, RIP-seq and gene disruption are the few tools available currently for identification of RBP targets. Here, we have adopted the TRIBE (Targets of RNA binding proteins identified by editing) system to in vivo identify the RNA targets of PfDis3, a key exoribonuclease subunit of RNA exosome in Plasmodium falciparum. We generated a transgenic parasite line of Pfdis3-ADARcd, which catalyzes an adenosine (A)-to-inosine (I) conversion at the potential interacting sites of PfDis3-targeting RNAs. Most of PfDis3 target genes contain one edit site. The majority of the edit sites detected by PfDis3-TRIBE locate in exons and spread across the entire coding regions. The nucleotides adjacent to the edit sites contain ~ 75% of A+T. PfDis3-TRIBE target genes are biases toward higher RIP enrichment, suggesting that PfDis3-TRIBE preferentially detects stronger PfDis3 RIP targets. Collectively, PfDis3-TRIBE is a favorable tool to identify in vivo target genes of RBP with high efficiency and reproducibility. Additionally, the PfDis3-targeting genes are involved in stage-related biological processes during the blood-stage development. PfDis3 appears to shape the dynamic transcriptional transcriptome of malaria parasites through post-transcriptional degradation of a variety of unwanted transcripts from both strands in the asexual blood stage.
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.
Project description:Identification of RNA targets of RNA-binding proteins (RBPs) is essential for complete understanding of their biological functions. However, it is still a challenge to identify the biologically relevant targets of RBPs through in vitro strategies of RIP-seq, HITS-CLIP, or GoldCLIP due to the potentially high background and complicated manipulation. In malaria parasites, RIP-seq and gene disruption are the few tools available currently for identification of RBP targets. Here, we have adopted the TRIBE (Targets of RNA binding proteins identified by editing) system to in vivo identify the RNA targets of PfDis3, a key exoribonuclease subunit of RNA exosome in Plasmodium falciparum. We generated a transgenic parasite line of Pfdis3-ADARcd, which catalyzes an adenosine (A)-to-inosine (I) conversion at the potential interacting sites of PfDis3-targeting RNAs. Most of PfDis3 target genes contain one edit site. The majority of the edit sites detected by PfDis3-TRIBE locate in exons and spread across the entire coding regions. The nucleotides adjacent to the edit sites contain ~ 75% of A+T. PfDis3-TRIBE target genes are biases toward higher RIP enrichment, suggesting that PfDis3-TRIBE preferentially detects stronger PfDis3 RIP targets. Collectively, PfDis3-TRIBE is a favorable tool to identify in vivo target genes of RBP with high efficiency and reproducibility. Additionally, the PfDis3-targeting genes are involved in stage-related biological processes during the blood-stage development. PfDis3 appears to shape the dynamic transcriptional transcriptome of malaria parasites through post-transcriptional degradation of a variety of unwanted transcripts from both strands in the asexual blood stage
Project description:Identification of RNA targets of RNA-binding proteins (RBPs) is essential for complete understanding of their biological functions. However, it is still a challenge to identify the biologically relevant targets of RBPs through in vitro strategies of RIP-seq, HITS-CLIP, or GoldCLIP due to the potentially high background and complicated manipulation. In malaria parasites, RIP-seq and gene disruption are the few tools available currently for identification of RBP targets. Here, we have adopted the TRIBE (Targets of RNA binding proteins identified by editing) system to in vivo identify the RNA targets of PfDis3, a key exoribonuclease subunit of RNA exosome in Plasmodium falciparum. We generated a transgenic parasite line of Pfdis3-ADARcd, which catalyzes an adenosine (A)-to-inosine (I) conversion at the potential interacting sites of PfDis3-targeting RNAs. Most of PfDis3 target genes contain one edit site. The majority of the edit sites detected by PfDis3-TRIBE locate in exons and spread across the entire coding regions. The nucleotides adjacent to the edit sites contain ~ 75% of A+T. PfDis3-TRIBE target genes are biases toward higher RIP enrichment, suggesting that PfDis3-TRIBE preferentially detects stronger PfDis3 RIP targets. Collectively, PfDis3-TRIBE is a favorable tool to identify in vivo target genes of RBP with high efficiency and reproducibility. Additionally, the PfDis3-targeting genes are involved in stage-related biological processes during the blood-stage development. PfDis3 appears to shape the dynamic transcriptional transcriptome of malaria parasites through post-transcriptional degradation of a variety of unwanted transcripts from both strands in the asexual blood stage
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.