Project description:miRNA-target chimeras identified with CLEAR-CLIP reveal miRNA 3' end pairing as a major determinant of Argonaute binding in vivo [mouse cortex CLEAR-CLIP]
Project description:miRNA-target chimeras identified with CLEAR-CLIP reveal miRNA 3' end pairing as a major determinant of Argonaute binding in vivo [human Huh7.5 AGO-CLIP & CLEAR-CLIP]
Project description:microRNAs (miRNAs) act as sequence-specific guides for Argonaute (AGO) proteins, which mediate post-transcriptional silencing of target mRNAs. Despite their importance in many biological processes, rules governing AGO-miRNA targeting are only partially understood. We use a modified AGO HITS-CLIP strategy, termed CLEAR (Covalent Ligation of Endogenous Argonaute-bound RNAs) CLIP that enriches miRNAs ligated to their endogenous mRNA targets. CLEAR-CLIP mapped ~130,000 endogenous miRNA-target interactions in mouse brain and ~40,000 in human hepatoma cells. Motif and structural analysis define expanded pairing rules for over 200 mammalian miRNAs. Most interactions combine seed-based pairing with distinct, miRNA-specific patterns of auxiliary pairing. At some regulatory sites, this specificity confers distinct silencing functions to miRNA family members with shared seed sequences but divergent 3’ ends. This work provides a means for explicit biochemical identification of miRNA sites in vivo, leading to the discovery that miRNA 3’ end pairing is a general determinant of AGO binding specificity.
Project description:microRNAs (miRNAs) act as sequence-specific guides for Argonaute (AGO) proteins, which mediate post-transcriptional silencing of target mRNAs. Despite their importance in many biological processes, rules governing AGO-miRNA targeting are only partially understood. We use a modified AGO HITS-CLIP strategy, termed CLEAR (Covalent Ligation of Endogenous Argonaute-bound RNAs) CLIP that enriches miRNAs ligated to their endogenous mRNA targets. CLEAR-CLIP mapped ~130,000 endogenous miRNA-target interactions in mouse brain and ~40,000 in human hepatoma cells. Motif and structural analysis define expanded pairing rules for over 200 mammalian miRNAs. Most interactions combine seed-based pairing with distinct, miRNA-specific patterns of auxiliary pairing. At some regulatory sites, this specificity confers distinct silencing functions to miRNA family members with shared seed sequences but divergent 3’ ends. This work provides a means for explicit biochemical identification of miRNA sites in vivo, leading to the discovery that miRNA 3’ end pairing is a general determinant of AGO binding specificity.
Project description:With regulatory roles in development, cell proliferation and disease, micro-RNA (miRNA) biology is of great importance and a potential key to novel RNA-based therapeutic regimens. Biochemically based sequencing approaches have provided robust means of uncovering miRNA binding landscapes on transcriptomes of various species. However, a current limitation to the therapeutic potential of miRNA biology in cattle is the lack of validated miRNAs targets. Here, we use cross-linking immunoprecipitation (CLIP) of the Argonaute (AGO) proteins and unambiguous miRNA-target identification through RNA chimeras to define a regulatory map of miRNA interactions in the cow (Bos taurus). The resulting interactome is the deepest reported to date for any species, demonstrating that comprehensive maps can be empirically obtained. We observe that bovine miRNA targeting principles are consistent with those observed in other mammals. Motif and structural analyses define expanded pairing rules with most interactions combining seed-based pairing with distinct, miRNA-specific patterns of auxiliary pairing. Further, miRNA-target chimeras had predictive value in evaluating true regulatory sites of the miR-17 family. Finally, we define miRNA-specific targeting for >5000 mRNAs and determine gene ontologies (GO) for these targets. This confirmed repression of genes important for embryonic development and cell cycle progress by the let-7 family, and repression of those involved in cell cycle arrest by the miR-17 family, but it also suggested a number of unappreciated miRNA functions. Our results provide a significant resource for transcriptomic understanding of bovine miRNA regulation, and demonstrate the power of experimental methods for establishing comprehensive interaction maps.
Project description:To exert regulatory function, miRNAs guide Argonaute (AGO) proteins to partially complementary sites on target RNAs. Crosslinking and immunoprecipitation (“re state-of-the-art to map AGO binding sites, but assigning the targeting miRNA to these sites relies on bioinformatics predictions and is therefore indirect. To directly and unambiguously identify miRNA:target site interactions, we modified our CLIP methodology in C. elegans to experimentally ligate miRNAs to their target sites. Unexpectedly, ligation reactions also occurred in absence of the exogenous ligase. Our in vivo dataset and re-analysis of published mammalian AGO-CLIP data for miRNA-chimeras yielded >17,000 miRNA:target site interactions. Analysis of interactions and extensive experimental validation of chimera-discovered targets of viral miRNAs suggest that our strategy identifies canonical, non-canonical, and non-conserved miRNA interactions. Our data suggest that ~80% of miRNA:targets have perfect or partial seed complementarity. In summary, analysis of miRNA:target chimeras enables the systematic, context-specific, in vivo discovery of miRNA interactions.
Project description:To exert regulatory function, miRNAs guide Argonaute (AGO) proteins to partially complementary sites on target RNAs. Crosslinking and immunoprecipitation (“re state-of-the-art to map AGO binding sites, but assigning the targeting miRNA to these sites relies on bioinformatics predictions and is therefore indirect. To directly and unambiguously identify miRNA:target site interactions, we modified our CLIP methodology in C. elegans to experimentally ligate miRNAs to their target sites. Unexpectedly, ligation reactions also occurred in absence of the exogenous ligase. Our in vivo dataset and re-analysis of published mammalian AGO-CLIP data for miRNA-chimeras yielded >17,000 miRNA:target site interactions. Analysis of interactions and extensive experimental validation of chimera-discovered targets of viral miRNAs suggest that our strategy identifies canonical, non-canonical, and non-conserved miRNA interactions. Our data suggest that ~80% of miRNA:targets have perfect or partial seed complementarity. In summary, analysis of miRNA:target chimeras enables the systematic, context-specific, in vivo discovery of miRNA interactions. In vivo PAR-CLIP basically as described previously (Jungkamp et al. 2011) using GFP-tagged ALG-1 expressing worms in L3 stage. Worm lysate was treated with RNase T1. Following immunoprecipitation and a second RNase T1 digest, it was proceeded as described in Hafner et al. 2010. For the modified iPAR-CLIP ligation samples and its control samples immuno-purified complexes were treated with PNK phospathase minus, subjected to ligation with T4 RNA ligase/no ligase added and subsequently phosphorylated with PNK. Protein purification and RNA library preparation essentially as described in Hafner et al., but with the selection of longer RNA products.
Project description:Using the CLEAR-CLIP methodology (PMID: 26602609) combined with high throughput sequencing, all the binding sites of the Argonaute (AGO) proteins on SARS-CoV-2 RNAs were identified as well as the miRNAs contributing to each binding site. Consequently, SARS-CoV-2 mutants were engineered to investigate the functional relevance of the main binding sites. The effect of the infection on the cellular miRNAs was also investigated using the same CLEAR-CLIP data and RNA-Seq analysis.
Project description:We obtained miRNA profiles by miRnome sequencing from ICGC MMML-Seq patients diagnosed with Burkitt lymphoma, diffuse large B-cell lymphoma and follicular lymphoma and provide evidence of subtype-specific miRNA expression differences. We describe differentially expressed, mutated, edited and not previously annotated miRNAs.
Addditionally, by performing argonaute-2 photoactivatable ribonucleoside-enhanced cross-linking and immunoprecipitation (PAR-CLIP) experiments, we obtained a set of biochemically-validated miRNA binding sites and identified miRNA-mRNA interaction pairs with a negative correlation in patient RNASeq data.