Project description:Protein-RNA interaction networks are essential to understand gene regulation control. Identifying the binding sites of RNA-binding proteins (RBPs) by CLIP (UV-crosslinking and immunoprecipitation) represents one of the most powerful methods to map in vivo protein-RNA interactions. However, the traditional CLIP protocol is technically challenging, which requires radioactive labeling and suffers from material loss during PAGE-membrane transfer procedures. Here we introduce a super-efficient CLIP method (GoldCLIP) that omits all gel purification steps. This nonisotopic method allowed us to perform highly reproducible CLIP experiments with classical RBP such as PTB in human cell lines. In principle, our method guarantees sequencing library constructions, providing the protein of interest can be successfully crosslinked to RNAs in living cells. GoldCLIP is readily applicable to diverse factors to uncover their endogenous targets.
Project description:In vivo microRNA-target interactions from adult mouse cortex were identified with CLEAR-CLIP, a modified AGO HITS-CLIP approach that allows direct ligation of microRNA and target within purified, endogenous AGO-RNA complexes.
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:Streamlined protocol for fluorescence-based PAR-CLIP (fPAR-CLIP) that eliminates the need to use radioactivity. Protocol is based on direct ligation of a fluorescently labeled adapter to the 3’end of crosslinked RNA on immobilized ribonucleoproteins, followed by isolation of the RNA and efficient conversion into cDNA without the previously needed size fractionation on denaturing polyacrylamide gels. These improvements cut the experimentation time from 4-5 to 2 days and increases sensitivity by 10-100-fold.
Project description:RNA-binding proteins are instrumental for post-transcriptional gene regulation, yet transcriptome-wide methods to profile RNA-protein interactions remain technically challenging. We present an improved library preparation strategy for cross-linking and immunoprecipitation (CLIP) that involves tailing and ligation of cDNA molecules (TLC) for increased sensitivity and efficiency. TLC-CLIP eliminates time-consuming purifications, reduces sample loss, and minimises experimental steps, allowing precise profiling of RNA-protein interactions from limited starting material at nucleotide resolution.
Project description:RNA-binding proteins are instrumental for post-transcriptional gene regulation, yet transcriptome-wide methods to profile RNA-protein interactions remain technically challenging. We present an improved library preparation strategy for cross-linking and immunoprecipitation (CLIP) that involves tailing and ligation of cDNA molecules (TLC) for increased sensitivity and efficiency. TLC-CLIP eliminates time-consuming purifications, reduces sample loss, and minimises experimental steps, allowing precise profiling of RNA-protein interactions from limited starting material at nucleotide resolution.
Project description:The identification of RNAs that are recognized by RNA-binding proteins (RNA-BPs) using techniques such as Crosslinking and Immunoprecipitation (CLIP) has revolutionized the genome-wide discovery of RNA-BP RNA targets. Among the different versions of CLIP that have been developed, the use of photoactivable nucleoside analogs has resulted in high efficiency photoactivable ribonucleoside-enhanced CLIP (PAR-CLIP) in vivo. Nonetheless, PAR-CLIP has not yet been applied in prokaryotes. To determine if PAR-CLIP can be used in prokaryotes, we determined suitable conditions for the incorporation of 4-thiouridine (4SU), a photoactivable nucleoside, into E. coli RNA and for the isolation of RNA crosslinked to RNA-BPs of interest. Applying this technique to Hfq, a well-characterized regulator of small RNA (sRNA)-messenger RNA (mRNA) interactions, we showed that PAR-CLIP identified most of the known sRNA targets of Hfq, as well as functionally relevant sites of Hfq-mRNA interactions at nucleotide resolution. Based on our findings, PAR-CLIP represents an improved method to identify both the RNAs and the specific regulatory sites that are recognized by RNA-BPs in prokaryotes.
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.