![]() ![]() Unfortunately, using proteins as bait has limited utility for identifying novel RNA-binding proteins that interact with an RNA of interest. Methods like cross-linking immunoprecipitation (CLIP) identify RNA-protein interactions by cross-linking RNAs and proteins with UV light, followed by an antibody pulldown of a protein of interest, much like using ChIP for studying protein and DNA interactions. Require prior knowledge that the protein of interest interacts with RNA.While native purification preserves RNA structure and naturally occurring complexes present in the cell, it can also introduce non-physiological RNA-protein interactions due to sample processing. ![]() Challenges with existing RNA-protein interaction methods coli biotin ligase BirA* from BioID and allows a researcher to identify proteins that bind an RNA motif of interest in living cells. To address this need, the Khavari lab at Stanford created the RNA-protein interaction detection (RaPID) method. But what if you want to study RNA-protein interactions? The characterization of RNA-protein interactions has lagged behind, likely due to limitations of current means to detect RNA-protein interactions. There are numerous ways to detect DNA-protein interactions or to analyze chromatin states ( CHIP-seq, FAIRE-seq, Cut & Run ) and to detect protein-protein interactions ( yeast-two hybrid, Co-IP, BioID ), and that’s just to name a few. RNA Biol.Sometimes it feels like DNA and protein get all the attention. Crosslinking-immunoprecipitation (iCLIP) analysis reveals global regulatory roles of hnRNP L. Rossbach, O., Hung, L.H., Khrameeva, E., Schreiner, S., Konig, J., Curk, T., Zupan, B., Ule, J., Gelfand, M.S., and Bindereif, A.iCLIP–transcriptome-wide mapping of protein-RNA interactions with individual nucleotide resolution. Konig, J., Zarnack, K., Rot, G., Curk, T., Kayikci, M., Zupan, B., Turner, D.J., Luscombe, N.M., and Ule, J.iCLIP: Protein-RNA interactions at nucleotide resolution. Huppertz, I., Attig, J., D’Ambrogio, A., Easton, L.E., Sibley, C.R., Sugimoto, Y., Tajnik, M., Konig, J., and Ule, J.PIPE-CLIP: a comprehensive online tool for CLIP-seq data analysis. Chen, B., Yun, J., Kim, M.S., Mendell, J.T., and Xie, Y.Identifying Argonaute binding sites in Caenorhabditis elegans using iCLIP. Broughton, J.P., and Pasquinelli, A.E.The protocol and data analysis are compared as well as actual data sets for different RBPs. This article compares discusses iCLIP in detail and compares and contrasts it to CLIP. Analysis of CLIP and iCLIP methods for nucleotide-resolution studies of protein-RNA interactions. Sugimoto, Y., Konig, J., Hussain, S., Zupan, B., Curk, T., Frye, M., and Ule, J. This is the paper that introduced iCLIP, it has an additional video detailing the protocol and some of the rational for each step. Konig, J., Zarnack, K., Rot, G., Curk, T., Kayikci, M., Zupan, B., Turner, D.J., Luscombe, N.M., and Ule, J. Currently, iCLIP is used to characterize the splicing activity of RBPs, for example hnRNP L (Rossbach et al., 2014) and can be used to map Argonaute-miRNA binding (Broughton and Pasquinelli, 2013). iCLIP was introduced relatively recently in 2011 (Konig et al., 2011). ICLIP has no significant disadvantages however, it requires a very detailed protocol and specialized data analysis tools to draw meaningful conclusions (Chen et al., 2014). Further, iCLIP doesn’t need to reverse transcribe over residual amino acids like HITS-CLIP, improving accuracy. Single nucleotide resolution is the defining advantage of iCLIP. The cDNA is then circularized meaning the nucleotide next to the adapter sequence is the last nucleotide before the RBP binding site (Huppertz et al., 2014). cDNA synthesis occurs from the adapter and is terminated at the polypeptide remaining on the RNA. The protein in the sample is then partially digest with proteinase K, leaving a polypeptide at the binding site. An adapter sequences is ligated to the 3’ ends of the RNAs. The protocol involves UV irradiation of living cells and immunoprecipitation of the protein of interest bound to RNAs. iCLIP is a refinement of CLIP that allows single-nucleotide resolution of RBP binding sites. ICLIP is not the latest Apple product you need to line for hours to own first, it stands for Individual-nucleotide resolution CLIP. ![]()
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