Project description:Despite the overwhelming information about sRNAs, one of the biggest challenges in the sRNA field is characterizing sRNA targetomes. Thus, we develop a novel method to identify RNAs that interact with a specific sRNA, regardless of the type of regulation (positive or negative) or targets (mRNA, tRNA, sRNA). This method is called MAPS: MS2 affinity purification coupled with RNA sequencing. As proof of principle, we identified RNAs bound to RybB, a well-characterized E. coli sRNA. Identification of RNAs co-purified with MS2-RybB in a rne131 ΔrybB strain. RybB (without MS2) was used as control
Project description:Despite the overwhelming information about sRNAs, one of the biggest challenges in the sRNA field is characterizing sRNA targetomes. Thus, we develop a novel method to identify RNAs that interact with a specific sRNA, regardless of the type of regulation (positive or negative) or targets (mRNA, tRNA, sRNA). This method is called MAPS: MS2 affinity purification coupled with RNA sequencing. As proof of principle, we identified RNAs bound to RyhB, a well-characterized E. coli sRNA. Identification of RNAs co-purified with MS2-RyhB in a rne131 ?ryhB strain. RyhB (without MS2) was used as control
Project description:During ribosomal and transfer RNA maturation, external transcribed spacer (ETS) and internal transcribed spacer (ITS) sequences are excised and, as non-functional by-products, are rapidly degraded. The 3’ETS of the glyW-cysT-leuZ polycistronic tRNA precursor was highly and specifically enriched by co-purification with at least two different small regulatory RNAs (sRNAs), RyhB and RybB. Both sRNAs were shown to base pair with the same region in the 3’ETS of leuZ (3’ETSleuZ). Disrupting the pairing by mutating 3’ETSleuZ significantly increased the activity of sRNAs, even under non-inducing conditions. Our results indicate that 3’ETSleuZ prevents sRNA-dependent remodeling of tricarboxylic acid (TCA) cycle fluxes and increases antibiotic sensitivity when sRNAs are transcriptionally repressed. This suggests that 3’ETSleuZ functions as a sponge to absorb transcriptional noise from repressed sRNAs. Finally, the fact that RybB and MicF sRNAs are co-purified with ITSmetZ-metW and ITSmetW-metV strongly suggests a much broader phenomenon. Identification of sRNAs co-purified with MS2-ITSmetZW and MS2-ITSmetWV. ITSmetZW and ITSmetWV (without MS2) were used as control
Project description:Over the past few decades cross-linking mass spectrometry (XLMS) has become a powerful tool for identification of protein-protein interactions and for gaining insight into the structures of proteins in living cells, tissues, and organelles. The development of new crosslinkers, enrichment strategies and data acquisition methods led to the establishment of numerous new software tools specifically for the analysis and interpretation of cross-linking data. We previously published one of these tools called MS Annika, a cross-linking search engine which can accurately identify cross-linked peptides in MS2 spectra from a variety of different MS-cleavable crosslinkers. In this publication we present an updated MS Annika and a new search algorithm that additionally supports processing of data from MS2-MS3-based approaches and identification of peptides from MS3 spectra. In the new MS2-MS3 search algorithm, MS3 spectra are matched to their corresponding precursor doublet peak in the MS2 scan to identify the crosslink modification and the monoisotopic peptide mass. This information is then used to adjust the MS3 spectra for search with MS Amanda, our in-house developed peptide search engine, to identify the cross-linked peptides. Peptides that are identified in the MS2 scan and one or more of the associated product MS3 scans are re-scored with a novel scoring function to reflect the increased confidence. Finally, the detected cross-links are validated by estimating the false discovery rate (FDR) using a target-decoy approach. We evaluated the MS3-search-capabilities of MS Annika on five different datasets covering a variety of experimental approaches and compared it to XlinkX and MaXLinker, two other cross-linking search engines that support MS3 crosslink identification. Three of the datasets were benchmark datasets of synthetic peptides that allow calculation of an experimentally validated FDR, and we show that MS Annika detects up to 4 times more true unique crosslinks than MaXLinker and up to 35% more than XlinkX while simultaneously yielding less false positive hits and therefore a more accurate FDR than the other two search engines. Additionally, for the other two datasets we could show that MS Annika finds between 74% to 2.5 times more crosslinks at 1% estimated FDR and reveals protein-protein interactions that are not detected by either XlinkX or MaXLinker.
Project description:Comprehensive mass spectrometry (MS)-based proteomics is now feasible, but reproducible and multiplexed quantification remains challenging especially for analysis of post-translational modifications (PTMs), such as phosphorylation. Here we compared the most popular quantification techniques for phosphoproteomics in context of cell-signaling studies: label-free quantification (LFQ), stable isotope labeling by amino acids in cell culture (SILAC) and MS2- and MS3-measured tandem mass tags (TMT). In a mixed species comparison with fixed phosphopeptide-ratios, we found LFQ and SILAC to be the most accurate techniques. MS2-based TMT suffered from substantial ratio compression, which MS3-based TMT could partly rescue. However, when analyzing phosphoproteome changes in the DNA damage response (DDR), we found that MS3-based TMT was outperformed by MS2-based TMT as it identified most significantly regulated phosphopeptides due to its higher precision and higher number of identifications. Finally, we show that the high accuracy of MS3-based TMT is crucial for determination of phosphorylation site stoichiometry using a novel multiplexing-dependent algorithm.
Project description:We Have a pancreas MS2/MS3 dataset in this project. We predict all spectra in the datasets via Prosit then rescore. We have 100% FDR maxquant search results, and using percolator we get 1%FDR filtered results with andromeda Scores and another with features extracted from Prosit predictions.
Project description:MS2-affinity purification coupled with RNA sequencing (MAPS) reveals S. aureus RsaG sRNA targetome. Affinity purification of in vivo regulatory complexes coupled with high throughput RNA sequencing methodology or MAPS standing for “MS2 affinity purification coupled to RNA".
Project description:RNA delivery is a method of choice to achieve transient gene expression for research and in cell- or gene-based therapies. To improve retroviral transfer, we designed a dimerization-independent MS2-driven packaging system using MS2-retrovirus chimeras. We delivered RUNX2- or DLX5-mRNA into primary human bone-marrow mesenchymal-stem-cells. We used microarrays to detail the global programme of gene expression confirming the effects of pro-osteogenic genes transduced by MS2 chimeric lentiviral particles.