A Derivatization-Free Parallel Reaction Monitoring-Based Proteomics Workflow for Quantitative, Site-Specific Analysis of Histone Post-Translational Modifications
A derivatization-free parallel reaction monitoring (PRM) workflow for robust, quantitative, and site-specific analysis of major histone H3 and H4 PTMs, enabling reliable validation of selected histone PTMs.
Abstract
Histone post-translational modifications (PTMs) are key regulators of chromatin architecture and gene expression. Although mass spectrometry (MS)-based data-independent acquisition (DIA) pipelines for histone PTM quantification are available, multiplexed targeted assays remain underdeveloped. Here, we present a derivatization-free parallel reaction monitoring (PRM) workflow for robust, quantitative, and site-specific analysis of major histone H3 and H4 PTMs. We employed highly efficient ArgC digestion to generate peptides of optimal length for liquid chromatography-tandem mass spectrometry (LC–MS/MS) while preserving endogenous PTMs, and we optimized chromatographic conditions to achieve isobaric separation and stable retention times. Co-eluting isobaric PTM species were confidently distinguished using site-specific fragment ions. The resulting PRM method enabled sensitive and reproducible detection of histone PTM isoforms across diverse biological systems. To illustrate its utility, we analyzed PTM dynamics in cells expressing histone H3.3 lysine-to-methionine substitutions and in cells treated with the histone deacetylase inhibitor entinostat, yielding results that correlated strongly with antibody-based readouts. This PRM platform provides a complementary, targeted approach to current chemical derivatization–based methods, enabling reliable validation of selected histone PTMs.
Mass spectrometry-based chemical proteomics is a powerful method to analyze proteins labelled by small molecules to identify protein targets of active compounds and to profile protein post-translational modifications. The throughput and high protein input for chemical proteomics workflows has been often a limiting factor for application of the technology for specialized and difficult to culture cell lines. The high protein input was necessary to gain significant difference of noise to signal ratio in proteomics readout. Here, we describe a general chemical proteomics workflow, which is performed in 96-well plate and necessitate only 25 μg of protein input to profile post-translationally modified proteins including abundant O-GlcNAcylated proteins as well as low abundant AMPylated proteins. The workflow integrates advances in Cu(I)-catalyzed azide-alkyne cycloaddition to minimize chemical side-reactivity of the ‘click reaction’ and data-independent acquisition mode during LC-MS/MS measurement. An iterative optimization of protein clean-up on carboxylate-coated paramagnetic beads led to significant saving of the beads usage and lowers the unspecific protein background that resulted in sensitivity gain.
Liu Zang, Jonas Grandke, Jana Richter et al.· bioRxiv· 0 citations
Improvements enabling quantification of site-specific modifications, including post-translational modifications and covalent compound-protein interactions spanning diverse pathways are described.
Steven R. Shuken, Geordon A. Frere, Charlotte R. Beard et al.· Nature Communications· 0 citations
RNA modifications regulate RNA stability, translation, stress responses, and disease processes, yet their function remains poorly understood due to technical limitations in sequence analysis. Here, we present an RNA-specific isobaric tandem mass tagging (RMT) platform for omic-scale quantitative mapping of RNA modifications. The platform combines RNA-specific tags adapted from proteomics with an end-to-end workflow spanning sample preparation through data processing. Validation using synthetic oligonucleotides and total tRNA from Pseudomonas aeruginosa yielded reproducible quantification, with coefficients of variation below 5%. Together with nucleobase fragment analysis, we identified and quantified 24 RNA modifications in PA14 tRNAs, including previously undescribed m2A38 and Gm/Cm39, and assigned their corresponding writer enzymes. Further analyses of tRNAs from writer knockout strains and stressed cells revealed dynamic modification patterns, modification interdependencies, and their potential roles in stress adaptation. This method provides a robust, cost-effective platform for quantitative RNA modification mapping, enabling deeper biological insights. The locations and levels of RNA modifications are key to understanding their biological functions. Here, the authors develop proteomics-style, RNA-specific isobaric tandem mass tags for quantitative RNA modification mapping by mass spectrometry, revealing condition-dependent changes and interdependencies among modification pathways.
