Investigating pathological epigenetic aberrations by epi-proteomics

Abstract

Epigenetics includes a complex set of processes that alter gene activity without modifying the DNA sequence, which ultimately determines how the genetic information common to all the cells of an organism is used to generate different cell types. Dysregulation in the deposition and maintenance of epigenetic features, which include histone posttranslational modifications (PTMs) and histone variants, can result in the inappropriate expression or silencing of genes, often leading to diseased states, including cancer. The investigation of histone PTMs and variants in the context of clinical samples has highlighted their importance as biomarkers for patient stratification and as key players in aberrant epigenetic mechanisms potentially targetable for therapy. Mass spectrometry (MS) has emerged as the most powerful and versatile tool for the comprehensive, unbiased and quantitative analysis of histone proteoforms. In recent years, these approaches—which we refer to as “epi-proteomics”—have demonstrated their usefulness for the investigation of epigenetic mechanisms in pathological conditions, offering a number of advantages compared with the antibody-based methods traditionally used to profile clinical samples. In this review article, we will provide a critical overview of the MS-based approaches that can be employed to study histone PTMs and variants in clinical samples, with a strong focus on the latest advances in this area, such as the analysis of uncommon modifications and the integration of epi-proteomics data into multi-OMICs approaches, as well as the challenges to be addressed to fully exploit the potential of this novel field of research.

Proteomics contributions to epigenetic drug discovery

“…Histone isolation is usually performed by purifying nuclei and further isolating histone bands for in‐gel digestion, or, alternatively, they can be further purified by acidic precipitation and subjected to in‐solution digestions [56]. Specific digestion strategies have been developed for MS‐based histone PTM analysis of histones (reviewed in [57]) to deal with the high number of lysines and arginines present in their sequences. In classical digestion workflows, these residues are recognized by the trypsin, generating peptides too short for MS analysis.…”