Mass Spectrometry-Based Methodology for Identification of Native Histone Variant Modifications From Mammalian Tissues and Solid Tumors.

Histone posttranslational modifications (PTMs) are key epigenetic marks involved in gene silencing or activation. Histone modifications impact chromatin organization and transcriptional processes through the changes in charge density between histones and DNA. They also serve as recognition and binding sites for specific binding proteins. Histone tails and globular cores contain many basic amino acid residues, which are subject to various dynamic modifications, making the modification repertoire extremely diverse. Consequently, determination of histone PTM identity and quantity has been a challenging task. In recent years, mass spectrometry-based methods have proven useful in histone PTM characterization. This chapter provides a brief overview of these methods and describes the approach to analyze the PTMs of the histone variant CENP-A, essential for the cell cycle progression, when present in minute amounts from tumor and mammalian tissues. Because this method does not rely on antibody-based immunopurification, we anticipate that these tools could be readily adaptable to the investigation to other histone variants in a range of mammalian tissues and solid tumors.