However, sequential NCL with multiple peptides allows for the preparation of fully synthetic histones, where multiple distinct histone PTMs can be incorporated throughout each histone.
Collectively, these data establish that multiple types of histone PTMs are involved in the DDR and, moreover, raise the prospect that additional DDR-responsive chromatin modifications await identification.
The diversity seen in terms of location on the nucleosome, genome localization and the cellular processes in which they are involved highlight the importance of histone PTMs to multiple fields of study including cell biology, epigenetics, development and cancer biology.
Different histone PTMs deposited across multiple residues on histone proteins generate a combinatorial pattern.
The function of histone PTMs in mammals remains uncertain because the multiple genes encoding each canonical histone, renders in vivo mutational analysis unfeasible in most instances.
Such cross-reactivity of histone antibodies at multiple sites is particularly concerning because the biological functions of histone PTMs are site-dependent and therefore confound the interpretation of antibody-dependent data.
With close to 200 sites and types of individual histone PTMs described, attention is now turning toward how multiple PTMs function together within the context of their physiological chromatin template (Ruthenburg et al., 2007; Taverna et al., 2007b).
A multiple reaction monitoring mass spectrometry assay was used to measure changes in abundance of several histone PTMs in frontal cortex from human donors affected with AD (n = 6) and age-matched, normal donors (n = 6).
With our multiple reaction monitoring (MRM) mass spectrometry method of PTM quantification, we were able to measure several histone PTMs in frontal cortex from humans.
Characterization of antibodies against histone PTMs used in the study was performed using a Histone Peptide Array (Active Motif, 13005).
