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As altered epigenetic regulation is a common feature of cancer, a greater understanding is required of the role of histone post-translational modifications as epigenetic regulators of changes in chromatin structure. Chromatin remodeling may also be important in the cellular response to DNA damage induced by anti-cancer drugs. A greater understanding of the nature of histone PTMs and resulting DNA damage in normal and cancerous tissues might indicate differences in the activity of enzymes involved in modifying histones, which could yield potential targets for cancer-specific therapy. Trichostatin A (TSA), a histone deacetylase inhibitor, promotes acetylation of histones and subsequently increases the accessibility to cellular machinery by the unraveling of DNA.
Using high-resolution 9.4T and 12T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers, the aim of this work was to characterise, in an unbiased fashion, the histone PTMs induced in histone H4 in response to treatment with TSA and certain environmental stimuli.
FT-ICR mass spectrometry is not well suited to online analysis, owing to the extended scan time required to achieve optimum resolving power. The TriVersa Nanomate enables fraction collection of the HPLC eluent allowing FT acquisition time to be decoupled from separation time. Following further sample cleanup, it proved possible to infuse unfractionated complex histone samples. The most abundant classes of histone present in the cell (H2A, H2B, H3, H4) were observed
The resolving power of FT-ICR permits the post-translational modification of H4 to be observed directly. It can be seen that in the case of cells treated with TSA, there was considerable variation in the acetylation state of histone H4. It was also possible to affect the acetylation state using certain environmental stimuli.