from Schizosaccharomyces pombe and MSX-DIA-based workflow for histone PTMs analysis with Skyline. Such workflow expands repertoire of quantified histone PTMs including rare co-occurring modifications which cannot be quantified using conventional antibody-based methodologies. We demonstrate that our heterochromatin preparations were enriched in repressive H3K9me2/3 as expected. Additionally we observe H3K9me2/3K14ac and H3K9me2/3S10ph suggesting that fraction of H3K9me2/3 co-exists with marks associated with open chromatin structures. We quantified histone PTMs associated with chromatin regions isolated mutant backgrounds derived by different routes, and demonstrate quantitative differences on histone PTMs level which are dependent on prior exposure to H3K9me2/3 suggesting epigenetic memory mechanism. Further results are going to be discussed.