Nucleosome and histone modification during yeast meiosis

During meiosis to form gametes or spores, chromosomes undergo dramatic compaction, which might be expected to result in tighter nucleosome packing. Here we investigate the impact of meiotic genome compaction on individual nucleosomal positions and modification states for every nucleosome in Saccharomyces cerevisiae. Surprisingly, we found that nucleosomes increased their spacing during the stationary phase that precedes meiosis, but then precisely returned to their original positions throughout meiosis, maintaining their phasing and width, including the maintenance of nucleosome-free regions. Histone modification states (H3K9Ac, H3K4Me3, H3K36Me3, and H3K79Me3) were investigated for individual nucleosome positions.