{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Histone H4 modifications—what we here refer to collectively as the H4C8 functional modalities—represent a central nexus for the regulation of chromatin structure and its many downstream cellular processes. Many studies have shown that acetylation events on the H4 tail, especially at lysine 16 (H4‐K16Ac), reduce chromatin fiber compaction and thereby promote an open, transcriptionally active chromatin state. This decompaction facilitates the binding and action of chromatin remodelers (for example, see"}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": ", and is dynamically regulated during the cell cycle as well as in response to cues such as circadian signals and metabolic changes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": " In contrast, methylation marks on histone H4—most notably the di‐ and trimethylation at lysine 20—provide specific docking sites for effector proteins that mediate critical responses such as DNA repair. For instance, methylated H4K20 is directly recognized by the tandem tudor domains of 53BP1, which is essential for proper double‐strand break repair."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Beyond these well‐characterized marks, H4 modifications also regulate the recruitment and activity of diverse chromatin‐modifying enzymes and reader proteins—such as SIRT1, TIP60, EED, BRD4, and others—that integrate a range of signals from oncogenic pathways to developmental and stress responses."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "10"}]}, {"type": "t", "text": " These regulatory interactions are critical for maintaining centromere identity, ensuring proper cell cycle progression, and safeguarding genomic stability in contexts as varied as tumor suppression, aging, and stem cell function."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "11", "end_ref": "13"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In summary, the functional repertoire of the histone H4 “C8” region—through its dynamic acetylation and methylation modifications—enables it to act as an integrative platform that modulates higher order chromatin folding, coordinates the recruitment of DNA repair and transcriptional machinery, and ultimately influences critical aspects of cell proliferation, differentiation, and genome maintenance."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "14", "end_ref": "16"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Michael Shogren-Knaak, Haruhiko Ishii, Jian-Min Sun, et al. 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