FIGURE 4.

Overview of histone dynamics throughout the cell cycle. Replication-coupled H3.1 and H3.2 are deposited by CAF-1 during DNA replication. New histones transiently lack PTMs on H4K20 (blue). Meanwhile, preexisting histone marks become diluted, as old histones are recycled on the two new DNA strands. As the cell progress into G₂, chromatin matures, and marks associated with active transcription (green) are reset via the transcriptional process. In contrast, repressive marks (red) begin to epigenetically spread from old to new histones. As the cell transitions from G₂ to M, histones are transiently phosphorylated (yellow), a mark that is thought to recruit proteins that aid in condensation. HJURP deposits the H3 centromeric variant CENP-A at the end of the cell cycle/beginning of the next one. The RI H3.3 variant is deposited at transcribed genes by the HIRA histone chaperone complex and over repetitive DNA regions by the ATRX–DAXX complex in interphase. Relative PTM abundance is denoted by the height of the curve and based on data from references provided in the main text. For simplicity, new histones are indicated by the H4K20me0 mark, but also contain H3K9me1 and H4K5/K12ac.