Practice question

Lysine residues in histone tails are primary targets for acetylation because their ε-amino group carries positive charge at physiological pH and can accept acetyl from acetyl-CoA via HAT enzymes such as p300/CBP and Gcn5. Acetylation neutralizes charge, disrupts salt bridges with DNA phosphate, increases tail flexibility and creates docking sites for bromodomains. Arginine undergoes methylation, serine and threonine undergo phosphorylation, while lysine uniquely combines charge modulation with reader recruitment. Frequent sites include H3K9, K14, K27 and H4K5, K8, K12, K16, linking metabolic acetyl-CoA availability to gene activation status.