Practice question

Histone tails contain hydroxyl-bearing residues capable of phospho-esterification. Serine and threonine side chains are phosphorylated by serine-threonine kinases such as Aurora B, MSK1, PKA and CK2, transferring γ-phosphate of ATP to hydroxyl oxygen. This introduces bulky negative charge, altering tail conformation and electrostatic interaction with DNA or reader proteins. Examples include H3S10, S28, T3 and H3T11 regulation during mitosis, DNA damage and transcriptional activation. Lysine and arginine cannot be phosphorylated in this context; they instead undergo acetylation and methylation, making phosphorylation specific to serine, threonine and tyrosine.