Practice question

Among histones, H4 shows extreme evolutionary conservation from yeast to humans with only one or two amino acid differences, reflecting severe functional constraint. H4 intimately contacts DNA at fourteen arginine anchor points, participates in H3-H4 tetramer core formation and interacts with neighboring nucleosomes via basic tail binding to acidic patch of H2A. Its N-terminal tail modifications especially acetylation at lysine 16 strongly influence 30 nanometer fiber inhibition and dosage compensation. Mutations in H4 lethal because assembly fails. H1 evolves fastest due to variable C-terminus, while H3 also conserved but less than H4.