HIRA and thalassemia: While H3.3 is deposited at euchromatic regions by the chaperone Histone regulator A (HIRA) replication-independently20, 69, the death-associated protein (DAXX) together with the α-thalassemia and/or mental retardation X-linked syndrome protein (ATRX) mediates H3.3 deposition in pericentric heterochromatin and telomeric regions26, 27.