Histone Cell Cycle Regulation Defective Homolog A (HIRA)

HIRA encodes a histone chaperone that preferentially places the variant histone H3.3 in nucleosomes. Orthologs of this gene in yeast, flies, and plants are necessary for the formation of transcriptionally silent heterochomatin. This gene plays an important role in the formation of the senescence-associated heterochromatin foci. These foci likely mediate the irreversible cell cycle changes that occur in senescent cells. It is considered the primary candidate gene in some haploinsufficiency syndromes such as DiGeorge syndrome, and insufficient production of the gene may disrupt normal embryonic development.The protein product of the TUPLE1 gene contains WD40 domains, motifs thought to be involved in protein-protein interactions.Expressed at high levels in kidney, pancreas and skeletal muscle and at lower levels in brain, heart, liver, lung, and placenta.