The HIRA gene encodes a histone chaperone that has transcription factor activity and is required for the periodic repression of histone gene transcription during the cell cycle.  The HIRA protein is involved in DNA replication-independent nucleosome assembly, the regulation of chromatin silencing, and the formation of senescence-associated heterochromatin foci.  By carrying out its function, the HIRA protein is believed to be involved in the biological processes of gastrulation, differentiation of muscle cells and osteoblasts, and anatomical structure morphogenesis.