HIRA, or the Histone chaperone HIRA complex, is a crucial protein complex involved in chromatin remodeling and the regulation of gene expression. It plays a significant role in the deposition of the histone variant H3.3 into nucleosomes, which is essential for DNA replication, repair, and the maintenance of genomic integrity. HIRA is particularly important in embryonic stem cells, where it helps to control the activity of retrotransposons, thereby safeguarding the stability of the genome. Its function in these processes underscores the importance of HIRA in development and the prevention of diseases associated with genomic instability.