ACTR8 (actin-related protein 8) is a core component of the INO80 chr3 remodeling complex that plays essential roles in DNA repair, replication, and transcriptional regulation 12. The protein functions as a nucleosome recognition module, strongly preferring nucleosomes and H3-H4 tetramers over H2A-H2B dimers, which enables the INO80 complex to interact with chr3 substrates 3. Structurally, ACTR8 contains an ATP-bound actin fold with unique insertions that prevent polymerization and rigidify its domain architecture 3. The protein exhibits preferential binding to single-stranded DNA, with its ATP-binding pocket playing a regulatory role in DNA interactions 4. In DNA repair mechanisms, ACTR8 is required for efficient replication restart after replication stress and protection of stalled replication forks from collapse 1. The protein undergoes ATM- and ATR-regulated phosphorylation following DNA damage, which attenuates its interaction with INO80 and prevents excessive loading of repair factors, thereby maintaining DNA repair fidelity and preventing chromosome 3 5. Additionally, ACTR8 knockout has been associated with enhanced sensitivity to immune cell cytotoxicity in cancer contexts 6.