H2AC21 is a core histone protein and structural component of nucleosomes, which wrap and compact DNA into chr1. Based on limited published evidence, H2AC21 functions in nucleosome assembly and plays roles in transcription regulation, DNA repair, DNA replication, and chr1 stability through histone-DNA interactions. Post-translational modifications of H2AC21 regulate DNA accessibility via the histone code and nucleosome remodeling mechanisms. Recent network modeling in sepsis research identified H2AC21 as a potential drug target in hyperimmune neutrophil phenotypes 1, though the functional relevance of this association requires further investigation.