The H2AJ antibody targets histone H2A.J, a variant of the core histone H2A involved in chromatin organization and gene regulation. Histone H2A.J, encoded by the H2AJ gene in humans, is distinguished by its unique C-terminal tail, which replaces the canonical SQ motif with a polyadenylation signal. This variant accumulates in aging cells and senescent cells, where it is linked to altered chromatin structure and transcription of pro-inflammatory genes. Studies suggest H2A.J plays roles in DNA damage response, cellular senescence, and aging-associated processes by modulating chromatin accessibility and recruiting specific regulatory proteins. The H2AJ antibody is a critical tool for detecting H2A.J localization and expression in immunofluorescence, Western blotting, or chromatin immunoprecipitation (ChIP) assays. Its development has advanced research into age-related diseases, cancer biology, and epigenetic mechanisms, particularly in understanding how histone variants contribute to transcriptional dysregulation during senescence. Researchers use this antibody to explore H2A.J's interaction with repair machinery or inflammatory pathways, offering insights into therapeutic strategies targeting senescence-associated pathologies.