The ETAA1 (Ewing's Tumor Associated Antigen 1) antibody is a tool used to study the ETAA1 protein, a key player in maintaining genomic stability. ETAA1 functions as a critical activator of the ATR kinase, a master regulator of the DNA damage response (DDR) pathway. It specifically interacts with replication protein A (RPA)-coated single-stranded DNA at stalled replication forks, recruiting ATR to sites of replication stress and facilitating its activation. This process ensures proper cell cycle checkpoint signaling, replication fork restart, and repair of DNA lesions. Dysregulation of ETAA1 has been linked to genomic instability, tumorigenesis, and chemoresistance in cancers such as Ewing sarcoma, glioblastoma, and hepatocellular carcinoma. ETAA1 antibodies, often developed in rabbit or mouse hosts, enable detection and functional analysis of ETAA1 through techniques like Western blotting, immunofluorescence, and co-immunoprecipitation. Researchers utilize these antibodies to investigate ETAA1's role in DDR mechanisms, its interplay with ATR/ATM pathways, and its potential as a therapeutic target or biomarker in cancer. Recent studies also explore ETAA1 variants associated with inherited syndromes featuring developmental defects and cancer predisposition.