BRCA1-associated ATM activator 1 encoded by ubiquitously expressed BRAT1 gene, interacts with the tumor suppressing BRCA1 (breast cancer 1) protein and the ATM (ataxia telangiectasia mutated) protein. The protein is required for activation of ATM following ionizing radiation and may act by regulating dephosphorylation of ATM. The protein is thought to play a role in the DNA damage pathway regulated by BRCA1 and ATM.