BRCA1 interacts in vivo with a novel protein, BACH1, a member of the DEAH 
helicase family. BACH1 binds directly to the BRCT repeats of BRCA1. A BACH1 
derivative, bearing a mutation in a residue that was essential for catalytic 
function in other helicases, interfered with normal double-strand break repair 
in a manner that was dependent on its BRCA1 binding function. Thus, BACH1/BRCA1 
complex formation contributes to a key BRCA1 activity. In addition, germline 
BACH1 mutations affecting the helicase domain were detected in two early-onset 
breast cancer patients and not in 200 matched controls. Thus, it is conceivable 
that, like BRCA1, BACH1 is a target of germline cancer-inducing mutations.