Holliday junction recognition protein (HJURP) levels in breast cancer associate with both poor prognosis and an increased sensitivity to irradiation. Whilst, in part, this could be explained in relation to proliferation, it would not entirely account for the association with sensitivity to radiation. Thus, HJURP may have clinical potential as a marker of prognosis and radiation sensitivity; further validation with tissues from randomised controlled trials is needed. HJURP may represent the first in a class of proteins with roles in chromosome segregation and DNA repair that act as predictive biomarkers.