Simple label-free fluorescence detection of apurinic/apyrimidinic endonuclease 1 activity and its inhibitor using the abasic site-binding fluorophore

Abstract

Apurinic/apyrimidinic endonuclease 1 (APE1) plays crucial role in DNA repair, which cleaves the abasic site (AP site) to facilitate the DNA repair process. APE1 is overexpressed in several cancers, and it has been demonstrated to be a promising target for anticancer drugs. Thus, development of a method for the detection of APE1 activity and screening of its inhibitors is important and highly desirable for cancer diagnosis and therapy. In this study, we report a simple and label-free fluorescence detection method for APE1 activity using an AP site-binding dye (2-amino-5,6,7-trimethyl-1,8-naphthyridine, ATMND) as a signal indicator. The fluorescence of ATMND was quenched after inserting ATMND into the AP site with a C base at the opposite position. The APE1-catalyzed cleavage of the AP site resulted in the release of the bound ATMND, and the quenched fluorescence of ATMND recovered. The label-free strategy makes this method convenient and easy to manipulate. The proposed method exhibits a good sensitivity, and we have also employed it to evaluate the inhibition effect of a drug on the APE1 activity. This approach holds potential applications in APE1-related cancer diagnosis and anticancer drug screening.