AUF1 recognizes 8-oxo-guanosine embedded in DNA and stimulates APE1 endoribonuclease activity

Aims: The existence of modified rNMPs embedded in genomic DNA, as a consequence of oxidative stress conditions, including 8-oxo-guanosine and ribose monophosphate abasic site (rAP), has been recently highlighted by several works including ours. Although the activity of APE1, a key enzyme of the base excision repair pathway, in the repair of rAP sites results as efficient as the canonical deoxyribose monophosphate abasic sites (dAP), its incision repair activity on 8-oxo-guanosine is very weak. The aims of this work were to: i) identify proteins able to specifically bind 8-oxo-guanosine embedded in DNA and promote APE1 endoribonuclease on this lesion and ii) characterize the molecular and biological relevance of this interaction using human cancer cell lines. Results: By using an unbiased proteomic approach, we discovered that AUF1 actively recognizes 8-oxo-guanosine and stimulates the APE1 enzymatic activity on this DNA lesion. By using orthogonal approaches, we found that: i) the interaction between AUF1 and APE1 is modulated by H2O2-treatment; ii) depletion of APE1 and AUF1 causes the accumulation of single- and double- strand breaks; iii) both proteins are involved in modulating the formation of DNA:RNA hybrids. Innovation: These data establish unexpected functions of AUF1 in modulating genome stability, and improve our knowledge of APE1 biology with respect to 8-oxo-guanosine embedded in DNA. Conclusions: By showing a novel function of AUF1, our findings shed new light on the process of maintenance of genome stability in mammalian cells towards oxidative stress-related damages.