Mitochondrial DNA, partially associated with mitochondrial inner membrane, is at the heart of ROS production thus, relative to boring, mtDNA contains high levels of oxidative damage. Many of these damages are Mutagenic and cause disease. Located on the inner membrane, base excision repair pathway is a major defense mechanism against oxidative damage. EXOG, a membrane-bound 5'-exo/endonuclease, is crucial for mtDNA repair. Depletion of EXOG causes accumulation of DNA damage in the mitochondria, but not in the nucleus, increases oxidative stress and mitochondrial dysfunction and leads to cell death. We propose that N-terminal transmembrane domain of EXOG anchors BER repairosome to mitochondrial inner membrane and modulates crucial 5'exonuclease activity of the enzyme. Because preservation of mtDNA integrity in cancer cells is a key for cancer progression, we aim to develop inhibitors to specifically halt function of EXOG and increase sensitivity to traditional chemotherapeutics.