Endonuclease G promotes mitochondrial genome cleavage and replication

Abstract

Endonuclease G (EndoG) is a nuclear-encoded endonuclease, mostly localised in mitochondria. In the nucleus EndoG participates in site-specific cleavage during replication stress and genome-wide DNA degradation during apoptosis. However, the impact of EndoG on mitochondrial DNA (mtDNA) metabolism is poorly understood. Here, we investigated whether EndoG is involved in the regulation of mtDNA replication and removal of aberrant copies. We applied the single-cell mitochondrial Transcription and Replication Imaging Protocol (mTRIP) and PCR-based strategies on human cells after knockdown/knockout and re-expression of EndoG. Our analysis revealed that EndoG stimulates both mtDNA replication initiation and mtDNA depletion, the two events being interlinked and dependent on EndoG's nuclease activity. Stimulation of mtDNA replication by EndoG was independent of 7S DNA processing at the replication origin. Importantly, both mtDNA-directed activities of EndoG were promoted by oxidative stress. Inhibition of base excision repair (BER) that repairs oxidative stress-induced DNA damage unveiled a pronounced effect of EndoG on mtDNA removal, reminiscent of recently discovered links between EndoG and BER in the nucleus. Altogether with the downstream effects on mitochondrial transcription, protein expression, redox status and morphology, this study demonstrates that removal of damaged mtDNA by EndoG and compensatory replication play a critical role in mitochondria homeostasis.

Involvement of the mitochondrial nuclease EndoG in the regulation of cell proliferation through the control of reactive oxygen species

“…5 A). Due to the fact that the METC activity is a major source of ROS and that EndoG regulates mtDNA replication and abundance [ 15 , 28 ], which contains genes codifying for several components of the METC, we checked the expression of several mitochondrial- and nuclear-encoded METC complex subunits in Endog +/+ and Endog −/− fibroblasts and observed no differences ( Fig. 5 B).…”

The Better Survival of MSI Subtype Is Associated With the Oxidative Stress Related Pathways in Gastric Cancer

“…ENDOG, the Endonuclease G, was the nuclear encoded gene and its corresponding protein mainly localized in mitochondria. This protein is capable of initiating the mitochondrial DNA replication by generating the RNA primers (51,52). On the one hand, it was the downstream effector of caspase-3 and facilitated the Myc-induced genetic instability and apoptosis (53,54).…”

On the epigenetic role of guanosine oxidation

“…Consistently, 8-oxo-dG adducts localize preferentially on fragmented mtDNA upon oxidative stress [202]. High susceptibility of mtDNA to strand breaks and Endonuclease G-mediated degradation was observed upon oxidative stress and proposed as a mechanism for protecting from deleterious accumulation of mutated mitochondrial genomes [203]. Intriguingly, recent works have shown that oxidative stress may also inhibit Endonuclease G activity, thus preventing mtDNA degradation and affecting cell death process [204].…”