BRCA2 deficiency reveals that oxidative stress impairs RNaseH1 function to cripple mitochondrial DNA maintenance

• Published in: Cell reports (Cambridge) 2021-08, Vol.36 (5), p.109478-109478, Article 109478
• Main Authors: Renaudin, Xavier, Lee, Miyoung, Shehata, Mona, Surmann, Eva-Maria, Venkitaraman, Ashok R.
• Format: Article
• Language: English
• Subjects: BRCA2; BRCA2 Protein - deficiency; BRCA2 Protein - metabolism; cancer; DNA Glycosylases - metabolism; DNA Helicases - metabolism; DNA Replication; DNA, Mitochondrial - chemistry; DNA, Mitochondrial - genetics; Female; Guanine - analogs & derivatives; Guanine - metabolism; HeLa Cells; Humans; Mitochondria - metabolism; Mitochondria - pathology; mitochondrial DNA replication; Multifunctional Enzymes - metabolism; neurodegeneration; Oxidative Stress; PRPF8; R-Loop Structures; R-loops; Ribonuclease H - metabolism; RNA Helicases - metabolism; RNA-Binding Proteins - metabolism; RNaseH1; SETX
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2021.109478

Oxidative stress is a ubiquitous cellular challenge implicated in aging, neurodegeneration, and cancer. By studying pathogenic mutations in the tumor suppressor BRCA2, we identify a general mechanism by which oxidative stress restricts mitochondrial (mt)DNA replication. BRCA2 inactivation induces R-loop accumulation in the mtDNA regulatory region and diminishes mtDNA replication initiation. In BRCA2-deficient cells, intracellular reactive oxygen species (ROS) are elevated, and ROS scavengers suppress the mtDNA defects. Conversely, wild-type cells exposed to oxidative stress by pharmacologic or genetic manipulation phenocopy these defects. Mechanistically, we find that 8-oxoguanine accumulation in mtDNA caused by oxidative stress suffices to impair recruitment of the mitochondrial enzyme RNaseH1 to sites of R-loop accrual, restricting mtDNA replication initiation. Thus, oxidative stress impairs RNaseH1 function to cripple mtDNA maintenance. Our findings highlight a molecular mechanism that links oxidative stress to mitochondrial dysfunction and is elicited by the inactivation of genes implicated in neurodegeneration and cancer. [Display omitted] •BRCA2-deficient cells accumulate mtDNA R-loops due to oxidative stress•This stress creates 8-oxoguanine lesions impairing RNaseH1 recruitment to mtDNA•RNaseH1 impairment triggers R-loop formation and restricts mtDNA replication•Other sources of oxidative stress also cripple mtDNA maintenance via this mechanism Oxidative stress ubiquitously challenges cellular homeostasis. Renaudin et al. show that oxidative stress impairs RNase H1 recruitment via 8-oxoguanine accumulation, eliciting unscheduled RNA-DNA hybrids (R-loops) that block mtDNA replication. These findings define the mechanism underlying a specific molecular consequence of oxidative stress, with links to aging-related human diseases.