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

Cell Rep. 2021 Aug 3;36(5):109478. doi: 10.1016/j.celrep.2021.109478.

Abstract

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.

Keywords: BRCA2; PRPF8; R-loops; RNaseH1; SETX; cancer; mitochondrial DNA replication; neurodegeneration; oxidative stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • BRCA2 Protein / deficiency*
  • BRCA2 Protein / metabolism
  • 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
  • Multifunctional Enzymes / metabolism
  • Oxidative Stress*
  • R-Loop Structures
  • RNA Helicases / metabolism
  • RNA-Binding Proteins / metabolism
  • Ribonuclease H / metabolism*

Substances

  • BRCA2 Protein
  • BRCA2 protein, human
  • DNA, Mitochondrial
  • Multifunctional Enzymes
  • PRPF8 protein, human
  • RNA-Binding Proteins
  • 8-hydroxyguanine
  • Guanine
  • Ribonuclease H
  • DNA Glycosylases
  • oxoguanine glycosylase 1, human
  • SETX protein, human
  • DNA Helicases
  • RNA Helicases