RHON1 Co-transcriptionally Resolves R-Loops for Arabidopsis Chloroplast Genome Maintenance

Cell Rep. 2020 Jan 7;30(1):243-256.e5. doi: 10.1016/j.celrep.2019.12.007.

Abstract

Preventing transcription-replication head-on conflict (HO-TRC)-triggered R-loop formation is essential for maintaining genome integrity in bacteria, plants, and mammals. The R-loop eraser RNase H can efficiently relax HO-TRCs. However, it is not clear how organisms resist HO-TRC-triggered R-loops when RNase H proteins are deficient. By screening factors that may relieve R-loop accumulation in the Arabidopsis atrnh1c mutant, we find that overexpression of the R-loop helicase RHON1 can rescue the defects of aberrantly accumulated HO-TRC-triggered R-loops co-transcriptionally. In addition, we find that RHON1 interacts with and orchestrates the transcriptional activity of plastid-encoded RNA polymerases to release the conflicts between transcription and replication. Our study illustrates that organisms employ multiple mechanisms to escape HO-TRC-triggered R-loop accumulation and thus maintain genome integrity.

Keywords: R-loops; RHON1; RNase H1; head-on; organelle-encoded RNA polymerase; transcription-replication conflicts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics*
  • DNA Replication / genetics
  • DNA, Ribosomal / genetics
  • DNA-Directed RNA Polymerases / metabolism
  • Genome, Chloroplast*
  • Genomic Instability
  • Mutation / genetics
  • Protein Binding / genetics
  • R-Loop Structures / genetics*
  • RNA-Binding Proteins / genetics*
  • Transcription, Genetic*

Substances

  • Arabidopsis Proteins
  • DNA, Ribosomal
  • RHON1 protein, Arabidopsis
  • RNA-Binding Proteins
  • DNA-Directed RNA Polymerases