R loops: from transcription byproducts to threats to genome stability

Mol Cell. 2012 Apr 27;46(2):115-24. doi: 10.1016/j.molcel.2012.04.009.


RNA:DNA hybrid structures known as R loops were thought to be rare byproducts of transcription. In the last decade, however, accumulating evidence has pointed to a new view in which R loops form more frequently, impacting transcription and threatening genome integrity as a source of chromosome fragility and a potential cause of disease. Not surprisingly, cells have evolved mechanisms to prevent cotranscriptional R loop formation. Here we discuss the factors and cellular processes that control R loop formation and the mechanisms by which R loops may influence gene expression and the integrity of the genome.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • DNA / chemistry
  • DNA Breaks
  • DNA Replication
  • Genomic Instability*
  • Models, Genetic
  • Mutagenesis
  • RNA / chemistry
  • Recombination, Genetic
  • Transcription, Genetic*


  • RNA
  • DNA