Polθ reverse transcribes RNA and promotes RNA-templated DNA repair

Sci Adv. 2021 Jun 11;7(24):eabf1771. doi: 10.1126/sciadv.abf1771. Print 2021 Jun.


Genome-embedded ribonucleotides arrest replicative DNA polymerases (Pols) and cause DNA breaks. Whether mammalian DNA repair Pols efficiently use template ribonucleotides and promote RNA-templated DNA repair synthesis remains unknown. We find that human Polθ reverse transcribes RNA, similar to retroviral reverse transcriptases (RTs). Polθ exhibits a significantly higher velocity and fidelity of deoxyribonucleotide incorporation on RNA versus DNA. The 3.2-Å crystal structure of Polθ on a DNA/RNA primer-template with bound deoxyribonucleotide reveals that the enzyme undergoes a major structural transformation within the thumb subdomain to accommodate A-form DNA/RNA and forms multiple hydrogen bonds with template ribose 2'-hydroxyl groups like retroviral RTs. Last, we find that Polθ promotes RNA-templated DNA repair in mammalian cells. These findings suggest that Polθ was selected to accommodate template ribonucleotides during DNA repair.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA / chemistry
  • DNA Repair
  • DNA-Directed DNA Polymerase* / chemistry
  • Deoxyribonucleotides
  • Humans
  • Mammals / genetics
  • RNA*
  • Ribonucleotides


  • Deoxyribonucleotides
  • Ribonucleotides
  • RNA
  • DNA
  • DNA-Directed DNA Polymerase