Polymerase θ-helicase efficiently unwinds DNA and RNA-DNA hybrids

J Biol Chem. 2018 Apr 6;293(14):5259-5269. doi: 10.1074/jbc.RA117.000565. Epub 2018 Feb 14.

Abstract

POLQ is a unique multifunctional replication and repair gene that encodes for a N-terminal superfamily 2 helicase and a C-terminal A-family polymerase. Although the function of the polymerase domain has been investigated, little is understood regarding the helicase domain. Multiple studies have reported that polymerase θ-helicase (Polθ-helicase) is unable to unwind DNA. However, it exhibits ATPase activity that is stimulated by single-stranded DNA, which presents a biochemical conundrum. In contrast to previous reports, we demonstrate that Polθ-helicase (residues 1-894) efficiently unwinds DNA with 3'-5' polarity, including DNA with 3' or 5' overhangs, blunt-ended DNA, and replication forks. Polθ-helicase also efficiently unwinds RNA-DNA hybrids and exhibits a preference for unwinding the lagging strand at replication forks, similar to related HELQ helicase. Finally, we find that Polθ-helicase can facilitate strand displacement synthesis by Polθ-polymerase, suggesting a plausible function for the helicase domain. Taken together, these findings indicate nucleic acid unwinding as a relevant activity for Polθ in replication repair.

Keywords: DNA damage; DNA damage response; DNA enzyme; DNA helicase; DNA polymerase; DNA repair; DNA replication; alternative end-joining; double-strand break repair; helicase; microhomology-mediated end-joining; polymerase; replication fork repair.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Crystallography, X-Ray
  • DNA / metabolism
  • DNA Breaks, Double-Stranded
  • DNA End-Joining Repair / physiology
  • DNA Helicases / metabolism*
  • DNA Replication / physiology
  • DNA, Single-Stranded / metabolism
  • DNA-Directed DNA Polymerase / metabolism*
  • DNA-Directed DNA Polymerase / physiology
  • Humans
  • Nucleic Acid Hybridization
  • Protein Binding
  • Recombination, Genetic / genetics

Substances

  • DNA, Single-Stranded
  • DNA
  • DNA polymerase theta
  • DNA-Directed DNA Polymerase
  • DNA Helicases

Associated data

  • PDB/5AGA
  • PDB/2P6R
  • PDB/2VA8