Polymerase theta-helicase promotes end joining by stripping single-stranded DNA-binding proteins and bridging DNA ends

Nucleic Acids Res. 2022 Apr 22;50(7):3911-3921. doi: 10.1093/nar/gkac119.

Abstract

Homologous recombination-deficient cancers rely on DNA polymerase Theta (Polθ)-Mediated End Joining (TMEJ), an alternative double-strand break repair pathway. Polθ is the only vertebrate polymerase that encodes an N-terminal superfamily 2 (SF2) helicase domain, but the role of this helicase domain in TMEJ remains unclear. Using single-molecule imaging, we demonstrate that Polθ-helicase (Polθ-h) is a highly processive single-stranded DNA (ssDNA) motor protein that can efficiently strip Replication Protein A (RPA) from ssDNA. Polθ-h also has a limited capacity for disassembling RAD51 filaments but is not processive on double-stranded DNA. Polθ-h can bridge two non-complementary DNA strands in trans. PARylation of Polθ-h by PARP-1 resolves these DNA bridges. We conclude that Polθ-h removes RPA and RAD51 filaments and mediates bridging of DNA overhangs to aid in polymerization by the Polθ polymerase domain.

Publication types

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

MeSH terms

  • DNA / chemistry
  • DNA Breaks, Double-Stranded
  • DNA End-Joining Repair*
  • DNA Helicases / genetics
  • DNA, Single-Stranded / genetics
  • DNA-Binding Proteins* / genetics
  • DNA-Binding Proteins* / metabolism
  • Replication Protein A / genetics
  • Replication Protein A / metabolism

Substances

  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • Replication Protein A
  • DNA
  • DNA Helicases