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

• Published in: Nucleic acids research 2022-04, Vol.50 (7), p.3911-3921
• Main Authors: Schaub, Jeffrey M, Soniat, Michael M, Finkelstein, Ilya J
• Format: Article
• Language: English
• Subjects: 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; Genome Integrity, Repair and; Replication Protein A - genetics; Replication Protein A - metabolism
• ISSN: 0305-1048; 1362-4962
• 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.