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Srs2 mediates PCNA-SUMO-dependent inhibition of DNA repair synthesis

Peter Burkovics1, Marek Sebesta, Alexandra Sisakova

  • 1National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic.

The EMBO Journal
|February 12, 2013
PubMed

Insights

SUMOylated PCNA (S-PCNA) and Srs2 limit DNA repair synthesis extension, preventing hazardous crossover resolution. This mechanism, involving Srs2

Area of Science:

  • Molecular Biology
  • Genetics
  • DNA Repair

Background:

  • DNA replication must be completed despite challenges like fork progression problems or DNA damage.
  • Proliferating Cell Nuclear Antigen (PCNA) and its modifications act as molecular switches, directing distinct DNA repair pathways.
  • In yeast, SUMOylated PCNA (S-PCNA) recruits Srs2 to replication sites, where Srs2 disassembles Rad51 filaments to inhibit homologous recombination (HR).

Purpose of the Study:

  • To investigate the role of S-PCNA and Srs2 in regulating DNA repair synthesis and homologous recombination.
  • To elucidate the mechanism by which S-PCNA and Srs2 limit the extension of recombination intermediates.
  • To identify novel regulatory pathways controlling genome stability during DNA replication and repair.

Main Methods:

  • Yeast genetics and molecular biology techniques.
  • Analysis of Srs2 activity, including its SUMO interaction motif (SIM).
  • Biochemical assays to study protein interactions and enzyme dissociation from DNA repair complexes.

Main Results:

  • S-PCNA and Srs2 inhibit the synthesis-dependent extension of recombination intermediates, preventing crossover formation.
  • This Srs2 function requires its C-terminal SUMO interaction motif but not its translocase activity or Rad51 interaction.
  • Srs2 binding to S-PCNA displaces DNA polymerases Polδ and Polη from the repair machinery.

Conclusions:

  • A novel mechanism is revealed where S-PCNA and Srs2 limit repair synthesis extension, controlling spontaneous genome rearrangements.
  • Srs2 dissociates polymerases from repair synthesis machinery, highlighting a new regulatory control point.
  • Cellular SUMOylation of PCNA attenuates DNA strand exchanges during template switching or HR, maintaining genome stability.

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