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SUMO modification of the neuroprotective protein TDP1 facilitates chromosomal single-strand break repair

Jessica J R Hudson1, Shih-Chieh Chiang, Owen S Wells

  • 1Genome Damage and Stability Centre, University of Sussex, Science Park Road, Falmer, Brighton BN1 9RQ, UK.

Nature Communications
|March 15, 2012
PubMed

Insights

Small ubiquitin-like modifier (SUMO)ylation of tyrosyl DNA phosphodiesterase 1 (TDP1) is crucial for DNA repair. SUMOylation enhances TDP1 accumulation at DNA damage sites, protecting the nervous system from genotoxic stress.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • DNA strand breaks are essential for chromosome metabolism but require resealing to prevent neurodegeneration.
  • Tyrosyl DNA phosphodiesterase 1 (TDP1) is vital for removing stalled topoisomerase 1 peptides, and its defects are linked to human neurodegenerative diseases.
  • The precise regulatory mechanisms governing TDP1 function, particularly in response to DNA damage, remain incompletely understood.

Purpose of the Study:

  • To investigate the role of post-translational modifications in regulating TDP1 function.
  • To determine if TDP1 is modified by small ubiquitin-like modifier (SUMO)ylation.
  • To elucidate the functional consequences of TDP1 SUMOylation on DNA repair and cellular response to genotoxic stress.

Main Methods:

  • Purification of SUMOylated TDP1 from mammalian cells.
  • Identification of the specific SUMOylation site on TDP1 using mass spectrometry.
  • Assessment of TDP1 catalytic activity in vitro.
  • Analysis of TDP1 localization to DNA damage sites using microscopy.
  • Evaluation of DNA repair kinetics in cells expressing wild-type and SUMOylation-deficient TDP1 mutants.

Main Results:

  • TDP1 was identified as a substrate for SUMOylation, with lysine 111 being the primary modification site.
  • SUMOylation did not affect the intrinsic catalytic activity of TDP1.
  • SUMOylation significantly promoted the accumulation of TDP1 at sites of DNA damage.
  • A TDP1 mutant lacking SUMOylation (K111R) exhibited impaired repair of chromosomal single-strand breaks.
  • Impaired repair was observed under conditions of transcription-associated topoisomerase 1 activity and oxidative stress.

Conclusions:

  • SUMOylation is a critical regulatory mechanism for TDP1 function during DNA repair.
  • SUMOylation enhances TDP1 recruitment to DNA damage sites, facilitating efficient repair of single-strand breaks.
  • These findings reveal a novel role for SUMOylation in maintaining genomic stability and protecting the nervous system from genotoxic insults.

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