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The DNA topoisomerase I binding protein topors as a novel cellular target for SUMO-1 modification: characterization of domains necessary for subcellular localization and sumolation.

Over the past years, modification by covalent attachment of SUMO (small ubiquitin-like modifier) has been demonstrated for of a number of cellular and viral proteins. While increasing evidence suggests a role for SUMO modification in the regulation of protein-protein interactions and/or subcellular localization, most SUMO targets are still at large. In this report we show that Topors, a Topoisomerase I and p53 interacting protein of hitherto unknown function, presents a novel cellular target for SUMO-1 modification. In a yeast two-hybrid system, Topors interacted with both SUMO-1 and the SUMO-1 conjugating enzyme UBC9. Multiple SUMO-1 modified forms of Topors could be detected after cotransfection of exogenous SUMO-1 and Topors induced the colocalization of a YFP tagged SUMO-1 protein in a speckled pattern in the nucleus. A subset of these Topors' nuclear speckles were closely associated with the PML nuclear bodies (POD, ND10). A central domain comprising Topors residues 437 to 574 was sufficient for both sumolation and localization to nuclear speckles. One SUMO-1 acceptor site at lysine residue 560 could be identified within this region. However, sumolation-deficient Topors mutants showed that sumolation obviously is not required for localization to nuclear speckles.

Pubmed ID: 14516784


  • Weger S
  • Hammer E
  • Engstler M


Experimental cell research

Publication Data

October 15, 2003

Associated Grants


Mesh Terms

  • Active Transport, Cell Nucleus
  • Bacterial Proteins
  • Binding Sites
  • Carrier Proteins
  • Cell Compartmentation
  • Cell Nucleus
  • Cell Nucleus Structures
  • DNA-Binding Proteins
  • Eukaryotic Cells
  • HeLa Cells
  • Humans
  • Ligases
  • Luminescent Proteins
  • Mutation
  • Neoplasm Proteins
  • Nuclear Proteins
  • Protein Structure, Tertiary
  • SUMO-1 Protein
  • Transcription Factors
  • Ubiquitin-Conjugating Enzymes
  • Ubiquitin-Protein Ligases