The E3 ligase Topors induces the accumulation of polysumoylated forms of DNA topoisomerase I in vitro and in vivo.
Human Topors has originally been identified as binding partner of p53 and DNA topoisomerase I (TOP1). It can function as both an ubiquitin and SUMO-1 E3 ligase for p53. Here we demonstrate that Topors enhances the formation of high-molecular weight SUMO-1 conjugates of TOP1 in a reconstituted in vitro system and also in human osteosarcoma cells, similar to treatment with CPT. In contrast to the situation observed with p53, overall sumoylation levels were rather unaffected. Experiments with TOP1 point mutants strongly suggest that the high-molecular weight conjugates represent SUMO-1 chains formed on a limited number of SUMO-1 acceptor sites.
Hammer
Eva
E
Institute of Virology, Charité Campus Benjamin Franklin, Free University of Berlin, Hindenburgdamm 27, 12203 Berlin, Germany.
Heilbronn
Regine
R
Weger
Stefan
S
D045744:Cell Line, Tumor; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D025842:SUMO-1 Protein; C120157:TOPORS protein, human; D044767:Ubiquitin-Protein Ligases; D004264:DNA Topoisomerases, Type I