title: Modification of the human thymine-DNA glycosylase by ubiquitin-like proteins facilitates enzymatic turnover.
abstract: DNA glycosylases initiate base excision repair (BER) through the generation of potentially harmful abasic sites (AP sites) in DNA. Human thymine-DNA glycosylase (TDG) is a mismatch-specific uracil/thymine-DNA glycosylase with an implicated function in the restoration of G*C base pairs at sites of cytosine or 5-methylcytosine deamination. The rate-limiting step in the action of TDG in vitro is its dissociation from the product AP site, suggesting the existence of a specific enzyme release mechanism in vivo. We show here that TDG interacts with and is covalently modified by the ubiquitin-like proteins SUMO-1 and SUMO-2/3. SUMO conjugation dramatically reduces the DNA substrate and AP site binding affinity of TDG, and this is associated with a significant increase in enzymatic turnover in reactions with a G*U substrate and the loss of G*T processing activity. Sumoylation also potentiates the stimulatory effect of APE1 on TDG. These observations implicate a function of sumoylation in the controlled dissociation of TDG from the AP site and open up novel perspectives for the understanding of the molecular mechanisms coordinating the early steps of BER.
authors.affiliation: Institute of Medical Radiobiology, University of Zürich and the Paul Scherrer Institute, August Forel Strasse 7, CH-8008 Zürich, Switzerland.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hardeland
authors.forename: Roland
authors.initials: R
authors.lastname: Steinacher
authors.forename: Josef
authors.initials: J
authors.lastname: Jiricny
authors.forename: Primo
authors.initials: P
authors.lastname: Schär
mesh_terms: D001665:Binding Sites; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein; C117909:SUMO2 protein, human; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; D014452:Ubiquitins; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D008239:Lysine