title: SUMO-1 regulates the conformational dynamics of thymine-DNA Glycosylase regulatory domain and competes with its DNA binding activity.
abstract: BACKGROUND
  The human thymine-DNA glycosylase (TDG) plays a dual role in base excision repair of G:U/T mismatches and in transcription. Regulation of TDG activity by SUMO-1 conjugation was shown to act on both functions. Furthermore, TDG can interact with SUMO-1 in a non-covalent manner.
  
  
  RESULTS
  Using NMR spectroscopy we have determined distinct conformational changes in TDG upon either covalent sumoylation on lysine 330 or intermolecular SUMO-1 binding through a unique SUMO-binding motif (SBM) localized in the C-terminal region of TDG. The non-covalent SUMO-1 binding induces a conformational change of the TDG amino-terminal regulatory domain (RD). Such conformational dynamics do not exist with covalent SUMO-1 attachment and could potentially play a broader role in the regulation of TDG functions for instance during transcription. Both covalent and non-covalent processes activate TDG G:U repair similarly. Surprisingly, despite a dissociation of the SBM/SUMO-1 complex in presence of a DNA substrate, SUMO-1 preserves its ability to stimulate TDG activity indicating that the non-covalent interactions are not directly involved in the regulation of TDG activity. SUMO-1 instead acts, as demonstrated here, indirectly by competing with the regulatory domain of TDG for DNA binding.
  
  
  CONCLUSIONS
  SUMO-1 increases the enzymatic turnover of TDG by overcoming the product-inhibition of TDG on apurinic sites. The mechanism involves a competitive DNA binding activity of SUMO-1 towards the regulatory domain of TDG. This mechanism might be a general feature of SUMO-1 regulation of other DNA-bound factors such as transcription regulatory proteins.
authors.affiliation: Institut de Recherche Interdisciplinaire, Université de Lille1 - Université de Lille2 - CNRS USR3078, Parc de la Haute Borne, 50 avenue de Halley, 59658 Villeneuve d'Ascq, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Smet-Nocca
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Wieruszeski
authors.forename: Hélène
authors.initials: H
authors.lastname: Léger
authors.forename: Sebastian
authors.initials: S
authors.lastname: Eilebrecht
authors.forename: Arndt
authors.initials: A
authors.lastname: Benecke
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D025842:SUMO-1 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D058207:Sumoylation; D044502:Thymine DNA Glycosylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D025842:SUMO-1 Protein; D004247:DNA; D044502:Thymine DNA Glycosylase