title: The Cockayne syndrome group B protein is a functional dimer.
abstract: Cockayne syndrome (CS) is a rare inherited human genetic disorder characterized by developmental abnormalities, UV sensitivity, and premature aging. The CS group B (CSB) protein belongs to the SNF2-family of DNA-dependent ATPases and is implicated in transcription elongation, transcription coupled repair, and base excision repair. It is a DNA stimulated ATPase and remodels chromatin in vitro. We demonstrate for the first time that full-length CSB positively cooperates in ATP hydrolysis as a function of protein concentration. We have investigated the quaternary structure of CSB using a combination of protein-protein complex trapping experiments and gel filtration, and found that CSB forms a dimer in solution. Chromatography studies revealed that enzymatically active CSB has an apparent molecular mass of approximately 360 kDa, consistent with dimerization of CSB. Importantly, in vivo protein cross-linking showed the presence of the CSB dimer in the nucleus of HeLa cells. We further show that dimerization occurs through the central ATPase domain of the protein. These results have implications for the mechanism of action of CSB, and suggest that other SNF2-family members might also function as dimers.
authors.affiliation: Danish Centre for Molecular Gerontology, Department of Molecular Biology, University of Aarhus, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Christiansen
authors.forename: Tina
authors.initials: T
authors.lastname: Thorslund
authors.forename: Bjarne
authors.initials: B
authors.lastname: Jochimsen
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: Tinna
authors.initials: T
authors.lastname: Stevnsner
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003057:Cockayne Syndrome / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D000075223:Poly-ADP-Ribose Binding Proteins; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D000075223:Poly-ADP-Ribose Binding Proteins; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes