title: The isolated C-terminal domain of Ring1B is a dimer made of stable, well-structured monomers.
abstract: The Ring1B is a core subunit protein of the PRC1 (polycomb repressive complex 1), which plays key roles in the regulation of the Homeobox gene expression, X-chromosome inactivation, stem cell self-renewal, and tumorigenesis. The C-terminal region of Ring1B interacts with RYBP, a transcriptional repressor in transiently transfected cells, and also with M33, another transcriptional repressor involved in mesoderm patterning. In this work, we show that the C-terminal domain of Ring1B, C-Ring1B, is a dimer in solution, with a dissociation constant of 200 microM, as shown by NMR, ITC, and analytical gel filtration. Each monomer is stable at physiological conditions in a wide pH range ( approximately 5 kcal mol-1 at 298 K), with a well-formed core and a spherical shape. The dimer has a high content of alpha-helix and beta-sheet, as indicated by FTIR spectra, and it is formed by the mutual docking of the preformed folded monomers. Since the C-terminal region is important for interaction with other proteins of the PRC1, the dimerization and the presence of those well-structured monomers might be a form of regulation.
authors.affiliation: Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, 03202 Elche (Alicante), Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Czypionka
authors.forename: Olga Ruiz
authors.initials: OR
authors.lastname: de los Paños
authors.forename: Mauricio G
authors.initials: MG
authors.lastname: Mateu
authors.forename: Francisco N
authors.initials: FN
authors.lastname: Barrera
authors.forename: Estefanía
authors.initials: E
authors.lastname: Hurtado-Gómez
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez
authors.forename: Miguel
authors.initials: M
authors.lastname: Vidal
authors.forename: José L
authors.initials: JL
authors.lastname: Neira
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002850:Chromatography, Gel; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D019281:Dimerization; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008969:Molecular Sequence Data; D063150:Polycomb Repressive Complex 1; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins; D044767:Ubiquitin-Protein Ligases
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1; C489842:Rnf2 protein, mouse; D044767:Ubiquitin-Protein Ligases