The Isolated C-Terminal Domain of Ring1B Is a Dimer Made of Stable, Well-Structured Monomers

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• 作者：Anna Czypionka ; Olga Ruiz de los Pa&ntilde ; os ; Mauricio G. Mateu ; Francisco N. Barrera ; Estefaní ; a Hurtado-G&oacute ; mez ; Javier G&oacute ; mez ; Miguel Vidal ; José ; L. Neira
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：November 6, 2007
• 年：2007
• 卷：46
• 期：44
• 页码：12764 - 12776
• 全文大小：184K
• 年卷期：v.46,no.44(November 6, 2007)
• ISSN：1520-4995

文摘

The Ring1B is a core subunit protein of the PRC1 (polycomb repressive complex 1), whichplays key roles in the regulation of the Homeobox gene expression, X-chromosome inactivation, stemcell self-renewal, and tumorigenesis. The C-terminal region of Ring1B interacts with RYBP, a transcriptionalrepressor in transiently transfected cells, and also with M33, another transcriptional repressor involved inmesoderm patterning. In this work, we show that the C-terminal domain of Ring1B, C-Ring1B, is adimer in solution, with a dissociation constant of 200 M, as shown by NMR, ITC, and analytical gelfiltration. Each monomer is stable at physiological conditions in a wide pH range (~5 kcal mol^-1 at 298K), with a well-formed core and a spherical shape. The dimer has a high content of -helix and -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 dimerizationand the presence of those well-structured monomers might be a form of regulation.