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.
