Structure of a Bmi-1-Ring1B polycomb group ubiquitin ligase complex.
Polycomb group proteins Bmi-1 and Ring1B are core subunits of the PRC1 complex, which plays important roles in the regulation of Hox gene expression, X-chromosome inactivation, tumorigenesis, and stem cell self-renewal. The RING finger protein Ring1B is an E3 ligase that participates in the ubiquitination of lysine 119 of histone ... H2A, and the binding of Bmi-1 stimulates the E3 ligase activity. We have mapped the regions of Bmi-1 and Ring1B required for efficient ubiquitin transfer and determined a 2.5-A structure of the Bmi-1-Ring1B core domain complex. The structure reveals that Ring1B "hugs" Bmi-1 through extensive RING domain contacts and its N-terminal tail wraps around Bmi-1. The two regions of interaction have a synergistic effect on the E3 ligase activity. Our analyses suggest a model where the Bmi-1-Ring1B complex stabilizes the interaction between the E2 enzyme and the nucleosomal substrate to allow efficient ubiquitin transfer.
Mesh Terms:
Crystallography, X-Ray, DNA-Binding Proteins, Humans, Models, Molecular, Nuclear Proteins, Protein Conformation, Protein Structure, Secondary, Proto-Oncogene Proteins, Recombinant Proteins, Repressor Proteins, Ubiquitin-Protein Ligases
Crystallography, X-Ray, DNA-Binding Proteins, Humans, Models, Molecular, Nuclear Proteins, Protein Conformation, Protein Structure, Secondary, Proto-Oncogene Proteins, Recombinant Proteins, Repressor Proteins, Ubiquitin-Protein Ligases
J. Biol. Chem.
Date: Jul. 21, 2006
PubMed ID: 16714294
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