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-Å 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. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.
CITATION STYLE
Li, Z., Cao, R., Wang, M., Myers, M. P., Zhang, Y., & Xu, R. M. (2006). Structure of a Bmi-1-Ring1B polycomb group ubiquitin ligase complex. Journal of Biological Chemistry, 281(29), 20643–20649. https://doi.org/10.1074/jbc.M602461200
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