Autoubiquitination of the BRCA1*BARD1 RING ubiquitin ligase.
The RING finger of BRCA1 confers ubiquitin ligase activity that is markedly enhanced when complexed with another RING-containing protein, BARD1, and is required for the function of this tumor suppressor protein in protecting genomic integrity. Here, we report that co-expression of BRCA1-(1-639) and BARD1 in bacteria can assemble a potent ... ubiquitin ligase activity. Purified BRCA1-(1-639)*BARD1 stimulated the Ubc5c-mediated monoubiquitination of histone H2A/H2AX in vitro, suggesting a possible role for BRCA1*BARD1 in modifying chromatin structure. Moreover, the truncated BRCA1*BARD1 complex exhibited efficient autoubiquitination activity in vitro capable of assembling non-lysine 48-linked polyubiquitin chains on both BRCA1-(1-639) and BARD1. When co-expressed in cells by transient transfection, the recombinant BRCA1-(1-300).BARD1 complex was found to be associated with polyubiquitin chains, suggesting that BRCA1-(1-300)*BARD1 was ubiquitinated in vivo as well. These results raise the possibility that BRCA1*BARD1 acts to assemble non-lysine 48-linked polyubiquitin chains that may serve as part of a signaling platform required for coordinating DNA repair-related events.
Mesh Terms:
BRCA1 Protein, Carrier Proteins, Cell Line, DNA Repair, Dimerization, Glutathione Transferase, Histones, Humans, Kinetics, Lysine, Protein Binding, Recombinant Proteins, Transfection, Tumor Suppressor Proteins, Ubiquitin, Ubiquitin-Protein Ligases
BRCA1 Protein, Carrier Proteins, Cell Line, DNA Repair, Dimerization, Glutathione Transferase, Histones, Humans, Kinetics, Lysine, Protein Binding, Recombinant Proteins, Transfection, Tumor Suppressor Proteins, Ubiquitin, Ubiquitin-Protein Ligases
J. Biol. Chem.
Date: Jun. 14, 2002
PubMed ID: 11927591
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