Abstract
Mutation of the BRCA1 tumor suppressor gene predisposes women to hereditary breast and ovarian cancers. BRCA1 forms a heterodimer with BARD1. The BRCA1/BARD1 heterodimer has ubiquitin ligase activity, considered to play crucial roles in tumor suppression and DNA damage response. Nevertheless, relevant BRCA1 substrates are poorly defined. We have developed a new approach to systematically identify the substrates of ubiquitin ligases by identifying proteins that display an enhanced incorporation of His-tagged ubiquitin upon ligase coexpression; using this method, we identified several candidate substrates for BRCA1. These include scaffold attachment factor B2 (SAFB2) and Tel2 as well as BARD1. BRCA1 was found to enhance SAFB protein expression and induce Tel2 nuclear translocation. Identification of the ubiquitination substrates has been a major obstacle to understanding the functions of ubiquitin ligases. The quantitative proteomics approach we devised for the identification of BRCA1 substrates will facilitate the identification of ubiquitin ligase-substrate pairs.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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BRCA1 Protein / genetics
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BRCA1 Protein / metabolism*
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Cell Nucleus / metabolism
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Cells, Cultured
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Gene Expression
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Gene Expression Regulation
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Humans
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Matrix Attachment Region Binding Proteins / genetics
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Matrix Attachment Region Binding Proteins / metabolism
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Mice
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Multiprotein Complexes / metabolism
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Nuclear Matrix-Associated Proteins / genetics
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Nuclear Matrix-Associated Proteins / metabolism
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Protein Transport
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Proteomics
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Proto-Oncogene Proteins c-ets / metabolism
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Receptors, Estrogen / genetics
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Receptors, Estrogen / metabolism
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Tumor Suppressor Proteins / genetics
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Tumor Suppressor Proteins / metabolism*
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / metabolism*
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Ubiquitinated Proteins / genetics
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Ubiquitinated Proteins / isolation & purification
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Ubiquitinated Proteins / metabolism
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Ubiquitination*
Substances
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BRCA1 Protein
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BRCA1 protein, human
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ETV7 protein, human
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Matrix Attachment Region Binding Proteins
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Multiprotein Complexes
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Nuclear Matrix-Associated Proteins
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Proto-Oncogene Proteins c-ets
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Receptors, Estrogen
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SAFB protein, human
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Tumor Suppressor Proteins
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Ubiquitinated Proteins
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BARD1 protein, human
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Ubiquitin-Protein Ligases