BRCA1-independent ubiquitination of FANCD2.
Monoubiquitination of the FANCD2 protein is a key step in the Fanconi anemia (FA) tumor suppressor pathway, coinciding with this molecule's accumulation at sites of genome damage. Strong circumstantial evidence points to a requirement for the BRCA1 gene product in this step. Here, we show that the purified BRCA1/BARD1 complex, together with E1 and UbcH5a, is sufficient to reconstitute the monoubiquitination of FANCD2 in vitro. Although siRNA-mediated knockdown of BRCA1 in human cells results in defective targeting of FANCD2 to sites of DNA damage, it does not lead to a defect in FANCD2 ubiquitination. Furthermore, ablation of the RING finger domains of either BRCA1 or BARD1 in the chicken B cell line DT40 also leaves FANCD2 modification intact. Consequently, while BRCA1 affects the accumulation of FANCD2 at sites of DNA damage, BRCA1/BARD1 E3 ligase activity is not essential for the monoubiquitination of FANCD2.
Pubmed ID: 12887909 RIS Download
Animals | BRCA1 Protein | Carrier Proteins | Cell-Free System | DNA Damage | Fanconi Anemia | Fanconi Anemia Complementation Group D2 Protein | Gene Expression Regulation, Neoplastic | HeLa Cells | Humans | Iron-Binding Proteins | Ligases | Mutation | Nuclear Proteins | Protein Structure, Tertiary | RNA, Small Interfering | Tumor Suppressor Proteins | Ubiquitin | Ubiquitin-Conjugating Enzymes | Ubiquitin-Protein Ligases