Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Brca1 A complex contains Brca1/Bard1, Abraxas, Rap80, and Brcc36; however, with the exception of the Brca1-Abraxas interaction, how the A complex is assembled is not known. The A complex is localized to sites of DNA damage through the UIM domains of RAP80, which bind K63-linked polyubiquitin chains. In this study, we identified an FHA domain RING finger E3 ubiquitin ligase, RNF8, and an E2-conjugating enzyme known to form K63-polyubiquitin chains, Ubc13, each of which is required to recruit the Brca1 A complex to sites of DNA damage. Rnf8 localizes to sites of DNA damage through an FHA-domain-containing region. We found that Rap80 contains an Abraxas interaction domain [AIR (Abraxas-interacting region)], required for association of Rap80 with Abraxas, Brca1, and Brcc36. Abraxas and Brcc36 associate through coiled-coil domains on each protein. These data suggest a model through which Ubc13 and Rnf8 are recruited to sites of DNA damage through DNA-damage-induced phosphorylation of a chromatin-associated protein and generate polyubiquitin chains that then recruit Rap80 and the entire Brca1 A complex to DNA-damage foci. This sequential E3 ubiquitin ligase recruitment constitutes a ubiquitin ligase cascade required for DNA repair and checkpoint signaling.
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PMID:Ubc13/Rnf8 ubiquitin ligases control foci formation of the Rap80/Abraxas/Brca1/Brcc36 complex in response to DNA damage. 1809 7

Chfr, a checkpoint with FHA and RING finger domains, plays an important role in cell cycle progression and tumor suppression. Chfr possesses the E3 ubiquitin ligase activity and stimulates the formation of polyubiquitin chains by Ub-conjugating enzymes, and induces the proteasome-dependent degradation of a number of cellular proteins, including Plk1 and Aurora A. While Chfr is a nuclear protein that functions within the cell nucleus, how Chfr is localized in the nucleus has not been clearly demonstrated. Here, we show that nuclear localization of Chfr is mediated by nuclear localization signal (NLS) sequences. To reveal the signal sequences responsible for nuclear localization, a short lysine-rich stretch (KKK) at amino acid residues 257-259 was replaced with alanine, which completely abolished nuclear localization. Moreover, we show that nuclear localization of Chfr is essential for its checkpoint function but not for its stability. Thus, our results suggest that NLS-mediated nuclear localization of Chfr leads to its accumulation within the nucleus, which may be important in the regulation of Chfr activation and Chfr-mediated cellular processes, including cell cycle progression and tumor suppression.
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PMID:Nuclear localization of Chfr is crucial for its checkpoint function. 1932 84