Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.25.1 (proteasome)
 28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ubiquitin/proteasome-mediated protein degradation controls various developmental pathways in eukaryotes. Cullin-containing complexes are both versatile and abundant groups of RING family ubiquitin E3 ligases, whose activities are subject to control by RUB/Nedd8 (for related to ubiquitin/neural precursor cell-expressed developmentally downregulated 8) modification of their cullin subunits. Here, we report the identification of an Arabidopsis thaliana counterpart of human CAND1 (cullin-associated and neddylation-dissociated) and demonstrate that it can preferentially interact with unmodified CUL1. The Arabidopsis cand1-1 null mutant displays distinct phenotypes, including late flowering, aerial rosettes, floral organ defects, low fertility, dwarfism, loss of apical dominance, and altered responses to multiple plant hormones. Molecular analyses show that many of these defects are because of compromised activity of CUL1-containing ubiquitin E3 ligases, indicating that CAND1 is required for their optimal activity. Furthermore, the cand1-1 mutant displays a partial constitutive photomorphogenic phenotype and has defects in HY5 degradation in the absence of light, a process mediated by a different RING family E3, COP1. Thus, our data provides genetic support for a critical role of CAND1 in regulating various ubiquitin E3 ligases and their targeted cellular and developmental pathways.
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PMID:Arabidopsis CAND1, an unmodified CUL1-interacting protein, is involved in multiple developmental pathways controlled by ubiquitin/proteasome-mediated protein Degradation. 1520 91

Regulated protein degradation contributes to plant development by mediating signaling events in many hormone, light, and developmental pathways. Ubiquitin ligases recognize and ubiquitinate target proteins for subsequent degradation by the 26S proteasome. The multisubunit SCF is the best-studied class of ubiquitin ligases in Arabidopsis (Arabidopsis thaliana). However, the extent of SCF participation in signaling networks is unclear. SCFs are composed of four subunits: CULLIN 1 (CUL1), ASK, RBX1, and an F-box protein. Null mutations in CUL1 are embryo lethal, limiting insight into the role of CUL1 and SCFs in later stages of development. Here, we describe a viable and fertile weak allele of CUL1, called cul1-6. cul1-6 plants have defects in seedling and adult morphology. In addition to reduced auxin sensitivity, cul1-6 seedlings are hyposensitive to ethylene, red, and blue light conditions. An analysis of protein interactions with the cul1-6 gene product suggests that both RUB (related to ubiquitin) modification and interaction with the SCF regulatory protein CAND1 (cullin associated and neddylation dissociated) are disrupted. These findings suggest that the morphological defects observed in cul1-6 plants are caused by defective SCF complex formation. Characterization of weak cul1 mutants provides insight into the role of SCFs throughout plant growth and development.
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PMID:A new CULLIN 1 mutant has altered responses to hormones and light in Arabidopsis. 1715 85

Nrf2 is a transcription factor that has emerged as the cell's main defense mechanism against many harmful environmental toxicants and carcinogens. Nrf2 is negatively regulated by Keap1, a substrate adaptor protein for the Cullin3 (Cul3)-containing E3-ligase complex, which targets Nrf2 for ubiquitination and degradation by the ubiquitin proteasome system (UPS). Recent evidence suggests that constitutive activation of Nrf2, due to mutations in Keap1 or Nrf2, is prominent in many cancer types and contributes to chemoresistance. Regulation of Nrf2 by the Cul3-Keap1-E3 ligase provides strong evidence that tight regulation of Cullin-ring ligases (CRLs) is imperative to maintain cellular homeostasis. There are seven known Cullin proteins that form various CRL complexes. They are regulated by neddylation/deneddylation, ubiquitination/deubiquitination, CAND1-assisted complex assembly/disassembly, and subunit dimerization. In this review, we will discuss the regulation of each CRL using the Cul3-Keap1-E3 ligase complex as the primary focus. The substrates of CRLs are involved in many signaling pathways. Therefore, deregulation of CRLs affects several cellular processes, including cell cycle arrest, DNA repair, cell proliferation, senescence, and death, which may lead to many human diseases, including cancer. This makes CRLs a promising target for novel cancer drug therapies.
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PMID:Regulation of the Nrf2-Keap1 antioxidant response by the ubiquitin proteasome system: an insight into cullin-ring ubiquitin ligases. 2048 66

The conserved N-terminal domains of the major tegument proteins of herpes viridae encode cysteine proteases with potent ubiquitin and NEDD8-specific deconjugase activity. Here we show that the Epstein-Barr virus-encoded member of this enzyme family, BPLF1, is targeted to cullin-RING ubiquitin ligases (CRLs) via the interaction of the conserved helix-2 with helix-23 of the C-terminal domain (CTD) of cullins, at a site involved in electrostatic interaction with helix-8 of the CRL regulator CAND1. Mutation of the solvent-exposed Asp86 and Asp90 of helix-2 to Arg does not affect the enzymatic activity of BPLF1 but abolishes cullin binding and prevents CRL inactivation. The binding of the catalytically active BPLF1 to cullins inhibits the recruitment of CAND1 to the deneddylated CRLs and promotes the selective degradation of cullins by the proteasome. Cullin proteolysis is rescued by the overexpression of CAND1 or its CTD-binding N-terminal domain. These findings illustrate a new strategy for viral modulation of CRL activity where the combined effects of cullin deneddylation and their targeting for proteasomal degradation drive stable inactivation of the ligases.
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PMID:Herpes virus deneddylases interrupt the cullin-RING ligase neddylation cycle by inhibiting the binding of CAND1. 2247 75

Tumor cells frequently promote the dysregulation of the cell cycle and escape from apoptotic cell death triggered by a number of cellular stresses. Programmed proteolytic degradation of regulatory proteins via the ubiquitin-proteasome pathway is crucial for homeostasis of numerous biological processes. Disruption of this system is one of the factors that promote aberrant cell-proliferation. The small ubiquitin-like protein, NEDD8, has been identified as a fundamental regulator of the activity of the E3 ubiquitin ligases called the SCF complex (consisting of Skp-1, cullin, and F-box protein) or CRL (cullin-RING ubiquitin ligase) which control a final step in ubiquitination of diverse substrates associated with cancer biology. The ubiquitin ligase activity of the SCF complex requires NEDD8 to covalently bind to cullins. To a large extent, exploring the negative regulation system of the NEDD8 pathway is expected to lead to the development of novel anticancer targets. This review focuses on the NEDD8 negative regulation system including chemical compounds such as MLN4924 and protein molecules (e.g. COP9 signalosome, CAND1, inactive mutant of Ubc12 and NUB1/NUB1L) and clarifies possible strategies for targeting the NEDD8 cascade in cancer cells.
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PMID:Negative regulation of NEDD8 conjugation pathway by novel molecules and agents for anticancer therapy. 2318 74