E3 ubiquitin ligases

Ardley, Helen C.; Robinson, Philip A.

doi:10.1042/bse0410015

Cited by 223 publications

(147 citation statements)

References 36 publications

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“…5,[8][9][10] Substrate recruitment in part occurs through ER-associated degradation, where misfolded protein is retro-translocated to the cytosol for proteasomal degradation. 11 Accumulation of misfolded proteins in the ER induces the UPR, resulting in a decreased rate of general transcription, whereas protein expression of selected chaperones (for example, GRP78/BiP, heat-shock proteins) is increased.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the ubiquitin–proteasome system in bortezomib-adapted cells

et al. 2009

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Resistance towards the proteasome inhibitor bortezomib is poorly understood. We adapted the HL-60, ARH-77 and AMO-1 cell lines (myeloid leukemia, plasmocytoid lymphoma, myeloma) to bortezomib exceeding therapeutic plasma levels, and compared characteristics of the ubiquitin-proteasome system, alternative proteases and the unfolded protein response (UPR) between adapted cells and parental lines. Adapted cells showed increased transcription rates, activities and polypeptide levels of the bortezomib-sensitive b5, but also of the b2 proteasome subunit and consistently retained elevated levels of active b1/b5-type proteasome subunits in the presence of therapeutic levels of bortezomib. Bortezomib-adapted HL-60 cells showed increased expression and proteasome association of the 11S proteasome activator, and did not accumulate poly-ubiquitinated protein, activate the UPR or UPR-mediated apoptosis in response to bortezomib. The rate of protein biosynthesis was reduced, and the transcription of chaperone genes downmodulated. We did not observe major changes in the activities of TPPII, cathepsins or deubiquitinating proteases. We conclude that different types of bortezomib-adapted cell lines, including myeloma, show similar patterns of changes in the proteasomal machinery which result in residual proteasome activity in the presence of bortezomib and a quantitative balance between protein biosynthesis and destruction.

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Section: Introductionmentioning

confidence: 99%

Characterization of the ubiquitin–proteasome system in bortezomib-adapted cells

et al. 2009

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“…It is conjugated to more than 100 cellular proteins through the sequential action of three conjugation enzymes that are also induced by IFN-α/β: E1 (Ube1L) (2), E2 (UbcH8) (3,4), and E3 (Herc5) (5,6). The vast majority of IFN-induced ISG15 conjugation is mediated by a single E3 enzyme, Herc5, in contrast to the ubiquitin system that uses a large number of E3 enzymes to accomplish target selectivity (7).…”

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confidence: 99%

ISG15 conjugation system targets the viral NS1 protein in influenza A virus–infected cells

Zhao

Hsiang

Kuo

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

196

203

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ISG15 is an IFN-α/β-induced, ubiquitin-like protein that is conjugated to a wide array of cellular proteins through the sequential action of three conjugation enzymes that are also induced by IFN-α/β. Recent studies showed that ISG15 and/or its conjugates play an important role in protecting cells from infection by several viruses, including influenza A virus. However, the mechanism by which ISG15 modification exerts antiviral activity has not been established. Here we extend the repertoire of ISG15 targets to a viral protein by demonstrating that the NS1 protein of influenza A virus (NS1A protein), an essential, multifunctional protein, is ISG15 modified in virus-infected cells. We demonstrate that the major ISG15 acceptor site in the NS1A protein in infected cells is a critical lysine residue (K41) in the N-terminal RNA-binding domain (RBD). ISG15 modification of K41 disrupts the association of the NS1A RBD domain with importin-α, the protein that mediates nuclear import of the NS1A protein, whereas the RBD retains its double-stranded RNA-binding activity. Most significantly, we show that ISG15 modification of K41 inhibits influenza A virus replication and thus contributes to the antiviral action of IFN-β. We also show that the NS1A protein directly and specifically binds to Herc5, the major E3 ligase for ISG15 conjugation in human cells. These results establish a "loss of function" mechanism for the antiviral activity of the IFN-induced ISG15 conjugation system, namely, that it inhibits viral replication by conjugating ISG15 to a specific viral protein, thereby inhibiting its function.SG15 is a ubiquitin-like molecule that is highly induced by IFN α/β (1). It is conjugated to more than 100 cellular proteins through the sequential action of three conjugation enzymes that are also induced by IFN-α/β: E1 (Ube1L) (2), E2 (UbcH8) (3, 4), and E3 (Herc5) (5, 6). The vast majority of IFN-induced ISG15 conjugation is mediated by a single E3 enzyme, Herc5, in contrast to the ubiquitin system that uses a large number of E3 enzymes to accomplish target selectivity (7).ISG15 and/or its conjugation play important roles in innate immunity against several viruses. The first clue to the antiviral property of ISG15 conjugation was the finding that the NS1 protein of influenza B virus binds ISG15 and blocks its conjugation, suggesting that ISG15 and/or its conjugation is inhibitory to the replication of influenza B virus (2). Subsequently, the antiinfluenza activity of ISG15 and/or its conjugation was established by the demonstration that ISG15 knockout (ISG15 −/− ) mice are more susceptible to both influenza A and B virus infection (8). Experiments with Ube1L −/− mice established that ISG15 conjugation rather than free ISG15 inhibits influenza B virus replication (9). Further, we established that ISG15 conjugation plays a large role in the IFN-induced antiviral state against influenza A virus in human tissue culture cells (10). Thus, siRNA-silencing of ISG15 conjugation enzymes inhibited IFN-induced ISG15 conjugation and parti...

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“…Recent studies have revealed that IKK activation by cytokines such as TNF and IL-1 and by Tolllike receptors is dependent on Lys63-linked nondegradative polyubiquitination (5). Using biochemical purification and in vitro reconstitution, it was shown that together with a ubiquitin activating enzyme (E1) and a specific dimeric ubiquitin conjugating enzyme Ubc13-Uev1A complex (E2), the RING domain containing protein TRAF6 acts as a specific ubiquitin ligase (E3) in this Lys63-linked polyubiquitination (6)(7)(8). A MAP kinase kinase kinase complex (MAP3K) known as the TAK1 complex containing the kinase TAK1 and two adapter proteins TAB1 and TAB2 is the intermediary in IKK activation.…”

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High-Affinity Interaction between IKKβ and NEMO

Maddineni

Chung

et al. 2008

Biochemistry

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The Ser/Thr-specific IκB kinase (IKK), which comprises IKKα or IKKβ and the regulatory protein NEMO, is at the bottleneck for NF-κB activation. IKK activity relies on interaction between NEMO and IKKα or IKKβ. A conserved region in the C-terminal tail of IKKβ or IKKα (NEMO-binding domain, NBD, residues 734-745 of IKKβ) is important for interaction with NEMO. Here we show that the NBD peptide of IKKβ is not sufficient for interaction with NEMO. Instead, a longer region of the IKKβ C-terminal region provides high affinity for NEMO. Quantitative measurements using surface plasmon resonance and isothermal titration calorimetry confirm the differential affinities of these interactions and provide insight into the kinetic and thermodynamic behaviors of the interactions. Biochemical characterization using multiangle light scattering (MALS) coupled with refractive index shows that the longer IKKβ C-terminal region forms a 2:2 stoichiometirc complex with NEMO.NF-κB proteins (NF-κBs) are evolutionarily conserved master regulators of immune and inflammatory responses (1, 2). They play critical roles in a wide array of biological processes, including innate and adaptive immunity, oncogenesis, and development. They are activated in response to ligation of many receptors, including T-cell receptors, B-cell receptors, members of the tumor necrosis factor (TNF) receptor superfamily, and the Tolllike receptor/interleukin-1 receptor (TLR/IL-1R) superfamily.NF-κBs share a highly conserved DNA-binding/dimerization domain called the Rel homology domain (RHD) (2, 3). The mammalian NF-κB family consists of p65 (RelA), RelB, c-Rel, p50/p105 (NF-κB1), and p52/p100 (NF-κB2). While p65, RelB, and c-Rel contain C-terminal transactivation domains, p105 and p100 contain long C-terminal domains that contain multiple ankyrin repeats and act to inhibit these proteins. The activity of NF-κB family members p65, RelB, and c-Rel is tightly regulated by interaction with the inhibitor of κB (IκB) proteins, which also contain ankyrin repeats, like the C-terminal domain of p105 and p100. Thus, in most cells, NF-κBs are held captive in the cytoplasm from translocating to the nucleus by the IκB proteins or IκB-like domains. The Ser/Thr-specific IκB kinase (IKK) is at the bottleneck for NF-κB activation (4). Activated IKK phosphorylates NF-κB-bound IκBs and the IκB-like domains of p100 and p105. This leads to Lys48-linked polyubiquitination and subsequent degradation of IκBs and processing of p100 and p105, respectively, by the proteasome. The freed or processed NF-κB dimers translocate to the nucleus to mediate specific target gene transcription. Recent studies have revealed that IKK activation by cytokines such as TNF and IL-1 and by Tolllike receptors is dependent on Lys63-linked nondegradative polyubiquitination (5). Using biochemical purification and in vitro reconstitution, it was shown that together with a ubiquitin activating enzyme (E1) and a specific dimeric ubiquitin conjugating enzyme Ubc13-Uev1A complex (E2), the RING domain containin...

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E3 ubiquitin ligases

Cited by 223 publications

References 36 publications

Characterization of the ubiquitin–proteasome system in bortezomib-adapted cells

Characterization of the ubiquitin–proteasome system in bortezomib-adapted cells

ISG15 conjugation system targets the viral NS1 protein in influenza A virus–infected cells

High-Affinity Interaction between IKKβ and NEMO

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