Ubiquitin binding modulates IAP antagonist-stimulated proteasomal degradation of c-IAP1 and c-IAP21

2008 ◽  
Vol 417 (1) ◽  
pp. 149-165 ◽  
Author(s):  
John W. Blankenship ◽  
Eugene Varfolomeev ◽  
Tatiana Goncharov ◽  
Anna V. Fedorova ◽  
Donald S. Kirkpatrick ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Proteasomal Degradation ◽  
Nuclear Factor Κb ◽  
Titration Calorimetry ◽  
Tumour Necrosis Factor Receptor ◽  
Amino Acid Residues ◽  
Polyubiquitin Chains ◽  
Ubiquitin Ligase Activity ◽  
Ubiquitin Binding ◽  
Uba Domain

A family of anti-apoptotic regulators known as IAP (inhibitor of apoptosis) proteins interact with multiple cellular partners and inhibit apoptosis induced by a variety of stimuli. c-IAP (cellular IAP) 1 and 2 are recruited to TNFR1 (tumour necrosis factor receptor 1)-associated signalling complexes, where they mediate receptor-induced NF-κB (nuclear factor κB) activation. Additionally, through their E3 ubiquitin ligase activities, c-IAP1 and c-IAP2 promote proteasomal degradation of NIK (NF-κB-inducing kinase) and regulate the non-canonical NF-κB pathway. In the present paper, we describe a novel ubiquitin-binding domain of IAPs. The UBA (ubiquitin-associated) domain of IAPs is located between the BIR (baculovirus IAP repeat) domains and the CARD (caspase activation and recruitment domain) or the RING (really interesting new gene) domain of c-IAP1 and c-IAP2 or XIAP (X-linked IAP) respectively. The c-IAP1 UBA domain binds mono-ubiquitin and Lys48- and Lys63-linked polyubiquitin chains with low-micromolar affinities as determined by surface plasmon resonance or isothermal titration calorimetry. NMR analysis of the c-IAP1 UBA domain–ubiquitin interaction reveals that this UBA domain binds the classical hydrophobic patch surrounding Ile44 of ubiquitin. Mutations of critical amino acid residues in the highly conserved MGF (Met-Gly-Phe) binding loop of the UBA domain completely abrogate ubiquitin binding. These mutations in the UBA domain do not overtly affect the ubiquitin ligase activity of c-IAP1 or the participation of c-IAP1 and c-IAP2 in the TNFR1 signalling complex. Treatment of cells with IAP antagonists leads to proteasomal degradation of c-IAP1 and c-IAP2. Deletion or mutation of the UBA domain decreases this degradation, probably by diminishing the interaction of the c-IAPs with the proteasome. These results suggest that ubiquitin binding may be an important mechanism for rapid turnover of auto-ubiquitinated c-IAP1 and c-IAP2.

scholarly journals Structural Basis of Ubiquitin Recognition by the Ubiquitin-associated (UBA) Domain of the Ubiquitin Ligase EDD

2007 ◽  
Vol 282 (49) ◽  
pp. 35787-35795 ◽  
Author(s):  
Guennadi Kozlov ◽  
Long Nguyen ◽  
Tong Lin ◽  
Gregory De Crescenzo ◽  
Morag Park ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Site Directed Mutagenesis ◽  
Structural Basis ◽  
Titration Calorimetry ◽  
Polyubiquitin Chains ◽  
C Terminus ◽  
Damage Repair ◽  
The Family ◽  
Uba Domain ◽  
Ordered Water

EDD (or HYD) is an E3 ubiquitin ligase in the family of HECT (homologous to E6-AP C terminus) ligases. EDD contains an N-terminal ubiquitin-associated (UBA) domain, which is present in a variety of proteins involved in ubiquitin-mediated processes. Here, we use isothermal titration calorimetry (ITC), NMR titrations, and pull-down assays to show that the EDD UBA domain binds ubiquitin. The 1.85Å crystal structure of the complex with ubiquitin reveals the structural basis of ubiquitin recognition by UBA helices α1 and α3. The structure shows a larger number of intermolecular hydrogen bonds than observed in previous UBA/ubiquitin complexes. Two of these involve ordered water molecules. The functional importance of residues at the UBA/ubiquitin interface was confirmed using site-directed mutagenesis. Surface plasmon resonance (SPR) measurements show that the EDD UBA domain does not have a strong preference for polyubiquitin chains over monoubiquitin. This suggests that EDD binds to monoubiquitinated proteins, which is consistent with its involvement in DNA damage repair pathways.

Structural insights into specificity and diversity in mechanisms of ubiquitin recognition by ubiquitin-binding domains

2012 ◽  
Vol 40 (2) ◽  
pp. 404-408 ◽  
Author(s):  
Mark S. Searle ◽  
Thomas P. Garner ◽  
Joanna Strachan ◽  
Jed Long ◽  
Jennifer Adlington ◽  
...  
Keyword(s):  
Proteasomal Degradation ◽  
Nuclear Factor Κb ◽  
Degradation Pathways ◽  
Protein Motifs ◽  
Binding Domains ◽  
Functional Models ◽  
Wide Range ◽  
Ubiquitin Binding ◽  
Uba Domain ◽  
Supporting Functional

UBDs [Ub (ubiquitin)-binding domains], which are typically small protein motifs of <50 residues, are used by receptor proteins to transduce post-translational Ub modifications in a wide range of biological processes, including NF-κB (nuclear factor κB) signalling and proteasomal degradation pathways. More than 20 families of UBDs have now been characterized in structural detail and, although many recognize the canonical Ile44/Val70-binding patch on Ub, a smaller number have alternative Ub-recognition sites. The A20 Znf (A20-like zinc finger) of the ZNF216 protein is one of the latter and binds with high affinity to a polar site on Ub centred around Asp58/Gln62. ZNF216 shares some biological function with p62, with both linked to NF-κB signal activation and as shuttle proteins in proteasomal degradation pathways. The UBA domain (Ub-associated domain) of p62, although binding to Ub through the Ile44/Val70 patch, is unique in forming a stable dimer that negatively regulates Ub recognition. We show that the A20 Znf and UBA domain are able to form a ternary complex through independent interactions with a single Ub molecule, supporting functional models for Ub as a ‘hub’ for mediating multi-protein complex assembly and for enhancing signalling specificity.

Gfi1 ubiquitination and proteasomal degradation is inhibited by the ubiquitin ligase Triad1

Blood ◽  
2007 ◽  
Vol 110 (9) ◽  
pp. 3128-3135 ◽  
Author(s):  
Jurgen A. F. Marteijn ◽  
Laurens T. van der Meer ◽  
Liesbeth van Emst ◽  
Simon van Reijmersdal ◽  
Willemijn Wissink ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Ubiquitin Ligase ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
Binding Domain ◽  
U937 Cells ◽  
Dna Binding Domain ◽  
Protein Levels ◽  
Ubiquitin Ligase Activity ◽  
Ubiquitin Proteasome

Abstract Growth factor independence 1 (Gfi1) is a transcriptional repressor essential for the function and development of many different hematopoietic lineages. The Gfi1 protein expression is regulated by the ubiquitin-proteasome system. In granulocytes, Gfi1 is rapidly degraded by the proteasome, while it is more stable in monocytes. How the ubiquitination and degradation of Gfi1 is regulated is unclear. Here, we show that the ubiquitin ligase Triad1 interacts with the DNA-binding domain of Gfi1. Unexpectedly, we found that Triad1 inhibited Gfi1 ubiquitination, resulting in a prolonged half-life. Down-regulation of endogenous Triad1 by siRNAs resulted in increased Gfi1 ubiquitination. In U937 cells, Triad1 caused an increase in endogenous Gfi1 protein levels and slowed cell proliferation in a similar manner when Gfi1 itself was expressed. A Triad1 mutant that lacks the Gfi1-binding domain did not affect Gfi1 levels and proliferation. Because neither proteasome-ubiquitin nor Triad1 ubiquitin ligase activity was required for the inhibition of Gfi1 ubiquitination, these data suggest that Triad1 competes for Gfi1 binding with as yet to be identified E3 ubiquitin ligases that do mark Gfi1 for proteasomal degradation. The finetuning of Gfi1 protein levels regulated by Triad1 defines an unexpected role for this protein in hematopoiesis.

scholarly journals The UBXN1 Protein Associates with Autoubiquitinated Forms of the BRCA1 Tumor Suppressor and Inhibits Its Enzymatic Function

2010 ◽  
Vol 30 (11) ◽  
pp. 2787-2798 ◽  
Author(s):  
Foon Wu-Baer ◽  
Thomas Ludwig ◽  
Richard Baer
Keyword(s):  
Tumor Suppressor ◽  
Polyubiquitin Chains ◽  
Binding Motifs ◽  
Protein Substrates ◽  
Cellular Processes ◽  
Enzymatic Function ◽  
Ubiquitin Ligase Activity ◽  
Uba Domain ◽  
Biochemical Mechanisms

ABSTRACT Although the BRCA1 tumor suppressor has been implicated in many cellular processes, the biochemical mechanisms by which it influences these diverse pathways are poorly understood. The only known enzymatic function of BRCA1 is the E3 ubiquitin ligase activity mediated by its highly conserved RING domain. In vivo, BRCA1 associates with the BARD1 polypeptide to form a heterodimeric BRCA1/BARD1 complex that catalyzes autoubiquitination of BRCA1 and trans ubiquitination of other protein substrates. In most cases, BRCA1-dependent ubiquitination generates polyubiquitin chains bearing an unconventional K6 linkage that does not appear to target proteins for proteasomal degradation. Since ubiquitin-dependent processes are usually mediated by cellular receptors with ubiquitin-binding motifs, we screened for proteins that specifically bind autoubiquitinated BRCA1. Here we report that the UBXN1 polypeptide, which contains a ubiquitin-associated (UBA) motif, recognizes autoubiquitinated BRCA1. This occurs through a bipartite interaction in which the UBA domain of UBXN1 binds K6-linked polyubiquitin chains conjugated to BRCA1 while the C-terminal sequences of UBXN1 bind the BRCA1/BARD1 heterodimer in a ubiquitin-independent fashion. Significantly, the E3 ligase activity of BRCA1/BARD1 is dramatically reduced in the presence of UBXN1, suggesting that UBXN1 regulates the enzymatic function of BRCA1 in a manner that is dependent on its ubiquitination status.

Orchestra for assembly and fate of polyubiquitin chains

2005 ◽  
Vol 41 ◽  
pp. 1-14 ◽  
Author(s):  
Kuhlbrodt Kirsten ◽  
Mouysset Julien ◽  
Hoppe Thorsten
Keyword(s):  
Protein Degradation ◽  
Ubiquitin Ligase ◽  
Chain Elongation ◽  
Polyubiquitin Chain ◽  
Ubiquitin Chain ◽  
Polyubiquitin Chains ◽  
Intracellular Signals ◽  
Ubiquitin Binding ◽  
Ubiquitin Ligase E3 ◽  
Ubiquitin Conjugating Enzyme

Selective protein degradation by the 26 S proteasome usually requires a polyubiquitin chain attached to the protein substrate by three classes of enzymes: a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin ligase (E3). This reaction can produce different polyubiquitin chains that, depending on size and linkage type, can provide distinct intracellular signals. Interestingly, polyubiquitination is sometimes regulated by additional conjugation factors, called E4s (polyubiquitin chain conjugation factors). Yeast UFD2 (ubiquitin fusion degradation protein-2), the first E4 to be described, binds to the ubiquitin moieties of preformed conjugates and catalyses ubiquitin-chain elongation together with E1, E2, and E3. Recent studies have illustrated that the E4 enzyme UFD2 co-operates with an orchestra of ubiquitin-binding factors in an escort pathway to transfer and deliver polyubiquitinated substrates to the 26 S proteasome. Here we propose a model in which E4-dependent polyubiquitination pathways are modulated by different ubiquitin-binding proteins, using ataxin-3 as an example.

scholarly journals The IRAK-catalysed activation of the E3 ligase function of Pellino isoforms induces the Lys63-linked polyubiquitination of IRAK1

2007 ◽  
Vol 409 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Alban Ordureau ◽  
Hilary Smith ◽  
Mark Windheim ◽  
Mark Peggie ◽  
Emma Carrick ◽  
...  
Keyword(s):  
Interleukin 1 ◽  
Nuclear Factor Κb ◽  
Regulatory Subunit ◽  
Wild Type ◽  
Dna Encoding ◽  
Polyubiquitin Chains ◽  
Ubiquitin Ligase Activity ◽  
Ubiquitin Conjugating Enzyme ◽  
Ligase Function

The protein kinases IRAK [IL-1 (interleukin 1) receptor-associated kinase] 1 and 4 play key roles in a signalling pathway by which bacterial infection or IL-1 trigger the production of inflammatory mediators. In the present study, we demonstrate that IRAK1 and IRAK4 phosphorylate Pellino isoforms in vitro and that phosphorylation greatly enhances Pellino's E3 ubiquitin ligase activity. We show that, in vitro, Pellino 1 can combine with the E2 conjugating complex Ubc13 (ubiquitin-conjugating enzyme 13)–Uev1a (ubiquitin E2 variant 1a) to catalyse the formation of K63-pUb (Lys63-linked polyubiquitin) chains, with UbcH3 to catalyse the formation of K48-pUb chains and with UbcH4, UbcH5a or UbcH5b to catalyse the formation of pUb-chains linked mainly via Lys11 and Lys48 of ubiquitin. In IRAK1−/− cells, the co-transfection of DNA encoding wild-type IRAK1 and Pellino 2, but not inactive mutants of these proteins, induces the formation of K63-pUb–IRAK1 and its interaction with the NEMO [NF-κB (nuclear factor κB) essential modifier] regulatory subunit of the IKK (inhibitor of NF-κB kinase) complex, a K63-pUb-binding protein. These studies suggest that Pellino isoforms may be the E3 ubiquitin ligases that mediate the IL-1-stimulated formation of K63-pUb–IRAK1 in cells, which may contribute to the activation of IKKβ and the transcription factor NF-κB, as well as other signalling pathways dependent on IRAK1/4.

Disruption of ubiquitin-mediated processes in diseases of the brain and bone

2008 ◽  
Vol 36 (3) ◽  
pp. 469-471 ◽  
Author(s):  
Robert Layfield ◽  
Mark S. Searle
Keyword(s):  
Disease Process ◽  
Protein Aggregates ◽  
Ubiquitin Proteasome System ◽  
Nuclear Factor Κb ◽  
Negative Effects ◽  
Multifunctional Protein ◽  
Sequestosome 1 ◽  
Ubiquitin Binding ◽  
Uba Domain ◽  
Ubiquitin Proteasome

A role for ubiquitin in the pathogenesis of human diseases was first suggested some two decades ago, from studies that localized the protein to intracellular protein aggregates, which are a feature of the major human neurodegenerative disorders. Although several different mechanisms have been proposed to connect impairment of the UPS (ubiquitin–proteasome system) to the presence of these ‘ubiquitin inclusions’ within diseased neurones, their significance in the disease process remains to be fully clarified. Ubiquitin inclusions also contain ubiquitin-binding proteins, such as the p62 protein [also known as SQSTM1 (sequestosome 1)], which non-covalently interacts with the ubiquitinated protein aggregates and may serve to mediate their autophagic clearance. p62 is a multifunctional protein and, in the context of bone-resorbing osteoclasts, is an important scaffold in the RANK [receptor activator of NF-κB (nuclear factor κB)]–NF-κB signalling pathway. Further, mutations affecting the UBA domain (ubiquitin-associated domain) of p62 are commonly found in patients with the skeletal disorder PDB (Paget's disease of bone). These mutations impair the ability of p62 to bind to ubiquitin and result in disordered osteoclast NF-κB signalling that may underlie the disease aetiology. Recent structural insights into the unusual mechanism of ubiquitin recognition by the p62 UBA domain have helped rationalize the mechanisms by which different PDB mutations exert their negative effects on ubiquitin binding by p62, as well as providing an indication of the ubiquitin-binding selectivity of p62 and, by extension, its normal biological functions.

scholarly journals Structure of phosphorylated UBL domain and insights into PINK1-orchestrated parkin activation

2016 ◽  
Vol 114 (2) ◽  
pp. 298-303 ◽  
Author(s):  
Jacob D. Aguirre ◽  
Karen M. Dunkerley ◽  
Pascal Mercier ◽  
Gary S. Shaw
Keyword(s):  
Oxidative Stress ◽  
Protein Kinase ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Hydrophobic Core ◽  
Ubiquitin Ligase Activity ◽  
Ubiquitin Binding ◽  
Altered Surface ◽  
Intramolecular Association ◽  
Core Packing

Mutations in PARK2 and PARK6 genes are responsible for the majority of hereditary Parkinson’s disease cases. These genes encode the E3 ubiquitin ligase parkin and the protein kinase PTEN-induced kinase 1 (PINK1), respectively. Together, parkin and PINK1 regulate the mitophagy pathway, which recycles damaged mitochondria following oxidative stress. Native parkin is inactive and exists in an autoinhibited state mediated by its ubiquitin-like (UBL) domain. PINK1 phosphorylation of serine 65 in parkin’s UBL and serine 65 of ubiquitin fully activate ubiquitin ligase activity; however, a structural rationale for these observations is not clear. Here, we report the structure of the phosphorylated UBL domain from parkin. We find that destabilization of the UBL results from rearrangements to hydrophobic core packing that modify its structure. Altered surface electrostatics from the phosphoserine group disrupt its intramolecular association, resulting in poorer autoinhibition in phosphorylated parkin. Further, we show that phosphorylation of both the UBL domain and ubiquitin are required to activate parkin by releasing the UBL domain, forming an extended structure needed to facilitate E2–ubiquitin binding. Together, the results underscore the importance of parkin activation by the PINK1 phosphorylation signal and provide a structural picture of the unraveling of parkin’s ubiquitin ligase potential.

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