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Structural basis for ligase-specific conjugation of linear ubiquitin chains by HOIP.

ABSTRACT: Linear ubiquitin chains are important regulators of cellular signalling pathways that control innate immunity and inflammation through nuclear factor (NF)-?B activation and protection against tumour necrosis factor-?-induced apoptosis. They are synthesized by HOIP, which belongs to the RBR (RING-between-RING) family of E3 ligases and is the catalytic component of LUBAC (linear ubiquitin chain assembly complex), a multisubunit E3 ligase. RBR family members act as RING/HECT hybrids, employing RING1 to recognize ubiquitin-loaded E2 while a conserved cysteine in RING2 subsequently forms a thioester intermediate with the transferred or 'donor' ubiquitin. Here we report the crystal structure of the catalytic core of HOIP in its apo form and in complex with ubiquitin. The carboxy-terminal portion of HOIP adopts a novel fold that, together with a zinc-finger, forms a ubiquitin-binding platform that orients the acceptor ubiquitin and positions its ?-amino group for nucleophilic attack on the E3?ubiquitin thioester. The C-terminal tail of a second ubiquitin molecule is located in close proximity to the catalytic cysteine, providing a unique snapshot of the ubiquitin transfer complex containing both donor and acceptor ubiquitin. These interactions are required for activation of the NF-?B pathway in vivo, and they explain the determinants of linear ubiquitin chain specificity by LUBAC.

SUBMITTER: Stieglitz B

PROVIDER: S-EPMC3838313 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Structural basis for ligase-specific conjugation of linear ubiquitin chains by HOIP.

Stieglitz Benjamin B Rana Rohini R RR Koliopoulos Marios G MG Morris-Davies Aylin C AC Schaeffer Veronique V Christodoulou Evangelos E Howell Steven S Brown Nicholas R NR Dikic Ivan I Rittinger Katrin K

Nature 20131020 7476

Linear ubiquitin chains are important regulators of cellular signalling pathways that control innate immunity and inflammation through nuclear factor (NF)-κB activation and protection against tumour necrosis factor-α-induced apoptosis. They are synthesized by HOIP, which belongs to the RBR (RING-between-RING) family of E3 ligases and is the catalytic component of LUBAC (linear ubiquitin chain assembly complex), a multisubunit E3 ligase. RBR family members act as RING/HECT hybrids, employing RING ...[more]

PMID: 24141947

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Project description:UnlabelledLinear ubiquitination is an atypical posttranslational modification catalyzed by the linear-ubiquitin-chain assembly complex (LUBAC), containing HOIP, HOIL-1L, and Sharpin. LUBAC facilitates NF-?B activation and inflammation upon receptor stimulation by ligating linear ubiquitin chains to critical signaling molecules. Indeed, linear-ubiquitination-dependent signaling is essential to prevent pyogenic bacterial infections that can lead to death. While linear ubiquitination is essential for intracellular receptor signaling upon microbial infection, this response must be measured and stopped to avoid tissue damage and autoimmunity. While LUBAC is activated upon bacterial stimulation, the mechanisms regulating LUBAC activity in response to bacterial stimuli have remained elusive. We demonstrate that LUBAC activity itself is downregulated through ubiquitination, specifically, ubiquitination of the catalytic subunit HOIP at the carboxyl-terminal lysine 1056. Ubiquitination of Lys1056 dynamically altered HOIP conformation, resulting in the suppression of its catalytic activity. Consequently, HOIP Lys1056-to-Arg mutation led not only to persistent LUBAC activity but also to prolonged NF-?B activation induced by bacterial lipopolysaccharide-mediated Toll-like receptor 4 (TLR4) stimulation, whereas it showed no effect on NF-?B activation induced by CD40 stimulation. This study describes a novel posttranslational regulation of LUBAC-mediated linear ubiquitination that is critical for specifically directing TLR4-mediated NF-?B activation.ImportancePosttranslational modification of proteins enables cells to respond quickly to infections and immune stimuli in a tightly controlled manner. Specifically, covalent modification of proteins with the small protein ubiquitin is essential for cells to initiate and terminate immune signaling in response to bacterial and viral infection. This process is controlled by ubiquitin ligase enzymes, which themselves must be regulated to prevent persistent and deleterious immune signaling. However, how this regulation is achieved is poorly understood. This paper reports a novel ubiquitination event of the atypical ubiquitin ligase HOIP that is required to terminate bacterial lipopolysaccharide (LPS)-induced TLR4 immune signaling. Ubiquitination causes the HOIP ligase to undergo a conformational change, which blocks its enzymatic activity and ultimately terminates LPS-induced TLR4 signaling. These findings provide a new mechanism for controlling HOIP ligase activity that is vital to properly regulate a proinflammatory immune response.

Dataset Information

Structural basis for ligase-specific conjugation of linear ubiquitin chains by HOIP.

Publications

Structural basis for ligase-specific conjugation of linear ubiquitin chains by HOIP.

Similar Datasets

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