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The deubiquitinase TRABID stabilizes the K29/K48-specific E3 ubiquitin ligase HECTD1.

ABSTRACT: Ubiquitin is a versatile posttranslational modification, which is covalently attached to protein targets either as a single moiety or as a ubiquitin chain. In contrast to K48 and K63-linked chains, which have been extensively studied, the regulation and function of most atypical ubiquitin chains are only starting to emerge. The deubiquitinase TRABID/ZRANB1 is tuned for the recognition and cleavage of K29 and K33-linked chains. Yet, substrates of TRABID and the cellular functions of these atypical ubiquitin signals remain unclear. We determined the interactome of two TRABID constructs rendered catalytic dead either through a point mutation in the catalytic cysteine residue or through removal of the OTU catalytic domain. We identified 50 proteins trapped by both constructs and which therefore represent candidate substrates of TRABID. The E3 ubiquitin ligase HECTD1 was then validated as a substrate of TRABID and used UbiCREST and Ub-AQUA proteomics to show that HECTD1 preferentially assembles K29- and K48-linked ubiquitin chains. Further in vitro autoubiquitination assays using ubiquitin mutants established that while HECTD1 can assemble short homotypic K29 and K48-linked chains, it requires branching at K29/K48 in order to achieve its full ubiquitin ligase activity. We next used transient knockdown and genetic knockout of TRABID in mammalian cells in order to determine the functional relationship between TRABID and HECTD1. This revealed that upon TRABID depletion, HECTD1 is readily degraded. Thus, this study identifies HECTD1 as a mammalian E3 ligase that assembles branched K29/K48 chains and also establishes TRABID-HECTD1 as a DUB/E3 pair regulating K29 linkages.

SUBMITTER: Harris LD

PROVIDER: S-EPMC7948964 | biostudies-literature |

REPOSITORIES: biostudies-literature

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The deubiquitinase TRABID stabilises the K29/K48-specific E3 ubiquitin ligase HECTD1

Project description:The OTU deubiquitinase TRABID is highly tuned for the recognition and cleavage of K29 and K33-linked ubiquitin chains. Yet the cellular functions of these atypical ubiquitin signals remain unclear. Here, we compared the interactome of two different catalytically-dead TRABID constructs, one that lacks the OTU domain and the other a single point mutant that is catalytically inactive. Since both constructs also act as ubiquitin trapping mutants, this approach was used to differentiate between interactors and substrates. The E3 ubiquitin ligase HECTD1 was confirmed as a TRABID substrate, and using UbiCREST and Ubiquitin-AQUA proteomics, we determined that HECTD1 preferentially assembles K29- and K48-linked ubiquitin chains. Further in vitro autoubiquitination assays using ubiquitin mutants established that in contrast to UBE3C, HECTD1 requires the formation of branched K29/K48-linked chains for its full activity. Finally, we used transient knockdown and genetic knock out of TRABID in mammalian cells to show that TRABID stabilises HECTD1 protein levels. This study identifies TRABID-HECTD1 as a K29-specific DUB/E3 pair and provides novel insights on the assembly of branched ubiquitin signals.

2021-06-23 | PXD022703 | Pride

Specific targeting of the deubiquitinase and E3 ligase families with engineered ubiquitin variants.

Project description:The ubiquitin proteasome system (UPS) has garnered much attention due to its potential for the development of therapeutics. Following a successful clinical application of general proteasome inhibitors much effort has been devoted to targeting individual UPS components including E3 enzymes and deubiquitinases that control specificity of ubiquitination. Our group has developed a novel approach for targeting the UPS proteins using engineered ubiquitin variants (Ubvs). These drug-like proteins can serve as valuable tools to study biological function of UPS components and assist in the development of small molecules for clinical use. In this review, we summarize studies of Ubvs targeting members of three major families, including deubiquitinases, HECT E3 ligases, and CRL E3 ligases. In particular, we focus on Ubv binding mechanisms, structural studies, and effects on enzyme function. Furthermore, new insights gained from the Ubvs are discussed in the context of small molecule studies.

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VPS34 K29/K48 branched ubiquitination governed by UBE3C and TRABID regulates autophagy, proteostasis and liver metabolism.

Project description:The ubiquitin-proteasome system (UPS) and autophagy are two major quality control processes whose impairment is linked to a wide variety of diseases. The coordination between UPS and autophagy remains incompletely understood. Here, we show that ubiquitin ligase UBE3C and deubiquitinating enzyme TRABID reciprocally regulate K29/K48-branched ubiquitination of VPS34. We find that this ubiquitination enhances the binding of VPS34 to proteasomes for degradation, thereby suppressing autophagosome formation and maturation. Under ER and proteotoxic stresses, UBE3C recruitment to phagophores is compromised with a concomitant increase of its association with proteasomes. This switch attenuates the action of UBE3C on VPS34, thereby elevating autophagy activity to facilitate proteostasis, ER quality control and cell survival. Specifically in the liver, we show that TRABID-mediated VPS34 stabilization is critical for lipid metabolism and is downregulated during the pathogenesis of steatosis. This study identifies a ubiquitination type on VPS34 and elucidates its cellular fate and physiological functions in proteostasis and liver metabolism.

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The E3 ubiquitin ligase HECTD1 contributes to cell proliferation through an effect on mitosis.

Project description:The cell cycle is tightly regulated by protein phosphorylation and ubiquitylation events. During mitosis, the multi-subunit cullin-RING E3 ubiquitin ligase APC/c functions as a molecular switch which signals for one cell to divide into two daughter cells, through the ubiquitylation and proteasomal degradation of mitotic cyclins. The contributions of other E3 ligase families during cell cycle progression remain less well understood. Similarly, the roles of ubiquitin chain types beyond homotypic K48 chains in S-phase or branched K11/K48 chains during mitosis, also remain to be fully determined. Our recent findings that HECTD1 ubiquitin ligase activity assembles branched K29/K48 ubiquitin linkages prompted us to evaluate HECTD1 function during the cell cycle. We used transient knockdown and genetic knockout to show that HECTD1 depletion in HEK293T and HeLa cells decreases cell number and we established that this is mediated through loss of ubiquitin ligase activity. Interestingly, we found that HECTD1 depletion increases the proportion of cells with aligned chromosomes (Prometa/Metaphase) and we confirmed this molecularly using phospho-Histone H3 (Ser28) as a marker of mitosis. Time-lapse microscopy of NEBD to anaphase onset established that HECTD1-depleted cells take on average longer to go through mitosis. In line with this data, HECTD1 depletion reduced the activity of the Spindle Assembly Checkpoint, and BUB3, a component of the Mitosis Checkpoint Complex, was identified as novel HECTD1 interactor. BUB3, BUBR1 or MAD2 protein levels remained unchanged in HECTD1-depleted cells. Overall, this study reveals a novel putative role for HECTD1 during mitosis and warrants further work to elucidate the mechanisms involved.

| S-EPMC9343455 | biostudies-literature

Ubiquitin Specific Peptidase 15 (USP15) suppresses glioblastoma cell growth via stabilization of HECTD1 E3 ligase attenuating WNT pathway activity.

Project description:Expression based prediction of new genomic alterations in glioblastoma identified the de-ubiquitinase Ubiquitin Specific Peptidase 15 (USP15) as potential tumor suppressor gene associated with genomic deletions (11%). Ectopic expression of USP15 in glioblastoma cell-lines reduced colony formation and growth in soft agar, while overexpression of its functional mutant had the opposite effect. Evaluation of the protein binding network of USP15 by Mass Spectrometry in glioblastoma cells uncovered eight novel interacting proteins, including HECT Domain Containing E3 Ubiquitin Protein Ligase 1 (HECTD1), whose mouse homologue has been associated with an inhibitory effect on the WNT-pathway. USP15 de-ubiquitinated and thereby stabilized HECTD1 in glioblastoma cells, while depletion of USP15 led to decreased HECTD1 protein levels. Expression of USP15 in glioblastoma cells attenuated WNT-pathway activity, while expression of the functional mutant enhanced the activity. Modulation of HECTD1 expression pheno-copied the effects observed for USP15. In accordance, human glioblastoma display a weak but significant negative correlation between USP15 and AXIN2 expression. Taken together, the data provide evidence that USP15 attenuates the canonical WNT pathway mediated by stabilization of HECTD1, supporting a tumor suppressing role of USP15 in a subset of glioblastoma.

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Interplay between bacterial deubiquitinase and ubiquitin E3 ligase regulates ubiquitin dynamics on Legionella phagosomes.

Project description:Legionella pneumophila extensively modulates the host ubiquitin network to create the Legionella-containing vacuole (LCV) for its replication. Many of its virulence factors function as ubiquitin ligases or deubiquitinases (DUBs). Here, we identify Lem27 as a DUB that displays a preference for diubiquitin formed by K6, K11, or K48. Lem27 is associated with the LCV where it regulates Rab10 ubiquitination in concert with SidC and SdcA, two bacterial E3 ubiquitin ligases. Structural analysis of the complex formed by an active fragment of Lem27 and the substrate-based suicide inhibitor ubiquitin-propargylamide (PA) reveals that it harbors a fold resembling those in the OTU1 DUB subfamily with a Cys-His catalytic dyad and that it recognizes ubiquitin via extensive hydrogen bonding at six contact sites. Our results establish Lem27 as a DUB that functions to regulate protein ubiquitination on L. pneumophila phagosomes by counteracting the activity of bacterial ubiquitin E3 ligases.

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The E3 ubiquitin ligase Rnf8 stabilizes Tpp1 to promote telomere end protection.

Project description:The mammalian shelterin component TPP1 has essential roles in telomere maintenance and, together with POT1, is required for the repression of DNA damage signaling at telomeres. Here we show that in Mus musculus, the E3 ubiquitin ligase Rnf8 localizes to uncapped telomeres and promotes the accumulation of DNA damage proteins 53Bp1 and ?-H2ax. In the absence of Rnf8, Tpp1 is unstable, resulting in telomere shortening and chromosome fusions through the alternative nonhomologous end-joining (A-NHEJ) repair pathway. The Rnf8 RING-finger domain is essential for Tpp1 stability and retention at telomeres. Rnf8 physically interacts with Tpp1 to generate Ubc13-dependent Lys63 polyubiquitin chains that stabilize Tpp1 at telomeres. The conserved Tpp1 residue Lys233 is important for Rnf8-mediated Tpp1 ubiquitylation and localization to telomeres. Thus, Tpp1 is a newly identified substrate for Rnf8, indicating a previously unrecognized role for Rnf8 in telomere end protection.

| S-EPMC3657743 | biostudies-literature

Deubiquitinase ubiquitin-specific protease 9X regulates the stability and function of E3 ubiquitin ligase ring finger protein 115 in breast cancer cells.

Project description:The E3 ubiquitin ligase ring finger protein 115 (RNF115) is overexpressed in more than half of human breast tumors and is implicated in the pathogenesis and progression of breast cancer. However, the mechanism behind RNF115 overexpression in breast tumors remains largely unknown. Here we report that ubiquitin-specific protease 9X (USP9X), a substrate-specific deubiquitinating enzyme, stabilizes RNF115 and thereby regulates its biological functions in breast cancer cells. Immunoprecipitation and GST pull-down assays showed that USP9X interacted with RNF115. Depletion of RNF115 by siRNAs or overexpression of RNF115 did not significantly affect USP9X expression. In contrast, knockdown of USP9X in breast cancer cells by siRNAs reduced RNF115 protein abundance, which was partially restored following treatment with proteasome inhibitor MG-132. Moreover, depletion of USP9X reduced the half-life of RNF115 and increased its ubiquitination. Conversely, overexpression of USP9X resulted in an accumulation of RNF115 protein, accompanied by a decrease in its ubiquitination. RNF115 mRNA levels were unaffected by overexpression or knockdown of USP9X. Furthermore, USP9X protein expression levels correlated positively with RNF115 in breast cancer cell lines and breast tumor samples. Importantly, reintroduction of RNF115 in USP9X-depleted cells partially rescued the reduced proliferation, migration, and invasion of breast cancer cells by USP9X knockdown. Collectively, these findings indicate that USP9X is a stabilizer of RNF115 protein and that the USP9X-RNF115 signaling axis is implicated in the breast cancer malignant phenotype.

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CUL5-ARIH2 E3-E3 ubiquitin ligase structure reveals cullin-specific NEDD8 activation.

Project description:An emerging mechanism of ubiquitylation involves partnering of two distinct E3 ligases. In the best-characterized E3-E3 pathways, ARIH-family RING-between-RING (RBR) E3s ligate ubiquitin to substrates of neddylated cullin-RING E3s. The E3 ARIH2 has been implicated in ubiquitylation of substrates of neddylated CUL5-RBX2-based E3s, including APOBEC3-family substrates of the host E3 hijacked by HIV-1 virion infectivity factor (Vif). However, the structural mechanisms remained elusive. Here structural and biochemical analyses reveal distinctive ARIH2 autoinhibition, and activation on assembly with neddylated CUL5-RBX2. Comparison to structures of E3-E3 assemblies comprising ARIH1 and neddylated CUL1-RBX1-based E3s shows cullin-specific regulation by NEDD8. Whereas CUL1-linked NEDD8 directly recruits ARIH1, CUL5-linked NEDD8 does not bind ARIH2. Instead, the data reveal an allosteric mechanism. NEDD8 uniquely contacts covalently linked CUL5, and elicits structural rearrangements that unveil cryptic ARIH2-binding sites. The data reveal how a ubiquitin-like protein induces protein-protein interactions indirectly, through allostery. Allosteric specificity of ubiquitin-like protein modifications may offer opportunities for therapeutic targeting.

| S-EPMC8460447 | biostudies-literature

The E3 ubiquitin ligase HectD1 suppresses EMT and metastasis by targeting the +TIP protein ACF7 for degradation

Project description:Cancer cells exploit the epithelial-to-mesenchymal transition (EMT) program toward metastasis. Cytoskeletal regulators are dually required in mesenchymal cells by promoting EMT-induced migration and sustaining the EMT program itself. In search for novel regulators of metastasis, we conducted an shRNA screen targeting a class of microtubule regulators, the plus-end tracking proteins (+TIPs). We show that the +TIP ACF7 is required for both the maintenance of EMT and to promote migration. We identified HectD1 as a potent E3 ubiquitin ligase mediating ACF7 degradation. Depletion of HectD1 robustly increases ACF7 protein levels and this is sufficient to enhance migration and EMT in cells, as well as facilitate metastasis in vivo. Ours results report the HectD1/ACF7 axis as a novel regulator of metastasis of breast cancer cells.

2018-01-03 | GSE100092 | GEO

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