Ubiquitin receptors are required for substrate-mediated activation of the proteasome's unfolding ability
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo Sapiens (human)
SUBMITTER: Daniel A. Kraut
PROVIDER: PXD010803 | JPOST Repository | Wed Sep 25 00:00:00 BST 2019
REPOSITORIES: jPOST
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Project description:The ubiquitin-proteasome system (UPS) is responsible for the bulk of protein degradation in eukaryotic cells, but the factors that cause different substrates to be unfolded and degraded to different extents are still poorly understood. We previously showed that polyubiquitinated substrates were degraded with greater processivity (with a higher tendency to be unfolded and degraded than released) than ubiquitin-independent substrates. Thus, even though ubiquitin chains are removed before unfolding and degradation occur, they affect the unfolding of a protein domain. How do ubiquitin chains activate the proteasome's unfolding ability? We investigated the roles of the three intrinsic proteasomal ubiquitin receptors - Rpn1, Rpn10 and Rpn13 - in this activation. We find that these receptors are required for substrate-mediated activation of the proteasome's unfolding ability. Rpn13 plays the largest role, but there is also partial redundancy between receptors. The architecture of substrate ubiquitination determines which receptors are needed for maximal unfolding ability, and, in some cases, simultaneous engagement of ubiquitin by multiple receptors may be required. Our results suggest physical models for how ubiquitin receptors communicate with the proteasomal motor proteins.
| S-EPMC6787058 | biostudies-literature
Project description:Protein ubiquitination plays an essential role in cellular physiology. Contrary to canonical ubiquitination at internal lysine residues, the physiological functions of N-terminal ubiquitination remain enigmatic. To identify endogenous N-terminally-ubiquitinated substrates, we discovered four novel monoclonal antibodies that selectively recognize tryptic peptides with an N-terminal diglycine remnant, corresponding to sites of N-terminal ubiquitination. Importantly, these antibodies do not recognize isopeptide-linked diglycine (ubiquitin) modifications on lysine. We solved the structure of one such antibody bound to a Gly-Gly-Met peptide to reveal the molecular basis for its selective recognition. These antibodies were used in conjunction with mass spectrometry proteomics to map N-terminal ubiquitination sites on endogenous substrates of UBE2W. These substrates included UCHL1 and UCHL5, where N-terminal ubiquitination distinctly altered deubiquitinase (DUB) activity. This new antibody toolkit for global profiling of endogenous N-terminal ubiquitination sites will enable future work to decipher the physiological functions of N-terminal ubiquitination.
2020-11-30 | MSV000086537 | MassIVE
Project description:Determination of ubiquitination sites on an artificial substrate consisting of an Neh2 domain from Nrf2 that has been modified to be able to be ubiquitinated with three different E3 ligase systems, Ubr1 (which forms K48 linkages), Rsp5 (which forms K63 linkages) and Cul3/Rbx1/Keap1 (which forms branched linkages).
2024-01-05 | MSV000093780 | MassIVE
Project description:MLL-fusions are potent oncogenes that initiate aggressive forms of acute leukemia. As aberrant transcriptional regulators, MLL-fusion proteins alter gene expression in hematopoietic cells through interactions with the histone H3 lysine 79 (H3K79) methyltransferase DOT1L. Notably, interference with MLL-fusion cofactors like DOT1L is an emerging therapeutic strategy in this disease. Here we identify the histone H2B E3 ubiquitin ligase RNF20 as an additional requirement for MLL-fusion-mediated leukemogenesis. Suppressing the expression of Rnf20 in diverse models of MLL-rearranged leukemia leads to inhibition of cell proliferation; under tissue culture conditions as well as in vivo. Rnf20 knockdown leads to reduced expression of MLL-fusion target genes, including Hoxa9 and Meis1; effects that resemble Dot1l-inhibition. Using ChIP-seq, we found that H2B ubiquitination (H2Bub) is enriched in the body of MLL-fusion target genes, correlating with sites of H3K79 methylation and transcription elongation. Furthermore, we found that Rnf20 is required to maintain local levels of H3K79 di-methylation by Dot1l at Hoxa9 and Meis1. These findings support a model whereby co-transcriptional recruitment of Rnf20 at MLL-fusion target genes leads to amplification of Dot1l-mediated H3K79 methylation, thereby rendering leukemia cells dependent on Rnf20 to maintain their oncogenic transcriptional program. Examination of gene expression profiles upon RNF20 RNAi in MLL-AF9 acute myeloid leukemia cells
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Project description:Protein ubiquitination, an evolutionarily conserved post-translational modification process in eukaryotes, and plays an important role in many biological processes. Aspergillus nidulans, a model filamentous fungus, contributes to our understanding of cellular physiology, metabolism and genetics, but its ubiquitination remains widely unknown. In this study, the ubiquitination sites in the proteome of A. nidulans were identified using a highly sensitive mass spectrometry combined with immuno-affinity enrichment of ubiquitinated peptides. The 4816 ubiquitination sites were identified in 1913 ubiquitinated proteins, accounting for 18.1% of total proteins in A. nidulans. Bioinformatic analysis suggested that the ubiquitinated proteins are associated with a number of biological functions and display various sub-cellular localizations. Meanwhile, seven motifs were revealed from the ubiquitinated peptides, and significantly over-presented in different pathways. This study presents a first proteome-wide view of ubiquitination in filamentous fungi, and provides an initial framework for exploring the physiological role of lysine ubiquitination in filamentous fungi.
2015-09-10 | PXD002299 | Pride
Project description:The TRIM37 gene is mutatedin Mulbery nanism, a rare autosomal recessive disorder, and is in the 17q23 chromosomal region that is amplified in up to ~40% of breast cancers. Trim37 contains a RING finger domain, a hallmark of E3 ubiquitin ligases, but the protein substrate(s) of Trim37 is unknown. Mono-ubiquitination of histone H2A is a chromatin modification associated with transcriptional repression and here we report that Trim37 is an H2A ubiquitin ligase. Genome-wide Chip-CHIP experiments indicate that in human breast cancer cells containing amplified 17q23, Trim37 is bound to the promoters of many tumor suppressor genes. RNA interference (RNAi)-mediated knockdown of Trim37 results in loss of ubiquitinated H2A, dissociation of PRC1 and PRC2, and transcriptional reactivation of silenced genes. Knockdown of Trim37 in human breast cancer cells containing amplified 17q23 substantially decreases tumor growth in mouse xenografts. Collectively, our results reveal Trim37 as a new H2A ubiquitin ligase that is overexpressed in a subset of breast cancers and redirects PRC2 to silence tumor suppressors and other genes resulting in oncogenesis. Identification of TRIM37 Binding targets in MCF7 cells from the two replicate experiments
2014-10-06 | E-GEOD-48196 | biostudies-arrayexpress
Project description:MLL-fusions are potent oncogenes that initiate aggressive forms of acute leukemia. As aberrant transcriptional regulators, MLL-fusion proteins alter gene expression in hematopoietic cells through interactions with the histone H3 lysine 79 (H3K79) methyltransferase DOT1L. Notably, interference with MLL-fusion cofactors like DOT1L is an emerging therapeutic strategy in this disease. Here we identify the histone H2B E3 ubiquitin ligase RNF20 as an additional requirement for MLL-fusion-mediated leukemogenesis. Suppressing the expression of Rnf20 in diverse models of MLL-rearranged leukemia leads to inhibition of cell proliferation; under tissue culture conditions as well as in vivo. Rnf20 knockdown leads to reduced expression of MLL-fusion target genes, including Hoxa9 and Meis1; effects that resemble Dot1l-inhibition. Using ChIP-seq, we found that H2B ubiquitination (H2Bub) is enriched in the body of MLL-fusion target genes, correlating with sites of H3K79 methylation and transcription elongation. Furthermore, we found that Rnf20 is required to maintain local levels of H3K79 di-methylation by Dot1l at Hoxa9 and Meis1. These findings support a model whereby co-transcriptional recruitment of Rnf20 at MLL-fusion target genes leads to amplification of Dot1l-mediated H3K79 methylation, thereby rendering leukemia cells dependent on Rnf20 to maintain their oncogenic transcriptional program.
2013-02-19 | GSE43725 | GEO
Project description:Dysregulated microglia are intimately involved in neurodegeneration including Alzheimer’s disease (AD) pathogenesis, but the mechanisms controlling pathogenic microglial gene expression remain poorly understood. The transcription factor CCAAT/enhancer binding protein beta (c/EBPß) regulates pro-inflammatory genes in microglia and is upregulated in AD. We show expression of c/EBPß in microglia is regulated post-translationally by the ubiquitin ligase COP1 (also called RFWD2). Ubiquitination of c/EBPß by COP1 targets it for proteasomal degradation. In the absence of COP1, c/EBPß accumulates rapidly and drives a potent pro-inflammatory and ApoE gene-expression program, evidenced by increased neurotoxicity in microglia-neuronal co-cultures. Antibody blocking studies reveal that neurotoxicity is almost entirely attributable to complement. Remarkably, loss of a single allele of Cebpb prevented the pro-inflammatory phenotype. COP1-deficient microglia markedly accelerated tau-mediated neurodegeneration in a mouse model where elevated ApoE plays a deleterious role. Collectively, these results identify c/EBPß as a potential therapeutic target for inflammation-driven neurodegeneration.
2020-08-14 | GSE145454 | GEO
Project description:The NLRP3 inflammasome, a pivotal component of innate immunity, has been implicated in various inflammatory disorders. The ubiquitin-editing enzyme A20 is well known to regulate inflammation and maintain homeostasis. However, the precise molecular mechanisms by which A20 modulates the NLRP3 inflammasome remain poorly understood. Here our study revealed that macrophages deficient in A20 exhibit increased protein abundance and elevated mRNA level of NIMA-related kinase 7 (NEK7). Importantly, A20 directly binds with NEK7, mediating its K48-linked ubiquitination, thereby targeting NEK7 for proteasomal degradation. Our results demonstrate that A20 enhance the ubiquitination of NEK7 at K189 and K293 ubiquitinated sites, with K189 playing a crucial role in the binding of NEK7 to A20, albeit not significantly influencing the interaction between NEK7 and NLRP3. Furthermore, A20 disrupts the association of NEK7 with the NLRP3 complex, potentially through the OTU domain and/or synergistic effect of ZnF4 and ZnF7 motifs. Significantly, NEK7 deletion markedly attenuates the activation of the NLRP3 inflammasome in A20-deficient conditions, both in vitro and in vivo. This study uncovers a new mechanism by which A20 inhibits the NLRP3 inflammasome.
2024-07-03 | GSE253265 | GEO
Project description:The Androgen Receptor (AR) is a pivotal protein in human physiology, exerting significant influence on both male and female physiology (PMID: 18434134, 25905231). Functioning as a nuclear transcription factor, AR binds to testosterone, translocates to the nucleus, and subsequently regulates the expression of numerous genes, impacting vital cellular processes such as cell proliferation, differentiation, and apoptosis (PMID: 4810760, 25237629). The prominent role of AR in human physiology is particularly notable in the context of prostate cancer initiation, where aberrant AR signaling has been identified as a key driver in tumorigenesis (PMID: 4810760, 27057074, 37429011). However, despite the considerable success of the current anti-androgen therapeutic approach, it faces the formidable challenge of drug resistance, significantly limiting the clinical outcome for patients and necessitating the urgent development of new therapeutic approaches to overcome resistance (PMID: 26563462, 24881730, 31363002, 35582713). Notably, one key feature of antiandrogen resistance is the sustained or enhanced AR signaling observed in many resistant tumors (PMID: 26563462, 34449248, 23580326), although the underlying molecular mechanisms remain largely unclear. Protein degradation, with ubiquitination at its core, plays a critical role in cell functionality, ensuring the elimination of redundant and harmful proteins (PMID: 16738015, 33634825). This intricate process involves the attachment of small proteins called ubiquitin to target proteins, marking them for degradation. Dysregulation of ubiquitination can lead to the accumulation of oncogenic proteins, contributing to tumorigenesis and therapy resistance in various cancers (PMID: 32296023, 33004065). The degradation of proteins is a complex process that involves the coordination of E1, E2 and E3 enzymes, with E3 enzymes binding to the target protein (PMID: 21111229, 20930542). Logically, research has focused on finding E3s targeting AR for degradation but has overlooked the role that E2s play in the ubiquitination process. In recent years, E2s have been shown to dictate the how and where ubiquitin gets attached in the target protein, dictating the fate of the protein (PMID: 27002219, 19851334). Therefore, finding the E2 involved in the degradation of AR can prove to be essential. In this study, we conducted an in vivo library screening approach and identified UBE2J1 as the bona fide E2 ubiquitin conjugating enzyme for AR ubiquitination. Our results demonstrated that the frequent loss of UBE2J1 in prostate cancer leads to dysregulated and impaired AR ubiquitination and degradation. Consequently, this promotes the accumulation of AR proteins and confers resistance to antiandrogen treatment in UBE2J1-deficient prostate cancer cells. To address this, we developed an innovative ubiquitination-based AR degrader that effectively restores AR ubiquitination, thereby resensitizing prostate cancer cells to antiandrogen therapy. These findings not only unveil the pivotal role of UBE2J1 as the crucial E2 ubiquitin conjugating enzyme for AR degradation but also shed light on a novel mechanism through which advanced prostate cancer cells upregulate AR protein levels, thereby acquiring resistance to existing antiandrogen therapy. These novel insights hold the potential to inform the development of more effective therapeutic strategies against advanced prostate cancers.
2024-02-09 | GSE240305 | GEO