RESUMO
Polyubiquitination by E2 and E3 enzymes is crucial to cell cycle control, epigenetic regulation, and development. The hallmark of the E2 family is the ubiquitin (Ub)-conjugating (UBC) domain that forms a dynamic thioester conjugate with ubiquitin (E2~Ub). Numerous studies have focused on E2 surfaces, such as the N-terminal and crossover helices, that directly interact with an E3 or the conjugated ubiquitin to stabilize the active, "closed" state of the E2~Ub. However, it remains unclear how other E2 surfaces regulate ubiquitin transfer. Here, we demonstrate the helix-turn-helix (HTH) motif of the UBC tunes the intrinsic polyubiquitination activity through distinct functions in different E2s. Interestingly, the E2HTH motif is repurposed in UBE2S and UBE2R2 to interact with the conjugated or acceptor ubiquitin, respectively, modulating ubiquitin transfer. Furthermore, we propose that Anaphase-Promoting Complex/Cyclosome binding to the UBE2SHTH reduces the conformational space of the flexible E2~Ub, demonstrating an atypical E3-dependent activation mechanism. Altogether, we postulate the E2HTH motif evolved to provide new functionalities that can be harnessed by E3s and permits additional regulation to facilitate specific E2-E3-mediated polyubiquitination.
Assuntos
Enzimas de Conjugação de Ubiquitina/química , Motivos de Aminoácidos , Domínio Catalítico , Humanos , Ubiquitina/metabolismo , Enzimas de Conjugação de Ubiquitina/metabolismoRESUMO
Cullin-RING ligases (CRLs) represent the largest E3 ubiquitin ligase family in eukaryotes, and the identification of their substrates is critical to understanding regulation of the proteome. Using genetic and pharmacologic Cullin inactivation coupled with genetic (GPS) and proteomic (QUAINT) assays, we have identified hundreds of proteins whose stabilities or ubiquitylation status are regulated by CRLs. Together, these approaches yielded many known CRL substrates as well as a multitude of previously unknown putative substrates. We demonstrate that one substrate, NUSAP1, is an SCF(Cyclin F) substrate during S and G2 phases of the cell cycle and is also degraded in response to DNA damage. This collection of regulated substrates is highly enriched for nodes in protein interaction networks, representing critical connections between regulatory pathways. This demonstrates the broad role of CRL ubiquitylation in all aspects of cellular biology and provides a set of proteins likely to be key indicators of cellular physiology.
Assuntos
Genoma Humano , Proteoma/análise , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitinação , Ciclopentanos/farmacologia , Inibidores Enzimáticos/farmacologia , Humanos , Pirimidinas/farmacologia , Ubiquitina-Proteína Ligases/genéticaRESUMO
Protein ubiquitination is a post-translational modification that entails the covalent attachment of the small protein ubiquitin (Ub), which acts as a signal to direct protein stability, localization, or interactions. The Ub code is written by a family of enzymes called E3 Ub ligases (â¼600 members in humans), which can catalyze the transfer of either a single ubiquitin or the formation of a diverse array of polyubiquitin chains. This code can be edited or erased by a different set of enzymes termed deubiquitinases (DUBs; â¼100 members in humans). While enzymes from these distinct families have seemingly opposing activities, certain E3-DUB pairings can also synergize to regulate vital cellular processes like gene expression, autophagy, innate immunity, and cell proliferation. In this review, we highlight recent studies describing Ub ligase-DUB interactions and focus on their relationships.
RESUMO
Oncogenic mutations in the small GTPase Ras are highly prevalent in cancer, but an understanding of the vulnerabilities of these cancers is lacking. We undertook a genome-wide RNAi screen to identify synthetic lethal interactions with the KRAS oncogene. We discovered a diverse set of proteins whose depletion selectively impaired the viability of Ras mutant cells. Among these we observed a strong enrichment for genes with mitotic functions. We describe a pathway involving the mitotic kinase PLK1, the anaphase-promoting complex/cyclosome, and the proteasome that, when inhibited, results in prometaphase accumulation and the subsequent death of Ras mutant cells. Gene expression analysis indicates that reduced expression of genes in this pathway correlates with increased survival of patients bearing tumors with a Ras transcriptional signature. Our results suggest a previously underappreciated role for Ras in mitotic progression and demonstrate a pharmacologically tractable pathway for the potential treatment of cancers harboring Ras mutations.
Assuntos
Neoplasias do Colo/metabolismo , Mitose , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas ras/genética , Proteínas ras/metabolismo , Animais , Proteínas de Ciclo Celular/antagonistas & inibidores , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Feminino , Genoma Humano , Humanos , Camundongos , Camundongos Nus , Mutação , Transplante de Neoplasias , Inibidores de Proteassoma , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas/antagonistas & inibidores , Proteínas Proto-Oncogênicas p21(ras) , Interferência de RNA , Transdução de Sinais , Transplante Heterólogo , Quinase 1 Polo-LikeRESUMO
mRNA display is revolutionizing peptide drug discovery through its ability to quickly identify potent peptide binders of therapeutic protein targets. Methods to expand the chemical diversity of display libraries are continually needed to increase the likelihood of identifying clinically relevant peptide ligands. Orthogonal aminoacyl-tRNA synthetases (ORSs) have proven utility in cellular genetic code expansion, but are relatively underexplored for in vitro translation (IVT) and mRNA display. Herein, we demonstrate that the promiscuous ORS p-CNF-RS can incorporate noncanonical amino acids at amber codons in IVT, including the novel substrate p-cyanopyridylalanine (p-CNpyrA), to enable a pyridine-thiazoline (pyr-thn) macrocyclization in mRNA display. Pyr-thn-based selections against the deubiquitinase USP15 yielded a potent macrocyclic binder that exhibits good selectivity for USP15 and close homologues over other ubiquitin-specific proteases (USPs). Overall, this work exemplifies how promiscuous ORSs can both expand side chain diversity and provide structural novelty in mRNA display libraries through a heterocycle forming macrocyclization.
Assuntos
Aminoacil-tRNA Sintetases , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Aminoacil-tRNA Sintetases/metabolismo , Código Genético , Aminoácidos/química , Peptídeos/genética , RNA de Transferência/metabolismoRESUMO
The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase and critical regulator of cell cycle progression. Despite its vital role, it has remained challenging to globally map APC/C substrates. By combining orthogonal features of known substrates, we predicted APC/C substrates in silico. This analysis identified many known substrates and suggested numerous candidates. Unexpectedly, chromatin regulatory proteins are enriched among putative substrates, and we show experimentally that several chromatin proteins bind APC/C, oscillate during the cell cycle, and are degraded following APC/C activation, consistent with being direct APC/C substrates. Additional analysis revealed detailed mechanisms of ubiquitylation for UHRF1, a key chromatin regulator involved in histone ubiquitylation and DNA methylation maintenance. Disrupting UHRF1 degradation at mitotic exit accelerates G1-phase cell cycle progression and perturbs global DNA methylation patterning in the genome. We conclude that APC/C coordinates crosstalk between cell cycle and chromatin regulatory proteins. This has potential consequences in normal cell physiology, where the chromatin environment changes depending on proliferative state, as well as in disease.
Assuntos
Ciclossomo-Complexo Promotor de Anáfase/metabolismo , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Cromatina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ciclossomo-Complexo Promotor de Anáfase/fisiologia , Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas Estimuladoras de Ligação a CCAAT/fisiologia , Ciclo Celular/fisiologia , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular , Cromatina/genética , Simulação por Computador , Células HEK293 , Células HeLa , Humanos , Processamento de Proteína Pós-Traducional , Fatores de Transcrição/metabolismo , Ubiquitina-Proteína Ligases/fisiologia , UbiquitinaçãoRESUMO
Ovarian cancer is the deadliest gynecological malignancy of the reproductive organs in the United States. Cyclin-dependent kinase 1 (CDK1) is an important cell cycle regulatory protein that specifically controls the G2/M phase transition of the cell cycle. RO-3306 is a selective, ATP-competitive, and cell-permeable CDK1 inhibitor that shows potent anti-tumor activity in multiple pre-clinical models. In this study, we investigated the effect of CDK1 expression on the prognosis of patients with ovarian cancer and the anti-tumorigenic effect of RO-3306 in both ovarian cancer cell lines and a genetically engineered mouse model of high-grade serous ovarian cancer (KpB model). In 147 patients with epithelial ovarian cancer, the overexpression of CDK1 was significantly associated with poor prognosis compared with a low expression group. RO-3306 significantly inhibited cellular proliferation, induced apoptosis, caused cellular stress, and reduced cell migration. The treatment of KpB mice with RO-3306 for four weeks showed a significant decrease in tumor weight under obese and lean conditions without obvious side effects. Overall, our results demonstrate that the inhibition of CDK1 activity by RO-3306 effectively reduces cell proliferation and tumor growth, providing biological evidence for future clinical trials of CDK1 inhibitors in ovarian cancer.
Assuntos
Proteína Quinase CDC2 , Neoplasias Ovarianas , Humanos , Feminino , Camundongos , Animais , Camundongos Transgênicos , Proteína Quinase CDC2/metabolismo , Linhagem Celular Tumoral , Neoplasias Ovarianas/tratamento farmacológico , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/metabolismo , Proliferação de Células , CarcinogêneseRESUMO
The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase and key regulator of cell cycle progression. Since APC/C promotes the degradation of mitotic cyclins, it controls cell cycle-dependent oscillations in cyclin-dependent kinase (CDK) activity. Both CDKs and APC/C control a large number of substrates and are regulated by analogous mechanisms, including cofactor-dependent activation. However, whereas substrate dephosphorylation is known to counteract CDK, it remains largely unknown whether deubiquitinating enzymes (DUBs) antagonize APC/C substrate ubiquitination during mitosis. Here, we demonstrate that Cezanne/OTUD7B is a cell cycle-regulated DUB that opposes the ubiquitination of APC/C targets. Cezanne is remarkably specific for K11-linked ubiquitin chains, which are formed by APC/C in mitosis. Accordingly, Cezanne binds established APC/C substrates and reverses their APC/C-mediated ubiquitination. Cezanne depletion accelerates APC/C substrate degradation and causes errors in mitotic progression and formation of micronuclei. These data highlight the importance of tempered APC/C substrate destruction in maintaining chromosome stability. Furthermore, Cezanne is recurrently amplified and overexpressed in numerous malignancies, suggesting a potential role in genome maintenance and cancer cell proliferation.
Assuntos
Ciclossomo-Complexo Promotor de Anáfase/metabolismo , Instabilidade Cromossômica , Enzimas Desubiquitinantes/metabolismo , Endopeptidases/metabolismo , Mitose , Proteínas de Neoplasias/metabolismo , Neoplasias/metabolismo , Proteólise , Ciclossomo-Complexo Promotor de Anáfase/genética , Enzimas Desubiquitinantes/genética , Endopeptidases/genética , Células HCT116 , Células HEK293 , Células HeLa , Humanos , Micronúcleos com Defeito Cromossômico , Proteínas de Neoplasias/genética , Neoplasias/genética , Neoplasias/patologia , UbiquitinaçãoRESUMO
Since its discovery forty years ago, protein ubiquitination has been an ever-expanding field. Virtually all biological processes are controlled by the post-translational conjugation of ubiquitin onto target proteins. In addition, since ubiquitin controls substrate degradation through the action of hundreds of enzymes, many of which represent attractive therapeutic candidates, harnessing the ubiquitin system to reshape proteomes holds great promise for improving disease outcomes. Among the numerous physiological functions controlled by ubiquitin, the cell cycle is among the most critical. Indeed, the discovery that the key drivers of cell cycle progression are regulated by the ubiquitin-proteasome system (UPS) epitomizes the connection between ubiquitin signaling and proliferation. Since cancer is a disease of uncontrolled cell cycle progression and proliferation, targeting the UPS to stop cancer cells from cycling and proliferating holds enormous therapeutic potential. Ubiquitination is reversible, and ubiquitin is removed from substrates by catalytic proteases termed deubiquitinases or DUBs. While ubiquitination is tightly linked to proliferation and cancer, the role of DUBs represents a layer of complexity in this landscape that remains poorly captured. Due to their ability to remodel the proteome by altering protein degradation dynamics, DUBs play an important and underappreciated role in the cell cycle and proliferation of both normal and cancer cells. Moreover, due to their enzymatic protease activity and an open ubiquitin binding pocket, DUBs are likely to be important in the future of cancer treatment, since they are among the most druggable enzymes in the UPS. In this review we summarize new and important findings linking DUBs to cell cycle and proliferation, as well as to the etiology and treatment of cancer. We also highlight new advances in developing pharmacological approaches to attack DUBs for therapeutic benefit.
Assuntos
Enzimas Desubiquitinantes/metabolismo , Neoplasias/patologia , Ciclo Celular , Enzima Desubiquitinante CYLD/genética , Enzima Desubiquitinante CYLD/metabolismo , Enzimas Desubiquitinantes/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Mitose , Mutação , Neoplasias/genética , Neoplasias/metabolismo , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Ubiquitina Tiolesterase/genética , Ubiquitina Tiolesterase/metabolismo , Peptidase 7 Específica de Ubiquitina/genética , Peptidase 7 Específica de Ubiquitina/metabolismoRESUMO
The maternal embryonic leucine zipper kinase (MELK) has been implicated in the regulation of cancer cell proliferation. RNAi-mediated MELK depletion impairs growth and causes G2/M arrest in numerous cancers, but the mechanisms underlying these effects are poorly understood. Furthermore, the MELK inhibitor OTSSP167 has recently been shown to have poor selectivity for MELK, complicating the use of this inhibitor as a tool compound to investigate MELK function. Here, using a cell-based proteomics technique called multiplexed kinase inhibitor beads/mass spectrometry (MIB/MS), we profiled the selectivity of two additional MELK inhibitors, NVS-MELK8a (8a) and HTH-01-091. Our results revealed that 8a is a highly selective MELK inhibitor, which we further used for functional studies. Resazurin and crystal violet assays indicated that 8a decreases triple-negative breast cancer cell viability, and immunoblotting revealed that impaired growth is due to perturbation of cell cycle progression rather than induction of apoptosis. Using double-thymidine synchronization and immunoblotting, we observed that MELK inhibition delays mitotic entry, which was associated with delayed activation of Aurora A, Aurora B, and cyclin-dependent kinase 1 (CDK1). Following this delay, cells entered and completed mitosis. Using live-cell microscopy of cells harboring fluorescent proliferating cell nuclear antigen, we confirmed that 8a significantly and dose-dependently lengthens G2 phase. Collectively, our results provide a rationale for using 8a as a tool compound for functional studies of MELK and indicate that MELK inhibition delays mitotic entry, likely via transient G2/M checkpoint activation.
Assuntos
Espectrometria de Massas , Mitose , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Histonas/metabolismo , Humanos , Mitose/efeitos dos fármacos , Proteínas de Neoplasias/metabolismo , Fosforilação/efeitos dos fármacos , Proteínas Serina-Treonina Quinases/metabolismo , Neoplasias de Mama Triplo Negativas/enzimologia , Neoplasias de Mama Triplo Negativas/patologiaRESUMO
Methylation of histone H3 lysine 36 (H3K36me) by yeast Set2 is critical for the maintenance of chromatin structure and transcriptional fidelity. However, we do not know the full range of Set2/H3K36me functions or the scope of mechanisms that regulate Set2-dependent H3K36 methylation. Here, we show that the APC/CCDC20 complex regulates Set2 protein abundance during the cell cycle. Significantly, absence of Set2-mediated H3K36me causes a loss of cell cycle control and pronounced defects in the transcriptional fidelity of cell cycle regulatory genes, a class of genes that are generally long, hence highly dependent on Set2/H3K36me for their transcriptional fidelity. Because APC/C also controls human SETD2, and SETD2 likewise regulates cell cycle progression, our data imply an evolutionarily conserved cell cycle function for Set2/SETD2 that may explain why recurrent mutations of SETD2 contribute to human disease.
Assuntos
Ciclossomo-Complexo Promotor de Anáfase/genética , Ciclo Celular/genética , Regulação Fúngica da Expressão Gênica , Metiltransferases/genética , Processamento de Proteína Pós-Traducional , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Transcrição Gênica , Evolução Biológica , Proteínas Cdc20/genética , Proteínas Cdc20/metabolismo , Ciclo Celular/efeitos dos fármacos , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Lisina/metabolismo , Metilação , Metiltransferases/metabolismo , Nocodazol/farmacologia , Proteólise , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Moduladores de Tubulina/farmacologiaRESUMO
The mitotic spindle is composed of dynamic microtubules and associated proteins that together direct chromosome movement during mitosis. The spindle plays a vital role in accurate chromosome segregation fidelity and is a therapeutic target in cancer. Nevertheless, the molecular mechanisms by which many spindle-associated proteins function remains unknown. The nucleolar and spindle-associated protein NUSAP1 is a microtubule-binding protein implicated in spindle stability and chromosome segregation. We show here that NUSAP1 localizes to dynamic spindle microtubules in a unique chromosome-centric pattern, in the vicinity of overlapping microtubules, during metaphase and anaphase of mitosis. Mass spectrometry-based analysis of endogenous NUSAP1 interacting proteins uncovered a cell cycle-regulated interaction between the RanBP2-RanGAP1-UBC9 SUMO E3 ligase complex and NUSAP1. Like NUSAP1 depletion, RanBP2 depletion impaired the response of cells to the microtubule poison Taxol. NUSAP1 contains a conserved SAP domain (SAF-A/B, Acinus, and PIAS). SAP domains are common among many other SUMO E3s, and are implicated in substrate recognition and ligase activity. We speculate that NUSAP1 contributes to accurate chromosome segregation by acting as a co-factor for RanBP2-RanGAP1-UBC9 during cell division.
Assuntos
Segregação de Cromossomos/fisiologia , Proteínas Ativadoras de GTPase/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Chaperonas Moleculares/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Enzimas de Conjugação de Ubiquitina/metabolismo , Segregação de Cromossomos/efeitos dos fármacos , Proteínas Ativadoras de GTPase/genética , Células HeLa , Humanos , Proteínas Associadas aos Microtúbulos/genética , Microtúbulos/genética , Microtúbulos/metabolismo , Chaperonas Moleculares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Paclitaxel/farmacologia , Domínios Proteicos , Fuso Acromático/genética , Fuso Acromático/metabolismo , Enzimas de Conjugação de Ubiquitina/genéticaRESUMO
UBE3A is a HECT domain E3 ubiquitin ligase whose dysfunction is linked to autism, Angelman syndrome, and cancer. Recently, we characterized a de novo autism-linked UBE3A mutant (UBE3AT485A) that disrupts phosphorylation control of UBE3A activity. Through quantitative proteomics and reporter assays, we found that the UBE3AT485A protein ubiquitinates multiple proteasome subunits, reduces proteasome subunit abundance and activity, stabilizes nuclear ß-catenin, and stimulates canonical Wnt signaling more effectively than wild-type UBE3A. We also found that UBE3AT485A activates Wnt signaling to a greater extent in cells with low levels of ongoing Wnt signaling, suggesting that cells with low basal Wnt activity are particularly vulnerable to UBE3AT485A mutation. Ligase-dead UBE3A did not stimulate Wnt pathway activation. Overexpression of several proteasome subunits reversed the effect of UBE3AT485A on Wnt signaling. We also observed that subunits that interact with UBE3A and affect Wnt signaling are located along one side of the 19S regulatory particle, indicating a previously unrecognized spatial organization to the proteasome. Altogether, our findings indicate that UBE3A regulates Wnt signaling in a cell context-dependent manner and that an autism-linked mutation exacerbates these signaling effects. Our study has broad implications for human disorders associated with UBE3A gain or loss of function and suggests that dysfunctional UBE3A might affect additional proteins and pathways that are sensitive to proteasome activity.
Assuntos
Transtorno Autístico/metabolismo , Mutação , Complexo de Endopeptidases do Proteassoma/metabolismo , Inibidores de Proteassoma/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , Via de Sinalização Wnt , beta Catenina/metabolismo , Células HEK293 , Humanos , Complexo de Endopeptidases do Proteassoma/genéticaRESUMO
Cancers with Ras mutations represent a major therapeutic problem. Recent RNAi screens have uncovered multiple nononcogene addiction pathways that are necessary for the survival of Ras mutant cells. Here, we identify the evolutionarily conserved gene enhancer of rudimentary homolog (ERH), in which depletion causes greater toxicity in cancer cells with mutations in the small GTPase KRAS compared with KRAS WT cells. ERH interacts with the spliceosome protein SNRPD3 and is required for the mRNA splicing of the mitotic motor protein CENP-E. Loss of ERH leads to loss of CENP-E and consequently, chromosome congression defects. Gene expression profiling indicates that ERH is required for the expression of multiple cell cycle genes, and the gene expression signature resulting from ERH down-regulation inversely correlates with KRAS signatures. Clinically, tumor ERH expression is inversely associated with survival of colorectal cancer patients whose tumors harbor KRAS mutations. Together, these findings identify a role of ERH in mRNA splicing and mitosis, and they provide evidence that KRAS mutant cancer cells are dependent on ERH for their survival.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/genética , Sequência Conservada , Evolução Molecular , Mutação/genética , Proteínas Proto-Oncogênicas/genética , Splicing de RNA/genética , Fatores de Transcrição/metabolismo , Proteínas ras/genética , Ciclo Celular/genética , Linhagem Celular Tumoral , Sobrevivência Celular/genética , Proteínas Cromossômicas não Histona/metabolismo , Cromossomos Humanos/metabolismo , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Regulação Neoplásica da Expressão Gênica , Humanos , Oncogenes , Ligação Proteica , Proteínas Proto-Oncogênicas p21(ras) , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Análise de Sobrevida , Proteínas Centrais de snRNP/metabolismoRESUMO
The anaphase-promoting complex/cyclosome (APC/C) is a cell cycle-regulated E3 ubiquitin ligase that controls the degradation of substrate proteins at mitotic exit and throughout the G1 phase. We have identified an APC/C substrate and cell cycle-regulated protein, KIAA0101/PAF15. PAF15 protein levels peak in the G2/M phase of the cell cycle and drop rapidly at mitotic exit in an APC/C- and KEN-box-dependent fashion. PAF15 associates with proliferating cell nuclear antigen (PCNA), and depletion of PAF15 decreases the number of cells in S phase, suggesting a role for it in cell cycle regulation. Following irradiation, PAF15 colocalized with γH2AX foci at sites of DNA damage through its interaction with PCNA. Finally, PAF15 depletion led to an increase in homologous recombination-mediated DNA repair, and overexpression caused sensitivity to UV-induced DNA damage. We conclude that PAF15 is an APC/C-regulated protein involved in both cell cycle progression and the DNA damage response.
Assuntos
Proteínas de Transporte/metabolismo , Ciclo Celular , Antígeno Nuclear de Célula em Proliferação/metabolismo , Complexos Ubiquitina-Proteína Ligase/metabolismo , Ciclossomo-Complexo Promotor de Anáfase , Western Blotting , Proteínas de Transporte/genética , Divisão Celular , Linhagem Celular , Linhagem Celular Tumoral , Dano ao DNA , Reparo do DNA , Proteínas de Ligação a DNA , Citometria de Fluxo , Fase G2 , Expressão Gênica , Células HEK293 , Células HeLa , Humanos , Ligação Proteica , Interferência de RNA , Recombinação Genética , Fase S , Especificidade por Substrato , UbiquitinaçãoRESUMO
The ubiquitin-like protein ISG15 (interferon-stimulated gene 15) regulates the host response to bacterial and viral infections through its conjugation to proteins (ISGylation) following interferon production. ISGylation is antagonized by the highly specific cysteine protease USP18, which is the major deISGylating enzyme. However, mechanisms underlying USP18's extraordinary specificity towards ISG15 remains elusive. Here, we show that USP18 interacts with its paralog USP41, whose catalytic domain shares 97% identity with USP18. However, USP41 does not act as a deISGylase, which led us to perform a comparative analysis to decipher the basis for this difference, revealing molecular determinants of USP18's specificity towards ISG15. We found that USP18 C-terminus, as well as a conserved Leucine at position 198, are essential for its enzymatic activity and likely act as functional surfaces based on AlphaFold predictions. Finally, we propose that USP41 antagonizes conjugation of the understudied ubiquitin-like protein FAT10 (HLA-F adjacent transcript 10) from substrates in a catalytic-independent manner. Altogether, our results offer new insights into USP18's specificity towards ISG15, while identifying USP41 as a negative regulator of FAT10 conjugation.
RESUMO
CD28 and 4-1BB costimulatory endodomains included in chimeric antigen receptor (CAR) molecules play a critical role in promoting sustained antitumor activity of CAR-T cells. However, the molecular events associated with the ectopic and constitutive display of either CD28 or 4-1BB in CAR-T cells have been only partially explored. In the current study, we demonstrated that 4-1BB incorporated within the CAR leads to cell cluster formation and cell death in the forms of both apoptosis and necroptosis in the absence of CAR tonic signaling. Mechanistic studies illustrate that 4-1BB sequesters A20 to the cell membrane in a TRAF-dependent manner causing A20 functional deficiency that in turn leads to NF-κB hyperactivity, cell aggregation via ICAM-1 overexpression, and cell death including necroptosis via RIPK1/RIPK3/MLKL pathway. Genetic modulations obtained by either overexpressing A20 or releasing A20 from 4-1BB by deleting the TRAF-binding motifs of 4-1BB rescue cell cluster formation and cell death and enhance the antitumor ability of 4-1BB-costimulated CAR-T cells.
Assuntos
Morte Celular , Receptores de Antígenos Quiméricos , Membro 9 da Superfamília de Receptores de Fatores de Necrose Tumoral , Proteína 3 Induzida por Fator de Necrose Tumoral alfa , Humanos , Receptores de Antígenos Quiméricos/metabolismo , Receptores de Antígenos Quiméricos/genética , Proteína 3 Induzida por Fator de Necrose Tumoral alfa/metabolismo , Proteína 3 Induzida por Fator de Necrose Tumoral alfa/genética , Membro 9 da Superfamília de Receptores de Fatores de Necrose Tumoral/metabolismo , Animais , Necroptose , Apoptose , Transdução de Sinais , Camundongos , NF-kappa B/metabolismo , Linhagem Celular Tumoral , Ubiquitina/metabolismoRESUMO
Ubiquitination is an essential regulator of cell division. The kinase Polo-like kinase 1 (PLK1) promotes protein degradation at G2/M phase through the E3 ubiquitin ligase Skp1-Cul1-F box (SCF)ßTrCP. However, the magnitude to which PLK1 shapes the mitotic proteome is uncharacterized. Combining quantitative proteomics with pharmacologic PLK1 inhibition revealed a widespread, PLK1-dependent program of protein breakdown at G2/M. We validated many PLK1-regulated proteins, including substrates of the cell-cycle E3 SCFCyclin F, demonstrating that PLK1 promotes proteolysis through at least two distinct E3 ligases. We show that the protein-kinase-A-anchoring protein A-kinase anchor protein 2 (AKAP2) is cell-cycle regulated and that its mitotic degradation is dependent on the PLK1/ßTrCP signaling axis. Expression of a non-degradable AKAP2 mutant resulted in actin defects and aberrant mitotic spindles, suggesting that AKAP2 degradation coordinates cytoskeletal organization during mitosis. These findings uncover PLK1's far-reaching role in shaping the mitotic proteome post-translationally and have potential implications in malignancies where PLK1 is upregulated.
RESUMO
Proteasome subunit hRpn13 is partially proteolyzed in certain cancer cell types to generate hRpn13Pru by degradation of its UCHL5/Uch37-binding DEUBAD domain and retention of an intact proteasome- and ubiquitin-binding Pru domain. By using structure-guided virtual screening, we identify an hRpn13 binder (XL44) and solve its structure ligated to hRpn13 Pru by integrated X-ray crystallography and NMR to reveal its targeting mechanism. Surprisingly, hRpn13Pru is depleted in myeloma cells following treatment with XL44. TMT-MS experiments reveal a select group of off-targets, including PCNA clamp-associated factor PCLAF and ribonucleoside-diphosphate reductase subunit M2 (RRM2), that are similarly depleted by XL44 treatment. XL44 induces hRpn13-dependent apoptosis and also restricts cell viability by a PCLAF-dependent mechanism. A KEN box, but not ubiquitination, is required for XL44-induced depletion of PCLAF. Here, we show that XL44 induces ubiquitin-dependent loss of hRpn13Pru and ubiquitin-independent loss of select KEN box containing proteins.
Assuntos
Glicoproteínas de Membrana , Complexo de Endopeptidases do Proteassoma , Complexo de Endopeptidases do Proteassoma/metabolismo , Glicoproteínas de Membrana/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Ubiquitina/metabolismo , Citoplasma/metabolismo , Fatores de TranscriçãoRESUMO
Protein deubiquitinases play critical pathophysiological roles in cancer. Among all deubiquitinases, an oncogenic function for OTUD7B has been established in genetic NSCLC murine models. However, few deubiquitinase inhibitors have been developed due to technical challenges. Here, we report a putative small molecule OTUD7B inhibitor obtained from an AI-aided screen of a 4 million compound library. We validated the effects of the OTUD7B inhibitor (7Bi) in reducing Akt-pS473 signals in multiple NSCLC and HEK293 cells by blocking OTUD7B-governed GßL deubiquitination in cells, as well as inhibiting OTUD7B-mediated cleavage of K11-linked di-ub in an in vitro enzyme assay. Furthermore, we report in leukemia cells, either genetic depletion or 7Bi-mediated pharmacological inhibition of OTUD7B reduces Akt-pS473 via inhibiting the OTUD7B/GßL signaling axis. Together, our study identifies the first putative OTUD7B inhibitor showing activities both in cells and in vitro, with promising applications as a therapeutic agent in treating cancer with OTUD7B overexpression.