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Wang Y, Niu K, Shi Y, Zhou F, Li X, Li Y, Chen T, Zhang Y. A review: targeting UBR5 domains to mediate emerging roles and mechanisms - chance or necessity? Int J Surg 2024; 110:4947-4964. [PMID: 38701508 PMCID: PMC11326040 DOI: 10.1097/js9.0000000000001541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 04/15/2024] [Indexed: 05/05/2024]
Abstract
Ubiquitinases are known to catalyze ubiquitin chains on target proteins to regulate various physiological functions like cell proliferation, autophagy, apoptosis, and cell cycle progression. As a member of E3 ligase, ubiquitin protein ligase E3 component n-recognin 5 (UBR5) belongs to the HECT E3 ligase and has been reported to be correlated with various pathophysiological processes. In this review, the authors give a comprehensive insight into the structure and function of UBR5. The authors discuss the specific domains of UBR5 and explore their biological functions separately. Furthermore, the authors describe the involvement of UBR5 in different pathophysiological conditions, including immune response, virus infection, DNA damage response, and protein quality control. Moreover, the authors provide a thorough summary of the important roles and regulatory mechanisms of UBR5 in cancers and other diseases. On the whole, investigating the domains and functions of UBR5, elucidating the underlying mechanisms of UBR5 with various substrates in detail may provide new theoretical basis for the treatment of diseases, including cancers, which could improve future studies to construct novel UBR5-targeted therapy strategies.
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Affiliation(s)
| | | | | | | | | | | | | | - Yewei Zhang
- Hepatopancreatobiliary Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, People’s Republic of China
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2
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Yang D, Geng T, Harrison AG, Cahoon JG, Xing J, Jiao B, Wang M, Cheng C, Hill RE, Wang H, Vella AT, Cheng G, Wang Y, Wang P. UBR5 promotes antiviral immunity by disengaging the transcriptional brake on RIG-I like receptors. Nat Commun 2024; 15:780. [PMID: 38278841 PMCID: PMC10817939 DOI: 10.1038/s41467-024-45141-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 01/16/2024] [Indexed: 01/28/2024] Open
Abstract
The Retinoic acid-Inducible Gene I (RIG-I) like receptors (RLRs) are the major viral RNA sensors essential for the initiation of antiviral immune responses. RLRs are subjected to stringent transcriptional and posttranslational regulations, of which ubiquitination is one of the most important. However, the role of ubiquitination in RLR transcription is unknown. Here, we screen 375 definite ubiquitin ligase knockout cell lines and identify Ubiquitin Protein Ligase E3 Component N-Recognin 5 (UBR5) as a positive regulator of RLR transcription. UBR5 deficiency reduces antiviral immune responses to RNA viruses, while increases viral replication in primary cells and mice. Ubr5 knockout mice are more susceptible to lethal RNA virus infection than wild type littermates. Mechanistically, UBR5 mediates the Lysine 63-linked ubiquitination of Tripartite Motif Protein 28 (TRIM28), an epigenetic repressor of RLRs. This modification prevents intramolecular SUMOylation of TRIM28, thus disengages the TRIM28-imposed brake on RLR transcription. In sum, UBR5 enables rapid upregulation of RLR expression to boost antiviral immune responses by ubiquitinating and de-SUMOylating TRIM28.
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Affiliation(s)
- Duomeng Yang
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA.
| | - Tingting Geng
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Andrew G Harrison
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Jason G Cahoon
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Jian Xing
- Department of Neuroscience, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Baihai Jiao
- Department of Medicine, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Mark Wang
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Chao Cheng
- Department of Medicine, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Robert E Hill
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine at the University of Edinburgh, Western General Hospital, Edinburgh, EH4, 2XU, UK
| | - Huadong Wang
- Department of Pathophysiology, Key Laboratory of State Administration of Traditional Chinese Medicine of the People's Republic of China, School of Medicine, Jinan University, Guangzhou, 510632, Guangdong, China
| | - Anthony T Vella
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Gong Cheng
- Tsinghua University-Peking University Joint Center for Life Sciences, School of Medicine, Tsinghua University, 100084, Beijing, China
| | - Yanlin Wang
- Department of Medicine, School of Medicine, UConn Health, Farmington, CT, 06030, USA
| | - Penghua Wang
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, 06030, USA.
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3
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Skelin J, Tomaić V. Comparative Analysis of Alpha and Beta HPV E6 Oncoproteins: Insights into Functional Distinctions and Divergent Mechanisms of Pathogenesis. Viruses 2023; 15:2253. [PMID: 38005929 PMCID: PMC10674601 DOI: 10.3390/v15112253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 11/09/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Human papillomaviruses (HPVs) represent a diverse group of DNA viruses that infect epithelial cells of mucosal and cutaneous tissues, leading to a wide spectrum of clinical outcomes. Among various HPVs, alpha (α) and beta (β) types have garnered significant attention due to their associations with human health. α-HPVs are primarily linked to infections of the mucosa, with high-risk subtypes, such as HPV16 and HPV18, being the major etiological agents of cervical and oropharyngeal cancers. In contrast, β-HPVs are predominantly associated with cutaneous infections and are commonly found on healthy skin. However, certain β-types, notably HPV5 and HPV8, have been implicated in the development of non-melanoma skin cancers in immunocompromised individuals, highlighting their potential role in pathogenicity. In this review, we comprehensively analyze the similarities and differences between α- and β-HPV E6 oncoproteins, one of the major drivers of viral replication and cellular transformation, and how these impact viral fitness and the capacity to induce malignancy. In particular, we compare the mechanisms these oncoproteins use to modulate common cellular processes-apoptosis, DNA damage repair, cell differentiation, and the immune response-further shedding light on their shared and distinct features, which enable them to replicate at divergent locations of the human body and cause different types of cancer.
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Affiliation(s)
| | - Vjekoslav Tomaić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia;
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4
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Sap KA, Geijtenbeek KW, Schipper-Krom S, Guler AT, Reits EA. Ubiquitin-modifying enzymes in Huntington's disease. Front Mol Biosci 2023; 10:1107323. [PMID: 36926679 PMCID: PMC10013475 DOI: 10.3389/fmolb.2023.1107323] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/16/2023] [Indexed: 02/10/2023] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the N-terminus of the HTT gene. The CAG repeat expansion translates into a polyglutamine expansion in the mutant HTT (mHTT) protein, resulting in intracellular aggregation and neurotoxicity. Lowering the mHTT protein by reducing synthesis or improving degradation would delay or prevent the onset of HD, and the ubiquitin-proteasome system (UPS) could be an important pathway to clear the mHTT proteins prior to aggregation. The UPS is not impaired in HD, and proteasomes can degrade mHTT entirely when HTT is targeted for degradation. However, the mHTT protein is differently ubiquitinated when compared to wild-type HTT (wtHTT), suggesting that the polyQ expansion affects interaction with (de) ubiquitinating enzymes and subsequent targeting for degradation. The soluble mHTT protein is associated with several ubiquitin-modifying enzymes, and various ubiquitin-modifying enzymes have been identified that are linked to Huntington's disease, either by improving mHTT turnover or affecting overall homeostasis. Here we describe their potential mechanism of action toward improved mHTT targeting towards the proteostasis machinery.
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Affiliation(s)
- Karen A Sap
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Karlijne W Geijtenbeek
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Sabine Schipper-Krom
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Arzu Tugce Guler
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Eric A Reits
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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5
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Wu B, Song M, Dong Q, Xiang G, Li J, Ma X, Wei F. UBR5 promotes tumor immune evasion through enhancing IFN-γ-induced PDL1 transcription in triple negative breast cancer. Am J Cancer Res 2022; 12:5086-5102. [PMID: 35836797 PMCID: PMC9274738 DOI: 10.7150/thno.74989] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/07/2022] [Indexed: 01/12/2023] Open
Abstract
Background: The up-regulation of PD-L1 is recognized as an adaption of cancer cells to evade immune surveillance and attack. However, the intrinsic mechanisms of the induction of PD-L1 by interferon-γ (IFN-γ) in tumor microenvironment remain incompletely characterized. Ubiquitin ligase E3 component N-recognition protein 5 (UBR5) has a critical role in tumorigenesis of triple negative breast cancer (TNBC) by triggering specific immune responses to the tumor. Dual targeting of UBR5 and PD-L1 exhibited superior therapeutic benefits in a preclinical TNBC model in short term. Methods: The regulation of UBR5 to PD-L1 upon IFN-γ stimulation was evaluated through in UBR5 deficiency, reconstitution or overexpression cell line models by quantitative PCR, immunohistochemistry and RNA-seq. The effects of PD-L1 regulation by UBR5 and double blockade of both genes were evaluated in mouse TNBC model. Luciferase reporter assay, chromatin immunoprecipitation-qPCR and bioinformatics analysis were performed to explore the transcription factors involved in the regulation of UBR5 to PD-L1. Results: E3 ubiquitin ligase UBR5 plays a key role in IFN-γ-induced PDL1 transcription in TNBC in an E3 ubiquitination activity-independent manner. RNA-seq-based transcriptomic analyses reveal that UBR5 globally affects the genes in the IFN-γ-induced signaling pathway. Through its poly adenylate binding (PABC) domain, UBR5 enhances the transactivation of PDL1 by upregulating protein kinase RNA-activated (PKR), and PKR's downstream factors including signal transducers and activators of transcription 1 (STAT1) and interferon regulatory factor 1 (IRF1). Restoration of PD-L1 expression in UBR5-deficient tumor cells recoups their malignancy in vivo, whereas CRISPR/Cas9-mediated simultaneous abrogation of UBR5 and PD-L1 expression yields synergistic therapeutic benefits than either blockade alone, with a strong impact on the tumor microenvironment. Conclusions: This study identifies a novel regulator of PDL1 transcription, elucidates the underlying molecular mechanisms and provides a strong rationale for combination cancer immunotherapies targeting UBR5 and PD-L1.
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Affiliation(s)
- Bingbing Wu
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Mei Song
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, New York
| | - Qun Dong
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Gang Xiang
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Jing Li
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaojing Ma
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, New York.,✉ Corresponding author: Fang Wei, 800 Dongchuan Road, Minghang, Shanghai 200240, China. Phone: 86-21-34205287; Fax: 86-21-34205287; E-mail: ; Xiaojing Ma,
| | - Fang Wei
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.,✉ Corresponding author: Fang Wei, 800 Dongchuan Road, Minghang, Shanghai 200240, China. Phone: 86-21-34205287; Fax: 86-21-34205287; E-mail: ; Xiaojing Ma,
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6
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Haręża DA, Wilczyński JR, Paradowska E. Human Papillomaviruses as Infectious Agents in Gynecological Cancers. Oncogenic Properties of Viral Proteins. Int J Mol Sci 2022; 23:1818. [PMID: 35163748 PMCID: PMC8836588 DOI: 10.3390/ijms23031818] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/29/2022] [Accepted: 02/03/2022] [Indexed: 01/25/2023] Open
Abstract
Human papillomaviruses (HPVs), which belong to the Papillomaviridae family, constitute a group of small nonenveloped double-stranded DNA viruses. HPV has a small genome that only encodes a few proteins, and it is also responsible for 5% of all human cancers, including cervical, vaginal, vulvar, penile, anal, and oropharyngeal cancers. HPV types may be classified as high- and low-risk genotypes (HR-HPVs and LR-HPVs, respectively) according to their oncogenic potential. HR-HPV 16 and 18 are the most common types worldwide and are the primary types that are responsible for most HPV-related cancers. The activity of the viral E6 and E7 oncoproteins, which interfere with critical cell cycle points such as suppressive tumor protein p53 (p53) and retinoblastoma protein (pRB), is the major contributor to HPV-induced neoplastic initiation and progression of carcinogenesis. In addition, the E5 protein might also play a significant role in tumorigenesis. The role of HPV in the pathogenesis of gynecological cancers is still not fully understood, which indicates a wide spectrum of potential research areas. This review focuses on HPV biology, the distribution of HPVs in gynecological cancers, the properties of viral oncoproteins, and the molecular mechanisms of carcinogenesis.
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Affiliation(s)
- Daria A. Haręża
- Laboratory of Virology, Institute of Medical Biology of the Polish Academy of Sciences, 93-232 Lodz, Poland;
- BioMedChem Doctoral School of the University of Lodz and Lodz Institutes of the Polish Academy of Sciences, 90-237 Lodz, Poland
| | - Jacek R. Wilczyński
- Department of Surgical and Oncological Gynecology, Medical University of Lodz, 90-419 Lodz, Poland;
| | - Edyta Paradowska
- Laboratory of Virology, Institute of Medical Biology of the Polish Academy of Sciences, 93-232 Lodz, Poland;
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7
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Loss of the E6AP ubiquitin ligase induces p53-dependent phosphorylation of HPV-18 E6 in cells derived from cervical cancer. J Virol 2022; 96:e0150321. [PMID: 35044207 DOI: 10.1128/jvi.01503-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cancer-causing HPV E6 oncoproteins contain a well-characterised phospho-acceptor site within the PDZ (PSD-95/Dlg/ZO-1) binding motif (PBM) at the C-terminus of the protein. Previous studies have shown that the threonine or serine residue in the E6 PBM is subject to phosphorylation by several stress-responsive cellular kinases, upon the induction of DNA damage in cervical cancer-derived cells. However, there is little information about the regulation of E6 phosphorylation in the absence of DNA damage and whether there may be other pathways by which E6 is phosphorylated. In this study, we demonstrate that loss of E6AP results in a dramatic increase in the levels of phosphorylated E6 (pE6), despite the expected overall reduction in total E6 protein levels. Furthermore, phosphorylation of E6 requires transcriptionally active p53 and occurs in a manner which is dependent upon DNA PK. These results identify a novel feedback loop, where loss of E6AP results in upregulation of p53, leading to increased levels of E6 phosphorylation, which in turn correlates with increased association with 14-3-3 and inhibition of p53 transcriptional activity. IMPORTANCE This study demonstrates that the knockdown of E6AP from cervical cancer-derived cells leads to an increase in phosphorylation of the E6 oncoprotein. We show that this phosphorylation of E6 requires p53 transcriptional activity and the enzyme DNA PK. This study therefore defines a feedback loop whereby activation of p53 can induce phosphorylation of E6 and which in turn can inhibit p53 transcriptional activity, independently of E6's ability to target p53 for degradation.
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8
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Human Papillomaviruses-Associated Cancers: An Update of Current Knowledge. Viruses 2021; 13:v13112234. [PMID: 34835040 PMCID: PMC8623401 DOI: 10.3390/v13112234] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 10/26/2021] [Accepted: 10/29/2021] [Indexed: 12/21/2022] Open
Abstract
Human papillomaviruses (HPVs), which are small, double-stranded, circular DNA viruses infecting human epithelial cells, are associated with various benign and malignant lesions of mucosa and skin. Intensive research on the oncogenic potential of HPVs started in the 1970s and spread across Europe, including Croatia, and worldwide. Nowadays, the causative role of a subset of oncogenic or high-risk (HR) HPV types, led by HPV-16 and HPV-18, of different anogenital and head and neck cancers is well accepted. Two major viral oncoproteins, E6 and E7, are directly involved in the development of HPV-related malignancies by targeting synergistically various cellular pathways involved in the regulation of cell cycle control, apoptosis, and cell polarity control networks as well as host immune response. This review is aimed at describing the key elements in HPV-related carcinogenesis and the advances in cancer prevention with reference to past and on-going research in Croatia.
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9
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Vats A, Trejo-Cerro O, Thomas M, Banks L. Human papillomavirus E6 and E7: What remains? Tumour Virus Res 2021; 11:200213. [PMID: 33716206 PMCID: PMC7972986 DOI: 10.1016/j.tvr.2021.200213] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/12/2022] Open
Abstract
Decades of research on the human papillomavirus oncogenes, E6 and E7, have given us huge amounts of data on their expression, functions and structures. We know much about the very many cellular proteins and pathways that they influence in one way or another. However, much of this information is quite discrete, referring to one activity examined under one condition. It is now time to join the dots to try to understand a larger picture: how, where and when do all these interactions occur... and why? Examining these questions will also show how many of the yet obscure cellular processes work together for cellular and tissue homeostasis in health and disease.
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Affiliation(s)
- Arushi Vats
- Tumour Virology Group, ICGEB, AREA Science Park, Trieste, 34149, Italy
| | - Oscar Trejo-Cerro
- Tumour Virology Group, ICGEB, AREA Science Park, Trieste, 34149, Italy
| | - Miranda Thomas
- Tumour Virology Group, ICGEB, AREA Science Park, Trieste, 34149, Italy.
| | - Lawrence Banks
- Tumour Virology Group, ICGEB, AREA Science Park, Trieste, 34149, Italy
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10
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UBR5 HECT domain mutations identified in mantle cell lymphoma control maturation of B cells. Blood 2021; 136:299-312. [PMID: 32325489 DOI: 10.1182/blood.2019002102] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 04/03/2020] [Indexed: 12/16/2022] Open
Abstract
Coordination of a number of molecular mechanisms including transcription, alternative splicing, and class switch recombination are required to facilitate development, activation, and survival of B cells. Disruption of these pathways can result in malignant transformation. Recently, next-generation sequencing has identified a number of novel mutations in mantle cell lymphoma (MCL) patients including mutations in the ubiquitin E3 ligase UBR5. Approximately 18% of MCL patients were found to have mutations in UBR5, with the majority of mutations within the HECT domain of the protein that can accept and transfer ubiquitin molecules to the substrate. Determining if UBR5 controls the maturation of B cells is important to fully understand malignant transformation to MCL. To elucidate the role of UBR5 in B-cell maturation and activation, we generated a conditional mutant disrupting UBR5's C-terminal HECT domain. Loss of the UBR5 HECT domain leads to a block in maturation of B cells in the spleen and upregulation of proteins associated with messenger RNA splicing via the spliceosome. Our studies reveal a novel role of UBR5 in B-cell maturation by stabilization of spliceosome components during B-cell development and suggests UBR5 mutations play a role in MCL transformation.
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11
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Singh S, Ng J, Sivaraman J. Exploring the "Other" subfamily of HECT E3-ligases for therapeutic intervention. Pharmacol Ther 2021; 224:107809. [PMID: 33607149 DOI: 10.1016/j.pharmthera.2021.107809] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/13/2020] [Accepted: 01/26/2021] [Indexed: 12/14/2022]
Abstract
The HECT E3 ligase family regulates key cellular signaling pathways, with its 28 members divided into three subfamilies: NEDD4 subfamily (9 members), HERC subfamily (6 members) and "Other" subfamily (13 members). Here, we focus on the less-explored "Other" subfamily and discuss the recent findings pertaining to their biological roles. The N-terminal regions preceding the conserved HECT domains are significantly diverse in length and sequence composition, and are mostly unstructured, except for short regions that incorporate known substrate-binding domains. In some of the better-characterized "Other" members (e.g., HUWE1, AREL1 and UBE3C), structure analysis shows that the extended region (~ aa 50) adjacent to the HECT domain affects the stability and activity of the protein. The enzymatic activity is also influenced by interactions with different adaptor proteins and inter/intramolecular interactions. Primarily, the "Other" subfamily members assemble atypical ubiquitin linkages, with some cooperating with E3 ligases from the other subfamilies to form branched ubiquitin chains on substrates. Viruses and pathogenic bacteria target and hijack the activities of "Other" subfamily members to evade host immune responses and cause diseases. As such, these HECT E3 ligases have emerged as potential candidates for therapeutic drug development.
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Affiliation(s)
- Sunil Singh
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543, Singapore
| | - Joel Ng
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543, Singapore
| | - J Sivaraman
- Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, 117543, Singapore.
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12
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Adaptors as the regulators of HECT ubiquitin ligases. Cell Death Differ 2021; 28:455-472. [PMID: 33402750 DOI: 10.1038/s41418-020-00707-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/04/2020] [Accepted: 11/04/2020] [Indexed: 12/15/2022] Open
Abstract
The HECT (homologous to E6AP C-terminus) ubiquitin ligases (E3s) are a small family of highly conserved enzymes involved in diverse cellular functions and pathological conditions. Characterised by a C-terminal HECT domain that accepts ubiquitin from E2 ubiquitin conjugating enzymes, these E3s regulate key signalling pathways. The activity and functional regulation of HECT E3s are controlled by several factors including post-translational modifications, inter- and intramolecular interactions and binding of co-activators and adaptor proteins. In this review, we focus on the regulation of HECT E3s by accessory proteins or adaptors and discuss various ways by which adaptors mediate their regulatory roles to affect physiological outcomes. We discuss common features that are conserved from yeast to mammals, regardless of the type of E3s as well as shed light on recent discoveries explaining some existing enigmas in the field.
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13
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Molecular Evolution, Neurodevelopmental Roles and Clinical Significance of HECT-Type UBE3 E3 Ubiquitin Ligases. Cells 2020; 9:cells9112455. [PMID: 33182779 PMCID: PMC7697756 DOI: 10.3390/cells9112455] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/03/2020] [Accepted: 11/07/2020] [Indexed: 12/12/2022] Open
Abstract
Protein ubiquitination belongs to the best characterized pathways of protein degradation in the cell; however, our current knowledge on its physiological consequences is just the tip of an iceberg. The divergence of enzymatic executors of ubiquitination led to some 600–700 E3 ubiquitin ligases embedded in the human genome. Notably, mutations in around 13% of these genes are causative of severe neurological diseases. Despite this, molecular and cellular context of ubiquitination remains poorly characterized, especially in the developing brain. In this review article, we summarize recent findings on brain-expressed HECT-type E3 UBE3 ligases and their murine orthologues, comprising Angelman syndrome UBE3A, Kaufman oculocerebrofacial syndrome UBE3B and autism spectrum disorder-associated UBE3C. We summarize evolutionary emergence of three UBE3 genes, the biochemistry of UBE3 enzymes, their biology and clinical relevance in brain disorders. Particularly, we highlight that uninterrupted action of UBE3 ligases is a sine qua non for cortical circuit assembly and higher cognitive functions of the neocortex.
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14
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Kumar A, Rathi E, Hariharapura RC, Kini SG. Is viral E6 oncoprotein a viable target? A critical analysis in the context of cervical cancer. Med Res Rev 2020; 40:2019-2048. [PMID: 32483862 DOI: 10.1002/med.21697] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 05/18/2020] [Accepted: 05/21/2020] [Indexed: 12/15/2022]
Abstract
An understanding of the pathology of cervical cancer (CC) mediated by E6/E7 oncoproteins of high-risk human papillomavirus (HPV) was developed by late 80's. But if we look at the present scenario, not a single drug could be developed to inhibit these oncoproteins and in turn, be used specifically for the treatment of CC. The readers are advised not to presume the "viability of E6 protein" as mentioned in the title relates to just druggability of E6. The viability aspect will cover almost everything a researcher should know to develop E6 inhibitors until the preclinical stage. Herein, we have analysed the achievements and shortcomings of the scientific community in the last four decades in targeting HPV E6 against CC. Role of all HPV proteins has been briefly described for better perspective with a little detailed discussion of the role of E6. We have reviewed the articles from 1985 onward, reporting in vitro inhibition of E6. Recently, many computational studies have reported potent E6 inhibitors and these have also been reviewed. Subsequently, a critical analysis has been reported to cover the in vitro assay protocols and in vivo models to develop E6 inhibitors. A paragraph has been devoted to the role of public policy to fight CC employing vaccines and whether the vaccine against HPV has quenched the zeal to develop drugs against it. The review concludes with the challenges and the way forward.
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Affiliation(s)
- Avinash Kumar
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Ekta Rathi
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Raghu Chandrashekar Hariharapura
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Suvarna G Kini
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
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Đukić A, Lulić L, Thomas M, Skelin J, Bennett Saidu NE, Grce M, Banks L, Tomaić V. HPV Oncoproteins and the Ubiquitin Proteasome System: A Signature of Malignancy? Pathogens 2020; 9:pathogens9020133. [PMID: 32085533 PMCID: PMC7168213 DOI: 10.3390/pathogens9020133] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/10/2020] [Accepted: 02/11/2020] [Indexed: 12/22/2022] Open
Abstract
Human papillomavirus (HPV) E6 and E7 oncoproteins are critical for development and maintenance of the malignant phenotype in HPV-induced cancers. These two viral oncoproteins interfere with a plethora of cellular pathways, including the regulation of cell cycle and the control of apoptosis, which are critical in maintaining normal cellular functions. E6 and E7 bind directly with certain components of the Ubiquitin Proteasome System (UPS), enabling them to manipulate a number of important cellular pathways. These activities are the means by which HPV establishes an environment supporting the normal viral life cycle, however in some instances they can also lead to the development of malignancy. In this review, we have discussed how E6 and E7 oncoproteins from alpha and beta HPV types interact with the components of the UPS, and how this interplay contributes to the development of cancer.
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Affiliation(s)
- Anamaria Đukić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
| | - Lucija Lulić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
| | - Miranda Thomas
- International Centre for Genetic Engineering and Biotechnology, AREA Science Park, Padriciano 99, I-34149 Trieste, Italy; (M.T.); (L.B.)
| | - Josipa Skelin
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
| | - Nathaniel Edward Bennett Saidu
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
| | - Magdalena Grce
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
| | - Lawrence Banks
- International Centre for Genetic Engineering and Biotechnology, AREA Science Park, Padriciano 99, I-34149 Trieste, Italy; (M.T.); (L.B.)
| | - Vjekoslav Tomaić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; (A.Đ.); (L.L.); (J.S.); (N.E.B.S.); (M.G.)
- Correspondence: ; Tel.: +385-1-4561110; Fax: +385-1-4561010
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16
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PDZ Domain-Containing Protein NHERF-2 Is a Novel Target of Human Papillomavirus 16 (HPV-16) and HPV-18. J Virol 2019; 94:JVI.00663-19. [PMID: 31597772 DOI: 10.1128/jvi.00663-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 09/11/2019] [Indexed: 01/02/2023] Open
Abstract
Cancer-causing human papillomavirus (HPV) E6 oncoproteins have a class I PDZ-binding motif (PBM) on their C termini, which play critical roles that are related to the HPV life cycle and HPV-induced malignancies. E6 oncoproteins use these PBMs to interact with, to target for proteasome-mediated degradation, a plethora of cellular substrates that contain PDZ domains and that are involved in the regulation of various cellular pathways. In this study, we show that both HPV-16 and HPV-18 E6 oncoproteins can interact with Na+/H+ exchange regulatory factor 2 (NHERF-2), a PDZ domain-containing protein, which among other cellular functions also behaves as a tumor suppressor regulating endothelial proliferation. The interaction between the E6 oncoproteins and NHERF-2 is PBM dependent and results in proteasome-mediated degradation of NHERF-2. We further confirmed this effect in cells derived from HPV-16- and HPV-18-positive cervical tumors, where we show that NHERF-2 protein turnover is increased in the presence of E6. Finally, our data indicate that E6-mediated NHERF-2 degradation results in p27 downregulation and cyclin D1 upregulation, leading to accelerated cellular proliferation. To our knowledge, this is the first report to demonstrate that E6 oncoproteins can stimulate cell proliferation by indirectly regulating p27 through targeting a PDZ domain-containing protein.IMPORTANCE This study links HPV-16 and HPV-18 E6 oncoproteins to the modulation of cellular proliferation. The PDZ domain-containing protein NHERF-2 is a tumor suppressor that has been shown to regulate endothelial proliferation; here, we demonstrate that NHERF-2 is targeted by HPV E6 for proteasome-mediated degradation. Interestingly, this indirectly affects p27, cyclin D1, and CDK4 protein levels and, consequently, affects cell proliferation. Hence, this study provides information that will improve our understanding of the molecular basis for HPV E6 function, and it also highlights the importance of the PDZ domain-containing protein NHERF-2 and its tumor-suppressive role in regulating cell proliferation.
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17
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Pyeon D, Rojas VK, Price L, Kim S, Singh M, Park IW. HIV-1 Impairment via UBE3A and HIV-1 Nef Interactions Utilizing the Ubiquitin Proteasome System. Viruses 2019; 11:v11121098. [PMID: 31783587 PMCID: PMC6950590 DOI: 10.3390/v11121098] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 11/15/2019] [Accepted: 11/25/2019] [Indexed: 12/30/2022] Open
Abstract
Molecular basis of HIV-1 life cycle regulation has thus far focused on viral gene stage-specificity, despite the quintessence of post-function protein elimination processes in the virus life cycle and consequent pathogenesis. Our studies demonstrated that a key pathogenic HIV-1 viral protein, Nef, interacted with ubiquitin (Ub)-protein ligase E3A (UBE3A/E6AP), suggesting that interaction between Nef and UBE3A is integral to regulation of viral and cellular protein decay and thereby the competing HIV-1 and host cell survivals. In fact, Nef and UBE3A degraded reciprocally, and UBE3A-mediated degradation of Nef was significantly more potent than Nef-triggered degradation of UBE3A. Further, UBE3A degraded not only Nef but also HIV-1 structural proteins, Gag, thus significantly inhibiting HIV-1 replication in Jurkat T cells only in the presence of Nef, indicating that interaction between Nef and UBE3Awas pivotal for UBE3A-mediated degradation of the viral proteins. Mechanistic study showed that Nef and UBE3A were specific and antagonistic to each other in regulating proteasome activity and ubiquitination of cellular proteins in general, wherein specific domains of Nef overlapping with the long terminal repeat (LTR) were essential for the observed actions. Further, Nef itself reduced the level of intracellular Gag by degrading a cardinal transcription regulator, Tat, demonstrating a broad role for Nef in the regulation of the HIV-1 life cycle. Taken together, these data demonstrated that the Nef and UBE3A complex plays a crucial role in coordinating viral protein degradation and hence HIV-1 replication, providing insights as to the nature of pathobiologic and defense strategies of HIV-1 and HIV-infected host cells.
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Affiliation(s)
- Dohun Pyeon
- Departments of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA;
| | - Vivian K. Rojas
- Department of Microbiology, Immunology and Genetics, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (V.K.R.); (L.P.)
| | - Lenore Price
- Department of Microbiology, Immunology and Genetics, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (V.K.R.); (L.P.)
| | - Seongcheol Kim
- Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA (M.S.)
| | - Meharvan Singh
- Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA (M.S.)
| | - In-Woo Park
- Department of Microbiology, Immunology and Genetics, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (V.K.R.); (L.P.)
- Correspondence: ; Tel.: +(817)-735-5115; Fax: +(817)-735-2610
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18
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Saez I, Gerbracht JV, Koyuncu S, Lee HJ, Horn M, Kroef V, Denzel MS, Dieterich C, Gehring NH, Vilchez D. The E3 ubiquitin ligase UBR5 interacts with the H/ACA ribonucleoprotein complex and regulates ribosomal RNA biogenesis in embryonic stem cells. FEBS Lett 2019; 594:175-188. [PMID: 31365120 DOI: 10.1002/1873-3468.13559] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/24/2019] [Accepted: 07/26/2019] [Indexed: 12/27/2022]
Abstract
UBR5 is an E3 ubiquitin ligase involved in distinct processes such as transcriptional regulation and development. UBR5 is highly upregulated in embryonic stem cells (ESCs), whereas its expression decreases with differentiation, suggesting a role for UBR5 in ESC function. However, little is known about how UBR5 regulates ESC identity. Here, we define the protein interactome of UBR5 in ESCs and find interactions with distinct components of the H/ACA ribonucleoprotein complex, which is required for proper maturation of ribosomal RNA (rRNA). Notably, loss of UBR5 induces an abnormal accumulation of rRNA processing intermediates, resulting in diminished ribosomal levels. Consequently, lack of UBR5 triggers an increase in p53 levels and a concomitant decrease in cellular proliferation rates. Thus, our results indicate a link between UBR5 and rRNA maturation.
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Affiliation(s)
- Isabel Saez
- Institute for Genetics and Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
| | | | - Seda Koyuncu
- Institute for Genetics and Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
| | - Hyun Ju Lee
- Institute for Genetics and Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
| | - Moritz Horn
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Virginia Kroef
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Martin S Denzel
- Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Christoph Dieterich
- Section of Bioinformatics and Systems Cardiology, Department of Internal Medicine III and Klaus, Tschira Institute for Computational Cardiology, University Hospital, Heidelberg, Germany
| | - Niels H Gehring
- Institute for Genetics, Department of Biology, University of Cologne, Germany
| | - David Vilchez
- Institute for Genetics and Cologne Excellence Cluster for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
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19
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Choi J, Busino L. E3 ubiquitin ligases in B-cell malignancies. Cell Immunol 2019; 340:103905. [PMID: 30827673 PMCID: PMC6584052 DOI: 10.1016/j.cellimm.2019.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 12/05/2018] [Accepted: 02/19/2019] [Indexed: 12/21/2022]
Abstract
Ubiquitylation is a post-translational modification (PTM) that controls various cellular signaling pathways. It is orchestrated by a three-step enzymatic cascade know as the ubiquitin proteasome system (UPS). E3 ligases dictate the specificity to the substrates, primarily leading to proteasome-dependent degradation. Deregulation of the UPS components by various mechanisms contributes to the pathogenesis of cancer. This review focuses on E3 ligase-substrates pairings that are implicated in B-cell malignancies. Understanding the molecular mechanism of specific E3 ubiquitin ligases will present potential opportunities for the development of targeted therapeutic approaches.
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Affiliation(s)
- Jaewoo Choi
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Luca Busino
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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20
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Gupta SM, Mania-Pramanik J. Molecular mechanisms in progression of HPV-associated cervical carcinogenesis. J Biomed Sci 2019; 26:28. [PMID: 31014351 PMCID: PMC6477741 DOI: 10.1186/s12929-019-0520-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 04/11/2019] [Indexed: 12/13/2022] Open
Abstract
Cervical cancer is the fourth most frequent cancer in women worldwide and a major cause of mortality in developing countries. Persistent infection with high-risk human papillomavirus (HPV) is a necessary cause for the development of cervical cancer. In addition, genetic and epigenetic alterations in host cell genes are crucial for progression of cervical precancerous lesions to invasive cancer. Although much progress has been made in understanding the life cycle of HPV and it’s role in the development of cervical cancer, there is still a critical need for accurate surveillance strategies and targeted therapeutic options to eradicate these cancers in patients. Given the widespread nature of HPV infection and the type specificity of currently available HPV vaccines, it is crucial that molecular details of the natural history of HPV infection as well as the biological activities of viral oncoproteins be elucidated. A better understanding of the mechanisms involved in oncogenesis can provide novel insights and opportunities for designing effective therapeutic approaches against HPV-associated malignancies. In this review, we briefly summarize epigenetic alterations and events that cause alterations in host genomes inducing cell cycle deregulation, aberrant proliferation and genomic instability contributing to tumorigenesis.
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Affiliation(s)
- Sadhana M Gupta
- Department of Infectious Diseases Biology, National Institute for Research in Reproductive Health, J.M. Street, Parel, Mumbai, 400012, India.
| | - Jayanti Mania-Pramanik
- Department of Infectious Diseases Biology, National Institute for Research in Reproductive Health, J.M. Street, Parel, Mumbai, 400012, India
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21
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Song L, Luo ZQ. Post-translational regulation of ubiquitin signaling. J Cell Biol 2019; 218:1776-1786. [PMID: 31000580 PMCID: PMC6548142 DOI: 10.1083/jcb.201902074] [Citation(s) in RCA: 184] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/29/2019] [Accepted: 04/03/2019] [Indexed: 12/22/2022] Open
Abstract
Song and Luo review the roles of post-translational modifications in ubiquitin signaling. Ubiquitination regulates many essential cellular processes in eukaryotes. This post-translational modification (PTM) is typically achieved by E1, E2, and E3 enzymes that sequentially catalyze activation, conjugation, and ligation reactions, respectively, leading to covalent attachment of ubiquitin, usually to lysine residues of substrate proteins. Ubiquitin can also be successively linked to one of the seven lysine residues on ubiquitin to form distinctive forms of polyubiquitin chains, which, depending upon the lysine used and the length of the chains, dictate the fate of substrate proteins. Recent discoveries revealed that this ubiquitin code is further expanded by PTMs such as phosphorylation, acetylation, deamidation, and ADP-ribosylation, on ubiquitin, components of the ubiquitination machinery, or both. These PTMs provide additional regulatory nodes to integrate development or insulting signals with cellular homeostasis. Understanding the precise roles of these PTMs in the regulation of ubiquitin signaling will provide new insights into the mechanisms and treatment of various human diseases linked to ubiquitination, including neurodegenerative diseases, cancer, infection, and immune disorders.
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Affiliation(s)
- Lei Song
- Department of Respiratory Medicine and Center of Infection and Immunity, The First Hospital of Jilin University, Changchun, China
| | - Zhao-Qing Luo
- Department of Respiratory Medicine and Center of Infection and Immunity, The First Hospital of Jilin University, Changchun, China .,Purdue Institute for Inflammation, Immunology and Infectious Diseases and Department of Biological Sciences, Purdue University, West Lafayette, IN
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22
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Lai TO, Boon SS, Law PT, Chen Z, Thomas M, Banks L, Chan PK. Oncogenicitiy Comparison of Human Papillomavirus Type 52 E6 Variants. J Gen Virol 2019; 100:484-496. [PMID: 30676312 DOI: 10.1099/jgv.0.001222] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Human papillomavirus (HPV) infection contributes to virtually all cases of cervical cancer, the fourth most common cancer affecting women worldwide. The oncogenicity of HPV is mainly attributable to the E6 and E7 oncoproteins. HPV-52 is the seventh most common HPV type globally, but it has a remarkably high prevalence in East Asia. In previous studies it has been speculated that the oncogenicity might vary among different HPV-52 variants. In the present study, we compared the oncogenicity of E6 derived from the HPV-52 prototype and three commonly found variants, V1 (K93R), V2 (E14D/V92L) and V3 (K93R/N122K), through molecular and phenotypic approaches. We demonstrated that cells containing V1 achieved higher colony formation and showed greater cell migration ability when compared to other variants, but no difference in cell immortalization ability was observed. At the molecular level, the three variants formed complexes with E6-associated protein (E6AP) and p53 as efficiently as the prototype. They degraded p53 and PSD95/Dlg/ZO-1(PDZ) proteins, including MAGI-1c and Dlg, to a similar extent. They also exhibited a similar subcellular localization, and shared a half-life of approximately 45 min. Our findings provide a clearer picture of HPV-52 E6 variant oncogenicity, which is important for further studies aiming to understand the unusually high prevalence of HPV-52 among cervical cancers in East Asia.
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Affiliation(s)
- Tsz On Lai
- 1Department of Microbiology, Faulty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
| | - Siaw Shi Boon
- 1Department of Microbiology, Faulty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
| | - Priscilla Ty Law
- 1Department of Microbiology, Faulty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
| | - Zigui Chen
- 1Department of Microbiology, Faulty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
| | - Miranda Thomas
- 2International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Lawrence Banks
- 2International Centre for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Paul Ks Chan
- 1Department of Microbiology, Faulty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
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23
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Lopez SJ, Segal DJ, LaSalle JM. UBE3A: An E3 Ubiquitin Ligase With Genome-Wide Impact in Neurodevelopmental Disease. Front Mol Neurosci 2019; 11:476. [PMID: 30686997 PMCID: PMC6338038 DOI: 10.3389/fnmol.2018.00476] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/05/2018] [Indexed: 12/11/2022] Open
Abstract
UBE3A is an E3 ubiquitin ligase encoded by an imprinted gene whose maternal deletion or duplication leads to distinct neurodevelopment disorders Angelman and Dup15q syndromes. Despite the known genetic basis of disease, how changes in copy number of a ubiquitin ligase gene can have widespread impact in early brain development is poorly understood. Previous studies have identified a wide array of UBE3A functions, interaction partners, and ubiquitin targets, but no central pathway fully explains its critical role in neurodevelopment. Here, we review recent UBE3A studies that have begun to investigate mechanistic, cellular pathways and the genome-wide impacts of alterations in UBE3A expression levels to gain broader insight into how UBE3A affects the developing brain. These studies have revealed that UBE3A is a multifunctional protein with important nuclear and cytoplasmic regulatory functions that impact proteasome function, Wnt signaling, circadian rhythms, imprinted gene networks, and chromatin. Synaptic functions of UBE3A interact with light exposures and mTOR signaling and are most critical in GABAergic neurons. Understanding the genome-wide influences of UBE3A will help uncover its role in early brain development and ultimately lead to identification of key therapeutic targets for UBE3A-related neurodevelopmental disorders.
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Affiliation(s)
- Simon Jesse Lopez
- Department of Medical Immunology and Microbiology, University of California, Davis, Davis, CA, United States.,Genome Center, University of California, Davis, Davis, CA, United States.,MIND Institute, University of California, Davis, Davis, CA, United States.,Integrative Genetics and Genomics, University of California, Davis, Davis, CA, United States
| | - David J Segal
- Genome Center, University of California, Davis, Davis, CA, United States.,MIND Institute, University of California, Davis, Davis, CA, United States.,Integrative Genetics and Genomics, University of California, Davis, Davis, CA, United States.,Department of Biochemistry and Molecular Medicine, University of California, Davis, Davis, CA, United States
| | - Janine M LaSalle
- Department of Medical Immunology and Microbiology, University of California, Davis, Davis, CA, United States.,Genome Center, University of California, Davis, Davis, CA, United States.,MIND Institute, University of California, Davis, Davis, CA, United States.,Integrative Genetics and Genomics, University of California, Davis, Davis, CA, United States
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24
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Sluimer J, Distel B. Regulating the human HECT E3 ligases. Cell Mol Life Sci 2018; 75:3121-3141. [PMID: 29858610 PMCID: PMC6063350 DOI: 10.1007/s00018-018-2848-2] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 05/23/2018] [Accepted: 05/28/2018] [Indexed: 01/09/2023]
Abstract
Ubiquitination, the covalent attachment of ubiquitin to proteins, by E3 ligases of the HECT (homologous to E6AP C terminus) family is critical in controlling diverse physiological pathways. Stringent control of HECT E3 ligase activity and substrate specificity is essential for cellular health, whereas deregulation of HECT E3s plays a prominent role in disease. The cell employs a wide variety of regulatory mechanisms to control HECT E3 activity and substrate specificity. Here, we summarize the current understanding of these regulatory mechanisms that control HECT E3 function. Substrate specificity is generally determined by interactions of adaptor proteins with domains in the N-terminal extensions of HECT E3 ligases. These N-terminal domains have also been found to interact with the HECT domain, resulting in the formation of inhibitory conformations. In addition, catalytic activity of the HECT domain is commonly regulated at the level of E2 recruitment and through HECT E3 oligomerization. The previously mentioned regulatory mechanisms can be controlled through protein-protein interactions, post-translational modifications, the binding of calcium ions, and more. Functional activity is determined not only by substrate recruitment and catalytic activity, but also by the type of ubiquitin polymers catalyzed to the substrate. While this is often determined by the specific HECT member, recent studies demonstrate that HECT E3s can be modulated to alter the type of ubiquitin polymers they catalyze. Insight into these diverse regulatory mechanisms that control HECT E3 activity may open up new avenues for therapeutic strategies aimed at inhibition or enhancement of HECT E3 function in disease-related pathways.
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Affiliation(s)
- Jasper Sluimer
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Ben Distel
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
- Department of Neuroscience, Erasmus Medical Center, Wijtemaweg 80, 3015 CN, Rotterdam, The Netherlands.
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25
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Chung CG, Lee H, Lee SB. Mechanisms of protein toxicity in neurodegenerative diseases. Cell Mol Life Sci 2018; 75:3159-3180. [PMID: 29947927 PMCID: PMC6063327 DOI: 10.1007/s00018-018-2854-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 06/06/2018] [Accepted: 06/07/2018] [Indexed: 12/12/2022]
Abstract
Protein toxicity can be defined as all the pathological changes that ensue from accumulation, mis-localization, and/or multimerization of disease-specific proteins. Most neurodegenerative diseases manifest protein toxicity as one of their key pathogenic mechanisms, the details of which remain unclear. By systematically deconstructing the nature of toxic proteins, we aim to elucidate and illuminate some of the key mechanisms of protein toxicity from which therapeutic insights may be drawn. In this review, we focus specifically on protein toxicity from the point of view of various cellular compartments such as the nucleus and the mitochondria. We also discuss the cell-to-cell propagation of toxic disease proteins that complicates the mechanistic understanding of the disease progression as well as the spatiotemporal point at which to therapeutically intervene. Finally, we discuss selective neuronal vulnerability, which still remains largely enigmatic.
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Affiliation(s)
- Chang Geon Chung
- Department of Brain and Cognitive Sciences, DGIST, Daegu, 42988, Republic of Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu, 42988, Republic of Korea.
| | - Sung Bae Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu, 42988, Republic of Korea.
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26
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Kiessling SY, Broglie MA, Soltermann A, Huber GF, Stoeckli SJ. Comparison of PI3K Pathway in HPV-Associated Oropharyngeal Cancer With and Without Tobacco Exposure. Laryngoscope Investig Otolaryngol 2018; 3:283-289. [PMID: 30186959 PMCID: PMC6119789 DOI: 10.1002/lio2.175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/23/2018] [Accepted: 04/30/2018] [Indexed: 12/21/2022] Open
Abstract
Objectives The aim of the study was to evaluate whether HPV associated OPSCC with tobacco exposure follows a different carcinogenic pathway compared to HPV associated OPSCC without tobacco exposure and to investigate its prognostic significance. The question was addressed with focus on components of the PI3K pathway. Methods 184 patients with newly diagnosed OPSCC treated with curative intent were consecutively enrolled. The expression level of p16, p53, PI3K, mTOR, and PTEN was assessed by immunohistochemistry and analyzed in relation to the risk factors HPV status and tobacco exposure. Results 94 of 184 (51%) patients were p16 positive, p53 overexpression was detected in 48 of 184 (26%) cases. PI3K overexpression with 70 of 184 (38%) cases was significantly higher in p16 positive tumors. mTOR overexpression was present in 90 of 184 (49%) cases and significantly higher in p16 negative tumors. PTEN loss was found in 42 of 184 (23%) cases without association to p16 expression. p16 positive OPSCC showed lower rates of p53 expression and mTOR expression as well as higher rates of PI3K expression irrespective of tobacco exposure. Survival analysis showed a distinct intermediate survival rate of p16 positive smokers. The markers PI3K, mTOR, and PTEN did not have a significant impact on survival. Conclusion HPV associated OPSCC with tobacco exposure follows the same expression level of the PI3K pathway as HPV associated OPSCC without tobacco exposure. The impaired survival rate of the intermediate risk group cannot be explained by different expression patterns of PI3K, mTOR, and PTEN. Level of Evidence 2b
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Affiliation(s)
- Si-Young Kiessling
- Department of Otorhinolaryngology, Head and Neck Surgery Cantonal Hospital of St. Gallen St. Gallen Switzerland
| | - Martina Anja Broglie
- Department of Otorhinolaryngology, Head and Neck Surgery Cantonal Hospital of St. Gallen St. Gallen Switzerland
| | - Alex Soltermann
- Institute of Pathology and Molecular Pathology University Hospital of Zurich Zurich Switzerland
| | - Gerhard Frank Huber
- Department of Otorhinolaryngology, Head and Neck Surgery University Hospital of Zurich Zurich Switzerland.,University of Zurich Zurich Switzerland
| | - Sandro Johannes Stoeckli
- Department of Otorhinolaryngology, Head and Neck Surgery Cantonal Hospital of St. Gallen St. Gallen Switzerland
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27
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The Human Papillomavirus E6 PDZ Binding Motif Links DNA Damage Response Signaling to E6 Inhibition of p53 Transcriptional Activity. J Virol 2018; 92:JVI.00465-18. [PMID: 29848585 DOI: 10.1128/jvi.00465-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/21/2018] [Indexed: 02/07/2023] Open
Abstract
The presence of a PDZ binding motif (PBM) in the human papillomavirus (HPV) E6 oncoprotein appears to be a characteristic marker of high oncogenic potential and confers interaction with a number of different cellular PDZ domain-containing substrates. The E6 PBM is also subject to phosphorylation, resulting in inhibition of E6 PDZ binding activity and instead allowing E6 to associate with 14-3-3 proteins. In this study, we analyzed the conditions under which the E6 PBM is phosphorylated. We demonstrate that in normal cycling cells, the levels of E6 phosphorylation are very low. However, following exposure of cells to oxidative stress or the induction of DNA damage, there is a striking increase in the levels of E6 phosphorylation. Depending on the specific stimulus, this phosphorylation of E6 can involve the ATM/ATR pathway and is performed primarily through Chk1, although the Chk2 pathway is also involved indirectly through activation of protein kinase A (PKA). To understand the biological relevance of these phospho-modifications of E6, we analyzed their effects upon the ability of E6 to inhibit p53 transcriptional activity. We show that an intact E6 phospho-acceptor site plays an essential role in the ability of E6 to inhibit p53 transcriptional activity on a subset of p53-responsive promoters in a manner that is independent of E6's ability to direct p53 degradation. These results are, to our knowledge, the first example of a DNA damage response controlling PBM-PDZ recognition. This study also provides links between the DNA damage response, the regulation of E6 PBM function, and the inhibition of p53 activity and begins to explain how HPV-infected cells remain within the cell cycle, despite activation of DNA damage response pathways during productive virus infections.IMPORTANCE The cancer-causing HPV E6 oncoproteins all possess a PDZ binding motif at their extreme carboxy termini. Depending upon whether this motif is phosphorylated, E6 can recognize PDZ domain-containing proteins or members of the 14-3-3 family of proteins. We show here that DNA damage response pathways directly signal to the E6 PBM, resulting in Chk1- and Chk2-driven phosphorylation. This phosphorylation is particularly pronounced following treatment of cells with a variety of different chemotherapeutic drugs. A direct functional consequence of this signaling is to confer an enhanced ability upon E6 to inhibit p53 transcriptional activity in a proteasome-independent but phosphorylation-dependent manner. These results are the first example of DNA damage signaling pathways regulating PBM-PDZ interactions and provide the mechanistic link between E6 PBM function and perturbation of p53 activity.
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Harding RJ, Tong YF. Proteostasis in Huntington's disease: disease mechanisms and therapeutic opportunities. Acta Pharmacol Sin 2018; 39:754-769. [PMID: 29620053 DOI: 10.1038/aps.2018.11] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 02/18/2018] [Indexed: 02/08/2023] Open
Abstract
Many neurodegenerative diseases are characterized by impairment of protein quality control mechanisms in neuronal cells. Ineffective clearance of misfolded proteins by the proteasome, autophagy pathways and exocytosis leads to accumulation of toxic protein oligomers and aggregates in neurons. Toxic protein species affect various cellular functions resulting in the development of a spectrum of different neurodegenerative proteinopathies, including Huntington's disease (HD). Playing an integral role in proteostasis, dysfunction of the ubiquitylation system in HD is progressive and multi-faceted with numerous biochemical pathways affected, in particular, the ubiquitin-proteasome system and autophagy routes for protein aggregate degradation. Unravelling the molecular mechanisms involved in HD pathogenesis of proteostasis provides new insight in disease progression in HD as well as possible therapeutic avenues. Recent developments of potential therapeutics are discussed in this review.
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Human Papillomavirus 16 (HPV-16), HPV-18, and HPV-31 E6 Override the Normal Phosphoregulation of E6AP Enzymatic Activity. J Virol 2017; 91:JVI.01390-17. [PMID: 28835500 DOI: 10.1128/jvi.01390-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 08/16/2017] [Indexed: 11/20/2022] Open
Abstract
The human papillomavirus (HPV) E6 oncoproteins recruit the cellular ubiquitin ligase E6AP/UBE3A to target cellular substrates for proteasome-mediated degradation, and one consequence of this activity is the E6 stimulation of E6AP autoubiquitination and degradation. Recent studies identified an autism-linked mutation within E6AP at T485, which was identified as a protein kinase A phosphoacceptor site and which could directly regulate E6AP ubiquitin ligase activity. In this study, we have analyzed how T485-mediated regulation of E6AP might affect E6 targeting of some of its known substrates. We show that modulation of T485 has no effect on the ability of E6 to direct either p53 or Dlg for degradation. Furthermore, T485 regulation has no effect on HPV-16 or HPV-31 E6-induced autodegradation of E6AP but does affect HPV-18 E6-induced autodegradation of E6AP. In cells derived from cervical cancers, we find low levels of both phosphorylated and nonphosphorylated E6AP in the nucleus. However, ablation of E6 results in a dramatic accumulation of phospho-E6AP in the cytoplasm, whereas nonphosphorylated E6AP accumulates primarily in the nucleus. Interestingly, E6AP phosphorylation at T485 confers association with 14-3-3 proteins, and this interaction seems to be important, in part, for the ability of E6 to recruit phospho-E6AP into the nucleus. These results demonstrate that HPV E6 overrides the normal phosphoregulation of E6AP, both in terms of its enzymatic activity and its subcellular distribution.IMPORTANCE Recent reports demonstrate the importance of phosphoregulation of E6AP for its normal enzymatic activity. Here, we show that HPV E6 is capable of overriding this regulation and can promote degradation of p53 and Dlg regardless of the phosphorylation status of E6AP. Furthermore, E6 interaction with E6AP also significantly alters how E6AP is subject to autodegradation and suggests that this is not a simple stimulation of an already-existing activity but rather a redirection of E6AP activity toward itself. Furthermore, E6-mediated regulation of the subcellular distribution of phospho-E6AP appears to be dependent, in part, upon the 14-3-3 family of proteins.
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Sominsky S, Shterzer N, Jackman A, Shapiro B, Yaniv A, Sherman L. E6 proteins of α and β cutaneous HPV types differ in their ability to potentiate Wnt signaling. Virology 2017; 509:11-22. [DOI: 10.1016/j.virol.2017.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/23/2017] [Accepted: 05/30/2017] [Indexed: 01/29/2023]
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Kuslansky Y, Sominsky S, Jackman A, Gamell C, Monahan BJ, Haupt Y, Rosin-Arbesfeld R, Sherman L. Ubiquitin ligase E6AP mediates nonproteolytic polyubiquitylation of β-catenin independent of the E6 oncoprotein. J Gen Virol 2016; 97:3313-3330. [DOI: 10.1099/jgv.0.000624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Yael Kuslansky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Sophia Sominsky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Anna Jackman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Cristina Gamell
- Research Division, The Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Brendon J. Monahan
- Division of Systems Biology and Personalized Medicine, Walter and Eliza Hall Institute of Medical Research, Parkville 3052, Victoria, Australia
| | - Ygal Haupt
- Research Division, The Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville 3010, Victoria, Australia
| | - Rina Rosin-Arbesfeld
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Levana Sherman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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Tomaić V. Functional Roles of E6 and E7 Oncoproteins in HPV-Induced Malignancies at Diverse Anatomical Sites. Cancers (Basel) 2016; 8:cancers8100095. [PMID: 27775564 PMCID: PMC5082385 DOI: 10.3390/cancers8100095] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 09/15/2016] [Accepted: 10/08/2016] [Indexed: 01/13/2023] Open
Abstract
Approximately 200 human papillomaviruses (HPVs) infect human epithelial cells, of which the alpha and beta types have been the most extensively studied. Alpha HPV types mainly infect mucosal epithelia and a small group of these causes over 600,000 cancers per year worldwide at various anatomical sites, especially anogenital and head-and-neck cancers. Of these the most important is cervical cancer, which is the leading cause of cancer-related death in women in many parts of the world. Beta HPV types infect cutaneous epithelia and may contribute towards the initiation of non-melanoma skin cancers. HPVs encode two oncoproteins, E6 and E7, which are directly responsible for the development of HPV-induced carcinogenesis. They do this cooperatively by targeting diverse cellular pathways involved in the regulation of cell cycle control, of apoptosis and of cell polarity control networks. In this review, the biological consequences of papillomavirus targeting of various cellular substrates at diverse anatomical sites in the development of HPV-induced malignancies are highlighted.
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Affiliation(s)
- Vjekoslav Tomaić
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34149 Trieste, Italy.
- Division of Molecular Medicine, Rudjer Boskovic Institute, 10000 Zagreb, Croatia.
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Shearer RF, Iconomou M, Watts CKW, Saunders DN. Functional Roles of the E3 Ubiquitin Ligase UBR5 in Cancer. Mol Cancer Res 2015; 13:1523-32. [PMID: 26464214 DOI: 10.1158/1541-7786.mcr-15-0383] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/06/2015] [Indexed: 11/16/2022]
Abstract
The Ubiquitin-Proteasome System (UPS) is an important regulator of cell signaling and proteostasis, which are essential to a variety of cellular processes. The UPS is disrupted in many diseases including cancer, and targeting the UPS for cancer therapy is gaining wide interest. E3 ubiquitin ligases occupy a key position in the hierarchical UPS enzymatic cascade, largely responsible for determining substrate specificity and ubiquitin (Ub) chain topology. The E3 ligase UBR5 (aka EDD1) is emerging as a key regulator of the UPS in cancer and development. UBR5 expression is deregulated in many cancer types and UBR5 is frequently mutated in mantle cell lymphoma. UBR5 is highly conserved in metazoans, has unique structural features, and has been implicated in regulation of DNA damage response, metabolism, transcription, and apoptosis. Hence, UBR5 is a key regulator of cell signaling relevant to broad areas of cancer biology. However, the mechanism by which UBR5 may contribute to tumor initiation and progression remains poorly defined. This review synthesizes emerging insights from genetics, biochemistry, and cell biology to inform our understanding of UBR5 in cancer. These molecular insights indicate a role for UBR5 in integrating/coordinating various cellular signaling pathways. Finally, we discuss outstanding questions in UBR5 biology and highlight the need to systematically characterize substrates, and address limitations in current animal models, to better define the role of UBR5 in cancer.
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Affiliation(s)
- Robert F Shearer
- Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, Australia. St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Mary Iconomou
- Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, Australia. St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Colin K W Watts
- Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, Australia
| | - Darren N Saunders
- Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, Australia. School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia.
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E3 ligase EDD1/UBR5 is utilized by the HPV E6 oncogene to destabilize tumor suppressor TIP60. Oncogene 2015; 35:2062-74. [DOI: 10.1038/onc.2015.268] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 05/04/2015] [Accepted: 06/07/2015] [Indexed: 02/08/2023]
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Abstract
Human papilloma virus (HPV)-associated head and neck carcinoma is quite heterogeneous and most of the tumors arise in the oral cavity, oropharynx, hypopharynx and larynx. HPV was just recently recognized as an emerging risk factor for oropharyngeal squamous cell carcinoma (OSCC). HPV(+) tumors represent 5-20% of all head and neck squamous-cell carcinomas (HNSCCs) and 40-90% of those arising from the oropharynx, with widely variable rates depending on the geographic area, population, relative prevalence of environment-related SCC and detection assay. Different carcinogenic mechanisms are most likely implicated in cervical and oropharyngeal carcinogenesis. The most certain carcinogenic genotype for the head and neck region and the most common high-risk HPV genotype, HPV-16, is frequently detected in OSCC. A combination of p16INK4A expression and molecular detection of HPV DNA is the gold standard for the viral identification in tissue and exfoliated cell samples. Differences in the biology of HPV(+) and HPV(-) OSCC may have implications for the management of patients. New immunotherapy drugs based on the release of the co-inhibitory receptors, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed-death 1 (PD-1) have currently emerged. The goal of therapeutic cancer vaccination is inculcation of a persistent, tumor antigen-specific T cell response which kills tumor cells. The efficacy of the current HPV vaccines, Cervarix and Gardasil, in preventing HPV-related HNSCC is at present unknown. Treatment de-escalation is recommended as the current management of HPV-induced HNSCCs.
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Affiliation(s)
- Apostolos Zaravinos
- Molecular Medicine Research Center and Laboratory of Molecular and Medical Genetics, Department of Biological Sciences, University of Cyprus, 1678 Nicosia, Cyprus. Division of Clinical Immunology and Transfusion Medicine, Department of Laboratory Medicine, Karolinska Institutet, 14145 Huddinge, Sweden
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Angelman syndrome-associated ubiquitin ligase UBE3A/E6AP mutants interfere with the proteolytic activity of the proteasome. Cell Death Dis 2015; 6:e1625. [PMID: 25633294 PMCID: PMC4669770 DOI: 10.1038/cddis.2014.572] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 11/25/2014] [Accepted: 11/26/2014] [Indexed: 11/08/2022]
Abstract
Angelman syndrome, a severe neurodevelopmental disease, occurs primarily due to genetic defects, which cause lack of expression or mutations in the wild-type E6AP/UBE3A protein. A proportion of the Angelman syndrome patients bear UBE3A point mutations, which do not interfere with the expression of the full-length protein, however, these individuals still develop physiological conditions of the disease. Interestingly, most of these mutations are catalytically defective, thereby indicating the importance of UBE3A enzymatic activity role in the Angelman syndrome pathology. In this study, we show that Angelman syndrome-associated mutants interact strongly with the proteasome via the S5a proteasomal subunit, resulting in an overall inhibitory effect on the proteolytic activity of the proteasome. Our results suggest that mutated catalytically inactive forms of UBE3A may cause defects in overall proteasome function, which could have an important role in the Angelman syndrome pathology.
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Holloway A, Simmonds M, Azad A, Fox JL, Storey A. Resistance to UV-induced apoptosis by β-HPV5 E6 involves targeting of activated BAK for proteolysis by recruitment of the HERC1 ubiquitin ligase. Int J Cancer 2014; 136:2831-43. [PMID: 25408501 DOI: 10.1002/ijc.29350] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 11/04/2014] [Indexed: 11/11/2022]
Abstract
UV exposure is the main etiological agent in the development of non-melanoma skin cancer (NMSC), but mounting evidence suggests a co-factorial role for β-genus HPV types early in tumor initiation or progression. UV damage initiates an apoptotic response, driven at the mitochondrial level by BCL-2 family proteins, that eliminates damaged cells that may accumulate deleterious mutations and acquire tumorigenic properties. BAK is a pro-apoptotic BCL-2 protein that functions ultimately to form pores that permeabilize the mitochondrial outer membrane, thereby committing a cell to death, a process involving changes in BAK phosphorylation and conformation. The E6 protein of β-type HPV5 signals BAK for proteasomal degradation, a function that confers protection from UV-induced apoptosis. We find that HPV5 E6 does not constitutively target BAK for proteolysis, but targets the latter stages of BAK activation, following changes in phosphorylation and conformation. A mutational analysis identified the lysine residue on BAK required for proteolysis, and a functional siRNA screen identified the HECT domain E3 ubiquitin ligase HERC1 as being required for E6-mediated BAK degradation. We show that HERC1 interacts with BAK in E6-expressing cells that have been damaged by UV, and provide evidence that the interaction of HERC1 with BAK requires access to a hydrophobic surface on BAK that binds BH3 domains of BCL-2 proteins. We also show that HERC1 contains a putative BH3 domain that can bind to BAK. These findings reveal a specific and unique mechanism used by the HPV5 E6 protein to target BAK.
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Affiliation(s)
- Amy Holloway
- Department of Oncology, Weatherall Institute of Molecular Medicine,University of Oxford, OX3 9DS, United Kingdom
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Sominsky S, Kuslansky Y, Shapiro B, Jackman A, Haupt Y, Rosin-Arbesfeld R, Sherman L. HPV16 E6 and E6AP differentially cooperate to stimulate or augment Wnt signaling. Virology 2014; 468-470:510-523. [PMID: 25262469 DOI: 10.1016/j.virol.2014.09.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 08/05/2014] [Accepted: 09/08/2014] [Indexed: 01/24/2023]
Abstract
The present study investigated the roles of E6 and E6AP in the Wnt pathway. We showed that E6 levels are markedly reduced in cells in which Wnt signaling is activated. Coexpression of wild-type or mutant E6AP (C820A) in Wnt-activated cells stabilized E6 and enhanced Wnt/β-catenin/TCF transcription. Expression of E6AP alone in nonstimulated cells elevated β-catenin level, promoted its nuclear accumulation, and activated β-catenin/TCF transcription. A knockdown of E6AP lowered β-catenin levels. Coexpression with E6 intensified the activities of E6AP. Further experiments proved that E6AP/E6 stabilize β-catenin by protecting it from proteasomal degradation. This function was dependent on the catalytic activity of E6AP, the kinase activity of GSK3β and the susceptibility of β-catenin to GSK3β phosphorylation. Thus, this study identified E6AP as a novel regulator of the Wnt signaling pathway, capable of cooperating with E6 in stimulating or augmenting Wnt/β-catenin signaling, thereby possibly contributing to HPV carcinogenesis.
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Affiliation(s)
- Sophia Sominsky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Yael Kuslansky
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Beny Shapiro
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Anna Jackman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Ygal Haupt
- Research Division, The Peter MacCallum Cancer Centre, East Melbourne, Australia.
| | - Rina Rosin-Arbesfeld
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
| | - Levana Sherman
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
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The role of ubiquitin and ubiquitin-like modification systems in papillomavirus biology. Viruses 2014; 6:3584-611. [PMID: 25254385 PMCID: PMC4189040 DOI: 10.3390/v6093584] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 09/17/2014] [Accepted: 09/18/2014] [Indexed: 12/12/2022] Open
Abstract
Human papillomaviruses (HPVs) are small DNA viruses that are important etiological agents of a spectrum of human skin lesions from benign to malignant. Because of their limited genome coding capacity they express only a small number of proteins, only one of which has enzymatic activity. Additionally, the HPV productive life cycle is intimately tied to the epithelial differentiation program and they must replicate in what are normally non-replicative cells, thus, these viruses must reprogram the cellular environment to achieve viral reproduction. Because of these limitations and needs, the viral proteins have evolved to co-opt cellular processes primarily through protein-protein interactions with critical host proteins. The ubiquitin post-translational modification system and the related ubiquitin-like modifiers constitute a widespread cellular regulatory network that controls the levels and functions of thousands of proteins, making these systems an attractive target for viral manipulation. This review describes the interactions between HPVs and the ubiquitin family of modifiers, both to regulate the viral proteins themselves and to remodel the host cell to facilitate viral survival and reproduction.
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Broniarczyk J, Bergant M, Goździcka-Józefiak A, Banks L. Human papillomavirus infection requires the TSG101 component of the ESCRT machinery. Virology 2014; 460-461:83-90. [PMID: 25010273 DOI: 10.1016/j.virol.2014.05.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/10/2014] [Accepted: 05/06/2014] [Indexed: 12/21/2022]
Abstract
Infection with human papillomaviruses (HPV) requires the minor capsid component L2, which plays an essential role in directing appropriate endosomal trafficking. Previous studies have indicated an infection route involving multi-vesicular bodies (MVBs), and an essential element in their biogenesis is the ESCRT machinery. Here we show that the ESCRT component TSG101 is required for optimal infection with both HPV-16 and BPV-1, with loss of TSG101 resulting in a decrease in viral infection, whereas overexpressed TSG101 increases rates of infection. We find that L2 proteins from multiple PV types interact with TSG101 and show that this interaction contributes to an alteration in the subcellular distribution of L2. In addition, TSG101 can modulate the levels of L2 polyubiquitination. These results demonstrate that TSG101 plays an important part in infection with diverse PVs, and suggests that trafficking of HPV through the ESCRT machinery and MVBs is part of infectious virus entry.
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Affiliation(s)
- Justyna Broniarczyk
- Department of Molecular Virology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Martina Bergant
- Laboratory for Environmental Research, University of Nova Gorica, Nova Gorica, Slovenia
| | - Anna Goździcka-Józefiak
- Department of Molecular Virology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
| | - Lawrence Banks
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34149 Trieste, Italy.
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Alpsoy A, Yasa S, Gündüz U. Etoposide resistance in MCF-7 breast cancer cell line is marked by multiple mechanisms. Biomed Pharmacother 2014; 68:351-5. [DOI: 10.1016/j.biopha.2013.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 09/24/2013] [Indexed: 12/25/2022] Open
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Abstract
Human papillomavirus (HPV) infection is clinically very common. It is usually a major risk factor in the development of cutaneous benign lesions, cervical cancer and a variety of other malignancies. The biological function of ubiquitination as an intracellular proteasomal-mediated form of protein degradation and an important modulator in the regulation of many fundamental cellular processes has been increasingly recognized over the last decade. HPV proteins have been demonstrated to evolve different strategies to utilize the ubiquitin system for their own purposes. The putative roles of E3 ubiquitin ligases in HPV-induced carcinogenesis have become increasingly apparent, although the mechanisms remain unclear. In this review we provide an update on the mechanisms of the involvement of E3 ubiquitin ligases in HPV-induced carcinogenesis, focusing on their interaction with HPV proteins and their roles in several signalling pathways. Targeting the E3 ubiquitin ligases might offer potential therapeutic strategies for HPV-related diseases in future.
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Affiliation(s)
- Zhifeng Lou
- Department of Dentistry, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China
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Tomaić V, Ganti K, Pim D, Bauer C, Blattner C, Banks L. Interaction of HPV E6 oncoproteins with specific proteasomal subunits. Virology 2013; 446:389-96. [PMID: 24074603 DOI: 10.1016/j.virol.2013.08.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 04/25/2013] [Accepted: 08/14/2013] [Indexed: 10/26/2022]
Abstract
The Human Papillomavirus E6 oncoproteins have the capacity to target several of their cellular interacting partners for proteasome mediated degradation, and recent proteomic analyses suggest a close involvement of E6 with the cellular proteasome machinery. In this study we have performed an extensive analysis of the capacity of different E6 oncoproteins to interact with specific proteasome components. We demonstrate that multiple subunits of the proteasome can be bound by different HPV E6 oncoproteins. Furthermore, whilst most of these interactions appear independent of the E6AP ubiquitin ligase, the association of E6 with the major ubiquitin-accepting proteasome subunit, S5a, does require the presence of E6AP. One consequence of the interaction between E6/E6AP and S5a is enhanced ubiquitination of this proteasome subunit. These results suggest a complex interplay between E6 and the proteasome, only some aspects of which are dependent upon the E6AP ubiquitin ligase.
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Affiliation(s)
- Vjekoslav Tomaić
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34149 Trieste, Italy
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Scheffner M, Kumar S. Mammalian HECT ubiquitin-protein ligases: biological and pathophysiological aspects. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:61-74. [PMID: 23545411 DOI: 10.1016/j.bbamcr.2013.03.024] [Citation(s) in RCA: 217] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/18/2013] [Accepted: 03/22/2013] [Indexed: 10/27/2022]
Abstract
Members of the HECT family of E3 ubiquitin-protein ligases are characterized by a C-terminal HECT domain that catalyzes the covalent attachment of ubiquitin to substrate proteins and by N-terminal extensions of variable length and domain architecture that determine the substrate spectrum of a respective HECT E3. Since their discovery in 1995, it has become clear that deregulation of distinct HECT E3s plays an eminent role in human disease or disease-related processes including cancer, cardiovascular and neurological disorders, viral infections, and immune response. Thus, a detailed understanding of the structure-function aspects of HECT E3s as well as the identification and characterization of the substrates and regulators of HECT E3s is critical in developing new approaches in the treatment of respective diseases. In this review, we summarize what is currently known about mammalian HECT E3s, with a focus on their biological functions and roles in pathophysiology.This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- Martin Scheffner
- Department of Biology, Konstanz Research School Chemical Biology, University of Konstanz, Konstanz, Germany.
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Morrison J, Laurent-Rolle M, Maestre AM, Rajsbaum R, Pisanelli G, Simon V, Mulder LCF, Fernandez-Sesma A, García-Sastre A. Dengue virus co-opts UBR4 to degrade STAT2 and antagonize type I interferon signaling. PLoS Pathog 2013; 9:e1003265. [PMID: 23555265 PMCID: PMC3610674 DOI: 10.1371/journal.ppat.1003265] [Citation(s) in RCA: 170] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 02/06/2013] [Indexed: 12/12/2022] Open
Abstract
An estimated 50 million dengue virus (DENV) infections occur annually and more than forty percent of the human population is currently at risk of developing dengue fever (DF) or dengue hemorrhagic fever (DHF). Despite the prevalence and potential severity of DF and DHF, there are no approved vaccines or antiviral therapeutics available. An improved understanding of DENV immune evasion is pivotal for the rational development of anti-DENV therapeutics. Antagonism of type I interferon (IFN-I) signaling is a crucial mechanism of DENV immune evasion. DENV NS5 protein inhibits IFN-I signaling by mediating proteasome-dependent STAT2 degradation. Only proteolytically-processed NS5 can efficiently mediate STAT2 degradation, though both unprocessed and processed NS5 bind STAT2. Here we identify UBR4, a 600-kDa member of the N-recognin family, as an interacting partner of DENV NS5 that preferentially binds to processed NS5. Our results also demonstrate that DENV NS5 bridges STAT2 and UBR4. Furthermore, we show that UBR4 promotes DENV-mediated STAT2 degradation, and most importantly, that UBR4 is necessary for efficient viral replication in IFN-I competent cells. Our data underscore the importance of NS5-mediated STAT2 degradation in DENV replication and identify UBR4 as a host protein that is specifically exploited by DENV to inhibit IFN-I signaling via STAT2 degradation. Dengue virus (DENV) is the leading cause of mosquito-borne viral illness and death in humans. At present, there are no vaccines and no specific antiviral therapeutics to prevent or treat DENV infections. We previously described that the NS5 protein of DENV inhibits type I interferon signaling in virus-infected cells by mediating STAT2 degradation. This property allows DENV to overcome the antiviral effects of type I interferon, contributing to viral replication in the host. We have now obtained new insight into the mechanism by which DENV NS5 induces STAT2 degradation. NS5 bridges STAT2 with the cellular protein UBR4, a member of a family of predicted E3 ligases, resulting in UBR4-mediated STAT2 degradation. Elimination of UBR4 or mutations in NS5 that prevent its binding to UBR4 prevent NS5 from inducing STAT2 degradation. Importantly, UBR4 is required for optimal DENV replication in the presence of a competent type I interferon system. Our data demonstrate the requirement of a host factor, UBR4, for DENV to overcome the antiviral interferon response. This information might be important for the design of specific DENV inhibitors that prevent dengue virus from evading innate immunity.
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Affiliation(s)
- Juliet Morrison
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Maudry Laurent-Rolle
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Ana M. Maestre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Ricardo Rajsbaum
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Giuseppe Pisanelli
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples, Italy
| | - Viviana Simon
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Lubbertus C. F. Mulder
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Ana Fernandez-Sesma
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- * E-mail:
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Grau-Bové X, Sebé-Pedrós A, Ruiz-Trillo I. A genomic survey of HECT ubiquitin ligases in eukaryotes reveals independent expansions of the HECT system in several lineages. Genome Biol Evol 2013; 5:833-47. [PMID: 23563970 PMCID: PMC3673628 DOI: 10.1093/gbe/evt052] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2013] [Indexed: 12/19/2022] Open
Abstract
The posttranslational modification of proteins by the ubiquitination pathway is an important regulatory mechanism in eukaryotes. To date, however, studies on the evolutionary history of the proteins involved in this pathway have been restricted to E1 and E2 enzymes, whereas E3 studies have been focused mainly in metazoans and plants. To have a wider perspective, here we perform a genomic survey of the HECT family of E3 ubiquitin-protein ligases, an important part of this posttranslational pathway, in genomes from representatives of all major eukaryotic lineages. We classify eukaryotic HECTs and reconstruct, by phylogenetic analysis, the putative repertoire of these proteins in the last eukaryotic common ancestor (LECA). Furthermore, we analyze the diversity and complexity of protein domain architectures of HECTs along the different extant eukaryotic lineages. Our data show that LECA had six different HECTs and that protein expansion and N-terminal domain diversification shaped HECT evolution. Our data reveal that the genomes of animals and unicellular holozoans considerably increased the molecular and functional diversity of their HECT system compared with other eukaryotes. Other eukaryotes, such as the Apusozoa Thecanomas trahens or the Heterokonta Phytophthora infestans, independently expanded their HECT repertoire. In contrast, plant, excavate, rhodophyte, chlorophyte, and fungal genomes have a more limited enzymatic repertoire. Our genomic survey and phylogenetic analysis clarifies the origin and evolution of different HECT families among eukaryotes and provides a useful phylogenetic framework for future evolutionary studies of this regulatory pathway.
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Affiliation(s)
- Xavier Grau-Bové
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
| | - Arnau Sebé-Pedrós
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
| | - Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Catalonia, Spain
- Departament de Genètica, Universitat de Barcelona, Catalonia, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Catalonia, Spain
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Thomas M, Tomaić V, Pim D, Myers MP, Tommasino M, Banks L. Interactions between E6AP and E6 proteins from alpha and beta HPV types. Virology 2012. [PMID: 23206439 DOI: 10.1016/j.virol.2012.11.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
High-risk mucosotropic Human papillomaviruses (HPVs), especially HPV-16, are the aetiological agents of cervical cancer and the cellular targets of their E6 oncoproteins have been much studied. However, much less is known about the cellular targets of the cutaneous HPV E6 proteins. In this study, a proteomic analysis of cells transfected with the E6 proteins from cutaneous HPV types specifically identified E6-interacting proteins involved in the ubiquitination pathways. These include the E3 ubiquitin-protein ligases E6AP and UBR4/p600. We also show that E6AP can contribute towards the steady-state levels of E6 and, conversely, that certain E6 proteins, in addition to those derived from the high-risk mucosal HPV types, can enhance levels of E6AP turnover. These results define important differences and commonalities in how HPV E6 proteins of mucosal and cutaneous origin interact with cellular ubiquitin-protein ligases.
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Affiliation(s)
- Miranda Thomas
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, Trieste 34149, Italy.
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Zanier K, Sidi AOMO, Boulade-Ladame C, Rybin V, Chappelle A, Atkinson A, Kieffer B, Travé G. Solution structure analysis of the HPV16 E6 oncoprotein reveals a self-association mechanism required for E6-mediated degradation of p53. Structure 2012; 20:604-17. [PMID: 22483108 PMCID: PMC3325491 DOI: 10.1016/j.str.2012.02.001] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 01/31/2012] [Accepted: 02/09/2012] [Indexed: 10/28/2022]
Abstract
The viral oncoprotein E6 is an essential factor for cervical cancers induced by "high-risk" mucosal HPV. Among other oncogenic activities, E6 recruits the ubiquitin ligase E6AP to promote the ubiquitination and subsequent proteasomal degradation of p53. E6 is prone to self-association, which long precluded its structural analysis. Here we found that E6 specifically dimerizes through its N-terminal domain and that disruption of the dimer interface strongly increases E6 solubility. This allowed us to raise structural data covering the entire HPV16 E6 protein, including the high-resolution NMR structures of the two zinc-binding domains of E6 and a robust data-driven model structure of the N-terminal domain homodimer. Interestingly, homodimer interface mutations that disrupt E6 self-association also inactivate E6-mediated p53 degradation. These data suggest that E6 needs to self-associate via its N-terminal domain to promote the polyubiquitination of p53 by E6AP.
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Affiliation(s)
- Katia Zanier
- Institut de Recherche de l’Ecole de Biotechnologie de Strasbourg (IREBS), Boulevard Sébastien Brant, BP 10413, 67412 Illkirch, France
| | - Abdellahi ould M’hamed ould Sidi
- Institut de Recherche de l’Ecole de Biotechnologie de Strasbourg (IREBS), Boulevard Sébastien Brant, BP 10413, 67412 Illkirch, France
| | - Charlotte Boulade-Ladame
- Institut de Recherche de l’Ecole de Biotechnologie de Strasbourg (IREBS), Boulevard Sébastien Brant, BP 10413, 67412 Illkirch, France
| | - Vladimir Rybin
- European Molecular Biology Laboratories (EMBL), Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Anne Chappelle
- Institut de Recherche de l’Ecole de Biotechnologie de Strasbourg (IREBS), Boulevard Sébastien Brant, BP 10413, 67412 Illkirch, France
| | - Andrew Atkinson
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 1 rue Laurent Fries, BP 163, 67404 Illkirch, France
| | - Bruno Kieffer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 1 rue Laurent Fries, BP 163, 67404 Illkirch, France
| | - Gilles Travé
- Institut de Recherche de l’Ecole de Biotechnologie de Strasbourg (IREBS), Boulevard Sébastien Brant, BP 10413, 67412 Illkirch, France
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p53 degradation activity, expression, and subcellular localization of E6 proteins from 29 human papillomavirus genotypes. J Virol 2011; 86:94-107. [PMID: 22013048 DOI: 10.1128/jvi.00751-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses (HPVs) are the etiological agents of cervical cancer and other human malignancies. HPVs are classified into high- and low-risk genotypes according to their association with cancer. Host cell transformation by high-risk HPVs relies in part on the ability of the viral E6 protein to induce the degradation of p53. We report the development of a cellular assay that accurately quantifies the p53 degradation activity of E6 in vivo, based on the fusion of p53 to Renilla luciferase (RLuc-p53). This assay was used to measure the p53 degradation activities of E6 proteins from 29 prevalent HPV types and variants of HPV type 16 (HPV16) and HPV33 by determining the amount of E6 expression vector required to reduce by half the levels of RLuc-p53 (50% effective concentration [EC₅₀]). These studies revealed an unexpected variability in the p53 degradation activities of different E6 proteins, even among active types whose EC₅₀s span more than 2 log units. Differences in activity were greater between types than between variants and did not correlate with differences in the intracellular localization of E6, with most being predominantly nuclear. Protein and mRNA expression of the 29 E6 proteins was also examined. For 16 high-risk types, spliced transcripts that encode shorter E6*I proteins of variable sizes and abundances were detected. Mutation of the splice donor site in five different E6 proteins increased their p53 degradation activity, suggesting that mRNA splicing can limit the activity of some high-risk E6 types. The quantification of p53 degradation in vivo represents a novel tool to systematically compare the oncogenic potentials of E6 proteins from different HPV types and variants.
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50
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Varshavsky A. The N-end rule pathway and regulation by proteolysis. Protein Sci 2011; 20:1298-345. [PMID: 21633985 PMCID: PMC3189519 DOI: 10.1002/pro.666] [Citation(s) in RCA: 517] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 05/16/2011] [Accepted: 05/18/2011] [Indexed: 01/12/2023]
Abstract
The N-end rule relates the regulation of the in vivo half-life of a protein to the identity of its N-terminal residue. Degradation signals (degrons) that are targeted by the N-end rule pathway include a set called N-degrons. The main determinant of an N-degron is a destabilizing N-terminal residue of a protein. In eukaryotes, the N-end rule pathway is a part of the ubiquitin system and consists of two branches, the Ac/N-end rule and the Arg/N-end rule pathways. The Ac/N-end rule pathway targets proteins containing N(α) -terminally acetylated (Nt-acetylated) residues. The Arg/N-end rule pathway recognizes unacetylated N-terminal residues and involves N-terminal arginylation. Together, these branches target for degradation a majority of cellular proteins. For example, more than 80% of human proteins are cotranslationally Nt-acetylated. Thus most proteins harbor a specific degradation signal, termed (Ac)N-degron, from the moment of their birth. Specific N-end rule pathways are also present in prokaryotes and in mitochondria. Enzymes that produce N-degrons include methionine-aminopeptidases, caspases, calpains, Nt-acetylases, Nt-amidases, arginyl-transferases and leucyl-transferases. Regulated degradation of specific proteins by the N-end rule pathway mediates a legion of physiological functions, including the sensing of heme, oxygen, and nitric oxide; selective elimination of misfolded proteins; the regulation of DNA repair, segregation and condensation; the signaling by G proteins; the regulation of peptide import, fat metabolism, viral and bacterial infections, apoptosis, meiosis, spermatogenesis, neurogenesis, and cardiovascular development; and the functioning of adult organs, including the pancreas and the brain. Discovered 25 years ago, this pathway continues to be a fount of biological insights.
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Affiliation(s)
- Alexander Varshavsky
- 1Division of Biology, California Institute of Technology, Pasadena, California 91125.
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