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Abstract
MYC is a master transcriptional regulator that controls almost all cellular processes. Over the last several decades, researchers have strived to define the context-dependent transcriptional gene programs that are controlled by MYC, as well as the mechanisms that regulate MYC function, in an effort to better understand the contribution of this oncoprotein to cancer progression. There are a wealth of data indicating that deregulation of MYC activity occurs in a large number of cancers and significantly contributes to disease progression, metastatic potential, and therapeutic resistance. Although the therapeutic targeting of MYC in cancer is highly desirable, there remain substantial structural and functional challenges that have impeded direct MYC-targeted drug development and efficacy. While efforts to drug the ‘undruggable’ may seem futile given these challenges and considering the broad reach of MYC, significant strides have been made to identify points of regulation that can be exploited for therapeutic purposes. These include targeting the deregulation of MYC transcription in cancer through small-molecule inhibitors that induce epigenetic silencing or that regulate the G-quadruplex structures within the MYC promoter. Alternatively, compounds that disrupt the DNA-binding activities of MYC have been the long-standing focus of many research groups, since this method would prevent downstream MYC oncogenic activities regardless of upstream alterations. Finally, proteins involved in the post-translational regulation of MYC have been identified as important surrogate targets to reduce MYC activity downstream of aberrant cell stimulatory signals. Given the complex regulation of the MYC signaling pathway, a combination of these approaches may provide the most durable response, but this has yet to be shown. Here, we provide a comprehensive overview of the different therapeutic strategies being employed to target oncogenic MYC function, with a focus on post-translational mechanisms.
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Gâtel P, Piechaczyk M, Bossis G. Ubiquitin, SUMO, and Nedd8 as Therapeutic Targets in Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1233:29-54. [PMID: 32274752 DOI: 10.1007/978-3-030-38266-7_2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ubiquitin defines a family of approximately 20 peptidic posttranslational modifiers collectively called the Ubiquitin-like (UbLs). They are conjugated to thousands of proteins, modifying their function and fate in many ways. Dysregulation of these modifications has been implicated in a variety of pathologies, in particular cancer. Ubiquitin, SUMO (-1 to -3), and Nedd8 are the best-characterized UbLs. They have been involved in the regulation of the activity and/or the stability of diverse components of various oncogenic or tumor suppressor pathways. Moreover, the dysregulation of enzymes responsible for their conjugation/deconjugation has also been associated with tumorigenesis and cancer resistance to therapies. The UbL system therefore constitutes an attractive target for developing novel anticancer therapeutic strategies. Here, we review the roles and dysregulations of Ubiquitin, SUMO, and Nedd8 pathways in tumorigenesis, as well as recent advances in the identification of small molecules targeting their conjugating machineries for potential application in the fight against cancer.
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Affiliation(s)
- Pierre Gâtel
- Equipe Labellisée Ligue Contre le Cancer, IGMM, Univ Montpellier, CNRS, Montpellier, France
| | - Marc Piechaczyk
- Equipe Labellisée Ligue Contre le Cancer, IGMM, Univ Montpellier, CNRS, Montpellier, France
| | - Guillaume Bossis
- Equipe Labellisée Ligue Contre le Cancer, IGMM, Univ Montpellier, CNRS, Montpellier, France.
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Xie M, Yu J, Ge S, Huang J, Fan X. SUMOylation homeostasis in tumorigenesis. Cancer Lett 2020; 469:301-309. [DOI: 10.1016/j.canlet.2019.11.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/19/2019] [Accepted: 11/01/2019] [Indexed: 10/25/2022]
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Peng Y, Wang Z, Wang Z, Yu F, Li J, Wong J. SUMOylation down-regulates rDNA transcription by repressing expression of upstream-binding factor and proto-oncogene c-Myc. J Biol Chem 2019; 294:19155-19166. [PMID: 31694914 DOI: 10.1074/jbc.ra119.010624] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 10/29/2019] [Indexed: 11/06/2022] Open
Abstract
Ribosome biogenesis is critical for proliferating cells and requires the coordinated activities of three eukaryotic RNA polymerases. We recently showed that the small ubiquitin-like modifier (SUMO) system controls the global level of RNA polymerase II (Pol II)-controlled transcription in mammalian cells by regulating cyclin-dependent kinase 9 activity. Here, we present evidence that the SUMO system also plays a critical role in the control of Pol I transcription. Using an siRNA-based knockdown approach, we found that multiple SUMO E3 ligases of the PIAS (protein inhibitor of activated STAT) family are involved in SUMO-mediated repression of ribosomal DNA (rDNA) gene transcription. We demonstrate that endogenous SUMO represses rDNA transcription primarily by repressing upstream-binding factor and proto-oncogene c-Myc expression and that ectopic overexpression of SUMO-associated enzymes additionally represses rDNA transcription via c-Myc SUMOylation and its subsequent degradation. The results of our study reveal a critical role of SUMOylation in the control of rDNA transcription, uncover the underlying mechanisms involved, and indicate that the SUMO system coordinates Pol I- and Pol II-mediated transcription in mammalian cells.
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Affiliation(s)
- Yu Peng
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Zhenxing Wang
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Zhiqiang Wang
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Fang Yu
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China.,Department of Medicine, University of Florida, Gainesville, Florida 32610
| | - Jiwen Li
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Jiemin Wong
- Shanghai Key Laboratory of Regulatory Biology, Fengxian District Central Hospital-East China Normal University Joint Center of Translational Medicine, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China .,State Key Laboratory of Oncogene and Related Genes, Shanghai Cancer Institute and Shanghai Jiao Tong University, Shanghai 200240, China
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Xiang JW, Zhang L, Tang X, Xiao Y, Liu Y, Wang L, Liu F, Gong XD, Fu JL, Yang L, Luo Z, Li DWC. Differential Expression of Seven De-sumoylation Enzymes (SENPs) in Major Ocular Tissues of Mouse Eye. Curr Mol Med 2019; 18:533-541. [PMID: 30636607 DOI: 10.2174/1566524019666190112132103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/07/2019] [Accepted: 01/07/2019] [Indexed: 11/22/2022]
Abstract
PURPOSE Protein Sumoylation is one of the most important and prevalent posttranscriptional modification. Increasing evidence have shown that the SENPs (sentrin/SUMOspecific proteases) are critical for steady-state levels of SUMO modification of target proteins, and protein de-sumoylation modulates a great diversity of biological processes including transcription, development, differentiation, neuroprotection, as well as pathogenesis. In the vertebrate eye, we and others have previously shown that sumoylation participated in the differentiation of major ocular tissues including retina and lens. However, the biological significance of seven SENP enzymes: SENP1 to 3 and SENP5 to 8 have not be fully investigated in the ocular tissues. METHODS The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J. RESULTS At the mRNA level, all SENPs were highly expressed in retina, and much reduced expression patterns in cornea, lens epithelium and lens fiber. At the protein level, SENP1 to -3, and SENP6 were highly abundant in cornea, while SENP5, SENP7 and SENP8 were enriched in retina, and these SENPs were relatively less abundant in lens tissues. CONCLUSION Our results for the first time established the differentiation expression patterns of the 7 de-sumoylation enzymes (SENPs), which provides a basis for further investigation of protein desumoylation functions in vertebrate eye.
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Affiliation(s)
- Jia-Wen Xiang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Lan Zhang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Xiangcheng Tang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Yuan Xiao
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Yunfei Liu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Ling Wang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Fangyuan Liu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Xiao-Dong Gong
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Jia-Ling Fu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Lan Yang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - Zhongwen Luo
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
| | - David Wan-Cheng Li
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Guangzhou, Guangdong 510230, China
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Chen Y, Sun XX, Sears RC, Dai MS. Writing and erasing MYC ubiquitination and SUMOylation. Genes Dis 2019; 6:359-371. [PMID: 31832515 PMCID: PMC6889025 DOI: 10.1016/j.gendis.2019.05.006] [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: 04/24/2019] [Revised: 05/23/2019] [Accepted: 05/29/2019] [Indexed: 12/22/2022] Open
Abstract
The transcription factor c-MYC (MYC thereafter) controls diverse transcription programs and plays a key role in the development of many human cancers. Cells develop multiple mechanisms to ensure that MYC levels and activity are precisely controlled in normal physiological context. As a short half-lived protein, MYC protein levels are tightly regulated by the ubiquitin proteasome system. Over a dozen of ubiquitin ligases have been found to ubiquitinate MYC whereas a number of deubiquitinating enzymes counteract this process. Recent studies show that SUMOylation and deSUMOylation can also regulate MYC protein stability and activity. Interestingly, evidence suggests an intriguing crosstalk between MYC ubiquitination and SUMOylation. Deregulation of the MYC ubiquitination-SUMOylation regulatory network may contribute to tumorigenesis. This review is intended to provide the current understanding of the complex regulation of the MYC biology by dynamic ubiquitination and SUMOylation and their crosstalk.
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Affiliation(s)
- Yingxiao Chen
- Departments of Molecular & Medical Genetics, School of Medicine, OHSU Knight Cancer Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Xiao-Xin Sun
- Departments of Molecular & Medical Genetics, School of Medicine, OHSU Knight Cancer Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Rosalie C Sears
- Departments of Molecular & Medical Genetics, School of Medicine, OHSU Knight Cancer Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Mu-Shui Dai
- Departments of Molecular & Medical Genetics, School of Medicine, OHSU Knight Cancer Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
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Sammak S, Hamdani N, Gorrec F, Allen MD, Freund SMV, Bycroft M, Zinzalla G. Crystal Structures and Nuclear Magnetic Resonance Studies of the Apo Form of the c-MYC:MAX bHLHZip Complex Reveal a Helical Basic Region in the Absence of DNA. Biochemistry 2019; 58:3144-3154. [PMID: 31260268 PMCID: PMC6791285 DOI: 10.1021/acs.biochem.9b00296] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
The c-MYC transcription
factor is a master regulator of cell growth
and proliferation and is an established target for cancer therapy.
This basic helix–loop–helix Zip protein forms a heterodimer
with its obligatory partner MAX, which binds to DNA via the basic
region. Considerable research efforts are focused on targeting the
heterodimerization interface and the interaction of the complex with
DNA. The only available crystal structure is that of a c-MYC:MAX complex
artificially tethered by an engineered disulfide linker and prebound
to DNA. We have carried out a detailed structural analysis of the
apo form of the c-MYC:MAX complex, with no artificial linker, both
in solution using nuclear magnetic resonance (NMR) spectroscopy and
by X-ray crystallography. We have obtained crystal structures in three
different crystal forms, with resolutions between 1.35 and 2.2 Å,
that show extensive helical structure in the basic region. Determination
of the α-helical propensity using NMR chemical shift analysis
shows that the basic region of c-MYC and, to a lesser extent, that
of MAX populate helical conformations. We have also assigned the NMR
spectra of the c-MYC basic helix–loop–helix Zip motif
in the absence of MAX and showed that the basic region has an intrinsic
helical propensity even in the absence of its dimerization partner.
The presence of helical structure in the basic regions in the absence
of DNA suggests that the molecular recognition occurs via a conformational
selection rather than an induced fit. Our work provides both insight
into the mechanism of DNA binding and structural information to aid
in the development of MYC inhibitors.
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Affiliation(s)
- Susan Sammak
- Microbiology, Tumor and Cell Biology (MTC) , Karolinska Institutet , Solnavägen 9 , 171 65 Stockholm , Sweden
| | - Najoua Hamdani
- Microbiology, Tumor and Cell Biology (MTC) , Karolinska Institutet , Solnavägen 9 , 171 65 Stockholm , Sweden
| | - Fabrice Gorrec
- MRC Laboratory of Molecular Biology , Cambridge Biomedical Campus , Francis Crick Avenue , Cambridge CB2 0QH , U.K
| | - Mark D Allen
- MRC Laboratory of Molecular Biology , Cambridge Biomedical Campus , Francis Crick Avenue , Cambridge CB2 0QH , U.K
| | - Stefan M V Freund
- MRC Laboratory of Molecular Biology , Cambridge Biomedical Campus , Francis Crick Avenue , Cambridge CB2 0QH , U.K
| | - Mark Bycroft
- MRC Laboratory of Molecular Biology , Cambridge Biomedical Campus , Francis Crick Avenue , Cambridge CB2 0QH , U.K
| | - Giovanna Zinzalla
- Microbiology, Tumor and Cell Biology (MTC) , Karolinska Institutet , Solnavägen 9 , 171 65 Stockholm , Sweden
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