1
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Szulc NA, Stefaniak F, Piechota M, Soszyńska A, Piórkowska G, Cappannini A, Bujnicki J, Maniaci C, Pokrzywa W. DEGRONOPEDIA: a web server for proteome-wide inspection of degrons. Nucleic Acids Res 2024; 52:W221-W232. [PMID: 38567734 PMCID: PMC11223883 DOI: 10.1093/nar/gkae238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/12/2024] [Accepted: 03/20/2024] [Indexed: 07/06/2024] Open
Abstract
E3 ubiquitin ligases recognize substrates through their short linear motifs termed degrons. While degron-signaling has been a subject of extensive study, resources for its systematic screening are limited. To bridge this gap, we developed DEGRONOPEDIA, a web server that searches for degrons and maps them to nearby residues that can undergo ubiquitination and disordered regions, which may act as protein unfolding seeds. Along with an evolutionary assessment of degron conservation, the server also reports on post-translational modifications and mutations that may modulate degron availability. Acknowledging the prevalence of degrons at protein termini, DEGRONOPEDIA incorporates machine learning to assess N-/C-terminal stability, supplemented by simulations of proteolysis to identify degrons in newly formed termini. An experimental validation of a predicted C-terminal destabilizing motif, coupled with the confirmation of a post-proteolytic degron in another case, exemplifies its practical application. DEGRONOPEDIA can be freely accessed at degronopedia.com.
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Affiliation(s)
- Natalia A Szulc
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Filip Stefaniak
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Małgorzata Piechota
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Anna Soszyńska
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Gabriela Piórkowska
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Andrea Cappannini
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Janusz M Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
| | - Chiara Maniaci
- Medical Research Council (MRC) Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Wojciech Pokrzywa
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena Str., 02-109 Warsaw, Poland
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2
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Patel JA, Zezelic C, Rageul J, Saldanha J, Khan A, Kim H. Replisome dysfunction upon inducible TIMELESS degradation synergizes with ATR inhibition to trigger replication catastrophe. Nucleic Acids Res 2023; 51:6246-6263. [PMID: 37144518 PMCID: PMC10325925 DOI: 10.1093/nar/gkad363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 03/29/2023] [Accepted: 04/26/2023] [Indexed: 05/06/2023] Open
Abstract
The structure of DNA replication forks is preserved by TIMELESS (TIM) in the fork protection complex (FPC) to support seamless fork progression. While the scaffolding role of the FPC to couple the replisome activity is much appreciated, the detailed mechanism whereby inherent replication fork damage is sensed and counteracted during DNA replication remains largely elusive. Here, we implemented an auxin-based degron system that rapidly triggers inducible proteolysis of TIM as a source of endogenous DNA replication stress and replisome dysfunction to dissect the signaling events that unfold at stalled forks. We demonstrate that acute TIM degradation activates the ATR-CHK1 checkpoint, whose inhibition culminates in replication catastrophe by single-stranded DNA accumulation and RPA exhaustion. Mechanistically, unrestrained replisome uncoupling, excessive origin firing, and aberrant reversed fork processing account for the synergistic fork instability. Simultaneous TIM loss and ATR inactivation triggers DNA-PK-dependent CHK1 activation, which is unexpectedly necessary for promoting fork breakage by MRE11 and catastrophic cell death. We propose that acute replisome dysfunction results in a hyper-dependency on ATR to activate local and global fork stabilization mechanisms to counteract irreversible fork collapse. Our study identifies TIM as a point of replication vulnerability in cancer that can be exploited with ATR inhibitors.
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Affiliation(s)
- Jinal A Patel
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Camryn Zezelic
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Julie Rageul
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Joanne Saldanha
- The Graduate program in Genetics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Arafat Khan
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
- Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY 11794, USA
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3
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Anil AT, Choudhary K, Pandian R, Gupta P, Thakran P, Singh A, Sharma M, Mishra SK. Splicing of branchpoint-distant exons is promoted by Cactin, Tls1 and the ubiquitin-fold-activated Sde2. Nucleic Acids Res 2022; 50:10000-10014. [PMID: 36095128 PMCID: PMC9508853 DOI: 10.1093/nar/gkac769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/22/2022] [Accepted: 08/27/2022] [Indexed: 11/13/2022] Open
Abstract
Intron diversity facilitates regulated gene expression and alternative splicing. Spliceosomes excise introns after recognizing their splicing signals: the 5'-splice site (5'ss), branchpoint (BP) and 3'-splice site (3'ss). The latter two signals are recognized by U2 small nuclear ribonucleoprotein (snRNP) and its accessory factors (U2AFs), but longer spacings between them result in weaker splicing. Here, we show that excision of introns with a BP-distant 3'ss (e.g. rap1 intron 2) requires the ubiquitin-fold-activated splicing regulator Sde2 in Schizosaccharomyces pombe. By monitoring splicing-specific ura4 reporters in a collection of S. pombe mutants, Cay1 and Tls1 were identified as additional regulators of this process. The role of Sde2, Cay1 and Tls1 was further confirmed by increasing BP-3'ss spacings in a canonical tho5 intron. We also examined BP-distant exons spliced independently of these factors and observed that RNA secondary structures possibly bridged the gap between the two signals. These proteins may guide the 3'ss towards the spliceosome's catalytic centre by folding the RNA between the BP and 3'ss. Orthologues of Sde2, Cay1 and Tls1, although missing in the intron-poor Saccharomyces cerevisiae, are present in intron-rich eukaryotes, including humans. This type of intron-specific pre-mRNA splicing appears to have evolved for regulated gene expression and alternative splicing of key heterochromatin factors.
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Affiliation(s)
- Anupa T Anil
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Karan Choudhary
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Rakesh Pandian
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Praver Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Poonam Thakran
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Arashdeep Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Monika Sharma
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
| | - Shravan Kumar Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, 140306 Punjab, India
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4
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Extended DNA binding interfaces beyond the canonical SAP domain contribute to the function of replication stress regulator SDE2 at DNA replication forks. J Biol Chem 2022; 298:102268. [PMID: 35850305 PMCID: PMC9399289 DOI: 10.1016/j.jbc.2022.102268] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/05/2022] [Accepted: 07/07/2022] [Indexed: 11/25/2022] Open
Abstract
Elevated DNA replication stress causes instability of the DNA replication fork and increased DNA mutations, which underlies tumorigenesis. The DNA replication stress regulator silencing-defective 2 (SDE2) is known to bind to TIMELESS (TIM), a protein of the fork protection complex, and enhances its stability, thereby supporting replisome activity at DNA replication forks. However, the DNA-binding activity of SDE2 is not well defined. Here, we structurally and functionally characterize a new conserved DNA-binding motif related to the SAP (SAF-A/B, Acinus, PIAS) domain in human SDE2 and establish its preference for ssDNA. Our NMR solution structure of the SDE2SAP domain reveals a helix-extended loop-helix core with the helices aligned parallel to each other, consistent with known canonical SAP folds. Notably, we have shown that the DNA interaction of this SAP domain extends beyond the core SAP domain and is augmented by two lysine residues in the C-terminal tail, which is uniquely positioned adjacent to the SAP motif and conserved in the pre-mRNA splicing factor SF3A3. Furthermore, we found that mutation in the SAP domain and extended C terminus not only disrupts ssDNA binding but also impairs TIM localization at replication forks, thus inhibiting efficient fork progression. Taken together, our results establish SDE2SAP as an essential element for SDE2 to exert its role in preserving replication fork integrity via fork protection complex regulation and highlight the structural diversity of the DNA–protein interactions achieved by a specialized DNA-binding motif.
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5
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Floro J, Dai A, Metzger A, Mora-Martin A, Ganem N, Cifuentes D, Wu CS, Dalal J, Lyons S, Labadorf A, Flynn R. SDE2 is an essential gene required for ribosome biogenesis and the regulation of alternative splicing. Nucleic Acids Res 2021; 49:9424-9443. [PMID: 34365507 PMCID: PMC8450105 DOI: 10.1093/nar/gkab647] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 07/08/2021] [Accepted: 07/21/2021] [Indexed: 11/22/2022] Open
Abstract
RNA provides the framework for the assembly of some of the most intricate macromolecular complexes within the cell, including the spliceosome and the mature ribosome. The assembly of these complexes relies on the coordinated association of RNA with hundreds of trans-acting protein factors. While some of these trans-acting factors are RNA-binding proteins (RBPs), others are adaptor proteins, and others still, function as both. Defects in the assembly of these complexes results in a number of human pathologies including neurodegeneration and cancer. Here, we demonstrate that Silencing Defective 2 (SDE2) is both an RNA binding protein and also a trans-acting adaptor protein that functions to regulate RNA splicing and ribosome biogenesis. SDE2 depletion leads to widespread changes in alternative splicing, defects in ribosome biogenesis and ultimately complete loss of cell viability. Our data highlight SDE2 as a previously uncharacterized essential gene required for the assembly and maturation of the complexes that carry out two of the most fundamental processes in mammalian cells.
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Affiliation(s)
- Jess Floro
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Anqi Dai
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
- Bioinformatics Program, Boston University, Boston, MA 02118 USA
| | - Abigail Metzger
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Alexandra Mora-Martin
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Neil J Ganem
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Daniel Cifuentes
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Ching-Shyi Wu
- Department and Graduate Institute of Pharmacology, National Taiwan University College of Medicine, Taipei, 10051, Taiwan
| | - Jasbir Dalal
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Shawn M Lyons
- Department of Biochemistry, Boston University School of Medicine, Boston, MA 02118, USA
| | - Adam Labadorf
- Bioinformatics Program, Boston University, Boston, MA 02118 USA
- Department of Neurology, Boston University School of Medicine, Boston, MA 02118 USA
| | - Rachel L Flynn
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
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6
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Signaling Pathways Regulated by UBR Box-Containing E3 Ligases. Int J Mol Sci 2021; 22:ijms22158323. [PMID: 34361089 PMCID: PMC8346999 DOI: 10.3390/ijms22158323] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 12/31/2022] Open
Abstract
UBR box E3 ligases, also called N-recognins, are integral components of the N-degron pathway. Representative N-recognins include UBR1, UBR2, UBR4, and UBR5, and they bind destabilizing N-terminal residues, termed N-degrons. Understanding the molecular bases of their substrate recognition and the biological impact of the clearance of their substrates on cellular signaling pathways can provide valuable insights into the regulation of these pathways. This review provides an overview of the current knowledge of the binding mechanism of UBR box N-recognin/N-degron interactions and their roles in signaling pathways linked to G-protein-coupled receptors, apoptosis, mitochondrial quality control, inflammation, and DNA damage. The targeting of these UBR box N-recognins can provide potential therapies to treat diseases such as cancer and neurodegenerative diseases.
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7
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Thakar T, Moldovan GL. The emerging determinants of replication fork stability. Nucleic Acids Res 2021; 49:7224-7238. [PMID: 33978751 PMCID: PMC8287955 DOI: 10.1093/nar/gkab344] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 04/18/2021] [Accepted: 04/20/2021] [Indexed: 12/21/2022] Open
Abstract
A universal response to replication stress is replication fork reversal, where the nascent complementary DNA strands are annealed to form a protective four-way junction allowing forks to avert DNA damage while replication stress is resolved. However, reversed forks are in turn susceptible to nucleolytic digestion of the regressed nascent DNA arms and rely on dedicated mechanisms to protect their integrity. The most well studied fork protection mechanism involves the BRCA pathway and its ability to catalyze RAD51 nucleofilament formation on the reversed arms of stalled replication forks. Importantly, the inability to prevent the degradation of reversed forks has emerged as a hallmark of BRCA deficiency and underlies genome instability and chemosensitivity in BRCA-deficient cells. In the past decade, multiple factors underlying fork stability have been discovered. These factors either cooperate with the BRCA pathway, operate independently from it to augment fork stability in its absence, or act as enablers of fork degradation. In this review, we examine these novel determinants of fork stability, explore the emergent conceptual underpinnings underlying fork protection, as well as the impact of fork protection on cellular viability and cancer therapy.
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Affiliation(s)
- Tanay Thakar
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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8
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Morgan JJ, Crawford LJ. The Ubiquitin Proteasome System in Genome Stability and Cancer. Cancers (Basel) 2021; 13:2235. [PMID: 34066546 PMCID: PMC8125356 DOI: 10.3390/cancers13092235] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 01/18/2023] Open
Abstract
Faithful DNA replication during cellular division is essential to maintain genome stability and cells have developed a sophisticated network of regulatory systems to ensure its integrity. Disruption of these control mechanisms can lead to loss of genomic stability, a key hallmark of cancer. Ubiquitination is one of the most abundant regulatory post-translational modifications and plays a pivotal role in controlling replication progression, repair of DNA and genome stability. Dysregulation of the ubiquitin proteasome system (UPS) can contribute to the initiation and progression of neoplastic transformation. In this review we provide an overview of the UPS and summarize its involvement in replication and replicative stress, along with DNA damage repair. Finally, we discuss how the UPS presents as an emerging source for novel therapeutic interventions aimed at targeting genomic instability, which could be utilized in the treatment and management of cancer.
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Affiliation(s)
| | - Lisa J. Crawford
- Patrick G Johnston Centre for Cancer Research, Queen’s University Belfast, Belfast BT9 7BL, UK;
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9
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Abstract
The fork protection complex (FPC), comprising the TIMELESS (TIM)-TIPIN heterodimer, acts as a scaffold of the replisome to support seamless DNA replication. We recently showed that SDE2, a PCNA-associated DNA replication stress regulator, maintains the integrity of the FPC, and together with TIM, protects stalled replication forks from nucleolytic degradation.
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Affiliation(s)
- Natalie Lo
- Department of Pharmacological Sciences, The State University of New York at Stony Brook, Stony Brook, NY, USA
| | - Julie Rageul
- Department of Pharmacological Sciences, The State University of New York at Stony Brook, Stony Brook, NY, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, The State University of New York at Stony Brook, Stony Brook, NY, USA.,Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, NY, USA
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10
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Yeh CW, Huang WC, Hsu PH, Yeh KH, Wang LC, Hsu PWC, Lin HC, Chen YN, Chen SC, Yeang CH, Yen HCS. The C-degron pathway eliminates mislocalized proteins and products of deubiquitinating enzymes. EMBO J 2021; 40:e105846. [PMID: 33469951 PMCID: PMC8013793 DOI: 10.15252/embj.2020105846] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 12/11/2020] [Accepted: 12/15/2020] [Indexed: 01/22/2023] Open
Abstract
Protein termini are determinants of protein stability. Proteins bearing degradation signals, or degrons, at their amino‐ or carboxyl‐termini are eliminated by the N‐ or C‐degron pathways, respectively. We aimed to elucidate the function of C‐degron pathways and to unveil how normal proteomes are exempt from C‐degron pathway‐mediated destruction. Our data reveal that C‐degron pathways remove mislocalized cellular proteins and cleavage products of deubiquitinating enzymes. Furthermore, the C‐degron and N‐degron pathways cooperate in protein removal. Proteome analysis revealed a shortfall in normal proteins targeted by C‐degron pathways, but not of defective proteins, suggesting proteolysis‐based immunity as a constraint for protein evolution/selection. Our work highlights the importance of protein termini for protein quality surveillance, and the relationship between the functional proteome and protein degradation pathways.
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Affiliation(s)
- Chi-Wei Yeh
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Wei-Chieh Huang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Pang-Hung Hsu
- Department of Life Science, Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan
| | - Kun-Hai Yeh
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Li-Chin Wang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.,Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, Taiwan
| | | | - Hsiu-Chuan Lin
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.,Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, Taiwan
| | - Yi-Ning Chen
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Shu-Chuan Chen
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Chen-Hsiang Yeang
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, Taiwan.,Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
| | - Hsueh-Chi S Yen
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.,Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, Taiwan
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11
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Rageul J, Park JJ, Zeng PP, Lee EA, Yang J, Hwang S, Lo N, Weinheimer AS, Schärer OD, Yeo JE, Kim H. SDE2 integrates into the TIMELESS-TIPIN complex to protect stalled replication forks. Nat Commun 2020; 11:5495. [PMID: 33127907 PMCID: PMC7603486 DOI: 10.1038/s41467-020-19162-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 09/28/2020] [Indexed: 01/07/2023] Open
Abstract
Protecting replication fork integrity during DNA replication is essential for maintaining genome stability. Here, we report that SDE2, a PCNA-associated protein, plays a key role in maintaining active replication and counteracting replication stress by regulating the replication fork protection complex (FPC). SDE2 directly interacts with the FPC component TIMELESS (TIM) and enhances its stability, thereby aiding TIM localization to replication forks and the coordination of replisome progression. Like TIM deficiency, knockdown of SDE2 leads to impaired fork progression and stalled fork recovery, along with a failure to activate CHK1 phosphorylation. Moreover, loss of SDE2 or TIM results in an excessive MRE11-dependent degradation of reversed forks. Together, our study uncovers an essential role for SDE2 in maintaining genomic integrity by stabilizing the FPC and describes a new role for TIM in protecting stalled replication forks. We propose that TIM-mediated fork protection may represent a way to cooperate with BRCA-dependent fork stabilization. The fork protection complex (FPC), including the proteins TIMELESS and TIPIN, stabilizes the replisome to ensure unperturbed fork progression during DNA replication. Here the authors reveal that that SDE2, a PCNA-associated protein, plays an important role in maintaining active replication and protecting stalled forks by regulating the replication fork protection complex (FPC).
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Affiliation(s)
- Julie Rageul
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Jennifer J Park
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Ping Ping Zeng
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Eun-A Lee
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, 44919, Republic of Korea
| | - Jihyeon Yang
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, 44919, Republic of Korea
| | - Sunyoung Hwang
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, 44919, Republic of Korea
| | - Natalie Lo
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Alexandra S Weinheimer
- Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Orlando D Schärer
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, 44919, Republic of Korea.,Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Jung-Eun Yeo
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, 44919, Republic of Korea.
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA. .,Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, New York, 11794, USA.
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12
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Luo A, Gong Y, Kim H, Chen Y. Proteome dynamics analysis identifies functional roles of SDE2 and hypoxia in DNA damage response in prostate cancer cells. NAR Cancer 2020; 2:zcaa010. [PMID: 32743553 PMCID: PMC7380487 DOI: 10.1093/narcan/zcaa010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/19/2020] [Accepted: 06/08/2020] [Indexed: 12/20/2022] Open
Abstract
Mechanistic understanding of hypoxia-responsive signaling pathways provides important insights into oxygen- and metabolism-dependent cellular phenotypes in diseases. Using SILAC-based quantitative proteomics, we provided a quantitative map identifying over 6300 protein groups in response to hypoxia in prostate cancer cells and identified both canonical and novel cellular networks dynamically regulated under hypoxia. Particularly, we identified SDE2, a DNA stress response modulator, that was significantly downregulated by hypoxia, independent of HIF (hypoxia-inducible factor) transcriptional activity. Mechanistically, hypoxia treatment promoted SDE2 polyubiquitination and degradation. Such regulation is independent of previously identified Arg/N-end rule proteolysis or the ubiquitin E3 ligase, CDT2. Depletion of SDE2 increased cellular sensitivity to DNA damage and inhibited cell proliferation. Interestingly, either SDE2 depletion or hypoxia treatment potentiated DNA damage-induced PCNA (proliferating cell nuclear antigen) monoubiquitination, a key step for translesion DNA synthesis. Furthermore, knockdown of SDE2 desensitized, while overexpression of SDE2 protected the hypoxia-mediated regulation of PCNA monoubiquitination upon DNA damage. Taken together, our quantitative proteomics and biochemical study revealed diverse hypoxia-responsive pathways that strongly associated with prostate cancer tumorigenesis and identified the functional roles of SDE2 and hypoxia in regulating DNA damage-induced PCNA monoubiquitination, suggesting a possible link between hypoxic microenvironment and the activation of error-prone DNA repair pathway in tumor cells.
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Affiliation(s)
- Ang Luo
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota at Twin Cities, Minneapolis, MN 55455, USA
| | - Yao Gong
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota at Twin Cities, Minneapolis, MN 55455, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Yue Chen
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota at Twin Cities, Minneapolis, MN 55455, USA
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13
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Sui X, Pan M, Li YM. Insights into the Design of p97-targeting Small Molecules from Structural Studies on p97 Functional Mechanism. Curr Med Chem 2020; 27:298-316. [PMID: 31584361 DOI: 10.2174/0929867326666191004162411] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 08/24/2019] [Accepted: 08/27/2019] [Indexed: 12/14/2022]
Abstract
p97, also known as valosin-containing protein or CDC48, is a member of the AAA+ protein family that is highly conserved in eukaryotes. It binds to various cofactors in the body to perform its protein-unfolding function and participates in DNA repair, degradation of subcellular membrane proteins, and protein quality control pathways, among other processes. Its malfunction can lead to many diseases, such as inclusion body myopathy, associated with Paget's disease of bone and/or frontotemporal dementia, amyotrophic lateral sclerosis disease, and others. In recent years, many small-molecule inhibitors have been deployed against p97, including bis (diethyldithiocarbamate)- copper and CB-5083, which entered the first phase of clinical tests but failed. One bottleneck in the design of p97 drugs is that its molecular mechanism remains unclear. This paper summarizes recent studies on the molecular mechanisms of p97, which may lead to insight into how the next generation of small molecules targeting p97 can be designed.
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Affiliation(s)
- Xin Sui
- Department of Chemistry, Tsinghua University, Beijing 100086, China
| | - Man Pan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, United States
| | - Yi-Ming Li
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, Anhui 230009, China
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14
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Leboeuf D, Abakumova T, Prikazchikova T, Rhym L, Anderson DG, Zatsepin TS, Piatkov KI. Downregulation of the Arg/N-degron Pathway Sensitizes Cancer Cells to Chemotherapy In Vivo. Mol Ther 2020; 28:1092-1104. [PMID: 32087767 DOI: 10.1016/j.ymthe.2020.01.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 01/16/2020] [Indexed: 02/07/2023] Open
Abstract
The N-degron pathway is an emerging target for anti-tumor therapies, because of its capacity to positively regulate many hallmarks of cancer, including angiogenesis, cell proliferation, motility, and survival. Thus, inhibition of the N-degron pathway offers the potential to be a highly effective anti-cancer treatment. With the use of a small interfering RNA (siRNA)-mediated approach for selective downregulation of the four Arg/N-degron-dependent ubiquitin ligases, UBR1, UBR2, UBR4, and UBR5, we demonstrated decreased cell migration and proliferation and increased spontaneous apoptosis in cancer cells. Chronic treatment with lipid nanoparticles (LNPs) loaded with siRNA in mice efficiently downregulates the expression of UBR-ubiquitin ligases in the liver without any significant toxic effects but engages the immune system and causes inflammation. However, when used in a lower dose, in combination with a chemotherapeutic drug, downregulation of the Arg/N-degron pathway E3 ligases successfully reduced tumor load by decreasing proliferation and increasing apoptosis in a mouse model of hepatocellular carcinoma, while avoiding the inflammatory response. Our study demonstrates that UBR-ubiquitin ligases of the Arg/N-degron pathway are promising targets for the development of improved therapies for many cancer types.
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Affiliation(s)
| | | | | | - Luke Rhym
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA; Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Daniel G Anderson
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA; Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA; Harvard and MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, MA, USA; Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA
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15
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Abstract
Faithful duplication of the genome is critical for the survival of an organism and prevention of malignant transformation. Accurate replication of a large amount of genetic information in a timely manner is one of the most challenging cellular processes and is often perturbed by intrinsic and extrinsic barriers to DNA replication fork progression, a phenomenon referred to as DNA replication stress. Elevated DNA replication stress is a primary source of genomic instability and one of the key hallmarks of cancer. Therefore, targeting DNA replication stress is an emerging concept for cancer therapy. The replication machinery associated with PCNA and other regulatory factors coordinates the synthesis and repair of DNA strands at the replication fork. The dynamic interaction of replication protein complexes with DNA is essential for sensing and responding to various signaling events relevant to DNA replication and damage. Thus, the disruption of the spatiotemporal regulation of protein homeostasis at the replication fork impairs genome integrity, which often involves the deregulation of ubiquitin-mediated proteolytic signaling. Notably, emerging evidence has highlighted the role of the AAA+ATPase VCP/p97 in extracting ubiquitinated protein substrates from the chromatin and facilitating the turnover of genome surveillance factors during DNA replication and repair. Here, we review recent advances in our understanding of chromatin-associated degradation pathways at the replication fork and the implication of these findings for cancer therapy.
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Affiliation(s)
- Julie Rageul
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Alexandra S Weinheimer
- Biochemistry and Structural Biology graduate program, Stony Brook University, New York 11794, USA
| | - Jennifer J Park
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA
| | - Hyungjin Kim
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York, 11794, USA; Stony Brook Cancer Center, Renaissance School of Medicine at Stony Brook University, Stony Brook, New York, 11794, USA.
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