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Ma Z, Sharma R, Rogers AN. Physiological Consequences of Nonsense-Mediated Decay and Its Role in Adaptive Responses. Biomedicines 2024; 12:1110. [PMID: 38791071 PMCID: PMC11117581 DOI: 10.3390/biomedicines12051110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Revised: 04/30/2024] [Accepted: 05/13/2024] [Indexed: 05/26/2024] Open
Abstract
The evolutionarily conserved nonsense-mediated mRNA decay (NMD) pathway is a quality control mechanism that degrades aberrant mRNA containing one or more premature termination codons (PTCs). Recent discoveries indicate that NMD also differentially regulates mRNA from wild-type protein-coding genes despite lacking PTCs. Together with studies showing that NMD is involved in development and adaptive responses that influence health and longevity, these findings point to an expanded role of NMD that adds a new layer of complexity in the post-transcriptional regulation of gene expression. However, the extent of its control, whether different types of NMD play different roles, and the resulting physiological outcomes remain unclear and need further elucidation. Here, we review different branches of NMD and what is known of the physiological outcomes associated with this type of regulation. We identify significant gaps in the understanding of this process and the utility of genetic tools in accelerating progress in this area.
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Affiliation(s)
- Zhengxin Ma
- MDI Biological Laboratory, Bar Harbor, ME 04609, USA
| | - Ratna Sharma
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA;
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2
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Mir DA, Ma Z, Horrocks J, Rogers AN. Stress-induced Eukaryotic Translational Regulatory Mechanisms. ARXIV 2024:arXiv:2405.01664v1. [PMID: 38745702 PMCID: PMC11092689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
The eukaryotic protein synthesis process entails intricate stages governed by diverse mechanisms to tightly regulate translation. Translational regulation during stress is pivotal for maintaining cellular homeostasis, ensuring the accurate expression of essential proteins crucial for survival. This selective translational control mechanism is integral to cellular adaptation and resilience under adverse conditions. This review manuscript explores various mechanisms involved in selective translational regulation, focusing on mRNA-specific and global regulatory processes. Key aspects of translational control include translation initiation, which is often a rate-limiting step, and involves the formation of the eIF4F complex and recruitment of mRNA to ribosomes. Regulation of translation initiation factors, such as eIF4E, eIF4E2, and eIF2, through phosphorylation and interactions with binding proteins, modulates translation efficiency under stress conditions. This review also highlights the control of translation initiation through factors like the eIF4F complex and the ternary complex and also underscores the importance of eIF2α phosphorylation in stress granule formation and cellular stress responses. Additionally, the impact of amino acid deprivation, mTOR signaling, and ribosome biogenesis on translation regulation and cellular adaptation to stress is also discussed. Understanding the intricate mechanisms of translational regulation during stress provides insights into cellular adaptation mechanisms and potential therapeutic targets for various diseases, offering valuable avenues for addressing conditions associated with dysregulated protein synthesis.
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Affiliation(s)
- Dilawar Ahmad Mir
- Kathryn W. Davis Center for Regenerative Biology and Aging, Mount Desert Island Biological Laboratory, Bar Harbor, ME
| | - Zhengxin Ma
- Kathryn W. Davis Center for Regenerative Biology and Aging, Mount Desert Island Biological Laboratory, Bar Harbor, ME
| | - Jordan Horrocks
- Kathryn W. Davis Center for Regenerative Biology and Aging, Mount Desert Island Biological Laboratory, Bar Harbor, ME
| | - Aric N Rogers
- Kathryn W. Davis Center for Regenerative Biology and Aging, Mount Desert Island Biological Laboratory, Bar Harbor, ME
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3
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Guo M, Fang Z, Chen B, Songyang Z, Xiong Y. Distinct dosage compensations of ploidy-sensitive and -insensitive X chromosome genes during development and in diseases. iScience 2023; 26:105997. [PMID: 36798435 PMCID: PMC9926305 DOI: 10.1016/j.isci.2023.105997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 12/12/2022] [Accepted: 01/12/2023] [Indexed: 01/20/2023] Open
Abstract
The active X chromosome in mammals is upregulated to balance its dosage to autosomes during evolution. However, it is elusive why the known dosage compensation machinery showed uneven and small influence on X genes. Here, based on >20,000 transcriptomes, we identified two X gene groups (ploidy-sensitive [PSX] and ploidy-insensitive [PIX]), showing distinct but evolutionarily conserved dosage compensations (termed XAR). We demonstrated that XAR-PIX was downregulated whereas XAR-PSX upregulated at both RNA and protein levels across cancer types, in contrast with their trends during stem cell differentiation. XAR-PIX, but not XAR-PSX, was lower and correlated with autoantibodies and inflammation in patients of lupus, suggesting that insufficient dosage of PIX genes contribute to lupus pathogenesis. We further identified and experimentally validated two XAR regulators, TP53 and ATRX. Collectively, we provided insights into X dosage compensation in mammals and demonstrated different regulation of PSX and PIX and their pathophysiological roles in human diseases.
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Affiliation(s)
- Mengbiao Guo
- Key Laboratory of Gene Engineering of the Ministry of Education, Institute of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Zhengwen Fang
- Key Laboratory of Gene Engineering of the Ministry of Education, Institute of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Bohong Chen
- Key Laboratory of Gene Engineering of the Ministry of Education, Institute of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Zhou Songyang
- Key Laboratory of Gene Engineering of the Ministry of Education, Institute of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yuanyan Xiong
- Key Laboratory of Gene Engineering of the Ministry of Education, Institute of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China,Corresponding author
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4
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Bonczek O, Wang L, Gnanasundram SV, Chen S, Haronikova L, Zavadil-Kokas F, Vojtesek B. DNA and RNA Binding Proteins: From Motifs to Roles in Cancer. Int J Mol Sci 2022; 23:ijms23169329. [PMID: 36012592 PMCID: PMC9408909 DOI: 10.3390/ijms23169329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/15/2022] [Accepted: 08/17/2022] [Indexed: 11/16/2022] Open
Abstract
DNA and RNA binding proteins (DRBPs) are a broad class of molecules that regulate numerous cellular processes across all living organisms, creating intricate dynamic multilevel networks to control nucleotide metabolism and gene expression. These interactions are highly regulated, and dysregulation contributes to the development of a variety of diseases, including cancer. An increasing number of proteins with DNA and/or RNA binding activities have been identified in recent years, and it is important to understand how their activities are related to the molecular mechanisms of cancer. In addition, many of these proteins have overlapping functions, and it is therefore essential to analyze not only the loss of function of individual factors, but also to group abnormalities into specific types of activities in regard to particular cancer types. In this review, we summarize the classes of DNA-binding, RNA-binding, and DRBPs, drawing particular attention to the similarities and differences between these protein classes. We also perform a cross-search analysis of relevant protein databases, together with our own pipeline, to identify DRBPs involved in cancer. We discuss the most common DRBPs and how they are related to specific cancers, reviewing their biochemical, molecular biological, and cellular properties to highlight their functions and potential as targets for treatment.
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Affiliation(s)
- Ondrej Bonczek
- Research Centre for Applied Molecular Oncology (RECAMO), Masaryk Memorial Cancer Institute (MMCI), Zluty Kopec 7, 656 53 Brno, Czech Republic
- Department of Medical Biosciences, Umea University, 90187 Umea, Sweden
- Correspondence: (O.B.); (B.V.)
| | - Lixiao Wang
- Department of Medical Biosciences, Umea University, 90187 Umea, Sweden
| | | | - Sa Chen
- Department of Medical Biosciences, Umea University, 90187 Umea, Sweden
| | - Lucia Haronikova
- Research Centre for Applied Molecular Oncology (RECAMO), Masaryk Memorial Cancer Institute (MMCI), Zluty Kopec 7, 656 53 Brno, Czech Republic
| | - Filip Zavadil-Kokas
- Research Centre for Applied Molecular Oncology (RECAMO), Masaryk Memorial Cancer Institute (MMCI), Zluty Kopec 7, 656 53 Brno, Czech Republic
| | - Borivoj Vojtesek
- Research Centre for Applied Molecular Oncology (RECAMO), Masaryk Memorial Cancer Institute (MMCI), Zluty Kopec 7, 656 53 Brno, Czech Republic
- Correspondence: (O.B.); (B.V.)
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5
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Matuszyk J. MALAT1-miRNAs network regulate thymidylate synthase and affect 5FU-based chemotherapy. Mol Med 2022; 28:89. [PMID: 35922756 PMCID: PMC9351108 DOI: 10.1186/s10020-022-00516-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 07/22/2022] [Indexed: 12/12/2022] Open
Abstract
Background The active metabolite of 5-Fluorouracil (5FU), used in the treatment of several types of cancer, acts by inhibiting the thymidylate synthase encoded by the TYMS gene, which catalyzes the rate-limiting step in DNA replication. The major failure of 5FU-based cancer therapy is the development of drug resistance. High levels of TYMS-encoded protein in cancerous tissues are predictive of poor response to 5FU treatment. Expression of TYMS is regulated by various mechanisms, including involving non-coding RNAs, both miRNAs and long non-coding RNAs (lncRNAs). Aim To delineate the miRNAs and lncRNAs network regulating the level of TYMS-encoded protein. Main body Several miRNAs targeting TYMS mRNA have been identified in colon cancers, the levels of which can be regulated to varying degrees by lncRNAs. Due to their regulation by the MALAT1 lncRNA, these miRNAs can be divided into three groups: (1) miR-197-3p, miR-203a-3p, miR-375-3p which are downregulated by MALAT1 as confirmed experimentally and the levels of these miRNAs are actually reduced in colon and gastric cancers; (2) miR-140-3p, miR-330-3p that could potentially interact with MALAT1, but not yet supported by experimental results; (3) miR-192-5p, miR-215-5p whose seed sequences do not recognize complementary response elements within MALAT1. Considering the putative MALAT1-miRNAs interaction network, attention is drawn to the potential positive feedback loop causing increased expression of MALAT1 in colon cancer and hepatocellular carcinoma, where YAP1 acts as a transcriptional co-factor which, by binding to the TCF4 transcription factor/ β-catenin complex, may increase the activation of the MALAT1 gene whereas the MALAT1 lncRNA can inhibit miR-375-3p which in turn targets YAP1 mRNA. Conclusion The network of non-coding RNAs may reduce the sensitivity of cancer cells to 5FU treatment by upregulating the level of thymidylate synthase.
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Affiliation(s)
- Janusz Matuszyk
- Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, 12 R. Weigla Street, 53-114, Wroclaw, Poland.
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A Novel Role of SMG1 in Cholesterol Homeostasis That Depends Partially on p53 Alternative Splicing. Cancers (Basel) 2022; 14:cancers14133255. [PMID: 35805027 PMCID: PMC9265556 DOI: 10.3390/cancers14133255] [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: 05/31/2022] [Revised: 06/26/2022] [Accepted: 06/29/2022] [Indexed: 12/10/2022] Open
Abstract
Simple Summary p53 isoforms have been reported in various tumor types. Both p53β and p53γ were recently reported to retain functionalities of full-length p53α. A role for p53 and p53 loss in cholesterol metabolism has also emerged. We show that SMG1, a phosphatidylinositol 3-kinase-related kinase, when inhibited in p53 wild-type MCF7 and HepG2 cells, significantly alters the expression of cholesterol pathway genes, with a net increase in intracellular cholesterol and an increased sensitivity to Fatostatin in MCF7. We confirm a prior report that SMG1 inhibition in MCF7 cells promotes expression of p53β and show the first evidence for increases in p53γ. Further, induced p53β expression, confirmed with antibody, explained the loss of SMG1 upregulation of the ABCA1 cholesterol exporter where p53γ had no effect on ABCA1. Additionally, upregulation of ABCA1 upon SMG1 knockdown was independent of upregulation of nonsense-mediated decay target RASSF1C, previously suggested to regulate ABCA1 via a “RASSF1C-miR33a-ABCA1” axis. Abstract SMG1, a phosphatidylinositol 3-kinase-related kinase (PIKK), essential in nonsense-mediated RNA decay (NMD), also regulates p53, including the alternative splicing of p53 isoforms reported to retain p53 functions. We confirm that SMG1 inhibition in MCF7 tumor cells induces p53β and show p53γ increase. Inhibiting SMG1, but not UPF1 (a core factor in NMD), upregulated several cholesterol pathway genes. SMG1 knockdown significantly increased ABCA1, a cholesterol efflux pump shown to be positively regulated by full-length p53 (p53α). An investigation of RASSF1C, an NMD target, increased following SMG1 inhibition and reported to inhibit miR-33a-5p, a canonical ABCA1-inhibiting miRNA, did not explain the ABCA1 results. ABCA1 upregulation following SMG1 knockdown was inhibited by p53β siRNA with greatest inhibition when p53α and p53β were jointly suppressed, while p53γ siRNA had no effect. In contrast, increased expression of MVD, a cholesterol synthesis gene upregulated in p53 deficient backgrounds, was sensitive to combined targeting of p53α and p53γ. Phenotypically, we observed increased intracellular cholesterol and enhanced sensitivity of MCF7 to growth inhibitory effects of cholesterol-lowering Fatostatin following SMG1 inhibition. Our results suggest deregulation of cholesterol pathway genes following SMG1 knockdown may involve alternative p53 programming, possibly resulting from differential effects of p53 isoforms on cholesterol gene expression.
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7
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Ensinck MM, Carlon MS. One Size Does Not Fit All: The Past, Present and Future of Cystic Fibrosis Causal Therapies. Cells 2022; 11:cells11121868. [PMID: 35740997 PMCID: PMC9220995 DOI: 10.3390/cells11121868] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 05/25/2022] [Accepted: 05/28/2022] [Indexed: 02/04/2023] Open
Abstract
Cystic fibrosis (CF) is the most common monogenic disorder, caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Over the last 30 years, tremendous progress has been made in understanding the molecular basis of CF and the development of treatments that target the underlying defects in CF. Currently, a highly effective CFTR modulator treatment (Kalydeco™/Trikafta™) is available for 90% of people with CF. In this review, we will give an extensive overview of past and ongoing efforts in the development of therapies targeting the molecular defects in CF. We will discuss strategies targeting the CFTR protein (i.e., CFTR modulators such as correctors and potentiators), its cellular environment (i.e., proteostasis modulation, stabilization at the plasma membrane), the CFTR mRNA (i.e., amplifiers, nonsense mediated mRNA decay suppressors, translational readthrough inducing drugs) or the CFTR gene (gene therapies). Finally, we will focus on how these efforts can be applied to the 15% of people with CF for whom no causal therapy is available yet.
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Affiliation(s)
- Marjolein M. Ensinck
- Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Flanders, Belgium;
| | - Marianne S. Carlon
- Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Flanders, Belgium;
- Laboratory of Respiratory Diseases and Thoracic Surgery (BREATHE), Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Flanders, Belgium
- Correspondence:
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8
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Kamp JA, Lemmens BBLG, Romeijn RJ, González-Prieto R, Olsen J, Vertegaal ACO, van Schendel R, Tijsterman M. THO complex deficiency impairs DNA double-strand break repair via the RNA surveillance kinase SMG-1. Nucleic Acids Res 2022; 50:6235-6250. [PMID: 35670662 PMCID: PMC9226523 DOI: 10.1093/nar/gkac472] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 05/11/2022] [Accepted: 06/02/2022] [Indexed: 12/25/2022] Open
Abstract
The integrity and proper expression of genomes are safeguarded by DNA and RNA surveillance pathways. While many RNA surveillance factors have additional functions in the nucleus, little is known about the incidence and physiological impact of converging RNA and DNA signals. Here, using genetic screens and genome-wide analyses, we identified unforeseen SMG-1-dependent crosstalk between RNA surveillance and DNA repair in living animals. Defects in RNA processing, due to viable THO complex or PNN-1 mutations, induce a shift in DNA repair in dividing and non-dividing tissues. Loss of SMG-1, an ATM/ATR-like kinase central to RNA surveillance by nonsense-mediated decay (NMD), restores DNA repair and radio-resistance in THO-deficient animals. Mechanistically, we find SMG-1 and its downstream target SMG-2/UPF1, but not NMD per se, to suppress DNA repair by non-homologous end-joining in favour of single strand annealing. We postulate that moonlighting proteins create short-circuits in vivo, allowing aberrant RNA to redirect DNA repair.
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Affiliation(s)
| | | | - Ron J Romeijn
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands
| | - Román González-Prieto
- Department of Cell & Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - Jesper V Olsen
- Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark
| | - Alfred C O Vertegaal
- Department of Cell & Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands
| | - Robin van Schendel
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands
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9
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Matsumoto Y. Development and Evolution of DNA-Dependent Protein Kinase Inhibitors toward Cancer Therapy. Int J Mol Sci 2022; 23:ijms23084264. [PMID: 35457081 PMCID: PMC9032228 DOI: 10.3390/ijms23084264] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/07/2022] [Accepted: 04/09/2022] [Indexed: 12/04/2022] Open
Abstract
DNA double-strand break (DSB) is considered the most deleterious type of DNA damage, which is generated by ionizing radiation (IR) and a subset of anticancer drugs. DNA-dependent protein kinase (DNA-PK), which is composed of a DNA-PK catalytic subunit (DNA-PKcs) and Ku80-Ku70 heterodimer, acts as the molecular sensor for DSB and plays a pivotal role in DSB repair through non-homologous end joining (NHEJ). Cells deficient for DNA-PKcs show hypersensitivity to IR and several DNA-damaging agents. Cellular sensitivity to IR and DNA-damaging agents can be augmented by the inhibition of DNA-PK. A number of small molecules that inhibit DNA-PK have been developed. Here, the development and evolution of inhibitors targeting DNA-PK for cancer therapy is reviewed. Significant parts of the inhibitors were developed based on the structural similarity of DNA-PK to phosphatidylinositol 3-kinases (PI3Ks) and PI3K-related kinases (PIKKs), including Ataxia-telangiectasia mutated (ATM). Some of DNA-PK inhibitors, e.g., NU7026 and NU7441, have been used extensively in the studies for cellular function of DNA-PK. Recently developed inhibitors, e.g., M3814 and AZD7648, are in clinical trials and on the way to be utilized in cancer therapy in combination with radiotherapy and chemotherapy.
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Affiliation(s)
- Yoshihisa Matsumoto
- Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan
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10
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Abstract
Nonsense-mediated mRNA decay (NMD) is an mRNA degradation pathway that eliminates transcripts containing premature termination codons (PTCs). Half-lives of the mRNAs containing PTCs demonstrate that a small percent escape surveillance and do not degrade. It is not known whether this escape represents variable mRNA degradation within cells or, alternatively cells within the population are resistant. Here we demonstrate a single-cell approach with a bi-directional reporter, which expresses two β-globin genes with or without a PTC in the same cell, to characterize the efficiency of NMD in individual cells. We found a broad range of NMD efficiency in the population; some cells degraded essentially all of the mRNAs, while others escaped NMD almost completely. Characterization of NMD efficiency together with NMD regulators in single cells showed cell-to-cell variability of NMD reflects the differential level of surveillance factors, SMG1 and phosphorylated UPF1. A single-cell fluorescent reporter system that enabled detection of NMD using flow cytometry revealed that this escape occurred either by translational readthrough at the PTC or by a failure of mRNA degradation after successful translation termination at the PTC.
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11
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Bamberger C, Pankow S, Yates JR. SMG1 and CDK12 Link ΔNp63α Phosphorylation to RNA Surveillance in Keratinocytes. J Proteome Res 2021; 20:5347-5358. [PMID: 34761935 PMCID: PMC10653645 DOI: 10.1021/acs.jproteome.1c00427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The tumor suppressor p53-like protein p63 is required for self-renewal of epidermal tissues. Loss of p63 or exposure to ultraviolet (UV) irradiation triggers terminal differentiation in keratinocytes. However, it remains unclear how p63 diverts epidermal cells from proliferation to terminal differentiation, thereby contributing to successful tissue self-renewal. Here, we used bottom-up proteomics to identify the proteome at the chromatin in normal human epidermal keratinocytes following UV irradiation and p63 depletion. We found that loss of p63 increased DNA damage and that UV irradiation recruited the cyclin-dependent kinase CDK12 and the serine/threonine protein kinase SMG1 to chromatin only in the presence of p63. A post-translational modification analysis of ΔNp63α with mass spectrometry revealed that phosphorylation of T357/S358 and S368 was dependent on SMG1, whereas CDK12 increased the phosphorylation of ΔNp63α at S66/S68 and S301. Indirect phosphorylation of ΔNp63α in the presence of SMG1 enabled ΔNp63α to bind to the tumor suppressor p53-specific DNA recognition sequence, whereas CDK12 rendered ΔNp63α less responsive to UV irradiation and was not required for specific DNA binding. CDK12 and SMG1 are known to regulate the transcription and splicing of RNAs and the decay of nonsense RNAs, respectively, and a subset of p63-specific protein-protein interactions at the chromatin also linked p63 to RNA transcription and decay. We observed that in the absence of p63, UV irradiation resulted in more ORF1p. ORF1p is the first protein product of the intronless non-LTR retrotransposon LINE-1, indicating a derailed surveillance of RNA processing and/or translation. Our results suggest that p63 phosphorylation and transcriptional activation might correspond to altered RNA processing and/or translation to protect proliferating keratinocytes from increased genotoxic stress.
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Affiliation(s)
- Casimir Bamberger
- Department for Chemical Physiology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
| | - Sandra Pankow
- Department for Chemical Physiology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
| | - John R. Yates
- Department for Chemical Physiology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
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12
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Alemi F, Raei Sadigh A, Malakoti F, Elhaei Y, Ghaffari SH, Maleki M, Asemi Z, Yousefi B, Targhazeh N, Majidinia M. Molecular mechanisms involved in DNA repair in human cancers: An overview of PI3k/Akt signaling and PIKKs crosstalk. J Cell Physiol 2021; 237:313-328. [PMID: 34515349 DOI: 10.1002/jcp.30573] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/17/2021] [Accepted: 08/20/2021] [Indexed: 12/14/2022]
Abstract
The cellular genome is frequently subjected to abundant endogenous and exogenous factors that induce DNA damage. Most of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family members are activated in response to DNA damage and are the most important DNA damage response (DDR) proteins. The DDR system protects the cells against the wrecking effects of these genotoxicants and repairs the DNA damage caused by them. If the DNA damage is severe, such as when DNA is the goal of chemo-radiotherapy, the DDR drives cells toward cell cycle arrest and apoptosis. Some intracellular pathways, such as PI3K/Akt, which is overactivated in most cancers, could stimulate the DDR process and failure of chemo-radiotherapy with the increasing repair of damaged DNA. This signaling pathway induces DNA repair through the regulation of proteins that are involved in DDR like BRCA1, HMGB1, and P53. In this review, we will focus on the crosstalk of the PI3K/Akt and PIKKs involved in DDR and then discuss current achievements in the sensitization of cancer cells to chemo-radiotherapy by PI3K/Akt inhibitors.
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Affiliation(s)
- Forough Alemi
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Aydin Raei Sadigh
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Faezeh Malakoti
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yusuf Elhaei
- Department of Clinical Biochemistry, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Seyed Hamed Ghaffari
- Department of Orthopedics, Shohada Medical Research & Training Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Masomeh Maleki
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Zatollah Asemi
- Research Center for Biochemistry and Nutrition in Metabolic Diseases, Kashan University of Medical Sciences, Kashan, Iran
| | - Bahman Yousefi
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Niloufar Targhazeh
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Maryam Majidinia
- Solid Tumor Research Center, Urmia University of Medical Sciences, Urmia, Iran
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13
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McHugh DR, Cotton CU, Hodges CA. Synergy between Readthrough and Nonsense Mediated Decay Inhibition in a Murine Model of Cystic Fibrosis Nonsense Mutations. Int J Mol Sci 2020; 22:ijms22010344. [PMID: 33396210 PMCID: PMC7794695 DOI: 10.3390/ijms22010344] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 12/17/2020] [Accepted: 12/29/2020] [Indexed: 12/15/2022] Open
Abstract
Many heritable genetic disorders arise from nonsense mutations, which generate premature termination codons (PTCs) in transcribed mRNA. PTCs ablate protein synthesis by prematurely terminating the translation of mutant mRNA, as well as reducing mutant mRNA quantity through targeted degradation by nonsense-mediated decay (NMD) mechanisms. Therapeutic strategies for nonsense mutations include facilitating ribosomal readthrough of the PTC and/or inhibiting NMD to restore protein function. However, the efficacy of combining readthrough agents and NMD inhibitors has not been thoroughly explored. In this study, we examined combinations of known NMD inhibitors and readthrough agents using functional analysis of the CFTR protein in primary cells from a mouse model carrying a G542X nonsense mutation in Cftr. We observed synergy between an inhibitor of the NMD component SMG-1 (SMG1i) and the readthrough agents G418, gentamicin, and paromomycin, but did not observe synergy with readthrough caused by amikacin, tobramycin, PTC124, escin, or amlexanox. These results indicate that treatment with NMD inhibitors can increase the quantity of functional protein following readthrough, and that combining NMD inhibitors and readthrough agents represents a potential therapeutic option for treating nonsense mutations.
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Affiliation(s)
- Daniel R. McHugh
- Department of Genetics and Genome Sciences, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA;
| | - Calvin U. Cotton
- Department of Pediatrics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA;
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA
| | - Craig A. Hodges
- Department of Genetics and Genome Sciences, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA;
- Department of Pediatrics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, USA;
- Correspondence:
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14
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Nonsense-Mediated mRNA Decay: Pathologies and the Potential for Novel Therapeutics. Cancers (Basel) 2020; 12:cancers12030765. [PMID: 32213869 PMCID: PMC7140085 DOI: 10.3390/cancers12030765] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/19/2020] [Accepted: 03/19/2020] [Indexed: 12/22/2022] Open
Abstract
Nonsense-mediated messenger RNA (mRNA) decay (NMD) is a surveillance pathway used by cells to control the quality mRNAs and to fine-tune transcript abundance. NMD plays an important role in cell cycle regulation, cell viability, DNA damage response, while also serving as a barrier to virus infection. Disturbance of this control mechanism caused by genetic mutations or dys-regulation of the NMD pathway can lead to pathologies, including neurological disorders, immune diseases and cancers. The role of NMD in cancer development is complex, acting as both a promoter and a barrier to tumour progression. Cancer cells can exploit NMD for the downregulation of key tumour suppressor genes, or tumours adjust NMD activity to adapt to an aggressive immune microenvironment. The latter case might provide an avenue for therapeutic intervention as NMD inhibition has been shown to lead to the production of neoantigens that stimulate an immune system attack on tumours. For this reason, understanding the biology and co-option pathways of NMD is important for the development of novel therapeutic agents. Inhibitors, whose design can make use of the many structures available for NMD study, will play a crucial role in characterizing and providing diverse therapeutic options for this pathway in cancer and other diseases.
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15
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Han X, Wei Y, Wang H, Wang F, Ju Z, Li T. Nonsense-mediated mRNA decay: a 'nonsense' pathway makes sense in stem cell biology. Nucleic Acids Res 2019; 46:1038-1051. [PMID: 29272451 PMCID: PMC5814811 DOI: 10.1093/nar/gkx1272] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 12/09/2017] [Indexed: 01/04/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a highly conserved post-transcriptional regulatory mechanism of gene expression in eukaryotes. Originally, NMD was identified as an RNA surveillance machinery in degrading 'aberrant' mRNA species with premature termination codons. Recent studies indicate that NMD regulates the stability of natural gene transcripts that play significant roles in cell functions. Although components and action modes of the NMD machinery in degrading its RNA targets have been extensively studied with biochemical and structural approaches, the biological roles of NMD remain to be defined. Stem cells are rare cell populations, which play essential roles in tissue homeostasis and hold great promises in regenerative medicine. Stem cells self-renew to maintain the cellular identity and differentiate into somatic lineages with specialized functions to sustain tissue integrity. Transcriptional regulations and epigenetic modulations have been extensively implicated in stem cell biology. However, post-transcriptional regulatory mechanisms, such as NMD, in stem cell regulation are largely unknown. In this paper, we summarize the recent findings on biological roles of NMD factors in embryonic and tissue-specific stem cells. Furthermore, we discuss the possible mechanisms of NMD in regulating stem cell fates.
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Affiliation(s)
- Xin Han
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Yanling Wei
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Hua Wang
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Feilong Wang
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Zhenyu Ju
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Tangliang Li
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
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16
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Pan C, Issaeva N, Yarbrough WG. HPV-driven oropharyngeal cancer: current knowledge of molecular biology and mechanisms of carcinogenesis. CANCERS OF THE HEAD & NECK 2018; 3:12. [PMID: 31093365 PMCID: PMC6460765 DOI: 10.1186/s41199-018-0039-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/09/2018] [Indexed: 12/21/2022]
Abstract
Understanding of oropharyngeal squamous cell carcinoma has significantly progressed over the last decades, and the concept that this disease can be subdivided into two distinct entities based on human papilloma virus (HPV) status has gained acceptance. To combat the constantly growing epidemic of HPV+ oropharyngeal cancer, further investigation and characterization the unique features of the disease, along with the development and implementation of new, targeted therapies, is crucial. In this review, we summarize the etiology, pathogenesis, diagnosis, treatment, and molecular characteristics of HPV-associated oropharyngeal squamous cell carcinoma.
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Affiliation(s)
- Cassie Pan
- 1Department of Surgery, Division of Otolaryngology, Yale University, New Haven, CT USA
| | - Natalia Issaeva
- 2Department of Otolaryngology/Head and Neck Surgery; Lineberger Cancer Center, University of North Carolina at Chapel Hill, 170 Manning Drive, Campus Box 7070, Chapel Hill, NC 27599 USA
| | - Wendell G Yarbrough
- 2Department of Otolaryngology/Head and Neck Surgery; Lineberger Cancer Center, University of North Carolina at Chapel Hill, 170 Manning Drive, Campus Box 7070, Chapel Hill, NC 27599 USA
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17
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TRRAP is essential for regulating the accumulation of mutant and wild-type p53 in lymphoma. Blood 2018; 131:2789-2802. [PMID: 29653964 DOI: 10.1182/blood-2017-09-806679] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 04/07/2018] [Indexed: 12/26/2022] Open
Abstract
Tumors accumulate high levels of mutant p53 (mutp53), which contributes to mutp53 gain-of-function properties. The mechanisms that underlie such excessive accumulation are not fully understood. To discover regulators of mutp53 protein accumulation, we performed a large-scale RNA interference screen in a Burkitt lymphoma cell line model. We identified transformation/transcription domain-associated protein (TRRAP), a constituent of several histone acetyltransferase complexes, as a critical positive regulator of both mutp53 and wild-type p53 levels. TRRAP silencing attenuated p53 accumulation in lymphoma and colon cancer models, whereas TRRAP overexpression increased mutp53 levels, suggesting a role for TRRAP across cancer entities and p53 mutations. Through clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 screening, we identified a 109-amino-acid region in the N-terminal HEAT repeat region of TRRAP that was crucial for mutp53 stabilization and cell proliferation. Mass spectrometric analysis of the mutp53 interactome indicated that TRRAP silencing caused degradation of mutp53 via the MDM2-proteasome axis. This suggests that TRRAP is vital for maintaining mutp53 levels by shielding it against the natural p53 degradation machinery. To identify drugs that alleviated p53 accumulation similarly to TRRAP silencing, we performed a small-molecule drug screen and found that inhibition of histone deacetylases (HDACs), specifically HDAC1/2/3, decreased p53 levels to a comparable extent. In summary, here we identify TRRAP as a key regulator of p53 levels and link acetylation-modifying complexes to p53 protein stability. Our findings may provide clues for therapeutic targeting of mutp53 in lymphoma and other cancers.
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18
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Resseguie EA, Brookes PS, O’Reilly MA. SMG-1 kinase attenuates mitochondrial ROS production but not cell respiration deficits during hyperoxia. Exp Lung Res 2017; 43:229-239. [PMID: 28749708 PMCID: PMC5956894 DOI: 10.1080/01902148.2017.1339143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 06/02/2017] [Indexed: 12/29/2022]
Abstract
PURPOSE Supplemental oxygen (hyperoxia) used to treat individuals in respiratory distress causes cell injury by enhancing the production of toxic reactive oxygen species (ROS) and inhibiting mitochondrial respiration. The suppressor of morphogenesis of genitalia (SMG-1) kinase is activated during hyperoxia and promotes cell survival by phosphorylating the tumor suppressor p53 on serine 15. Here, we investigate whether SMG-1 and p53 blunt this vicious cycle of progressive ROS production and decline in mitochondrial respiration seen during hyperoxia. MATERIALS AND METHODS Human lung adenocarcinoma A549 and H1299 or colon carcinoma HCT116 cells were depleted of SMG-1, UPF-1, or p53 using RNA interference, and then exposed to room air (21% oxygen) or hyperoxia (95% oxygen). Immunoblotting was used to evaluate protein expression; a Seahorse Bioanalyzer was used to assess cellular respiration; and flow cytometry was used to evaluate fluorescence intensity of cells stained with mitochondrial or redox sensitive dyes. RESULTS Hyperoxia increased mitochondrial and cytoplasmic ROS and suppressed mitochondrial respiration without changing mitochondrial mass or membrane potential. Depletion of SMG-1 or its cofactor, UPF1, significantly enhanced hyperoxia-induced mitochondrial but not cytosolic ROS abundance. They did not affect mitochondrial mass, membrane potential, or hyperoxia-induced deficits in mitochondrial respiration. Genetic depletion of p53 in A549 cells and ablation of the p53 gene in H1299 or HCT116 cells revealed that SMG-1 influences mitochondrial ROS through activation of p53. CONCLUSIONS Our findings show that hyperoxia does not promote a vicious cycle of progressive mitochondrial ROS and dysfunction because SMG-1-p53 signaling attenuates production of mitochondrial ROS without preserving respiration. This suggests antioxidant therapies that blunt ROS production during hyperoxia may not suffice to restore cellular respiration.
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Affiliation(s)
- Emily A. Resseguie
- Department of Environmental Medicine, The University of Rochester, Rochester, New York, USA
| | - Paul S. Brookes
- Department of Anesthesiology, The University of Rochester, Rochester, New York, USA
| | - Michael A. O’Reilly
- Department of Environmental Medicine, The University of Rochester, Rochester, New York, USA
- Department of Pediatrics, The University of Rochester, Rochester, New York, USA
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19
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Zhang Y, Zheng Y, Faheem A, Sun T, Li C, Li Z, Zhao D, Wu C, Liu J. A novel AKT inhibitor, AZD5363, inhibits phosphorylation of AKT downstream molecules, and activates phosphorylation of mTOR and SMG-1 dependent on the liver cancer cell type. Oncol Lett 2016; 11:1685-1692. [PMID: 26998062 PMCID: PMC4774473 DOI: 10.3892/ol.2016.4111] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 12/10/2015] [Indexed: 12/22/2022] Open
Abstract
Due to frequent phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway dysregulation, AKT is typically accepted as a promising anticancer therapeutic target. mTOR, in particular, represents a suitable therapeutic target for hepatocellular carcinoma, whilst suppressor with morphogenetic effect on genitalia family member-1 (SMG-1) is believed to serve a potential tumor suppressor role in human cancer. Despite SMG-1 and mTOR belonging to the same PI3K-related kinase family, the interactions between them are not yet fully understood. In the present study, a novel pyrrolopyrimidine-derived compound, AZD5363, was observed to suppress proliferation in liver cancer Hep-G2 and Huh-7 cells by inhibiting the phosphorylation of downstream molecules in the AKT signal pathway, in a dose- and time-dependent manner. AZD5363 activated the phosphorylation of mTOR, dependent on the liver cancer cell type, as it may have differing effects in various liver cancer cell lines. Additionally, AZD5363 also activated SMG-1 within the same liver cancer cells types, which subsequently activated the phosphorylation of mTOR. In conclusion, the present study indicates that AZD5363 inhibited phosphorylation of AKT downstream molecules, and activated phosphorylation of mTOR and SMG-1, dependent on the liver cancer type.
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Affiliation(s)
- Yuncheng Zhang
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Yuanwen Zheng
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Ali Faheem
- Shandong University School of Medicine, Jinan, Shandong 250021, P.R. China
| | - Tiantong Sun
- Shandong University School of Medicine, Jinan, Shandong 250021, P.R. China
| | - Chunyou Li
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Zhe Li
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Diantang Zhao
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Chao Wu
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
| | - Jun Liu
- Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong 250021, P.R. China
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20
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Abstract
Oxygen is the basic molecule which supports life and it truly is "god's gift to life." Despite its immense importance, research on "oxygen biology" has never received the light of the day and has been limited to physiological and biochemical studies. It seems that in modern day biology, oxygen research is summarized in one word "hypoxia." Scientists have focused on hypoxia-induced transcriptomics and molecular-cellular alterations exclusively in disease models. Interestingly, the potential of oxygen to control the basic principles of biology like homeostatic maintenance, transcription, replication, and protein folding among many others, at the molecular level, has been completely ignored. Here, we present a perspective on the crucial role played by oxygen in regulation of basic biological phenomena. Our conclusion highlights the importance of establishing novel research areas like oxygen biology, as there is great potential in this field for basic science discoveries and clinical benefits to the society.
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21
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Yuan Z, Guo W, Yang J, Li L, Wang M, Lei Y, Wan Y, Zhao X, Luo N, Cheng P, Liu X, Nie C, Peng Y, Tong A, Wei Y. PNAS-4, an Early DNA Damage Response Gene, Induces S Phase Arrest and Apoptosis by Activating Checkpoint Kinases in Lung Cancer Cells. J Biol Chem 2015; 290:14927-44. [PMID: 25918161 DOI: 10.1074/jbc.m115.658419] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Indexed: 02/05/2023] Open
Abstract
PNAS-4, a novel pro-apoptotic gene, was activated during the early response to DNA damage. Our previous study has shown that PNAS-4 induces S phase arrest and apoptosis when overexpressed in A549 lung cancer cells. However, the underlying action mechanism remains far from clear. In this work, we found that PNAS-4 expression in lung tumor tissues is significantly lower than that in adjacent lung tissues; its expression is significantly increased in A549 cells after exposure to cisplatin, methyl methane sulfonate, and mitomycin; and its overexpression induces S phase arrest and apoptosis in A549 (p53 WT), NCI-H460 (p53 WT), H526 (p53 mutation), and Calu-1 (p53(-/-)) lung cancer cells, leading to proliferation inhibition irrespective of their p53 status. The S phase arrest is associated with up-regulation of p21(Waf1/Cip1) and inhibition of the Cdc25A-CDK2-cyclin E/A pathway. Up-regulation of p21(Waf1/Cip1) is p53-independent and correlates with activation of ERK. We further showed that the intra-S phase checkpoint, which occurs via DNA-dependent protein kinase-mediated activation of Chk1 and Chk2, is involved in the S phase arrest and apoptosis. Gene silencing of Chk1/2 rescues, whereas that of ATM or ATR does not affect, S phase arrest and apoptosis. Furthermore, human PNAS-4 induces DNA breaks in comet assays and γ-H2AX staining. Intriguingly, caspase-dependent cleavage of Chk1 has an additional role in enhancing apoptosis. Taken together, our findings suggest a novel mechanism by which elevated PNAS-4 first causes DNA-dependent protein kinase-mediated Chk1/2 activation and then results in inhibition of the Cdc25A-CDK2-cyclin E/A pathway, ultimately causing S phase arrest and apoptosis in lung cancer cells.
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Affiliation(s)
- Zhu Yuan
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China,
| | - Wenhao Guo
- the Department of Abdominal Oncology, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, No. 37, Guoxue Road, Chengdu 610041, Sichuan Province, China, and
| | - Jun Yang
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Lei Li
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Meiliang Wang
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Yi Lei
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Yang Wan
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Xinyu Zhao
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Na Luo
- the Nankai University School of Medicine/Collaborative Innovation Center of Biotherapy, Tianjin 300071, China
| | - Ping Cheng
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Xinyu Liu
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Chunlai Nie
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Yong Peng
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
| | - Aiping Tong
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China,
| | - Yuquan Wei
- From the State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, 17 People's South Road, Chengdu 610041, China
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22
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Du Y, Lu F, Li P, Ye J, Ji M, Ma D, Ji C. SMG1 acts as a novel potential tumor suppressor with epigenetic inactivation in acute myeloid leukemia. Int J Mol Sci 2014; 15:17065-76. [PMID: 25257528 PMCID: PMC4200422 DOI: 10.3390/ijms150917065] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 09/16/2014] [Accepted: 09/18/2014] [Indexed: 11/30/2022] Open
Abstract
Suppressor with morphogenetic effect on genitalia family member (SMG1) belongs to a family of phosphoinositide 3-kinase-related kinases and is the main kinase involved in nonsense-mediated mRNA decay. Recently, SMG1 was suggested as a novel potential tumor suppressor gene, particularly in hypoxic tumors. To investigate the function of SMG1 in acute myeloid leukemia (AML), we performed methylation-specific polymerase chain reaction and found that SMG1 was hypermethylated in the promoter region. SMG1 hypermethylation was found in 66% (33/50) of AML samples compared with none (0/14) of the normal controls. SMG1 mRNA was down-regulated in AML patients with hypermethylation status whereas it was readily expressed in patients without methylation. Moreover, treatment of AML cells with demethylating agent 5-aza-2'-deoxycytidine (decitabine) inhibited AML cell growth and induced apoptosis by reversing SMG1 methylation status and restoring SMG1 expression. On the other hand, knockdown of SMG1 by RNA interference inhibited apoptosis. We also found that mTOR expression level was negatively correlated to SMG1 expression in AML patients which indicated that SMG1 and mTOR maybe act antagonistically to regulate AML cell growth. In conclusion, our results indicate that SMG1 acts as a potential tumor suppressor with epigenetic regulation in AML.
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MESH Headings
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Apoptosis
- Azacitidine/analogs & derivatives
- Azacitidine/pharmacology
- Bone Marrow/metabolism
- Cell Line, Tumor
- DNA Methylation/drug effects
- DNA, Neoplasm/genetics
- Decitabine
- Down-Regulation
- Female
- Gene Expression Regulation, Leukemic/drug effects
- Gene Expression Regulation, Leukemic/genetics
- Gene Expression Regulation, Leukemic/physiology
- Humans
- Leukemia, Myeloid, Acute/genetics
- Leukemia, Myeloid, Acute/metabolism
- Leukemia, Myelomonocytic, Acute/genetics
- Leukemia, Myelomonocytic, Acute/metabolism
- Male
- Middle Aged
- Neoplasm Proteins/genetics
- Neoplasm Proteins/physiology
- Phosphatidylinositol 3-Kinases/genetics
- Phosphatidylinositol 3-Kinases/physiology
- Promoter Regions, Genetic
- Protein Serine-Threonine Kinases
- RNA Interference
- RNA, Messenger/biosynthesis
- RNA, Neoplasm/biosynthesis
- TOR Serine-Threonine Kinases/physiology
- Tumor Suppressor Proteins/genetics
- Tumor Suppressor Proteins/physiology
- Young Adult
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Affiliation(s)
- Yahui Du
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Fei Lu
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Peng Li
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Jingjing Ye
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Min Ji
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Daoxin Ma
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
| | - Chunyan Ji
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China.
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23
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Cho H, Han S, Park OH, Kim YK. SMG1 regulates adipogenesis via targeting of staufen1-mediated mRNA decay. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:1276-87. [DOI: 10.1016/j.bbagrm.2013.10.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 10/23/2013] [Accepted: 10/25/2013] [Indexed: 12/21/2022]
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24
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SMG1 identified as a regulator of Parkinson's disease-associated alpha-synuclein through siRNA screening. PLoS One 2013; 8:e77711. [PMID: 24204929 PMCID: PMC3813773 DOI: 10.1371/journal.pone.0077711] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/12/2013] [Indexed: 12/15/2022] Open
Abstract
Synucleinopathies are a broad class of neurodegenerative disorders characterized by the presence of intracellular protein aggregates containing α-synuclein protein. The aggregated α-synuclein protein is hyperphosphorylated on serine 129 (S129) compared to the unaggregated form of the protein. While the precise functional consequences of S129 hyperphosphorylation are still being clarified, numerous in vitro and in vivo studies suggest that S129 phosphorylation is an early event in α-synuclein dysfunction and aggregation. Identifying the kinases and phosphatases that regulate this critical phosphorylation event may ultimately prove beneficial by allowing pharmacological mitigation of synuclein dysfunction and toxicity in Parkinson’s disease and other synucleinopathies. We report here the development of a high-content, fluorescence-based assay to quantitate levels of total and S129 phosphorylated α-synuclein protein. We have applied this assay to conduct high-throughput loss-of-function screens with siRNA libraries targeting 711 known and predicted human kinases and 206 phosphatases. Specifically, knockdown of the phosphatidylinositol 3-kinase related kinase SMG1 resulted in significant increases in the expression of pS129 phosphorylated α-synuclein (p-syn). Moreover, SMG1 protein levels were significantly reduced in brain regions with high p-syn levels in both dementia with Lewy bodies (DLB) and Parkinson’s disease with dementia (PDD). These findings suggest that SMG1 may play an important role in increased α-synuclein pathology during the course of PDD, DLB, and possibly other synucleinopathies.
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25
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Gubanova E, Issaeva N, Gokturk C, Djureinovic T, Helleday T. SMG-1 suppresses CDK2 and tumor growth by regulating both the p53 and Cdc25A signaling pathways. Cell Cycle 2013; 12:3770-80. [PMID: 24107632 DOI: 10.4161/cc.26660] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The DNA damage response is coordinated by phosphatidylinositol 3-kinase-related kinases, ATM, ATR, and DNA-PK. SMG-1 is the least studied stress-responsive member of this family. Here, we show that SMG-1 regulates the G 1/S checkpoint through both a p53-dependent, and a p53-independent pathway. We identify Cdc25A as a new SMG-1 substrate, and show that cells depleted of SMG-1 exhibit prolonged Cdc25A stability, failing to inactivate CDK2 in response to radiation. Given an increased tumor growth following depletion of SMG-1, our data demonstrate a novel role for SMG-1 in regulating Cdc25A and suppressing oncogenic CDK2 driven proliferation, confirming SMG-1 as a tumor suppressor.
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Affiliation(s)
- Evgenia Gubanova
- Department of Molecular Biosciences; The Wenner-Gren Institute; Stockholm University; Stockholm, Sweden; Science for Life Laboratory; Division of Translational Medicine and Chemical Biology; Department of Medical Biochemistry and Biophysics; Karolinska Institute; Stockholm, Sweden
| | - Natalia Issaeva
- Department of Surgery, Otolaryngology; Yale University; New Haven, CT USA; Cancer Center; Yale University, New Haven, CT USA
| | - Camilla Gokturk
- Science for Life Laboratory; Division of Translational Medicine and Chemical Biology; Department of Medical Biochemistry and Biophysics; Karolinska Institute; Stockholm, Sweden
| | - Tatjana Djureinovic
- Department of Molecular Biosciences; The Wenner-Gren Institute; Stockholm University; Stockholm, Sweden
| | - Thomas Helleday
- Science for Life Laboratory; Division of Translational Medicine and Chemical Biology; Department of Medical Biochemistry and Biophysics; Karolinska Institute; Stockholm, Sweden
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26
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Kostareli E, Holzinger D, Bogatyrova O, Hielscher T, Wichmann G, Keck M, Lahrmann B, Grabe N, Flechtenmacher C, Schmidt CR, Seiwert T, Dyckhoff G, Dietz A, Höfler D, Pawlita M, Benner A, Bosch FX, Plinkert P, Plass C, Weichenhan D, Hess J. HPV-related methylation signature predicts survival in oropharyngeal squamous cell carcinomas. J Clin Invest 2013; 123:2488-501. [PMID: 23635773 DOI: 10.1172/jci67010] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 02/22/2013] [Indexed: 01/30/2023] Open
Abstract
High-risk types of human papilloma virus (HPV) are increasingly associated with oropharyngeal squamous cell carcinoma (OPSCC). Strikingly, patients with HPV-positive OPSCC are highly curable with ionizing radiation and have better survival compared with HPV-negative patients, but the underlying molecular mechanisms remain poorly understood. We applied an array-based approach to monitor global changes in CpG island hypermethylation between HPV-negative and HPV-positive OPSCCs and identified a specific pattern of differentially methylated regions that critically depends on the presence of viral transcripts. HPV-related alterations were confirmed for the majority of candidate gene promoters by mass spectrometric, quantitative methylation analysis. There was a significant inverse correlation between promoter hypermethylation of ALDH1A2, OSR2, GATA4, GRIA4, and IRX4 and transcript levels. Interestingly, Kaplan-Meier analysis revealed that a combined promoter methylation pattern of low methylation levels in ALDH1A2 and OSR2 promoters and high methylation levels in GATA4, GRIA4, and IRX4 promoters was significantly correlated with improved survival in 3 independent patient cohorts. ALDH1A2 protein levels, determined by immunohistochemistry on tissue microarrays, confirmed the association with clinical outcome. In summary, our study highlights specific alterations in global gene promoter methylation in HPV-driven OPSCCs and identifies a signature that predicts the clinical outcome in OPSCCs.
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Affiliation(s)
- Efterpi Kostareli
- Department of Otolaryngology, Head and Neck Surgery, University Hospital Heidelberg, Heidelberg, Germany
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Karam R, Wengrod J, Gardner LB, Wilkinson MF. Regulation of nonsense-mediated mRNA decay: implications for physiology and disease. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:624-33. [PMID: 23500037 DOI: 10.1016/j.bbagrm.2013.03.002] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 03/02/2013] [Accepted: 03/04/2013] [Indexed: 01/24/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is an mRNA quality control mechanism that destabilizes aberrant mRNAs harboring premature termination (nonsense) codons (PTCs). Recent studies have shown that NMD also targets mRNAs transcribed from a large subset of wild-type genes. This raises the possibility that NMD itself is under regulatory control. Indeed, several recent studies have shown that NMD activity is modulated in specific cell types and that key components of the NMD pathway are regulated by several pathways, including microRNA circuits and NMD itself. Cellular stress also modulates the magnitude of NMD by mechanisms that are beginning to be understood. Here, we review the evidence that NMD is regulated and discuss the physiological role for this regulation. We propose that the efficiency of NMD is altered in some cellular contexts to regulate normal biological events. In disease states-such as in cancer-NMD is disturbed by intrinsic and extrinsic factors, resulting in altered levels of crucial NMD-targeted mRNAs that lead to downstream pathological consequences. This article is part of a Special Issue entitled: RNA Decay mechanisms.
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Affiliation(s)
- Rachid Karam
- Department of Reproductive Medicine, University of California, San Diego, CA 92093-0864, USA
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Sadeque A, Serão NV, Southey BR, Delfino KR, Rodriguez-Zas SL. Identification and characterization of alternative exon usage linked glioblastoma multiforme survival. BMC Med Genomics 2012. [PMID: 23206951 PMCID: PMC3548711 DOI: 10.1186/1755-8794-5-59] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Background Alternative exon usage (AEU) is an important component of gene regulation. Exon expression platforms allow the detection of associations between AEU and phenotypes such as cancer. Numerous studies have identified associations between gene expression and the brain cancer glioblastoma multiforme (GBM). The few consistent gene expression biomarkers of GBM that have been reported may be due to the limited consideration of AEU and the analytical approaches used. The objectives of this study were to develop a model that accounts for the variations in expression present between the exons within a gene and to identify AEU biomarkers of GBM survival. Methods The expression of exons corresponding to 25,403 genes was related to the survival of 250 individuals diagnosed with GBM in a training data set. Genes exhibiting AEU in the training data set were confirmed in an independent validation data set of 78 patients. A hierarchical mixed model that allows the consideration of covariation between exons within a gene and of the effect of the epidemiological characteristics of the patients was developed to identify associations between exon expression and patient survival. This general model describes all three possible scenarios: multi-exon genes with and without AEU, and single-exon genes. Results AEU associated with GBM survival was identified on 2477 genes (P-value < 5.0E-04 or FDR-adjusted P-value < 0.05). G-protein coupled receptor 98 (Gpr98) and epidermal growth factor (Egf) were among the genes exhibiting AEU with 30 and 9 exons associated with GBM survival, respectively. Pathways enriched among the AEU genes included focal adhesion, ECM-receptor interaction, ABC transporters and pathways in cancer. In addition, 24 multi-exon genes without AEU and 8 single-exon genes were associated with GBM survival (FDR-adjusted P-value < 0.05). Conclusions The inferred patterns of AEU were consistent with in silico AS models. The hierarchical model used offered a flexible and simple way to interpret and identify associations between survival that accommodates multi-exon genes with or without AEU and single exon genes. Our results indicate that differential expression of AEU could be used as biomarker for GBM and potentially other cancers.
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Affiliation(s)
- Ahmed Sadeque
- Department of Animal Sciences, University of Illinois Urbana-Champaign, Urbana, IL, USA
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Gopalsamy A, Bennett EM, Shi M, Zhang WG, Bard J, Yu K. Identification of pyrimidine derivatives as hSMG-1 inhibitors. Bioorg Med Chem Lett 2012; 22:6636-41. [PMID: 23021994 DOI: 10.1016/j.bmcl.2012.08.107] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/23/2012] [Accepted: 08/28/2012] [Indexed: 10/27/2022]
Abstract
hSMG-1 kinase plays a dual role in a highly conserved RNA surveillance pathway termed nonsense-mediated RNA decay (NMD) and in cellular genotoxic stress response. Since deregulation of cellular responses to stress contributes to tumor growth and resistance to chemotherapy, hSMG-1 is a potential target for cancer treatment. From our screening efforts, we have identified pyrimidine derivatives as hSMG-1 kinase inhibitors. We report structure-based optimization of this pan-kinase scaffold to improve its biochemical profile and overall kinome selectivity, including mTOR and CDK, to generate the first reported selective hSMG-1 tool compound.
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Affiliation(s)
- Ariamala Gopalsamy
- Worldwide Medicinal Chemistry, Pfizer, 200 Cambridgepark Drive, Cambridge, MA 02140, USA.
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Kostareli E, Holzinger D, Hess J. New Concepts for Translational Head and Neck Oncology: Lessons from HPV-Related Oropharyngeal Squamous Cell Carcinomas. Front Oncol 2012; 2:36. [PMID: 22655271 PMCID: PMC3356125 DOI: 10.3389/fonc.2012.00036] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 03/27/2012] [Indexed: 12/31/2022] Open
Abstract
Human papillomavirus (HPV) infection is well established as an etiological agent responsible for a number of pathologies affecting the stratified epithelia of skin and anogenital sites. More recently, the infection by (mucosal) high-risk HPV types has also been found to be causally associated with squamous cell carcinoma in the head and neck region (HNSCC), especially in the oropharynx. Intriguingly, HPV-related oropharyngeal squamous cell carcinomas (OPSCC) represent a distinct clinical entity compared to HPV-negative tumors with particular regard to treatment–response and survival outcome. The association between HPV infection and OPSCC may therefore have important implications for the prevention and/or treatment of OPSCC. The improved survival of patients with HPV-related tumors also raises the question, as to whether a better understanding of the underlying differences may help to identify new therapeutic concepts that could be used in targeted therapy for HPV-negative and improved therapy for HPV-positive cancers. This review summarizes the most recent advances in our understanding of the molecular principles of HPV-related OPSCC, mainly based on functional genomic approaches, but also emphasizes the significant role played by the tumor microenvironment, especially the immune system, for improved clinical outcome and differential sensitivity of HPV-related tumors to current treatment options.
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Affiliation(s)
- Efterpi Kostareli
- Department of Otolaryngology, Head and Neck Surgery, Research Group Experimental Head and Neck Oncology, University Hospital Heidelberg Heidelberg, Germany
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Gubanova E, Brown B, Ivanov SV, Helleday T, Mills GB, Yarbrough WG, Issaeva N. Downregulation of SMG-1 in HPV-positive head and neck squamous cell carcinoma due to promoter hypermethylation correlates with improved survival. Clin Cancer Res 2012; 18:1257-67. [PMID: 22247495 DOI: 10.1158/1078-0432.ccr-11-2058] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE Human papillomavirus (HPV) is linked with a subset of head and neck squamous cell carcinomas (HNSCC). HPV-positive HNSCCs show a better prognosis than HPV-negative HNSCCs, which may be explained by sensitivity of the HPV-positive HNSCCs to ionizing radiation (IR). Although the molecular mechanism behind sensitivity to IR in HPV-positive HNSCCs is unresolved, DNA damage response (DDR) might be a significant determinant of IR sensitivity. An important player in the DDR, SMG-1 (suppressor with morphogenetic effect on genitalia), is a potential tumor suppressor and may therefore be deregulated in cancer. No studies have yet been conducted linking defects in SMG-1 expression with cancer. We investigated whether deregulation of SMG-1 could be responsible for defects in the DDR in oropharyngeal HNSCC. EXPERIMENTAL DESIGN Expression and promoter methylation status of SMG-1 were investigated in HNSCCs. To identify a functional link between HPV infection and SMG-1, we transfected the HPV-negative cells with an E6/E7 expression construct. SMG-1 short hairpin RNAs were expressed in HPV-negative cells to estimate survival upon IR. RESULTS Forced E6/E7 expression in HPV-negative cells resulted in SMG-1 promoter hypermethylation and decreased SMG-1 expression. Due to promoter hypermethylation, HPV-positive HNSCC cells and tumors express SMG-1 at lower levels than HPV-negative SCCs. Depletion of SMG-1 in HPV-negative HNSCC cells resulted in increased radiation sensitivity, whereas SMG-1 overexpression protected HPV-positive tumor cells from irradiation. CONCLUSIONS Levels of SMG-1 expression negatively correlated with HPV status in cancer cell lines and tumors. Diminished SMG-1 expression may contribute to the enhanced response to therapy exhibited by HPV-positive HNSCCs.
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Affiliation(s)
- Evgenia Gubanova
- Department of Genetics, Microbiology and Toxicology, Stockholm University, Stockholm, Sweden
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Abstract
hSMG-1 is a member of the phosphoinositide 3 kinase-like kinase (PIKK) family with established roles in nonsense-mediated decay (NMD) of mRNA containing premature termination codons and in genotoxic stress responses to DNA damage. We report here a novel role for hSMG-1 in cytoplasmic stress granule (SG) formation. Exposure of cells to stress causing agents led to the localization of hSMG-1 to SG, identified by colocalization with TIA-1, G3BP1, and eIF4G. hSMG-1 small interfering RNA and the PIKK inhibitor wortmannin prevented formation of a subset of SG, while specific inhibitors of ATM, DNA-PK(cs), or mTOR had no effect. Exposure of cells to H(2)O(2) and sodium arsenite induced (S/T)Q phosphorylation of proteins. While Upf2 and Upf1, an essential substrate for hSMG-1 in NMD, were present in SG, NMD-specific Upf1 phosphorylation was not detected in SG, indicating hSMG-1's role in SG is separate from classical NMD. Thus, SG formation appears more complex than originally envisaged and hSMG-1 plays a central role in this process.
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