1
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Idiiatullina E, Al-Azab M, Lin M, Hrovat-Schaale K, Liu Z, Li X, Guo C, Chen X, Li Y, Gao S, Cui J, Zhou W, Liu L, Zhang Y, Masters SL. Heterozygous de novo dominant negative mutation of REXO2 results in interferonopathy. Nat Commun 2024; 15:6685. [PMID: 39107301 PMCID: PMC11303720 DOI: 10.1038/s41467-024-50878-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Accepted: 07/22/2024] [Indexed: 08/10/2024] Open
Abstract
Mitochondrial RNA (mtRNA) in the cytosol can trigger the innate immune sensor MDA5, and autoinflammatory disease due to type I IFN. Here, we show that a dominant negative mutation in the gene encoding the mitochondrial exonuclease REXO2 may cause interferonopathy by triggering the MDA5 pathway. A patient characterized by this heterozygous de novo mutation (p.T132A) presented with persistent skin rash featuring hyperkeratosis, parakeratosis and acanthosis, with infiltration of lymphocytes and eosinophils around small blood vessels. In addition, circulating IgE levels and inflammatory cytokines, including IFNα, are found consistently elevated. Transcriptional analysis highlights a type I IFN gene signature in PBMC. Mechanistically, REXO2 (T132A) lacks the ability to cleave RNA and inhibits the activity of wild-type REXO2. This leads to an accumulation of mitochondrial dsRNA in the cytosol, which is recognized by MDA5, leading to the associated type I IFN gene signature. These results demonstrate that in the absence of appropriate regulation by REXO2, aberrant cellular nucleic acids may accumulate and continuously trigger innate sensors, resulting in an inborn error of immunity.
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Affiliation(s)
- Elina Idiiatullina
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
- Department of Therapy and Nursing, Bashkir State Medical University, Ufa, Russia
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School, Newark, USA
| | - Mahmoud Al-Azab
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
- Department of Medical Microbiology, Faculty of Medicine, University of Science and Technology, Aden, Yemen
| | - Meng Lin
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Katja Hrovat-Schaale
- Department of Therapy and Nursing, Bashkir State Medical University, Ufa, Russia
- Department of Medical Microbiology, Faculty of Medicine, University of Science and Technology, Aden, Yemen
| | - Ziyang Liu
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Xiaotian Li
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Caiqin Guo
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Xixi Chen
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Yaoying Li
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Song Gao
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Jun Cui
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Wenhao Zhou
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China
| | - Li Liu
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China.
| | - Yuxia Zhang
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China.
| | - Seth L Masters
- Department of Genetics and Endocrinology, Guangzhou Institute of Paediatrics, Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangzhou, China.
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
- Department of Medical Biology, The University of Melbourne, Parkville, Australia.
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia.
- Department of Molecular and Translational Science, Monash University, Clayton, VIC, Australia.
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2
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Zhang T, Zhang R, Zhang Z, Li D, Guo X, Zhang Z, Zhu X, Tan S. REXO2 up-regulation is positively correlated with poor prognosis and tumor immune infiltration in hepatocellular carcinoma. Int Immunopharmacol 2024; 130:111740. [PMID: 38401464 DOI: 10.1016/j.intimp.2024.111740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/18/2024] [Accepted: 02/19/2024] [Indexed: 02/26/2024]
Abstract
BACKGROUND As a homologous counterpart to the prokaryotic oligonuclease found in the cellular cytoplasm and mitochondrion, REXO2 assumes a pivotal role in the maintenance of mitochondrial homeostasis. Nevertheless, the precise functions and mechanisms by which REXO2 operates within the context of hepatocellular carcinoma (HCC) have hitherto remained unexamined. METHODS The expression levels of REXO2 in HCC tissues were evaluated through the utilization of the immunohistochemical (IHC) method, and subsequently, the association between REXO2 expression and the clinicopathological characteristics of HCC patients was scrutinized employing the χ2 test. A battery of experimental assays, encompassing CCK8 viability assessment, cell colony formation, wound healing, and transwell assays, were conducted with the aim of elucidating the biological role of REXO2 within HCC cells. Complementary bioinformatics analyses were undertaken to discern potential correlations between REXO2 and immune infiltration in tumor tissues. RESULTS Our IHC findings have unveiled a notable up-regulation of REXO2 within HCC tissues, and this heightened expression bears the status of an independent prognostic factor, portending an adverse outcome for HCC patients (P < 0.05). Upon the attenuation of REXO2 expression, a discernible reduction in the rates of proliferation, invasion and migration of HCC cells ensued (P < 0.05). Furthermore, transcriptome sequencing analysis has provided insights into the putative influence of REXO2 on the development of HCC through the modulation of TNF and NF-κB signaling pathways. Additionally, our bioinformatics analyses have demonstrated a positive correlation between REXO2 and tumor immune cell infiltration, as well as immune checkpoint CTLA-4. CONCLUSIONS In summation, our results posit an association between the up-regulation of REXO2 and adverse prognostic outcomes, alongside the involvement of immune-related signaling pathways and tumor immune infiltration within the realm of HCC.
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Affiliation(s)
- Tianmiao Zhang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Rongcheng Zhang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Zhongqi Zhang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Di Li
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Xuefeng Guo
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Zhengbao Zhang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China
| | - Xiaonian Zhu
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China.
| | - Shengkui Tan
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi, China; Youjiang Medical University for Nationalities, Baise 533000, Guangxi, China.
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3
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Badhwar P, Khan SH, Taneja B. Three-dimensional structure of a mycobacterial oligoribonuclease reveals a unique C-terminal tail that stabilizes the homodimer. J Biol Chem 2022; 298:102595. [PMID: 36244449 PMCID: PMC9676404 DOI: 10.1016/j.jbc.2022.102595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 10/01/2022] [Accepted: 10/11/2022] [Indexed: 11/06/2022] Open
Abstract
Oligoribonucleases (Orns) are highly conserved DnaQ-fold 3'-5' exoribonucleases that have been found to carry out the last step of cyclic-di-GMP (c-di-GMP) degradation, that is, pGpG to GMP in several bacteria. Removal of pGpG is critical for c-di-GMP homeostasis, as excess uncleaved pGpG can have feedback inhibition on phosphodiesterases, thereby perturbing cellular signaling pathways regulated by c-di-GMP. Perturbation of c-di-GMP levels not only affects survival under hypoxic, reductive stress, or nutrient-limiting conditions but also affects pathogenicity in infection models as well as antibiotic response in mycobacteria. Here, we have determined the crystal structure of MSMEG_4724, the Orn of Mycobacterium smegmatis (Ms_orn) to 1.87 Å resolution to investigate the function of its extended C-terminal tail that is unique among bacterial Orns. Ms_orn is a homodimer with the canonical RNase-H fold of exoribonucleases and conserved catalytic residues in the active site. Further examination of the substrate-binding site with a modeled pGpG emphasized the role of a phosphate cap and "3'OH cap" in constricting a 2-mer substrate in the active site. The unique C-terminal tail of Ms_orn aids dimerization by forming a handshake-like flap over the second protomer of the dimer. Our thermal and denaturant-induced unfolding experiments suggest that it helps in higher stability of Ms_orn as compared with Escherichia coli Orn or a C-terminal deletion mutant. We also show that the C-terminal tail is required for modulating response to stress agents in vivo. These results will help in further evaluating the role of signaling and regulation by c-di-GMP in mycobacteria.
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Affiliation(s)
- Pooja Badhwar
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Sabab Hasan Khan
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi, India
| | - Bhupesh Taneja
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India,For correspondence: Bhupesh Taneja
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4
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Lee VT, Sondermann H, Winkler WC. Nano-RNases: oligo- or dinucleases? FEMS Microbiol Rev 2022; 46:6677394. [PMID: 36026528 PMCID: PMC9779919 DOI: 10.1093/femsre/fuac038] [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: 09/23/2021] [Revised: 07/28/2022] [Accepted: 08/24/2022] [Indexed: 01/07/2023] Open
Abstract
Diribonucleotides arise from two sources: turnover of RNA transcripts (rRNA, tRNA, mRNA, and others) and linearization of cyclic-di-nucleotide signaling molecules. In both cases, there appears to be a requirement for a dedicated set of enzymes that will cleave these diribonucleotides into mononucleotides. The first enzyme discovered to mediate this activity is oligoribonuclease (Orn) from Escherichia coli. In addition to being the enzyme that cleaves dinucleotides and potentially other short oligoribonucleotides, Orn is also the only known exoribonuclease enzyme that is essential for E. coli, suggesting that removal of the shortest RNAs is an essential cellular function. Organisms naturally lacking the orn gene encode other nanoRNases (nrn) that can complement the conditional E. coli orn mutant. This review covers the history and recent advances in our understanding of these enzymes and their substrates. In particular, we focus on (i) the sources of diribonucleotides; (ii) the discovery of exoribonucleases; (iii) the structural features of Orn, NrnA/NrnB, and NrnC; (iv) the enzymatic activity of these enzymes against diribonucleotides versus other substrates; (v) the known physiological consequences of accumulation of linear dinucleotides; and (vi) outstanding biological questions for diribonucleotides and diribonucleases.
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5
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How RNases Shape Mitochondrial Transcriptomes. Int J Mol Sci 2022; 23:ijms23116141. [PMID: 35682820 PMCID: PMC9181182 DOI: 10.3390/ijms23116141] [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: 05/02/2022] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/17/2022] Open
Abstract
Mitochondria are the power houses of eukaryote cells. These endosymbiotic organelles of prokaryote origin are considered as semi-autonomous since they have retained a genome and fully functional gene expression mechanisms. These pathways are particularly interesting because they combine features inherited from the bacterial ancestor of mitochondria with characteristics that appeared during eukaryote evolution. RNA biology is thus particularly diverse in mitochondria. It involves an unexpectedly vast array of factors, some of which being universal to all mitochondria and others being specific from specific eukaryote clades. Among them, ribonucleases are particularly prominent. They play pivotal functions such as the maturation of transcript ends, RNA degradation and surveillance functions that are required to attain the pool of mature RNAs required to synthesize essential mitochondrial proteins such as respiratory chain proteins. Beyond these functions, mitochondrial ribonucleases are also involved in the maintenance and replication of mitochondrial DNA, and even possibly in the biogenesis of mitochondrial ribosomes. The diversity of mitochondrial RNases is reviewed here, showing for instance how in some cases a bacterial-type enzyme was kept in some eukaryotes, while in other clades, eukaryote specific enzymes were recruited for the same function.
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6
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Zhang J, Sun L, Zhang Q, Bartlam M. Crystal structure of oligoribonuclease from Vibrio cholerae O1 El Tor with bound peptide. Acta Crystallogr F Struct Biol Commun 2021; 77:437-443. [PMID: 34866598 PMCID: PMC8647215 DOI: 10.1107/s2053230x21011043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 10/21/2021] [Indexed: 11/10/2022] Open
Abstract
Oligoribonuclease (Orn), a member of the DEDDh superfamily, can hydrolyse 2-5 nt nanoRNAs to mononucleotides. It is involved in maintaining the intracellular levels of RNA, c-di-GMP signalling and transcription initiation in many bacterial species. Here, the crystal structure of Orn from Vibrio cholerae O1 El Tor (VcOrn) is reported at a resolution of 1.7 Å. VcOrn, which consists of nine α-helices and six β-strands, crystallizes with a single monomer in the asymmetric unit but forms a homodimer via crystallographic twofold symmetry. Electron density is observed in the active pocket that corresponds to an intersubunit N-terminal expression tag with sequence GPLGSHHH. The positively charged N-terminal tag binds in the negatively charged nucleotide-binding pocket with a buried surface area of ∼500 Å2. The N-terminal tag interacts with VcOrn via π-π stacking with two conserved residues involved in nucleotide binding, as well as via salt bridges and hydrogen bonds. The structure reported here reveals that the active pocket can accommodate polypeptides in addition to nucleotides, thus providing an important starting point for investigation into substrate modification and inhibitor design targeting VcOrn.
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Affiliation(s)
- Jianyu Zhang
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Protein Science and College of Life Sciences, Nankai University, 38 Tongyan Road, Tianjin 300350, People’s Republic of China
| | - Liyuan Sun
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Protein Science and College of Life Sciences, Nankai University, 38 Tongyan Road, Tianjin 300350, People’s Republic of China
| | - Qionglin Zhang
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Protein Science and College of Life Sciences, Nankai University, 38 Tongyan Road, Tianjin 300350, People’s Republic of China
| | - Mark Bartlam
- State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Protein Science and College of Life Sciences, Nankai University, 38 Tongyan Road, Tianjin 300350, People’s Republic of China
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7
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Lormand JD, Kim SK, Walters-Marrah GA, Brownfield BA, Fromme JC, Winkler WC, Goodson JR, Lee VT, Sondermann H. Structural characterization of NrnC identifies unifying features of dinucleotidases. eLife 2021; 10:70146. [PMID: 34533457 PMCID: PMC8492067 DOI: 10.7554/elife.70146] [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: 05/12/2021] [Accepted: 09/08/2021] [Indexed: 11/13/2022] Open
Abstract
RNA degradation is fundamental for cellular homeostasis. The process is carried out by various classes of endolytic and exolytic enzymes that together degrade an RNA polymer to mono-ribonucleotides. Within the exoribonucleases, nano-RNases play a unique role as they act on the smallest breakdown products and hence catalyze the final steps in the process. We recently showed that oligoribonuclease (Orn) acts as a dedicated diribonuclease, defining the ultimate step in RNA degradation that is crucial for cellular fitness (Kim et al., 2019). Whether such a specific activity exists in organisms that lack Orn-type exoribonucleases remained unclear. Through quantitative structure-function analyses, we show here that NrnC-type RNases share this narrow substrate length preference with Orn. Although NrnC and Orn employ similar structural features that distinguish these two classes of dinucleases from other exonucleases, the key determinants for dinuclease activity are realized through distinct structural scaffolds. The structures, together with comparative genomic analyses of the phylogeny of DEDD-type exoribonucleases, indicate convergent evolution as the mechanism of how dinuclease activity emerged repeatedly in various organisms. The evolutionary pressure to maintain dinuclease activity further underlines the important role these analogous proteins play for cell growth.
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Affiliation(s)
- Justin D Lormand
- Department of Molecular Medicine, Cornell University, Ithaca, United States
| | - Soo-Kyoung Kim
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | | | - Bryce A Brownfield
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - J Christopher Fromme
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Wade C Winkler
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Jonathan R Goodson
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Vincent T Lee
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Holger Sondermann
- Department of Molecular Medicine, Cornell University, Ithaca, United States.,CSSB Centre for Structural Systems Biology, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.,Christian-Albrechts-Universität, Kiel, Germany
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8
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Human Mitochondrial RNA Processing and Modifications: Overview. Int J Mol Sci 2021; 22:ijms22157999. [PMID: 34360765 PMCID: PMC8348895 DOI: 10.3390/ijms22157999] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/23/2021] [Accepted: 07/24/2021] [Indexed: 01/29/2023] Open
Abstract
Mitochondria, often referred to as the powerhouses of cells, are vital organelles that are present in almost all eukaryotic organisms, including humans. They are the key energy suppliers as the site of adenosine triphosphate production, and are involved in apoptosis, calcium homeostasis, and regulation of the innate immune response. Abnormalities occurring in mitochondria, such as mitochondrial DNA (mtDNA) mutations and disturbances at any stage of mitochondrial RNA (mtRNA) processing and translation, usually lead to severe mitochondrial diseases. A fundamental line of investigation is to understand the processes that occur in these organelles and their physiological consequences. Despite substantial progress that has been made in the field of mtRNA processing and its regulation, many unknowns and controversies remain. The present review discusses the current state of knowledge of RNA processing in human mitochondria and sheds some light on the unresolved issues.
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9
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Szewczyk M, Malik D, Borowski LS, Czarnomska SD, Kotrys AV, Klosowska-Kosicka K, Nowotny M, Szczesny RJ. Human REXO2 controls short mitochondrial RNAs generated by mtRNA processing and decay machinery to prevent accumulation of double-stranded RNA. Nucleic Acids Res 2020; 48:5572-5590. [PMID: 32365187 PMCID: PMC7261184 DOI: 10.1093/nar/gkaa302] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 03/31/2020] [Accepted: 04/22/2020] [Indexed: 12/15/2022] Open
Abstract
RNA decay is a key element of mitochondrial RNA metabolism. To date, the only well-documented machinery that plays a role in mtRNA decay in humans is the complex of polynucleotide phosphorylase (PNPase) and SUV3 helicase, forming the degradosome. REXO2, a homolog of prokaryotic oligoribonucleases present in humans both in mitochondria and the cytoplasm, was earlier shown to be crucial for maintaining mitochondrial homeostasis, but its function in mitochondria has not been fully elucidated. In the present study, we created a cellular model that enables the clear dissection of mitochondrial and non-mitochondrial functions of human REXO2. We identified a novel mitochondrial short RNA, referred to as ncH2, that massively accumulated upon REXO2 silencing. ncH2 degradation occurred independently of the mitochondrial degradosome, strongly supporting the hypothesis that ncH2 is a primary substrate of REXO2. We also investigated the global impact of REXO2 depletion on mtRNA, revealing the importance of the protein for maintaining low steady-state levels of mitochondrial antisense transcripts and double-stranded RNA. Our detailed biochemical and structural studies provide evidence of sequence specificity of the REXO2 oligoribonuclease. We postulate that REXO2 plays dual roles in human mitochondria, ‘scavenging’ nanoRNAs that are produced by the degradosome and clearing short RNAs that are generated by RNA processing.
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Affiliation(s)
- Maciej Szewczyk
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw 02-106, Poland.,Faculty of Biology, Institute of Genetics and Biotechnology, University of Warsaw, Warsaw 02-106, Poland
| | - Deepshikha Malik
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Lukasz S Borowski
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw 02-106, Poland.,Faculty of Biology, Institute of Genetics and Biotechnology, University of Warsaw, Warsaw 02-106, Poland
| | - Sylwia D Czarnomska
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw 02-106, Poland
| | - Anna V Kotrys
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw 02-106, Poland
| | | | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw 02-109, Poland
| | - Roman J Szczesny
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw 02-106, Poland
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10
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Abstract
Pheochromocytoma (PCC) is a rare, mostly benign tumour of the adrenal medulla. Hereditary PCC accounts for ~35% of cases and has been associated with germline mutations in several cancer susceptibility genes (e.g., KIF1B, SDHB, VHL, SDHD, RET). We performed whole-exome sequencing in a family with four PCC-affected patients in two consecutive generations and identified a potential novel candidate pathogenic variant in the REXO2 gene that affects splicing (c.531-1G>T (NM 015523.3)), which co-segregated with the phenotype in the family. REXO2 encodes for RNA exonuclease 2 protein and localizes to 11q23, a chromosomal region displaying allelic imbalance in PCC. REXO2 protein has been associated with DNA repair, replication and recombination processes and thus its inactivation may contribute to tumorigenesis. While the study suggests that this novel REXO2 gene variant underlies PCC in this family, additional functional studies are required in order to establish the putative role of the REXO2 gene in PCC predisposition.
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11
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Doamekpor SK, Gozdek A, Kwasnik A, Kufel J, Tong L. A novel 5'-hydroxyl dinucleotide hydrolase activity for the DXO/Rai1 family of enzymes. Nucleic Acids Res 2020; 48:349-358. [PMID: 31777937 PMCID: PMC6943137 DOI: 10.1093/nar/gkz1107] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 11/01/2019] [Accepted: 11/13/2019] [Indexed: 12/16/2022] Open
Abstract
Modifications at the 5'-end of RNAs play a pivotal role in determining their fate. In eukaryotes, the DXO/Rai1 family of enzymes removes numerous 5'-end RNA modifications, thereby regulating RNA turnover. Mouse DXO catalyzes the elimination of incomplete 5'-end caps (including pyrophosphate) and the non-canonical NAD+ cap on mRNAs, and possesses distributive 5'-3' exoribonuclease activity toward 5'-monophosphate (5'-PO4) RNA. Here, we demonstrate that DXO also catalyzes the hydrolysis of RNAs bearing a 5'-hydroxyl group (5'-OH RNA). The crystal structure of DXO in complex with a 5'-OH RNA substrate mimic at 2.0 Å resolution provides elegant insight into the molecular mechanism of this activity. More importantly, the structure predicts that DXO first removes a dinucleotide from 5'-OH RNA. Our nuclease assays confirm this prediction and demonstrate that this 5'-hydroxyl dinucleotide hydrolase (HDH) activity for DXO is higher than the subsequent 5'-3' exoribonuclease activity for selected substrates. Fission yeast Rai1 also has HDH activity although it does not have 5'-3' exonuclease activity, and the Rat1-Rai1 complex can completely degrade 5'-OH RNA. An Arabidopsis DXO1 variant is active toward 5'-OH RNA but prefers 5'-PO4 RNA. Collectively, these studies demonstrate the diverse activities of DXO/Rai1 and expands the collection of RNA substrates that can undergo 5'-3' mediated decay.
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Affiliation(s)
- Selom K Doamekpor
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Agnieszka Gozdek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Aleksandra Kwasnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Joanna Kufel
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, 02-106 Warsaw, Poland
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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12
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Nicholls TJ, Spåhr H, Jiang S, Siira SJ, Koolmeister C, Sharma S, Kauppila JHK, Jiang M, Kaever V, Rackham O, Chabes A, Falkenberg M, Filipovska A, Larsson NG, Gustafsson CM. Dinucleotide Degradation by REXO2 Maintains Promoter Specificity in Mammalian Mitochondria. Mol Cell 2019; 76:784-796.e6. [PMID: 31588022 PMCID: PMC6900737 DOI: 10.1016/j.molcel.2019.09.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/12/2019] [Accepted: 09/04/2019] [Indexed: 12/12/2022]
Abstract
Oligoribonucleases are conserved enzymes that degrade short RNA molecules of up to 5 nt in length and are assumed to constitute the final stage of RNA turnover. Here we demonstrate that REXO2 is a specialized dinucleotide-degrading enzyme that shows no preference between RNA and DNA dinucleotide substrates. A heart- and skeletal-muscle-specific knockout mouse displays elevated dinucleotide levels and alterations in gene expression patterns indicative of aberrant dinucleotide-primed transcription initiation. We find that dinucleotides act as potent stimulators of mitochondrial transcription initiation in vitro. Our data demonstrate that increased levels of dinucleotides can be used to initiate transcription, leading to an increase in transcription levels from both mitochondrial promoters and other, nonspecific sequence elements in mitochondrial DNA. Efficient RNA turnover by REXO2 is thus required to maintain promoter specificity and proper regulation of transcription in mammalian mitochondria.
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Affiliation(s)
- Thomas J Nicholls
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Henrik Spåhr
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany; Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden; Max Planck Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm 17177, Sweden
| | - Shan Jiang
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden; Max Planck Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm 17177, Sweden
| | - Stefan J Siira
- Harry Perkins Institute of Medical Research, Nedlands, WA 6009, Australia; Centre for Medical Research, The University of Western Australia, Nedlands, WA 6009, Australia
| | - Camilla Koolmeister
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden; Max Planck Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm 17177, Sweden
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå 901 87, Sweden
| | - Johanna H K Kauppila
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Min Jiang
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Hannover Medical School, 30625 Hannover, Germany
| | - Oliver Rackham
- Harry Perkins Institute of Medical Research, Nedlands, WA 6009, Australia; School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, WA 6102, Australia; Curtin Health Innovation Research Institute, Curtin University, Bentley, WA 6102, Australia
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå 901 87, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Aleksandra Filipovska
- Harry Perkins Institute of Medical Research, Nedlands, WA 6009, Australia; School of Molecular Sciences, The University of Western Australia, Nedlands, WA, Australia
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden; Max Planck Institute for Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm 17177, Sweden.
| | - Claes M Gustafsson
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden.
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Kim SK, Lormand JD, Weiss CA, Eger KA, Turdiev H, Turdiev A, Winkler WC, Sondermann H, Lee VT. A dedicated diribonucleotidase resolves a key bottleneck for the terminal step of RNA degradation. eLife 2019; 8:46313. [PMID: 31225796 PMCID: PMC6613908 DOI: 10.7554/elife.46313] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 06/14/2019] [Indexed: 12/28/2022] Open
Abstract
Degradation of RNA polymers, an ubiquitous process in all cells, is catalyzed by specific subsets of endo- and exoribonucleases that together recycle RNA fragments into nucleotide monophosphate. In γ-proteobacteria, 3-'5' exoribonucleases comprise up to eight distinct enzymes. Among them, Oligoribonuclease (Orn) is unique as its activity is required for clearing short RNA fragments, which is important for cellular fitness. However, the molecular basis of Orn's unique cellular function remained unclear. Here, we show that Orn exhibits exquisite substrate preference for diribonucleotides. Crystal structures of substrate-bound Orn reveal an active site optimized for diribonucleotides. While other cellular RNases process oligoribonucleotides down to diribonucleotide entities, Orn is the one and only diribonucleotidase that completes the terminal step of RNA degradation. Together, our studies indicate RNA degradation as a step-wise process with a dedicated enzyme for the clearance of a specific intermediate pool, diribonucleotides, that affects cellular physiology and viability.
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Affiliation(s)
- Soo-Kyoung Kim
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Justin D Lormand
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, United States
| | - Cordelia A Weiss
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Karin A Eger
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, United States
| | - Husan Turdiev
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Asan Turdiev
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Wade C Winkler
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
| | - Holger Sondermann
- Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, United States
| | - Vincent T Lee
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, United States
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