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Bárria C, Athayde D, Hernandez G, Fonseca L, Casinhas J, Cordeiro TN, Archer M, Arraiano CM, Brito JA, Matos RG. Structure and function of Campylobacter jejuni polynucleotide phosphorylase (PNPase): Insights into the role of this RNase in pathogenicity. Biochimie 2024; 216:56-70. [PMID: 37806617 DOI: 10.1016/j.biochi.2023.10.006] [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: 07/24/2023] [Revised: 09/29/2023] [Accepted: 10/06/2023] [Indexed: 10/10/2023]
Abstract
Ribonucleases are in charge of the processing, degradation and quality control of all cellular transcripts, which makes them crucial factors in RNA regulation. This post-transcriptional regulation allows bacteria to promptly react to different stress conditions and growth phase transitions, and also to produce the required virulence factors in pathogenic bacteria. Campylobacter jejuni is the main responsible for human gastroenteritis in the world. In this foodborne pathogen, exoribonuclease PNPase (CjPNP) is essential for low-temperature cell survival, affects the synthesis of proteins involved in virulence and has an important role in swimming, cell adhesion/invasion ability, and chick colonization. Here we report the crystallographic structure of CjPNP, complemented with SAXS, which confirms the characteristic doughnut-shaped trimeric arrangement and evaluates domain arrangement and flexibility. Mutations in highly conserved residues were constructed to access their role in RNA degradation and polymerization. Surprisingly, we found two mutations that altered CjPNP into a protein that is only capable of degrading RNA even in conditions that favour polymerization. These findings will be important to develop new strategies to combat C. jejuni infections.
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Affiliation(s)
- Cátia Bárria
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Diogo Athayde
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Guillem Hernandez
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Leonor Fonseca
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Jorge Casinhas
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Tiago N Cordeiro
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Margarida Archer
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Cecília M Arraiano
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - José A Brito
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
| | - Rute G Matos
- ITQB NOVA, Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Avenida da República, 2780-157, Oeiras, Portugal.
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Falchi FA, Forti F, Carnelli C, Genco A, Pizzoccheri R, Manzari C, Pavesi G, Briani F. Human PNPase causes RNA stabilization and accumulation of R-loops in the Escherichia coli model system. Sci Rep 2023; 13:11771. [PMID: 37479726 PMCID: PMC10362022 DOI: 10.1038/s41598-023-38924-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 07/17/2023] [Indexed: 07/23/2023] Open
Abstract
Polyribonucleotide phosphorylase (PNPase) is a phosphorolytic RNA exonuclease highly conserved throughout evolution. In Escherichia coli, PNPase controls complex phenotypic traits like biofilm formation and growth at low temperature. In human cells, PNPase is located in mitochondria, where it is implicated in the RNA import from the cytoplasm, the mitochondrial RNA degradation and the processing of R-loops, namely stable RNA-DNA hybrids displacing a DNA strand. In this work, we show that the human PNPase (hPNPase) expressed in E. coli causes oxidative stress, SOS response activation and R-loops accumulation. Hundreds of E. coli RNAs are stabilized in presence of hPNPase, whereas only few transcripts are destabilized. Moreover, phenotypic traits typical of E. coli strains lacking PNPase are strengthened in presence of the human enzyme. We discuss the hypothesis that hPNPase expressed in E. coli may bind, but not degrade, the RNA, in agreement with previous in vitro data showing that phosphate concentrations in the range of those found in the bacterial cytoplasm and, more relevant, in the mitochondria, inhibit its activity.
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Affiliation(s)
- Federica A Falchi
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Francesca Forti
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Cristina Carnelli
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Aurelia Genco
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Roberto Pizzoccheri
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy
| | - Caterina Manzari
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari "Aldo Moro", 70121, Bari, Italy
| | - Giulio Pavesi
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy.
| | - Federica Briani
- Dipartimento di Bioscienze, Università degli Studi di Milano, 20133, Milan, Italy.
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Single-exonuclease nanocircuits reveal the RNA degradation dynamics of PNPase and demonstrate potential for RNA sequencing. Nat Commun 2023; 14:552. [PMID: 36725855 PMCID: PMC9892577 DOI: 10.1038/s41467-023-36278-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 01/23/2023] [Indexed: 02/03/2023] Open
Abstract
The degradation process of RNA is decisive in guaranteeing high-fidelity translation of genetic information in living organisms. However, visualizing the single-base degradation process in real time and deciphering the degradation mechanism at the single-enzyme level remain formidable challenges. Here, we present a reliable in-situ single-PNPase-molecule dynamic electrical detector based on silicon nanowire field-effect transistors with ultra-high temporal resolution. These devices are capable of realizing real-time and label-free monitoring of RNA analog degradation with single-base resolution, including RNA analog binding, single-nucleotide hydrolysis, and single-base movement. We discover a binding event of the enzyme (near the active site) with the nucleoside, offering a further understanding of the RNA degradation mechanism. Relying on systematic analyses of independent reads, approximately 80% accuracy in RNA nucleoside sequencing is achieved in a single testing process. This proof-of-concept sets up a Complementary Metal Oxide Semiconductor (CMOS)-compatible playground for the development of high-throughput detection technologies toward mechanistic exploration and single-molecule sequencing.
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Falchi FA, Pizzoccheri R, Briani F. Activity and Function in Human Cells of the Evolutionary Conserved Exonuclease Polynucleotide Phosphorylase. Int J Mol Sci 2022; 23:ijms23031652. [PMID: 35163574 PMCID: PMC8836086 DOI: 10.3390/ijms23031652] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 01/28/2022] [Accepted: 01/28/2022] [Indexed: 02/04/2023] Open
Abstract
Polynucleotide phosphorylase (PNPase) is a phosphorolytic RNA exonuclease highly conserved throughout evolution. Human PNPase (hPNPase) is located in mitochondria and is essential for mitochondrial function and homeostasis. Not surprisingly, mutations in the PNPT1 gene, encoding hPNPase, cause serious diseases. hPNPase has been implicated in a plethora of processes taking place in different cell compartments and involving other proteins, some of which physically interact with hPNPase. This paper reviews hPNPase RNA binding and catalytic activity in relation with the protein structure and in comparison, with the activity of bacterial PNPases. The functions ascribed to hPNPase in different cell compartments are discussed, highlighting the gaps that still need to be filled to understand the physiological role of this ancient protein in human cells.
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Gonzalez-Rivera JC, Orr AA, Engels SM, Jakubowski JM, Sherman MW, O'Connor KN, Matteson T, Woodcock BC, Contreras LM, Tamamis P. Computational evolution of an RNA-binding protein towards enhanced oxidized-RNA binding. Comput Struct Biotechnol J 2020; 18:137-152. [PMID: 31988703 PMCID: PMC6965710 DOI: 10.1016/j.csbj.2019.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 12/02/2022] Open
Abstract
The oxidation of RNA has been implicated in the development of many diseases. Among the four ribonucleotides, guanosine is the most susceptible to oxidation, resulting in the formation of 8-oxo-7,8-dihydroguanosine (8-oxoG). Despite the limited knowledge about how cells regulate the detrimental effects of oxidized RNA, cellular factors involved in its regulation have begun to be identified. One of these factors is polynucleotide phosphorylase (PNPase), a multifunctional enzyme implicated in RNA turnover. In the present study, we have examined the interaction of PNPase with 8-oxoG in atomic detail to provide insights into the mechanism of 8-oxoG discrimination. We hypothesized that PNPase subunits cooperate to form a binding site using the dynamic SFF loop within the central channel of the PNPase homotrimer. We evolved this site using a novel approach that initially screened mutants from a library of beneficial mutations and assessed their interactions using multi-nanosecond Molecular Dynamics simulations. We found that evolving this single site resulted in a fold change increase in 8-oxoG affinity between 1.2 and 1.5 and/or selectivity between 1.5 and 1.9. In addition to the improvement in 8-oxoG binding, complementation of K12 Δpnp with plasmids expressing mutant PNPases caused increased cell tolerance to H2O2. This observation provides a clear link between molecular discrimination of RNA oxidation and cell survival. Moreover, this study provides a framework for the manipulation of modified-RNA protein readers, which has potential application in synthetic biology and epitranscriptomics.
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Affiliation(s)
- Juan C. Gonzalez-Rivera
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Asuka A. Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Sean M. Engels
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Joseph M. Jakubowski
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Mark W. Sherman
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
| | - Katherine N. O'Connor
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Tomas Matteson
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
| | - Brendan C. Woodcock
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Lydia M. Contreras
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
- Corresponding authors at: McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States (L.M. Contreras).
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
- Corresponding authors at: McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States (L.M. Contreras).
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6
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Cameron TA, Matz LM, De Lay NR. Polynucleotide phosphorylase: Not merely an RNase but a pivotal post-transcriptional regulator. PLoS Genet 2018; 14:e1007654. [PMID: 30307990 PMCID: PMC6181284 DOI: 10.1371/journal.pgen.1007654] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Almost 60 years ago, Severo Ochoa was awarded the Nobel Prize in Physiology or Medicine for his discovery of the enzymatic synthesis of RNA by polynucleotide phosphorylase (PNPase). Although this discovery provided an important tool for deciphering the genetic code, subsequent work revealed that the predominant function of PNPase in bacteria and eukaryotes is catalyzing the reverse reaction, i.e., the release of ribonucleotides from RNA. PNPase has a crucial role in RNA metabolism in bacteria and eukaryotes mainly through its roles in processing and degrading RNAs, but additional functions in RNA metabolism have recently been reported for this enzyme. Here, we discuss these established and noncanonical functions for PNPase and the possibility that the major impact of PNPase on cell physiology is through its unorthodox roles.
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Affiliation(s)
- Todd A. Cameron
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Lisa M. Matz
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas, United States of America
| | - Nicholas R. De Lay
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center, Houston, Texas, United States of America
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Texas, United States of America
- * E-mail:
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7
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Dos Santos RF, Quendera AP, Boavida S, Seixas AF, Arraiano CM, Andrade JM. Major 3'-5' Exoribonucleases in the Metabolism of Coding and Non-coding RNA. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2018; 159:101-155. [PMID: 30340785 DOI: 10.1016/bs.pmbts.2018.07.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
3'-5' exoribonucleases are key enzymes in the degradation of superfluous or aberrant RNAs and in the maturation of precursor RNAs into their functional forms. The major bacterial 3'-5' exoribonucleases responsible for both these activities are PNPase, RNase II and RNase R. These enzymes are of ancient nature with widespread distribution. In eukaryotes, PNPase and RNase II/RNase R enzymes can be found in the cytosol and in mitochondria and chloroplasts; RNase II/RNase R-like enzymes are also found in the nucleus. Humans express one PNPase (PNPT1) and three RNase II/RNase R family members (Dis3, Dis3L and Dis3L2). These enzymes take part in a multitude of RNA surveillance mechanisms that are critical for translation accuracy. Although active against a wide range of both coding and non-coding RNAs, the different 3'-5' exoribonucleases exhibit distinct substrate affinities. The latest studies on these RNA degradative enzymes have contributed to the identification of additional homologue proteins, the uncovering of novel RNA degradation pathways, and to a better comprehension of several disease-related processes and response to stress, amongst many other exciting findings. Here, we provide a comprehensive and up-to-date overview on the function, structure, regulation and substrate preference of the key 3'-5' exoribonucleases involved in RNA metabolism.
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Affiliation(s)
- Ricardo F Dos Santos
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Ana P Quendera
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Sofia Boavida
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - André F Seixas
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Cecília M Arraiano
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - José M Andrade
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
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Shimada E, Ahsan FM, Nili M, Huang D, Atamdede S, TeSlaa T, Case D, Yu X, Gregory BD, Perrin BJ, Koehler CM, Teitell MA. PNPase knockout results in mtDNA loss and an altered metabolic gene expression program. PLoS One 2018; 13:e0200925. [PMID: 30024931 PMCID: PMC6053217 DOI: 10.1371/journal.pone.0200925] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 07/05/2018] [Indexed: 01/10/2023] Open
Abstract
Polynucleotide phosphorylase (PNPase) is an essential mitochondria-localized exoribonuclease implicated in multiple biological processes and human disorders. To reveal role(s) for PNPase in mitochondria, we established PNPase knockout (PKO) systems by first shifting culture conditions to enable cell growth with defective respiration. Interestingly, PKO established in mouse embryonic fibroblasts (MEFs) resulted in the loss of mitochondrial DNA (mtDNA). The transcriptional profile of PKO cells was similar to rho0 mtDNA deleted cells, with perturbations in cholesterol (FDR = 6.35 x 10-13), lipid (FDR = 3.21 x 10-11), and secondary alcohol (FDR = 1.04x10-12) metabolic pathway gene expression compared to wild type parental (TM6) MEFs. Transcriptome analysis indicates processes related to axonogenesis (FDR = 4.49 x 10-3), axon development (FDR = 4.74 x 10-3), and axonal guidance (FDR = 4.74 x 10-3) were overrepresented in PKO cells, consistent with previous studies detailing causative PNPase mutations in delayed myelination, hearing loss, encephalomyopathy, and chorioretinal defects in humans. Overrepresentation analysis revealed alterations in metabolic pathways in both PKO and rho0 cells. Therefore, we assessed the correlation of genes implicated in cell cycle progression and total metabolism and observed a strong positive correlation between PKO cells and rho0 MEFs compared to TM6 MEFs. We quantified the normalized biomass accumulation rate of PKO clones at 1.7% (SD ± 2.0%) and 2.4% (SD ± 1.6%) per hour, which was lower than TM6 cells at 3.3% (SD ± 3.5%) per hour. Furthermore, PKO in mouse inner ear hair cells caused progressive hearing loss that parallels human familial hearing loss previously linked to mutations in PNPase. Combined, our study reports that knockout of a mitochondrial nuclease results in mtDNA loss and suggests that mtDNA maintenance could provide a unifying connection for the large number of biological activities reported for PNPase.
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Affiliation(s)
- Eriko Shimada
- Molecular Biology Institute Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
| | - Fasih M. Ahsan
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Mahta Nili
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Dian Huang
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
| | - Sean Atamdede
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Tara TeSlaa
- Molecular Biology Institute Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
| | - Dana Case
- Molecular Biology Institute Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
| | - Xiang Yu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Brian D. Gregory
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Benjamin J. Perrin
- Department of Biology, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana, United States of America
| | - Carla M. Koehler
- Molecular Biology Institute Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
- Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California, United States of America
| | - Michael A. Teitell
- Molecular Biology Institute Interdepartmental Program, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
- Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California, United States of America
- Broad Center for Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Pediatrics, University of California Los Angeles, Los Angeles, California, United States of America
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, California, United States of America
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Raj R, Mitra S, Gopal B. Characterization of Staphylococcus epidermidis Polynucleotide phosphorylase and its interactions with ribonucleases RNase J1 and RNase J2. Biochem Biophys Res Commun 2017; 495:2078-2084. [PMID: 29242153 DOI: 10.1016/j.bbrc.2017.12.056] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 12/10/2017] [Indexed: 11/16/2022]
Abstract
Polynucleotide phosphorylase catalyzes both 3'-5' exoribonuclease and polyadenylation reactions. The crystal structure of Staphylococcus epidermidis PNPase revealed a bound phosphate in the PH2 domain of each protomer coordinated by three adjacent serine residues. Mutational analysis suggests that phosphate coordination by these serine residues is essential to maintain the catalytic center in an active conformation. We note that PNPase forms a complex with RNase J1 and RNase J2 without substantially altering either exo-ribonuclease or polyadenylation activity of this enzyme. This decoupling of catalytic activity from protein-protein interactions suggests that association of these endo- or exo-ribonucleases with PNPase could be more relevant for cellular localization or concerted targeting of structured RNA for recycling.
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Affiliation(s)
- Rishi Raj
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
| | - Sharmistha Mitra
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
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10
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Carzaniga T, Sbarufatti G, Briani F, Dehò G. Polynucleotide phosphorylase is implicated in homologous recombination and DNA repair in Escherichia coli. BMC Microbiol 2017; 17:81. [PMID: 28376742 PMCID: PMC5379764 DOI: 10.1186/s12866-017-0980-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 03/25/2017] [Indexed: 11/22/2022] Open
Abstract
Background Polynucleotide phosphorylase (PNPase, encoded by pnp) is generally thought of as an enzyme dedicated to RNA metabolism. The pleiotropic effects of PNPase deficiency is imputed to altered processing and turnover of mRNAs and small RNAs, which in turn leads to aberrant gene expression. However, it has long since been known that this enzyme may also catalyze template-independent polymerization of dNDPs into ssDNA and the reverse phosphorolytic reaction. Recently, PNPase has been implicated in DNA recombination, repair, mutagenesis and resistance to genotoxic agents in diverse bacterial species, raising the possibility that PNPase may directly, rather than through control of gene expression, participate in these processes. Results In this work we present evidence that in Escherichia coli PNPase enhances both homologous recombination upon P1 transduction and error prone DNA repair of double strand breaks induced by zeocin, a radiomimetic agent. Homologous recombination does not require PNPase phosphorolytic activity and is modulated by its RNA binding domains whereas error prone DNA repair of zeocin-induced DNA damage is dependent on PNPase catalytic activity and cannot be suppressed by overexpression of RNase II, the other major enzyme (encoded by rnb) implicated in exonucleolytic RNA degradation. Moreover, E. coli pnp mutants are more sensitive than the wild type to zeocin. This phenotype depends on PNPase phosphorolytic activity and is suppressed by rnb, thus suggesting that zeocin detoxification may largely depend on RNA turnover. Conclusions Our data suggest that PNPase may participate both directly and indirectly through regulation of gene expression to several aspects of DNA metabolism such as recombination, DNA repair and resistance to genotoxic agents.
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Affiliation(s)
- Thomas Carzaniga
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, Milan, 20133, Italy.,Present address: Dipartimento di Biotecnologie mediche e medicina traslazionale, Università degli Studi di Milano, via F.lli Cervi 93, Segrate, MI, 20090, Italy
| | - Giulia Sbarufatti
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, Milan, 20133, Italy.,Present address: Eurofins BioPharma Product Testing Italy, Eurofins Biolab srl, via Bruno Buozzi, 2, Vimodrone, 20090, Italy
| | - Federica Briani
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, Milan, 20133, Italy
| | - Gianni Dehò
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, Milan, 20133, Italy.
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11
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Briani F, Carzaniga T, Dehò G. Regulation and functions of bacterial PNPase. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 7:241-58. [PMID: 26750178 DOI: 10.1002/wrna.1328] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/23/2015] [Accepted: 11/23/2015] [Indexed: 01/29/2023]
Abstract
Polynucleotide phosphorylase (PNPase) is an exoribonuclease that catalyzes the processive phosphorolytic degradation of RNA from the 3'-end. The enzyme catalyzes also the reverse reaction of polymerization of nucleoside diphosphates that has been implicated in the generation of heteropolymeric tails at the RNA 3'-end. The enzyme is widely conserved and plays a major role in RNA decay in both Gram-negative and Gram-positive bacteria. Moreover, it participates in maturation and quality control of stable RNA. PNPase autoregulates its own expression at post-transcriptional level through a complex mechanism that involves the endoribonuclease RNase III and translation control. The activity of PNPase is modulated in an intricate and still unclear manner by interactions with small molecules and recruitment in different multiprotein complexes. Not surprisingly, given the wide spectrum of PNPase substrates, PNPase-defective mutations in different bacterial species have pleiotropic effects and perturb the execution of genetic programs involving drastic changes in global gene expression such as biofilm formation, growth at suboptimal temperatures, and virulence.
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Affiliation(s)
- Federica Briani
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Thomas Carzaniga
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Gianni Dehò
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
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12
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RNase III-Independent Autogenous Regulation of Escherichia coli Polynucleotide Phosphorylase via Translational Repression. J Bacteriol 2015; 197:1931-8. [PMID: 25825432 DOI: 10.1128/jb.00105-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 03/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The complex posttranscriptional regulation mechanism of the Escherichia coli pnp gene, which encodes the phosphorolytic exoribonuclease polynucleotide phosphorylase (PNPase), involves two endoribonucleases, namely, RNase III and RNase E, and PNPase itself, which thus autoregulates its own expression. The models proposed for pnp autoregulation posit that the target of PNPase is a mature pnp mRNA previously processed at its 5' end by RNase III, rather than the primary pnp transcript (RNase III-dependent models), and that PNPase activity eventually leads to pnp mRNA degradation by RNase E. However, some published data suggest that pnp expression may also be regulated through a PNPase-dependent, RNase III-independent mechanism. To address this issue, we constructed isogenic Δpnp rnc(+) and Δpnp Δrnc strains with a chromosomal pnp-lacZ translational fusion and measured β-galactosidase activity in the absence and presence of PNPase expressed by a plasmid. Our results show that PNPase also regulates its own expression via a reversible RNase III-independent pathway acting upstream from the RNase III-dependent branch. This pathway requires the PNPase RNA binding domains KH and S1 but not its phosphorolytic activity. We suggest that the RNase III-independent autoregulation of PNPase occurs at the level of translational repression, possibly by competition for pnp primary transcript between PNPase and the ribosomal protein S1. IMPORTANCE In Escherichia coli, polynucleotide phosphorylase (PNPase, encoded by pnp) posttranscriptionally regulates its own expression. The two models proposed so far posit a two-step mechanism in which RNase III, by cutting the leader region of the pnp primary transcript, creates the substrate for PNPase regulatory activity, eventually leading to pnp mRNA degradation by RNase E. In this work, we provide evidence supporting an additional pathway for PNPase autogenous regulation in which PNPase acts as a translational repressor independently of RNase III cleavage. Our data make a new contribution to the understanding of the regulatory mechanism of pnp mRNA, a process long since considered a paradigmatic example of posttranscriptional regulation at the level of mRNA stability.
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