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Cross EM, Marin O, Ariawan D, Aragão D, Cozza G, Di Iorio E, Forwood JK, Alvisi G. Structural determinants of phosphorylation-dependent nuclear transport of HCMV DNA polymerase processivity factor UL44. FEBS Lett 2024; 598:199-209. [PMID: 38158756 DOI: 10.1002/1873-3468.14797] [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: 10/30/2023] [Revised: 12/08/2023] [Accepted: 12/11/2023] [Indexed: 01/03/2024]
Abstract
Human cytomegalovirus DNA polymerase processivity factor UL44 is transported into the nucleus by importin (IMP) α/β through a classical nuclear localization signal (NLS), and this region is susceptible to cdc2-mediated phosphorylation at position T427. Whilst phosphorylation within and close to the UL44 NLS regulates nuclear transport, the details remain elusive, due to the paucity of structural information regarding the role of negatively charged cargo phosphate groups. We addressed this issue by studying the effect of UL44 T427 phosphorylation on interaction with several IMPα isoforms by biochemical and structural approaches. Phosphorylation decreased UL44/IMPα affinity 10-fold, and a comparative structural analysis of UL44 NLS phosphorylated and non-phosphorylated peptides complexed with mouse IMPα2 revealed the structural rearrangements responsible for phosphorylation-dependent inhibition of UL44 nuclear import.
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Affiliation(s)
- Emily M Cross
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, Australia
- Diamond Light Source, Didcot, UK
| | - Oriano Marin
- Department of Biomedical Sciences, University of Padova, Italy
| | - Daryl Ariawan
- Dementia Research Centre, Macquarie University, Sydney, Australia
| | | | - Giorgio Cozza
- Department of Molecular Medicine, University of Padua, Italy
| | - Enzo Di Iorio
- Department of Molecular Medicine, University of Padua, Italy
| | - Jade K Forwood
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, Australia
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Li HM, Ghildyal R, Hu M, Tran KC, Starrs LM, Mills J, Teng MN, Jans DA. Respiratory Syncytial Virus Matrix Protein-Chromatin Association Is Key to Transcriptional Inhibition in Infected Cells. Cells 2021; 10:2786. [PMID: 34685766 PMCID: PMC8534903 DOI: 10.3390/cells10102786] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 09/23/2021] [Accepted: 10/06/2021] [Indexed: 01/07/2023] Open
Abstract
The morbidity and mortality caused by the globally prevalent human respiratory pathogen respiratory syncytial virus (RSV) approaches that world-wide of influenza. We previously demonstrated that the RSV matrix (M) protein shuttles, in signal-dependent fashion, between host cell nucleus and cytoplasm, and that this trafficking is central to RSV replication and assembly. Here we analyze in detail the nuclear role of M for the first time using a range of novel approaches, including quantitative analysis of de novo cell transcription in situ in the presence or absence of RSV infection or M ectopic expression, as well as in situ DNA binding. We show that M, dependent on amino acids 110-183, inhibits host cell transcription in RSV-infected cells as well as cells transfected to express M, with a clear correlation between nuclear levels of M and the degree of transcriptional inhibition. Analysis of bacterially expressed M protein and derivatives thereof mutated in key residues within M's RNA binding domain indicates that M can bind to DNA as well as RNA in a cell-free system. Parallel results for point-mutated M derivatives implicate arginine 170 and lysine 172, in contrast to other basic residues such as lysine 121 and 130, as critically important residues for inhibition of transcription and DNA binding both in situ and in vitro. Importantly, recombinant RSV carrying arginine 170/lysine 172 mutations shows attenuated infectivity in cultured cells and in an animal model, concomitant with altered inflammatory responses. These findings define an RSV M-chromatin interface critical for host transcriptional inhibition in infection, with important implications for anti-RSV therapeutic development.
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Affiliation(s)
- Hong-Mei Li
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, VIC 3800, Australia; (H.-M.L.); (R.G.); (M.H.)
| | - Reena Ghildyal
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, VIC 3800, Australia; (H.-M.L.); (R.G.); (M.H.)
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra, ACT 2617, Australia;
| | - Mengjie Hu
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, VIC 3800, Australia; (H.-M.L.); (R.G.); (M.H.)
| | - Kim C. Tran
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; (K.C.T.); (M.N.T.)
| | - Lora M. Starrs
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra, ACT 2617, Australia;
| | - John Mills
- Department of Infectious Diseases, School of Biomedical Sciences, Monash University and the Burnet Institute, Melbourne, VIC 3004, Australia;
| | - Michael N. Teng
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; (K.C.T.); (M.N.T.)
| | - David A. Jans
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Melbourne, VIC 3800, Australia; (H.-M.L.); (R.G.); (M.H.)
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Messa L, Celegato M, Bertagnin C, Mercorelli B, Alvisi G, Banks L, Palù G, Loregian A. The Dimeric Form of HPV16 E6 Is Crucial to Drive YAP/TAZ Upregulation through the Targeting of hScrib. Cancers (Basel) 2021; 13:cancers13164083. [PMID: 34439242 PMCID: PMC8393709 DOI: 10.3390/cancers13164083] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/06/2021] [Accepted: 08/10/2021] [Indexed: 01/22/2023] Open
Abstract
Simple Summary Understanding the mechanisms of action of HPV oncoproteins is pivotal for the rationale development of anti-cancer drugs to treat HPV-related malignancies. The aim of the present study was to explore more in detail the mechanism of action of the HPV16 oncoprotein E6 that directly fosters the YAP/TAZ signaling pathway, a conserved cascade highly active in HPV-related cancers. We confirmed previous evidence about the importance of the PDZ-protein targeting in this process, highlighting here the importance of hScrib degradation, and discovered that the targeting of the Scribble module involves the dimeric form of HPV16 E6. The findings here presented extend our knowledge about the mechanism through which the oncoprotein E6 targets a PDZ-host factor to degradation in cancer cells. Abstract Human papillomavirus is the most common viral infectious agent responsible for cancer development in humans. High-risk strains are known to induce cancer through the expression of the viral oncogenes E6 and E7, yet we have only a partial understanding of the precise mechanisms of action of these viral proteins. Here we investigated the molecular mechanism through which the oncoprotein E6 alters the Hippo-YAP/TAZ pathway to trigger YAP/TAZ induction in cancer cells. By employing E6 overexpression systems combined with protein–protein interaction studies and loss-of-function approaches, we discovered that the E6-mediated targeting of hScrib, which supports YAP/TAZ upregulation, intimately requires E6 homodimerization. We show that the self-association of E6, previously reported only in vitro, takes place in the cytoplasm and, as a dimer, E6 targets the fraction of hScrib at the cell cortex for proteasomal degradation. Thus, E6 homodimerization emerges as an important event in the mechanism of E6-mediated hScrib targeting to sustain downstream YAP/TAZ upregulation, unraveling for the first time the key role of E6 homodimerization in the context of its transforming functions and thus paving the way for the possible development of E6 dimerization inhibitors.
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Affiliation(s)
- Lorenzo Messa
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Marta Celegato
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Chiara Bertagnin
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Beatrice Mercorelli
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Gualtiero Alvisi
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Lawrence Banks
- International Centre for Genetic Engineering and Biotechnology, 34149 Trieste, Italy;
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
| | - Arianna Loregian
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (L.M.); (M.C.); (C.B.); (B.M.); (G.A.); (G.P.)
- Correspondence: ; Tel.: +39-049-8272363
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Ghassabian H, Falchi F, Timmoneri M, Mercorelli B, Loregian A, Palù G, Alvisi G. Divide et impera: An In Silico Screening Targeting HCMV ppUL44 Processivity Factor Homodimerization Identifies Small Molecules Inhibiting Viral Replication. Viruses 2021; 13:v13050941. [PMID: 34065234 PMCID: PMC8160850 DOI: 10.3390/v13050941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 12/19/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a leading cause of severe diseases in immunocompromised individuals, including AIDS patients and transplant recipients, and in congenitally infected newborns. The utility of available drugs is limited by poor bioavailability, toxicity, and emergence of resistant strains. Therefore, it is crucial to identify new targets for therapeutic intervention. Among the latter, viral protein–protein interactions are becoming increasingly attractive. Since dimerization of HCMV DNA polymerase processivity factor ppUL44 plays an essential role in the viral life cycle, being required for oriLyt-dependent DNA replication, it can be considered a potential therapeutic target. We therefore performed an in silico screening and selected 18 small molecules (SMs) potentially interfering with ppUL44 homodimerization. Antiviral assays using recombinant HCMV TB4-UL83-YFP in the presence of the selected SMs led to the identification of four active compounds. The most active one, B3, also efficiently inhibited HCMV AD169 strain in plaque reduction assays and impaired replication of an AD169-GFP reporter virus and its ganciclovir-resistant counterpart to a similar extent. As assessed by Western blotting experiments, B3 specifically reduced viral gene expression starting from 48 h post infection, consistent with the inhibition of viral DNA synthesis measured by qPCR starting from 72 h post infection. Therefore, our data suggest that inhibition of ppUL44 dimerization could represent a new class of HCMV inhibitors, complementary to those targeting the DNA polymerase catalytic subunit or the viral terminase complex.
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Affiliation(s)
- Hanieh Ghassabian
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
| | | | - Martina Timmoneri
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
| | - Beatrice Mercorelli
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
| | - Arianna Loregian
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
| | - Gualtiero Alvisi
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy; (H.G.); (M.T.); (B.M.); (A.L.); (G.P.)
- Correspondence:
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Di Antonio V, Palù G, Alvisi G. Live-Cell Analysis of Human Cytomegalovirus DNA Polymerase Holoenzyme Assembly by Resonance Energy Transfer Methods. Microorganisms 2021; 9:microorganisms9050928. [PMID: 33925913 PMCID: PMC8146696 DOI: 10.3390/microorganisms9050928] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/21/2021] [Accepted: 04/22/2021] [Indexed: 12/18/2022] Open
Abstract
Human cytomegalovirus (HCMV) genome replication is a complex and still not completely understood process mediated by the highly coordinated interaction of host and viral products. Among the latter, six different proteins form the viral replication complex: a single-stranded DNA binding protein, a trimeric primase/helicase complex and a two subunit DNA polymerase holoenzyme, which in turn contains a catalytic subunit, pUL54, and a dimeric processivity factor ppUL44. Being absolutely required for viral replication and representing potential therapeutic targets, both the ppUL44-pUL54 interaction and ppUL44 homodimerization have been largely characterized from structural, functional and biochemical points of view. We applied fluorescence and bioluminescence resonance energy transfer (FRET and BRET) assays to investigate such processes in living cells. Both interactions occur with similar affinities and can take place both in the nucleus and in the cytoplasm. Importantly, single amino acid substitutions in different ppUL44 domains selectively affect its dimerization or ability to interact with pUL54. Intriguingly, substitutions preventing DNA binding of ppUL44 influence the BRETmax of protein-protein interactions, implying that binding to dsDNA induces conformational changes both in the ppUL44 homodimer and in the DNA polymerase holoenzyme. We also compared transiently and stably ppUL44-expressing cells in BRET inhibition assays. Transient expression of the BRET donor allowed inhibition of both ppUL44 dimerization and formation of the DNA polymerase holoenzyme, upon overexpression of FLAG-tagged ppUL44 as a competitor. Our approach could be useful both to monitor the dynamics of assembly of the HCMV DNA polymerase holoenzyme and for antiviral drug discovery.
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Herpesvirus DNA polymerase processivity factors: Not just for DNA synthesis. Virus Res 2021; 298:198394. [PMID: 33775751 DOI: 10.1016/j.virusres.2021.198394] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 11/22/2022]
Abstract
Herpesviruses encode multiple proteins directly involved in DNA replication, including a DNA polymerase and a DNA polymerase processivity factor. As the name implies, these processivity factors are essential for efficient DNA synthesis, however they also make additional contributions to DNA replication, as well as having novel roles in transcription and modulation of host processes. Here we review the mechanisms by which DNA polymerase processivity factors from all three families of mammalian herpesviruses contribute to viral DNA replication as well as to additional aspects of viral infection.
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7
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Elbadawy HM, Mohammed Abdul MI, Aljuhani N, Vitiello A, Ciccarese F, Shaker MA, Eltahir HM, Palù G, Di Antonio V, Ghassabian H, Del Vecchio C, Salata C, Franchin E, Ponterio E, Bahashwan S, Thabet K, Abouzied MM, Shehata AM, Parolin C, Calistri A, Alvisi G. Generation of Combinatorial Lentiviral Vectors Expressing Multiple Anti-Hepatitis C Virus shRNAs and Their Validation on a Novel HCV Replicon Double Reporter Cell Line. Viruses 2020; 12:v12091044. [PMID: 32962117 PMCID: PMC7551853 DOI: 10.3390/v12091044] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 12/12/2022] Open
Abstract
Despite the introduction of directly acting antivirals (DAAs), for the treatment of hepatitis C virus (HCV) infection, their cost, patient compliance, and viral resistance are still important issues to be considered. Here, we describe the generation of a novel JFH1-based HCV subgenomic replicon double reporter cell line suitable for testing different antiviral drugs and therapeutic interventions. This cells line allowed a rapid and accurate quantification of cell growth/viability and HCV RNA replication, thus discriminating specific from unspecific antiviral effects caused by DAAs or cytotoxic compounds, respectively. By correlating cell number and virus replication, we could confirm the inhibitory effect on the latter of cell over confluency and characterize an array of lentiviral vectors expressing single, double, or triple cassettes containing different combinations of short hairpin (sh)RNAs, targeting both highly conserved viral genome sequences and cellular factors crucial for HCV replication. While all vectors were effective in reducing HCV replication, the ones targeting viral sequences displayed a stronger antiviral effect, without significant cytopathic effects. Such combinatorial platforms as well as the developed double reporter cell line might find application both in setting-up anti-HCV gene therapy approaches and in studies aimed at further dissecting the viral biology/pathogenesis of infection.
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Affiliation(s)
- Hossein M. Elbadawy
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
| | - Mohi I. Mohammed Abdul
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
- Correspondence: (M.I.M.A.); (A.C.); (G.A.)
| | - Naif Aljuhani
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
| | - Adriana Vitiello
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Francesco Ciccarese
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
- Immunology and Molecular Oncology Unit, Veneto Institute of Oncology IOV-IRCCS, 35128 Padua, Italy
| | - Mohamed A. Shaker
- Pharmaceutics and Pharmaceutical Technology Department, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia;
- Pharmaceutics Department, Faculty of Pharmacy, Helwan University, Cairo 11795, Egypt
| | - Heba M. Eltahir
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Veronica Di Antonio
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
- Immunology and Molecular Oncology Unit, Veneto Institute of Oncology IOV-IRCCS, 35128 Padua, Italy
| | - Hanieh Ghassabian
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Claudia Del Vecchio
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Cristiano Salata
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Elisa Franchin
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Eleonora Ponterio
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
- Fondazione Policlinico Universitario "A. Gemelli"—I.R.C.C.S., 00168 Rome, Italy
| | - Saleh Bahashwan
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
| | - Khaled Thabet
- Department of Biochemistry, Faculty of Pharmacy, Minia University, Minia 61519, Egypt;
| | - Mekky M. Abouzied
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
- Department of Biochemistry, Faculty of Pharmacy, Minia University, Minia 61519, Egypt;
| | - Ahmed M. Shehata
- Department of Pharmacology and Toxicology, College of Pharmacy, Taibah University, Almadinah Almunawwarah 41477, Saudi Arabia; (H.M.E.); (N.A.); (H.M.E.); (S.B.); (M.M.A.); (A.M.S.)
- Department of Pharmacology and toxicology, Faculty of Pharmacy, Beni-Suef University, Beni-Suef 62511, Egypt
| | - Cristina Parolin
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
| | - Arianna Calistri
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
- Correspondence: (M.I.M.A.); (A.C.); (G.A.)
| | - Gualtiero Alvisi
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy; (A.V.); (F.C.); (G.P.); (V.D.A.); (H.G.); (C.D.V.); (C.S.); (E.F.); (E.P.); (C.P.)
- Correspondence: (M.I.M.A.); (A.C.); (G.A.)
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Ivermectin Inhibits Bovine Herpesvirus 1 DNA Polymerase Nuclear Import and Interferes with Viral Replication. Microorganisms 2020; 8:microorganisms8030409. [PMID: 32183205 PMCID: PMC7143239 DOI: 10.3390/microorganisms8030409] [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: 02/19/2020] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 12/22/2022] Open
Abstract
Bovine herpesvirus1 (BoHV-1) is a major bovine pathogen. Despite several vaccines being available to prevent viral infection, outbreaks are frequent and cause important economic consequences worldwide. The development of new antiviral drugs is therefore highly desirable. In this context, viral genome replication represents a potential target for therapeutic intervention. BoHV-1 genome is a dsDNA molecule whose replication takes place in the nuclei of infected cells and is mediated by a viral encoded DNA polymerase holoenzyme. Here, we studied the physical interaction and subcellular localization of BoHV-1 DNA polymerase subunits in cells for the first time. By means of co-immunoprecipitation and confocal laser scanning microscopy (CLSM) experiments, we could show that the processivity factor of the DNA polymerase pUL42 is capable of being autonomously transported into the nucleus, whereas the catalytic subunit pUL30 is not. Accordingly, a putative classic NLS (cNLS) was identified on pUL42 but not on pUL30. Importantly, both proteins could interact in the absence of other viral proteins and their co-expression resulted in accumulation of UL30 to the cell nucleus. Treatment of cells with Ivermectin, an anti-parasitic drug which has been recently identified as an inhibitor of importin α/β-dependent nuclear transport, reduced UL42 nuclear import and specifically reduced BoHV-1 replication in a dose-dependent manner, while virus attachment and entry into cells were not affected. Therefore, this study provides a new option of antiviral therapy for BoHV-1 infection with Ivermectin.
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Human Cytomegalovirus DNA Polymerase Subunit UL44 Antagonizes Antiviral Immune Responses by Suppressing IRF3- and NF-κB-Mediated Transcription. J Virol 2019; 93:JVI.00181-19. [PMID: 30867312 DOI: 10.1128/jvi.00181-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 03/02/2019] [Indexed: 01/09/2023] Open
Abstract
Innate immunity is the first line of host defense against viral invasion. The induction of type I interferons (IFNs) and inflammatory cytokines is essential to host antiviral immune responses, which are also key targets of viral immune evasion. Human cytomegalovirus (HCMV) can establish long-term latent infections, in which immune evasion is a pivotal step. In this study, we identified HCMV protein UL44, a DNA polymerase processivity factor, as an inhibitor of the interferon regulatory factor 3 (IRF3)- and NF-κB-dependent antiviral response. Ectopic expression of UL44 inhibited HCMV-triggered induction of downstream effector genes and enhanced viral replication. Conversely, knockdown of UL44 potentiated HCMV-triggered induction of downstream antiviral genes. UL44 interacted with IRF3 and p65, and it inhibited the binding of IRF3 and NF-κB to the promoters of their downstream antiviral genes. These findings reveal an important mechanism of immune evasion by HCMV at the transcriptional level.IMPORTANCE Induction of type I IFNs and inflammatory cytokines plays pivotal roles in host antiviral innate immune responses. Viruses have evolved various mechanisms to interfere with these processes. HCMV causes severe ailments in immunodeficient populations and is a major cause of birth defects. It has been shown that HCMV antagonizes host innate immune defenses, which is important for establishing immune evasion and latent infection. In this study, we identified the HCMV DNA polymerase subunit UL44 as a suppressor of antiviral innate immune responses. Overexpression of UL44 impaired HCMV-triggered induction of type I IFNs and other antiviral genes and thus potentiated viral replication, whereas UL44 deficiency showed opposite effects. Mechanistic studies indicated that UL44 acts by inhibiting the binding of IRF3 and NF-κB to the promoters of downstream antiviral genes. These findings defined an important mechanism of HCMV immune evasion at the transcriptional level, which may provide a therapeutic target for the treatment of HCMV infection.
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Salvi A, Vezzoli M, Busatto S, Paolini L, Faranda T, Abeni E, Caracausi M, Antonaros F, Piovesan A, Locatelli C, Cocchi G, Alvisi G, De Petro G, Ricotta D, Bergese P, Radeghieri A. Analysis of a nanoparticle‑enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis. Int J Mol Med 2019; 43:2303-2318. [PMID: 31017260 PMCID: PMC6488180 DOI: 10.3892/ijmm.2019.4158] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 03/20/2019] [Indexed: 12/12/2022] Open
Abstract
Down syndrome (DS) is caused by the presence of part or all of a third copy of chromosome 21. DS is associated with several phenotypes, including intellectual disability, congenital heart disease, childhood leukemia and immune defects. Specific microRNAs (miRNAs/miR) have been described to be associated with DS, although none of them so far have been unequivocally linked to the pathology. The present study focuses to the best of our knowledge for the first time on the miRNAs contained in nanosized RNA carriers circulating in the blood. Fractions enriched in nanosized RNA-carriers were separated from the plasma of young participants with DS and their non-trisomic siblings and miRNAs were extracted. A microarray-based analysis on a small cohort of samples led to the identification of the three most abundant miRNAs, namely miR-16-5p, miR-99b-5p and miR-144-3p. These miRNAs were then profiled for 15 pairs of DS and non-trisomic sibling couples by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Results identified a clear differential expression trend of these miRNAs in DS with respect to their non-trisomic siblings and gene ontology analysis pointed to their potential role in a number of typical DS features, including 'nervous system development', 'neuronal cell body' and certain forms of 'leukemia'. Finally, these expression levels were associated with certain typical quantitative and qualitative clinical features of DS. These results contribute to the efforts in defining the DS-associated pathogenic mechanisms and emphasize the importance of properly stratifying the miRNA fluid vehicles in order to probe biomolecules that are otherwise hidden and/or not accessible to (standard) analysis.
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Affiliation(s)
- Alessandro Salvi
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Marika Vezzoli
- Unit of Biostatistics, Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Sara Busatto
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Lucia Paolini
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Teresa Faranda
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Edoardo Abeni
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Maria Caracausi
- Department of Experimental, Diagnostic and Specialty Medicine (DIMES), Unit of Histology, Embryology and Applied Biology, University of Bologna, I‑40138 Bologna, Italy
| | - Francesca Antonaros
- CSGI, Research Center for Colloids and Nanoscience, Sesto Fiorentino, I‑50019 Florence, Italy
| | - Allison Piovesan
- CSGI, Research Center for Colloids and Nanoscience, Sesto Fiorentino, I‑50019 Florence, Italy
| | - Chiara Locatelli
- Neonatology Unit, St. Orsola‑Malpighi Polyclinic, I‑40138 Bologna, Italy
| | - Guido Cocchi
- Neonatology Unit, St. Orsola‑Malpighi Polyclinic, I‑40138 Bologna, Italy
| | - Gualtiero Alvisi
- Department of Molecular Medicine, University of Padua, I‑35121 Padua, Italy
| | - Giuseppina De Petro
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Doris Ricotta
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Paolo Bergese
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
| | - Annalisa Radeghieri
- Department of Molecular and Translational Medicine, University of Brescia, I‑25123 Brescia, Italy
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11
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Contribution of the residue at position 4 within classical nuclear localization signals to modulating interaction with importins and nuclear targeting. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1114-1129. [DOI: 10.1016/j.bbamcr.2018.05.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 05/02/2018] [Accepted: 05/04/2018] [Indexed: 01/08/2023]
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12
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Intersectin goes nuclear: secret life of an endocytic protein. Biochem J 2018; 475:1455-1472. [PMID: 29599122 DOI: 10.1042/bcj20170897] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/22/2018] [Accepted: 03/26/2018] [Indexed: 01/22/2023]
Abstract
Intersectin 1-short (ITSN1-s) is a 1220 amino acid ubiquitously expressed scaffold protein presenting a multidomain structure that allows to spatiotemporally regulate the functional interaction of a plethora of proteins. Besides its well-established role in endocytosis, ITSN1-s is involved in the regulation of cell signaling and is implicated in tumorigenesis processes, although the signaling pathways involved are still poorly understood. Here, we identify ITSN1-s as a nucleocytoplasmic trafficking protein. We show that, by binding to importin (IMP)α, a small fraction of ITSN1-s localizes in the cell nucleus at the steady state, where it preferentially associates with the nuclear envelope and interacts with lamin A/C. However, upon pharmacological ablation of chromosome region maintenance 1 (CRM-1)-dependent nuclear export pathway, the protein accumulates into the nucleus, thus revealing its moonlighting nature. Analysis of deletion mutants revealed that the coiled coil (CC) and Src homology (SH3) regions play the major role in its nucleocytoplasmic shuttling. While no evidence of nuclear localization signal (NLS) was detected in the CC region, a functional bipartite NLS was identified within the SH3D region of ITSN1-s (RKKNPGGWWEGELQARGKKRQIGW-1127), capable of conferring energy-dependent nuclear accumulation to reporter proteins and whose mutational ablation affects nuclear import of the whole SH3 region. Thus, ITSN1-s is an endocytic protein, which shuttles between the nucleus and the cytoplasm in a CRM-1- and IMPα-dependent fashion.
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13
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Trevisan M, Di Antonio V, Radeghieri A, Palù G, Ghildyal R, Alvisi G. Molecular Requirements for Self-Interaction of the Respiratory Syncytial Virus Matrix Protein in Living Mammalian Cells. Viruses 2018; 10:v10030109. [PMID: 29510513 PMCID: PMC5869502 DOI: 10.3390/v10030109] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 02/26/2018] [Accepted: 02/28/2018] [Indexed: 02/07/2023] Open
Abstract
Respiratory syncytial virus (RSV) is an important human pathogen, which infects respiratory tract epithelial cells causing bronchiolitis and pneumonia in children and the elderly. Recent studies have linked RSV matrix (M) ability to self-interaction and viral budding. However, RSV M has been crystalized both as a monomer and a dimer, and no formal proof exists to date that it forms dimers in cells. Here, by using a combination of confocal laser scanning microscopy and bioluminescent resonant energy transfer applied to differently tagged deletion mutants of RSV M, we show that the protein can self-interact in living mammalian cells and that both the N and C-terminus of the protein are strictly required for the process, consistent with the reported dimeric crystal structure.
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Affiliation(s)
- Marta Trevisan
- Department of Molecular Medicine, University of Padua, Padua 35121, Italy.
| | | | - Annalisa Radeghieri
- Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy.
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padua, Padua 35121, Italy.
| | - Reena Ghildyal
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra 2617, Australia.
| | - Gualtiero Alvisi
- Department of Molecular Medicine, University of Padua, Padua 35121, Italy.
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14
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Yu X, Shahriari S, Li HM, Ghildyal R. Measles Virus Matrix Protein Inhibits Host Cell Transcription. PLoS One 2016; 11:e0161360. [PMID: 27551716 PMCID: PMC4994966 DOI: 10.1371/journal.pone.0161360] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 07/06/2016] [Indexed: 12/22/2022] Open
Abstract
Measles virus (MeV) is a highly contagious virus that still causes annual epidemics in developing countries despite the availability of a safe and effective vaccine. Additionally, importation from endemic countries causes frequent outbreaks in countries where it has been eliminated. The M protein of MeV plays a key role in virus assembly and cytopathogenesis; interestingly, M is localised in nucleus, cytoplasm and membranes of infected cells. We have used transient expression of M in transfected cells and in-cell transcription assays to show that only some MeV M localizes to the nucleus, in addition to cell membranes and the cytoplasm as previously described, and can inhibit cellular transcription via binding to nuclear factors. Additionally, MeV M was able to inhibit in vitro transcription in a dose-dependent manner. Importantly, a proportion of M is also localized to nucleus of MeV infected cells at early times in infection, correlating with inhibition of cellular transcription. Our data show, for the first time, that MeV M may play a role early in infection by inhibiting host cell transcription.
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Affiliation(s)
- Xuelian Yu
- Section of Epidemiology & Statistics, Department of Public Health, Xinjiang Medical University, 393 XinYi Road, Urumqi, PR China
| | - Shadi Shahriari
- Respiratory Virology Group, Centre for Research in Therapeutic Solutions, Faculty of ESTeM, University of Canberra, Bruce, ACT 2617, Canberra, Australia
| | - Hong-Mei Li
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Parade, Melbourne, VIC 3800, Australia
| | - Reena Ghildyal
- Respiratory Virology Group, Centre for Research in Therapeutic Solutions, Faculty of ESTeM, University of Canberra, Bruce, ACT 2617, Canberra, Australia
- * E-mail:
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15
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Naing Z, Webel R, Hamilton S, Schmeiser C, Scott G, Marschall M, Rawlinson W. Stimulatory effects of human cytomegalovirus tegument protein pp71 lead to increased expression of CCL2 (monocyte chemotactic protein-1) during infection. J Gen Virol 2015; 96:1855-62. [PMID: 25711967 DOI: 10.1099/vir.0.000101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human cytomegalovirus (CMV) is the most common infectious cause of congenital birth defects in developed countries. Studies of infected amniotic fluid and placentae show CMV infection leads to a pro-inflammatory shift in cytokine profiles with implications for pathogenesis of foetal disease. ELISA, immunofluorescence and real-time-PCR assays were used to investigate CCL2 (monocyte chemotactic protein-1) and TNF-α changes following CMV infection of human fibroblasts, as well as following transient expression of CMV gene products in HeLa cells. Infection of human fibroblasts with CMV AD169 resulted in increased cytoplasmic and extracellular expression of CCL2 during early stages of infection, followed by marked downregulation of the chemokine at late times. Induction of CCL2 was not observed with CMV clinical strain Merlin, consistent with the postulated immune-evasion potential of this genetically intact WT strain. Comparison between live and UV-irradiated virus infections showed that changes in CCL2 levels were a direct response to active CMV replication. There were no significant changes in TNF-α expression during a parallel time-course of CMV infection. In transient transfection assays, overexpression of CMV tegument protein pp71 resulted in intracellular and extracellular upregulation of CCL2 protein. mRNA analysis showed that pp71-induced elevation in CCL2 was mediated through transcriptional upregulation. The data showed that CMV-induced upregulation of CCL2 during early stages of infection was mediated, at least in part, by stimulation of viral pp71, which may contribute to viral pathogenesis through enhanced virus dissemination.
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Affiliation(s)
- Zin Naing
- 1Virology Research Laboratory, Department of Microbiology, South Eastern Area Laboratory Services, Prince of Wales Hospital, Sydney, NSW, Australia 2School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia 3Australian Centre for Perinatal Science, University of New South Wales, Sydney, NSW, Australia
| | - Rike Webel
- 4Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Stuart Hamilton
- 1Virology Research Laboratory, Department of Microbiology, South Eastern Area Laboratory Services, Prince of Wales Hospital, Sydney, NSW, Australia 5School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Cathrin Schmeiser
- 4Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Gillian Scott
- 1Virology Research Laboratory, Department of Microbiology, South Eastern Area Laboratory Services, Prince of Wales Hospital, Sydney, NSW, Australia 5School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Manfred Marschall
- 4Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, Erlangen, Germany
| | - William Rawlinson
- 3Australian Centre for Perinatal Science, University of New South Wales, Sydney, NSW, Australia 2School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia 1Virology Research Laboratory, Department of Microbiology, South Eastern Area Laboratory Services, Prince of Wales Hospital, Sydney, NSW, Australia
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16
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Regulated transport into the nucleus of herpesviridae DNA replication core proteins. Viruses 2013; 5:2210-34. [PMID: 24064794 PMCID: PMC3798897 DOI: 10.3390/v5092210] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 12/11/2022] Open
Abstract
The Herpesvirdae family comprises several major human pathogens belonging to three distinct subfamilies. Their double stranded DNA genome is replicated in the nuclei of infected cells by a number of host and viral products. Among the latter the viral replication complex, whose activity is strictly required for viral replication, is composed of six different polypeptides, including a two-subunit DNA polymerase holoenzyme, a trimeric primase/helicase complex and a single stranded DNA binding protein. The study of herpesviral DNA replication machinery is extremely important, both because it provides an excellent model to understand processes related to eukaryotic DNA replication and it has important implications for the development of highly needed antiviral agents. Even though all known herpesviruses utilize very similar mechanisms for amplification of their genomes, the nuclear import of the replication complex components appears to be a heterogeneous and highly regulated process to ensure the correct spatiotemporal localization of each protein. The nuclear transport process of these enzymes is controlled by three mechanisms, typifying the main processes through which protein nuclear import is generally regulated in eukaryotic cells. These include cargo post-translational modification-based recognition by the intracellular transporters, piggy-back events allowing coordinated nuclear import of multimeric holoenzymes, and chaperone-assisted nuclear import of specific subunits. In this review we summarize these mechanisms and discuss potential implications for the development of antiviral compounds aimed at inhibiting the Herpesvirus life cycle by targeting nuclear import of the Herpesvirus DNA replicating enzymes.
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17
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Avanzi S, Leoni V, Rotola A, Alviano F, Solimando L, Lanzoni G, Bonsi L, Di Luca D, Marchionni C, Alvisi G, Ripalti A. Susceptibility of human placenta derived mesenchymal stromal/stem cells to human herpesviruses infection. PLoS One 2013; 8:e71412. [PMID: 23940750 PMCID: PMC3734067 DOI: 10.1371/journal.pone.0071412] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 07/01/2013] [Indexed: 12/11/2022] Open
Abstract
Fetal membranes (FM) derived mesenchymal stromal/stem cells (MSCs) are higher in number, expansion and differentiation abilities compared with those obtained from adult tissues, including bone marrow. Upon systemic administration, ex vivo expanded FM-MSCs preferentially home to damaged tissues promoting regenerative processes through their unique biological properties. These characteristics together with their immune-privileged nature and immune suppressive activity, a low infection rate and young age of placenta compared to other sources of SCs make FM-MSCs an attractive target for cell-based therapy and a valuable tool in regenerative medicine, currently being evaluated in clinical trials. In the present study we investigated the permissivity of FM-MSCs to all members of the human Herpesviridae family, an issue which is relevant to their purification, propagation, conservation and therapeutic use, as well as to their potential role in the vertical transmission of viral agents to the fetus and to their potential viral vector-mediated genetic modification. We present here evidence that FM-MSCs are fully permissive to infection with Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), Varicella zoster virus (VZV), and Human Cytomegalovirus (HCMV), but not with Epstein-Barr virus (EBV), Human Herpesvirus-6, 7 and 8 (HHV-6, 7, 8) although these viruses are capable of entering FM-MSCs and transient, limited viral gene expression occurs. Our findings therefore strongly suggest that FM-MSCs should be screened for the presence of herpesviruses before xenotransplantation. In addition, they suggest that herpesviruses may be indicated as viral vectors for gene expression in MSCs both in gene therapy applications and in the selective induction of differentiation.
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Affiliation(s)
- Simone Avanzi
- Department of Oncology, Haematology and Laboratory Medicine, Operative Unit of Microbiology, A. O-U. di Bologna Policlinico S. Orsola-Malpighi, Bologna, Italy
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18
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The human cytomegalovirus DNA polymerase processivity factor UL44 is modified by SUMO in a DNA-dependent manner. PLoS One 2012; 7:e49630. [PMID: 23166733 PMCID: PMC3499415 DOI: 10.1371/journal.pone.0049630] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/11/2012] [Indexed: 12/22/2022] Open
Abstract
During the replication of human cytomegalovirus (HCMV) genome, the viral DNA polymerase subunit UL44 plays a key role, as by binding both DNA and the polymerase catalytic subunit it confers processivity to the holoenzyme. However, several lines of evidence suggest that UL44 might have additional roles during virus life cycle. To shed light on this, we searched for cellular partners of UL44 by yeast two-hybrid screenings. Intriguingly, we discovered the interaction of UL44 with Ubc9, an enzyme involved in the covalent conjugation of SUMO (Small Ubiquitin-related MOdifier) to cellular and viral proteins. We found that UL44 can be extensively sumoylated not only in a cell-free system and in transfected cells, but also in HCMV-infected cells, in which about 50% of the protein resulted to be modified at late times post-infection, when viral genome replication is accomplished. Mass spectrometry studies revealed that UL44 possesses multiple SUMO target sites, located throughout the protein. Remarkably, we observed that binding of UL44 to DNA greatly stimulates its sumoylation both in vitro and in vivo. In addition, we showed that overexpression of SUMO alters the intranuclear distribution of UL44 in HCMV-infected cells, and enhances both virus production and DNA replication, arguing for an important role for sumoylation in HCMV life cycle and UL44 function(s). These data report for the first time the sumoylation of a viral processivity factor and show that there is a functional interplay between the HCMV UL44 protein and the cellular sumoylation system.
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19
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Ranneberg-Nilsen T, Rollag H, Slettebakk R, Backe PH, Olsen Ø, Luna L, Bjørås M. The chromatin remodeling factor SMARCB1 forms a complex with human cytomegalovirus proteins UL114 and UL44. PLoS One 2012; 7:e34119. [PMID: 22479537 PMCID: PMC3313996 DOI: 10.1371/journal.pone.0034119] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 02/22/2012] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Human cytomegalovirus (HCMV) uracil DNA glycosylase, UL114, is required for efficient viral DNA replication. Presumably, UL114 functions as a structural partner to other factors of the DNA-replication machinery and not as a DNA repair protein. UL114 binds UL44 (HCMV processivity factor) and UL54 (HCMV-DNA-polymerase). In the present study we have searched for cellular partners of UL114. METHODOLOGY/PRINCIPAL FINDINGS In a yeast two-hybrid screen SMARCB1, a factor of the SWI/SNF chromatin remodeling complex, was found to be an interacting partner of UL114. This interaction was confirmed in vitro by co-immunoprecipitation and pull-down. Immunofluorescence microscopy revealed that SMARCB1 along with BRG-1, BAF170 and BAF155, which are the core SWI/SNF components required for efficient chromatin remodeling, were present in virus replication foci 24-48 hours post infection (hpi). Furthermore a direct interaction was also demonstrated for SMARCB1 and UL44. CONCLUSIONS/SIGNIFICANCE The core SWI/SNF factors required for efficient chromatin remodeling are present in the HCMV replication foci throughout infection. The proteins UL44 and UL114 interact with SMARCB1 and may participate in the recruitment of the SWI/SNF complex to the chromatinized virus DNA. Thus, the presence of the SWI/SNF chromatin remodeling complex in replication foci and its association with UL114 and with UL44 might imply its involvement in different DNA transactions.
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Affiliation(s)
- Toril Ranneberg-Nilsen
- Department of Microbiology, University of Oslo and Oslo University Hospital HF, Oslo, Norway
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20
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Sites and roles of phosphorylation of the human cytomegalovirus DNA polymerase subunit UL44. Virology 2011; 417:268-80. [PMID: 21784501 DOI: 10.1016/j.virol.2011.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 04/12/2011] [Accepted: 06/11/2011] [Indexed: 12/27/2022]
Abstract
The human cytomegalovirus DNA polymerase subunit UL44 is a phosphoprotein, but its sites and roles of phosphorylation have not been investigated. We compared sites of phosphorylation of UL44 in vitro by the viral protein kinase UL97 and cyclin-dependent kinase 1 with those in infected cells. Transient treatment of infected cells with a UL97 inhibitor greatly reduced labeling of two minor UL44 phosphopeptides. Viruses containing alanine substitutions of most UL44 residues that are phosphorylated in infected cells exhibited at most modest effects on viral DNA synthesis and yield. However, substitution of highly phosphorylated sites adjacent to the nuclear localization signal abolished viral replication. The results taken together are consistent with UL44 being phosphorylated directly by UL97 during infection, and a crucial role for phosphorylation-mediated nuclear localization of UL44 for viral replication, but lend little support to the widely held hypothesis that UL97-mediated phosphorylation of UL44 is crucial for viral DNA synthesis.
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21
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Alvisi G, Marin O, Pari G, Mancini M, Avanzi S, Loregian A, Jans DA, Ripalti A. Multiple phosphorylation sites at the C-terminus regulate nuclear import of HCMV DNA polymerase processivity factor ppUL44. Virology 2011; 417:259-67. [PMID: 21741668 DOI: 10.1016/j.virol.2011.06.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/13/2011] [Accepted: 06/14/2011] [Indexed: 12/31/2022]
Abstract
The processivity factor of human cytomegalovirus DNA polymerase, phosphoprotein ppUL44, is essential for viral replication. During viral infection ppUL44 is phosphorylated by the viral kinase pUL97, but neither the target residues on ppUL44 nor the effect of phosphorylation on ppUL44's activity are known. We report here that ppUL44 is phosphorylated when transiently expressed in mammalian cells and coimmunoprecipitates with cellular kinases. Of three potential phosphorylation sites (S413, S415, S418) located upstream of ppUL44's nuclear localization signal (NLS) and one (T427) within the NLS itself, protein kinase CK2 (CK2) specifically phosphorylates S413, to trigger a cascade of phosphorylation of S418 and S415 by CK1 and CK2, respectively. Negative charge at the CK2/CK1 target serine residues facilitates optimal nuclear accumulation of ppUL44, whereas negative charge on T427, a potential cyclin-dependent 1 phosphorylation site, strongly decreases nuclear accumulation. Thus, nuclear transport of ppUL44 is finely tuned during viral infection through complex phosphorylation events.
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Affiliation(s)
- Gualtiero Alvisi
- Department of Hematology and Oncology Lorenzo e Ariosto Seràgnoli, University of Bologna, Medical School, Bologna, Italy.
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22
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Wang Y, Sathish N, Hollow C, Yuan Y. Functional characterization of Kaposi's sarcoma-associated herpesvirus open reading frame K8 by bacterial artificial chromosome-based mutagenesis. J Virol 2011; 85:1943-57. [PMID: 21159864 PMCID: PMC3067771 DOI: 10.1128/jvi.02060-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 12/06/2010] [Indexed: 01/09/2023] Open
Abstract
The open reading frame K8 of Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a basic leucine zipper (bZip) protein that binds to the origin of viral DNA replication and is an integral component of viral lytic DNA replication complex. Moreover, K8 physically interacts with replication and transcription activator (RTA) and represses its transactivation activity on several viral promoters. To investigate the role of this protein in viral life cycle, we constructed two K8-null recombinant mutant viruses (BAC-ΔK8 and BAC-stopK8) by using a bacterial artificial chromosome (BAC) system. Latent viral infection can be reconstituted in 293T and BJAB cells with wild-type and the K8-null recombinant viruses by introducing the cloned viral genomes into the cells. When the cells carrying these viruses were induced with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate, no significant difference was seen in overall viral gene expression between wild-type and K8-null viruses, with lytic DNA replication still active in the latter. However, 293T cells harboring K8-null mutant viruses, either BAC-ΔK8 or BAC-stopK8, displayed lower copy numbers of latent KSHV genome in comparison with wild-type viruses. Furthermore, although K8 deficiency appeared to not affect infectivity when K8-null viruses were used to infect 293T, primary human microvascular dermal endothelial and human foreskin fibroblast cells, they exhibited much lower viral genome copy numbers in all types of cell compared to wild-type viruses. Taken together, these data suggest a possible role of K8 in abortive lytic DNA replication occurring in early stages of de novo infection or in the maintenance of latent viral genomes.
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Affiliation(s)
- Yan Wang
- Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania 19104, Guanghua School of Stomatology and Institute of Human Virology, Sun Yat-Sen University, Guangzhou, China
| | - Narayanan Sathish
- Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania 19104, Guanghua School of Stomatology and Institute of Human Virology, Sun Yat-Sen University, Guangzhou, China
| | - Charles Hollow
- Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania 19104, Guanghua School of Stomatology and Institute of Human Virology, Sun Yat-Sen University, Guangzhou, China
| | - Yan Yuan
- Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania 19104, Guanghua School of Stomatology and Institute of Human Virology, Sun Yat-Sen University, Guangzhou, China
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Roth DM, Moseley GW, Pouton CW, Jans DA. Mechanism of microtubule-facilitated "fast track" nuclear import. J Biol Chem 2011; 286:14335-51. [PMID: 21339293 DOI: 10.1074/jbc.m110.210302] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Although the microtubule (MT) cytoskeleton has been shown to facilitate nuclear import of specific cancer-regulatory proteins including p53, retinoblastoma protein, and parathyroid hormone-related protein (PTHrP), the MT association sequences (MTASs) responsible and the nature of the interplay between MT-dependent and conventional importin (IMP)-dependent nuclear translocation are unknown. Here we used site-directed mutagenesis, live cell imaging, and direct IMP and MT binding assays to map the MTAS of PTHrP for the first time, finding that it is within a short modular region (residues 82-108) that overlaps with the IMPβ1-recognized nuclear localization signal (residues 66-108) of PTHrP. Importantly, fluorescence recovery after photobleaching experiments indicated that disruption of the MT network or mutation of the MTAS of PTHrP decreases the rate of nuclear import by 2-fold. Moreover, MTAS functions depend on mutual exclusivity of binding of PTHrP to MTs and IMPβ1 such that, following MT-dependent trafficking toward the nucleus, perinuclear PTHrP can be displaced from MTs by IMPβ1 prior to import into the nucleus. This is the first molecular definition of an MTAS that facilitates protein nuclear import as well as the first delineation of the mechanism whereby cargo is transferred directly from the cytoskeleton to the cellular nuclear import apparatus. The results have broad significance with respect to fundamental processes regulating cell physiology/transformation.
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Affiliation(s)
- Daniela Martino Roth
- Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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Tetrameric ring formation of Epstein-Barr virus polymerase processivity factor is crucial for viral replication. J Virol 2010; 84:12589-98. [PMID: 20926567 DOI: 10.1128/jvi.01394-10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Epstein-Barr virus BMRF1 DNA polymerase processivity factor, which is essential for viral genome replication, exists mainly as a C-shaped head-to-head homodimer but partly forms a ring-shaped tetramer through tail-to-tail association. Based on its molecular structure, several BMRF1 mutant viruses were constructed to examine their influence on viral replication. The R256E virus, which has a severely impaired capacity for DNA binding and polymerase processivity, failed to form replication compartments, resulting in interference of viral replication, while the C95E mutation, which impairs head-to-head contact in vitro, unexpectedly hardly affected the viral replication. Also, surprisingly, replication of the C206E virus, which is expected to have impairment of tail-to-tail contact, was severely restricted, although the mutant protein possesses the same in vitro biochemical activities as the wild type. Since the tail-to-tail contact surface is smaller than that of the head-to-head contact area, its contribution to ring formation might be essential for viral replication.
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The carboxy-terminal segment of the human cytomegalovirus DNA polymerase accessory subunit UL44 is crucial for viral replication. J Virol 2010; 84:11563-8. [PMID: 20739543 DOI: 10.1128/jvi.01033-10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The amino-terminal 290 residues of UL44, the presumed processivity factor of human cytomegalovirus DNA polymerase, possess all of the established biochemical activities of the full-length protein, while the carboxy-terminal 143 residues contain a nuclear localization signal (NLS). We found that although the amino-terminal domain was sufficient for origin-dependent synthesis in a transient-transfection assay, the carboxy-terminal segment was crucial for virus replication and for the formation of DNA replication compartments in infected cells, even when this segment was replaced with a simian virus 40 NLS that ensured nuclear localization. Our results suggest a role for this segment in viral DNA synthesis.
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