1
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Hasanshahi Z, Dehghani B, Hashempour A. Interaction Between Vpx and SAMHD1, Vital for SAMHD1 Inhibition. AIDS Res Hum Retroviruses 2024; 40:384-392. [PMID: 38084955 DOI: 10.1089/aid.2023.0052] [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] [Indexed: 12/28/2023] Open
Abstract
It was confirmed that the sterile alpha motif and HD domain 1 (SAMHD1) limits human immunodeficiency virus type 1 (HIV-1) replication. In contrast, viral protein x (Vpx) in HIV-2 and some simian immunodeficiency viruses can counteract this effect. The possible interaction between SAMHD1 and Vpx was suggested by previous studies; however, there are no data to confirm this interaction. Therefore, this study aimed to study the interaction between two proteins and the properties of Vpx protein for the first time using bioinformatic tools. Vpx and SAMHD1 sequences were obtained from the National Center for Biotechnology Information GenBank. Several software were used to define Vpx properties and the interaction between Vpx and different SAMHD1 isoforms. Our findings indicated the difference in interaction sites among different Vpx. However, in all Vpx proteins, this region is from amino acids 4 to 90. In addition, two regions (26-31 and 134-139) and two amino acids 425 and 429 in SAMHD1 are vital in the possible interaction. In addition, our analysis determined the physicochemical and immunological properties of the Vpx. Considering all factors, this study could confirm that Vpx interacts with SAMHD1, which could inhibit SAMHD1. Moreover, our findings can pave the way for future studies to express and purify Vpx in the laboratory and study this protein in vitro.
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Affiliation(s)
- Zahra Hasanshahi
- HIV/AIDS Research Center, Institute of Health, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Behzad Dehghani
- HIV/AIDS Research Center, Institute of Health, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Ava Hashempour
- HIV/AIDS Research Center, Institute of Health, Shiraz University of Medical Sciences, Shiraz, Iran
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2
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Yong D, Ahmad S, Mabanglo MF, Halabelian L, Schapira M, Ackloo S, Perveen S, Ghiabi P, Vedadi M. Development of Peptide Displacement Assays to Screen for Antagonists of DDB1 Interactions. Biochemistry 2024; 63:1297-1306. [PMID: 38729622 PMCID: PMC11112733 DOI: 10.1021/acs.biochem.4c00044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 04/01/2024] [Accepted: 04/17/2024] [Indexed: 05/12/2024]
Abstract
The DNA damage binding protein 1 (DDB1) is an essential component of protein complexes involved in DNA damage repair and the ubiquitin-proteasome system (UPS) for protein degradation. As an adaptor protein specific to Cullin-RING E3 ligases, DDB1 binds different receptors that poise protein substrates for ubiquitination and subsequent degradation by the 26S proteasome. Examples of DDB1-binding protein receptors are Cereblon (CRBN) and the WD-repeat containing DDB1- and CUL4-associated factors (DCAFs). Cognate substrates of CRBN and DCAFs are involved in cancer-related cellular processes or are mimicked by viruses to reprogram E3 ligases for the ubiquitination of antiviral host factors. Thus, disrupting interactions of DDB1 with receptor proteins might be an effective strategy for anticancer and antiviral drug discovery. Here, we developed fluorescence polarization (FP)-based peptide displacement assays that utilize full-length DDB1 and fluorescein isothiocyanate (FITC)-labeled peptide probes derived from the specific binding motifs of DDB1 interactors. A general FP-based assay condition applicable to diverse peptide probes was determined and optimized. Mutagenesis and biophysical analyses were then employed to identify the most suitable peptide probe. The FITC-DCAF15 L49A peptide binds DDB1 with a dissociation constant of 68 nM and can be displaced competitively by unlabeled peptides at sub-μM to low nM concentrations. These peptide displacement assays can be used to screen small molecule libraries to identify novel modulators that could specifically antagonize DDB1 interactions toward development of antiviral and cancer therapeutics.
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Affiliation(s)
- Darren Yong
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Shabbir Ahmad
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Mark F. Mabanglo
- Drug
Discovery Program, Ontario Institute for
Cancer Research, Toronto, Ontario M5G 0A3, Canada
| | - Levon Halabelian
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
- Department
of Pharmacology and Toxicology, University
of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Matthieu Schapira
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
- Department
of Pharmacology and Toxicology, University
of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Suzanne Ackloo
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Sumera Perveen
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Pegah Ghiabi
- Structural
Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, Canada
| | - Masoud Vedadi
- Drug
Discovery Program, Ontario Institute for
Cancer Research, Toronto, Ontario M5G 0A3, Canada
- Department
of Pharmacology and Toxicology, University
of Toronto, Toronto, Ontario M5S 1A8, Canada
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3
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Kapoor-Vazirani P, Rath SK, Liu X, Shu Z, Bowen NE, Chen Y, Haji-Seyed-Javadi R, Daddacha W, Minten EV, Danelia D, Farchi D, Duong DM, Seyfried NT, Deng X, Ortlund EA, Kim B, Yu DS. SAMHD1 deacetylation by SIRT1 promotes DNA end resection by facilitating DNA binding at double-strand breaks. Nat Commun 2022; 13:6707. [PMID: 36344525 PMCID: PMC9640623 DOI: 10.1038/s41467-022-34578-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 10/29/2022] [Indexed: 11/09/2022] Open
Abstract
Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) has a dNTPase-independent function in promoting DNA end resection to facilitate DNA double-strand break (DSB) repair by homologous recombination (HR); however, it is not known if upstream signaling events govern this activity. Here, we show that SAMHD1 is deacetylated by the SIRT1 sirtuin deacetylase, facilitating its binding with ssDNA at DSBs, to promote DNA end resection and HR. SIRT1 complexes with and deacetylates SAMHD1 at conserved lysine 354 (K354) specifically in response to DSBs. K354 deacetylation by SIRT1 promotes DNA end resection and HR but not SAMHD1 tetramerization or dNTPase activity. Mechanistically, K354 deacetylation by SIRT1 promotes SAMHD1 recruitment to DSBs and binding to ssDNA at DSBs, which in turn facilitates CtIP ssDNA binding, leading to promotion of genome integrity. These findings define a mechanism governing the dNTPase-independent resection function of SAMHD1 by SIRT1 deacetylation in promoting HR and genome stability.
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Affiliation(s)
- Priya Kapoor-Vazirani
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Sandip K Rath
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Xu Liu
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Zhen Shu
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Nicole E Bowen
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Yitong Chen
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Ramona Haji-Seyed-Javadi
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Waaqo Daddacha
- Department of Biochemistry and Molecular Biology, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA
| | - Elizabeth V Minten
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Diana Danelia
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Daniela Farchi
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Duc M Duong
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Nicholas T Seyfried
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Xingming Deng
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Eric A Ortlund
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Baek Kim
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - David S Yu
- Department of Radiation Oncology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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4
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Banchenko S, Krupp F, Gotthold C, Bürger J, Graziadei A, O’Reilly FJ, Sinn L, Ruda O, Rappsilber J, Spahn CMT, Mielke T, Taylor IA, Schwefel D. Structural insights into Cullin4-RING ubiquitin ligase remodelling by Vpr from simian immunodeficiency viruses. PLoS Pathog 2021; 17:e1009775. [PMID: 34339457 PMCID: PMC8360603 DOI: 10.1371/journal.ppat.1009775] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/12/2021] [Accepted: 07/02/2021] [Indexed: 12/21/2022] Open
Abstract
Viruses have evolved means to manipulate the host's ubiquitin-proteasome system, in order to down-regulate antiviral host factors. The Vpx/Vpr family of lentiviral accessory proteins usurp the substrate receptor DCAF1 of host Cullin4-RING ligases (CRL4), a family of modular ubiquitin ligases involved in DNA replication, DNA repair and cell cycle regulation. CRL4DCAF1 specificity modulation by Vpx and Vpr from certain simian immunodeficiency viruses (SIV) leads to recruitment, poly-ubiquitylation and subsequent proteasomal degradation of the host restriction factor SAMHD1, resulting in enhanced virus replication in differentiated cells. To unravel the mechanism of SIV Vpr-induced SAMHD1 ubiquitylation, we conducted integrative biochemical and structural analyses of the Vpr protein from SIVs infecting Cercopithecus cephus (SIVmus). X-ray crystallography reveals commonalities between SIVmus Vpr and other members of the Vpx/Vpr family with regard to DCAF1 interaction, while cryo-electron microscopy and cross-linking mass spectrometry highlight a divergent molecular mechanism of SAMHD1 recruitment. In addition, these studies demonstrate how SIVmus Vpr exploits the dynamic architecture of the multi-subunit CRL4DCAF1 assembly to optimise SAMHD1 ubiquitylation. Together, the present work provides detailed molecular insight into variability and species-specificity of the evolutionary arms race between host SAMHD1 restriction and lentiviral counteraction through Vpx/Vpr proteins.
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Affiliation(s)
- Sofia Banchenko
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Ferdinand Krupp
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Christine Gotthold
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Jörg Bürger
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
- Microscopy and Cryo-Electron Microscopy Service Group, Max-Planck-Institute for Molecular Genetics, Berlin, Germany
| | - Andrea Graziadei
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Francis J. O’Reilly
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Ludwig Sinn
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Olga Ruda
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Juri Rappsilber
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
- Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Christian M. T. Spahn
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
| | - Thorsten Mielke
- Microscopy and Cryo-Electron Microscopy Service Group, Max-Planck-Institute for Molecular Genetics, Berlin, Germany
| | - Ian A. Taylor
- Macromolecular Structure Laboratory, The Francis Crick Institute, London, United Kingdom
| | - David Schwefel
- Charité–Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Berlin, Germany
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5
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Thapa G, Bhattacharya A, Bhattacharya S. Dimeric Hold States of Anti-HIV Protein SAMHD1 are Redox Tunable. J Chem Inf Model 2020; 60:6377-6391. [PMID: 33135886 DOI: 10.1021/acs.jcim.0c00629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The sterile α motif and histidine-aspartate domain-containing protein 1 (or SAMHD1) is a human protein that restricts HIV-1 in select terminally differentiated cells of the immune system by acting as a triphosphohydrolase, lowering dNTP pools. The functionally active form of the protein has been reported to be a tetramer where adjacent monomers are linked by GTP-Mg+2-dNTP cross-bridges, although some studies have also suggested the existence of a dimeric form of this protein. In this in silico study, we have investigated the stability of SAMHD1 dimeric "hold states" as well as the role of intrachain disulfide bonds. We have found that dimeric-GTP bound SAMHD1 can exist as a viable meso-stable hold state with extensive motion in the C-terminal domain, which is quenched upon tetramer assembly. The redox switch comprised of residues C341, C350, and C522 was found to be linked to changes in the allosteric site, suggesting a mechanism for initiating tetramer disassembly. The disulfide state of the protein dimer (C341-S-S-C350 vs C341-S-S-C522) also plays a role in driving affinities for the allosteric dATP molecules. In sum, our results suggest a model wherein dimeric SAMHD1 exists as a "hold state" in the cytosol, ready to be activated by dATP concentrations, where the "tunability" of this activation is further regulated by the redox state of the enzyme.
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Affiliation(s)
- Gauri Thapa
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Akash Bhattacharya
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, United States
| | - Swati Bhattacharya
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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6
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Zhang Z, Zheng L, Yu Y, Wu J, Yang F, Xu Y, Guo Q, Wu X, Cao S, Cao L, Song X. Involvement of SAMHD1 in dNTP homeostasis and the maintenance of genomic integrity and oncotherapy (Review). Int J Oncol 2020; 56:879-888. [PMID: 32319570 DOI: 10.3892/ijo.2020.4988] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/07/2020] [Indexed: 11/06/2022] Open
Abstract
Sterile alpha motif and histidine/aspartic acid domain‑containing protein 1 (SAMHD1), the only deoxynucleotide triphosphate (dNTP) hydrolase in eukaryotes, plays a crucial role in regulating the dynamic balance and ratio of cellular dNTP pools. Furthermore, SAMHD1 has been reported to be involved in the pathological process of several diseases. Homozygous SAMHD1 mutations have been identified in immune system disorders, such as autoimmune disease Aicardi‑Goutières syndrome (AGS), whose primary pathogenesis is associated with the abnormal accumulation and disproportion of dNTPs. SAMHD1 is also considered to be an intrinsic virus‑restriction factor by suppressing the viral infection process, including reverse transcription, replication, packaging and transmission. In addition, SAMHD1 has been shown to promote genome integrity during homologous recombination following DNA damage, thus being considered a promising candidate for oncotherapy applications. The present review summarizes the molecular mechanisms of SAMHD1 regarding the regulation of dNTP homeostasis and DNA damage response. Additionally, its potential effects on tumorigenesis and oncotherapy are reported.
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Affiliation(s)
- Zhou Zhang
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Lixia Zheng
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Yang Yu
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Jinying Wu
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Fan Yang
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Yingxi Xu
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Qiqiang Guo
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Xuan Wu
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Sunrun Cao
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Liu Cao
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
| | - Xiaoyu Song
- College of Basic Medical Science, Institute of Translational Medicine, China Medical University, Shenyang, Liaoning 110122, P.R. China
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7
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Kueck T, Cassella E, Holler J, Kim B, Bieniasz PD. The aryl hydrocarbon receptor and interferon gamma generate antiviral states via transcriptional repression. eLife 2018; 7:38867. [PMID: 30132758 PMCID: PMC6120754 DOI: 10.7554/elife.38867] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 08/21/2018] [Indexed: 12/13/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor whose activation induces the expression of numerous genes, with many effects on cells. However, AhR activation is not known to affect the replication of viruses. We show that AhR activation in macrophages causes a block to HIV-1 and HSV-1 replication. We find that AhR activation transcriptionally represses cyclin-dependent kinase (CDK)1/2 and their associated cyclins, thereby reducing SAMHD1 phosphorylation, cellular dNTP levels and both HIV-1 and HSV-1 replication. Remarkably, a different antiviral stimulus, interferon gamma (IFN-γ), that induces a largely non-overlapping set of genes, also transcriptionally represses CDK1, CDK2 and their associated cyclins, resulting in similar dNTP depletion and antiviral effects. Concordantly, the SIV Vpx protein provides complete and partial resistance to the antiviral effects of AhR and IFN-γ, respectively. Thus, distinct antiviral signaling pathways converge on CDK/cyclin repression, causing inhibition of viral DNA synthesis and replication.
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Affiliation(s)
- Tonya Kueck
- Laboratory of Retrovirology, The Rockefeller University, New York, United States
| | - Elena Cassella
- Laboratory of Retrovirology, The Rockefeller University, New York, United States
| | - Jessica Holler
- Center for Drug Discovery, The Department of Pediatrics, Emory University, Atlanta, United States
| | - Baek Kim
- Center for Drug Discovery, The Department of Pediatrics, Emory University, Atlanta, United States.,Department of Pharmacy, Kyung Hee University, Seoul, South Korea
| | - Paul D Bieniasz
- Laboratory of Retrovirology, The Rockefeller University, New York, United States.,Howard Hughes Medical Institute, The Rockefeller University, New York, United States
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8
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Mauney CH, Hollis T. SAMHD1: Recurring roles in cell cycle, viral restriction, cancer, and innate immunity. Autoimmunity 2018; 51:96-110. [PMID: 29583030 PMCID: PMC6117824 DOI: 10.1080/08916934.2018.1454912] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 03/16/2018] [Indexed: 12/24/2022]
Abstract
Sterile alpha motif and histidine-aspartic acid domain-containing protein 1 (SAMHD1) is a deoxynucleotide triphosphate (dNTP) hydrolase that plays an important role in the homeostatic balance of cellular dNTPs. Its emerging role as an effector of innate immunity is affirmed by mutations in the SAMHD1 gene that cause the severe autoimmune disease, Aicardi-Goutieres syndrome (AGS) and that are linked to cancer. Additionally, SAMHD1 functions as a restriction factor for retroviruses, such as HIV. Here, we review the current biochemical and biological properties of the enzyme including its structure, activity, and regulation by post-translational modifications in the context of its cellular function. We outline open questions regarding the biology of SAMHD1 whose answers will be important for understanding its function as a regulator of cell cycle progression, genomic integrity, and in autoimmunity.
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Affiliation(s)
- Christopher H Mauney
- a Department of Biochemistry , Center for Structural Biology, Wake Forest School of Medicine , Winston Salem , NC , USA
| | - Thomas Hollis
- a Department of Biochemistry , Center for Structural Biology, Wake Forest School of Medicine , Winston Salem , NC , USA
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9
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Bakir TM. The role of SAMHD1 expression and its relation to HIV-2 (Vpx) gene production. Saudi Pharm J 2018; 26:903-908. [PMID: 30202235 PMCID: PMC6128726 DOI: 10.1016/j.jsps.2018.03.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 03/10/2018] [Indexed: 11/21/2022] Open
Abstract
SAMHD1 (sterile alpha motif and HD domain 1) is a protein that is found in myeloid cells, which restricts HIV1 replication. It depletes the de-oxy-nucleoside tri-phosphate (dNTPs) pool needed for a viral cDNA synthesis leading to inhibition of viral replication inside the cells. However, it does not restrict HIV2 replication in myeloid cells due to the presence of viral Vpx protein. Vpx is a virion-associated protein which augments viral infectivity and it only exists in HIV2 and it has been recently shown in Simian Immunodeficiency Virus (SIV) and which can induce degradation of SAMHD1 protein. This increases the amount of dNTPs for viral reverse transcription in cytoplasm and HIV infection. HIV2 reverse transcription is believed to be less active than HIV1 and this could be the reason for the absence of Vpx from HIV1. Protein expression and interaction between Vpx and SAMHD1 remains unclear. The interaction of SAMHD1 and HIV2-VPx patients' cells can be considered as a first step to help in the development for more effective anti-HIV drugs and possible novel intervention therapy in the future. Present review article provides comprehensive insights on the above issue. We performed a comprehensive literature search in the bibliographic database “Pubmed,” looking at studies discussing the SAMHDI and Vpx interactions.
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10
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Zhou X, DeLucia M, Hao C, Hrecka K, Monnie C, Skowronski J, Ahn J. HIV-1 Vpr protein directly loads helicase-like transcription factor (HLTF) onto the CRL4-DCAF1 E3 ubiquitin ligase. J Biol Chem 2017; 292:21117-21127. [PMID: 29079575 DOI: 10.1074/jbc.m117.798801] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 10/23/2017] [Indexed: 11/06/2022] Open
Abstract
The viral protein R (Vpr) is an accessory virulence factor of HIV-1 that facilitates infection in immune cells. Cellular functions of Vpr are tied to its interaction with DCAF1, a substrate receptor component of the CRL4 E3 ubiquitin ligase. Recent proteomic approaches suggested that Vpr degrades helicase-like transcription factor (HLTF) DNA helicase in a proteasome-dependent manner by redirecting the CRL4-DCAF1 E3 ligase. However, the precise molecular mechanism of Vpr-dependent HLTF depletion is not known. Here, using in vitro reconstitution assays, we show that Vpr mediates polyubiquitination of HLTF, by directly loading it onto the C-terminal WD40 domain of DCAF1 in complex with the CRL4 E3 ubiquitin ligase. Mutational analyses suggest that Vpr interacts with DNA-binding residues in the N-terminal HIRAN domain of HLTF in a manner similar to the recruitment of another target, uracil DNA glycosylase (UNG2), to the CRL4-DCAF1 E3 by Vpr. Strikingly, Vpr also engages a second, adjacent region, which connects the HIRAN and ATPase/helicase domains. Thus, our findings reveal that Vpr utilizes common as well as distinctive interfaces to recruit multiple postreplication DNA repair proteins to the CRL4-DCAF1 E3 ligase for ubiquitin-dependent proteasomal degradation.
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Affiliation(s)
- Xiaohong Zhou
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
| | - Maria DeLucia
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
| | - Caili Hao
- Department of Molecular Biology and Microbiology, Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Kasia Hrecka
- Department of Molecular Biology and Microbiology, Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Christina Monnie
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
| | - Jacek Skowronski
- Department of Molecular Biology and Microbiology, Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Jinwoo Ahn
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
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11
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Patra KK, Bhattacharya A, Bhattacharya S. Allosteric Signal Transduction in HIV-1 Restriction Factor SAMHD1 Proceeds via Reciprocal Handshake across Monomers. J Chem Inf Model 2017; 57:2523-2538. [PMID: 28956603 DOI: 10.1021/acs.jcim.7b00279] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The sterile alpha motif and histidine-aspartate domain-containing protein 1 (or SAMHD1), a human dNTP-triphosphohydrolase, contributes to HIV-1 restriction in select terminally differentiated cells of the immune system. The catalytically active form of the protein is an allosterically triggered tetramer, whose HIV-1 restriction properties are attributed to its dNTP-triphosphohydrolase activity. The tetramer itself is assembled by a GTP/dNTP combination. This enzyme uses the strategy of deoxynucleotide starvation, which is thought to prevent effective reverse transcription of the retroviral genome-hence, restricting HIV-1 propagation. HIV-2 and SIV have evolved defenses against SAMHD1, underscoring its role in restriction. Previous studies have provided high-resolution structures of GTP/dNTP-bound enzyme complexes but have not been able to provide information on dynamics. In this study, we have used correlation network analysis along with MD techniques to study the flow of allosteric information across the active complex. We have found evidence of a reciprocal allosteric "handshake" occurring across monomeric units. We have also uncovered a short linker region as the nexus for funnelling the regulatory signal from phosphorylation at T592 from the surface to the interior core of the protein.
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Affiliation(s)
- Kajwal Kumar Patra
- Department of Physics, Indian Institute of Technology Guwahati , Guwahati, Assam, India 781039
| | - Akash Bhattacharya
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio , San Antonio, Texas 78229-3900, United States
| | - Swati Bhattacharya
- Department of Physics, Indian Institute of Technology Guwahati , Guwahati, Assam, India 781039.,Department of Chemical Engineering, Indian Institute of Technology Bombay , Mumbai, India 400076
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12
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Inhibition of Vpx-Mediated SAMHD1 and Vpr-Mediated Host Helicase Transcription Factor Degradation by Selective Disruption of Viral CRL4 (DCAF1) E3 Ubiquitin Ligase Assembly. J Virol 2017; 91:JVI.00225-17. [PMID: 28202763 DOI: 10.1128/jvi.00225-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 02/09/2017] [Indexed: 12/21/2022] Open
Abstract
The lentiviral accessory proteins Vpx and Vpr are known to utilize CRL4 (DCAF1) E3 ligase to induce the degradation of the host restriction factor SAMHD1 or host helicase transcription factor (HLTF), respectively. Selective disruption of viral CRL4 (DCAF1) E3 ligase could be a promising antiviral strategy. Recently, we have determined that posttranslational modification (neddylation) of Cullin-4 is required for the activation of Vpx-CRL4 (DCAF1) E3 ligase. However, the mechanism of Vpx/Vpr-CRL4 (DCAF1) E3 ligase assembly is still poorly understood. Here, we report that zinc coordination is an important regulator of Vpx-CRL4 E3 ligase assembly. Residues in a conserved zinc-binding motif of Vpx were essential for the recruitment of the CRL4 (DCAF1) E3 complex and Vpx-induced SAMHD1 degradation. Importantly, altering the intracellular zinc concentration by treatment with the zinc chelator N,N,N'-tetrakis-(2'-pyridylmethyl)ethylenediamine (TPEN) potently blocked Vpx-mediated SAMHD1 degradation and inhibited wild-type SIVmac (simian immunodeficiency virus of macaques) infection of myeloid cells, even in the presence of Vpx. TPEN selectively inhibited Vpx and DCAF1 binding but not the Vpx-SAMHD1 interaction or Vpx virion packaging. Moreover, we have shown that zinc coordination is also important for the assembly of the HIV-1 Vpr-CRL4 E3 ligase. In particular, Vpr zinc-binding motif mutation or TPEN treatment efficiently inhibited Vpr-CRL4 (DCAF1) E3 ligase assembly and Vpr-mediated HLTF degradation or Vpr-induced G2 cell cycle arrest. Collectively, our study sheds light on a conserved strategy by the viral proteins Vpx and Vpr to recruit host CRL4 (DCAF1) E3 ligase, which represents a target for novel anti-human immunodeficiency virus (HIV) drug development.IMPORTANCE The Vpr and its paralog Vpx are accessory proteins encoded by different human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) lentiviruses. To facilitate viral replication, Vpx has evolved to induce SAMHD1 degradation and Vpr to mediate HLTF degradation. Both Vpx and Vpr perform their functions by recruiting CRL4 (DCAF1) E3 ligase. In this study, we demonstrate that the assembly of the Vpx- or Vpr-CRL4 E3 ligase requires a highly conserved zinc-binding motif. This motif is specifically required for the DCAF1 interaction but not for the interaction of Vpx or Vpr with its substrate. Selective disruption of Vpx- or Vpr-CRL4 E3 ligase function was achieved by zinc sequestration using N,N,N'-tetrakis-(2'-pyridylmethyl)ethylenediamine (TPEN). At the same time, zinc sequestration had no effect on zinc-dependent cellular protein functions. Therefore, information obtained from this study may be important for novel anti-HIV drug development.
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13
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Jang S, Zhou X, Ahn J. Substrate Specificity of SAMHD1 Triphosphohydrolase Activity Is Controlled by Deoxyribonucleoside Triphosphates and Phosphorylation at Thr592. Biochemistry 2016; 55:5635-5646. [PMID: 27588835 DOI: 10.1021/acs.biochem.6b00627] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The sterile alpha motif (SAM) and histidine-aspartate (HD) domain containing protein 1 (SAMHD1) constitute a triphosphohydrolase that converts deoxyribonucleoside triphosphates (dNTPs) into deoxyribonucleosides and triphosphates. SAMHD1 exists in multiple states. The monomer and apo- or GTP-bound dimer are catalytically inactive. Binding of dNTP at allosteric site 2 (AS2), adjacent to GTP-binding allosteric site 1 (AS1), induces formation of the tetramer, the catalytically active form. We have developed an enzyme kinetic assay, tailored to control specific dNTP binding at each site, allowing us to determine the kinetic binding parameters of individual dNTPs at both the AS2 and catalytic sites for all possible combinations of dNTP binding at both sites. Here, we show that the apparent Km values of dNTPs at AS2 vary in the order of dCTP < dGTP < dATP < dTTP. Interestingly, dCTP binding at AS2 significantly reduces the dCTP hydrolysis rate, which is restored to a rate comparable to that of other dNTPs upon dGTP, dATP, or dTTP binding at AS2. Strikingly, a phosphomimetic mutant, Thr592Asp SAMHD1 as well as phospho-Thr592, show a significantly altered substrate specificity, with the rate of dCTP hydrolysis being selectively reduced regardless of which dNTP binds at AS2. Furthermore, cyclin A2 binding at the C-terminus of SAMHD1 induces the disassembly of the SAMHD1 tetramer, suggesting an additional layer of SAMHD1 activity modulation by cyclin A2/CDK2 kinase. Together, our results reveal multiple allosteric mechanisms for controlling the rate of dNTP destruction by SAMHD1.
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Affiliation(s)
- Sunbok Jang
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
| | - Xiaohong Zhou
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
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14
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Wu Y, Zhou X, Barnes CO, DeLucia M, Cohen AE, Gronenborn AM, Ahn J, Calero G. The DDB1-DCAF1-Vpr-UNG2 crystal structure reveals how HIV-1 Vpr steers human UNG2 toward destruction. Nat Struct Mol Biol 2016; 23:933-940. [PMID: 27571178 DOI: 10.1038/nsmb.3284] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/03/2016] [Indexed: 01/04/2023]
Abstract
The HIV-1 accessory protein Vpr is required for efficient viral infection of macrophages and promotion of viral replication in T cells. Vpr's biological activities are closely linked to the interaction with human DCAF1, a cellular substrate receptor of the Cullin4-RING E3 ubiquitin ligase (CRL4) of the host ubiquitin-proteasome-mediated protein degradation pathway. The molecular details of how Vpr usurps the protein degradation pathway have not been delineated. Here we present the crystal structure of the DDB1-DCAF1-HIV-1-Vpr-uracil-DNA glycosylase (UNG2) complex. The structure reveals how Vpr engages with DCAF1, creating a binding interface for UNG2 recruitment in a manner distinct from the recruitment of SAMHD1 by Vpx proteins. Vpr and Vpx use similar N-terminal and helical regions to bind the substrate receptor, whereas different regions target the specific cellular substrates. Furthermore, Vpr uses molecular mimicry of DNA by a variable loop for specific recruitment of the UNG2 substrate.
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Affiliation(s)
- Ying Wu
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Xiaohong Zhou
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Christopher O Barnes
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Maria DeLucia
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Aina E Cohen
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, California, USA
| | - Angela M Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Jinwoo Ahn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Guillermo Calero
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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15
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Zhou X, DeLucia M, Ahn J. SLX4-SLX1 Protein-independent Down-regulation of MUS81-EME1 Protein by HIV-1 Viral Protein R (Vpr). J Biol Chem 2016; 291:16936-16947. [PMID: 27354282 DOI: 10.1074/jbc.m116.721183] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Indexed: 12/22/2022] Open
Abstract
Evolutionarily conserved structure-selective endonuclease MUS81 forms a complex with EME1 and further associates with another endonuclease SLX4-SLX1 to form a four-subunit complex of MUS81-EME1-SLX4-SLX1, coordinating distinctive biochemical activities of both endonucleases in DNA repair. Viral protein R (Vpr), a highly conserved accessory protein in primate lentiviruses, was previously reported to bind SLX4 to mediate down-regulation of MUS81. However, the detailed mechanism underlying MUS81 down-regulation is unclear. Here, we report that HIV-1 Vpr down-regulates both MUS81 and its cofactor EME1 by hijacking the host CRL4-DCAF1 E3 ubiquitin ligase. Multiple Vpr variants, from HIV-1 and SIV, down-regulate both MUS81 and EME1. Furthermore, a C-terminally truncated Vpr mutant and point mutants R80A and Q65R, all of which lack G2 arrest activity, are able to down-regulate MUS81-EME1, suggesting that Vpr-induced G2 arrest is not correlated with MUS81-EME1 down-regulation. We also show that neither the interaction of MUS81-EME1 with Vpr nor their down-regulation is dependent on SLX4-SLX1. Together, these data provide new insight on a conserved function of Vpr in a host endonuclease down-regulation.
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Affiliation(s)
- Xiaohong Zhou
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Maria DeLucia
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Jinwoo Ahn
- From the Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
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16
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Franzolin E, Salata C, Bianchi V, Rampazzo C. The Deoxynucleoside Triphosphate Triphosphohydrolase Activity of SAMHD1 Protein Contributes to the Mitochondrial DNA Depletion Associated with Genetic Deficiency of Deoxyguanosine Kinase. J Biol Chem 2015; 290:25986-96. [PMID: 26342080 PMCID: PMC4646252 DOI: 10.1074/jbc.m115.675082] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Indexed: 11/22/2022] Open
Abstract
The dNTP triphosphohydrolase SAMHD1 is a nuclear antiviral host restriction factor limiting HIV-1 infection in macrophages and a major regulator of dNTP concentrations in human cells. In normal human fibroblasts its expression increases during quiescence, contributing to the small dNTP pool sizes of these cells. Down-regulation of SAMHD1 by siRNA expands all four dNTP pools, with dGTP undergoing the largest relative increase. The deoxyguanosine released by SAMHD1 from dGTP can be phosphorylated inside mitochondria by deoxyguanosine kinase (dGK) or degraded in the cytosol by purine nucleoside phosphorylase. Genetic mutations of dGK cause mitochondrial (mt) DNA depletion in noncycling cells and hepato-cerebral mtDNA depletion syndrome in humans. We studied if SAMHD1 and dGK interact in the regulation of the dGTP pool during quiescence employing dGK-mutated skin fibroblasts derived from three unrelated patients. In the presence of SAMHD1 quiescent mutant fibroblasts manifested mt dNTP pool imbalance and mtDNA depletion. When SAMHD1 was silenced by siRNA transfection the composition of the mt dNTP pool approached that of the controls, and mtDNA copy number increased, compensating the depletion to various degrees in the different mutant fibroblasts. Chemical inhibition of purine nucleoside phosphorylase did not improve deoxyguanosine recycling by dGK in WT cells. We conclude that the activity of SAMHD1 contributes to the pathological phenotype of dGK deficiency. Our results prove the importance of SAMHD1 in the regulation of all dNTP pools and suggest that dGK inside mitochondria has the function of recycling the deoxyguanosine derived from endogenous dGTP degraded by SAMHD1 in the nucleus.
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Affiliation(s)
- Elisa Franzolin
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
| | - Cristiano Salata
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy
| | - Vera Bianchi
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
| | - Chiara Rampazzo
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
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17
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Wu Y, Koharudin LMI, Mehrens J, DeLucia M, Byeon CH, Byeon IJL, Calero G, Ahn J, Gronenborn AM. Structural Basis of Clade-specific Engagement of SAMHD1 (Sterile α Motif and Histidine/Aspartate-containing Protein 1) Restriction Factors by Lentiviral Viral Protein X (Vpx) Virulence Factors. J Biol Chem 2015; 290:17935-17945. [PMID: 26045556 DOI: 10.1074/jbc.m115.665513] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Indexed: 11/06/2022] Open
Abstract
Sterile α motif (SAM) and histidine/aspartate (HD)-containing protein 1 (SAMHD1) restricts human/simian immunodeficiency virus infection in certain cell types and is counteracted by the virulence factor Vpx. Current evidence indicates that Vpx recruits SAMHD1 to the Cullin4-Ring Finger E3 ubiquitin ligase (CRL4) by facilitating an interaction between SAMHD1 and the substrate receptor DDB1- and Cullin4-associated factor 1 (DCAF1), thereby targeting SAMHD1 for proteasome-dependent down-regulation. Host-pathogen co-evolution and positive selection at the interfaces of host-pathogen complexes are associated with sequence divergence and varying functional consequences. Two alternative interaction interfaces are used by SAMHD1 and Vpx: the SAMHD1 N-terminal tail and the adjacent SAM domain or the C-terminal tail proceeding the HD domain are targeted by different Vpx variants in a unique fashion. In contrast, the C-terminal WD40 domain of DCAF1 interfaces similarly with the two above complexes. Comprehensive biochemical and structural biology approaches permitted us to delineate details of clade-specific recognition of SAMHD1 by lentiviral Vpx proteins. We show that not only the SAM domain but also the N-terminal tail engages in the DCAF1-Vpx interaction. Furthermore, we show that changing the single Ser-52 in human SAMHD1 to Phe, the residue found in SAMHD1 of Red-capped monkey and Mandrill, allows it to be recognized by Vpx proteins of simian viruses infecting those primate species, which normally does not target wild type human SAMHD1 for degradation.
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Affiliation(s)
- Ying Wu
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Leonardus M I Koharudin
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Jennifer Mehrens
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Maria DeLucia
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Chang-Hyeok Byeon
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - In-Ja L Byeon
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Guillermo Calero
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Jinwoo Ahn
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260.
| | - Angela M Gronenborn
- Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260.
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18
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Degradation of SAMHD1 by Vpx Is Independent of Uncoating. J Virol 2015; 89:5701-13. [PMID: 25762741 DOI: 10.1128/jvi.03575-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/05/2015] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Sterile alpha motif domain and HD domain-containing protein 1 (SAMHD1) restricts human immunodeficiency virus type 1 (HIV-1) replication in myeloid and resting T cells. Lentiviruses such as HIV-2 and some simian immunodeficiency viruses (SIVs) counteract the restriction by encoding Vpx or Vpr, accessory proteins that are packaged in virions and which, upon entry of the virus into the cytoplasm, induce the proteasomal degradation of SAMHD1. As a tool to study these mechanisms, we generated HeLa cell lines that express a fusion protein termed NLS.GFP.SAM595 in which the Vpx binding domain of SAMHD1 is fused to the carboxy terminus of green fluorescent protein (GFP) and a nuclear localization signal is fused to the amino terminus of GFP. Upon incubation of Vpx-containing virions with the cells, the NLS.GFP.SAM595 fusion protein was degraded over several hours and the levels remained low over 5 days as the result of continued targeting of the CRL4 E3 ubiquitin ligase. Degradation of the fusion protein required that it contain a nuclear localization sequence. Fusion to the cytoplasmic protein muNS rendered the protein resistant to Vpx-mediated degradation, confirming that SAMHD1 is targeted in the nucleus. Virions treated with protease inhibitors failed to release Vpx, indicating that Gag processing was required for Vpx release from the virion. Mutations in the capsid protein that altered the kinetics of virus uncoating and the Gag binding drug PF74 had no effect on the Vpx-mediated degradation. These results suggest that Vpx is released from virions without a need for uncoating of the capsid, allowing Vpx to transit to the nucleus rapidly upon entry into the cytoplasm. IMPORTANCE SAMHD1 restricts lentiviral replication in myeloid cells and resting T cells. Its importance is highlighted by the fact that viruses such as HIV-2 encode an accessory protein that is packaged in the virion and is dedicated to inducing SAMHD1 degradation. Vpx needs to act rapidly upon infection to allow reverse transcription to proceed. The limited number of Vpx molecules in a virion also needs to clear the cell of SAMHD1 over a prolonged period of time. Using an engineered HeLa cell line that expresses a green fluorescent protein (GFP)-SAMHD1 fusion protein, we showed that the Vpx-dependent degradation occurs without a need for viral capsid uncoating. In addition, the fusion protein was degraded only when it was localized to the nucleus, confirming that SAMHD1 is targeted in the nucleus and thus explaining why Vpx also localizes to the nucleus.
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19
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DePaula-Silva AB, Cassiday PA, Chumley J, Bosque A, Monteiro-Filho CMR, Mahon CS, Cone KR, Krogan N, Elde NC, Planelles V. Determinants for degradation of SAMHD1, Mus81 and induction of G2 arrest in HIV-1 Vpr and SIVagm Vpr. Virology 2015; 477:10-17. [PMID: 25618414 DOI: 10.1016/j.virol.2014.12.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 10/13/2014] [Accepted: 12/29/2014] [Indexed: 11/16/2022]
Abstract
Vpr and Vpx are a group of highly related accessory proteins from primate lentiviruses. Despite the high degree of amino acid homology within this group, these proteins can be highly divergent in their functions. In this work, we constructed chimeric and mutant proteins between HIV-1 and SIVagm Vpr in order to better understand the structure-function relationships. We tested these constructs for their abilities to induce G2 arrest in human cells and to degrade agmSAMHD1 and Mus81. We found that the C-terminus of HIV-1 Vpr, when transferred onto SIVagm Vpr, provides the latter with the de novo ability to induce G2 arrest in human cells. We confirmed that HIV-1 Vpr induces degradation of Mus81 although, surprisingly, degradation is independent and genetically separable from Vpr׳s ability to induce G2 arrest.
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Affiliation(s)
- Ana Beatriz DePaula-Silva
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA
| | - Patrick A Cassiday
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA
| | - Jeffrey Chumley
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA
| | - Alberto Bosque
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA
| | - Carlos M R Monteiro-Filho
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA
| | - Cathal S Mahon
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
| | - Kelsey R Cone
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Nevan Krogan
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
| | - Nels C Elde
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Vicente Planelles
- Division of Microbiology and Immunology, Department of Pathology, University of Utah School of Medicine, 15 North Medical Drive East #2100, Salt Lake City, UT 84112, USA.
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20
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Kyei GB, Cheng X, Ramani R, Ratner L. Cyclin L2 is a critical HIV dependency factor in macrophages that controls SAMHD1 abundance. Cell Host Microbe 2014; 17:98-106. [PMID: 25532805 DOI: 10.1016/j.chom.2014.11.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 09/11/2014] [Accepted: 11/03/2014] [Indexed: 11/16/2022]
Abstract
The restriction factor SAMHD1 limits HIV-1 replication in noncycling cells. SIV and HIV-2 overcome this restriction via the accessory protein Vpx, which targets SAMHD1 for degradation through interactions with the host ubiquitin ligase adaptor DCAF1. However, the factors used by HIV-1 to replicate in macrophages, despite the presence of the restriction factor SAMHD1, are unknown. Using a yeast two-hybrid screen, we identified cyclin L2 as a DCAF1-interacting protein required for HIV-1 replication in macrophages. Knockdown of cyclin L2 results in severe attenuation of HIV-1 replication in macrophages but not cycling cells, and this effect is lost in the absence of SAMHD1. Cyclin L2 and SAMHD1 form a molecular complex that is partially dependent on the presence of DCAF1 and results in SAMHD1 degradation in a proteasome- and DCAF1-dependent manner. Therefore, cyclin L2-mediated control of SAMHD1 levels in macrophages supports HIV-1 replication.
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Affiliation(s)
- George Boateng Kyei
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Xiaogang Cheng
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Rashmi Ramani
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Lee Ratner
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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21
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Koharudin LMI, Wu Y, DeLucia M, Mehrens J, Gronenborn AM, Ahn J. Structural basis of allosteric activation of sterile α motif and histidine-aspartate domain-containing protein 1 (SAMHD1) by nucleoside triphosphates. J Biol Chem 2014; 289:32617-27. [PMID: 25288794 DOI: 10.1074/jbc.m114.591958] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Sterile α motif and histidine-aspartate domain-containing protein 1 (SAMHD1) plays a critical role in inhibiting HIV infection, curtailing the pool of dNTPs available for reverse transcription of the viral genome. Recent structural data suggested a compelling mechanism for the regulation of SAMHD1 enzymatic activity and revealed dGTP-induced association of two inactive dimers into an active tetrameric enzyme. Here, we present the crystal structures of SAMHD1 catalytic core (residues 113-626) tetramers, complexed with mixtures of nucleotides, including dGTP/dATP, dGTP/dCTP, dGTP/dTTP, and dGTP/dUTP. The combined structural and biochemical data provide insight into dNTP promiscuity at the secondary allosteric site and how enzymatic activity is modulated. In addition, we present biochemical analyses of GTP-induced SAMHD1 full-length tetramerization and the structure of SAMHD1 catalytic core tetramer in complex with GTP/dATP, revealing the structural basis of GTP-mediated SAMHD1 activation. Altogether, the data presented here advance our understanding of SAMHD1 function during cellular homeostasis.
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Affiliation(s)
- Leonardus M I Koharudin
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Ying Wu
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Maria DeLucia
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Jennifer Mehrens
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Angela M Gronenborn
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
| | - Jinwoo Ahn
- From the Department of Structural Biology and Pittsburgh Center for HIV-Host Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260
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22
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Schaller T, Bauby H, Hué S, Malim MH, Goujon C. New insights into an X-traordinary viral protein. Front Microbiol 2014; 5:126. [PMID: 24782834 PMCID: PMC3986551 DOI: 10.3389/fmicb.2014.00126] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 03/11/2014] [Indexed: 11/13/2022] Open
Abstract
Vpx is a protein encoded by members of the HIV-2/SIVsmm and SIVrcm/SIVmnd-2 lineages of primate lentiviruses, and is packaged into viral particles. Vpx plays a critical role during the early steps of the viral life cycle and has been shown to counteract SAMHD1, a restriction factor in myeloid and resting T cells. However, it is becoming evident that Vpx is a multifunctional protein in that SAMHD1 antagonism is likely not its sole role. This review summarizes the current knowledge on this X-traordinary protein.
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Affiliation(s)
- Torsten Schaller
- Department of Infectious Diseases, King's College London London, UK
| | - Hélène Bauby
- Department of Infectious Diseases, King's College London London, UK
| | - Stéphane Hué
- Department of Infection, Division of Infection and Immunity, Centre for Medical Molecular Virology, University College London London, UK
| | - Michael H Malim
- Department of Infectious Diseases, King's College London London, UK
| | - Caroline Goujon
- Department of Infectious Diseases, King's College London London, UK
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Reinhard C, Bottinelli D, Kim B, Luban J. Vpx rescue of HIV-1 from the antiviral state in mature dendritic cells is independent of the intracellular deoxynucleotide concentration. Retrovirology 2014; 11:12. [PMID: 24485168 PMCID: PMC3923257 DOI: 10.1186/1742-4690-11-12] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 01/28/2014] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND SIVMAC/HIV-2 Vpx recruits the CUL4A-DCAF1 E3 ubiquitin ligase complex to degrade the deoxynucleotide hydrolase SAMHD1. This increases the concentration of deoxynucleotides available for reverse transcription in myeloid cells and resting T cells. Accordingly, transduction of these cells by SIVMAC requires Vpx. Virus-like particles containing SIVMAC Vpx (Vpx-VLPs) also increase the efficiency of HIV-1 transduction in these cells, and rescue transduction by HIV-1, but not SIVMAC, in mature monocyte-derived dendritic cells (MDDCs). Differences in Vpx mechanism noted at that time, along with recent data suggesting that SAMHD1 gains additional restriction capabilities in the presence of type I IFN prompted further examination of the role of Vpx and SAMHD1 in HIV-1 transduction of mature MDDCs. RESULTS When challenged with Vpx-VLPs, SAMHD1 was degraded in MDDCs even after cells had been matured with LPS, though there was no increase in deoxynucleotide levels. Steady-state levels of HIV-1 late reverse transcription products in mature MDDCs were increased to the same extent by either Vpx-VLPs or exogenous nucleosides. In contrast, only Vpx-VLPs increased the levels of 2-LTR circles and proviral DNA in myeloid cells. These results demonstrate that exogenous nucleosides and Vpx-VLPs both increase the levels of HIV-1 cDNA in myeloid cells, but only Vpx-VLPs rescue 2-LTR circles and proviral DNA in myeloid cells with a previously established antiviral state. Finally, since trans-acting Vpx-VLPs provide long-lasting rescue of HIV-1 vector transduction in the face of the antiviral state, and exogenous nucleosides do not, exogenous nucleosides were used to achieve efficient transduction of MDDCs by vectors that stably encode Vprs and Vpxs from a collection of primate lentiviruses. Vpr from SIVDEB or SIVMUS, Vpx from SIVMAC251 or HIV-2, but not SIVRCM, degraded endogenous SAMHD1, increased steady-state levels of HIV-1 cDNA, and rescued HIV-1 from the antiviral state in MDDCs. CONCLUSION Inhibition of deoxynucleotide hydrolysis by promoting SAMHD1 degradation is not the only mechanism by which Vpx rescues HIV-1 in MDDCs from the antiviral state. Vpx has an additional effect on HIV-1 transduction of these cells that occurs after completion of reverse transcription and acts independently of deoxynucleotide levels.
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Affiliation(s)
| | | | | | - Jeremy Luban
- Department of Microbiology and Molecular Medicine, University of Geneva, 1 Rue Michel Servet, Geneva 4 CH-1211, Switzerland.
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Schwefel D, Groom HCT, Boucherit VC, Christodoulou E, Walker PA, Stoye JP, Bishop KN, Taylor IA. Structural basis of lentiviral subversion of a cellular protein degradation pathway. Nature 2014; 505:234-8. [PMID: 24336198 PMCID: PMC3886899 DOI: 10.1038/nature12815] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 10/28/2013] [Indexed: 12/20/2022]
Abstract
Lentiviruses contain accessory genes that have evolved to counteract the effects of host cellular defence proteins that inhibit productive infection. One such restriction factor, SAMHD1, inhibits human immunodeficiency virus (HIV)-1 infection of myeloid-lineage cells as well as resting CD4(+) T cells by reducing the cellular deoxynucleoside 5'-triphosphate (dNTP) concentration to a level at which the viral reverse transcriptase cannot function. In other lentiviruses, including HIV-2 and related simian immunodeficiency viruses (SIVs), SAMHD1 restriction is overcome by the action of viral accessory protein x (Vpx) or the related viral protein r (Vpr) that target and recruit SAMHD1 for proteasomal degradation. The molecular mechanism by which these viral proteins are able to usurp the host cell's ubiquitination machinery to destroy the cell's protection against these viruses has not been defined. Here we present the crystal structure of a ternary complex of Vpx with the human E3 ligase substrate adaptor DCAF1 and the carboxy-terminal region of human SAMHD1. Vpx is made up of a three-helical bundle stabilized by a zinc finger motif, and wraps tightly around the disc-shaped DCAF1 molecule to present a new molecular surface. This adapted surface is then able to recruit SAMHD1 via its C terminus, making it a competent substrate for the E3 ligase to mark for proteasomal degradation. The structure reported here provides a molecular description of how a lentiviral accessory protein is able to subvert the cell's normal protein degradation pathway to inactivate the cellular viral defence system.
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Affiliation(s)
- David Schwefel
- Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Harriet C. T. Groom
- Division of Virology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Virginie C. Boucherit
- Division of Virology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Evangelos Christodoulou
- Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Philip A. Walker
- Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Jonathan P. Stoye
- Division of Virology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Kate N. Bishop
- Division of Virology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Ian A. Taylor
- Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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Vorontsov II, Wu Y, DeLucia M, Minasov G, Mehrens J, Shuvalova L, Anderson WF, Ahn J. Mechanisms of allosteric activation and inhibition of the deoxyribonucleoside triphosphate triphosphohydrolase from Enterococcus faecalis. J Biol Chem 2013; 289:2815-24. [PMID: 24338016 DOI: 10.1074/jbc.m113.524207] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
EF1143 from Enterococcus faecalis, a life-threatening pathogen that is resistant to common antibiotics, is a homo-tetrameric deoxyribonucleoside triphosphate (dNTP) triphosphohydrolase (dNTPase), converting dNTPs into the deoxyribonucleosides and triphosphate. The dNTPase activity of EF1143 is regulated by canonical dNTPs, which simultaneously act as substrates and activity modulators. Previous crystal structures of apo-EF1143 and the protein bound to both dGTP and dATP suggested allosteric regulation of its enzymatic activity by dGTP binding at four identical allosteric sites. However, whether and how other canonical dNTPs regulate the enzyme activity was not defined. Here, we present the crystal structure of EF1143 in complex with dGTP and dTTP. The new structure reveals that the tetrameric EF1143 contains four additional secondary allosteric sites adjacent to the previously identified dGTP-binding primary regulatory sites. Structural and enzyme kinetic studies indicate that dGTP binding to the first allosteric site, with nanomolar affinity, is a prerequisite for substrate docking and hydrolysis. Then, the presence of a particular dNTP in the second site either enhances or inhibits the dNTPase activity of EF1143. Our results provide the first mechanistic insight into dNTP-mediated regulation of dNTPase activity.
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Affiliation(s)
- Ivan I Vorontsov
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611 and
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Sze A, Olagnier D, Lin R, van Grevenynghe J, Hiscott J. SAMHD1 Host Restriction Factor: A Link with Innate Immune Sensing of Retrovirus Infection. J Mol Biol 2013; 425:4981-94. [DOI: 10.1016/j.jmb.2013.10.022] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 10/15/2013] [Accepted: 10/16/2013] [Indexed: 02/02/2023]
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Mechanism of allosteric activation of SAMHD1 by dGTP. Nat Struct Mol Biol 2013; 20:1304-9. [PMID: 24141705 PMCID: PMC3833828 DOI: 10.1038/nsmb.2692] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/10/2013] [Indexed: 01/21/2023]
Abstract
SAMHD1, a dNTP triphosphohydrolase (dNTPase), has a key role in human innate immunity. It inhibits infection of blood cells by retroviruses, including HIV, and prevents the development of the autoinflammatory Aicardi-Goutières syndrome (AGS). The inactive apo-SAMHD1 interconverts between monomers and dimers, and in the presence of dGTP the protein assembles into catalytically active tetramers. Here, we present the crystal structure of the human tetrameric SAMHD1-dGTP complex. The structure reveals an elegant allosteric mechanism of activation through dGTP-induced tetramerization of two inactive dimers. Binding of dGTP to four allosteric sites promotes tetramerization and induces a conformational change in the substrate-binding pocket to yield the catalytically active enzyme. Structure-based biochemical and cell-based biological assays confirmed the proposed mechanism. The SAMHD1 tetramer structure provides the basis for a mechanistic understanding of its function in HIV restriction and the pathogenesis of AGS.
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Nakagawa T, Mondal K, Swanson PC. VprBP (DCAF1): a promiscuous substrate recognition subunit that incorporates into both RING-family CRL4 and HECT-family EDD/UBR5 E3 ubiquitin ligases. BMC Mol Biol 2013; 14:22. [PMID: 24028781 PMCID: PMC3847654 DOI: 10.1186/1471-2199-14-22] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 09/03/2013] [Indexed: 12/19/2022] Open
Abstract
The terminal step in the ubiquitin modification system relies on an E3 ubiquitin ligase to facilitate transfer of ubiquitin to a protein substrate. The substrate recognition and ubiquitin transfer activities of the E3 ligase may be mediated by a single polypeptide or may rely on separate subunits. The latter organization is particularly prevalent among members of largest class of E3 ligases, the RING family, although examples of this type of arrangement have also been reported among members of the smaller HECT family of E3 ligases. This review describes recent discoveries that reveal the surprising and distinctive ability of VprBP (DCAF1) to serve as a substrate recognition subunit for a member of both major classes of E3 ligase, the RING-type CRL4 ligase and the HECT-type EDD/UBR5 ligase. The cellular processes normally regulated by VprBP-associated E3 ligases, and their targeting and subversion by viral accessory proteins are also discussed. Taken together, these studies provide important insights and raise interesting new questions regarding the mechanisms that regulate or subvert VprBP function in the context of both the CRL4 and EDD/UBR5 E3 ligases.
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Affiliation(s)
- Tadashi Nakagawa
- Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine, Graduate School of Medicine, Tohoku University, Sendai 900-8575, Japan.
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Abstract
Replication of HIV-1 and other retroviruses is dependent on numerous host proteins in the cells. Some of the host proteins, however, function as restriction factors to block retroviral infection of target cells. The host protein SAMHD1 has been identified as the first mammalian deoxynucleoside triphosphate triphosphohydrolase (dNTPase), which blocks the infection of HIV-1 and other retroviruses in non-cycling immune cells. SAMHD1 protein is highly expressed in human myeloid-lineage cells and CD4+ T-lymphocytes, but its retroviral restriction function is only observed in noncycling cells. Recent studies have revealed biochemical mechanisms of SAMHD1-mediated retroviral restriction. In this review, the latest progress on SAMHD1 research is summarized and the mechanisms by which SAMHD1 mediates retroviral restriction are analyzed. Although the physiological function of SAMHD1 is largely unknown, this review provides perspectives about the role of endogenous SAMHD1 protein in maintaining normal cellular function, such as nucleic acid metabolism and the proliferation of cells.
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