| Structural highlights
Disease
[SAMH1_HUMAN] Defects in SAMHD1 are the cause of Aicardi-Goutieres syndrome type 5 (AGS5) [MIM:612952]. A form of Aicardi-Goutieres syndrome, a genetically heterogeneous disease characterized by cerebral atrophy, leukoencephalopathy, intracranial calcifications, chronic cerebrospinal fluid (CSF) lymphocytosis, increased CSF alpha-interferon, and negative serologic investigations for common prenatal infection. Clinical features as thrombocytopenia, hepatosplenomegaly and elevated hepatic transaminases along with intermittent fever may erroneously suggest an infective process. Severe neurological dysfunctions manifest in infancy as progressive microcephaly, spasticity, dystonic posturing and profound psychomotor retardation. Death often occurs in early childhood.[1] [2] Defects in SAMHD1 are the cause of chilblain lupus type 2 (CHBL2) [MIM:614415]. A rare cutaneous form of lupus erythematosus. Affected individuals present with painful bluish-red papular or nodular lesions of the skin in acral locations precipitated by cold and wet exposure at temperatures less than 10 degrees centigrade.[3]
Function
[VPRBP_HUMAN] Component of the CUL4A-RBX1-DDB1-VprBP/DCAF1 E3 ubiquitin-protein ligase complex, VprBP/DCAF1 may function as the substrate recognition module within this complex. For example, VprBP/DCAF1 targets NF2 to the E3 ubiquitin-ligase complex for ubiquitination and subsequent proteasome-dependent degradation. In case of infection by HIV-1 virus, it is recruited by HIV-1 Vpr in order to hijack the CUL4A-RBX1-DDB1 function leading to arrest the cell cycle in G2 phase, and also to protect the viral protein from proteasomal degradation by another E3 ubiquitin ligase. In case of infection by HIV-2 virus, it is recruited by HIV-2 Vpx in order to hijack the CUL4A-RBX1-DDB1 function leading to enhanced efficiency of macrophage infection and promotion of the replication of cognate primate lentiviruses in cells of monocyte/macrophage lineage. Associated with chromatin in a DDB1-independent and cell cycle-dependent manner, VprBP/DCAF1 is recruited to chromatin as DNA is being replicated and is released from chromatin before mitosis.[4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [SAMH1_HUMAN] Putative nuclease involved in innate immune response by acting as a negative regulator of the cell-intrinsic antiviral response. May play a role in mediating proinflammatory responses to TNF-alpha signaling.[17] [18] [VPX_SIVSP] Plays a role in nuclear translocation of the viral pre-integration complex (PIC), thus is required for the virus to infect non-dividing cells. Targets specific host proteins for degradation by the 26S proteasome. Acts by associating with the cellular CUL4A-DDB1 E3 ligase complex through direct interaction with host VPRPB/DCAF-1. This change in the E3 ligase substrate specificity results in the degradation of host SAMHD1. In turn, SAMHD1 depletion allows viral replication in host myeloid cells by preventing SAMHD1-mediated hydrolysis of intracellular dNTPs necessary for reverse transcription.
Publication Abstract from PubMed
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.
Structural basis of lentiviral subversion of a cellular protein degradation pathway.,Schwefel D, Groom HC, Boucherit VC, Christodoulou E, Walker PA, Stoye JP, Bishop KN, Taylor IA Nature. 2013 Dec 15. doi: 10.1038/nature12815. PMID:24336198[19]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Rice GI, Bond J, Asipu A, Brunette RL, Manfield IW, Carr IM, Fuller JC, Jackson RM, Lamb T, Briggs TA, Ali M, Gornall H, Couthard LR, Aeby A, Attard-Montalto SP, Bertini E, Bodemer C, Brockmann K, Brueton LA, Corry PC, Desguerre I, Fazzi E, Cazorla AG, Gener B, Hamel BC, Heiberg A, Hunter M, van der Knaap MS, Kumar R, Lagae L, Landrieu PG, Lourenco CM, Marom D, McDermott MF, van der Merwe W, Orcesi S, Prendiville JS, Rasmussen M, Shalev SA, Soler DM, Shinawi M, Spiegel R, Tan TY, Vanderver A, Wakeling EL, Wassmer E, Whittaker E, Lebon P, Stetson DB, Bonthron DT, Crow YJ. Mutations involved in Aicardi-Goutieres syndrome implicate SAMHD1 as regulator of the innate immune response. Nat Genet. 2009 Jul;41(7):829-32. doi: 10.1038/ng.373. Epub 2009 Jun 14. PMID:19525956 doi:10.1038/ng.373
- ↑ Thiele H, du Moulin M, Barczyk K, George C, Schwindt W, Nurnberg G, Frosch M, Kurlemann G, Roth J, Nurnberg P, Rutsch F. Cerebral arterial stenoses and stroke: novel features of Aicardi-Goutieres syndrome caused by the Arg164X mutation in SAMHD1 are associated with altered cytokine expression. Hum Mutat. 2010 Nov;31(11):E1836-50. doi: 10.1002/humu.21357. PMID:20842748 doi:10.1002/humu.21357
- ↑ Ravenscroft JC, Suri M, Rice GI, Szynkiewicz M, Crow YJ. Autosomal dominant inheritance of a heterozygous mutation in SAMHD1 causing familial chilblain lupus. Am J Med Genet A. 2011 Jan;155A(1):235-7. doi: 10.1002/ajmg.a.33778. PMID:21204240 doi:10.1002/ajmg.a.33778
- ↑ Le Rouzic E, Belaidouni N, Estrabaud E, Morel M, Rain JC, Transy C, Margottin-Goguet F. HIV1 Vpr arrests the cell cycle by recruiting DCAF1/VprBP, a receptor of the Cul4-DDB1 ubiquitin ligase. Cell Cycle. 2007 Jan 15;6(2):182-8. Epub 2007 Jan 17. PMID:17314515
- ↑ Wen X, Duus KM, Friedrich TD, de Noronha CM. The HIV1 protein Vpr acts to promote G2 cell cycle arrest by engaging a DDB1 and Cullin4A-containing ubiquitin ligase complex using VprBP/DCAF1 as an adaptor. J Biol Chem. 2007 Sep 14;282(37):27046-57. Epub 2007 Jul 9. PMID:17620334 doi:http://dx.doi.org/10.1074/jbc.M703955200
- ↑ Tan L, Ehrlich E, Yu XF. DDB1 and Cul4A are required for human immunodeficiency virus type 1 Vpr-induced G2 arrest. J Virol. 2007 Oct;81(19):10822-30. Epub 2007 Jul 11. PMID:17626091 doi:http://dx.doi.org/10.1128/JVI.01380-07
- ↑ Belzile JP, Duisit G, Rougeau N, Mercier J, Finzi A, Cohen EA. HIV-1 Vpr-mediated G2 arrest involves the DDB1-CUL4AVPRBP E3 ubiquitin ligase. PLoS Pathog. 2007 Jul;3(7):e85. PMID:17630831 doi:http://dx.doi.org/10.1371/journal.ppat.0030085
- ↑ Hrecka K, Gierszewska M, Srivastava S, Kozaczkiewicz L, Swanson SK, Florens L, Washburn MP, Skowronski J. Lentiviral Vpr usurps Cul4-DDB1[VprBP] E3 ubiquitin ligase to modulate cell cycle. Proc Natl Acad Sci U S A. 2007 Jul 10;104(28):11778-83. Epub 2007 Jul 3. PMID:17609381 doi:http://dx.doi.org/10.1073/pnas.0702102104
- ↑ DeHart JL, Zimmerman ES, Ardon O, Monteiro-Filho CM, Arganaraz ER, Planelles V. HIV-1 Vpr activates the G2 checkpoint through manipulation of the ubiquitin proteasome system. Virol J. 2007 Jun 8;4:57. PMID:17559673 doi:http://dx.doi.org/10.1186/1743-422X-4-57
- ↑ Le Rouzic E, Morel M, Ayinde D, Belaidouni N, Letienne J, Transy C, Margottin-Goguet F. Assembly with the Cul4A-DDB1DCAF1 ubiquitin ligase protects HIV-1 Vpr from proteasomal degradation. J Biol Chem. 2008 Aug 1;283(31):21686-92. doi: 10.1074/jbc.M710298200. Epub 2008 , Jun 4. PMID:18524771 doi:http://dx.doi.org/10.1074/jbc.M710298200
- ↑ McCall CM, Miliani de Marval PL, Chastain PD 2nd, Jackson SC, He YJ, Kotake Y, Cook JG, Xiong Y. Human immunodeficiency virus type 1 Vpr-binding protein VprBP, a WD40 protein associated with the DDB1-CUL4 E3 ubiquitin ligase, is essential for DNA replication and embryonic development. Mol Cell Biol. 2008 Sep;28(18):5621-33. doi: 10.1128/MCB.00232-08. Epub 2008 Jul , 7. PMID:18606781 doi:http://dx.doi.org/10.1128/MCB.00232-08
- ↑ Huang J, Chen J. VprBP targets Merlin to the Roc1-Cul4A-DDB1 E3 ligase complex for degradation. Oncogene. 2008 Jul 3;27(29):4056-64. Epub 2008 Mar 10. PMID:18332868 doi:onc200844
- ↑ Srivastava S, Swanson SK, Manel N, Florens L, Washburn MP, Skowronski J. Lentiviral Vpx accessory factor targets VprBP/DCAF1 substrate adaptor for cullin 4 E3 ubiquitin ligase to enable macrophage infection. PLoS Pathog. 2008 May 9;4(5):e1000059. doi: 10.1371/journal.ppat.1000059. PMID:18464893 doi:http://dx.doi.org/10.1371/journal.ppat.1000059
- ↑ Bergamaschi A, Ayinde D, David A, Le Rouzic E, Morel M, Collin G, Descamps D, Damond F, Brun-Vezinet F, Nisole S, Margottin-Goguet F, Pancino G, Transy C. The human immunodeficiency virus type 2 Vpx protein usurps the CUL4A-DDB1 DCAF1 ubiquitin ligase to overcome a postentry block in macrophage infection. J Virol. 2009 May;83(10):4854-60. doi: 10.1128/JVI.00187-09. Epub 2009 Mar 4. PMID:19264781 doi:http://dx.doi.org/10.1128/JVI.00187-09
- ↑ Gramberg T, Sunseri N, Landau NR. Evidence for an activation domain at the amino terminus of simian immunodeficiency virus Vpx. J Virol. 2010 Feb;84(3):1387-96. doi: 10.1128/JVI.01437-09. Epub 2009 Nov 18. PMID:19923175 doi:http://dx.doi.org/10.1128/JVI.01437-09
- ↑ Lee JM, Lee JS, Kim H, Kim K, Park H, Kim JY, Lee SH, Kim IS, Kim J, Lee M, Chung CH, Seo SB, Yoon JB, Ko E, Noh DY, Kim KI, Kim KK, Baek SH. EZH2 generates a methyl degron that is recognized by the DCAF1/DDB1/CUL4 E3 ubiquitin ligase complex. Mol Cell. 2012 Nov 30;48(4):572-86. doi: 10.1016/j.molcel.2012.09.004. Epub 2012 , Oct 11. PMID:23063525 doi:http://dx.doi.org/10.1016/j.molcel.2012.09.004
- ↑ Liao W, Bao Z, Cheng C, Mok YK, Wong WS. Dendritic cell-derived interferon-gamma-induced protein mediates tumor necrosis factor-alpha stimulation of human lung fibroblasts. Proteomics. 2008 Jul;8(13):2640-50. doi: 10.1002/pmic.200700954. PMID:18546154 doi:10.1002/pmic.200700954
- ↑ Rice GI, Bond J, Asipu A, Brunette RL, Manfield IW, Carr IM, Fuller JC, Jackson RM, Lamb T, Briggs TA, Ali M, Gornall H, Couthard LR, Aeby A, Attard-Montalto SP, Bertini E, Bodemer C, Brockmann K, Brueton LA, Corry PC, Desguerre I, Fazzi E, Cazorla AG, Gener B, Hamel BC, Heiberg A, Hunter M, van der Knaap MS, Kumar R, Lagae L, Landrieu PG, Lourenco CM, Marom D, McDermott MF, van der Merwe W, Orcesi S, Prendiville JS, Rasmussen M, Shalev SA, Soler DM, Shinawi M, Spiegel R, Tan TY, Vanderver A, Wakeling EL, Wassmer E, Whittaker E, Lebon P, Stetson DB, Bonthron DT, Crow YJ. Mutations involved in Aicardi-Goutieres syndrome implicate SAMHD1 as regulator of the innate immune response. Nat Genet. 2009 Jul;41(7):829-32. doi: 10.1038/ng.373. Epub 2009 Jun 14. PMID:19525956 doi:10.1038/ng.373
- ↑ Schwefel D, Groom HC, Boucherit VC, Christodoulou E, Walker PA, Stoye JP, Bishop KN, Taylor IA. Structural basis of lentiviral subversion of a cellular protein degradation pathway. Nature. 2013 Dec 15. doi: 10.1038/nature12815. PMID:24336198 doi:http://dx.doi.org/10.1038/nature12815
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