title: Phospho-dependent Regulation of SAMHD1 Oligomerisation Couples Catalysis and Restriction.
abstract: SAMHD1 restricts HIV-1 infection of myeloid-lineage and resting CD4+ T-cells. Most likely this occurs through deoxynucleoside triphosphate triphosphohydrolase activity that reduces cellular dNTP to a level where reverse transcriptase cannot function, although alternative mechanisms have been proposed recently. Here, we present combined structural and virological data demonstrating that in addition to allosteric activation and triphosphohydrolase activity, restriction correlates with the capacity of SAMHD1 to form "long-lived" enzymatically competent tetramers. Tetramer disruption invariably abolishes restriction but has varied effects on in vitro triphosphohydrolase activity. SAMHD1 phosphorylation also ablates restriction and tetramer formation but without affecting triphosphohydrolase steady-state kinetics. However phospho-SAMHD1 is unable to catalyse dNTP turnover under conditions of nucleotide depletion. Based on our findings we propose a model for phosphorylation-dependent regulation of SAMHD1 activity where dephosphorylation switches housekeeping SAMHD1 found in cycling cells to a high-activity stable tetrameric form that depletes and maintains low levels of dNTPs in differentiated cells.
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Arnold
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Harriet C T
authors.initials: HC
authors.lastname: Groom
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Simone
authors.initials: S
authors.lastname: Kunzelmann
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Schwefel
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Caswell
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Paula
authors.initials: P
authors.lastname: Ordonez
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Mann
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Rueschenbaum
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: David C
authors.initials: DC
authors.lastname: Goldstone
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Pennell
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Howell
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom; Faculty of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Stoye
authors.affiliation: Centre for Genomic Medicine, Institute for Human Development, Faculty of Medicine and Human Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Michelle
authors.initials: M
authors.lastname: Webb
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Taylor
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London, United Kingdom.
authors.forename: Kate N
authors.initials: KN
authors.lastname: Bishop
mesh_terms: D055162:Biocatalysis; D002460:Cell Line; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D005434:Flow Cytometry; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011487:Protein Conformation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000076106:SAM Domain and HD Domain-Containing Protein 1; D013054:Spectrophotometry, Atomic
chemical_list: D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins