Phospho-dependent regulation of SAMHD1 oligomerisation couples catalysis and restriction
journal contributionposted on 2020-07-07, 14:20 authored by Laurence H Arnold, Harriet CT Groom, Simone Kunzelmann, David Schwefel, Sarah J Caswell, Paula Ordonez, Melanie C Mann, Sabrina Rueschenbaum, David C Goldstone, Simon Pennell, Steven A Howell, Jonathan P Stoye, Michelle Webb, Ian A Taylor, Kate N Bishop
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.
BiocatalysisCell LineChromatography, GelChromatography, High Pressure LiquidCrystallography, X-RayFlow CytometryHIV-1HumansMonomeric GTP-Binding ProteinsPhosphorylationProtein ConformationReverse Transcriptase Polymerase Chain ReactionSAM Domain and HD Domain-Containing Protein 1Spectrophotometry, AtomicBishop U117592729Taylor, I U117565647Stoye U117512710Smerdon U117584228PRTSB0605 Microbiology1107 Immunology1108 Medical MicrobiologyVirology