Phospho-dependent Regulation of SAMHD1 Oligomerisation Couples Catalysis and Restriction

DOI: 10.1371/journal.ppat.1005194
PMID: 4592219

Authors: Laurence H. Arnold (The Francis Crick Institute) , Harriet C. T. Groom (The Francis Crick Institute) , Simone Kunzelmann (The Francis Crick Institute) , David Schwefel (The Francis Crick Institute) , Sarah J. Caswell (The Francis Crick Institute) , Paula Ordonez (The Francis Crick Institute) , Melanie C. Mann (The Francis Crick Institute) , Sabrina Rueschenbaum (The Francis Crick Institute) , David C. Goldstone (The Francis Crick Institute) , Simon Pennell (The Francis Crick Institute) , Steven A. Howell (The Francis Crick Institute) , Jonathan P. Stoye (The Francis Crick Institute) , Michelle Webb (University of Manchester) , Ian A. Taylor (The Francis Crick Institute) , Kate N. Bishop (The Francis Crick Institute)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Plos Pathogens , VOL 11 (10)

State: Published (Approved)
Published: October 2015

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.

Journal Keywords: Phosphorylation; HIV-1; Cell differentiation; Hydrolysis; Crystal structure; Electron density; Allosteric regulation; Enzyme regulation

Subject Areas: Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography , I04-Macromolecular Crystallography