(a) The NLS-GFP-SAMHD1-CtD degron. (b) Microscopic images of uninfected and SIV Vpx+/− infected 293T cells expressing NLS-GFP-SAMHD1-CtD wildtype or mutant R617E. (c) Quantitative analysis of GFPSAMHD1 degron expression following infection with SIV Vpx+/− viruses. Percentages of GFP+ cells are plotted against SIV virus titre. MG132 was added where indicated. Upper left panel is representative of three independent experiments. (d) Immunoblots of 293T cells co-transfected with SAMHD1 and Vpx plasmids (un, untransfected; −, empty vector; +, Vpx) probed with antibodies to SAMHD1 (upper), 14-3-3 (middle) or VpxHIV-2 (lower), representative of two independent experiments. (e) Restriction of HIV-1 infection by WT SAMHD1 and mutants. Restriction is expressed as a ratio of HIV-infected SAMHD1-transduced to infected SAMHD1-negative cells (>3 independent experiments with different viral stocks). Error bars show standard deviation.