Type I IFN treatment upregulates SAMHD1 expression in HEK 293T cells and HeLa cells. HEK 293T cells (A) and HeLa cells (B) were treated with different amounts of IFNα or IFNβ as indicated for 24 hr and whole cell lysates were subjected to immunoblotting for SAMHD1 and tetherin expression. β-actin is shown as a loading control. (C) Comparison of endogenous SAMHD1 expression in HEK 293T cells, HeLa cells, and monocyte-derived DCs (MDDCs) from five independent donors. Relative SAMHD1 levels compared to GAPDH are shown.