FIGURE 1.

Interferons stimulate SAMHD1 expression. A, monocytic U937 cells and primary monocytes were treated with 1000 units/ml IFNα, IFNβ, IFNγ for 6 and 24 h (U937, top) and for 24 h (monocytes, bottom left). Protein samples were subjected to immunoblotting analysis and probed for SAMHD1, STAT1 to monitor successful stimulation, and ERK or ACTB as a loading control. Blots of three independent donors were quantified and corrected for ACTB signal and normalized to unstimulated controls (means ± S.D., bottom right). Immunoblots are representative of three independent experiments (n = 3). B, SAMHD1, ISG54, and IRF1 mRNA levels were quantified by real-time quantitative RT-PCR in U937 cells (top) and primary monocytes (bottom) after treatment with 1000 units/ml IFN for 24 h. Top, -fold changes of mRNA levels to the untreated samples were calculated for each individual experiment based on the mean of three technical replicates. The means ± S.D. of the -fold changes of three independent experiments are depicted (n = 3). Bottom, -fold changes of mRNA levels to the untreated samples were calculated for each individual donor. For two donors, the mean -fold change was based on one biological replicate each, measured in technical triplicates. For one donor, the mean -fold change was based on two biological replicates, each measured in two technical replicates. The means ± S.D. (error bars) of the -fold changes of three donors are depicted (n = 3). ns, p > 0.05; *, p ≤ 0.05; ****, p ≤ 0.0001.