Fig. 6
SAMHD1 is dephosphorylated at T592 by PP2A-B55α holoenzymes during mitotic exit in cycling cells. Knock-down of PP2A B55α subunit leads to impaired and delayed dephosphorylation of SAMHD1 at T592 during mitotic exit. HeLa cells were either transfected with control siRNA or simultaneously with a single siRNA targeting PP2A B55α subunit. Transfected cells were then arrested in mitosis using nocodazole and mitotic exit was induced chemically by adding flavopiridol (FP) in the presence of MG-132. Cells were harvested at the indicated time points over a period of 18 min. Whole-cell lysates were analyzed by immunoblotting using antibodies specific to the indicated proteins. For quantification, the signal of phosphorylated SAMHD1 ( = SAMHD1 pT592; signal marked with asterisks, compared to SAMHD1 pT592 signal in non-synchronized cells (see Supplementary Fig. 5f)) was normalized to total SAMHD1 and level of SAMHD1 pT592 within 18 min compared between siCtr- and siB55α-transfected cells. Immunoblot data shown are representative of two independent experiments, while the quantification graphs represent the mean ± SD of both experiments
