(A) TREX1 DNase activity was measured by a real-time fluorescent assay using a 30-nt-long ssDNA as a substrate. HeLa cells and HeLa cells stably expressing TREX1-V5 were grown asynchronously (AS) or arrested in mitosis with nocodazole (M). Cell extracts were immunoprecipitated with anti-V5 agarose beads. After the assay is completed, aliquots of the reaction mixtures were examined by immunoblot of Phos-Tag PAGE to confirm status of TREX1 phosphorylation (right).
(B) TREX1-V5 WT, S78A/261A, and S78D/261D mutants were expressed in 293T cells and immunoprecipitated using anti-V5 agarose beads. DNase activity was measured as in (A). After the assay ended, aliquots of the reaction mixtures were examined by immunoblots with regular SDS-PAGE (bottom).
(C) TREX1-V5 WT and a S166A/167A mutant were expressed in 293T cells and immunoprecipitated using anti-V5 agarose beads. DNase activity was measured as in (A). After the assay ended, aliquots of the reaction mixtures were examined by immunoblots with regular SDS-PAGE (bottom). Data are representative of at least three independent experiments. Error bars, SD.