FIGURE 1.

Identification of PARP1 as a novel protein partner for TREX1. A, expression levels of both IFPN-tagged TREX1 and endogenous TREX1 proteins from HEK293 stable cell lines expressing TREX1 were determined by Western blotting. α-Tubulin served as an endogenous loading control. B, IFPN-tagged TREX1 was purified with anti-GFP antibody from the cell extracts, eluted in SDS buffer, and subjected to SDS-PAGE. The proteins were visualized by Coomassie Brilliant Blue (CBB) staining. Peptide sequences of the PARP1 protein were obtained by mass spectrometry. Two of seven peptide sequences that identified PARP1 are shown. Note that the IFPN-TREX1 target protein of size 50 kDa is almost overlapped by the heavy chain IgG band. HC, heavy chain; LC, light chain. C, the whole-cell extracts from the stable cell lines were immunoprecipitated with anti-GFP antibody and immunoblotted with anti-PARP1 or anti-TREX1 antibody. Protein input was assessed by Western blotting with the indicated antibodies. D, purified PARP1 was incubated with GST or GST-TREX1 coupled to glutathione-Sepharose 4B. Proteins retained on Sepharose were eluted and then blotted with the indicated antibodies.