FIGURE 6.

TREX1 influences PARP1 cleavage and poly(ADP-ribosyl)ation of PARP1 during DNA damage response. A, HeLa cells transfected with FLAG-TREX1 or a control FLAG vector were cultured with or without staurosporine (1 μm) for 3 h before harvest. Whole protein extracts prepared with Nonidet P-40 cell lysis buffer were subjected to SDS-PAGE and then immunoblotted with antibodies against PARP1, FLAG, or tubulin. Signal intensities of endogenous full-length and cleaved PARP1 were quantified and normalized to tubulin. Data are given as the mean ± S.E. (error bars). *, p < 0.05; **, p < 0.005 by paired t test. B, TREX1 stably overexpressing or control HEK293 cells were treated with or without sodium arsenite (2 mm) for 10 or 30 min. Whole-cell extracts were immunoprecipitated with anti-PARP1 antibody and immunoblotted with anti-PAR or anti-PARP1 antibody. Densitometric analyses of the blots for PAR levels normalized to PARP1 levels are shown in the lower panels. PARlated, poly(ADP-ribosyl)ated.