Figure 3.

Determination of the long-term effect of PARP-1 inhibitors on PAR levels and viability in PARG-null cells. (A) PARG-null TS cells were cultured and treated with PARP inhibitors as in Fig. 2 and maintained for 5 passages. At the end of each passage, cells were collected and analyzed for PAR levels by immunoblot. Cells treated with DPQ only survived through 2 passages. Loading controls were provided by immunodetection of β-actin. Positive controls for PARP inhibition (BZ treatment) were equivalent as in Fig. 1. Untreated cells, which served as negative controls (C), were collected after passage 2. (B) At the beginning (the day after plating) of passages 1 (P1) and 2 (P2), cells were viewed by light microscopy.