siRNA knockdown of PP6R1 or PP6c decreases repair of DNA double-strand breaks and sensitizes glioblastoma cells to radiation.

<p>A. Two days after transfection with siRNA cells were irradiated with 10 Gy and either harvested immediately (10 Gy) or allowed to repair DNA damage for 3 hours (10 Gy+3 hours) prior to harvesting cells. Harvested cells were embedded in agarose plugs and subjected to PFGE as described. The bars represent the fraction of DNA released from agarose plugs during PFGE, normalized to sham-irradiated control (±SEM). The data are from two independent experiments. M059J cells were used as a negative control. B. M059K cells were transfected with control siRNA or specific siRNAs targeted to DNA-PKcs, PP6R1, PP6c, PP6R3, or ARS-A. Two days after transfection, the M059K cells were irradiated with 0, 2.5, 5 Gy, replated, cultured for two weeks and scored for surviving colonies. The data points show the mean of surviving fraction ± SD (n = 3). M059J cells were used as a negative control. C. Representative Western blot for siRNA knockdown efficiency. The blot shows the level of the proteins of interest after transfection with siRNA. Ku86 is a marker for the nuclear fraction and was used as a loading control.