FIG. 8.

Knockdown of PolH confers on cells early resistance to UV-induced apoptosis but defers recovery from UV-induced DNA damage. (A) PolH knockdown significantly decreased UV-induced apoptosis at early times but increased UV-induced apoptosis at late times. RKO cells that are proficient and deficient in PolH were radiated with 12 J/m² of UV. At 0, 12, 24, 36, and 48 h after UV irradiation, cells were collected and fluorescence-activated cell sorting analysis was performed as in Fig. 2D to determine the ratio of apoptotic cells. (B) PARP cleavage is decreased in RKO-PolH-KD cells at early times but increased at late times after UV irradiation. RKO cells were treated as in panel A. Cells were collected, and uncleaved and cleaved PARP was detected with anti-PARP monoclonal antibody. (C) The parental and PolH knockdown RKO cells were treated as in panel A except that the cells were irradiated with 35 J/m² of UV.