Figure 7.

Knockdown of PARG and PARP1 delays single-strand break repair. DNA single-strand breakage was measured with the comet assay. A) A549 cells were treated with 400 μM hydrogen peroxide for 15 min and then allowed to recover in culture medium for indicated time periods. Single cells were then exposed to an electric field in agarose gel and stained with ethidium bromide, as described in Materials and Methods. Labeled DNA was visualized under fluorescent microscope. B) Control, shPARP1, and shPARG cells were exposed to 400 μM hydrogen peroxide for 15 min and then allowed to recover in culture medium for 45 min. Single cells then underwent electrophoresis and were processed as described above. Distribution of olive tail moments is shown at right. Representative images are presented (A, B). C) Clonogenic activity of 200 μM hydrogen peroxide-treated control, shPARP1, and shPARG cells.