Methods for Studying the G2 DNA Damage Checkpoint in Mammalian Cells

In response to post-replicative DNA damage, cells activate the G2 DNA damage checkpoint to ensure mitosis is not attempted until the damage has been repaired. This is a common response to a variety of DNA damaging agents, including ionizing radiation and many chemotherapeutic agents used in the treatment of cancer. The G2 DNA damage checkpoint acts to inhibit the mitotic cyclin-dependent kinase, and thus cells are arrested in the G2 phase of the cell cycle. The kinetics of this checkpoint can be assayed by staining cells for markers of mitosis, which can then be quantified by flow cytometry or microscopy.