53BP1 - DNA damage response

Genotoxicity is an important indicator of safety of new molecules, but in cancer therapy, DNA damage is one of the most classical actions desired for a chemotherapeutic drug. The ability of cells to repair DNA damage is also an important indicator on whether the drug candidate is effective for chemotherapy.

To measure DNA damage we use the 53BP1 protein, which acts on cell cycle checkpoint signaling and on DNA repair through non-homologous end joining recombination. When a double-strand break (DSB) occurs, 53BP1 is recruited and accumulates, forming foci on the damage sites. Each nuclear focus indicates a site of DSB, and the total count indicates the degree of cell damage.