Activation of the DNA-dependent protein kinase by drug-induced and radiation-induced DNA strand breaks.

MÃ¥rtensson S, Nygren J, Osheroff N, Hammarsten O
Radiat Res. 2003 160 (3): 291-301

PMID: 12926987 · DOI:10.1667/0033-7587(2003)160[0291:aotdpk]2.0.co;2

The DNA-dependent protein kinase (DNA-PK) is a DNA-end activated protein kinase that is required for efficient repair of DNA double-strand breaks (DSBs) and for normal resistance to ionizing radiation. DNA-PK is composed of a DNA-binding subunit, Ku, and a catalytic subunit, DNA-PKcs (PRKDC). We have previously shown that PRKDC is activated when the enzyme interacts with the terminal nucleotides of a DSB. These nucleotides are often damaged when DSBs are introduced by anticancer agents and could therefore prevent recognition by DNA-PK. To determine whether DNA-PK could recognize DNA strand breaks generated by agents used in the treatment of cancer, we damaged plasmid DNA with anticancer drugs and ionizing radiation. The DNA breaks were tested for the ability to activate purified DNA-PK. The data indicate that DSBs produced by bleomycin, calicheamicin and two types of ionizing radiation ((137)Cs gamma rays and N(7+) ions: high and low linear energy transfer, respectively) activate DNA-PK to levels matching the kinase activation obtained with simple restriction endonuclease-induced DSBs. In contrast, the protein-linked DSBs produced by etoposide and topoisomerase II failed to bind and activate DNA-PK. Our findings indicate that DNA-PK recognizes DSBs regardless of chemical complexity but cannot recognize the protein-linked DSBs produced by etoposide and topoisomerase II.

MeSH Terms (26)

Aminoglycosides Anti-Bacterial Agents Antibiotics, Antineoplastic Antigens, Nuclear Antimetabolites, Antineoplastic Bleomycin DNA DNA-Activated Protein Kinase DNA-Binding Proteins DNA Damage DNA Helicases DNA Repair DNA Topoisomerases, Type II Dose-Response Relationship, Drug Enediynes Energy Transfer Enzyme Activation Etoposide Ferritins Ku Autoantigen Models, Biological Nucleic Acid Synthesis Inhibitors Plasmids Protein-Serine-Threonine Kinases Protein Binding Radiation, Ionizing

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