DNA-PKcs dependence of Artemis endonucleolytic activity, differences between hairpins and 5' or 3' overhangs.

During V(D)J recombination, the RAG proteins create DNA hairpins at the V, D, or J coding ends, and the structure-specific nuclease Artemis is essential to open these hairpins prior to joining. Artemis also is an endonuclease for 5' and 3' overhangs at many DNA double strand breaks caused by ionizing radiation, and Artemis functions as part of the nonhomologous DNA end joining pathway in repairing these. All of these activities require activation of the Artemis protein by interaction with and phosphorylation by the DNA-dependent protein kinase catalytic subunit (DNA-PKcs).