Increased Artemis levels confer radioresistance to both high and low LET radiation exposures

Deepa M Sridharan,Mary K Whalen,Janice M Pluth,Steven M Yannone,Donna Almendrala,Misako Kawahara,Francis A Cucinotta

doi:10.1186/1748-717x-7-96

Abstract

BackgroundArtemis has a defined role in V(D)J recombination and has been implicated in the repair of radiation induced double-strand breaks. However the exact function(s) of Artemis in DNA repair and its preferred substrate(s) in vivo remain undefined. Our previous work suggests that Artemis is important for the repair of complex DNA damage like that inflicted by high Linear Energy Transfer (LET) radiation. To establish the contribution of Artemis in repairing DNA damage caused by various radiation qualities, we evaluated the effect of over-expressing Artemis on cell survival, DNA repair, and cell cycle arrest after exposure to high and low LET radiation.ResultsOur data reveal that Artemis over-expression confers marked radioprotection against both types of radiation, although the radioprotective effect was greater following high LET radiation. Inhibitor studies reveal that the radioprotection imparted by Artemis is primarily dependent on DNA-PK activity, and to a lesser extent on ATM kinase activity. Together, these data suggest a DNA-PK dependent role for Artemis in the repair of complex DNA damage.ConclusionsThese findings indicate that Artemis levels significantly influence radiation toxicity in human cells and suggest that Artemis inhibition could be a practical target for adjuvant cancer therapies.

Highlights

Artemis has a defined role in V(D)J recombination and has been implicated in the repair of radiation induced double-strand breaks
We find that DNA protein kinase (DNA-PK) kinase activity influences the survival advantage imparted by Artemis over-expression to a greater degree that ataxia telangiectasia mutated (ATM) kinase activity and that Artemis phosphorylation is uncoupled from radioresistance
We find that Artemis over-expression accelerates the resolution of γH2AX, and by inference the rate of doublestrand break repair in vivo (Figure 2)

Summary

Introduction

Artemis has a defined role in V(D)J recombination and has been implicated in the repair of radiation induced double-strand breaks. The exact function(s) of Artemis in DNA repair and its preferred substrate(s) in vivo remain undefined. Our previous work suggests that Artemis is important for the repair of complex DNA damage like that inflicted by high Linear Energy Transfer (LET) radiation. Radiation therapy is one of the most broadly prescribed treatments for malignancy. We have identified elevated Artemis levels as being a powerful determinant of radiation resistance in human cells. Individuals lacking functional Artemis are extremely sensitive to radiation and cannot generate mature B or T cells due to incomplete V(D)J recombination which results in immunodeficiency [1].

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