DNA Double-Strand Break Formation Induced by Replication Arrest Depend On Artemis.

Abstract 1097

Poster Board I-119

Hydroxyurea (HU) is an antineoplastic drug used in hematological malignancies, specifically polycythemia vera, essential thrombocytosis or chronic myelogenous leukemia. HU targets cells that are actively replicating DNA by inhibit ing ribonucleotide reductase, which causes an imbalance in the deoxynucleotide triphosphate pool. Stalled replication forks lead to the production of single-stranded DNA (ssDNA), which in some cases is converted to DSBs by unknown mechanisms, an event that is termed replication fork collapse. however, the precise mechanism for DSB induction and the cellular response to persistent replication fork stalling are not fully understood. We show that DSBs are generated in an Artemis nuclease-dependent manner following prolonged stalling caused by exposure to HU, with subsequent activation of the ataxia-telangiectasia mutated (ATM) signaling pathway. DNA-dependent protein kinase (DNA-PK) activity, a prerequisite for the endonuclease activity of Artemis, is also required for DSB generation and subsequent ATM activation. Our findings indicate a novel function of Artemis as a molecular switch that converts single-stranded DNA lesions into DSBs, thereby activating an ATM-dependent fail-safe mechanism following prolonged replication fork stalling.