ATM and DNA-PK function redundantly to phosphorylate H2AX after exposure to ionizing radiation

Stiff, Thomas, O'Driscoll, Mark, Rief, N, Iwabuchi, K, Lobrich, M and Jeggo, Penny (2004) ATM and DNA-PK function redundantly to phosphorylate H2AX after exposure to ionizing radiation. Cancer Research, 64 (7). pp. 2390-2396. ISSN 00085472

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H2AX phosphorylation is an early step in the response to DNA damage. It is widely accepted that ATM (ataxia telangiectasia mutated protein) phosphorylates H2AX in response to DNA double-strand breaks (DSBs). Whether DNA-dependent protein kinase (DNA-PK) plays any role in this response is unclear. Here, we show that H2AX phosphorylation after exposure to ionizing radiation (IR) occurs to similar extents in human fibroblasts and in mouse embryo fibroblasts lacking either DNA-PK or ATM but is ablated in ATM-deficient cells treated with LY294002, a drug that specifically inhibits DNA-PK. Additionally, we show that inactivation of both DNA-PK and ATM is required to ablate IR-induced H2AX phosphorylation in chicken cells. We confirm that H2AX phosphorylation induced by DSBs in nonreplicating cells is ATR (ataxia telangiectasia and Rad3-related protein) independent. Taken together, we conclude that under most normal growth conditions, IR-induced H2AX phosphorylation can be carried out by ATM and DNA-PK in a redundant, overlapping manner. In contrast, DNA-PK cannot phosphorylate other proteins involved in the checkpoint response, including chromatin-associated Rad17. However, by phosphorylating H2AX, DNA-PK can contribute to the presence of the damage response proteins MDCI and 53BPI at the site of the DSB.

Item Type: Article
Schools and Departments: School of Life Sciences > Sussex Centre for Genome Damage and Stability
Depositing User: Thomas Stiff
Date Deposited: 06 Feb 2012 19:50
Last Modified: 24 Jul 2012 08:42
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