Extracellular Signal-Related Kinase Positively Regulates Ataxia Telangiectasia Mutated, Homologous Recombination Repair, and the DNA Damage Response

Abstract

The accurate joining of DNA double-strand breaks by homologous recombination repair (HRR) is critical to the long-term survival of the cell. The three major mitogenactivated protein (MAP) kinase (MAPK) signaling pathways, extracellular signal-regulated kinase (ERK), p38, and c-Jun-NH 2 -kinase (JNK), regulate cell growth, survival, and apoptosis. To determine the role of MAPK signaling in HRR, we used a human in vivo I-SceI-based repair system. First, we verified that this repair platform is amenable to pharmacologic manipulation and show that the ataxia telangiectasia mutated (ATM) kinase is critical for HRR. The ATM-specific inhibitor KU-55933 compromised HRR up to 90% in growth-arrested cells, whereas this effect was less pronounced in cycling cells. Then, using well-characterized MAPK small-molecule inhibitors, we show that ERK1/2 and JNK signaling are important positive regulators of HRR in growth-arrested cells. On the other hand, inhibition of the p38 MAPK pathway generated an almost 2-fold stimulation of HRR. When ERK1/2 signaling was stimulated by oncogenic RAF-1, an f2-fold increase in HRR was observed. KU-55933 partly blocked radiation-induced ERK1/2 phosphorylation, suggesting that ATM regulates ERK1/2 signaling. Furthermore, inhibition of MAP/ERK kinase (MEK)/ERK signaling resulted in severely reduced levels of phosphorylated (S1981) ATM foci but not ;-H2AX foci, and suppressed ATM phosphorylation levels >85% throughout the cell cycle. Collectively, these results show that MAPK signaling positively and negatively regulates HRR in human cells. More specifically, ATM-dependent signaling through the RAF/MEK/ ERK pathway is critical for efficient HRR and for radiationinduced ATM activation, suggestive of a regulatory feedback loop between ERK and ATM. [Cancer Res 2007;67(3):1046-53]

PARP and CHK inhibitors interact to cause DNA damage and cell death in mammary carcinoma cells

“…17,39 Studies have also linked ATM activation to activation of the ERK1/2 pathway. 41 Activated MEK1 increased the levels of both ERCC1 and XRCC1 in breast cancer cells arguing that a portion of the mechanism by which activated MEK1 could suppress DNA damage is through upregulation of these proteins.…”

Heme oxygenase-1 and carbon monoxide modulate DNA repair through ataxia-telangiectasia mutated (ATM) protein

“…CO has been shown to activate signaling pathways that involve hemoproteins such as guanylate cyclase, nitric oxide synthase, and the mitochondrial cytochromes and also has been shown to influence the activation of the nonheme signaling molecules including p38, MAPK, STAT3, peroxisome proliferator-activated receptor-γ, and hypoxia-inducible transcription factor-1α (20,21). ATM phosphorylation in response to ischemia reperfusion is severely impaired with blockade of the MAPK pathway (22), which is a well-described target for HO-1/CO (23). Importantly, inhibition of the MAPK-ERK pathway reduced the levels of phosphorylated ATM foci, but not γ-H2AX (22), and cells lacking STAT3 showed decreased DNA repair through ATM and ATR (24).…”

“…ATM phosphorylation in response to ischemia reperfusion is severely impaired with blockade of the MAPK pathway (22), which is a well-described target for HO-1/CO (23). Importantly, inhibition of the MAPK-ERK pathway reduced the levels of phosphorylated ATM foci, but not γ-H2AX (22), and cells lacking STAT3 showed decreased DNA repair through ATM and ATR (24). We speculate that CO targets the DNA structure either directly or by binding to the metal ions on DNA and thereby influences the function of DNA-associated enzymes.…”

Role of epidermal growth factor receptor in DNA damage repair

“…It is well-accepted that HR is most active in late S-phase and G2. It is plausible, therefore, that these apparently disparate changes in HR can be reconciled by considering the cell cycle phase in which they have occurred [18,24,25].…”

“…The ATM-specific inhibitor KU-55933 partly blocks radiation-induced ERK1/2 phosphorylation, suggesting that ATM regulates ERK1/2 signaling. Thus, it seems that ATM and ERK signaling might be interacting in a regulatory feedback loop [25,26]. EGFR may affect transcription of the ATM gene by NF-κB, activated through the PI3K-Akt pathway.…”