Sensing of Ionizing Radiation-induced DNA Damage by ATM through Interaction with Histone Deacetylase

Abstract

The ATM gene is mutated in individuals with ataxia telangiectasia, a human genetic disease characterized by extreme sensitivity to radiation. The ATM protein acts as a sensor of radiation-induced cellular damage and contributes to cell cycle regulation, signal transduction, and DNA repair; however, the mechanisms underlying these functions of ATM remain largely unknown. Binding and immunoprecipitation assays have now shown that ATM interacts with the histone deacetylase HDAC1 both in vitro and in vivo, and that the extent of this association is increased after exposure of MRC5CV1 human fibroblasts to ionizing radiation. Histone deacetylase activity was also detected in immunoprecipitates prepared from these cells with antibodies to ATM, and this activity was blocked by the histone deacetylase inhibitor trichostatin A. These results suggest a previously unanticipated role for ATM in the modification of chromatin components in response to ionizing radiation.The human genetic disease ataxia telangiectasia (AT), 1 which is characterized by extreme sensitivity to radiation, is caused by mutations in the ATM gene (1, 2). The protein encoded by this gene acts as a sensor of radiation-induced cellular damage and plays important roles in cell cycle regulation, signal transduction, and DNA repair (2-6). However, the mechanisms by which ATM performs these various functions remain largely uncharacterized.Exposure of cells to ionizing radiation results in the arrest of cell cycle progression, induction of the transcription of specific genes, modification of nucleosomal structure, and activation of the DNA repair machinery (3, 6). Histone acetylation and deacetylation are thought to play important roles in the modification of chromatin structure and in monitoring chromosomal integrity during the cell cycle and transcriptional regulation (7-9). Various non-histone proteins that participate in regulation of the cell cycle and transcription are associated with histone acetylation or deacetylation activities (10 -14). Certain transcriptional coactivators, including pCAF, BRCA2, and ATM-like proteins, possess intrinsic acetylation activities (15-18). Conversely, transcriptional repressors have been shown to associate with histone deacetylases (19 -24). Recent studies have shown that the product of the retinoblastoma gene (Rb) represses transcription of the E2F gene by recruiting the mammalian deacetylase proteins HDAC1 and HDAC2, to which it binds through an LXCXE motif in its pocket domain (24 -27).Sequence analysis has revealed that the NH 2 terminus of ATM contains an LXCXE motif (amino acids 115-119) (Fig. 1a). We therefore investigated whether ATM also interacts with HDAC1. We have now shown that the two proteins indeed interact both in vitro and in vivo and that the extent of the association in vivo is increased by exposure of the cells to ionizing radiation. EXPERIMENTAL PROCEDURESCell Culture and Irradiation-Human normal (MRC5CV1) and AT (AT5BIVA, AT4BIVA, and AT3BIVA) fibroblasts were maintained at 37°C under an atmosphe...

Modulation of cellular radiation responses by histone deacetylase inhibitors

“…Importantly, the findings indicated that ionizing radiation enhances ATM-associated HDAC activity suggesting that HDACs may have a critical role in ATM signaling in response to DNA damage (Kim GD et al, 1999). The fact that this study demonstrated that TSA inhibits this ATM-associated HDAC activity, provides an insight into a possible mechanism by which HDAC inhibitors may enhance the radiation sensitivity of cells (Kim GD et al, 1999).…”

“…It has been shown using human fibroblasts that ATM interacts with HDAC1 both in vitro and in vivo (Kim GD et al, 1999;Ju and Muller, 2003). Importantly, the findings indicated that ionizing radiation enhances ATM-associated HDAC activity suggesting that HDACs may have a critical role in ATM signaling in response to DNA damage (Kim GD et al, 1999).…”

An HDAC1-binding domain within FATS bridges p21 turnover to radiation-induced tumorigenesis

“…Linkage between p21 and radiation-induced tumorigenesis Z Li et al HDAC1 is a major deacetylase whose genetic deletion causes a significant reduction in total HDAC activity (Zupkovitz et al, 2006), and its involvement in cancer has been established (Lin et al, 1998). In addition, HDAC1 has been implicated in ATM-mediated sensing of IR-induced DNA damage (Kim et al, 1999), implying the potential crosstalk between FATS and ATM. Although we cannot rule out the possibility that the interaction between FATS and HDAC1 may also abolish HDAC1-mediated repression of p21 transcription, which acts through a general transcription factor Sp1 (Lagger et al, 2002;Lagger et al, 2003), such effect on FATS-mediated induction of p21 is negligible, as FATS did not affect the expression of p27, whose expression is also mediated by Sp1 (Wei et al, 2003;Cen et al, 2008).…”

Integrated Bioinformatics for Radiation-Induced Pathway Analysis from Proteomics and Microarray Data

“…ATM plays critical roles in radiationinduced responses (Kastan et al, 2001;Kurz and Lees-Miller, 2004), and has been identified as a potential target for novel radiosensitizers (Sarkaria andEshleman, 2001, Ahmed andLi 2007). For example, small molecule inhibitors of ATM or downstream signaling molecules (Kim et al, 1999;Jung and Dritschilo, 2001) may offer a strategy to sensitize tumors to the lethal effects of ionizing radiation while sparing normal tissues.…”