Tip60-ing the balance in DSB repair.

Nature Cell Biology (Impact Factor: 20.06). 11/2009; 11(11):1279-81. DOI: 10.1038/ncb1109-1279
Source: PubMed
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    ABSTRACT: The key member of the MYST acetyltransferases family, TIP60 (Tat-interactive protein, 60KD) tightly modulates a wide array of cellular processes, including chromatin remodeling, gene transcription, apoptosis, DNA repair and cell cycle arrest. The function of TIP60 can be regulated by SIRT1 through deacetylation. Here, we found that TIP60 can also be functionally regulated by HDAC3. We identified six lysine residuals as its autoacetylation sites. Mutagenesis of these lysines to arginines completely abolishes the autoacetylation of TIP60. Overexpression of HDAC3 increases TIP60 ubiquitination levels. However, unlike SIRT1, HDAC3 increased the half-life of TIP60. Further study found that HDAC3 co-localized with TIP60 both in the nucleus and the cytoplasm which could be the reason that HDAC3 can stabilize the TIP60. The deacetylation of TIP60 by both SIRT1 and HDAC3 reduces apoptosis induced by DNA damage. Knockdown of HDAC3 in cells increased TIP60 acetylation levels and increased apoptosis after DNA damage. Together, our findings provide a better understanding of TIP60 regulation mechanisms which is significant basis for further studies on its cellular functions.
    Journal of Biological Chemistry 10/2014; 289(49). DOI:10.1074/jbc.M114.575266 · 4.60 Impact Factor
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    ABSTRACT: Nuclear EGFR is involved in cellular stress management and regulation of cellular radio-sensitivity. The aim of this study was to elucidate the molecular mode of nuclear EGFR action. Radiation induced nuclear EGFR-shuttling and EGFR-foci formation was analyzed with immunohistochemistry and confocal microscopy. Composition of γH(2)AX-protein complexes was analyzed by western-blotting after immuno-precipitation. Functional relevance of nuclear EGFR was analyzed after siRNA mediated depletion of EGFR with respect to activation of ATM, histone H3 acetylation, residual DNA-damage and cell survival after irradiation. Following radiation nuclear EGFR was localized in foci similar to γH(2)AX. EGFR co-localized in a sub-fraction of γH(2)AX-foci. Analysis of composition of γH(2)AX-complexes revealed presence of EGFR, ATM, promyelocytic leukemia protein (PML), histone H3 and hetero-chromatin binding protein (HP1) in response to radiation. Depletion of EGFR protein inhibited ATM activation due to inhibition of acetylase TIP60 activity following irradiation. Consequently, histone H3 acetylation and phosphorylation was blocked and chromatin could not be opened for repair. Thus, residual DNA-damage was increased 24 h after irradiation and cells were radio-sensitized. Comparable results were obtained when cells were treated with EGFR-NLS-peptide, which blocks EGFR nuclear shuttling specifically. Nuclear EGFR is part of DNA-damage repair complex and is involved in regulation of TIP60-acetylase activity. TIP60 is essential for ATM activation and chromatin relaxation which is a prerequisite for DNA-repair in heterochromatic DNA. Thus interventional EGFR strategies during tumor treatment may also interact with DNA-repair by blocking access to damaged DNA.
    Radiotherapy and Oncology 06/2011; 99(3):317-22. DOI:10.1016/j.radonc.2011.06.001 · 4.86 Impact Factor
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    ABSTRACT: BACKGROUND AND PURPOSE: EGFR and the sodium-dependent glucose transporter, SGLT1, are found in complex after radiation treatment. The aim of this study was to elucidate the role of EGFR in glucose uptake and chromatin remodeling. MATERIAL AND METHODS: Glucose accumulation was quantified with help of (3)H-glucose. Involvement of SGLT was detected by a specific inhibitor. Role of EGFR was proved by EGFR overexpression and siRNA driven knockdown. Functional endpoints were intracellular ATP levels, protein expression, residual DNA-damage and colony formation. RESULTS: EGFR/SGLT1 interactions in response to ionizing radiation were associated with increased glucose uptake. Nevertheless, tumor cells exhibit ATP depletion following irradiation. Recovery from radiation-induced ATP crisis was EGFR/SGLT-dependent and associated with increased cell survival and improved DNA-repair. The blockage of either EGFR or SGLT inhibited ATP level recovery and histone H3 modifications crucial for both chromatin remodeling and DNA repair in response to irradiation. Inhibition of the acetyltransferase TIP60, which is essential for histone H3-K9 acetylation and ATM activation, prevented energy crisis and chromatin remodeling. CONCLUSIONS: Radiation-associated interactions between SGLT1 and EGFR resulted in increased glucose uptake, which counteracts the ATP crisis in tumor cells due to chromatin remodeling. The blockage of recovery from ATP crisis led to radio-sensitization in tumor cells.
    Radiotherapy and Oncology 04/2013; 107(2). DOI:10.1016/j.radonc.2013.03.016 · 4.86 Impact Factor