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Title: Interstitial chromatin alteration causes persistent p53 activation involved in the radiation-induced senescence-like growth arrest

Abstract

Various stresses including ionizing radiation give normal human fibroblasts a phenotype of senescence-like growth arrest (SLGA), manifested by p53-dependent irreversible G1 arrest. To determine the mechanism of persistent activation of p53, we examined phosphorylated Ataxia telangiectasia mutated (ATM) and phosphorylated histone H2AX foci formation after X-irradiation. Although the multiple tiny foci, detected soon after (<30 min) irradiation, gradually disappeared, some of these foci changed to large foci and persisted for 5 days. Large foci containing phosphorylated ATM and {gamma}-H2AX co-localized and foci with p53 phosphorylated at serine 15 also showed the same distribution. Interestingly, the signals obtained by telomere fluorescence in situ hybridization (FISH) assay did not co-localize with 90% of the large foci. Our results indicate that chromatin alteration in interstitial chromosomal regions is the most likely cause of continuous activation of p53, which results in the induction of SLGA by ionizing radiation.

Authors:
 [1];  [2];  [1];  [3];  [4]
  1. Division of Radiation Biology, Department of Radiology and Radiation Biology, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521 (Japan)
  2. (Japan)
  3. Division of Radiation Biology and Health Science, Research Institute for Advanced Science and Technology, Osaka Prefecture University, 1-2 Gakuen-cho, Sakai, Osaka 599-8570 (Japan)
  4. Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University, 2-1010 Asashironishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan). E-mail: nabe@rri.kyoto-u.ac.jp
Publication Date:
OSTI Identifier:
20798778
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 340; Journal Issue: 1; Other Information: DOI: 10.1016/j.bbrc.2005.11.167; PII: S0006-291X(05)02693-8; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRONMENTAL POLLUTANT EFFECTS ON LIVING ORGANISMS AND BIOLOGICAL MATERIALS; BIOLOGICAL RADIATION EFFECTS; BIOLOGICAL STRESS; CHROMATIN; FIBROBLASTS; FLUORESCENCE; GROWTH; IN-SITU HYBRIDIZATION; IONIZING RADIATIONS; IRRADIATION; PHENOTYPE; SERINE

Citation Formats

Suzuki, Masatoshi, Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University, 2-1010 Asashironishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Suzuki, Keiji, Kodama, Seiji, and Watanabe, Masami. Interstitial chromatin alteration causes persistent p53 activation involved in the radiation-induced senescence-like growth arrest. United States: N. p., 2006. Web. doi:10.1016/j.bbrc.2005.11.167.
Suzuki, Masatoshi, Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University, 2-1010 Asashironishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Suzuki, Keiji, Kodama, Seiji, & Watanabe, Masami. Interstitial chromatin alteration causes persistent p53 activation involved in the radiation-induced senescence-like growth arrest. United States. doi:10.1016/j.bbrc.2005.11.167.
Suzuki, Masatoshi, Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University, 2-1010 Asashironishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Suzuki, Keiji, Kodama, Seiji, and Watanabe, Masami. Fri . "Interstitial chromatin alteration causes persistent p53 activation involved in the radiation-induced senescence-like growth arrest". United States. doi:10.1016/j.bbrc.2005.11.167.
@article{osti_20798778,
title = {Interstitial chromatin alteration causes persistent p53 activation involved in the radiation-induced senescence-like growth arrest},
author = {Suzuki, Masatoshi and Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University, 2-1010 Asashironishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 and Suzuki, Keiji and Kodama, Seiji and Watanabe, Masami},
abstractNote = {Various stresses including ionizing radiation give normal human fibroblasts a phenotype of senescence-like growth arrest (SLGA), manifested by p53-dependent irreversible G1 arrest. To determine the mechanism of persistent activation of p53, we examined phosphorylated Ataxia telangiectasia mutated (ATM) and phosphorylated histone H2AX foci formation after X-irradiation. Although the multiple tiny foci, detected soon after (<30 min) irradiation, gradually disappeared, some of these foci changed to large foci and persisted for 5 days. Large foci containing phosphorylated ATM and {gamma}-H2AX co-localized and foci with p53 phosphorylated at serine 15 also showed the same distribution. Interestingly, the signals obtained by telomere fluorescence in situ hybridization (FISH) assay did not co-localize with 90% of the large foci. Our results indicate that chromatin alteration in interstitial chromosomal regions is the most likely cause of continuous activation of p53, which results in the induction of SLGA by ionizing radiation.},
doi = {10.1016/j.bbrc.2005.11.167},
journal = {Biochemical and Biophysical Research Communications},
number = 1,
volume = 340,
place = {United States},
year = {Fri Feb 03 00:00:00 EST 2006},
month = {Fri Feb 03 00:00:00 EST 2006}
}
  • Purpose: Senescence-like growth arrest in human solid carcinomas is now recognized as the major outcome of radiotherapy. This study was designed to analyze cell cycle during the process of senescence-like growth arrest in mammary carcinoma cells exposed to X-rays. Methods and Materials: Fluorescent ubiquitination-based cell cycle indicators were introduced into the human mammary carcinoma cell line MCF-7. Cell cycle was sequentially monitored by live-cell imaging for up to 5 days after exposure to 10 Gy of X-rays. Results: Live-cell imaging revealed that cell cycle transition from G2 to G1 phase without mitosis, so-called mitotic skipping, was observed in 17.1% andmore » 69.8% of G1- and G2-irradiated cells, respectively. Entry to G1 phase was confirmed by the nuclear accumulation of mKO{sub 2}-hCdt1 as well as cyclin E, which was inversely correlated to the accumulation of G2-specific markers such as mAG-hGeminin and CENP-F. More than 90% of cells skipping mitosis were persistently arrested in G1 phase and showed positive staining for the senescent biochemical marker, which is senescence-associated ss-galactosidase, indicating induction of senescence-like growth arrest accompanied by mitotic skipping. While G2 irradiation with higher doses of X-rays induced mitotic skipping in approximately 80% of cells, transduction of short hairpin RNA (shRNA) for p53 significantly suppressed mitotic skipping, suggesting that ionizing radiation-induced mitotic skipping is associated with p53 function. Conclusions: The present study found the pathway of senescence-like growth arrest in G1 phase without mitotic entry following G2-irradiation.« less
  • No abstract prepared.
  • Transforming growth factor {beta}1 (TGF {beta}1) induces Mv1Lu cell senescence by persistently producing mitochondrial reactive oxygen species (ROS) through decreased complex IV activity. Here, we investigated the molecular mechanism underlying the effect of TGF {beta}1 on mitochondrial complex IV activity. TGF {beta}1 progressively phosphorylated the negative regulatory sites of both glycogen synthase kinase 3 (GSK3) {alpha} and {beta}, corresponding well to the intracellular ROS generation profile. Pre-treatment of N-acetyl cysteine, an antioxidant, did not alter this GSK3 phosphorylation (inactivation), whereas pharmacological inhibition of GSK3 by SB415286 significantly increased mitochondrial ROS, implying that GSK3 phosphorylation is an upstream event of themore » ROS generation. GSK3 inhibition by SB415286 decreased complex IV activity and cellular O{sub 2} consumption rate and eventually induced senescence of Mv1Lu cell. Similar results were obtained with siRNA-mediated knockdown of GSK3. Moreover, we found that GSK3 not only exists in cytosol but also in mitochondria of Mv1Lu cell and the mitochondrial GSK3 binds complex IV subunit 6b which has no electron carrier and is topologically located in the mitochondrial intermembrane space. Involvement of subunit 6b in controlling complex IV activity and overall respiration rate was proved with siRNA-mediated knockdown of subunit 6b. Finally, TGF {beta}1 treatment decreased the binding of the subunit 6b to GSK3 and subunit 6b phosphorylation. Taken together, our results suggest that GSK3 inactivation is importantly involved in TGF {beta}1-induced complex IV defects through decreasing phosphorylation of the subunit 6b, thereby contributing to senescence-associated mitochondrial ROS generation.« less
  • Highlights: •The pathophysiological role of IL-6 in high glucose-induced podocyte loss. •The novel role of PGC-1α in the development of diabetic nephropathy. •Signaling of IL-6 and PGC-1α in high glucose-induced dysfunction of podocyte. -- Abstract: Podocyte loss, which is mediated by podocyte apoptosis, is implicated in the onset of diabetic nephropathy. In this study, we investigated the involvement of interleukin (IL)-6 in high glucose-induced apoptosis of rat podocytes. We also examined the pathophysiological role of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) in this system. High glucose treatment induced not only podocyte apoptosis but also podocyte growth arrest. High glucosemore » treatment also increased IL-6 secretion and activated IL-6 signaling. The high glucose-induced podocyte apoptosis was blocked by IL-6 neutralizing antibody. IL-6 treatment or overexpression induced podocyte apoptosis and growth arrest, and IL-6 siRNA transfection blocked high glucose-induced podocyte apoptosis and growth arrest. Furthermore, high glucose or IL-6 treatment increased PGC-1α expression, and PGC-1α overexpression also induced podocyte apoptosis and growth arrest. PGC-1α siRNA transfection blocked high glucose-induced podocyte apoptosis and growth arrest. Collectively, these findings showed that high glucose promoted apoptosis and cell growth arrest in podocytes via IL-6 signaling. In addition, PGC-1α is involved in podocyte apoptosis and cell growth arrest. Therefore, blocking IL-6 and its downstream mediators such as IL6Rα, gp130 and PGC-1α may attenuate the progression of diabetic nephropathy.« less
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