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Oxidation resistance 1 prevents genome instability through maintenance of G2/M arrest in gamma-ray-irradiated cells.

ABSTRACT: Human oxidation resistance 1 (OXR1) was identified as a protein that decreases genomic mutations in Escherichia coli caused by oxidative DNA damage. However, the mechanism by which OXR1 defends against genome instability has not been elucidated. To clarify how OXR1 maintains genome stability, the effects of OXR1-depletion on genome stability were investigated in OXR1-depleted HeLa cells using gamma-rays (?-rays). The OXR1-depleted cells had higher levels of superoxide and micronucleus (MN) formation than control cells after irradiation. OXR1-overexpression alleviated the increases in reactive oxygen species (ROS) level and MN formation after irradiation. The increased MN formation in irradiated OXR1-depleted cells was partially attenuated by the ROS inhibitor N-acetyl-L-cysteine, suggesting that OXR1-depeletion increases ROS-dependent genome instability. We also found that OXR1-depletion shortened the duration of ?-ray-induced G2/M arrest. In the presence of the cell cycle checkpoint inhibitor caffeine, the level of MN formed after irradiation was similar between control and OXR1-depleted cells, demonstrating that OXR1-depletion accelerates MN formation through abrogation of G2/M arrest. In OXR1-depleted cells, the level of cyclin D1 protein expression was increased. Here we report that OXR1 prevents genome instability by cell cycle regulation as well as oxidative stress defense.

SUBMITTER: Matsui A

PROVIDER: S-EPMC6976731 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Oxidation resistance 1 prevents genome instability through maintenance of G2/M arrest in gamma-ray-irradiated cells.

Matsui Ako A Kobayashi Junya J Kanno Shin-Ichiro SI Hashiguchi Kazunari K Miyaji Masahiro M Yoshikawa Yukihiro Y Yasui Akira A Zhang-Akiyama Qiu-Mei QM

Journal of radiation research 20200101 1

Human oxidation resistance 1 (OXR1) was identified as a protein that decreases genomic mutations in Escherichia coli caused by oxidative DNA damage. However, the mechanism by which OXR1 defends against genome instability has not been elucidated. To clarify how OXR1 maintains genome stability, the effects of OXR1-depletion on genome stability were investigated in OXR1-depleted HeLa cells using gamma-rays (γ-rays). The OXR1-depleted cells had higher levels of superoxide and micronucleus (MN) forma ...[more]

PMID: 31845986

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Project description:Vpr is an accessory protein of human immunodeficiency virus type 1 (HIV-1) with multiple functions. The induction of G2 arrest by Vpr plays a particularly important role in efficient viral replication because the transcriptional activity of the HIV-1 long terminal repeat is most active in G2 phase. The regulation of apoptosis by Vpr is also important for immune suppression and pathogenesis during HIV infection. However, it is not known whether Vpr-induced apoptosis depends on the ability of Vpr to induce G2 arrest, and the dynamics of Vpr-induced G2 arrest and apoptosis have not been visualized. We performed time-lapse imaging to examine the temporal relationship between Vpr-induced G2 arrest and apoptosis using HeLa cells containing the fluorescent ubiquitination-based cell cycle indicator2 (Fucci2). The dynamics of G2 arrest and subsequent long-term mitotic cell rounding in cells transfected with the Vpr-expression vector were visualized. These cells underwent nuclear mis-segregation after prolonged mitotic processes and then entered G1 phase. Some cells subsequently displayed evidence of apoptosis after prolonged mitotic processes and nuclear mis-segregation. Interestingly, Vpr-induced apoptosis was seldom observed in S or G2 phase. Likewise, visualization of synchronized HeLa/Fucci2 cells infected with an adenoviral vector expressing Vpr clearly showed that Vpr arrests the cell cycle at G2 phase, but does not induce apoptosis at S or G2 phase. Furthermore, time-lapse imaging of HeLa/Fucci2 cells expressing SCAT3.1, a caspase-3-sensitive fusion protein, clearly demonstrated that Vpr induces caspase-3-dependent apoptosis. Finally, to examine whether the effects of Vpr on G2 arrest and apoptosis were reversible, we performed live-cell imaging of a destabilizing domain fusion Vpr, which enabled rapid stabilization and destabilization by Shield1. The effects of Vpr on G2 arrest and subsequent apoptosis were reversible. This study is the first to characterize the dynamics of the morphological changes that occur during Vpr-induced G2 arrest and apoptosis.

Project description:AIM:To identify the differentially expressed proteins involved in ionizing radiation in mice and to explore new ways for studying radiation-related proteins. METHODS:Bal B/c mice grouped as sham-irradiation, 3 h and 72 h irradiation were exposed to 9.0 Gy single dose of gamma-irradiation. Intestinal epithelia were isolated from mice, and total proteins were extracted with urea containing solution. A series of methods were used, including two-dimensional electrophoresis, PDQuest 2-DE software analysis, peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and SWISS-PROT database searching, to separate and identify the differential proteins. Western blotting and RT-PCR were used to validate the differentially expressed proteins. RESULTS:Mouse intestine was severely damaged by 9.0 Gy gamma-irradiation. Image analysis of two-dimensional gels revealed that averages of 638 +/- 39, 566 +/- 32 and 591 +/- 29 protein spots were detected in 3 groups, respectively, and the majority of these protein spots were matched. About 360 protein spots were matched between normal group and 3 h irradiation group, and the correlation coefficient was 0.78 by correlation analysis of gels. Also 312 protein spots matched between normal group and 72 h irradiation group, and 282 protein spots between 3 h and 72 h irradiation groups. Twenty-eight differential protein spots were isolated from gels, digested with trypsin, and measured with MALDI-TOF-MS. A total of 25 spots yielded good spectra, and 19 spots matched known proteins after database searching. These proteins were mainly involved in anti-oxidation, metabolism, signal transduction, and protein post-translational processes. Western-blotting confirmed that enolase was up-regulated by gamma-irradiation. Up-regulation of peroxiredoxin I was verified by applying RT-PCR technique, but no change occurred in Q8VC72. CONCLUSION:These differentially expressed proteins might play important roles when mouse intestine was severely injured by gamma-irradiation. It is suggested that differential proteomic analysis may be a useful tool to study the proteins involved in radiation damage of mouse intestinal epithelia.

Dataset Information

Oxidation resistance 1 prevents genome instability through maintenance of G2/M arrest in gamma-ray-irradiated cells.

Publications

Oxidation resistance 1 prevents genome instability through maintenance of G2/M arrest in gamma-ray-irradiated cells.

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