Laboratory of Cytogenetics and Tissue Regeneration

Seoul, South Korea

Laboratory of Cytogenetics and Tissue Regeneration

Seoul, South Korea
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Ahn J.,Korea Research Institute of Bioscience and Biotechnology | Ahn J.,Chungnam National University | Choi J.-H.,Korea Research Institute of Bioscience and Biotechnology | Won M.,Korea Research Institute of Bioscience and Biotechnology | And 6 more authors.
Biochemical and Biophysical Research Communications | Year: 2011

The Ras-related small GTP-binding protein RhoB is rapidly induced in response to genotoxic stresses caused by ionizing radiation. It is known that UV-induced RhoB expression results from the binding of activating transcription factor 2 (ATF2) via NF-Y to the inverted CCAAT box (-23) of the RhoB promoter. Here, we show that the association of c-Jun with the distal CCAAT box (-72) is primarily involved in UV-induced RhoB expression and p38 MAPK regulated RhoB induction through the distal CCAAT box. UV-induced RhoB expression and apoptosis were markedly attenuated by pretreatment with the p38 MAPK inhibitor. siRNA knockdown of RhoB, ATF2 and c-Jun resulted in decreased RhoB expression and eventually restored the growth of UV-irradiated Jurkat cells. In the reporter assay using luciferase under the RhoB promoter, inhibition of RhoB promoter activity by the p38 inhibitor and knockdown of c-Jun using siRNA occurred through the distal CCAAT box. Immunoprecipitation and DNA affinity protein binding assays revealed the association of c-Jun and p300 via NF-YA and the dissociation of histone deacetylase 1 (HDAC1) via c-Jun recruitment to the CCAAT boxes of the RhoB promoter. These results suggest that the activation of p38 MAPK primarily contributes to UV-induced RhoB expression by recruiting the c-Jun and p300 proteins to the distal CCAAT box of the RhoB promoter in Jurkat cells. © 2011 Elsevier Inc.


Ahn J.,Korea Research Institute of Bioscience and Biotechnology | Ahn J.,Chungnam National University | Won M.,Korea Research Institute of Bioscience and Biotechnology | Choi J.-H.,Korea Research Institute of Bioscience and Biotechnology | And 6 more authors.
Biochemical and Biophysical Research Communications | Year: 2012

The small heat-shock protein Hsp9 from Schizosaccharomyces pombe was previously reported to be a homologue of Saccharomyces cerevisiae HSP12. Although Hsp9 is expressed in response to heat shock and nutritional limitation, its function is still not completely understood. Here, we explored the biological function of Hsp9 in S. pombe. The hsp9 gene might play a role in stress adaptation; hsp9 deletion caused heat sensitivity and overexpression induced heat tolerance. In addition, Hsp9 also contribute to cell cycle regulation in the nucleus. Δ. hsp9 cells grew more quickly and were shorter in length than wild-type cells. Moreover, Δ. hsp9 cells did not achieve checkpoint arrest under stress conditions, leading to cell death, and exhibited a short doubling time and short G2 phase. Overexpression of hsp9 induced cell cycle delay, increased the population of G2 phase cells, and rescued the phenotypes of cdc2-33, cdc25-22, Δ. rad24, and Δ. rad25 mutants, suggesting that Hsp9 probably regulates Cdc2 phosphorylation by modulating the Cdc25 activity. Indeed, immunoprecipitation experiments revealed that Hsp9 is associated with 14-3-3 and Cdc25. In Δ. hsp9 cells, the association of 14-3-3 with Cdc25 was weakened and Cdc2 phosphorylaton was reduced. Together, our data suggest that Hsp9 has dual functions in stress adaptation and regulating a G2-M checkpoint by the Cdc25 inactivation; this differs from S. cerevisiae HSP12, which maintains cell membrane stability under stress conditions. © 2011 Elsevier Inc.


Kim C.-H.,Laboratory of Cytogenetics and Tissue Regeneration | Won M.,Korea Research Institute of Bioscience and Biotechnology | Choi C.-H.,Korea Research Institute of Bioscience and Biotechnology | Ahn J.,Korea Research Institute of Bioscience and Biotechnology | And 4 more authors.
Biochemical and Biophysical Research Communications | Year: 2010

The Ras-related small GTP-binding protein RhoB is known to be a pro-apoptotic protein and immediate-early inducible by genotoxic stresses. In addition, JNK activation is known to function in γ-radiation-induced apoptosis. However, it is unclear how JNK activation and γ-radiation-dependent RhoB induction are related. Here we verified the relationship between JNK activation and RhoB induction. RhoB induction by γ-radiation occurred at the transcriptional level and transcriptional activation of RhoB was concomitant with an increase in RhoB protein. γ-Radiation-induced RhoB expression was markedly attenuated by pretreatment with a JNK-specific inhibitor, SP600125, but not by a p38 MAPK inhibitor, SB203580. Inhibition of JNK caused a decrease in early apoptotic cell death that correlated with RhoB expression. However, PI3K inhibition had no significant effects, indicating that the AKT survival pathway was not involved. The siRNA knockdown of JNK resulted in a decrease in RhoB expression and the siRNA knockdown of RhoB restored cell growth even in the γ-irradiated cells. These results suggest that RhoB regulation involves the JNK pathway and contributes to the early apoptotic response of Jurkat T cells to γ-radiation. © 2009 Elsevier Inc. All rights reserved.


PubMed | Laboratory of Cytogenetics and Tissue Regeneration
Type: Journal Article | Journal: Biochemical and biophysical research communications | Year: 2010

The Ras-related small GTP-binding protein RhoB is known to be a pro-apoptotic protein and immediate-early inducible by genotoxic stresses. In addition, JNK activation is known to function in gamma-radiation-induced apoptosis. However, it is unclear how JNK activation and gamma-radiation-dependent RhoB induction are related. Here we verified the relationship between JNK activation and RhoB induction. RhoB induction by gamma-radiation occurred at the transcriptional level and transcriptional activation of RhoB was concomitant with an increase in RhoB protein. gamma-Radiation-induced RhoB expression was markedly attenuated by pretreatment with a JNK-specific inhibitor, SP600125, but not by a p38 MAPK inhibitor, SB203580. Inhibition of JNK caused a decrease in early apoptotic cell death that correlated with RhoB expression. However, PI3K inhibition had no significant effects, indicating that the AKT survival pathway was not involved. The siRNA knockdown of JNK resulted in a decrease in RhoB expression and the siRNA knockdown of RhoB restored cell growth even in the gamma-irradiated cells. These results suggest that RhoB regulation involves the JNK pathway and contributes to the early apoptotic response of Jurkat T cells to gamma-radiation.

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