• Food Science of Animal Resources
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• v.30 no.5
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• pp.787-794
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• 2010

Calcium plays a role as a signaling molecule in various cellular events. It has been reported that calcium suppresses adipocyte differentiation only in the early phase of adipogenesis. Herein, we demonstrate that treatment of A23187, a mobilizer of intracellular calcium, on day 4 post adipocyte differentiation could still reduce lipid accumulation in differentiating 3T3-L1 cells for 48 h. In addition, luciferase reporter gene and RT-Q-PCR assays demonstrate that A23187 can selectively inhibit transcriptional activities and expression of PPAR$\gamma$ and LXR$\alpha$, suggesting that A23187 may reduce lipid accumulation in the late phase of adipogenesis via downregulation of PPAR$\gamma$ and LXR$\alpha$ expression and transactivation. Moreover, inhibition of HDAC activity by trichostatin A (TSA) partially blocked A23187-mediated downregulation of transcriptional activities of PPAR$\gamma$ and LXR$\alpha$. Together, our data demonstrate that calcium mobilization inhibits expression and transcriptional activities of PPAR$\gamma$ and LXR$\alpha$, resulting in reduced lipid accumulation in differentiating adipocytes, and thus, mobilization of intracellular calcium in adipocytes may serve as a new preventive and therapeutic approach for obesity.

• Environmental Mutagens and Carcinogens
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• v.24 no.4
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• pp.171-179
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• 2004

Cytochrome P4503A4(CYP3A4) is the most abundnat CYPs in human liver, comparising approximately 30% of the total liver CYPs contents ans is involbed in the metabolism of more than 60% of currently used therapeutic drugs. The expression of CYP3A4 is induced by a variety of structurally unrelated xonobiotics including the antibiotic rifampicin and endogenous hormones, and might be mediated through steroid and xenobiotic receptor(SXR) system. The molecular mechanisms underlying regulation of CYP3A4 gene expression hae not been understood. In order to gain the insight of the molecular mechanism of CYP3A4 gene expression, study has been undertaken to investigate if the histone deacelylation is involved in the regulation of CYP3A4 gene expression by proximal promoter or not. Also SXR was investigated to see if they were involved in the regulation of CYP3A4 proximal promoter activity. HepG2 or Hena-I cells were transfected with a plasmid containing~1kb of the CYP3A4 proximal promoter region (-863 to +64bp) cloned in front of a reporter gene, luciferase, in the presence or absence of SXR or hER. Transfected cells were treated with CYP3A4 inducers such as rifampicin, PCN and RU 486, or with estradiol, in order to exmine to regulation of CYP3A4 gene expression in the presence or absence of trichostatin A (TSA). In HepG2 cells, CYP3A4 inducers and estradiol increased significantly the luciferase activity by CYP3A4 proximal promoter, only when TSA was co-treated after SXR cotransfection. In the case of Hepa-I cells CYP3A4 inducers and estradiol incressed modestly the luciferase activity when TSA was co-treated, but this increment was not enhanced by SXR cotransfection in contrast to HepG2 cells. Taken together, these results indicated that the inhibition of histone deacetylation was required to SXR-mediated increase in CYP3A4 proximal promoter region when rifampicin, or PCN was treated. Futher a trans-activation by SXR may demand other species-specific transcription factors.

• Animal Bioscience
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• v.37 no.6
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• pp.1021-1030
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• 2024

Objective: R-loops are DNA:RNA triplex hybrids, and their metabolism is tightly regulated by transcriptional regulation, DNA damage response, and chromatin structure dynamics. R-loop homeostasis is dynamically regulated and closely associated with gene transcription in mouse zygotes. However, the factors responsible for regulating these dynamic changes in the R-loops of fertilized mouse eggs have not yet been investigated. This study examined the functions of candidate factors that interact with R-loops during zygotic gene activation. Methods: In this study, we used publicly available next-generation sequencing datasets, including low-input ribosome profiling analysis and polymerase II chromatin immunoprecipitation-sequencing (ChIP-seq), to identify potential regulators of R-loop dynamics in zygotes. These datasets were downloaded, reanalyzed, and compared with mass spectrometry data to identify candidate factors involved in regulating R-loop dynamics. To validate the functions of these candidate factors, we treated mouse zygotes with chemical inhibitors using in vitro fertilization. Immunofluorescence with an anti-R-loop antibody was then performed to quantify changes in R-loop metabolism. Results: We identified DEAD-box-5 (DDX5) and histone deacetylase-2 (HDAC2) as candidates that potentially regulate R-loop metabolism in oocytes, zygotes and two-cell embryos based on change of their gene translation. Our analysis revealed that the DDX5 inhibition of activity led to decreased R-loop accumulation in pronuclei, indicating its involvement in regulating R-loop dynamics. However, the inhibition of histone deacetylase-2 activity did not significantly affect R-loop levels in pronuclei. Conclusion: These findings suggest that dynamic changes in R-loops during mouse zygote development are likely regulated by RNA helicases, particularly DDX5, in conjunction with transcriptional processes. Our study provides compelling evidence for the involvement of these factors in regulating R-loop dynamics during early embryonic development.

• Radiation Oncology Journal
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• v.22 no.2
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• pp.138-141
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• 2004

Purpose : We have previously reported that human glioblastoma cells are sensitized to radiation-induced death after their exposure to trichostatin A (TSA), a histone deacetylase inhibitor (HDAC-1), prior to the irradiation. We aimed to measure the magnitude of the radiosensitizing effect of TSA in human head and neck cancer cell lines. Materials and Methods : Human head and neck cancer cell lines, HN-3 and HN-9, were exposed to 0, 50, 100, and 200 nM TSA for 18 hr prior to irradiation. Then, the TSA-treated cells were irradiated with 0, 2, 4, 6, and 8 Gy, and cell survival was measured by clonogenic assay. Results : Pre-irradiation exposure to TSA was found to radiosensitize HN-3 and HN-9 cell lines. In HN-9 cells, the fraction surviving after 2 Gy (SF2) was significantly reduced by treatment of TSA at concentration as low as 50 nM. However, a treatment with 200 nM TSA was required to significantly decrease SF2 in the HN-3 cell line. SER of pre-irradiation treatment with 200 nM TSA was 1.84 in HN-3 and 7.24 in HN-9, respectively. Conclusions : Our results clearly showed that human head and neck cancer cell lines can be sensitized to ionizing radiation by pre-irradiation inhibition of histone deacetylase (HDAC) using TSA, and that this potentiation might well be a general phenomenon.