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DNA promoter methylation-dependent transcription of the double C2-like domain ? (DOC2B) gene regulates tumor growth in human cervical cancer.

ABSTRACT: Double C2-like domain ? (DOC2B) gene encodes for a calcium-binding protein, which is involved in neurotransmitter release, sorting, and exocytosis. We have identified the promoter region of the DOC2B gene as hypermethylated in pre-malignant, malignant cervical tissues, and cervical cancer cell lines by methylation-sensitive dimethyl sulfoxide-polymerase chain reaction and bisulfite genome sequencing; whereas, it was unmethylated in normal cervical tissues (p < 0.05). The promoter hypermethylation was inversely associated with mRNA expression in SiHa, CaSki, and HeLa cells and treatment with demethylating agent 5-aza-2-deoxycytidine restored DOC2B expression. The region -630 to +25 bp of the DOC2B gene showed robust promoter activity by a luciferase reporter assay and was inhibited by in vitro artificial methylation with Sss1 methylase prior to transient transfections. Overexpression of the DOC2B gene in SiHa cells when compared with controls showed significantly reduced colony formation, cell proliferation, induced cell cycle arrest, and repressed cell migration and invasion (p < 0.05). Ectopic expression of DOC2B resulted in anoikis-mediated cell death and repressed tumor growth in a nude mice xenograft model (p < 0.05). DOC2B expressing cells showed a significant increase in intracellular calcium level (p < 0.05), impaired AKT1 and ERK1/2 signaling, and induced actin cytoskeleton remodeling. Our results show that promoter hypermethylation and silencing of the DOC2B gene is an early and frequent event during cervical carcinogenesis and whose reduced expression due to DNA promoter methylation may lead to selective cervical tumor growth.

SUBMITTER: Kabekkodu SP

PROVIDER: S-EPMC4036182 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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DNA promoter methylation-dependent transcription of the double C2-like domain β (DOC2B) gene regulates tumor growth in human cervical cancer.

Kabekkodu Shama Prasada SP Bhat Samatha S Radhakrishnan Raghu R Aithal Abhijit A Mascarenhas Roshan R Pandey Deeksha D Rai Lavanya L Kushtagi Pralhad P Mundyat Gopinath Puthiya GP Satyamoorthy Kapaettu K

The Journal of biological chemistry 20140225 15

Double C2-like domain β (DOC2B) gene encodes for a calcium-binding protein, which is involved in neurotransmitter release, sorting, and exocytosis. We have identified the promoter region of the DOC2B gene as hypermethylated in pre-malignant, malignant cervical tissues, and cervical cancer cell lines by methylation-sensitive dimethyl sulfoxide-polymerase chain reaction and bisulfite genome sequencing; whereas, it was unmethylated in normal cervical tissues (p < 0.05). The promoter hypermethylatio ...[more]

PMID: 24570007

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Project description:BackgroundThe Escherichia coli response regulator NarL controls transcription of genes involved in nitrate respiration during anaerobiosis. NarL consists of two domains joined by a linker that wraps around the interdomain interface. Phosphorylation of the NarL N-terminal receiver domain (RD) releases the, otherwise sequestered, C-terminal output domain (OD) that subsequently binds specific DNA promoter sites to repress or activate gene expression. The aim of this study is to investigate the extent to which the NarL OD and RD function independently to regulate transcription, and the affect of the linker on OD function.ResultsNarL OD constructs containing different linker segments were examined for their ability to repress frdA-lacZ or activate narG-lacZ reporter fusion genes. These in vivo expression assays revealed that the NarL OD, in the absence or presence of linker helix α6, constitutively repressed frdA-lacZ expression regardless of nitrate availability. However, the presence of the linker loop α5-α6 reversed this repression and also showed impaired DNA binding in vitro. The OD alone could not activate narG-lacZ expression; this activity required the presence of the NarL RD. A footprint assay demonstrated that the NarL OD only partially bound recognition sites at the narG promoter, and the binding affinity was increased by the presence of the phosphorylated RD. Analytical ultracentrifugation used to examine domain oligomerization showed that the NarL RD forms dimers in solution while the OD is monomeric.ConclusionsThe NarL RD operates as an on-off switch to occlude or release the OD in a nitrate-responsive manner, but has additional roles to directly stimulate transcription at promoters for which the OD lacks independent function. One such role of the RD is to enhance the DNA binding affinity of the OD to target promoter sites. The data also imply that NarL phosphorylation results in RD dimerization and in the separation of the entire linker region from the OD.

Project description:DNA methylation, and consequent down-regulation, of tumour suppressor genes occurs in response to epigenetic stimuli during cancer development. Similarly, human oncoviruses, including human papillomavirus (HPV), up-regulate and augment DNA methyltransferase (DNMT) and histone deacetylase (HDAC) activities, thereby decreasing tumour suppressor genes (TSGs) expression. Ubiquitin-like containing PHD and RING finger domain 1 (UHRF1), an epigenetic regulator of DNA methylation, is overexpressed in HPV-induced cervical cancers. Here, we investigated the role of UHRF1 in cervical cancer by knocking down its expression in HeLa cells using lentiviral-encoded short hairpin (sh)RNA and performing cDNA microarrays. We detected significantly elevated expression of thioredoxin-interacting protein (TXNIP), a known TSG, in UHRF1-knockdown cells, and this gene is hypermethylated in cervical cancer tissue and cell lines, as indicated by whole-genome methylation analysis. Up-regulation of UHRF1 and decreased TXNIP were further detected in cervical cancer by western blot and immunohistochemistry and confirmed by Oncomine database analysis. Using chromatin immunoprecipitation, we identified the inverted CCAAT domain-containing UHRF1-binding site in the TXNIP promoter and demonstrated UHRF1 knockdown decreases UHRF1 promoter binding and enhances TXNIP expression through demethylation of this region. TXNIP promoter CpG methylation was further confirmed in cervical cancer tissue by pyrosequencing and methylation-specific polymerase chain reaction. Critically, down-regulation of UHRF1 by siRNA or UHRF1 antagonist (thymoquinone) induces cell cycle arrest and apoptosis, and ubiquitin-specific protease 7 (USP7), which stabilises and promotes UHRF1 function, is increased by HPV viral protein E6/E7 overexpression. These results indicate HPV might induce carcinogenesis through UHRF1-mediated TXNIP promoter methylation, thus suggesting a possible link between CpG methylation and cervical cancer.

Project description:BackgroundClooxygenase-2 (COX-2) expression is overexpressed in human prostate cancer, and aberrant methylation of the COX-2 promoter has also been elucidated. However, how the methylation of CpG islands at COX-2 regulates its expression in prostate cancer is still unclear. We will determine the methylated 5' CpG island of the COX-2 gene and its role in the expression of COX-2 in prostate androgen-dependent and androgen-independent cancer cells, LNCaP and DU145.MethodsWe used western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to confirm the COX-2 expression in prostate cancer cell lines, including LNCaP (androgen-dependent) and DU145 (androgen-independent) cells. To investigate whether the COX-2 expression was regulated by the methylation status of the 5' CpG island, we treated LNCaP and DU145 cells with the DNA methylation inhibitor, 5-aza-2'-deoxycytidine, and determined COX-2 expression in the treated/untreated cells by western blotting and qRT-PCR. Subsequently, bisulfite sequencing was performed to study the methylation sites in the treated/untreated cells. The effects of 5-aza-2'-deoxycytidine to cell proliferation, cell migration and cell cycle process in DU145 and LNCaP cells were determined using Cell Counting Kit-8 (CCK-8) assay, transwell assay and flow cytometry, respectively.ResultsThe results revealed that the expression of COX-2 in androgen-dependent LNCaP cells was 5.44-fold (in protein level) and 2.46-fold (in mRNA level) higher than that in androgen-independent DU145 cells. After 5-aza-2'-deoxycytidine treatment, COX-2 expression in DU145 cells was elevated significantly, but no change was found in LNCaP cells. The A and C regions of the COX-2 CpG island exhibited reduced methylation along with that an increased expression of COX-2 was noted in DU145 cell after 5-aza-2'-deoxycytidine treatment. Also, the treatment with 5-aza-2'-deoxycytidine inhibited cell proliferation, cell migration and influenced the cell cycle progression in both DU145 and LNCaP cells.ConclusionsOur results reveal that androgen receptor (AR)-dependent/independent prostate cancer cell lines exhibit different regulation of methylation in COX-2 that regulate its expression. Additionally, 5-aza-2'-deoxycytidine treatment of DU145 and LNCaP cells inhibits their ability of tumor progression.

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DNA promoter methylation-dependent transcription of the double C2-like domain ? (DOC2B) gene regulates tumor growth in human cervical cancer.

Publications

DNA promoter methylation-dependent transcription of the double C2-like domain β (DOC2B) gene regulates tumor growth in human cervical cancer.

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