scholarly journals Epigenetic silencing of the XAF1 gene is mediated by the loss of CTCF binding

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Georgina Victoria-Acosta ◽  
Karla Vazquez-Santillan ◽  
Luis Jimenez-Hernandez ◽  
Laura Muñoz-Galindo ◽  
Vilma Maldonado ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Suppressor Gene ◽  
Tumour Suppressor Gene ◽  
Epigenetic Silencing ◽  
Ctcf Binding ◽  
Open Chromatin ◽  
Cpg Dinucleotide

Abstract XAF1 is a tumour suppressor gene that compromises cell viability by modulating different cellular events such as mitosis, cell cycle progression and apoptosis. In cancer, the XAF1 gene is commonly silenced by CpG-dinucleotide hypermethylation of its promoter. DNA demethylating agents induce transcriptional reactivation of XAF1, sensitizing cancer cells to therapy. The molecular mechanisms that mediate promoter CpG methylation have not been previously studied. Here, we demonstrate that CTCF interacts with the XAF1 promoter in vivo in a methylation-sensitive manner. By transgene assays, we demonstrate that CTCF mediates the open-chromatin configuration of the XAF1 promoter, inhibiting both CpG-dinucleotide methylation and repressive histone posttranslational modifications. In addition, the absence of CTCF in the XAF1 promoter inhibits transcriptional activation induced by well-known apoptosis activators. We report for the first time that epigenetic silencing of the XAF1 gene is a consequence of the loss of CTCF binding.

Promoter-associated small double-stranded RNA interacts with heterogeneous nuclear ribonucleoprotein A2/B1 to induce transcriptional activation

2012 ◽  
Vol 447 (3) ◽  
pp. 407-416 ◽  
Author(s):  
Jia Hu ◽  
Zhong Chen ◽  
Ding Xia ◽  
Jia Wu ◽  
Hua Xu ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Activation ◽  
Mammalian Cells ◽  
Kinase Inhibitor ◽  
Suppressor Gene ◽  
Tumour Suppressor Gene ◽  
Double Stranded Rna ◽  
P21 Promoter

Several recent reports have demonstrated that small activating dsRNA [double-stranded RNA; saRNA (small activating dsRNA)] complementary to promoter regions can up-regulate gene expression in mammalian cells, a phenomenon termed RNAa (RNA activation). However, the mechanism of RNAa remains obscure with regard to what is the target molecule for promoter-targeted saRNA and what are the proteins involved in this process. p21Waf1/Cip1 (p21) [CDKN1A (cyclin-dependent kinase inhibitor 1A)], an important tumour suppressor gene, is among the genes that can be activated by RNAa in tumour cells. In the present study, we provide direct evidence that p21 promoter-targeted saRNA interact with its intended target on the p21 promoter to activate p21 expression. This process is associated with recruitment of RNA polymerase II and AGO2 (argonaute 2) protein to the saRNA-target site. Additionally, we found that several hnRNPs (heterogeneous nuclear ribonucleoproteins) (A1, A2/B1 and C1/C2) are associated with saRNA. Further studies show that hnRNPA2/B1 interacts with the saRNA in vivo and in vitro and is required for RNAa activity. These findings indicate that RNAa results from specific targeting of promoters and reveals additional mechanistic details of RNAa.

Analysis of Saccharomyces cerevisiae his3 transcription in vitro: biochemical support for multiple mechanisms of transcription

1990 ◽  
Vol 10 (6) ◽  
pp. 2832-2839
Author(s):  
A S Ponticelli ◽  
K Struhl
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcriptional Activation ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Initiation Site ◽  
Activator Proteins ◽  
Nuclear Extracts ◽  
Transcription In Vitro

The promoter region of the Saccharomyces cerevisiae his3 gene contains two TATA elements, TC and TR, that direct transcription initiation to two sites designated +1 and +13. On the basis of differences between their nucleotide sequences and their responsiveness to upstream promoter elements, it has previously been proposed that TC and TR promote transcription by different molecular mechanisms. To begin a study of his3 transcription in vitro, we used S. cerevisiae nuclear extracts together with various DNA templates and transcriptional activator proteins that have been characterized in vivo. We demonstrated accurate transcription initiation in vitro at the sites used in vivo, transcriptional activation by GCN4, and activation by a GAL4 derivative on various gal-his3 hybrid promoters. In all cases, transcription stimulation was dependent on the presence of an acidic activation region in the activator protein. In addition, analysis of promoters containing a variety of TR derivatives indicated that the level of transcription in vitro was directly related to the level achieved in vivo. The results demonstrated that the in vitro system accurately reproduced all known aspects of in vivo his3 transcription that depend on the TR element. However, in striking contrast to his3 transcription in vivo, transcription in vitro yielded approximately 20 times more of the +13 transcript than the +1 transcript. This result was not due to inability of the +1 initiation site to be efficiently utilized in vitro, but rather it reflects the lack of TC function in vitro. The results support the idea that TC and TR mediate transcription from the wild-type promoter by distinct mechanisms.

scholarly journals Sentinel interaction mapping – a generic approach for the functional analysis of human disease gene variants using yeast

2020 ◽  
Vol 13 (7) ◽  
pp. dmm044560
Author(s):  
Barry P. Young ◽  
Kathryn L. Post ◽  
Jesse T. Chao ◽  
Fabian Meili ◽  
Kurt Haas ◽  
...  
Keyword(s):  
Genetic Variants ◽  
Human Disease ◽  
Disease Gene ◽  
Suppressor Gene ◽  
Tumour Suppressor Gene ◽  
Disease Genes ◽  
Gene Variants ◽  
Human Disease Gene ◽  
Simple Growth

ABSTRACTAdvances in sequencing technology have led to an explosion in the number of known genetic variants of human genes. A major challenge is to now determine which of these variants contribute to diseases as a result of their effect on gene function. Here, we describe a generic approach using the yeast Saccharomyces cerevisiae to quickly develop gene-specific in vivo assays that can be used to quantify the level of function of a genetic variant. Using synthetic dosage lethality screening, ‘sentinel’ yeast strains are identified that are sensitive to overexpression of a human disease gene. Variants of the gene can then be functionalized in a high-throughput fashion through simple growth assays using solid or liquid media. Sentinel interaction mapping (SIM) has the potential to create functional assays for the large majority of human disease genes that do not have a yeast orthologue. Using the tumour suppressor gene PTEN as an example, we show that SIM assays can provide a fast and economical means to screen a large number of genetic variants.

scholarly journals Molecular Mechanisms Underlying Yatein-Induced Cell-Cycle Arrest and Microtubule Destabilization in Human Lung Adenocarcinoma Cells

Cancers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1384 ◽  
Author(s):  
Shang-Tse Ho ◽  
Chi-Chen Lin ◽  
Yu-Tang Tung ◽  
Jyh-Horng Wu
Keyword(s):  
Cell Cycle ◽  
Antitumor Activity ◽  
Lung Adenocarcinoma ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Human Lung ◽  
Microtubule Dynamics ◽  
Cycle Progression ◽  
Human Lung Adenocarcinoma

Yatein is an antitumor agent isolated from Calocedrus formosana Florin leaves extract. In our previous study, we found that yatein inhibited the growth of human lung adenocarcinoma A549 and CL1-5 cells by inducing intrinsic and extrinsic apoptotic pathways. To further uncover the effects and mechanisms of yatein-induced inhibition on A549 and CL1-5 cell growth, we evaluated yatein-mediated antitumor activity in vivo and the regulatory effects of yatein on cell-cycle progression and microtubule dynamics. Flow cytometry and western blotting revealed that yatein induces G2/M arrest in A549 and CL1-5 cells. Yatein also destabilized microtubules and interfered with microtubule dynamics in the two cell lines. Furthermore, we evaluated the antitumor activity of yatein in vivo using a xenograft mouse model and found that yatein treatment altered cyclin B/Cdc2 complex expression and significantly inhibited tumor growth. Taken together, our results suggested that yatein effectively inhibited the growth of A549 and CL1-5 cells possibly by disrupting cell-cycle progression and microtubule dynamics.

scholarly journals New Enlightenment of Skin Cancer Chemoprevention through Phytochemicals:In VitroandIn VivoStudies and the Underlying Mechanisms

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Madhulika Singh ◽  
Shankar Suman ◽  
Yogeshwer Shukla
Keyword(s):  
Skin Cancer ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Cancer Chemoprevention ◽  
Chemopreventive Agents ◽  
Novel Approach ◽  
Comprehensive Knowledge ◽  
Underlying Mechanisms

Skin cancer is still a major cause of morbidity and mortality worldwide. Skin overexposure to ultraviolet irradiations, chemicals, and several viruses has a capability to cause severe skin-related disorders including immunosuppression and skin cancer. These factors act in sequence at various steps of skin carcinogenesis via initiation, promotion, and/or progression. These days cancer chemoprevention is recognized as the most hopeful and novel approach to prevent, inhibit, or reverse the processes of carcinogenesis by intervention with natural products. Phytochemicals have antioxidant, antimutagenic, anticarcinogenic, and carcinogen detoxification capabilities thereby considered as efficient chemopreventive agents. Considerable efforts have been done to identify the phytochemicals which may possibly act on one or several molecular targets that modulate cellular processes such as inflammation, immunity, cell cycle progression, and apoptosis. Till date several phytochemicals in the light of chemoprevention have been studied by using suitable skin carcinogenicin vitroandin vivomodels and proven as beneficial for prevention of skin cancer. This revision presents a comprehensive knowledge and the main molecular mechanisms of actions of various phytochemicals in the chemoprevention of skin cancer.

scholarly journals Transcription Factor Fli1 Regulates Collagen Fibrillogenesis in Mouse Skin

2008 ◽  
Vol 29 (2) ◽  
pp. 425-434 ◽  
Author(s):  
Yoshihide Asano ◽  
Margaret Markiewicz ◽  
Masahide Kubo ◽  
Gabor Szalai ◽  
Dennis K. Watson ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activation ◽  
Molecular Mechanisms ◽  
Mrna Level ◽  
Mouse Skin ◽  
Dermal Fibroblasts ◽  
Acid Extraction ◽  
Fibrillar Collagen ◽  
Cultured Fibroblasts

ABSTRACT Biosynthesis of fibrillar collagen in the skin is precisely regulated to maintain proper tissue homeostasis; however, the molecular mechanisms involved in this process remain largely unknown. Transcription factor Fli1 has been shown to repress collagen synthesis in cultured dermal fibroblasts. This study investigated the role of Fli1 in regulation of collagen biosynthesis in mice skin in vivo using mice with the homozygous deletion of the C-terminal transcriptional activation (CTA) domain of the Fli1 gene (Fli1ΔCTA/ΔCTA). Skin analyses of the Fli1 mutant mice revealed a significant upregulation of fibrillar collagen genes at mRNA level, as well as increased collagen content as measured by acetic acid extraction and hydroxyproline assays. In addition, collagen fibrils contained ultrastructural abnormalities including immature thin fibrils and very thick irregularly shaped fibrils, which correlated with the reduced levels of decorin, fibromodulin, and lumican. Fibroblasts cultured from the skin of Fli1ΔCTA/ΔCTA mice maintained elevated synthesis of collagen mRNA and protein. Additional experiments in cultured fibroblasts have revealed that although Fli1 ΔCTA retains the ability to bind to the collagen promoter in vitro and in vivo, it no longer functions as transcriptional repressor. Together, these results establish Fli1 as a key regulator of the collagen homeostasis in the skin in vivo.

scholarly journals STAT3 controls myeloid progenitor growth during emergency granulopoiesis

Blood ◽  
2010 ◽  
Vol 116 (14) ◽  
pp. 2462-2471 ◽  
Author(s):  
Huiyuan Zhang ◽  
Hoainam Nguyen-Jackson ◽  
Athanasia D. Panopoulos ◽  
Haiyan S. Li ◽  
Peter J. Murray ◽  
...  
Keyword(s):  
Intracellular Signaling ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Signaling Cascades ◽  
Regulation Of Transcription ◽  
Conditional Deletion ◽  
Myeloid Progenitor ◽  
Enhancer Binding Protein ◽  
Transcription 3

Abstract Granulocyte colony-stimulating factor (G-CSF) mediates “emergency” granulopoiesis during infection, a process that is mimicked by clinical G-CSF use, yet we understand little about the intracellular signaling cascades that control demand-driven neutrophil production. Using a murine model with conditional deletion of signal transducer and activator of transcription 3 (STAT3) in bone marrow, we investigated the cellular and molecular mechanisms of STAT3 function in the emergency granulopoiesis response to G-CSF administration or infection with Listeria monocytogenes, a pathogen that is restrained by G-CSF signaling in vivo. Our results show that STAT3 deficiency renders hematopoietic progenitor cells and myeloid precursors refractory to the growth-promoting functions of G-CSF or L monocytogenes infection. STAT3 is necessary for accelerating granulocyte cell-cycle progression and maturation in response to G-CSF. STAT3 directly controls G-CSF–dependent expression of CCAAT-enhancer-binding protein β (C/EBPβ), a crucial factor in the emergency granulopoiesis response. Moreover, STAT3 and C/EBPβ coregulate c-Myc through interactions with the c-myc promoter that control the duration of C/EBPα occupancy during demand-driven granulopoiesis. These results place STAT3 as an essential mediator of emergency granulopoiesis by its regulation of transcription factors that direct G-CSF–responsive myeloid progenitor expansion.

scholarly journals SUMO Represses Transcriptional Activity of the Drosophila SoxNeuro and Human Sox3 Central Nervous System–specific Transcription Factors

2005 ◽  
Vol 16 (6) ◽  
pp. 2660-2669 ◽  
Author(s):  
Jean Savare ◽  
Nathalie Bonneaud ◽  
Franck Girard
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Acceptor Site ◽  
Hmg Box ◽  
Sumo Modification

Sry high mobility group (HMG) box (Sox) transcription factors are involved in the development of central nervous system (CNS) in all metazoans. Little is known on the molecular mechanisms that regulate their transcriptional activity. Covalent posttranslational modification by small ubiquitin-like modifier (SUMO) regulates several nuclear events, including the transcriptional activity of transcription factors. Here, we demonstrate that SoxNeuro, an HMG box-containing transcription factor involved in neuroblast formation in Drosophila, is a substrate for SUMO modification. SUMOylation assays in HeLa cells and Drosophila S2 cells reveal that lysine 439 is the major SUMO acceptor site. The sequence in SoxNeuro targeted for SUMOylation, IKSE, is part of a small inhibitory domain, able to repress in cis the activity of two adjacent transcriptional activation domains. Our data show that SUMO modification represses SoxNeuro transcriptional activity in transfected cells. Overexpression in Drosophila embryos of a SoxN form that cannot be targeted for SUMOylation strongly impairs the development of the CNS, suggesting that SUMO modification of SoxN is crucial for regulating its activity in vivo. Finally, we present evidence that SUMO modification of group B1 Sox factors was conserved during evolution, because Sox3, the human counterpart of SoxN, is also negatively regulated through SUMO modification.

scholarly journals Cyclin D3-CDK6 Complex Facilitates Tumorigenesis by Regulating the C-Myc/miR-15a/16 Axis in a Feedback Loop in Gastric Cancer

2020 ◽  
Author(s):  
Yeting Hong ◽  
Wei He ◽  
Jianbin Zhang ◽  
Lu Shen ◽  
Chong Yu ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Cell Cycle ◽  
Cell Proliferation ◽  
Feedback Loop ◽  
Cell Cycle Progression ◽  
Molecular Mechanisms ◽  
Cyclin D3 ◽  
Luciferase Reporter

Abstract Background: Cyclin D3-CDK6 complex is a component of the core cell cycle machinery that regulates cell proliferation. By using Human Protein Atlas database, a higher expression level of this complex was found in gastric cancer. However, the function of this complex in gastric cancer remain poorly understood. This study aims to determine the expression pattern of this complex in gastric cancer and to investigate its biological role during tumorigenesis.Methods: To demonstrate that Cyclin D3-CDK6 regulate the c-Myc/miR-15a/16 axis in a feedback loop in gastric cancer, a series of methods were conducted both in vitro and in vivo experiments, including qRT-PCR, western blot analysis, EdU assay, flow cytometry, luciferase reporter assay and immunohistochemical staining. SPSS and Graphpad prism software were used for data analysis.Results: In this study, we found that Cyclin D3 and CDK6 were significantly upregulated in gastric cancer and correlated with poorer overall survival. Further study proved that this complex significantly promoted cell proliferation and cell cycle progression in vitro and accelerated xenografted tumor growth in vivo. Furthermore, we explored the molecular mechanisms through which the complex mediated Rb phosphorylation and then promoted c-Myc expression in vitro, we also found c-Myc could suppress miR-15a/16 expression in gastric cancer cell. Finally, we found that miR-15a/16 can simultaneously regulate Cyclin D3 and CDK6 expression as direct target genes.Conclusions: Our findings uncover the Cyclin D3-CDK6/c-Myc/miR-15a/16 feedback loop axis as a pivotal role in the regulation of gastric cancer tumorigenesis, and this regulating axis may provide a potential therapeutic target for gastric cancer treatment.

scholarly journals CLDN6 Suppresses c–MYC–Mediated Aerobic Glycolysis to Inhibit Proliferation by TAZ in Breast Cancer

2021 ◽  
Vol 23 (1) ◽  
pp. 129
Author(s):  
Huinan Qu ◽  
Da Qi ◽  
Xinqi Wang ◽  
Yuan Dong ◽  
Qiu Jin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Molecular Mechanisms ◽  
Aerobic Glycolysis ◽  
Lactate Production ◽  
Suppressor Gene ◽  
Binding Motif ◽  
Cancer Proliferation ◽  
In Vivo Experiments

Claudin 6 (CLDN6) was found to be a breast cancer suppressor gene, which is lowly expressed in breast cancer and inhibits breast cancer cell proliferation upon overexpression. However, the mechanism by which CLDN6 inhibits breast cancer proliferation is unclear. Here, we investigated this issue and elucidated the molecular mechanisms by which CLDN6 inhibits breast cancer proliferation. First, we verified that CLDN6 was lowly expressed in breast cancer tissues and that patients with lower CLDN6 expression had a worse prognosis. Next, we confirmed that CLDN6 inhibited breast cancer proliferation through in vitro and in vivo experiments. As for the mechanism, we found that CLDN6 inhibited c–MYC–mediated aerobic glycolysis based on a metabolomic analysis of CLDN6 affecting cellular lactate levels. CLDN6 interacted with a transcriptional co–activator with PDZ-binding motif (TAZ) and reduced the level of TAZ, thereby suppressing c–MYC transcription, which led to a reduction in glucose uptake and lactate production. Considered together, our results suggested that CLDN6 suppressed c–MYC–mediated aerobic glycolysis to inhibit the proliferation of breast cancer by TAZ, which indicated that CLDN6 acted as a novel regulator of aerobic glycolysis and provided a theoretical basis for CLDN6 as a biomarker of progression in breast cancer.

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