关键词： activating transcription factor 3 (Atf3)   early growth response 1 (Egr1)   hypertrophy   immediate early gene   microarray   negative feedback  

摘要： Endothelin-1 promotes cardiomyocyte hypertrophy by inducing changes in gene expression. Immediate early genes including Atf3 (activating transcription factor 3), Egr1 (early growth response 1) and Ptgs2 (prostaglandin-endoperoxide synthase 2) are rapidly and transiently up-regulated by endothelin-1 in cardiomyocytes. Atf3 regulates the expression of downstream genes and is implicated in negative feedback regulation of other immediate early genes. To identify Atf3-regulated genes, we knocked down Atf3 expression in cardiomyocytes exposed to endothelin-1 and used microarrays to interrogate the transcriptomic effects. The expression of 23 mRNAs (including Egr1 and Ptgs2) was enhanced and the expression of 25 mRNAs was inhibited by Atf3 knockdown. Using quantitative PCR, we determined that: knockdown of Atf3 had little effect on up-regulation of Egr1 mRNA over 30 min, but abolished the subsequent decline, causing sustained Egr1 mRNA expression and enhanced protein expression. This resulted from direct binding of Atf3 to the Egr1 promoter. Mathematical modelling established that Atf3 can suffice to suppress Egr1 expression. Given the widespread co-regulation of Atf3 with Egr1, we suggest that the Atf3-Egr1 negative feedback loop is of general significance. Loss of Atf3 caused abnormal cardiomyocyte growth, presumably resulting from the dysregulation of target genes. The results of the present study therefore identify Atf3 as a nexus in cardiomyocyte hypertrophy required to facilitate the full and proper growth response.

摘要： GnRH binds to its receptor on gonadotropes and activates multiple members of the MAPK signaling family that in turn regulates the expression of several immediate early genes (IEGs) including Jun, Fos, Atf3, and Egr1. These IEGs confer hormonal responsiveness to gonadotrope-specific genes including Gnrhr, Cga, Fshb, and Lhb. In this study we tested the hypothesis that GnRH specifically regulates the accumulation of Jun and Atf3 mRNA through a pathway that includes intracellular Ca2+, calcineurin, and nuclear factor of activated T cells (NFAT). Our results indicate that pretreatment of murine L beta T2 cells with 1, 2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)-ester, a Ca2+ chelator, reduced the expression of all the IEGs to varying degrees, whereas treatment with thapsigargin, an intracellular Ca2+ protein pump inhibitor, increased the expression of the IEG. Furthermore, cyclosporin A, a calcineurin-specific inhibitor, reduced the ability of GnRH to regulate accumulation of Jun and Atf3 mRNA and to a lesser extent Fos. In contrast, Egr1 mRNA was unaffected. NFATs are transcription factors regulated by calcineurin and were detected in L beta T2 cells. GnRH increased luciferase activity of an NFAT-dependent promoter reporter that was dependent on intracellular Ca2+ and calcineurin activity. Additionally, although small interfering RNA specific for Nfat4 only marginally reduced GnRH regulation of Jun, Fos, and Atf3 mRNA accumulation, activity of an activator protein-1-responsive reporter construct was reduced by 48%. Together these data suggest that calcineurin and NFAT are new members of the gonadotrope transcriptional network that confer hormonal responsiveness to several key genes required for gonadotropin synthesis and secretion. (Molecular Endocrinology 26: 873-886, 2012)

关键词： Adipocyte differentiation   Activating transcription factor 3 (ATF3)   CCAAT/enhancer-binding proteins alpha (C/EBP alpha)   Promoter   Hypoxia  

摘要： ATF3 is a stress-adaptive gene that regulates proliferation or apoptosis under stress conditions. However, the role of ATF3 is unknown in adipocyte cells. Therefore, in this study, we investigated the functional role of ATF3 in adipocytes. Both lentivirus-mediated overexpression of ATF3 and stably-overexpressed ATF3 inhibited adipocyte differentiation in 3T3-L1 cells, as revealed by decreased lipid staining with oil red staining and reduction in adipogenic genes. Thapsigargin treatment and overexpression of ATF3 decreased C/EBP alpha transcript and repressed the activity of the 3.6-kb mouse C/EBP alpha promoter, demonstrating that ATF3 downregulates C/EBP alpha expression. Transfection studies using mutant constructs containing 5'-deletions in the C/EBP alpha promoter revealed that a putative ATF/CRE element, GGATGTCA, is located between -1921 and -1914. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay demonstrated that ATF3 directly binds to mouse C/EBP alpha promoter spanning from -1928 to -1907. Both chemical hypoxia-mimetics or physical hypoxia led to reduce the C/EBP alpha mRNA and repress the promoter activity of the C/EBP alpha gene, whereas increase ATF3 mRNA, suggesting that ATF3 may contribute to the inhibition of adipocyte differentiation in hypoxia through downregulation of C/EBP alpha expression. Collectively, these results demonstrate that ATF3 represses the C/EBP alpha gene, resulting in inhibition of adipocyte differentiation, and thus plays a role in hypoxia-mediated inhibition of adipocyte differentiation. (C) 2012 Elsevier Inc. All rights reserved.

关键词： ATF3   Caspase 3   Schwann cell   Nerve regeneration   Diabetes   BB rat  

摘要： The aim of this study was to evaluate nerve regeneration in relation to the transcription factor, Activating Transcription Factor 3 (ATF 3), and an apoptotic marker, caspase 3, in the Schwann cells of diabetic BB rats (i.e. display type 1 diabetes phenotype). Sciatic nerves in healthy Wistar rats and in diabetic BB rats were transected and immediately repaired. Axonal outgrowth (neurofilament staining) and expression of ATF 3 and caspase 3 were quantified by immunohistochemistry after six days. There was no difference in axonal outgrowth between healthy and diabetic rats. However, the sciatic nerve in the diabetic rats exhibited a larger number of ATF 3 expressing Schwann cells at the site of the lesion and also a higher number of caspase 3 expressing Schwann cells. Similar differences were observed in the distal nerve segment between the healthy and diabetic rats. There were no correlations between the number of Schwann cells expressing ATF 3 and caspase 3. Thus, diabetic BB rats display an increased activation of ATF 3 and also a rise in apoptotic caspase 3 expressing Schwann cells, but with no discrepancy in length of axonal outgrowth after nerve injury and repair at six days. Knowledge about signal transduction mechanisms in diabetes after stress may provide new insights into the development of diabetic neuropathy and neuropathic pain. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

关键词： Cardiovascular biology  

摘要： Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipid-loaded macrophages in the arterial wall. We demonstrate that macrophage lipid body formation can be induced by modified lipoproteins or by inflammatory Toll-like receptor agonists. We used an unbiased approach to study the overlap in these pathways to identify regulators that control foam cell formation and atherogenesis. An analysis method integrating epigenomic and transcriptomic datasets with a transcription factor (TF) binding site prediction algorithm suggested that the TF ATF3 may regulate macrophage foam cell formation. Indeed, we found that deletion of this TF results in increased lipid body accumulation, and that ATF3 directly regulates transcription of the gene encoding cholesterol 25-hydroxylase. We further showed that production of 25-hydroxycholesterol (25-HC) promotes macrophage foam cell formation. Finally, deletion of ATF3 in Apoe(-/-) mice led to in vivo increases in foam cell formation, aortic 25-HC levels, and disease progression. These results define a previously unknown role for ATF3 in controlling macrophage lipid metabolism and demonstrate that ATF3 is a key intersection point for lipid metabolic and inflammatory pathways in these cells.

关键词： ATF3   电离辐射   细胞凋亡   DNA损伤修复  

摘要： 目的阐明辐射损伤中ATF3蛋白诱导表达的生物学功能及其调控机制,为探讨辐射损伤防护的新方法提供依据。方法 HCT116(Tet-off)细胞分为4组,即对照组(细胞未进行任何处理)、诱导组(加入诺考达唑诱导ATF3蛋白表达)、照射组(单纯接受射线照射)、照射+诱导组(细胞加入诺考达唑诱导ATF3蛋白表达后接受射线照射)。流式细胞术分析细胞周期变化。Caspase decay分析细胞凋亡。克隆形成率测定细胞增殖。结果与对照组相比较,诱导组细胞周期出现G1期阻滞。表达ATF3蛋白的细胞内出现Caspase 3和多聚ADP-核糖聚合酶(PARP)裂解,对照组则未出现2种蛋白的裂解。诱导组的细胞克隆形成率(15.09%)低于对照组(21.13%),但高于照射组(2.25%)和照射+诱导组(5.24%)。结论 ATF3表达可诱导细胞周期G1阻滞、细胞凋亡和增殖能力下降,且对于受照射的细胞可能有一定的辐射保护作用。

关键词： DR5   ATF3   p53   CPT   TRAIL  

摘要： Stress response gene ATF3 is one of the p53 target genes and has a tumor suppressor role in cancer. However, the biological role of p53-ATF3 pathway is not well understood. Death receptor 5 (DR5) is a death domain-containing transmembrane receptor that triggers cell death upon binding to its ligand TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), and a combination of TRAIL and agents that increase the expression of DR5 is expected as a novel anticancer therapy. In this report, we demonstrate that ATF3 is required for efficient DR5 induction upon DNA damage by camptothecin (CPT) in colorectal cancer cells. In the absence of ATF3, induction of DR5 messenger RNA and protein is remarkably abrogated, and this is associated with reduced cell death by TRAIL and CPT. By contrast, exogenous expression of ATF3 causes more rapid and elevated expression of DR5, resulting in enhanced sensitivity to apoptotic cell death by TRAIL/CPT. Reporter assay and DNA affinity precipitation assay demonstrate that at least three ATF/CRE motifs at the proximal promoter of the human DR5 gene are involved in the activation of DNA damage-induced DR5 gene transcription. Furthermore, ATF3 is shown to interact with p53 to form a complex on the DR5 gene by Re-chromatin immunoprecipitation assay. Taken together, our results provide a novel insight into the role of ATF3 as an essential co-transcription factor for p53 upon DNA damage, and this may represent a useful biomarker for TRAIL-based anticancer therapy. Oncogene (2012) 31, 2210-2221;doi:10.1038/onc.2011.397;published online 19 September 2011

关键词： ATF3   EGR-1   ROS   Patulin  

摘要： Patulin is a fungal mycotoxin of Aspergilus and Penicillium that is commonly found in rotting fruits and exerts its potential toxic effect mainly by reactive oxygen species (ROS) generation. However, the effect of patulin on cancer cells as well as its intracellular mechanism has been controversial and not clearly defined yet In this study, patulin was found to induce G1/S accumulation and cell growth arrest accompanied by caspase-3 activation, PARP cleavage and ATF3 expression in human colon cancer cell line HCT116. Ser/Thr phosphorylation of a transcription factor. EGR-1, was increased while its expression did not change upon patulin treatment to the cells. Knockdown of ATF3 and EGR-1 using their respective siRNAs showed EGR-1 dependent ATF3 expression. Moreover, treatment of the cells with antioxidants N-acetylcysteine (NAC) and glutathione (GSH) revealed that patulin induced ATF3 expression and apoptosis were dependent on ROS generation. ATF3 expression was also increased by patulin in other colorectal cancer cell types, Caco2 and SW620. Collectively, our data present a new anti-cancer molecular mechanism of patulin, suggesting EGR-1 and ATF3 as critical targets for the development of anti-cancer chemotherapeutics. In this regard, patulin could be a candidate for the treatment of colorectal cancers. (C) 2011 Elsevier Inc. All rights reserved.