p53 cooperates with Sp1 to regulate breed-dependent expression of glucocorticoid receptor in the liver of preweaning piglets

Distinct Patterns of GR Transcriptional Regulation in Liver and Muscle of LPS-Challenged Weaning Piglets

Glucocorticoid receptor (GR), which is ubiquitously expressed in nearly all cell types of various organs, mediates the tissue-specific metabolic and immune responses to maintain homeostasis and ensure survival under stressful conditions or pathological challenges. The neonatal period is metabolically demanding, and piglets are subjected to multiple stressors in modern intensive farms, especially around weaning. The liver is more responsive to LPS challenge compared to muscle, which is indicated by significantly increased TLR4 and p-p65, TNF-α, and IL-6 levels in association with GR down-regulation at both mRNA and protein levels. GR binding to the putative nGRE on TNF-α and IL-6 gene promoters decreased in the liver, but not muscle, upon LPS stimulation. The transcriptional regulation of GR also showed striking differences between liver and muscle. GR exon 1 mRNA variants 1–4, 1–5, and 1–6 were down-regulated in both liver and muscle, but a significant up-regulation of GR exon 1–9/10 mRNA variants abolished the change of total GR mRNA in the muscle in response to LPS stimulation. The significant down-regulation of GR in the liver corresponded with significantly decreased binding of p-GR and diminished histone acetylation in GR gene promoters. These results indicate that tissue-specific GR transcriptional regulation is involved in the differential inflammation responses between liver and muscle.

Cell-specific expression of ENACα gene by FOXA1 in the glucocorticoid receptor pathway

Introduction:

The glucocorticoid receptor (GR) is one of the most widely studied ligand-dependent nuclear receptors. The combination of transcriptional regulatory factors required for the expression of individual genes targeted by GR varies across cell types; however, the mechanisms underlying this cell type–specific regulation of gene expression are not yet clear.

Methods:

Here, we investigated genes regulated by GR in two different cell lines, A549 and ARPE-19, and examined how gene expression varied according to the effect of pioneer factors using RNA-seq and RT-qPCR.

Results:

Our RNA-seq results identified 19 and 63 genes regulated by GR that are ARPE-19-specific and A549-specific, respectively, suggesting that GR induces the expression of different sets of genes in a cell type–specific manner. RT-qPCR confirmed that the epithelial sodium channel (ENACα) gene is an ARPE-19 cell-specific GR target gene, whereas the FK506 binding protein 5 (FKBP5) gene was A549 cell-specific. There was a significant decrease in ENACα expression in FOXA1-deficient ARPE-19 cells, suggesting that FOXA1 might function as a pioneer factor enabling the selective expression of ENACα in ARPE-19 cells but not in A549 cells.

Conclusion:

These findings indicate that ENACα expression in ARPE-19 cells is regulated by FOXA1 and provide insights into the molecular mechanisms of cell type–specific expression of GR-regulated genes.

Roles of alternative splicing in modulating transcriptional regulation

Background

The ability of a transcription factor to regulate its targets is modulated by a variety of genetic and epigenetic mechanisms. Alternative splicing can modulate gene function by adding or removing certain protein domains, and therefore affect the activity of protein. Reverse engineering of gene regulatory networks using gene expression profiles has proven valuable in dissecting the logical relationships among multiple proteins during the transcriptional regulation. However, it is unclear whether alternative splicing of certain proteins affects the activity of other transcription factors.

Results

In order to investigate the roles of alternative splicing during transcriptional regulation, we constructed a statistical model to infer whether the alternative splicing events of modulator proteins can affect the ability of key transcription factors in regulating the expression levels of their transcriptional targets. We tested our strategy in KIRC (Kidney Renal Clear Cell Carcinoma) using the RNA-seq data downloaded from TCGA (the Cancer Genomic Atlas). We identified 828of modulation relationships between the splicing levels of modulator proteins and activity levels of transcription factors. For instance, we found that the activity levels of GR (glucocorticoid receptor) protein, a key transcription factor in kidney, can be influenced by the splicing status of multiple proteins, including TP53, MDM2 (mouse double minute 2 homolog), RBM14 (RNA-binding protein 14) and SLK (STE20 like kinase). The influenced GR-targets are enriched by key cancer-related pathways, including p53 signaling pathway, TR/RXR activation, CAR/RXR activation, G1/S checkpoint regulation pathway, and G2/M DNA damage checkpoint regulation pathway.

Conclusions

Our analysis suggests, for the first time, that exon inclusion levels of certain regulatory proteins can affect the activities of many transcription factors. Such analysis can potentially unravel a novel mechanism of how splicing variation influences the cellular function and provide important insights for how dysregulation of splicing outcome can lead to various diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0465-6) contains supplementary material, which is available to authorized users.

Glucocorticoid receptor is involved in the differential expression of hepatic 3β-hydroxysteroid dehydrogenase between barrows and boars at finishing stage

The enzyme 3β-hydroxysteroid dehydrogenase (3β-HSD) plays an important role in androstenone metabolism in pig liver, and its defective expression is related to the development of boar taint. Early age castration is a common practice in many countries to avoid boar taint, yet whether and how castration affects porcine hepatic 3β-HSD expression are still poorly understood. In this study, we aimed to compare the expression of 3β-HSD between intact (boars) and castrated (barrows) male pigs, and to explore the potential factors regulating 3β-HSD transcription. Compared to barrows, boars showed worse carcass quality. Boars had significantly higher levels of serum androstenone (P < 0.01), testosterone (P < 0.01) and hepatic cortisol (P < 0.05), which were contrary to significantly lower expression of 3β-HSD messenger RNA (P < 0.01) and protein (P < 0.01) in the liver. Significant differences were detected for the hepatic expression of androgen receptor (AR) and CCAAT/enhancer binding protein β (C/EBPβ). Chromatin immunoprecipitation (ChIP) assay demonstrated reduced histone H3 acetylation (P < 0.05) but increased glucocorticoid receptor (GR) binding to 3β-HSD gene promoter in boars (P < 0.05). These results indicate that GR binding to 3β-HSD promoter is involved in the differential hepatic 3β-HSD expression between boars and barrows.

Potential of Environmental Enrichment to Prevent Transgenerational Effects of Paternal Trauma

Adverse experiences in early life are risk factors for the development of behavioral and physiological symptoms that can lead to psychiatric and cognitive disorders later in life. Some of these symptoms can be transmitted to the offspring, in some cases by non-genomic mechanisms involving germ cells. Using a mouse model of unpredictable maternal separation and maternal stress, we show that postnatal trauma alters coping behaviors in adverse conditions in exposed males when adult and in their adult male progeny. The behavioral changes are accompanied by increased glucocorticoid receptor (GR) expression and decreased DNA methylation of the GR promoter in the hippocampus. DNA methylation is also decreased in sperm cells of exposed males when adult. Transgenerational transmission of behavioral symptoms is prevented by paternal environmental enrichment, an effect associated with the reversal of alterations in GR gene expression and DNA methylation in the hippocampus of the male offspring. These findings highlight the influence of both negative and positive environmental factors on behavior across generations and the plasticity of the epigenome across life.

Survivin in survival of hepatocellular carcinoma

Survivin is an anti-apoptotic protein belonging to the inhibitor of apoptosis protein (IAP) family. It is involved in the regulation of important physiological and pathological processes in cells and functions to inhibit cell apoptosis and promote cell proliferation. Normally and terminally differentiated tissues are nearly negative for survivin. In contrast, survivin is highly expressed in most human tumor tissues, including hepatocellular carcinoma (HCC). The abnormal overexpression of survivin is closely related to the malignant biological behaviors of tumors. During the development and progression of HCC, the high level of survivin expression promotes cancer cell proliferation, inhibits cancer cell apoptosis, induces tumor stromal angiogenesis, reduces the sensitivity of cancer cells to radiotherapy and chemotherapy, and ultimately affects the prognosis of patients with HCC. Survivin expression is regulated by a large number of factors. The latest discovery indicated that the transcription factor octamer-binding transcription factor 4 (OCT4) enhances the expression of survivin though cyclin D1 (CCND1), which, in part, accounts for tumor cell proliferation, recurrence and metastasis. Survivin plays key roles in HCC, which renders it an ideal target for the treatment of HCC. The present article reviews the research progress on the relationship between survivin and HCC and on the HCC treatment strategies targeting survivin.