Cis-acting elements reinforcing the activity of the estrogen-response element in the very-low-density apolipoprotein II gene promoter

Estrogen enhances the expression of a growth-associated long noncoding RNA in chicken liver via ERα

1. The long noncoding RNA lncGLM is significantly differentially expressed in the livers of peak-laying hens compared with that in the livers of pre-laying hens, but its potential biological role and expression regulation are unclear.2. To explore the potential biological function of lncGLM, single nucleotide polymorphism (SNP) detection and association analysis were carried out in the Gushi×Anka F₂ resource population.3. The tissues and spatiotemporal expression characteristics of lncGLM were analysed by real-time quantitative PCR. The effects of 17β-oestradiol on the expression of lncGLM expression were analysed through in vitro and in vivo experiments.4. The results showed that a g.19069338 T > C SNP was present in lncGLM. Association analysis revealed that lncGLM was significantly associated with body slanting length at 12 weeks, body weight at 12 weeks, shank length at four weeks, chest depth at eight weeks, pelvic width at 12 weeks, eviscerated weight, head weight, pancreas weight, pectoralis weight, leg muscle weight, muscular stomach weight rate, pancreas weight rate, carcase weight, aspartate aminotransferase, creatinine and pectoral muscle water loss rate.5. The expression of lncGLM in the liver was higher than that in other sampled tissues. In addition, the expression of lncGLM in the liver was significantly higher in the peak-laying period than at the pre-laying period. Both in vitro and in vivo experiments showed that lncGLM expression was regulated by 17β-oestradiol via oestrogen receptor alpha (ER-α). These results demonstrated that the chicken lncGLM gene is highly expressed in liver tissue and regulated by oestrogen through ER-α.

High-throughput screening for analysis of in vitro toxicity

The influence of combinatorial chemistry and high-throughput screening (HTS) technologies in the pharmaceutical industry during the last 10 years has been enormous. However, the attrition rate of drugs in the clinic due to toxicity during this period still remained 40-50%. The need for reduced toxicity failure led to the development of early toxicity screening assays. This chapter describes the state of the art for assays in the area of genotoxicity, cytotoxicity, carcinogenicity, induction of specific enzymes from phase I and II metabolism, competition assays for enzymes of phase I and II metabolism, embryotoxicity as well as endocrine disruption and reprotoxicity. With respect to genotoxicity, the full Ames, Ames II, Vitotox, GreenScreen GC, RadarScreen, and non-genotoxic carcinogenicity assays are discussed. For cytotoxicity, cellular proliferation, calcein uptake, oxygen consumption, mitochondrial activity, radical formation, glutathione depletion as well as apoptosis are described. For high-content screening (HCS), the possibilities for analysis of cytotoxicity, micronuclei, centrosome formation and phospholipidosis are examined. For embryotoxicity, endocrine disruption and reprotoxicity alternative assays are reviewed for fast track analysis by means of nuclear receptors and membrane receptors. Moreover, solutions for analyzing enzyme induction by activation of nuclear receptors, like AhR, CAR, PXR, PPAR, FXR, LXR, TR and RAR are given.

Hormone-induced recruitment of Sp1 mediates estrogen activation of the rabbit uteroglobin gene in endometrial epithelium

Steroid hormones activate gene expression by interaction of their receptors with hormone-responsive DNA elements and tissue-specific or ubiquitous factors. To monitor the molecular changes on the promoter of the rabbit uteroglobin gene during early pseudopregnancy in vivo, we have applied the genomic footprinting methodology to endometrial tissue. Estrogen induction results in the simultaneous occupancy of an estrogen-responsive element and an adjacent GC/GT box in the promoter. DNA binding assays demonstrate that the corresponding regulatory factors are the ligand-induced estrogen receptor and the ubiquitous transcription factor Sp1. Both factors functionally synergize in primary endometrial cells, showing that the GC/GT box is an essential part of a composite estrogen-responsive unit. However, the estrogen receptor and Sp1 do not bind cooperatively to their sites in vitro, suggesting that other mechanisms might be responsible for the hormone-dependent binding of Sp1 in vivo. Since hormone treatment leads to the appearance of a distinct DNase I-hypersensitive site over the promoter chromatin, an estrogen-induced change in the local chromatin structure could facilitate binding of Sp1 in vivo.

Differential stimulation by CCAAT/enhancer-binding protein alpha isoforms of the estrogen-activated promoter of the very-low-density apolipoprotein II gene

The transcription factors CCAAT/enhancer-binding proteins alpha and beta (C/EBP alpha and C/EBP beta) are highly expressed in liver and are believed to function in maintaining the differentiated state of the hepatocytes. C/EBP alpha appears to be a critical regulator of genes involved in metabolic processes. We are interested in the roles of C/EBP in the expression of the very-low-density apolipoprotein II (apoVLDL II) gene. This gene encodes an avian yolk protein, is induced by estrogens and is only expressed in liver. To examine the role of C/EBP in apoVLDL II expression, footprinting and electromobility-shift analysis were performed. For three of the protein-binding sites in the apoVLDL II promoter region, C/EBP alpha and C/EBP beta were identified as the major DNA-binding activities. For one of the C/EBP genes, C/EBP alpha, the effect of the gene products on apoVLDL II transcription was examined. From transfection experiments we conclude that maximal estrogen-dependent activity of the apoVLDL II promoter requires the dual action of the estrogen receptor and C/EBP. The level of activity is different depending on the nature of the C/EBP alpha translational isoform transfected, the full-length C/EBP alpha polypeptide being the most active isoform and the N-terminally truncated isoform being moderately active. The present results suggest a role of C/EBP alpha translational isoform ratio in the modulation of expression of C/EBP target genes, such as those involved in metabolic processes.

Human estrogen receptor (ER) gene promoter-P1: estradiol-independent activity and estradiol inducibility in ER+ and ER- cells

Estrogen receptor (ER) is expressed at a low level in normal tissues such as breast and uterus but at a high level in breast and endometrial carcinomas. A proximal element (ERF-1) located between positions +133 and +204 relative to the promoter P1 major initiation site has been recently identified in ER+ cells and contributes to the differential promoter activity between ER+ and ER- cells. In this study, MCF7 and HeLa cells were transfected with chloramphenicol acetyltransferase constructs containing ER gene promoter P1 sequences. We show here that the sequences lying between nucleotides +13 to +212 are also essential for transcription at the ER gene promoter P1 in ER- cells, which do not express ERF-1. Interestingly, on gel shift experiments, a complex specific to ER- cells forms in the region spanning nucleotides +123 to +210. We also show that promoter P1 is responsive to estradiol in cells expressing endogenous (MCF7) or exogenous ER. We further demonstrate, using mutational analysis and gel retardation assays, that the three half-estrogen response elements located between nucleotides -420 and -892 are responsible for the estradiol inducibility of promoter P1. Because estradiol has a mitogenic effect on both breast and endometrial epithelial cells, our data would give an insight into the role of estrogens in the occurrence of breast and endometrial carcinomas.