Biomedical subjects

Elizabeth A Edwards

Publications and source records attributed to Elizabeth A Edwards.

At least 19 recordsLinked to original sources

PubMed2006

Identification and expression of benzylsuccinate synthase genes in a toluene-degrading methanogenic consortium.

Benzylsuccinate synthase (BSS) initiates anaerobic toluene biodegradation, and BSS genes have been found in several nitrate- and iron-reducing organisms. Here, two new putative bssA genes were identified in a methanogenic toluene-degrading culture. Transcription was upregulated with toluene but not with benzoate, consistent with the proposed function. These are the first bss sequences from a methanogenic culture.

Base Sequence↗

PubMed2006

A 1,1,1-trichloroethane-degrading anaerobic mixed microbial culture enhances biotransformation of mixtures of chlorinated ethenes and ethanes.

1,1,1-trichloroethane (1,1,1-TCA) is a common groundwater pollutant as a result of improper disposal and accidental spills. It is often found as a cocontaminant with trichloroethene (TCE) and inhibits some TCE-degrading microorganisms. 1,1,1-TCA removal is therefore required for effective bioremediation of sites contaminated with mixed chlorinated organics. This study characterized MS, a 1,1,1-TCA-degrading, anaerobic, mixed microbial culture derived from a 1,1,1-TCA-contaminated site in the northeastern United States. MS reductively dechlorinated 1,1,1-TCA to 1,1-dichloroethane (1,1-DCA) and then to monochloroethane (CA) but not further. Cloning of bacterial 16S rRNA genes revealed among other organisms the presence of a Dehalobacter sp. and a Desulfovibrio sp., which are both phylogenetically related to known dehalorespiring strains. Monitoring of these populations with species-specific quantitative PCR during degradation of 1,1,1-TCA and 1,1-DCA showed that Dehalobacter proliferated during dechlorination. Dehalobacter growth was dechlorination dependent, whereas Desulfovibrio growth was dechlorination independent. Experiments were also performed to test whether MS could enhance TCE degradation in the presence of inhibiting levels of 1,1,1-TCA. Dechlorination of cis-dichloroethene (cDCE) and vinyl chloride (VC) in KB-1, a chloroethene-degrading culture used for bioaugmentation, was inhibited with 1,1,1-TCA present. When KB-1 and MS were coinoculated, degradation of cDCE and VC to ethene proceeded as soon as the 1,1,1-TCA was dechlorinated to 1,1-DCA by MS. This demonstrated the potential application of the MS and KB-1 cultures for cobioaugmentation of sites cocontaminated with 1,1,1-TCA and TCE.

Bacteria, Anaerobic↗

PubMed2006

Heparin derivatives as inhibitors of BACE-1, the Alzheimer's beta-secretase, with reduced activity against factor Xa and other proteases.

Heparan sulfate (HS) regulates processing of the amyloid precursor protein by the Alzheimer's beta-secretase (BACE-1). An HS analogue, porcine intestinal mucosal heparin, was systematically modified at the principal positions of O-sulfation and N-sulfation/acetylation and tested for BACE-1 inhibitory and anti factor Xa activities. The derivative with the highest anti-BACE-1 to anti-Xa activity ratio contained N-acetyl and 2-O- and 6-O-sulfates and also exhibited attenuated activities against cathepsin-D and renin, two other structurally related aspartyl proteases.

Alzheimer Disease↗

PubMed2006

Evaluation of isotopic enrichment factors for the biodegradation of chlorinated ethenes using a parameter estimation model: toward an improved quantification of biodegradation.

A model was developed to predict the concentrations of chlorinated ethenes and ethene during sequential reductive dechlorination of tetrachloroethene (PCE) from stable carbon isotope values using Rayleigh model principles and specified isotopic enrichment factors for each step of dechlorination. The model was tested using three separate datasets of concentration and isotope values measured during three experiments involving the degradation of PCE to vinyl chloride (VC), trichloroethene (TCE) to ethene, and cis-1,2-dichloroethene (cDCE) to ethene. The model was then coupled to a parameter estimation method to estimate values for the isotopic enrichment factors of TCE, cDCE, and VC when they are intermediates in the dechlorination to ethene. The enrichment factors estimated for TCE and cDCE when they were intermediates in biodegradation experiments were close to or within the published range of enrichment factors determined from experiments where TCE or cDCE were the initial substrates. In contrast, the enrichment factors determined by parameter estimation for experiments in which VC was an intermediate in biodegradation experiments were consistently more negative (by approximately 10 per thousandth) than the most negative published enrichment factor determined from experiments where VC was the initial substrate. This finding suggests that the range of enrichment factors for VC dechlorination may not be as narrow as previously suggested (-21.5 per thousandth to -26.6 per thousandth) and that fractionation during VC dechlorination when VC is an intermediate compound may be significantly larger than when VC is the initial substrate. These findings have important implications both for the current practice of extrapolating laboratory-derived isotopic enrichment factors to quantify biodegradation of chlorinated ethenes in the field and for understanding the details of enzymatic reductive dechlorination.

Biodegradation, Environmental↗

PubMed2006

Biological enhancement of tetrachloroethene dissolution and associated microbial community changes.

A bench-scale study was performed to evaluate the enhancement of tetrachloroethene (PCE) dissolution from a dense nonaqueous phase liquid (DNAPL) source zone due to reductive dechlorination. The study was conducted in a pair of two-dimensional bench-scale aquifer systems using soil and groundwater from Dover Air Force Base, DE. After establishment of PCE source zones in each aquifer system, one was biostimulated (addition of electron donor) while the other was biostimulated and then bioaugmented with the KB1 dechlorinating culture. Biostimulation resulted in the growth of iron-reducing bacteria (Geobacter) in both systems as a result of the high iron content of the Dover soil. After prolonged electron donor addition methanogenesis dominated, but no dechlorination was observed. Following bioaugmentation of one system, dechlorination to ethene was achieved, coincident with growth of introduced Dehalococcoides and other microbes in the vicinity and downgradient of the PCE DNAPL (detected using DGGE and qPCR). Dechlorination was not detected in the nonbioaugmented system over the course of the study, indicating that the native microbial community, although containing a member of the Dehalococcoides group, was not able to dechlorinate PCE. Over 890 days, 65% of the initial emplaced PCE was removed in the bioaugmented, dechlorinating system, in comparison to 39% removal by dissolution from the nondechlorinating system. The maximum total ethenes concentration (3 mM) in the bioaugmented system occurred approximately 100 days after bioaugmentation, indicating that there was at least a 3-fold enhancement of PCE dissolution atthis time. Removal rates decreased substantially beyond this time, particularly during the last 200 days of the study, when the maximum concentrations of total ethenes were only about 0.5 mM. However, PCE removal rates in the dechlorinating system remained more than twice the removal rates of the nondechlorinating system. The reductions in removal rates over time are attributed to both a shrinking DNAPL source area, and reduced flow through the DNAPL source area due to bioclogging and pore blockage from methane gas generation.

Biodegradation, Environmental↗

PubMed2006

Harnessing microbial activities for environmental cleanup.

Human activities have released large amounts of toxic organic and inorganic chemicals into the environment. Toxic waste streams threaten dwindling drinking water supplies and impact terrestrial, estuarine and marine ecosystems. Cleanup is technically challenging and the costs based on traditional technologies are exceeding the economic capabilities of even the richest countries. Recent advances in our understanding of the microbiology contributing to contaminant transformation and detoxification has led to successful field demonstrations. Hence, harnessing the activity of naturally occurring bacteria, particularly the power of anaerobic reductive processes, is a promising approach to restore contaminated subsurface environments, protect drinking water reservoirs and to safeguard ecosystem health.

Drug Delivery Systems↗

PubMed2006

Microbial composition of chlorinated ethene-degrading cultures dominated by Dehalococcoides.

The community composition of microbial cultures degrading tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) to ethene was studied. A combination of PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and 16S rRNA gene sequence analysis revealed that all cultures contained Dehalococcoides populations, but that the populations of other organisms varied widely. Based on the sequences of cloned 16S rRNA genes, real-time PCR methods were developed for several of these phylotypes affiliated with the putative dechlorinators Sulfurospirillum and Geobacter, the putative methanogens Methanomethylovorans, Methanomicrobiales, Methanosaeta and Methanosarcina, the putative acetogens Acetobacterium, Spirochaetes, and Sporomusa, and the putative fermenters Bacteroidetes, Syntrophus, and Syntrophobacter. These novel quantitative PCR methods were then used to estimate relative abundances of each phylotype in several individual cultures maintained on each chlorinated ethene. Dehalococcoides populations were the dominant phylotypes assayed in most KB-1 cultures, agreeing with the DGGE and cloning results. A Geobacter phylotype was also strongly represented in most PCE and TCE cultures, but not in cDCE or VC cultures, suggesting a possible role for this organism as a PCE-to-cDCE dechlorinator. The Sulfurospirillum phylotype was estimated to comprise a minor fraction of 16S rRNA gene copies and did not appear to have an important role in dechlorination.

Bacteria↗

PubMed2006

Growth of Dehalobacter and Dehalococcoides spp. during degradation of chlorinated ethanes.

Mixed anaerobic microbial subcultures enriched from a multilayered aquifer at a former chlorinated solvent disposal facility in West Louisiana were examined to determine the organism(s) involved in the dechlorination of the toxic compounds 1,2-dichloroethane (1,2-DCA) and 1,1,2-trichloroethane (1,1,2-TCA) to ethene. Sequences phylogenetically related to Dehalobacter and Dehalococcoides, two genera of anaerobic bacteria that are known to respire with chlorinated ethenes, were detected through cloning of bacterial 16S rRNA genes. Denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments after starvation and subsequent reamendment of culture with 1,2-DCA showed that the Dehalobacter sp. grew during the dichloroelimination of 1,2-DCA to ethene, implicating this organism in degradation of 1,2-DCA in these cultures. Species-specific real-time quantitative PCR was further used to monitor proliferation of Dehalobacter and Dehalococcoides during the degradation of chlorinated ethanes and showed that in fact both microorganisms grew simultaneously during the degradation of 1,2-DCA. Conversely, Dehalobacter grew during the dichloroelimination of 1,1,2-TCA to vinyl chloride (VC) but not during the subsequent reductive dechlorination of VC to ethene, whereas Dehalococcoides grew only during the reductive dechlorination of VC but not during the dichloroelimination of 1,1,2-TCA. This demonstrated that in mixed cultures containing multiple dechlorinating microorganisms, these organisms can have either competitive or complementary dechlorination activities, depending on the chloro-organic substrate.

Anaerobiosis↗

PubMed2005

Metabolites detected during biodegradation of 13C6-benzene in nitrate-reducing and methanogenic enrichment cultures.

The mechanism for anaerobic metabolism of benzene remains unknown. To date, there have been only a few studies reporting metabolites of anaerobic benzene biodegradation, in part because anaerobic benzene-degrading enrichment cultures are not very common and only two isolates have been characterized to date. Phenol and benzoate, metabolites consistent with benzene hydroxylation or benzene carboxylation, have been identified previously in mixed cultures, and more recently benzene methylation to toluene has been proposed as another possible mechanism for anaerobic benzene degradation. In this study, 13C6-benzene was added to nitrate-reducing and methanogenic enrichment cultures and specific 13C-labeled metabolites were monitored over time. The putative metabolites were detected by gas chromatography/mass spectrometry in ether extracts of 100-mL samples of culture taken at each time point. This method of analysis provided the sensitivity required to accurately quantify low concentrations of these compounds. In addition, benzoate trapping was used in an attemptto increase concentrations of upstream metabolites. In both cultures, in the presence and absence of unlabeled benzoate (trap), [ring-13C]-toluene and [ring-13C]benzoate were detected transiently during degradation. The data strongly support initial methylation of benzene to toluene, followed bytransformation to benzoate. Although benzene methylation has been proposed previously, this is the first direct evidence to supportthis pathway. In the methanogenic culture only, 13C6-phenol was also detected. The transient appearance of phenol, which appeared to be further transformed to benzoate, suggests that a pathway involving hydroxylation to phenol, as proposed in other studies, was also operative.

Anaerobiosis↗

PubMed2005

Carbon isotopic fractionation during aerobic vinyl chloride degradation.

Vinyl chloride (VC) is a carcinogenic contaminant commonly found in groundwater. Much research has focused on anaerobic reductive dechlorination of VC, and recently on aerobic VC degradation. In this study, the stable carbon isotope enrichment factor associated with aerobic VC assimilation was determined for Mycobacterium sp. strains JS60, JS61, and JS617 and Nocardioides sp. strain JS614. The enrichment factors ranged from -8.2+/-0.1 to -7.0+/-0.3 % and did not change as a function of biomass concentration. The measured enrichment factors for aerobic VC degradation were smaller than those reported for anaerobic VC degradation. Enrichment factors can also be expressed in terms of kinetic isotope effects (KIEs), 12k/13k, which result from the difference in reaction rates of bonds containing light and heavy isotopes. The KIEs for aerobic VC degradation (1.01+/-0.001) were smaller than those for anaerobic VC degradation (1.03+/-0.007). From the perspective of bond breakage during a chemical reaction, the larger KIE associated with anaerobic VC degradation as compared to aerobic VC degradation agrees with KIE theory. This theory predicts that larger fractionations can be expected in reactions where heavier atoms are involved (i.e., C-Cl bond for anaerobic versus C=C for aerobic) and in reactions involving large changes in vibrational frequencies of the molecule between its ground state and transition state (i.e., C-Cl cleavage versus C=C epoxidation). The significant fractionation observed during aerobic VC degradation suggests that stable carbon isotope measurements may be used as a tool to distinguish between biodegraded and nonbiodegraded VC.

Bacteria, Aerobic↗

PubMed2005

Quantifying chlorinated ethene degradation during reductive dechlorination at Kelly AFB using stable carbon isotopes.

Stable isotope analysis of chlorinated ethene contaminants was carried out during a bioaugmentation pilot test at Kelly Air Force Base (AFB) in San Antonio Texas. In this pilot test, cis-1,2-dichloroethene (cDCE) was the primary volatile organic compound. A mixed microbial enrichment culture, KB-1, shown in laboratory experiments to reduce chlorinated ethenes to non-toxic ethene, was added to the pilot test area. Following bioaugmentation with KB-1, perchloroethene (PCE), trichloroethene (TCE) and cDCE concentrations declined, while vinyl chloride (VC) concentrations increased and subsequently decreased as ethene became the dominant transformation product. Shifts in carbon isotopic values up to 2.7 per thousand, 6.4 per thousand, 10.9 per thousand and 10.6 per thousand were observed for PCE, TCE, cDCE and VC, respectively, after bioaugmentation, consistent with the effects of biodegradation. While a rising trend of VC concentrations and the first appearance of ethene were indicative of biodegradation by 72 days post-bioaugmentation, the most compelling evidence of biodegradation was the substantial carbon isotope enrichment (2.0 per thousand to 5.0 per thousand) in ä13C(cDCE). Fractionation factors obtained in previous laboratory studies were used with isotope field measurements to estimate first-order cDCE degradation rate constants of 0.12 h(-1) and 0.17 h(-1) at 115 days post-bioaugmentation. These isotope-derived rate constants were clearly lower than, but within a factor of 2-4 of the previously published rate constant calculated in a parallel study at Kelly AFB using chlorinated ethene concentrations. Stable carbon isotopes can provide not only a sensitive means for early identification of the effects of biodegradation, but an additional means to quantify the rates of biodegradation in the field.

Biodegradation, Environmental↗

PubMed2005

Multiple reductive-dehalogenase-homologous genes are simultaneously transcribed during dechlorination by Dehalococcoides-containing cultures.

Degenerate primers were used to amplify 14 distinct reductive-dehalogenase-homologous (RDH) genes from the Dehalococcoides-containing mixed culture KB1. Most of the corresponding predicted proteins were highly similar (97 to >99% amino acid identity) to previously reported Dehalococcoides reductive dehalogenases. To examine the differential transcription of these RDH genes, KB1 was split into five subcultures amended with either trichloroethene, cis-1,2-dichloroethene, vinyl chloride, 1,2-dichlorethane, or no chlorinated electron acceptor. Total RNA was extracted following the onset of reductive dechlorination, and RDH transcripts were reverse transcribed and amplified using degenerate primers. The results indicate that the transcription of RDH genes requires the presence of a chlorinated electron acceptor, and for all treatments, multiple RDH genes were simultaneously transcribed, with transcripts of two of the genes being present under all four electron-accepting conditions. Two of the transcribed sequences were highly similar to reported vinyl chloride reductase genes, namely, vcrA from Dehalococcoides sp. strain VS and bvcA from Dehalococcoides sp. strain BAV1. These findings suggest that multiple RDH genes are induced by a single chlorinated substrate and that multiple reductive dehalogenases contribute to chloroethene degradation in KB1.

Base Sequence↗

PubMed2004

Gene expression profiles for detecting and distinguishing potential endocrine-disrupting compounds in environmental samples.

Industrial and municipal processes may produce and release endocrine-disrupting compounds (EDCs) into the environment, but the exact nature of their effects is difficult to investigate. EDCs typically exert their effect by affecting gene expression aberrantly. To determine if gene expression profiles could be used to detect and distinguish estrogenic EDCs, an estrogen receptor positive human breast cancer cell line (MCF-7) was exposed to known estrogenic compounds, suspected EDCs, and extracts from three effluent samples. A set of specifically estrogen-regulated genes was identified by microarray analysis. Nine estrogen up-regulated genes (IGFBP4, HSPA8, B4GALT1, XBP1, KRT8, GTPBP4, HNRPAB, SLC2A1, and CALM1) and two estrogen down-regulated genes (ID2 and ZNF217) were consistently detectable in response to estrogen and other estrogenic compounds. Gene expression patterns in cells that were exposed to effluent sample extracts were compared to gene expression patterns in cells that were exposed to known endocrines. Using this technique, two of the effluent samples were shown to have estrogenic activity. This approach could easily be extended to screen for other types of receptor-mediated endocrine disruption. For example, cells expressing androgen or aryl hydrocarbon receptors could be used in gene expression profiling assays to detect androgenic effects or for the presence of bioactive aromatic hydrocarbons. Gene expression profiling is emerging as a sensitive and specific method to screen complex samples for endocrine disrupting activity.

Androgens↗

PubMed2004

Pathway dependent isotopic fractionation during aerobic biodegradation of 1,2-dichloroethane.

1,2-Dichloroethane (1,2-OCA) is a widespread groundwater contaminant known to be biodegradable under aerobic conditions via enzymatic oxidation or hydrolytic dehalogenation reactions. Current literature reports that stable carbon isotope fractionation of 1,2-DCA during aerobic biodegradation is large and reproducible (-27 to -33/1000). In this study, a significant variation in the magnitude of stable carbon isotope fractionation during aerobic biodegradation was observed. Biodegradation in experiments involving microcosms, enrichment cultures, and pure microbial cultures produced a consistent bimodal distribution of enrichment factors (epsilon) with one mean epsilon centered on -3.9 +/- 0.6/1000 and the other on -29.2 +/- 1.9/1000. Reevaluation of epsilon in terms of kinetic isotope effects 12k/13k gave values of 12k/13k = 1.01 and 1.06, which are typical of oxidation and hydrolytic dehalogenation (S(N)2) reactions, respectively. The bimodal distribution is therefore consistent with the microbial degradation of 1,2-DCA by two separate enzymatic pathways. This interpretation is further supported in this study by experiments with pure strains of Xanthobacter autotrophicus GJ10, Ancylobacter aquaticus AD20, and Pseudomonas sp. Strain DCA1 for which the enzymatic degradation pathways are well-known. A small fractionation of -3.0/1000 was measured for 1,2-DCA degradation by Pseudomonas sp. Strain DCA1 (monooxygenase enzyme), while degradation by the hydrolytic dehalogenase enzyme by the other two pure strains was characterized by fractionation of -32.3/1000.

Biodegradation, Environmental↗

PubMed2004

Fluorotelomer alcohol biodegradation yields poly- and perfluorinated acids.

The widespread detection of environmentally persistent perfluorinated acids (PFCAs) such as perfluorooctanoic acid (PFOA) and its longer chained homologues (C9>C15) in biota has instigated a need to identify potential sources. It has recently been suggested that fluorinated telomer alcohols (FTOHs) are probable precursor compounds that may undergo transformation reactions in the environment leading to the formation of these potentially toxic and bioaccumulative PFCAs. This study examined the aerobic biodegradation of the 8:2 telomer alcohol (8:2 FTOH, CF3(CF2)7CH2CH2OH) using a mixed microbial system. The initial measured half-life of the 8:2 FTOH was approximately 0.2 days mg(-1) of initial biomass protein. The degradation of the telomer alcohol was monitored using a gas chromatograph equipped with an electron capture detector (GC/ECD). Volatile metabolites were identified using gas chromatography/ mass spectrometry (GC/MS), and nonvolatile metabolites were identified and quantified using liquid chromatography/ tandem mass spectrometry (LC/MS/MS). Telomer acids (CF3(CF2)7CH2COOH; CF3(CF2)6CFCHCOOH) and PFOA were identified as metabolites during the degradation, the unsaturated telomer acid being the predominant metabolite measured. The overall mechanism involves the oxidation of the 8:2 FTOH to the telomer acid via the transient telomer aldehyde. The telomer acid via a beta-oxidation mechanism was furthertransformed, leading to the unsaturated acid and ultimately producing the highly stable PFOA. Telomer alcohols were demonstrated to be potential sources of PFCAs as a consequence of biotic degradation. Biological transformation may be a major degradation pathway for fluorinated telomer alcohols in aquatic systems.

Bacteria, Aerobic↗

PubMed2004

Perchlorate-reducing microorganisms isolated from contaminated sites.

An extensive microcosm survey of perchlorate-contaminated sites was undertaken to assess the ability of indigenous microorganisms to degrade perchlorate. Samples from 12 contaminated sites and from one pristine location were analysed. Perchlorate was degraded to below detection limit in all electron donor-amended microcosms. Perchlorate-reducing microorganisms (PRMs) were numerous at most of these sites. Sixteen distinct PRMs were isolated that were phylogenetically related to either Dechloromonas in the Beta Proteobacteria (9/16 isolates) or to Azospirillum in the Alpha Proteobacteria (7/16 isolates). The majority of previously isolated PRMs are in the Beta Proteobacteria related to Dechloromonas or Dechlorosoma. This study indicates that PRMs of the genus Azospirillum may be more prevalent at contaminated sites than the current record of isolates suggests. Cell yields, electron donor to perchlorate ratios and maximum specific growth rates were similar among the isolates and similar to the few previously published values. However, the Monod half-saturation constants for perchlorate for the two Azospirillum isolates characterized were lower than those measured for other genera, suggesting that they may be more effective at low concentrations of perchlorate. These results extend the current understanding of PRMs from diverse environments and provide added confidence that microbial perchlorate reduction is ubiquitous, even at highly contaminated sites, and can be harnessed effectively for bioremediation.

Azospirillum↗

PubMed2004

Characterization of a highly enriched dehalococcoides-containing culture that grows on vinyl chloride and trichloroethene.

A highly enriched culture that reductively dechlorinates trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), and vinyl chloride (VC) to ethene without methanogenesis is described. The Dehalococcoides strain in this enrichment culture had a yield of (5.6 +/- 1.4) x 10(8) 16S rRNA gene copies/micromol of Cl(-) when grown on VC and hydrogen. Unlike the other VC-degrading cultures described in the literature, strains VS and BAV1, this culture maintained the ability to grow on TCE with a yield of (3.6 +/- 1.3) x 10(8) 16S rRNA gene copies/micromol of Cl(-). The yields on an electron-equivalent basis measured for the culture grown on TCE and on VC were not significantly different, indicating that both substrates supported growth equally well. PCR followed by denaturing gradient gel electrophoresis, cloning, and phylogenetic analyses revealed that this culture contained one Dehalococcoides 16S rRNA gene sequence, designated KB-1/VC, that was identical (over 1,386 bp) to the sequences of previously described organisms FL2 and CBDB1. A second Dehalococcoides sequence found in separate KB-1 enrichment cultures maintained on cDCE, TCE, and tetrachloroethene was no longer present in the VC-H(2) enrichment culture. This second Dehalococcoides sequence was identical to that of BAV1. As neither FL2 nor CBDB1 can dechlorinate VC to ethene in a growth-related fashion, it is clear that current 16S rRNA gene-based analyses do not provide sufficient information to distinguish between metabolically diverse members of the Dehalococcoides group.

Base Sequence↗

PubMed2003

Identification of estrogen-responsive genes by complementary deoxyribonucleic acid microarray and characterization of a novel early estrogen-induced gene: EEIG1.

Estrogen receptors (ERs) are nuclear transcription factors that regulate gene expression in response to estrogen and estrogen-like compounds. Identification of estrogen-regulated genes in target cells is an essential step toward understanding the molecular mechanisms of estrogen action. Using cDNA microarray examinations, 19 genes were identified as induced by 17 beta-estradiol in MCF-7 cells, 10 of which have been reported previously to be estrogen responsive or to be linked with ER status. Five known estrogen-regulated genes, E2IG4, IGFBP4, SLC2A1, XBP1 and B4GALT1, and AFG3L1, responded quickly to estrogen treatment. A novel estrogen-responsive gene was identified and named EEIG1for early estrogen-induced gene 1. EEIG1 was clearly induced by 17 beta-estradiol within 2 h of treatment, and was widely responsive to a group of estrogenic compounds including natural and synthetic estrogens and estrogenic environmental compounds. EEIG1 was expressed in ER-positive but not in ER-negative breast cancer cell lines. EEIG1 expression was repressed by antiestrogens 4-OH-tamoxifen and ICI 182,780 but not by protein synthesis inhibitors cycloheximide and puromycin. These results provide evidence that some estrogenic compounds differentially enhance the transcription of estrogen-regulated genes and suggest a role for EEIG1 in estrogen action.

Breast Neoplasms↗