[The construction and the expression of V5 epitope fused human androgen receptor vector in the yeast cell].

When we try to establish the gene recombinant yeast cell to screen the androgenic endocrine disruptors, the key procedure is the androgen receptor (AR) expression in the yeast cell. For this purpose, we obtained the GPD (glyceraldehyde-3-phosphote dehydrogenase) promoter from the yeast genosome of W303-1A using PCR system and inserting it into Swa I and BamH I sites of pYestrp2. The new constructed vector was named pGPD. The V5 epitope tag DNA with a 5'-BamH I and a 3'-EcoR I sticky end was cloned into the corresponding site of the pGPD vector to yield the vector of pGPDV5. The 2 723 bp full length AR ORF amplified by PCR from pcDNA3.1/AR was fused to V5 epitope tag DNA in pGPDV5 to give the AR yeast expression vector of pGPDV5/AR. This fused vector was transformed into the yeast cell (W303-1A). Western blot was used to detect the V5 fused protein of AR, in the protocol of which the primary monoclonal antibody (IgG(2a)) of mouse anti-V5 and the polyclonal secondary antibody of goat anti-mouse (IgG) linked to horseradish peroxidase (HRP) were used to detect the specific protein in the given sample of the transformed yeast extract. The result showed that the fused protein of AR was expressed successfully in the yeast cell.

[Establishment of recombinant Lac Z reporter gene-transformed yeast cells for bioassay of androgen-like compounds in environment].

OBJECTIVE: To establish the yeast-based bioassay system for the androgenic endocrine disruptors in the environment. METHODS: The recombinant gene-transformed yeast cells were constructed based on two episomal vectors. In the expression vector, the expression of androgen receptor (AR) gene was driven by 3-glyceraldehydephosphate dehydrogenase (GPD) promoter and the gene was fused to V5 epitope; in the reporter vector, the expression of the Lac Z gene as a report gene was under the control of the androgen response element (ARE). The vectors were transformed into yeast cells (W303-1A) to construct the yeast-based bioassay system. The sensitivity of this assay system was evaluated by the androgenic compounds (dihydrotestosterone, DHT and testosterone propionate, TP)and the specificity of this system by the estrogenic compounds (17ß-estradiol, estriol, estrone, diethylstilbestrol and ethinyl estradiol). RESULTS: Both DHT and TP yielded a significant dose-effect model with the recombinant gene-transformed yeast cells, indicating that this yeast bioassay system has a high sensitivity. Moreover, the assay also exhibited a high specificity in that the yeast cells had no dose-effect relationship with the different concentrations of five estrogens (17ß-estradiol, estriol, estrone, diethylstilbestrol and ethinyl estradiol). CONCLUSION: The recombinant yeast cells could be applied to screen for the androgen-like compounds in the environment.

[The effects of TATA-box in CYC1 promoter on the reporter gene regulated by ERE in the recombinant yeast cell].

The complementary oligonucleotides, each with two consensus estrogen response element (ERE)-sequences and 5'-Hind III and 3'-Sph I sticky ends were artificially synthesized. A solution with both the complementary DNA sequences was heated to 95'C and cooled down to room temperature to form double strand DNA (dsDNA). The set was cloned into the corresponding sites of CYC1 promoter of the pERE-CYC-yEGFP to yield pERE-CYCalpha-yEGFP vector. The two different reporter vectors, pERE-CYC-yEGFP and pERE-CYCalpha-yEGFP, the 2ERE, were placed in the CYC1 promoter. The former promoter downstream ERE contains alpha and beta-TATA boxes and the latter has only alpha-TATA box. The two different reporter vectors were transformed into the yeast cells that express human estrogen receptor alpha (ERalpha). Incubation of the recombinant yeasts with the six estrogenic compounds for 4 hours showed that the recombinant cell containing pERE-CYCalpha-yEGFP would give very poor dose-response curves, in contrast to the recombinant cell containing pERE-CYC-yEGFP which produced well-shaped dose-response curves. So it is necessary for this bioassay that alpha and beta-TATA boxes in the minimal CYC1 promoter when the promoter is used as a rapid and high throughput system for screening estrogenic chemical products.

Development of a rapid screening and surveillance for estrogenic chemicals in environment based on recombinant yEGFP yeast cell.

A recombinant yEGFP gene yeast strain necessary for the routine screening of estrogen activity in the chemical product of the environment was described. Two plasmids, one containing human estrogen receptor (hER) cDNA fused to the GPD gene promoter and another yEGFP inserted under the control of ERE, were constructed. The use of hER cDNA and the yEGFP reporter in the yeast cell sensor resulted in estrogenic chemical product-dependent light emission of yEGFP without additions owing its advantages: a simple and reagent-free measurement of GFP, and a non-toxic protein characteristic. The time needed for the optimal induction of light emission was 4h. The maximal fold induction of 8.80 over uninduced levels at the concentration of 10(-5)M of bisphenol A and 0.1 nM sensitivities for four different estrogenic chemicals tested were obtained. Five different chemicals which could not bind to hER did not cause an induction of yEGFP. This bioassay can be performed completely in 96-well plates. Thus, this test system can be used as a rapid screening system for the surveillance of estrogenic chemical products in the environment. The yEGFP assay is sensitive, reproducible, and cheap, which makes it highly suitable to be used as a high throughput system.

[Bioassay of recombinant green fluorescent protein gene yeast cell for a high throughput to screen estrogenic compounds].

We developed the recombinant green fluorescent protein gene yeast cell to screen estrogenic compounds based on two episomal vectors. In the expression vector the expression of human estrogen receptor alpha(hERalpha) was driven by 3-glyceraldehydephosphate dehydrogenase (GPD) promoter; in the reporter vector the expression of the yeast enhanced green fluorescent protein (yEGFP) gene was under the control of the estrogen response element (ERE). The vectors were transformed into yeast cell (W303-1A) to construct GFP recombinant yeast cell. Incubation of the yeast cell with various concentrations of the estrogenic compounds led to expression of the reporter gene product GFP in a dose dependent manner. Compared to other yeast bioassays, the yeast cell for environmental estrogen bioassay based on yEGFP reporter gene did not need cell wall disruption or the addition of a substrate or reagent. This yEGFP assay was performed completely in 96 well plates. So this test system can be used as a rapid and high throughput system for screening estrogenic chemical products, which has the characteristics of the sensitivity, reproducibility and cheapness.

Bioassay of estrogenic activity of effluent and influent in a farm wastewater treatment plant using an in vitro recombinant assay with yeast cells.

OBJECTIVE: Environmental estrogens at an elevated concentration are known to produce adverse effects on human and animal life. However, the majority of researches have been focused on industrial discharges, while the impact of livestock wastes as a source of endocrine disrupters in aquatic environments has been rarely elucidated. In order to investigate the contribution of environmental estrogens from livestock, the estrogenic activity in water samples from a farm wastewater treatment plant was analyzed by a recombinant yeast screening method. METHODS: The extracts prepared from 15 selected water samples from the farm wastewater treatment plant, among which 6 samples were from pre-treatment section (influents) and 9 from post-treatment section (effluents), were analyzed for estrogenic activity by cellar bioassay. Yeast cells transfected with the expression plasmid of human estrogen receptor and the Lac Z reporter plasmid encoding beta-galactossidase, were used to measure the estrogen-like compounds in the farm wastewater treatment plant. RESULTS: The wastewater samples from influents showed a higher estrogenic potency than the effluent samples showing a low induction of beta-galactossidase relative to solvent control condition. By comparison with a standard curve for 17 beta-estradiol (E2), estrogenic potency in water samples from the influents was calculated as E2-equivalent and ranged from 0.1 to 150 pM E2-equivalent. The estrogenic potency in water samples from the effluents was significantly lower than that in the influents, and 7 water samples had less detectable limit in the total of 9 samples. CONCLUSION: Yeast bioassay of estrogenic activity in most of the samples from the farm wastewater after disposal by traditional sewage treatment showed negative results.