-
Nature Oct 2009Growing evidence supports the notion that proteasome-mediated destruction of transcriptional activators can be intimately coupled to their function. Recently, Nalley et...
Growing evidence supports the notion that proteasome-mediated destruction of transcriptional activators can be intimately coupled to their function. Recently, Nalley et al. challenged this view by reporting that the prototypical yeast activator Gal4 does not dynamically associate with chromatin, but rather 'locks in' to stable promoter complexes that are resistant to competition. Here we present evidence that the assay used to reach this conclusion is unsuitable, and that promoter-bound, active Gal4 is indeed susceptible to competition in vivo. Our data challenge the key evidence that Nalley et al. used to reach their conclusion, and indicate that Gal4 functions in vivo within the context of dynamic promoter complexes.
Topics: Binding, Competitive; Chromatin Immunoprecipitation; DNA-Binding Proteins; Estradiol; Galactokinase; Promoter Regions, Genetic; Protein Binding; Receptors, Estrogen; Reproducibility of Results; Research Design; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Tamoxifen; Trans-Activators; Transcription Factors; Transcription, Genetic; Transcriptional Activation
PubMed: 19812621
DOI: 10.1038/nature08406 -
Methods in Molecular Biology (Clifton,... 2014We have reviewed the binding affinities of several antitumor drugs doxorubicin (Dox), N-(trifluoroacetyl) doxorubicin (FDox), tamoxifen (Tam), 4-hydroxytamoxifen...
We have reviewed the binding affinities of several antitumor drugs doxorubicin (Dox), N-(trifluoroacetyl) doxorubicin (FDox), tamoxifen (Tam), 4-hydroxytamoxifen (4-Hydroxytam), and endoxifen (Endox) with chitosan nanoparticles of different sizes (chitosan-15, chitosan-100, and chitosan-200 KD) in order to evaluate the efficacy of chitosan nanocarriers in drug delivery systems. Spectroscopic and molecular modeling studies showed the binding sites and the stability of drug-polymer complexes. Drug-chitosan complexation occurred via hydrophobic and hydrophilic contacts as well as H-bonding network. Chitosan-100 KD was the more effective drug carrier than the chitosan-15 and chitosan-200 KD.
Topics: Antineoplastic Agents; Binding Sites; Chitosan; Doxorubicin; Drug Carriers; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Kinetics; Nanoparticles; Porosity; Tamoxifen; Thermodynamics
PubMed: 24567139
DOI: 10.1007/978-1-4939-0363-4_11 -
Hippocampus Jun 2016Recent studies have focused on the identification and manipulation of memory traces in rodent models. The two main mouse models utilized are either a CreER(T2) /loxP...
Recent studies have focused on the identification and manipulation of memory traces in rodent models. The two main mouse models utilized are either a CreER(T2) /loxP tamoxifen (TAM)- or a tetracycline transactivator/tetracycline-response element doxycycline-inducible system. These systems, however, could be improved to label a more specific population of activated neurons corresponding to behavior. Here, we sought to identify an improved selective estrogen receptor (ER) modulator (SERM) in which we could label an individual memory trace in ArcCreER(T2) mice. We found that 4-hydroxytamoxifen (4-OHT) is a selective SERM in the ArcCreER(T2) × Rosa26-CAG-stop(flox) -channelrhodospin (ChR2)-enhanced yellow fluorescent protein (eYFP) mice. The half-life of 4-OHT is shorter than TAM, allowing for more specificity of memory trace labeling. Furthermore, 4-OHT allowed for context-specific labeling in the dentate gyrus and CA3. In summary, we believe that 4-OHT improves the specificity of memory trace labeling and will allow for refined memory trace studies in the future. © 2015 Wiley Periodicals, Inc.
Topics: Animals; Bacterial Proteins; Cell Count; Channelrhodopsins; Conditioning, Psychological; Estradiol; Fear; Fulvestrant; Hippocampus; Immunohistochemistry; Luminescent Proteins; Memory; Mice, Transgenic; Microscopy, Confocal; Models, Animal; Neurons; RNA, Untranslated; Raloxifene Hydrochloride; Receptors, Estrogen; Selective Estrogen Receptor Modulators; Tamoxifen
PubMed: 26662713
DOI: 10.1002/hipo.22556 -
Biophysical Chemistry Nov 2021The anticancer drug tamoxifen and its primary metabolite 4-hydroxytamoxifen tend to accumulate in membranes due to its strong hydrophobic character. Thus, in this work...
The anticancer drug tamoxifen and its primary metabolite 4-hydroxytamoxifen tend to accumulate in membranes due to its strong hydrophobic character. Thus, in this work we have carried out a systematic study to investigate their effects on model phosphatidylcholine membranes. Tamoxifen and 4-hydroxytamoxifen affect the phase behaviour of phosphatidylcholine model membranes, giving rise to formation of drug/dipalmitoylphosphatidylcholine domains, which is more evident in the case of 4-hydroxytamoxifen. These drugs have differential effects on the polar and apolar regions of the phospholipid supporting a different location of both compounds within the bilayer. Both compounds induce contents leakage in fluid phosphatidylcholine unilamellar liposomes, the effect of 4-hydroxytamoxifen being negligible as compared to that of tamoxifen. Molecular dynamics confirmed the tendency of both drugs to form clusters, tamoxifen locating all along the bilayer, whereas 4-hydroxytamoxifen mostly locates near the lipid/water interface, which can explain the different effects of both drugs in fluid phosphatidylcholine membranes.
Topics: Phosphatidylcholines; Tamoxifen
PubMed: 34530285
DOI: 10.1016/j.bpc.2021.106681 -
Nature Chemical Biology May 2015Directly modulating the activity of genome-editing proteins has the potential to increase their specificity by reducing activity following target locus modification. We...
Directly modulating the activity of genome-editing proteins has the potential to increase their specificity by reducing activity following target locus modification. We developed Cas9 nucleases that are activated by the presence of a cell-permeable small molecule by inserting an evolved 4-hydroxytamoxifen-responsive intein at specific positions in Cas9. In human cells, conditionally active Cas9s modify target genomic sites with up to 25-fold higher specificity than wild-type Cas9.
Topics: Bacterial Proteins; Cells, Cultured; Endonucleases; Genome; HEK293 Cells; High-Throughput Nucleotide Sequencing; Humans; Ligands; Models, Molecular; Protein Conformation; Small Molecule Libraries; Tamoxifen
PubMed: 25848930
DOI: 10.1038/nchembio.1793 -
The EMBO Journal Sep 2011Autophagy is an evolutionarily conserved mechanism of cellular self-digestion in which proteins and organelles are degraded through delivery to lysosomes. Defects in...
Autophagy is an evolutionarily conserved mechanism of cellular self-digestion in which proteins and organelles are degraded through delivery to lysosomes. Defects in this process are implicated in numerous human diseases including cancer. To further elucidate regulatory mechanisms of autophagy, we performed a functional screen in search of microRNAs (miRNAs), which regulate the autophagic flux in breast cancer cells. In this study, we identified the tumour suppressive miRNA, miR-101, as a potent inhibitor of basal, etoposide- and rapamycin-induced autophagy. Through transcriptome profiling, we identified three novel miR-101 targets, STMN1, RAB5A and ATG4D. siRNA-mediated depletion of these genes phenocopied the effect of miR-101 overexpression, demonstrating their importance in autophagy regulation. Importantly, overexpression of STMN1 could partially rescue cells from miR-101-mediated inhibition of autophagy, indicating a functional importance for this target. Finally, we show that miR-101-mediated inhibition of autophagy can sensitize breast cancer cells to 4-hydroxytamoxifen (4-OHT)-mediated cell death. Collectively, these data establish a novel link between two highly important and rapidly growing research fields and present a new role for miR-101 as a key regulator of autophagy.
Topics: Autophagy; Autophagy-Related Proteins; Breast Neoplasms; Cell Line, Tumor; Cysteine Endopeptidases; Etoposide; Female; Gene Expression Profiling; Gene Expression Regulation; Humans; MicroRNAs; Oligonucleotide Array Sequence Analysis; RNA Interference; RNA, Small Interfering; Sirolimus; Stathmin; Tamoxifen; rab5 GTP-Binding Proteins
PubMed: 21915098
DOI: 10.1038/emboj.2011.331 -
Environmental Science & Technology Oct 2023Wastewater treatment plants (WWTPs) are regarded as the main sources of estrogens that reach the aquatic environment. Hence, continuous monitoring of potential...
Wastewater treatment plants (WWTPs) are regarded as the main sources of estrogens that reach the aquatic environment. Hence, continuous monitoring of potential estrogenic-active compounds by a biosensor is an appealing approach. However, existing biosensors cannot simultaneously distinguish and quantify estrogenic agonists and antagonists. To overcome the challenge, we developed an estrogen receptor-based biosensor that selectively screened estrogenic agonists and antagonists by introducing rationally designed agonist/antagonist conformation-specific reporters. The double functional conformation-specific reporters consist of a Cy5.5-labeled streptavidin moiety and a peptide moiety, serving as signal recognition and signal transduction elements. In addition, the conformation recognition mechanism was further validated at the molecular level through molecular docking. Based on the two-step "turn-off" strategy, the biosensor exhibited remarkable sensitivity, detecting 17β-estradiol-binding activity equivalent (E-BAE) at 7 ng/L and 4-hydroxytamoxifen-binding activity equivalent (4-OHT-BAE) at 91 ng/L. To validate its practicality, the biosensor was employed in a case study involving wastewater samples from two full-scale WWTPs across different treatment stages to map their estrogenic agonist and antagonist binding activities. Comparison with the yeast two-hybrid bioassay showed a strong liner relationship ( = 0.991, < 0.0001), indicating the excellent accuracy and reliability of this technology in real applications.
Topics: Wastewater; Molecular Docking Simulation; Reproducibility of Results; Estrogens; Estrone; Biosensing Techniques; Water Pollutants, Chemical
PubMed: 37802504
DOI: 10.1021/acs.est.3c03223 -
Biomedicine & Pharmacotherapy =... Jan 2022Tamoxifen, a widely prescribed medication in premenopausal women diagnosed with hormone-dependent breast cancer, is potentially co-prescribed with Hedyotis diffusa (H....
Tamoxifen, a widely prescribed medication in premenopausal women diagnosed with hormone-dependent breast cancer, is potentially co-prescribed with Hedyotis diffusa (H. diffusa), particularly in Taiwan. However, no related report has investigated the drug-herb interaction of H. diffusa on the pharmacokinetics of tamoxifen and its metabolites. In the present study, male Sprague-Dawley rats were administered different doses of H. diffusa extract for 5 consecutive days prior to the administration of tamoxifen (10 mg/kg). A validated ultra-liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) system was developed to monitor tamoxifen, 4-hydroxytamoxifen, N-desmethyltamoxifen, and endoxifen in rat plasma. Pharmacokinetic results demonstrated that the area under curves (AUCs) of tamoxifen and the relative bioavailability (%) of tamoxifen were dose-dependently decreased (31-68%) by pre-treatment with H. diffusa extract (3 g/kg and 6 g/kg). In addition, the conversion ratio of 4-hydroxytamoxifen was downregulated (0.5-fold change) and the N-desmethyltamoxifen conversion ratio was upregulated (2-fold change) by high-dose H. diffusa extract. As a result, the relative bioavailability and biotransformation changes affect the clinical efficacy of tamoxifen treatment. These preclinical findings reveal a hitherto unreported interaction between tamoxifen and H. diffusa extract that has implications for their therapeutic efficacy in treating breast cancer.
Topics: Animals; Biological Availability; Biotransformation; Breast Neoplasms; Chromatography, Liquid; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Hedyotis; Herb-Drug Interactions; Plant Extracts; Rats; Rats, Sprague-Dawley; Tamoxifen; Tandem Mass Spectrometry
PubMed: 34839255
DOI: 10.1016/j.biopha.2021.112466 -
Nutrition and Cancer 2001Anthocyanins, which are natural plant pigments from the flavonoid family, represent substantial constituents of the human diet. Because some other bioflavonoids are... (Comparative Study)
Comparative Study
Anthocyanins, which are natural plant pigments from the flavonoid family, represent substantial constituents of the human diet. Because some other bioflavonoids are known to have estrogenic activity, the aim of this study was to determine the estrogenic activity of the anthocyanine aglycones. Binding affinity to the estrogen receptor-alpha was 10,000- to 20,000-fold lower than that of the endogenous estrogen estradiol. In the estrogen receptor-positive cell line MCF-7, the anthocyanidins induced expression of a reporter gene. The tested anthocyanidins showed estrogen-inducible cell proliferation in two cell lines (MCF-7 and BG-1), but not in the receptor-negative human breast cancer cell line MDA-MB-231. The phytoestrogen-induced cell proliferation could be blocked by addition of the receptor antagonist 4-hydroxytamoxifen. Combination treatments with the endogenous estrogen estradiol resulted in a reduction of estradiol-induced cell proliferation. Overall, the tested anthocyanidins exert estrogenic activity, which might play a role in altering the development of hormone-dependent adverse effects.
Topics: Anthocyanins; Breast Neoplasms; Cell Division; Estradiol; Estrogen Receptor alpha; Estrogens; Estrogens, Non-Steroidal; Female; Gene Expression; Humans; Isoflavones; Ovarian Neoplasms; Phytoestrogens; Plant Preparations; Receptors, Estrogen; Tamoxifen; Transcription, Genetic; Tumor Cells, Cultured
PubMed: 12094617
DOI: 10.1080/01635581.2001.9680625 -
The Journal of Steroid Biochemistry and... May 1993Some of the isoflavonoids present in human diet as well as in urine are expected to exert biologic effects as they have been reported to bind to estrogen receptors and...
Some of the isoflavonoids present in human diet as well as in urine are expected to exert biologic effects as they have been reported to bind to estrogen receptors and to be estrogenic in other species. This report describes the in vitro assessment of estrogenic effects of isoflavonoids using human endometrial cells and tissue. The relative estrogenic potencies (EC50 values) of estradiol, 3 dietary isoflavonoids (coumestrol, genistein and daidzein) and one of their metabolites (equol), were estimated by using a recently developed multiwell plate in vitro bioassay based on the estrogen-specific enhancement of alkaline phosphatase (AlkP) activity in human endometrial adenocarcinoma cells of the Ishikawa-Var I line. The maximal AlkP activity elicited by the isoflavonoids tested was as high as that achieved with estradiol and their effects were suppressed by the antiestrogens 4-hydroxytamoxifen and ICI 164,384. These results indicate that estradiol and the isoflavonoids exert their effects on AlkP by similar interactions with the estrogen receptor, with potencies depending on binding affinities. The estrogenic effect of equol was confirmed by another in vitro bioassay, based on the estrogen-stimulated enhancement of prostaglandin F2 alpha output by fragments of human secretory endometrium.
Topics: Adenocarcinoma; Alkaline Phosphatase; Biological Assay; Chromans; Coumestrol; Dinoprost; Endometrial Neoplasms; Endometrium; Equol; Estradiol; Female; Genistein; Humans; Isoflavones; Polyunsaturated Alkamides; Tamoxifen; Tumor Cells, Cultured
PubMed: 8499347
DOI: 10.1016/0960-0760(93)90009-l