Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Heterologous expression system”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1990

Cell cycle regulation of an exogenous human poly(ADP-ribose) polymerase cDNA introduced into murine cells.

We have evaluated the regulation of expression of the poly(ADP-ribose) polymerase gene during cell growth and replication. In a synchronized population of HeLa cells or in serum-stimulated WI-38 cells, steady-state levels of the polymerase mRNA were highest at late S and S-G2 phases and negligible in early S phase. Transcription did not solely account for the significant increase in the mRNA levels observed in late S phase by Northern analysis. The stability of the mRNA was dependent upon the percent proliferating cells in the culture. Accordingly, polymerase mRNA from cells in early exponential phase was significantly more stable than from cells in stationary phase of asynchronous growth. To clarify these observations, we utilized a novel heterologous expression system that involved murine 3T3 cells transfected with a human poly(ADP-ribose) polymerase cDNA under the control of a non-cell cycle-specific promoter. Cells were synchronized, and a comparison was made of the endogenous (murine) and exogenous (human) polymerase mRNA levels. Both the endogenous and the exogenous mRNA were specifically stabilized by the same mechanisms and only during late S phase; therefore, we concluded that mRNA pools for the polymerase are regulated at the post-transcriptional level. The heterologous expression system confirmed that the post-transcriptional regulation system in the mouse cells can recognize and faithfully regulate the human cDNA in response to the murine cell cycle signals. More importantly, the presence of extra copies (human) of the polymerase gene did not provide an increased amount of the total polymerase mRNA or protein and, in fact, the sum of the endogenous and exogenous mRNA in the transfected cells was approximately the same as the level of endogenous transcript in the control cells. This suggested that there might be a limit to the amount of polymerase protein accumulating in the cellular pool and thus levels of poly(ADP-ribose) polymerase may be autoregulated.

Animals↗
PubMed1992

Functional properties of acetylcholine receptors coexpressed with the 43K protein in heterologous cell systems.

The nicotinic acetylcholine (ACh) receptor is an integral membrane protein which mediates synaptic transmission at the skeletal neuromuscular junction. A key event in the development of the neuromuscular junction is the formation of high density aggregates of ACh receptors in the postsynaptic membrane. Receptor clustering has been attributed, in part, to their association with a peripheral membrane protein of Mr 43,000 (43K protein). We have addressed whether the association of the 43K protein can alter the single channel properties of the ACh receptor, and thus influence neuromuscular transmission at developing synapses, by expressing ACh receptors with and without the 43K protein in heterologous expression systems. We found that coexpression of the 43K protein with the receptor did not significantly alter either its single channel conductance or its mean channel open time. This was true in oocytes and also in COS cells where it was possible to localize 43K-induced clusters by fluorescence microscopy and to record from those clustered receptors. These data are in agreement with previous single channel studies which have shown that the properties of diffusely distributed and clustered receptors in native muscle cells from both mice and Xenopus do not differ.

Animals↗
PubMed1992

Immunocytochemical analysis reveals differences between the subcellular localization of normal and delta Phe508 recombinant cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis (CF) is caused by mutations in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR). The most common mutation responsible for CF is the deletion of amino acid residue Phe508, with an average allelic frequency of 70%. We have isolated an anti-CFTR monoclonal antibody which specifically recognizes recombinant normal and delta Phe508-CFTR produced by a vaccinia virus expression system. Immunocytochemical analysis of L cells expressing either normal or delta Phe508-CFTR showed a marked difference in subcellular distribution. Normal CFTR had a distinct localization in the perinuclear area and was also associated with the plasma membrane. delta Phe508-CFTR essentially lacked the membrane-associated distribution and was present throughout the cytoplasm. This heterologous expression system thus provides a model system for studying the subcellular localization of different mutant forms of CFTR.

Animals↗
PubMed1991

A Mycoplasma hyorhinis protein with sequence similarities to nucleotide-binding enzymes.

We have determined the nucleotide (nt) and deduced amino acid (aa) sequence of a unique 115-kDa Mycoplasma hyorhinis protein (P115) with an N-terminal region containing a highly conserved consensus sequence characteristics of nt-binding domains of several ATPase and GTPase enzymes. However, P115 lacked additional conserved features characteristic of some classes of nt-binding proteins. Based on the hydropathy profile of the deduced aa sequence, the absence of a leader peptide, its exclusive partitioning into the hydrophilic phase during Triton X-114 phase fractionation of M. hyorhinis, and immunofluorescence analysis indicating no surface-exposed domains, it was concluded that P115 is a cytoplasmic protein lacking intrinsic membrane interaction. M. hyorhinis P115 appears to be a species-specific protein, since it was not detected in any other mycoplasmal or bacterial species examined with specific antibody or genomic probes. Since genetic systems for direct mutational analysis are currently unavailable in this organism, sequence analysis provides critical information in establishing the possible function of this protein. Moreover, the nt sequence encoding P115 reported here supports a previously proposed model, based on synthesis of P115-related proteins in Escherichia coli, suggesting that multiple polypeptide products can be generated from mycoplasma genes by promiscuous translation initiation in this heterologous expression system.

Adenosine Triphosphatases↗
PubMed1991

Expression and enzymatic activity of recombinant cytochrome P450 17 alpha-hydroxylase in Escherichia coli.

When the cDNA encoding bovine microsomal 17 alpha-hydroxylase cytochrome P450 (P45017 alpha) containing modifications within the first seven codons which favor expression in Escherichia coli is placed in a highly regulated tac promoter expression plasmid, as much as 16 mg of spectrally detectable P45017 alpha per liter of culture can be synthesized and integrated into E. coli membranes. The known enzymatic activities of bovine P45017 alpha can be reconstituted by addition of purified rat liver NADPH-cytochrome P450 reductase to isolated E. coli membrane fractions containing the recombinant P45017 alpha enzyme. Surprisingly, it is found that E. coli contain an electron-transport system that can substitute for the mammalian microsomal NADPH-cytochrome P450 reductase in supporting both the 17 alpha-hydroxylase and 17,20-lyase activities of P45017 alpha. Thus, not only can E. coli express this eukaryotic membrane protein at relatively high levels, but as evidenced by metabolism of steroids added directly to the cells, the enzyme is catalytically active in vivo. These studies establish E. coli as an efficacious heterologous expression system for structure-function analysis of the cytochrome P450 system.

17-alpha-Hydroxypregnenolone↗
PubMed1992

Functional analysis of the promoter region of a nodule-enhanced glutamine synthetase gene from Phaseolus vulgaris L.

The 5'-flanking region of gln-gamma, the nodule-enhanced glutamine synthetase gene from Phaseolus vulgaris L., has been analysed for cis-regulatory elements using a series of 5' deletions and hybrid gln-gamma:: CaMV 35S promoters. The promoters were fused to the uidA reporter gene and their activities tested in two heterologous expression systems. In the first system, the chimaeric genes were transferred to Lotus corniculatus L. using Agrobacterium rhizogenes and their expression was studied in nodulated hairy roots. In the second system, the constructs were electroporated into tobacco mesophyll protoplasts. The results of the 5' deletion analysis showed that the sequence between -597 and -21 (relative to the ATG codon) was sufficient for nodule-specific expression of the chimaeric gene in nodulated hairy roots, and revealed the existence of at least two positive regulatory elements. Sequences located between -2000 and -597 were able to stimulate expression in nodules but not protoplasts, while the region from -597 to -354 enhanced expression in both nodules and protoplasts. Results obtained with the hybrid gln-gamma::35S promoters showed that two overlapping restriction fragments (-516/-343 and -474/-293) were able to stimulate expression from a heterologous promoter in an orientation-dependent manner. Previous work has demonstrated the presence of conserved A/T-rich binding sites for nuclear proteins in the region between -516 and -446, and their possible role in regulating gln-gamma expression is discussed.

DNA Mutational Analysis↗
PubMed1992

Mislocalization of delta F508 CFTR in cystic fibrosis sweat gland.

Misprocessing and mislocalization of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) has been described for the major CF-causing mutation (delta F508) in heterologous expression systems in vitro. We have generated monoclonal antibodies (mAbs) to CFTR with the aim of localizing the protein and its CF variants in vivo. Of the tissues where CFTR was observed, only the sweat gland is readily available and does not undergo secondary changes due to CF disease pathology. Sweat ducts from CF patients homozygous for delta F508 did not show the typical apical membrane staining seen in control biopsies. This demonstrates that the biosynthetic arrest and intracellular retention of delta F508 CFTR initially observed in vitro does occur in vivo and emphasizes the need to focus efforts on understanding the mislocalization.

Amino Acid Sequence↗
PubMed1992

Endothelial nitric oxide synthase: molecular cloning and characterization of a distinct constitutive enzyme isoform.

Nitric oxide (NO) is a ubiquitous intercellular messenger molecule synthesized from the amino acid L-arginine by NO synthases in diverse cells and tissues. NO is synthesized in vascular endothelial cells and appears to play an important role in the control of blood pressure and platelet aggregation. A detailed understanding of the regulation of NO synthesis by endothelial cells has been hampered by the lack of molecular clones for endothelial NO synthase; the isolation and characterization of such clones is reported herein. The constitutive NO synthases present in endothelial cells and in brain share common biochemical and pharmacologic features. We purified NO synthase from bovine brain and determined the amino acid sequence of several tryptic peptides. The sequence of the bovine brain peptides is nearly identical to the deduced amino acid sequence previously determined for the rat brain NO synthase. These sequence data were utilized to design PCR-generated NO synthase cDNA probes, which were used to isolate clones encoding NO synthase from a bovine aortic endothelial cell (BAEC) cDNA library. A full-length NO synthase cDNA clone was isolated, representing a protein of 1205 amino acids with a molecular mass of 133 kDa; transfection of this clone in a heterologous expression system demonstrated the expected enzymatic activity. The deduced amino acid sequence of the BAEC NO synthase cDNA differs at numerous residues from the sequence determined for the purified bovine brain protein and shows 50-60% sequence identity with recently isolated molecular clones for murine macrophage and rat brain NO synthase isoforms. Bovine genomic Southern blots probed with bovine brain and BAEC NO synthase cDNA probes identify distinct bands, indicating that these cDNAs are the products of different genes. Prolonged treatment of BAECs with the cytokine tumor necrosis factor alpha, which we have previously shown to result in a marked increase in NO synthase activity, is associated with a decrease in the abundance of the 4.8-kilobase BAEC NO synthase transcript. The increase in BAEC NO synthase activity induced by tumor necrosis factor alpha is thus likely to involve posttranscriptional mechanisms or the induction of a distinct endothelial NO synthase isoform.

Amino Acid Oxidoreductases↗
PubMed1990

Monoclonal antibodies specific to human ETS-2 oncoprotein: recognition of epitopes clustered on the B domain.

Six monoclonal antibodies were prepared from mice immunized with a bacterially expressed human ets-2 protein. These antibodies specifically recognize the two human ets-2-encoded proteins p56 and p54 but failed to react with chicken, mouse, rat, bovine, or monkey proteins, suggesting that the antibodies recognize epitopes specific to the human ets-2 protein. Differential reactivities of these monoclonal antibodies with the peptide fragments generated by partial proteolytic digestion of the bacterially expressed ets-2 protein indicated that the six antibodies recognize at least three distinct epitopes in the B domain of the ets-2 protein. Immunoprecipitation experiments comparing native and denaturing conditions suggested that the ets-2 domain detected by the monoclonal antibodies is masked in the native condition by either protein folding or interacting proteins. The biochemical analysis of the ets-2 protein will be facilitated by the development of these monoclonal antibodies, which may be useful as both domain-specific probes and tools for specifically detecting the human ets-2 protein in heterologous expression systems.

Animals↗
PubMed1992

Isolation and characterization of a gene encoding DNA topoisomerase I in Drosophila melanogaster.

We synthesized a DNA probe specific for the gene encoding eucaryotic DNA topoisomerase I by the polymerase chain reaction. The sequences of the primers for this reaction were deduced from the regions with extensive homology among the enzymes from the fission and budding yeasts, and the human. From the clones isolated by screening a Drosophila cDNA library with this DNA probe, two cDNA clones of 3.8 and 5.2 kb were characterized and completely sequenced. Both cDNA sequences contain an identical open reading frame for 972 amino acid residues. The 3.8 kb messenger RNA is likely generated by using a polyadenylation site 5' upstream to that used in generating the 5.2 kb mRNA. The predicted amino acid sequence shows that a segment of 420 amino acid residues at the amino terminus is hydrophilic, similar to the amino terminal 200 residues in the yeast and human enzymes. Furthermore, the Drosophila enzyme is unique in that the amino terminal 200 residues are enriched in serine and histidine residues; most of them are present in clusters. The rest of the Drosophila sequence is highly homologous to those from yeast and human enzymes. The evolutionarily conserved residues are identified and are likely the critical elements for the structure and function of this enzyme. A plasmid vector containing the cloned cDNA was constructed for the expression of Drosophila protein in Escherichia coli. The enzymatic and immunochemical analysis of the polypeptide produced in this heterologous expression system demonstrated that the expressed protein shares similar enzymatic properties and antigenic epitopes with DNA topoisomerase I purified from Drosophila embryos or tissue culture cells, thus establishing the bacterial expression system being useful for the future structure/function analysis of the Drosophila enzyme.

Amino Acid Sequence↗
PubMed1992

Expression of an outward-rectifying potassium channel from maize mRNA and complementary RNA in Xenopus oocytes.

Injection of Xenopus oocytes with poly(A)+ mRNA isolated from different plants (maize, cucumber, and squash) results in the appearance of a voltage- and time-dependent, potassium-selective, outward current that is similar to the outward-rectifying potassium current recorded in many higher plant cells. Maize shoots were found to be especially enriched in mRNA encoding such activity. A cDNA library of maize shoot mRNA was constructed in the vector lambda ZAPII and was used to synthesize RNA complementary to the cDNA (cRNA). Injection of the cRNA gave rise to an outward-rectifying potassium current with properties similar to the currents obtained by poly(A)+ mRNA injection. These results demonstrate that higher plant mRNA can be properly translated into a product that produces a voltage-regulated potassium channel in the plasma membrane of Xenopus oocytes. Thus, Xenopus oocytes can be used as a heterologous expression system for the functional identification and isolation of plant ion channel genes as well as for the study of structure-function relationship of plant ion channels.

Animals↗
PubMed1991

Rescue of Sindbis virus-specific RNA replication and transcription by using a vaccinia virus recombinant.

A heterologous system expressing functional Sindbis virus nonstructural proteins (nsPs) has several possible uses for studying Sindbis virus-specific RNA replication and transcription in vivo and in vitro. Of the many possible approaches, vaccinia virus offers an attractive transient expression system given that Sindbis virus replication can occur in cells which have been previously infected by vaccinia virus. In this report, a vaccinia virus recombinant (called vSINNS), which contains the cDNA encoding the Sindbis virus nsPs under the control of either the vaccinia virus 7.5K promoter or the bacteriophage T7 promoter, has been constructed and characterized. Upon infection of several cell types with vSINNS, Sindbis virus nsP precursors and processed forms, including nsP1, nsP2, and both phosphorylated and nonphosphorylated forms of nsP3, were synthesized. Proteins containing the putative RNA-dependent RNA polymerase domain (nsP4 and nsP34), which are normally produced in small amounts by readthrough of an opal termination codon, were not detected in vSINNS-infected cells. However, all nsP functions necessary for Sindbis virus-specific RNA synthesis must have been expressed, since both replication and subgenomic mRNA transcription of an engineered Sindbis virus defective interfering RNA in cells infected with vSINNS was observed. Furthermore, vSINNS could be used as a helper virus to amplify, to relatively high titers, a replication-defective Sindbis virus mutant containing an in-frame deletion in the conserved N-terminal domain of nsP3. These data, as well as the observation that normal yields of parental Sindbis virus are produced in cells which have been previously infected with vSINNS, indicate that expression of Sindbis virus nsPs, in the absence of Sindbis virus-specific RNA replication, is not sufficient to block the formation of active RNA replication complexes by superinfecting Sindbis virus.

Animals↗
PubMed1992

The arginine-rich domain of the hepatitis B virus core protein is required for pregenome encapsidation and productive viral positive-strand DNA synthesis but not for virus assembly.

Assembly of replication-competent hepatitis B virus (HBV) nucleocapsids requires the interaction of the core protein, the P protein, and the RNA pregenome. The core protein contains an arginine-rich C-terminal domain which is dispensable for particle formation in heterologous expression systems. Using transient expression in HuH7 cells of a series of C-terminally truncated core proteins, I examined the functional role of this basic region in the context of a complete HBV genome. All variants containing at least the 144 N-terminal amino acids were assembly competent, but efficient pregenome encapsidation was observed only with variants consisting of 164 or more amino acids. These data indicate that one function of the arginine-rich region is to provide the interactions between core protein and RNA pregenome. However, in cores from the variant ending with amino acid 164, the production of complete positive-strand DNA was drastically reduced. Moreover, almost all positive-strand DNA originated from in situ priming, whereas in wild-type particles, this type of priming not supporting the formation of relaxed circular DNA (RC-DNA) accounted for about one half of the positive strands. Further C-terminal residues to position 173 restored RC-DNA formation, and the corresponding variant did not differ from the full-length core protein in all assays used. The observation that RNA encapsidation and formation of RC-DNA can be genetically separated suggests that the core protein, via its basic C-terminal region, also acts as an essential auxiliary component in HBV replication, possibly like a histone, or like a single-stranded-DNA-binding protein. In contrast to their importance for HBV replication, sequences beyond amino acid 164 were not required for the formation of enveloped virions. Since particles from variant 164 did not contain mature DNA genomes, a genome maturation signal is apparently not required for HBV nucleocapsid envelopment.

Amino Acid Sequence↗
PubMed2025

FGF13 is not secreted from mouse neurons.

FGF13, a noncanonical fibroblast growth factor (FGF) and member of the fibroblast growth factor homologous factor (FHF) subset, lacks a signal sequence and was previously reported to remain intracellular, where it regulates voltage-gated sodium channels (VGSCs) at least in part through direct interaction with the cytoplasmic C-terminus of VGSCs. Recent reports suggest FGF13 is secreted and regulates neuronal VGSCs through interactions with extracellular domains of integral plasma membrane proteins, yet supportive data are limited. Using rigorous positive and negative controls, we show that transfected FGF13 is not secreted from cultured cells in a heterologous expression system, nor is endogenous FGF13 secreted from cultured neurons. Furthermore, using multiple unbiased screens including proximity labeling proteomics, our results suggest FGF13 remains within membranes and is unavailable to interact directly with extracellular protein domains.

Animals↗
PubMed2025

Archaea produce peptidoglycan hydrolases that kill bacteria.

The social life of archaea is poorly understood. In particular, even though competition and conflict are common themes in microbial communities, there is scant evidence documenting antagonistic interactions between archaea and their abundant prokaryotic brethren: bacteria. Do archaea specifically target bacteria for destruction? If so, what molecular weaponry do they use? Here, we present an approach to infer antagonistic interactions between archaea and bacteria from genome sequence. We show that a large and diverse set of archaea encode peptidoglycan hydrolases, enzymes that recognize and cleave a structure-peptidoglycan-that is a ubiquitous component of bacterial cell walls but absent from archaea. We predict the bacterial targets of archaeal peptidoglycan hydrolases using a structural homology approach and demonstrate that the predicted target bacteria tend to inhabit a similar niche to the archaeal producer, indicative of ecologically relevant interactions. Using a heterologous expression system, we demonstrate that two peptidoglycan hydrolases from the halophilic archaeaon Halogranum salarium B-1 kill the halophilic bacterium Halalkalibacterium halodurans, a predicted target, and do so in a manner consistent with peptidoglycan hydrolase activity. Our results suggest that, even though the tools and rules of engagement remain largely unknown, archaeal-bacterial conflicts are likely common, and we present a roadmap for the discovery of additional antagonistic interactions between these two domains of life. Our work has implications for understanding mixed microbial communities that include archaea and suggests that archaea might represent a large untapped reservoir of novel antibacterials.

N-Acetylmuramoyl-L-alanine Amidase↗
PubMed2025

RNG2 tethers the conoid to the apical polar ring in Toxoplasma gondii to enable parasite motility and invasion.

The conoid is a dynamic, tubulin-based structure conserved across the Apicomplexa that undergoes extrusion during egress, gliding motility, and invasion in Toxoplasma gondii. This organelle traverses the apical polar ring (APR) in response to calcium waves and plays a critical role in controlling parasite motility. While the actomyosin-dependent extrusion of the conoid is beginning to be elucidated, the mechanism by which it remains apically anchored to the APR is still unclear. RNG2, a protein localized to both the conoid and the APR, has emerged as a strong candidate for mediating this connection. Biochemical analysis revealed that RNG2 is an unstable protein, undergoing extensive proteolytic cleavage both in the parasite and in heterologous expression systems. Its biochemical properties, with the presence of large coiled-coil domains, likely facilitate the formation of concatenated assemblies, enabling RNG2 to serve as a dynamic and resilient bridge between the conoid and the APR. Using a combination of iterative ultrastructure expansion microscopy and immunoelectron microscopy, we confirmed the localization of RNG2 to the 22 tethering elements bridging the APR and the conoid. Conditional depletion of RNG2 led to the striking detachment of the intact conoid organelle from the APR, supporting an essential role for RNG2 as a tether. Cryo-electron tomography of conoid-less parasites revealed that, in the absence of RNG2, the apical vesicle remains anchored to the plasma membrane, while the rhoptries follow the detached conoid. Although RNG2 depletion only mildly reduces microneme secretion, the parasites are immotile and exhibit impaired rhoptry discharge, highlighting the critical role of proper conoid anchorage in motility and host cell invasion. Comprehensive mutagenesis of RNG2 identified distinct regions responsible for binding to the conoid and the APR, and demonstrated that the full-length, intact protein is essential for bridging these two structures and for its functional activity. Altogether, RNG2 emerges as a pivotal protein that ensures conoid functionality and coordination in Coccidia.

Toxoplasma↗
PubMed1992

Differential activation of intracellular effector by two isoforms of human neurokinin-1 receptor.

Two isoforms of the human neurokinin-1 receptor were cloned and characterized in heterologous expression systems of mammalian cell culture and Xenopus oocytes. The two isoforms differ only in the length of the encoded polypeptide. The peptide-binding properties of the long form of human neurokinin-1 receptor are consistent with those of the native neurokinin-1 receptor of mammalian tissues, where substance P is the most potent agonist. Peptide agonists elicit an oscillating current in Xenopus oocytes expressing the long form. In contrast, the short form of human neurokinin-1 receptor expressed in COS cells binds substance P with an apparent affinity at least 10-fold lower than that of the long form, and it elicits the electrophysiological response only weakly in Xenopus oocytes. These data suggest that the short form couples to a different effector system. Sequence analysis suggested that the two isoforms may arise from alternative pre-mRNA splicing. These results indicate that multiple forms of the human neurokinin-1 receptor exist and the differential activation of intracellular effector may be involved in generating the complex biological effects of substance P.

Amino Acid Sequence↗
PubMed1992

Thyroid hormone regulates the oxytocin gene.

Endocrine factors involved in the transcriptional regulation of the oxytocin (OT) gene were investigated in heterologous expression systems. Plasmids having a 5'-flanking region of the rat OT gene (-363/+16) or the human OT gene (-382/+41) cloned in front of the firefly luciferase gene were co-transfected with an expression vector for the rat thyroid hormone receptor alpha in P19 embryonal carcinoma (EC) cells. Thyroid hormone (T3) stimulated the activity of the rat and human OT promoters about 10-fold. In MCF-7 breast tumor cells transfected with the human OT promoter-luciferase fusion gene, T3 stimulation through endogenous thyroid hormone receptors was about 5-fold. Co-transfection experiments in P19EC cells using 5' deletion mutants of the rat OT gene showed that thyroid hormone responsiveness was located in two regions, one located between nucleotides -195 and -172, the other between nucleotides -172 and -148. Each region accounted for about 3-fold T3 stimulation. Gel retardation analysis using extracts from HeLa cells over-producing the c-erbA/TR alpha protein showed specific binding to the -172/-148 element, while no binding occurred on the -195/-172 element. The -172/-148 element which contains the imperfect estrogen response element, GGTGACCTTGACC, has inverted as well as direct repeats of the TGACC motif. Mutagenesis of TGACC motifs separately reduced thyroid hormone responsiveness by about 50%. However, simultaneous mutation of two TGACC motifs abolished the responsiveness to T3 completely. There was no cooperativity between the activated thyroid hormone and estrogen receptors in transfected MCF-7 cells nor in thyroid hormone receptor and estrogen receptor co-transfected P19EC cells. Negative interactions between these two receptors were observed and gel retardation assays showed interaction between the two receptors proteins. It was shown in an in vivo experiment that treatment of rats with thyroid hormone increased hypothalamic OT mRNA levels, the pituitary OT content, as well as OT levels in blood. The results reveal thyroid hormone as a physiological regulator of OT gene expression, which stimulates OT promoter activity directly through interaction with a thyroid hormone-response element in the OT gene.

Animals↗