Regulation Of Hormone Gene Expression Research Articles

Expression of hormone-regulated genes in osteoblastic cells with reference to postmenopausal osteoporosis

Expression of hormone-regulated genes in osteoblastic cells with reference to postmenopausal osteoporosis

Thyroid hormone regulation of hepatic genes in vivo detected by complementary DNA microarray.

The liver is an important target organ of thyroid hormone. However, only a limited number of hepatic target genes have been identified, and little is known about the pattern of their regulation by thyroid hormone. We used a quantitative fluorescent cDNA microarray to identify novel hepatic genes regulated by thyroid hormone. Fluorescent-labeled cDNA prepared from hepatic RNA of T3-treated and hypothyroid mice was hybridized to a cDNA microarray, representing 2225 different mouse genes, followed by computer analysis to compare relative changes in gene expression. Fifty five genes, 45 not previously known to be thyroid hormone-responsive genes, were found to be regulated by thyroid hormone. Among them, 14 were positively regulated by thyroid hormone, and unexpectedly, 41 were negatively regulated. The expression of 8 of these genes was confirmed by Northern blot analyses. Thyroid hormone affected gene expression for a diverse range of cellular pathways and functions, including gluconeogenesis, lipogenesis, insulin signaling, adenylate cyclase signaling, cell proliferation, and apoptosis. This is the first application of the microarray technique to study hormonal regulation of gene expression in vivo and should prove to be a powerful tool for future studies of hormone and drug action.

Thyroid Hormone Regulation of Hepatic Genes in Vivo Detected by Complementary DNA Microarray

The liver is an important target organ of thyroid hormone. However, only a limited number of hepatic target genes have been identified, and little is known about the pattern of their regulation by thyroid hormone. We used a quantitative fluorescent cDNA microarray to identify novel hepatic genes regulated by thyroid hormone. Fluorescent-labeled cDNA prepared from hepatic RNA of T3-treated and hypothyroid mice was hybridized to a cDNA microarray, representing 2225 different mouse genes, followed by computer analysis to compare relative changes in gene expression. Fifty five genes, 45 not previously known to be thyroid hormone-responsive genes, were found to be regulated by thyroid hormone. Among them, 14 were positively regulated by thyroid hormone, and unexpectedly, 41 were negatively regulated. The expression of 8 of these genes was confirmed by Northern blot analyses. Thyroid hormone affected gene expression for a diverse range of cellular pathways and functions, including gluconeogenesis, lipogenesis, insulin signaling, adenylate cyclase signaling, cell proliferation, and apoptosis. This is the first application of the microarray technique to study hormonal regulation of gene expression in vivo and should prove to be a powerful tool for future studies of hormone and drug action.

New signaling systems in hormonal regulation mechanisms

In his research activities, Nikolai Alekseevich Yudaev paid great attention to the study of the mechanisms of the biological action of hormones. He extremely liked the postulate that hormones regulate gene expression. Great interest in this problem predetermined the choice of the topic of this lecture at scientific readings devoted to his memory. The proposed publication is devoted to the consideration of new data on intracellular signal transduction of a number of hormones, such as growth hormone (GH), prolactin, and other protein hormones exhibiting a similar mechanism of biological action. It is well known that GR and prolactin are pituitary hormones, but not everyone knows that they can also be secreted by other tissues and are directly related to the regulation of immune processes.

Steroid hormone receptors: evolution, ligands, and molecular basis of biologic function.

The characterization of the superfamily of nuclear receptors, in particular the steroid/retinoid/thyroid hormone receptors, has resulted in a more complete understanding of how a repertoire of hormonally and nutritionally derived lipophilic ligands controls cell functions to effect development and homeostasis. As transducers of hormonal signaling in the nucleus, this superfamily of DNA-binding proteins appears to represent a crucial link in the emergence of multicellular organisms. Because nuclear receptors bind and are conformationally activated by a chemically diverse array of ligands, yet are closely related in general structure, they present an intriguing example of paralogous evolution. It is hypothesized that an ancient prototype receptor evolved into an intricate set of dimerizing isoforms, capable of recognizing an ensemble of hormone-responsive element motifs in DNA, and exerting ligand-directed combinatorial control of gene expression. The effector domains of nuclear receptors mediate transcriptional activation by recruiting coregulatory multisubunit complexes that remodel chromatin, target the initiation site, and stabilize the RNA polymerase II machinery for repeated rounds of transcription of the regulated gene. Because some nuclear receptors also function in gene repression, while others are constitutive activators, this superfamily of proteins provides a number of avenues for investigating hormonal regulation of gene expression. This review surveys briefly the latest findings in the nuclear receptor field and identifies particular areas where future studies should be fruitful. J. Cell. Biochem. Suppls. 32/33:110-122, 1999.

Calreticulin

Calreticulin is an ancient and highly conserved protein. It is intensively studied and has been assigned multiple functions, the scope and variety of which are exceptionally wide for a single protein. Subsequent to the description of its calcium binding properties, calreticulin has been characterized as a molecular chaperone, an extracellular lectin, an intracellular mediator of integrin function, an inhibitor of steroid hormone-regulated gene expression and a C1q-binding protein. That one protein can perform so many functions is at once intriguing and controversial and further investigation is clearly required in order to fully understand the functions of calreticulin and elucidate its roles in disease. Based on current knowledge, calreticulin is being examined as a possible target for therapeutic intervention in steroid hormone-dependent conditions, such as osteoporosis, as well as for the development of novel anti-thrombotic agents.

Nuclear Matrix Acceptor Binding Sites for Steroid Hormone Receptors: A Candidate Nuclear Matrix Acceptor Protein

Steroid/nuclear-hormone receptors are ligand-activated transcription factors that have been localized to the nuclear matrix. The classic model of hormone action suggests that, following activation, these receptors bind to specific "steroid response elements" on the DNA, then interact with other factors in the transcription initiation complex. However, evidence demonstrates the existence of specific chromatin proteins that act as accessory factors by facilitating the binding of the steroid receptors to the DNA. One such protein, the "receptor binding factor (RBF)-1", has been purified and shown to confer specific, high-affinity binding of the progesterone receptor to the DNA. Interestingly, the RBF-1 is localized to the nuclear matrix. Further, the RBF-1 binds specifically to a sequence of the c-myc proto-oncogene that has the appearance of a nuclear matrix attached region (MAR). These results, and other findings reviewed here, suggest that the nuclear matrix is involved intimately in steroid hormone-regulated gene expression.

A structural role for hormone in the thyroid hormone receptor.

The crystal structure of the rat alpha 1 thyroid hormone receptor ligand-binding domain bound with a thyroid hormone agonist reveals that ligand is completely buried within the domain as part of the hydrophobic core. In addition, the carboxy-terminal activation domain forms an amphipathic helix, with its hydrophobic face constituting part of the hormone binding cavity. These observations suggest a structural role for ligand, in establishing the active conformation of the receptor, that is likely to underlie hormonal regulation of gene expression for the nuclear receptors.

Molecular Model Systems in the Lepidoptera

List of contributors Preface 1. A brief history of Lepidoptera as model systems Judith H. Willis, Adam S. Wilkins and Marian R. Goldsmith 2. Genetics of the silkworm: revisiting an ancient model system Marian R. Goldsmith 3. Mobile elements of lepidopteran genomes Thomas H. Eickbush 4. Lepidopteran phylogeny and applications to comparative studies of development Jerome C. Regier, Timothy Friedlander, Robert F. Leclerc, Charles Mitter and Brian M. Wiegmann 5. A summary of lepidopteran embryogenesis and experimental embryology Lisa M. Nagy 6. Roles of homeotic genes in the Bombyx body plan Kohji Ueno, Toshifumi Nagata and Yoshiaki Suzuki 7. Chorion genes: an overview of their structure, function, and transcriptional regulation Fotis C. Kafatos, George Tzertzinis, Nikolaus A. Spoerel and Hanh T. Nguyen 8. Chorion genes: molecular models of evolution Thomas H. Eickbush and John A. Izzo 9. Regulation of the silk protein genes and the homeobox genes in silk gland development Chi-chung Hui and Yoshiaki Suzuki 10. Control of transcription by Bombyx mori RNA polymerase III Karen U. Sprague 11. Hormonal regulation of gene expression during lepidopteran development Lynn M. Riddiford 12. Lepidoptera as model systems for studies of hormone action on the central nervous system James W. Truman 13. Molecular genetics of moth olfaction: a model for cellular identity and temporal assembly of the nervous system Richard G. Vogt 14. Molecular biology of the immune response Amy B. Mulnix and Peter E. Dunn 15. Engineered baculoviruses: molecular tools for lepidopteran developmental biology and physiology and potential agents for insect pest control Kostas Iatrou 16. Epilogue: Lepidopterans as model systems - questions and prospects Adam S. Wilkins and Marian R. Goldsmith References Index.

Involvement of MAP kinase in insulin signalling revealed by non-invasive imaging of luciferase gene expression in single living cells.

Studies of the mechanisms by which signals are transmitted from receptor tyrosine kinases would be facilitated by a way of monitoring events at the single-cell level. We have explored how luciferase imaging can be used to examine the role of specific signalling pathways in insulin-stimulated gene expression. The analysis of luciferase expression in single cells has previously been hampered by the insensitivity of existing methodologies and the lack of a way of monitoring quantitatively, and independently, more than one promoter within the same cell. We have developed a technique for examining the dynamics of insulin-stimulated AP-1-dependent transcription in single living cells, and have explored the signalling pathway involved. Luciferase and aequorin gene expression were examined in single living cells with a high-sensitivity photon-counting camera. The technique involved the comicroinjection of luciferase- and aequorin-based reporter plasmids directly into the cell nucleus, and the subsequent analysis of luminescence in the presence of luciferin and coelenterazine, respectively. The method is quantitative and allows insulin-stimulated gene expression to be monitored in real time. We found that insulin promoted a substantial increase in the expression of a luciferase gene under the control of the AP-1-binding site from the collagenase gene promoter. Aequorin expression, under the control of a cytomegalovirus promoter, was unaffected by insulin. The effect of insulin on luciferase expression was specifically blocked by overexpression of either the mitogen-activated protein (MAP) kinase phosphatase CL100, or the dominant-negative mutant MAP kinase kinase, MEKS217/221A. Microinjection coupled with luciferase imaging allows hormone-regulated gene expression from relatively weak promoters to be monitored in single living cells. We have used this method to demonstrate that MAP kinase plays a central role in the ability of insulin to stimulate AP-1-dependent gene transcription.

Hormonal Regulation of Opioid Peptide Neurons in the Anteroventral Periventricular Nucleus

Steroid hormones provide a means of coordinating the activity of widespread neural systems that mediate endocrine, autonomic, and somatomotor aspects of reproductive processes that are essential for the propagation of mammalian species. Because these processes are quite different in each sex, the neural pathways that control them are also sexually differentiated. The anteroventral periventricular nucleus (AVPV) of the preoptic region occupies a nodal point in sexually dimorphic forebrain circuits and appears to play a critical role in regulating gonadotropin secretion. The AVPV contains sexually dimorphic populations of opioid peptide containing neurons that display different patterns of development and are differentially regulated in adult animals by gonadal steroids. Moreover, estrogen (ER) and progesterone (PR) receptors are expressed in AVPV neurons in a transmitter-specific way, and the expression of these nuclear transacting factors is differentially regulated by sex steroids. Thus, neurons in the AVPV show distinct patterns of hormonal regulation of gene expression, and distinct hormone receptor profiles.

B3-53 Dehydrin:Hormonal regulation of gene expression and approached towards dehydrin function

B3-53 Dehydrin:Hormonal regulation of gene expression and approached towards dehydrin function

Hormonal regulation of gene expression

The involvement of plant hormones in the regulation of gene expression is well-recognized. Current research using molecular approaches has resulted in the isolation and characterization of a number of hormone-responsive genes and cDNAs. These genes are proving to be valuable molecular probes to study the mode of action of plant hormones. This review will briefly describe some recent molecular data from selected hormone-responsive plant systems. Results of these studies indicate potential complexity in the regulation of these genes. These results and future challenges are discussed.

The Stringency and Magnitude of Androgen-Specific Gene Activation are Combinatorial Functions of Receptor and Nonreceptor Binding Site Sequences

The mechanism by which specific hormonal regulation of gene expression is attained in vivo is a paradox in that several of the steroid receptors recognize the same DNA element in vitro. We have characterized a complex enhancer of the mouse sex-limited protein (Slp) gene that is activated exclusively by androgens but not by glucocorticoids in transfection. Potent androgen induction requires both the consensus hormone response element (HRE) and auxiliary elements residing within the 120-bp DNA fragment C' delta 9. Multiple nonreceptor factors are involved in androgen specificity, with respect to both the elevation of androgen receptor activity and the inactivity of glucocorticoid receptor (GR), since clustered base changes at any of several sites reduce or abolish androgen induction and do not increase glucocorticoid response. However, moving the HRE as little as 10 bases away from the rest of the enhancer allows GR to function, suggesting that GR is repressed by juxtaposition to particular factors within the androgen-specific complex. Surprisingly, some sequence variations of the HRE itself, within the context of C' delta 9, alter the stringency of specificity, as well as the magnitude, of hormonal response. These HRE sequence effects on expression correspond in a qualitative manner with receptor binding, i.e., GR shows a threefold difference in affinities for HREs amongst which androgen receptor does not discriminate. Altering the HRE orientation within the enhancer also affects hormonal stringency, increasing glucocorticoid but not androgen response. The effect of these subtle variations suggests that they alter receptor position with respect to other factors. Thus, protein-protein interactions that elicit specific gene regulation are established by the array of DNA elements in a complex enhancer and can be modulated by sequence variations within these elements that may influence selection of precise protein contacts.

The stringency and magnitude of androgen-specific gene activation are combinatorial functions of receptor and nonreceptor binding site sequences.

The mechanism by which specific hormonal regulation of gene expression is attained in vivo is a paradox in that several of the steroid receptors recognize the same DNA element in vitro. We have characterized a complex enhancer of the mouse sex-limited protein (Slp) gene that is activated exclusively by androgens but not by glucocorticoids in transfection. Potent androgen induction requires both the consensus hormone response element (HRE) and auxiliary elements residing within the 120-bp DNA fragment C' delta 9. Multiple nonreceptor factors are involved in androgen specificity, with respect to both the elevation of androgen receptor activity and the inactivity of glucocorticoid receptor (GR), since clustered base changes at any of several sites reduce or abolish androgen induction and do not increase glucocorticoid response. However, moving the HRE as little as 10 bases away from the rest of the enhancer allows GR to function, suggesting that GR is repressed by juxtaposition to particular factors within the androgen-specific complex. Surprisingly, some sequence variations of the HRE itself, within the context of C' delta 9, alter the stringency of specificity, as well as the magnitude, of hormonal response. These HRE sequence effects on expression correspond in a qualitative manner with receptor binding, i.e., GR shows a threefold difference in affinities for HREs amongst which androgen receptor does not discriminate. Altering the HRE orientation within the enhancer also affects hormonal stringency, increasing glucocorticoid but not androgen response. The effect of these subtle variations suggests that they alter receptor position with respect to other factors. Thus, protein-protein interactions that elicit specific gene regulation are established by the array of DNA elements in a complex enhancer and can be modulated by sequence variations within these elements that may influence selection of precise protein contacts.

Hormonal Regulation of Gene Expression in Cultured Adipocytes1

Cultured adipocytes provide a convenient system to examine the molecular basis of tissue-specific hormonal control of gene expression. We have examined the regulation of the S14 protein (17 kDa, 4.9 pI) in cultured adipocytes. The S14 protein serves as a model for lipogenic gene expression. Whereas both glucocorticoids (GC) and retinoic acid (RA) induce S14 gene transcription in adipocytes, neither hormone activates S14 gene transcription in preadipocytes. To investigate the molecular basis for this tissue-specific hormonal control, 3T3-L1 preadipocytes were stably transfected with S14-chloramphenicol acetyl transferase (CAT) fusion genes. Both GC and RA induced S14CAT activity in adipocytes, but not in preadipocytes, indicating that cis-linked targets for GC, RA, and tissue-specific control were located upstream from the 5′ end of the S14 gene. Analysis of the expression of CAT fusion genes containing canonical GC and RA response elements showed that endogenous GC and RA receptors activated these genes in both preadipocyte and adipocyte phenotypes. Thus, the GC and RA regulatory networks were operative in both cell types. Deletion analysis of the S14CAT fusion genes showed that the cis-linked elements that conferred the GC, RA, and tissue-specific control were located between −1,381 and −1,588 bp upstream from the 5′ end of the S14 gene. Gel shift and DNase I footprint analysis indicated that nuclear proteins interacting with this region were under tissue-specific control. We speculate that tissue-specific proteins modulate the activity of GC/RA regulated proteins that interact with the S14 GC/RA response region.

Hormonal regulation and properties of a new group of basic hemolymph proteins expressed during insect metamorphosis.

Two abundant basic proteins, and arylphorin, that are expressed during metamorphosis of Trichoplusia ni were isolated, their cDNAs cloned, and regulation of their expression assessed. According to the criteria of encoded protein sequence, positions of sequence coinitiation and cotermination, amino acid compositions, nonsex-specificity, and immunological analyses, the related yet distinct basic proteins do not correspond to any previously established group of insect proteins, each of which can be distinguished on the basis of such criteria, although they appear to be within the arthropod hemocyanin superfamily. The basic proteins can be separated under native isoelectric focusing conditions, indicating that they do not preferentially form heteromeric complexes under such conditions. While the transcripts for both basic proteins and a coexpressed acidic protein (Jones, G., Brown, N., Manczak, M., Hiremath, S., and Kafatos, F. (1990) J. Biol. Chem. 265, 8596-8602) appeared in both sexes on the day prior to ecdysteroid-driven metamorphic commitment, and persisted at high abundance for the next 24 h, the arylphorin mRNA appeared 1 day earlier and declined immediately after metamorphic commitment. The dynamics of suppression of the appearance and abundance of transcripts in response to maintenance of a high juvenile hormone titer was different for the acidic versus the two basic proteins. Another regulatory difference in response to juvenile hormone was shown by a decreased translatability of the mRNAs for the two basic proteins, but not for the acidic protein. In contrast, the abundance and translatability of arylphorin mRNA was insensitive to a high juvenile hormone level. A further difference in regulation was shown by the maintenance of a high level of both arylphorin and the acidic protein in the hemolymph after disappearance of their transcripts, while the basic proteins instead disappeared from the hemolymph and persisted in the fat body. These results establish at least three qualitatively different effects of juvenile hormone on the abundance of transcripts for these representatives of three groups in the hemocyanin superfamily, and also establish mRNA translatability as another differential level of regulation among them. Given these differences in mechanisms of regulation of evolutionarily related proteins, this system of metamorphosis-associated proteins in T. ni should prove to be a valuable tool in studies of mechanisms of hormonal regulation of gene expression during the metamorphic transformation of larval tissues.

The thyroid hormone response element is required for activation of the growth hormone gene promoter by nicotinamide analogs

N′-Methylnicotinamide and nicotinamide, which decreased in vitro ADP-ribosylation of nuclear proteins and/or cellular NAD + content, selectively increased the basal expression of the rat growth hormone (GH) gene promoter and its response to triiodothyronine (T3). This increase was not found when the thyroid hormone response element (TRE) was deleted from the promoter. Transfection with an expression vector for the T3 receptor inhibited basal activity of the TRE-containing promoter and repressed the stimulatory effect of N′-methylnicotinamide. The addition of hormone relieved this inhibition and enhanced transcription above levels found in the absence of the transfected receptors. These results suggest a modulatory role of ADP-ribosylation in hormonal regulation of gene expression.

Molecular Physiology of the Regulation of Hepatic Gluconeogenesis and Glycolysis

Understanding the regulation of hepatic glucose metabolism had its foundation in the elucidation of several pathways, but recent advances have come from the application of molecular genetics. Five years ago little was known about the primary structure of the key regulatory enzymes. Since then, the primary sequence of liver GK, 6-PF-1-K, Fru-1,6-P2ase, PK, PEPCK, and 6-PF-2-K/Fru-2,6-P2ase have been derived from cDNA sequences and/or determined by direct protein sequencing. This has provided new insights into the molecular mechanisms of catalysis and the regulation of these enzymes by covalent modification. Isolation of the cDNAs for these enzymes also has allowed for the quantitation of specific mRNAs and permitted analysis of hormonal control of specific gene expression. The genes for these enzymes have been isolated and sequenced, and their promoter regions are being identified and characterized. Hormone response elements have been delineated in several of the promoters. The promoter regions for 6-PF-2-K/Fru-2,6-P2ase and Fru-1,6-P2ase have also been identified, and future research will focus on the elucidation of the mechanisms whereby hormones regulate the expression of these genes. A number of generalizations can be made about the regulation of gene expression of glycolytic/gluconeogenic enzymes. First, there is coordinate hormonal regulation of gene expression and these effects are consonant with their physiologic actions. Insulin induces the mRNAs that encode glycolytic enzymes and represses the mRNAs that encode gluconeogenic enzymes; cAMP has opposite effects. Both can increase or decrease transcription. Whereas insulin and cAMP affect all of these mRNAs, glucocorticoids appear to have a more restricted action. Second, transcriptional and posttranscriptional regulatory mechanisms are involved. The synthesis of all of the mRNAs discussed is regulated by hormones. Relatively little is known about how mRNA stability is regulated in general, but it is clear that PEPCK mRNA is stabilized by agents that increase the rate of transcription of the gene. Under appropriate metabolic signals this dual control of mRNA synthesis and stability provides for a long-term increase in PEPCK mRNA and protein. Studies with PK mRNA are less direct, but suggest a similar dual mechanism. It will be interesting to see whether multilevel regulation is restricted to these two mRNAs, both of which are involved in the same substrate cycle, or whether the stability of other mRNAs involved in hepatic glucose metabolism is also affected. Third, glucose appears to be important in the regulation of these hepatic genes.(ABSTRACT TRUNCATED AT 400 WORDS)

Calbindin-D 9k gene expression during pregnancy and lactation in the rat

Calbindin-D 9k (CaBP-9k) is a calcium binding protein expressed in mammalian intestine, uterus and placenta. It is believed to be involved in transepithelial calcium transport in intestine and placenta and regulation of cytosolic calcium concentration in uterus. CaBP-9k mRNA levels were measured by Northern blot analysis in maternal duodenum, uterus, placenta and fetal/neonatal duodenum during pregnancy and lactation. In maternal duodenum a maximal increase occurred at day 15 of lactation (2.3-fold) and 20 days post-lactation levels decrease to 30.3% of non-pregnant controls. In non-pregnant uterus a 10-fold variation of CaBP-9k mRNA levels was observed between individual animals despite a uniform expression of β-actin. During pregnancy high CaBP-9k expression is found, averaging about 20% of duodenal levels, which abruptly drops below detection during early lactation. At late lactation CaBP-9k mRNA levels are again subject to great variation ranging from no expression to maximal levels found in the non-pregnant uterus. Placental CaBP-9k is maximally expressed at the end of pregnancy (day 20) reaching about 2.5% of duodenal levels. Fetal intestinal CaBP-9k mRNA was detectable in 20 μg total RNA at day 18 of pregnancy and rose sharply in early lactation reaching about 50% of adult duodenal levels at day 20 lactation. The profound changes of uterine CaBP-9k mRNA in non-pregnant (cycling), pregnant, and lactating rats indicate a rapid hormonal regulation of gene expression, most likely involving 17β-estradiol.