Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of media conditions on the glucocorticoid response has been examined in three types of cultured cells. In rat pituitary tumor cells (GC cells) growth hormone production was stimulated by glucocorticoids provided fresh culture media was present (enriched media conditions). In contrast, dexamethasone either failed to induce or deinduce growth hormone synthesis if added to cultures which had not received fresh media for 3 days (depleted media condition). With human skin fibroblasts, cortisol stimulated [3H]thymidine incorporation in the enriched condition but inhibited this response in the depleted condition. In mouse lymphoma (S49) cells the enriched media conditions significantly delayed the killing response to glucocorticoids (20% killing after 24 h versus 90% killing after 24 h for the depleted condition). Thus, the magnitude and in some cases, the direction of the glucocorticoid response are sensitive to the conditions to which the cells are exposed. In all three cell types the steroid also rapidly (detectable by 15 min, maximal by 2 h) altered chromatin structure as detected by a change in the number of initiation sites for Escherichia coli RNA polymerase assayed under cell-free conditions. This early nuclear response could be in a positive or negative direction and was also affected by the culture conditions; enriched media favored a positive or less negative effect on the initiation sites by the steroid, while depleted media favored a steroid-induced inhibition of this chromatin function. In S49 and GC cells the kinetics and magnitude of the change in chromatin closely followed receptor . glucocorticoid complex binding to nuclei while removal of dexamethasone from the culture media resulted in a rapid (t 1/2 = approximately 20 min) disappearance of the effect which paralleled loss of bound hormone from the nucleus. The glucocorticoid effect on chromatin was not observed in two lines of glucocorticoid-resistant mutant S49 cells. One line (R-) lacks detectable glucocorticoid receptors; the other line (Nti) has receptors that bind the hormone normally, but the receptor . glucocorticoid complexes bind more avidly to the nucleus. These results suggest that the receptor is involved in both the stimulatory and the inhibitory effects on chromatin. The findings in the Nti cells and of a slight lag between nuclear binding of receptors and initiation site alteration implies that some receptor property, in addition to nuclear binding per se, is responsible for the influence on chromatin. These results are discussed in terms of a model in which steroid hormones initiate their actions by influencing a reaction that modifies chromatin structure. The direction and magnitude of the reaction, and its effect on the expression of specific genes, are dictated by the metabolic state and differentiation of the cell.
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PMID:Stimulation and inhibition of cellular functions by glucocorticoids. Correlations with rapid influences on chromatin structure. 46 88

Cultured rat pituitary tumor cells, GH3/D6, which synthesize both growth hormone and prolactin, have cell-surface epidermal growth factor (EGF) receptor sites (34,000 per cell) that bind 125I-labeled EGF with a high affinity (Kd approximately 1 nM). Prolonged treatment of the cells with EGF did not stimulate cell division but did inhibit thyroid hormone-stimulated cell growth. In addition, EGF altered the morphology of the cells from a rounded to an elongated conformation. EGF also induced a perturbation of chromatin structure in GH3 cell nuclei that was detected by an increase (40%) in the number of rifampicin-resistant initiation sites for bacterial RNA polymerase. This was accompanied by an increased synthesis of prolactin and an inhibition of synthesis of growth hormone. In the presence of EGF, the synthesis of growth hormone was no longer inducible by thyroid hormone, but it remained responsive to glucocorticoids. The results demonstrate that EGF can elicit major effects on the cellular phenotype and expression of specific genes in the absence of a proliferative response. This suggests that EGF can also regulate differentiated cellular functions.
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PMID:Epidermal growth factor and expression of specific genes: effects on cultured rat pituitary cells are dissociable from the mitogenic response. 624 57

Using a combination of polymerase chain reaction and genomic library screening we have cloned a human gene for a subtype of the somatostatin (SST) receptor (SSTR) termed human SSTR5 (hSSTR5), which is located on chromosome 16. The predicted amino acid sequence of hSSTR5 displays 75% sequence identity with a recently identified rat SSTR [Mol. Pharmacol. 42:939-946 (1992)], suggesting that it is the human homologue of this receptor. hSSTR5 consists of a 363-residue polypeptide exhibiting a putative seven-transmembrane domain topology typical of G protein-coupled receptors. The receptor displays considerable sequence identity to hSSTR1 (42%), hSSTR2 (48%), hSSTR3 (47%), and hSSTR4 (46%). Membranes prepared from COS-7 cells transiently expressing the hSSTR5 gene bound 125I-Leu8,D-Trp22,Tyr25-SST-28 (125I-LTT-SST-28) with high affinity and in a saturable manner. SST-14, SST-28, and various synthetic SST peptide agonists produced dose-dependent inhibition of radioligand binding with the following rank order of potency: LTT-SST-28 > SST-28 > D-Trp8-SST-14 > SST-14 approximately RC-160 approximately BIM 23014 > MK-678 > SMS 201-995. hSSTR5 bound SST-28 with a 12.6-fold greater affinity (Ki = 0.19 nM), compared with SST-14 (Ki = 2.24 nM), indicating that the receptor is SST-28 selective. Addition of GTP, guanosine-5'-O-(3-thio)triphosphate, Na+ ions, or pertusis toxin greatly reduced 125I-LTT-SST-28 binding, thereby indicating that hSSTR5 is coupled to pertussis toxin-sensitive G proteins. Both SST-14 and SST-28 displayed dose-dependent inhibition of forskolin-stimulated cAMP accumulation, consistent with functional coupling of the receptor to adenylyl cyclase inhibition. Northern blot analysis of SSTR5 mRNA revealed a 2.4-kilobase transcript in normal rat pituitary and GH3 rat pituitary tumor cells and a 4.0-kilobase transcript in normal human pituitary. Reverse transcriptase polymerase chain reaction revealed expression of the hSSTR gene in fetal human pituitary and hypothalamus but not in human cerebral cortex. In situ hybridization of the rat pituitary showed that SSTR5 mRNA is selectively localized in the anterior lobe. SSTR5 mRNA was not expressed in four human pituitary tumors (somatotroph adenoma, prolactinoma, and chromophobe adenomas) or in a human insulinoma. Although hSSTR5 displays approximately 75% sequence identity with rat SSTR5, the two receptors display significantly different pharmacological profiles, especially with respect to their binding affinities for the SST analogue SMS 201-995.
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PMID:Molecular cloning, functional characterization, and chromosomal localization of a human somatostatin receptor (somatostatin receptor type 5) with preferential affinity for somatostatin-28. 790 5

While pituitary tumors can be induced in rats by the administration of estrogen, susceptibility to such tumors is highly strain dependent. In this study, 21-day-old male rats of two strains-Fischer 344 (F344) strain, which is particularly susceptible to pituitary tumors, and Sprague-Dawley (SD) strain, which is relatively resistant, were treated with diethylstilbestrol (DES) over a period of 10 days. Reverse-transcriptase polymerase chain reaction (RT-PCR) was used to analyze the expression levels of two tumor suppressor genes, p53 and rb, in the pituitaries. In SD rats, both p53 and rb mRNA appeared to increase in response to DES treatment, while in F344 rats they remained undetectable. Western blot analysis revealed that protein levels of cyclin D, which is a cell cycle regulating protein thought to be a potential oncogene, decreased in response to DES treatment in F344 rats but remained constant in SD rats. The observed differences in the expression levels of p53, rb and cyclin D suggest that they might be involved in the primary process of estrogen-induced pituitary tumor development prior to detectable tumor growth.
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PMID:Potential involvement of tumor suppressor gene expression in the formation of estrogen-inducible pituitary tumors in rats. 1081 Dec 86

Very few of the genes that are important in pituitary tumor initiation, progression, and metastasis have been identified to date. To identify potential genes that may be important in pituitary tumor progression and carcinoma development, we used Affymetrix GeneChip HGU-133A-oligonucleotide arrays, which contain more than 15,000 characterized genes from the human genome to study gene expression in an ACTH pituitary carcinoma metastatic to the liver and four pituitary adenomas. Reverse-transcriptase real-time quantitative- PCR (RT-qPCR) was then used to analyze 4 nonneoplastic pituitaries, 19 adenomas, and the ACTH carcinoma. A larger series of pituitary adenomas and carcinomas were also analyzed for protein expression using tissue microarrays (TMA) (n = 233) and by Western blotting (n = 18). There were 4298 genes that were differentially expressed among the adenomas compared to the carcinoma, with 2057 genes overexpressed and 2241 genes underexpressed in the adenomas. The beta-galactoside binding protein galactin-3 was underexpressed in some adenomas compared to the carcinomas. Prolactin (PRL) and ACTH tumors had the highest levels of expression of galectin-3. The human achaetescute homolog-1 ASCL1 (hASH-1) gene was also underexpressed in some adenomas compared to the carcinoma. Prolactin and ACTH tumors had the highest levels of expression of hASH-1. ID2, which has an important role in cell development and tumorigenesis, was underexpressed in some adenomas compared to the carcinomas. Transducin-like enhancer of split four/ Groucho (TLE-4) was over-expressed in adenomas compared to the ACTH carcinoma. The differential expression of these genes was validated by RT-qPCR, by immunohistochemistry using TMA and by Western blotting. These results indicate that the LGALS3, hASH1, ID2, and TLE-4 genes may have important roles in the development of pituitary carcinomas.
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PMID:Patterns of gene expression in pituitary carcinomas and adenomas analyzed by high-density oligonucleotide arrays, reverse transcriptase-quantitative PCR, and protein expression. 1694 82

Pituitary tumor transforming gene is an important gene which is involved in many cellular functions including cell division, DNA repair, organ development, expression, and secretion of various angiogenic and metastatic factors. Overexpression of this gene has also been reported in many cancers. Understanding the molecular pathways induced by this oncogene is therefore important not only to understand the development of the disease but also for proper diagnosis and treatment. Gene profiling is an excellent tool to identify the genetic mechanisms, networks, and pathways associated with a particular disease. Oligo-nucleotide microarrays can be everybody's choice as a first step to identify the global expression of genes involved in the study of interest. Each technique has its own limitation. Therefore, further confirmation of the results with a different technique is always necessary. Quantitative real-time reverse-transcriptase polymerase chain reaction (qRT-PCR) is one of the widely used and best described techniques to confirm the microarray data. Here, we describe the qRT-PCR techniques for gene profiling studies and the methods used for the analysis of the output data for further studies.
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PMID:Using quantitative real-time reverse transcriptase polymerase chain reaction to validate gene regulation by PTTG. 2213 Sep 89