Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation of the expression of beta-adrenoceptor (beta-ARs) is not thoroughly understood. We demonstrate that the rat heart cell-line H9c2 expresses both beta 1- and beta 2-ARs. In radioligand-binding experiments, the maximal binding capacity of (-)-[125I]-iodocyanopindolol was determined as 18 +/- 0.6 fmol/mg of protein with a KD of 35.4 +/- 4.1 pM. Competitive radioligand-binding experiments with subtype-specific beta-antagonists reveal a subtype ratio of beta 1- to beta 2-ARs of 29%: 71%. With competitive reverse-transcriptase PCR we found beta 2-mRNA to be up to 1600 times more frequent than beta 1-mRNA. Treatment of the H9c2 cell-line with the beta-adrenergic agonist (-)-isoproterenol (10(-6) M), the antagonist (-)-propranolol (10(-6) M) and the glucocorticoid dexamethasone (500 nM) induces regulatory effects on both the beta-AR protein and mRNA level. Isoproterenol treatment leads to down-regulation of the total receptor number by 56 +/- 4%, due to a decrease in beta 2-ARs, while maintaining the beta 1-AR number constant. On the transcription level, both beta 1-and beta 2-mRNAs are decreased by 30% and 42% respectively. mRNA stability measurements reveal a reduced half-life of beta 2-mRNA from 9.3 h to 6.5 h after isoproterenol treatment. Incubation of cells with (-)-propranolol does not affect the amounts of beta-ARs and their mRNAs. Dexamethasone induces a 1.8 +/- 0.2-fold increase in beta-AR number over the basal level as well as a 1.9 +/- 0.2-fold increase in the amount of beta 2-mRNA. Because the half-life of beta 2-mRNA was unaffected by dexamethasone, the increased beta 2-mRNA level must be due to an enhanced transcription rate. The beta 1-mRNA levels are unchanged during dexamethasone-incubation of the cells. Our data clearly demonstrate that treatment of H9c2 rat heart cells with isoproterenol and dexamethasone induces alterations in the level of RNA stability as well as gene transcription, leading to altered receptor numbers.
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PMID:Regulation of beta-adrenoceptor density and mRNA levels in the rat heart cell-line H9c2. 876 Mar 84

Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by a sustained elevation of the platelet count in the absence of other causes of thrombocytosis. ET is difficult to diagnose, and the demonstration of clonal hematopoiesis may be of value. However, clonality analysis of hematopoietic cells based on the study of the X-chromosome inactivation pattern is complicated by the observation that some normal females present skewed lyonization. Moreover, DNA methylation of X-linked genes in hematopoietic cells may differ from that in other tissues. Appropriate controls for skewed lyonization are therefore critical for the study of clonality. We developed two techniques based on X-chromosome inactivation and polymerase chain reaction (PCR) analysis of polymorphisms, to study clonality in ET patients. Reverse transcriptase-PCR analysis of IDS, P55, and G6PD mRNAs was used to examine the different hematopoietic cell lineages including platelets in patients heterozygous for these polymorphisms and analysis of the HUMARA gene methylation pattern permitted us to study clonality in all nucleated cell fractions of the other patients. Using both types of assay and T lymphocytes as a control tissue for lyonization, clonal hematopoiesis was demonstrated in 28 patients. In 14 patients, the granulocytes were polyclonal; among these patients, platelets were monoclonal in 3 cases, polyclonal in 7 cases, and in the remaining 4 cases this fraction could not be studied because the patients were homozygotes for all RNA markers. No conclusion about clonality could be drawn in 6 cases. Polyclonal hematopoiesis was found in all the cases of reactive thrombocytosis. These findings confirm the high frequency of monoclonal hematopoiesis in ET, the utility of studying platelets, and the possibility of using T lymphocytes as a control tissues for X-chromosome inactivation patterns.
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PMID:Clonality analysis of hematopoiesis in essential thrombocythemia: advantages of studying T lymphocytes and platelets. 897 85

Mutations of the androgen receptor (AR) gene and protein are associated with complete androgen insensitivity syndromes (CAIS) in individuals with XY genotypes causing them to develop as phenotypic females. Splice site mutations of the AR gene are very rare and in this report we describe the consequences of a novel G --> A mutation at the exon 7/intron 7 splice junction of the AR gene that resulted in CAIS in two siblings. Reverse transcriptase-polymerase chain reaction (RT-PCR) of the AR transcript in patient's fibroblasts was performed and sequencing of the product showed omission of exon 7, with exon 6 being spliced directly to exon 8. This resulted in a shift of the reading frame and the introduction of a premature stop codon 10 amino acids into exon 8. Immunoblot analyses showed that the resultant AR protein was partially deleted in its C-terminal region and was approximately 1.5 kDa smaller than the wild type. This truncated AR was non-functional as it was unable to bind its physiological ligand (dihydrotestosterone) in androgen-binding assays. This is the first documentation of a point mutation in the AR gene which causes exon skipping and proves that the mutation is the cause of CAIS in our two subjects.
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PMID:A novel splice site mutation in the androgen receptor gene results in exon skipping and a non-functional truncated protein. 929 79

Recent studies have shown a higher incidence of C-cell hyperplasia (CCH) in men compared with women in postmortem thyroid tissues. We postulated that the expression of androgen receptor (AR) protein may, in part, explain the differences. To test this hypothesis, we examined thyroid tissue from 27 consecutive autopsy cases for the presence of CCH (defined as >50 C-cells/x100 magnification in three fields) and for AR expression in autopsy cases and in 43 medullary thyroid carcinomas (MTCs) from patients with sporadic and familial disease as well as two multiple endocrine neoplasia type 2A patients with only CCH. CCH was present in 8 of 20 males (40%) and in 1 of 7 females (14%) at autopsy. AR protein was detected in most surgically resected thyroids with MTC and CCH (80%), but in only 25% of autopsy thyroids, probably reflecting postmortem degradation of the receptor protein. Reverse transcriptase polymerase chain reaction confirmed the presence of AR mRNA in MTC and in papillary thyroid carcinomas. These results support the observation that CCH is more common in postmortem thyroids of males and suggest that the presence of AR with higher circulating levels of androgens may contribute to the higher incidence of CCH in men.
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PMID:Androgen receptor expression in C-cells and in medullary thyroid carcinoma. 1285 7