Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is established that testosterone (T) increases aromatase activity (AA) in the quail brain and that this induction of AA represents a limiting factor in the activation of male copulatory behavior. This action of T presumably results from an induction of aromatase synthesis since the number of aromatase-immunoreactive (ARO-ir) cells increases and, in parallel, there is an increase in aromatase mRNA as measured by reverse transcriptase-polymerase chain reaction (RT-PCR) technology. The specific role of androgenic and estrogenic metabolites of T in this induction is not yet clear but product-formation assays suggest that both types of compounds synergize to increase AA. The exact role of androgens and estrogens in the induction of aromatase was examined by studying both the aromatase protein by immunocytochemistry and the aromatase mRNA by RT-PCR in castrated quail that had been treated with T or its androgenic metabolite, 5 alpha-dihydrotestosterone (DHT) or its estrogenic metabolite, estradiol-17 beta (E2) or both DHT and E2 simultaneously. A specific quantitative PCR technique using a modified aromatase as internal standard was developed for this purpose. T increased the number of ARO-ir cells in all brain areas and increased the concentration of ARO mRNA in the preoptic area-anterior hypothalamus (POA-aHYP) and in the posterior hypothalamus (pHYP). E2-treated birds had more ARO-ir cells than castrates in the posterior part of the medial preoptic nucleus (POM), in the bed nucleus stria terminalis (BNST) and tuber. Their aromatase mRNA concentration was significantly increased in the POA-aHYP but this effect did not reach significance in the pHYP. DHT by itself had no effect on either the number of ARO-ir cells (all brain regions considered) or the concentration of aromatase mRNA. DHT, however, synergized with E2, both in inducing ARO-ir neurons and in increasing aromatase mRNA concentration. This synergism was shown to be statistically significant in several brain areas. These data demonstrate that both androgens and estrogens regulate aromatase at the pretranslational level. Because the percentage increase in the number of ARO-iR cells was in general very similar to the increase in aromatase mRNA concentration, these data also suggest that these steroids regulate aromatase mostly by changing its mRNA synthesis or catabolism.
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PMID:Synergism between androgens and estrogens in the induction of aromatase and its messenger RNA in the brain. 824 62

Long-term tamoxifen therapy is associated with increased risk of uterine endometrial cancer and benign alterations. Tamoxifen is metabolized to reactive intermediates by endometrial tissue, and tamoxifen therapy-induced DNA adducts have been found in human endometrium. Since metabolic activation is often catalyzed by cytochrome P450 (CYP) enzymes, the expression profile of individual xenobiotic-metabolizing CYP genes was studied in human uterine endometrium by reverse transcriptase-polymerase chain reaction. The following CYP mRNAs were detected: CYP2B6, CYP2C, CYP2E1, CYP3A4, CYP3A5, CYP4B1, and CYP11A. Amplification of CYP1A1, CYP1A2, CYP2A6, CYP2D6, CYP2F1, CYP3A7, and CYP19 was not found. CYP3A5 and CYP4B1 transcripts were found only in samples from premenopausal women. These data suggest that the human endometrial epithelium has the potential of producing CYP enzymes known to generate genotoxic intermediates from tamoxifen and metabolites that affect oestrogen receptors.
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PMID:Expression of cytochrome P450 genes encoding enzymes active in the metabolism of tamoxifen in human uterine endometrium. 949 38

In all species of crocodilians, sex is determined not by genetic mechanisms, but by the temperature at which the egg is incubated. In the American alligator (Alligator mississippiensis) the thermosensitive period (TSP) for sex determination is a 7- to 10-day window within stages 21-24 of development, around the middle third of the incubation period. Treating embryos with estrogen during the TSP produces female offspring, even at male incubation temperatures. Conversely, blocking embryonic estrogen synthesis at female-inducing temperature prevents development of the female phenotype. Therefore, it has been suggested that estrogen plays a role in determination of sex in the alligator. Estrogen is produced from an androgen substrate by cytochrome P450 aromatase (CYP19). If estrogen plays a critical role in sex determination, there should be differences in aromatase expression between embryos at male- and female-producing temperatures during the TSP. Therefore, to address this question, we cloned and characterized the alligator CYP19 cDNA. Based on the sequence information, a quantitative kinetic reverse transcriptase-polymerase chain reaction (TaqMan) assay was designed to measure expression of the alligator aromatase gene in RNA extracted from the gonadal and brain regions of alligator embryos incubated at male- or female-producing temperatures from prior to the TSP through hatching. Aromatase expression was detected in the brain region from the earliest stage tested (stage 20) through hatching. The hypothalamus had significantly higher expression than the forebrain or hindbrain in both male and female embryos. Expression was not significantly different in the gonadal region between embryos at male and female temperatures until after the TSP, when there was a dramatic increase in expression at female temperature. These data indicate that aromatase expression and, thus, estrogen production, are not the initial trigger for sex determination but play an essential role in ovarian differentiation in the alligator. J. Exp. Zool. 290:439-448, 2001.
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PMID:Alligator aromatase cDNA sequence and its expression in embryos at male and female incubation temperatures. 1155 51

Cytochrome P450arom, a key enzyme in the hormonal steroidogenic pathway, mediates the conversion of androgens to estrogens. This work describes the molecular cloning of the cDNA encoding the European sea bass (Dicentrarchus labrax L.) cytochrome P450arom by means of reverse transcriptase and polymerase chain reaction (RT-PCR) and 5' and 3'-rapid amplification of cDNA ends (RACE) analyses. The cDNA is 1822bp in length and encodes a putative protein of 517 amino acids. Northern blot analysis revealed that the ovary expressed a transcript of about 2.2kb in size. Analysis of the deduced amino acid sequence indicated 62-86% identity with ovarian P450arom of other teleost fish, the highest identity being found with the Japanese flounder, Paralichthys olivaceous. Identity was lower (56-65%) with the P450arom forms first reported in teleost brain. Only 52% identity was observed with the corresponding fragment of the cartilaginous fish, Dasyatis sabina. RT-PCR revealed that the sea bass P450arom mRNA was also expressed, at low levels, in testis and brain. Between the 5' and 3'-untranslated terminal regions (UTR), the sea bass CYP19 gene contains eight introns. All introns conform to the GT/AG rule for RNA splicing and are inserted in exactly the same positions as those found in Oryzias latipes and the human CYP19 gene.
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PMID:European sea bass (Dicentrarchus labrax L.) cytochrome P450arom: cDNA cloning, expression and genomic organization. 1186 61

This work describes the molecular cloning of the cDNA encoding the rainbow trout (Oncorhynchus mykiss Walbaum) brain cytochrome P450arom by means of reverse transcriptase and polymerase chain reaction (RT-PCR) and 5'- and 3'-rapid amplification of cDNA ends (RACE) analyses. The results obtained demonstrate that, as in other teleost fishes, the trout genome contains, besides the gene previously identified in the ovary, a second CYP19 gene (CYP19B) expressed at high level in the brain. Moreover, two P450aromB mRNAs, forms I and II, were found to be transcribed in trout. Form I (1816 sequenced nt) contains an open reading frame (ORF) of 1464b, a 5'-untranslated terminal region (UTR) of 124b and at least 228b in the 3'-UTR (incomplete, as the polyadenylation signal was not determined). Form II (1930 sequenced nt) contains an ORF of 1362b, a 5'-UTR of 340b and the same 3'-UTR as form I. Form II lacks the first 34 amino acids of form I, corresponding to the membrane-anchoring segment, whereas the sequence of the remaining coding region is almost the same in the two forms, resulting in proteins of 454 and 488 amino acids, respectively. Whether the two transcripts derive from the same gene by alternative splicing or are encoded by different CYP19B genes remains to be clarified. On Northern blot analyses with brain and ovary specific ORF probes and poly(A)(+)-enriched RNAs from trout ovary and brain, a transcript of about 2.6kb was identified in the ovary, as expected, whereas the full-length mRNA of brain P450arom is about 3.8kb. The brain form is expressed in the brain and gonads, whereas expression in peripheral tissues is limited mostly to the gills. The two trout CYP19 genes are not equivalent in tissue-specific expression, indicating the possibility of distinct promoters and regulatory mechanisms.
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PMID:Cloning of two mRNA variants of brain aromatase cytochrome P450 in rainbow trout (Oncorhynchus mykiss Walbaum). 1242 36

Ghrelin, a growth hormone-releasing hormone produced by gastroenteropancreatic endocrine cells, hypothalamus, and pituitary, was recently identified in medullary thyroid carcinomas and derived cell lines. However, no data exist on its expression in either normal or neoplastic thyroid follicular cells. We analyzed ghrelin expression by immunohistochemistry, in situ hybridization, and reverse transcriptase-polymerase chain reaction in 15 fetal, 4 infant, and 10 adult thyroids, and in 54 tumors of follicular origin. We also analyzed the effects of ghrelin on cell proliferation in N-PAP and ARO thyroid carcinoma cell lines. Ghrelin-binding sites were investigated using reverse transcriptase-polymerase chain reaction to detect its growth hormone secretagogue receptor (GHS-R) mRNA and an in situ-binding localization procedure. Strong ghrelin immunoreactivity was found in fetal but not in infant or adult thyroids. Ghrelin protein and mRNA were present, in variable amounts, in benign and malignant tumors. Normal thyroids, thyroid tumors, and cell lines showed ghrelin binding sites by binding localization, in the absence of the specific GHS receptor mRNA (with the exception of one normal thyroid). Moreover, ghrelin induced dose-dependent inhibition of growth in cell lines. In conclusion, ghrelin is expressed in fetal but not in adult thyroid, and is re-expressed in tumors; the presence of ghrelin receptors other than GHS-R in normal and neoplastic adult thyroid is suggested; ghrelin inhibits cell proliferation of thyroid carcinoma cell lines in vitro.
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PMID:Ghrelin in fetal thyroid and follicular tumors and cell lines: expression and effects on tumor growth. 1254 22

Development of antral follicles beyond 3 to 4 mm in cattle appears as a wave pattern that occurs two to three times during the estrous cycle. Each wave presents a cyclic recruitment of multiple follicles at the 3- to 4-mm stage, followed by the selection of a single follicle that becomes the dominant follicle (DF). The molecular determinants involved in the follicular dominance process remain poorly understood. The objective of the current study was to compare gene expression in granulosa cells (GCs) between growing dominant follicles from Day 5 of the estrous cycle and nonselected small follicles (<or=4 mm) using the suppression subtractive hybridization (SSH) approach to identify candidate genes differentially expressed in GCs of the DF. Small follicle cDNAs were subtracted from DF cDNAs (DF-SF) and used to establish a DF GC-subtracted cDNA library. A total of 42 nonredundant cDNAs were identified. Detection of previously identified genes such as CX43, CYP19, INHBA, and SERPINE2 supported the validity of our experimental model and the use of SSH as the method of analysis. For selected genes such as ApoER2, CPD, CSPG2, 14-3-3 epsilon, NR5A2/SF2, RGN/SMP30, and SERPINE2, gene expression profiles were compared by virtual Northern blot or reverse transcriptase-polymerase chain reaction, and results confirmed an increase or induction of their mRNA in GCs of dominant follicles compared with that of small follicles. We conclude that we have identified novel genes (known and unknown) that are up-regulated in bovine GCs that may affect follicular growth, dominance, or both.
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PMID:Gene expression profiling of differentially expressed genes in granulosa cells of bovine dominant follicles using suppression subtractive hybridization. 1456 16

A number of conditions related to sex-reversal in boys and men and precocious puberty in girls are caused by estrogen-secreting adrenal tumors. In these tumors, cytochrome P450 aromatase (aromatase) that is encoded in the CYP19 gene is expressed at high levels. To investigate the molecular mechanism of aromatase expression in these adrenal tumors, we characterized the activity, gene transcript and genomic promoter region of aromatase in the human adrenocortical carcinoma cell line H295R. Aromatase activity and the transcript of the CYP19 gene were highly up-regulated by forskolin, but not by dexamethasone. The results from exon I-specific reverse transcriptase (RT)-PCR and the transfection of reporter constructs suggested that promoter I.3 and promoter II were activated in H295R. Deletion and mutation analysis suggested that cAMP response element-like sequence (CLS) and steroidogenic factor-1 (SF-1) motif, were critical for the activation of promoter II. The results of this work should provide the basis for the molecular analysis of aromatase expression in adrenocortical cells.
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PMID:Forskolin up-regulates aromatase (CYP19) activity and gene transcripts in the human adrenocortical carcinoma cell line H295R. 1470 51

To evaluate the feasibility of radionuclide gene therapy, we investigated the effect of sodium iodide symporter (NIS) gene transfection on the uptake of some beta- and gamma-emitters in human anaplastic thyroid cancer. NIS gene was transfected into human anaplastic cancer ARO cells using liposome (ARO-N) and its expression was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR). Iodide uptake by ARO-N was 109 times higher than by ARO, and 99mTc and 188Re uptake by ARO-N were 21 and 47 times higher than by ARO, respectively. The half-lives of radionuclides (125I, 99mTc, and 188Re) retention in the cells were about 12, 3 and 4 min, respectively. Biodistribution studies showed that ARO-N tumors accumulated higher amounts of radionuclides than ARO tumors. The mean accumulations of 125I, 99mTc, and 188Re in ARO-N tumors were 18.3 +/- 8.7, 14.6 +/- 7.1 and 23.2 +/- 3.5% injected dose per gram (ID/g) at 2 hours postinjection, respectively. Scintigraphic images of tumor bearing mice using 131I, 99mTc, and 188Re allowed clear visualization of ARO-N tumors. In summary, NIS gene transfection to a single anaplastic thyroid cancer cell line efficiently triggered high tumor uptake of radioiodines, 99mTc and 188Re. These results demonstrate the possibility of imaging and therapy using NIS gene transfection in anaplastic thyroid carcinoma, although the short retention time is considered the major impediment to be resolved for the successful implementation.
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PMID:In vitro and in vivo properties of a human anaplastic thyroid carcinoma cell line transfected with the sodium iodide symporter gene. 1567 66

Large cell calcifying Sertoli cell tumors (LCCSCT) are associated with Carney complex and Peutz-Jeghers syndrome. The mechanisms linking these 2 genetic defects to the genesis of this tumor are obscure. Studies of CYP19 (aromatase) and transforming growth factor (TGF)-beta1 messenger RNA (mRNA) abundance, estrogen receptor (ER), TGFbeta1, and TGFbeta type II receptor (R) immunochemistry were carried out in the testis of a patient with this tumor to gain information on possible mechanisms of cell tumor development. Testicular tissue of a prepubertal patient, collected at gonadectomy, was separated into 2 macroscopically distinct fractions: tumoral nodules (Tu) and extratumoral, normal-looking testicular tissue (ExTu). The patient was a 9.5-year-old boy with a 5-year history of bilateral gynecomastia (Tanner stage 4), no pubic hair, incipient genital development, and bilateral testicular nodules. Multiple pigmented lesions of the skin were present. Bilateral mammectomy and gonadectomy was performed. RNA was extracted from Tu and ExTu for semiquantitative reverse transcriptase-polymerase chain reaction of CYP19 and TGFbeta1. Protein expression of ER, TGFbeta1, and TGFbeta type II R in Tu and ExTu was detected by immunohistochemistry. Cell proliferation was estimated by Ki-67 antigen immunochemistry and apoptosis using a modified TUNEL assay. Mean expression of aromatase and TGFbeta1 mRNAs in Tu was 6- and 2.3-fold higher than in ExTu, respectively (P<0.05). Tumoral cells exhibited ER staining with a predominant extranuclear localization. Positive staining of Sertoli cells in Tu was higher than in ExTu. TGFbeta1 immunostaining of the interstitial cells in Tu was higher than in ExTu. TGFbeta type II R immunostaining was detected in most Sertoli and interstitial cells, but intensity in ExTu was lower than in Tu. No significant difference was detected in the proliferation index, but in Tu, the percentage of Sertoli cells in apoptosis (1.4%) was significantly lower (P<0.01) than in ExTu (14.0%). The following hypothesis is proposed. The congenital gene defects of Carney complex or of Peutz-Jeghers syndrome might trigger a cascade of intracellular events that leads to overexpression of aromatase in Sertoli cells, favoring the development of a LCCSCT. At some point in the evolution of the disease, a mutational event might induce a higher expression of the ER. Also, TGFbeta1 protein expression is increased in neighboring cells. In this environment, TGFbeta1 might switch from tumor suppressor to oncogenic factor and, along with estrogen-ER complexes, might favor tumor progression by inhibiting apoptosis.
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PMID:High TGFbeta1, estrogen receptor, and aromatase gene expression in a large cell calcifying sertoli cell tumor (LCCSCT): implications for the mechanism of oncogenesis. 1694 77


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