Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The presence of estrogens in tumour cells is considered to be a critical factor for the development of the hormone-dependent forms of breast cancer. The last, rate-limiting step of estrogen biosynthesis is controlled by cytochrome P-450 type enzyme complex named aromatase. In the present study we determined and characterized the expression of aromatase mRNA in the breast carcinoma cell lines T47D and MCF-7. The expression was characterized by slot blot hybridization, reverse transcriptase-polymerase chain reaction technique and Northern hybridization analysis. Northern blotting revealed the presence of 4.4 kb and 2.4 kb messengers in both cell lines.
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PMID:Identification of the aromatase in the breast carcinoma cell lines T47D and MCF-7. 801 54

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

The expression of individual xenobiotic-metabolizing cytochrome P450 (CYP) genes in human placenta was studied at the mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR). mRNAs of CYP1A1, CYP2E1, CYP2F1, CYP3A3/4, CYP3A5, and CYP4B1 were detected by RT-PCR, and CYP1A2, CYP2A6/7, CYP2B6/7, CYp2C8-19, CYP2D6, and CYp3A7 were not detected. Several enzyme activity assays and immunoblasts were used to further characterize expression of forms producing detectable mRNA transcripts. The catalytic activities of 7-ethoxycoumarin O-deethylase (ECOD), 7-ethoxyresorufin O-deethylase (EROD) and aryl hydrocarbon hydroxylase (AHH) were substantially increased in response to maternal cigarette smoking, and paralleled the amount of CYP1A1 mRNA and protein. Aromatase activities were slightly lower in placentas exposed to cigarette smoke compared with nonexposed placentas. These data show that several xenobiotic-metabolizing CYP genes are expressed in human placenta at a low level. The significant of such low-level expression is unknown, but it may have local physiological or toxic consequences.
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PMID:Expression of xenobiotic-metabolizing cytochrome P450 forms in human full-term placenta. 861 84

The expression of aromatase was evaluated in 44 ovarian carcinomas, 7 carcinomas of low malignant potential (LMP), and 14 benign adenomas. Aromatase immunoreactivity was observed in stromal cells in 35 of 44 (79.5%) ovarian carcinomas and 3 of 7 carcinomas of LMP. However, no immunoreactivity was pronounced at sites of frank invasion in ovarian carcinoma. To characterize aromatase in ovarian carcinoma, aromatase activity, mRNA expression, and alternative uses of exon 1 were determined. Quantitation of aromatase activity with the tritiated water method demonstrated 41.62 +/- 9.15 pmol/hour/mg protein in 11 ovarian carcinomas. The mean concentration of aromatase mRNA for 14 ovarian carcinomas was 3 +/- 4 amol/ng RNA, which significantly correlated with aromatase immunoreactivity. The alternative use of multiple copies of exon 1 was examined by reverse transcriptase polymerase chain reaction in 11 carcinomas. The transcript, mainly using exons 1c and 1d, was detected in 4 and 5 cases of carcinoma, respectively. Patterns of utilization of exon 1, however, did not significantly correlate with aromatase overexpression. These results suggest that aromatase is expressed in stromal cells of ovarian carcinoma but not in benign ovarian neoplasms. Increased aromatase expression in stromal cells of human ovarian carcinoma is, therefore, considered to play an important role in the biological behavior of these tumors by producing estrogens in situ as in other female sex-steroid-dependent neoplasms.
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PMID:Aromatase in human common epithelial ovarian neoplasms. 868 61

In pregnant mares, eCG stimulates luteal androgen and estrogen production, increasing plasma concentrations 2- to 3-fold. To study how these changes are regulated, we examined the expression of mRNA for the steroidogenic enzymes 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), cytochrome P450 17 alpha-hydroxylase/17,20-lyase (P450 17 alpha), and cytochrome P450 aromatase (P450arom) in equine primary corpora lutea using Northern blot analyses. Three equine specific cDNAs were generated by reverse transcriptase polymerase chain reaction. When compared to human, bovine, and rat sequences, the nucleotide identities were 82%, 84%, and 76%, respectively, for 3 beta-HSD cDNA (843 base pairs [bp]); 79%, 80% and 66% for P450(17) alpha cDNA (541 bp); and 80%, 83% and 75% for P450arom cDNA (289 bp). The P450(17) alpha cDNA sequence demonstrated 99.6% nucleotide identity with the previously published sequence for equine testicular P450(17) alpha. Luteal tissue samples were collected at three times: diestrus (Days 8-10), early pregnancy before the onset of eCG secretion (Days 29-35), and early pregnancy after the onset of eCG secretion (Days 42-45). Although no significant changes were observed in 3 beta-HSD expression, P450(17) alpha and P450arom demonstrated stage-specific transcriptional regulation. Steady-state levels of P450(17) alpha mRNA were similar during diestrus and early pregnancy before the onset of eCG secretion but increased significantly after the onset of eCG secretion. Cytochrome P450arom mRNA levels decreased significantly after the onset of eCG secretion. Steady-state levels of P450arom mRNA were highest in luteal tissue collected during pregnancy before the onset of eCG secretion and intermediate during diestrus. Secretion of eCG appears to increase luteal estrogen synthesis by a transcriptional up-regulation of P450(17) alpha expression. These data suggest that availability of aromatizable androgens may be rate-limiting in luteal estrogen synthesis before the onset of eCG secretion.
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PMID:Differential transcription of steroidogenic enzymes in the equine primary corpus luteum during diestrus and early pregnancy. 909 61

Peripheral aromatization of androgens exert estrogenic actions in many tissues. Recently in situ production of estrogens by aromatase was detected in human bone and cultured osteoblasts and has been proposed to participate in the maintenance of bone mass. We examined aromatase expression by immunohistochemistry and mRNA in situ hybridization in 16 cases of tibia (female 2 male, 14 female, 62 +/- 5.2 years old) and quantified the level of aromatase mRNA in 28 cases of rib, femur, and lumbar vertebrae (16 male, 12 female, 58.0 +/- 11.3 years old) by reverse transcriptase-polymerase chain reaction (RT-PCR) in order to study whether or not and in which cell types aromatase was expressed in human bone tissues. We also studied alternative use of multiple exons 1 of its gene and immunolocalization of type I 17 beta-hydroxysteroid dehydrogenase (HSD), which converts estrone produced by aromatase to estradiol. Strong aromatase immunoreactivity and mRNA hybridization as well as type I 17 beta-HSD immunoreactivity were detected in lining cells, osteoblasts, chondrocytes of articular cartilage, and adipocytes adjacent to bone trabeculae in all the cases examined. Amounts of aromatase mRNA varied greatly among the subjects (11.25 +/- 9.77, 0.61-42.84 attomol/ng of total RNA). The amount of aromatase expression was not correlated with age or gender of the subjects but positively correlated with the degree of osteroporotic changes evaluated by radiological findings of lumbar vertebrae. Analysis of multiple exons 1 revealed that 1b or fibroblast type was predominantly (23/26) utilized as a promoter of aromatase gene expression. These results demonstrated that aromatase is expressed widely in human bone tissue and may play important roles in maintenance of human bone tissue.
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PMID:Aromatase in human bone tissue. 928 57

In fibroblasts derived from human adipose tissue, aromatase induction is observed after exposure to 1 microM cortisol in the presence of serum or platelet-derived growth factor (PDGF). Progesterone suppresses this induction in a dose-dependent manner, 10 microM resulting in complete inhibition. A reduced cortisol concentration (0.1 microM) concomitantly reduces the progesterone concentration required for effective inhibition (10-100 nM). This effect of progesterone is specific, as neither the release of cellular enzymes nor aromatase induction by dibutyryl-cAMP, which acts independently from cortisol, are affected. However, the inhibitory effect of progesterone requires its presence throughout the induction period. Kinetic studies in intact cells reveal a reduced number of aromatase active sites upon progesterone treatment, whereas progesterone at near-physiological concentration (100 nM) does not inhibit aromatase activity in isolated microsomes. Semi-quantitative reverse transcriptase PCR analysis shows reduced amounts of aromatase mRNA in progesterone-treated cells, indicating specific inhibition of the glucocorticoid-dependent pathway of aromatase induction. The inhibitory effect of progesterone is not blocked by the anti-progestin ZK114043, excluding action via progesterone receptors and indicating competition for the glucocorticoid receptor. Progesterone must be considered a potential physiological inhibitor of glucocorticoid-dependent aromatase induction in adipose tissue. It is proposed that it is a suppressor of aromatase induction in adipose tissue in premenopausal women.
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PMID:Progesterone inhibits glucocorticoid-dependent aromatase induction in human adipose fibroblasts. 984 69

Among sex steroids, especially estrogen metabolism has been considered to play a role in the function and pathology of human veins. We investigated the expression and activity of the estrogen-producing enzyme aromatase and estrogen receptor (ER) in human vena cava to assess possible in situ biosynthesis of estrogens and their modes of action. We first examined aromatase expression by immunohistochemistry in human inferior vena cava obtained from 29 autopsy cases (11 males, 18 females, 63.6 +/- 3.0 years old). We then semiquantitated the level of aromatase mRNA by reverse transcriptase-polymerase chain reaction in 24 cases and aromatase activity by 3H-water assay in 15 cases to examine whether or not and in which cell types aromatase was expressed. We also studied alternative use of multiple exon 1s of its gene and immunolocalization of 17beta-hydroxysteroid dehydrogenase type I (17beta-HSD I), which converts estrone produced by aromatase to estradiol, a biologically active estrogen and ER. Aromatase and 17beta-HSD I immunoreactivity were both detected in smooth muscle cells (SMC) of the media in all the cases and in endothelial cells (EC) in 20 and 22 cases, respectively. ER immunoreactivity was detected in SMC of vena cava in 21 cases. The amount of aromatase mRNA was significantly greater in the cases utilizing 1c (I.3) or 1d (P.II) of exon 1 (9 cases, 191.1 +/- 26.3 attomol/ng total RNA) than those utilizing 1b (I.4) as the promoter (14 cases, 50.6 +/- 13.0 attomol/ng total RNA) (p < 0.01). Significant correlation (p < 0.05) was observed between the amount of aromatase mRNA and aromatase activity in 15 cases examined. No significant correlation was detected between the amount of aromatase mRNA or aromatase labeling index and the ER status. These results suggest that estrone and estradiol are produced in the human vena cava and that their production is mediated by aromatase and 17beta-HSD I, respectively but not all of these locally synthesized estrogens may not work directly in situ.
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PMID:Aromatase and sex steroid receptors in human vena cava. 1046 7

Aromatase (P450AROM) is the enzyme complex with converts testosterone to estradiol and androstendione to estrone. This enzyme was detected in various normal tissues and uterine pathology such as uterine myoma, endometrial cancer and endometriosis. The aim of the study was to estimate expression of P450AROM messenger ribonucleic acid (mRNA) in normal, hyperplastic and malignant endometrium, and the ability to convert androstenedione to estrone by endometrial cancer tissue. Normal endometrium was obtained from 16 (12 proliferative phase, 4 secretory phase) regularly cycling women after hysterectomy for myomas, hyperplastic endometrium (n = 5) and endometrial cancer (n = 5) from postmenopausal women. The ability to convert androstenedione to estrone was estimated in 16 cases of endometrial cancer in postmenopausal women. P450AROM mRNA was measured by a quantitative assay based on reverse transcribing the mRNA into cDNA with reverse transcriptase (RT) then amplification of the cDNA using the polymerase chain reaction (PCR). The mean (+/- SEM) expression of aromatase gene in proliferative endometrium was 84.4 +/- 14.0 pg mRNA/microgram DNA and in secretory endometrium 200.3 +/- 87.8 pg mRNA/microgram DNA. The mean (+/- SEM) P450AROM mRNA expression in endometrial hyperplasia was 92.9 +/- 17.8 pg mRNA/microgram DNA, in endometrial cancer was 14.3 +/- 7.7 pg mRNA/microgram DNA. Androstenedione to estrone conversion in endometrial cancer tissue culture was 252.5 +/- 91 fmol/g tissue/h. Our data confirm that human normal, hyperplastic and malignant endometrium do express P450AROM mRNA and that aromatase activity is present in endometrial cancer tissue.
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PMID:[Aromatase (P450AROM) mRNA expression in normal, hyperplastic and malignant endometrium and aromatase activity in endometrial cancer tissue culture]. 1084 13

Estrogen plays an important role during brain development interfering with the maturation of distinct neural systems and, in particular, with the sexual differentiation of brain structures and function. Similar to other brain regions, estrogen is known to influence neuronal differentiation and plasticity in the hippocampus. The present study is concerned with the developmental expression of mRNAs for the estrogen-synthesizing enzyme aromatase and the two known nuclear estrogen receptors (alpha/beta) in the male and female mouse hippocampus. Using semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis, we found that aromatase as well as estrogen receptors (alpha/beta) are already expressed prenatally in the hippocampus of both sexes. Aromatase expression increased during the first two postnatal weeks and decreased, thereafter, to lower levels in adults. Sex differences in aromatase expression were observed postnatally with higher levels in males. Estrogen receptor-alpha/beta mRNAs did not fluctuate obviously throughout pre- and postnatal development but revealed a distinct sex-specific pattern at the end of the first postnatal week. Again, higher expression was detected in males. These findings clearly demonstrate the capacity of estrogen formation and the presence of both estrogen receptor subtypes in the developing hippocampus. Sex differences in aromatase mRNA levels paralleled the sex-specific pattern of estrogen receptor expression. Thus, our data support the idea that the developing hippocampus is a target for estrogen action and estrogen receptor-mediated sexual differentiation.
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PMID:Ontogenetic expression and sex differences of aromatase and estrogen receptor-alpha/beta mRNA in the mouse hippocampus. 1086 19


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