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)

Progesterone (P) is known to regulate sex steroid receptors in uterine cells. However, its precise regulation at the messenger ribonucleic acid (mRNA) level is unclear. In this study we examined the effects of P and testosterone (T) on the regulation of sex steroid receptors in cultured human endometrial stromal cells (ESC), using the quantitative reverse transcriptase polymerase chain reaction method. We isolated ESC from human endometrial tissues and cultured them with or without P (10(-6) mol/L) or T (10(-8) mol/L) for 9 days. Incubation with P decreased progesterone receptor (PR), estrogen receptor, and androgen receptor mRNA levels in cultured human ESC to 0.56 +/- 0.04-, 0.53 +/- 0.08-, and 0.84 +/- 0.04-fold (mean +/- SE), respectively. T also decreased PR, estrogen receptor, and androgen receptor mRNA levels in cultured human ESC to 0.48 +/- 0.06-, 0.52 +/- 0.05-, and 0.82 +/- 0.04-fold (mean +/- SE), respectively. These decreases by P and T occurred in a dose-dependent manner. We also examined the sex steroid receptor levels in human ESC cultured for 0, 3, 6, and 9 days. The PR mRNA level in ESC without P was increased in a time-dependent manner. This increase was also inhibited by P, and the mRNA level in the presence of P was almost constant throughout the culture period. Our results demonstrated that P or T is a regulator of sex steroid receptors in ESC and that this regulation may influence the responsiveness to P of decidual change in ESC.
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PMID:Regulation of sex steroid receptor gene expression by progesterone and testosterone in cultured human endometrial stromal cells. 785 3

Expression of progesterone receptors (PR) was studied in human osteoblast-like cell lines and primary human osteoblast cultures at the molecular level. Using the sensitive reverse transcriptase polymerase chain reaction (RT-PCR) and oligonucleotide primers which flank the progesterone-binding domain of human PR, progesterone receptor (PR) mRNA was detected in three osteoblast-like cell lines--HOS-TE85, MG-63, and SAOS-2. When compared with beta-actin gene expression, levels of PRmRNA transcripts varied between cell lines (PRmRNA in HOS-TE85 > MG-63 >> SAOS-2). In addition, RT-PCR confirmed the presence of PRmRNA transcripts in primary human osteoblast cells cultured from collagenase-treated bone. Immunostaining was used to visualize PR protein in cells. All osteoblast-like cell lines showed specific staining for PR. Immunoreactivity was distributed equally in the nucleus and cytoplasm. The level of staining was significantly lower than that detected in PR-positive MCF-7 breast cancer cells though well above background levels obtained for PR-negative HeLa cells. The finding that PR is expressed at both the level of mRNA and protein in several osteoblast-like cell lines as well as in human primary osteoblast cultures indicates that bone-forming osteoblast cells are direct targets for progesterone action.
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PMID:Progesterone receptors are expressed in human osteoblast-like cell lines and in primary human osteoblast cultures. 858 76

We employed homologous recombination in mouse embryonic stem cells to disrupt the estrogen receptor (ER) gene. Subsequently generated mice that are homozygous for the gene disruption, termed ERKO, possess no demonstrable wild-type ER by Western blot analysis. However, the presence of residual high affinity binding, as detected by [3H]estradiol binding assays and sucrose gradients in uterine extracts from ERKO females prompted further investigation of transcription and translation products from the disrupted ER gene. Analysis of ERKO uterine messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction demonstrated that although no full-length wild-type ER mRNA was present, two smaller transcripts, labeled E1 and E2, were identified and partially sequenced. Both ERKO transcripts are splicing variants that result in the disrupting NEO sequence being partially or completely removed from the mRNA. In the ERKO-E2 variant, this results in a frame shift and the creation of at least two stop codons downstream. In the ERKO-E1 variant, the ER reading frame is preserved and encodes for a smaller mutant ER that could be the source of the residual estradiol binding. When this mutant form is overexpressed and characterized in vitro, it results in a smaller protein of the predicted size that possesses significantly reduced estrogen-dependent transcriptional activity compared with that of the wild-type ER. Despite residual amounts of an impaired ER variant, estrogen insensitivity in the female ERKOs was confirmed by the failure of estrogen treatment to induce known uterine markers of estrogen action, such as increased DNA synthesis, and transcription of the progesterone receptor, lactoferrin, and glucose-6-phosphate dehydrogenase genes. Furthermore, serum levels of estradiol in the ERKO female are more than 10-fold higher than those in the wild type, consistent with a syndrome of hormone insensitivity.
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PMID:Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene. 858 21

In normal estrogen target tissues, estrogen action is mediated through a specific nuclear transcription factor, the estrogen receptor (ER). The site of estrogen action in the developing organism is therefore determined by cells that contain ER and other necessary tissue and gene-specific components for estrogen-mediated transcription. Immunocytochemical methods were used to determine the cellular localization and tissue distribution of ERs in reproductive tracts of mouse fetuses. Nuclear staining for ER was observed in reproductive tracts at fetal days 13 to 15. ERs were present in the precursors of both male and female reproductive tracts at these early developmental stages, which may be attributable to their similar embryonic origins. However, as the tissues undergo sexual differentiation at later fetal and early neonatal ages, ER increases in the female reproductive tracts as compared with the male. ER was detected by immunoblotting on fetal day 10 (before sexual differentiation) in extracts of whole mouse embryos. To determine whether ER and progesterone receptor genes are expressed earlier in development, we examined RNA from preimplantation mouse embryos using reverse transcriptase-polymerase chain reaction techniques. ER mRNA was found in oocytes and fertilized eggs. Message concentration declined at the 2-cell stage and reached its lowest level at the 5- to 8-cell stage. ER mRNA was not detectable at the morula stage but reappeared at the blastocyst stage. Progesterone receptor mRNA was not detectable until the blastocyst stage. The embryonic expression of ER and progesterone receptor genes in the blastocyst suggests a possible functional requirement for estrogen and progesterone receptors in preimplantation embryos.
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PMID:Embryonic estrogen receptors: do they have a physiological function? 859 78

The human endometrium undergoes regular cyclical changes under the endocrine control of oestrogens and progesterone acting via specific nuclear receptors. The molecular and cellular events mediating these changes are not understood. The present study examined the changes in the endometrial progesterone receptor and its mRNA during the menstrual cycle. Forty-four endometrial samples obtained from women with normal menstrual cycles were divided into four categories: early proliferative (days 6-9), late proliferative (days 10-14), early secretory (days 15-21) and late secretory (days 22-28). The progesterone receptor protein was determined using a human progesterone receptor enzyme-linked immunoassay kit. Total RNA was extracted using RNAzol and the abundance of mRNA encoding the progesterone receptor was determined by reverse transcriptase-polymerase chain reaction and by northern blot analysis. The concentration of the progesterone receptor in the endometrium was highest during the late proliferative phase and was lowest in the late secretory phase. Significant differences were observed between the menstrual cycle phases (P < 0.003). No cyclical variation was observed in the concentration of mRNA encoding for the progesterone receptor in the endometrium when analysed by reverse transcriptase polymerase chain reaction or by northern analysis. There appears to be no association between the amounts of mRNA encoding the progesterone receptor and progesterone receptor protein during the menstrual cycle suggesting that the control of the expression of the progesterone receptor may not occur solely at the transcriptional level.
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PMID:Endometrial progesterone receptor expression during the human menstrual cycle. 866 43

Progesterone is a known immunosupressant in humans and may be important in treatment regimens for women with immunological and endocrinological reproductive failure. The molecular mechanism of progesterone-mediated immunosuppression remains controversial. We used the reverse transcriptase polymerase chain reaction (RT-PCR) technique to detect progesterone receptor RNA in human peripheral blood mononuclear cells (PBMCs). No expression could be documented in PBMCs from men or women representing various reproductive states. We also used the glucocorticoid receptor antagonist RU 43044 to address the hypothesis that progesterone exerts immunomodulatory effects via interactions with the glucocorticoid receptor. Both hydrocortisone (10(-6) and 10(-7) M) and progesterone (10(-5), 10(-6) and 10(-7) M) inhibited phytohaemagglutinin-induced lymphocyte proliferation in a dose-dependent fashion. RU 43044 (10(-5) M) significantly reversed the immunosuppressive effect od hydrocortisone but not that of progesterone. These studies indicate that human PBMCs do not express the classical progesterone receptor. Our results further suggest that progesterone does not mediate its immunomodulatory effects via interaction with the glucocorticoid receptor. Interaction with other members of the steroid and thyroid hormone receptor superfamily, local conversion to other steroid substances or non-classical receptor-mediated mechanisms may be involved.
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PMID:Progesterone-induced immunosuppression is not mediated through the progesterone receptor. 913 Jul 72

Steroids have the ability to alter adipose tissue distribution. Controversy exists as to whether these effects of sex hormones (oestrogen, progesterone and testosterone) on human adipose tissue are indirect or direct, as only very few studies have focused on steroid receptor status in human adipose tissue. In the present study, we reinvestigated steroid receptor status in human mature adipose tissue and human preadipocytes. Oestrogen, glucocorticoid and androgen receptors were found in human mature adipocytes from both women and men. The receptors were detected by ligand binding. Furthermore, the existence of the receptors was confirmed by demonstrating that adipocytes contained mRNA encoding the receptors. cDNA was generated using reverse transcriptase (RT) followed by polymerase chain reaction (PCR) amplification using specific primers (RT-PCR) for the specific steroid receptors. Adipocytes did not contain mRNA encoding the progesterone receptor (PR), and no progesterone binding was detectable in human adipocytes. Human preadipocytes contained glucocorticoid receptor (GR) mRNA and androgen receptor (AR) mRNA, whereas we were unable to detect oestrogen receptor (ER) mRNA and progesterone mRNA in human preadipocytes. In conclusion, oestrogen glucocorticoid and androgen receptors are present in mature adipocytes from subjects of both sexes, whereas adipocytes do not contain progesterone receptors. In preadipocytes, only glucocorticoid receptors and androgen receptors are present, whereas oestrogen receptors and progesterone receptors are not present.
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PMID:Identification of steroid receptors in human adipose tissue. 901 78

A variant form of the human oestrogen receptor (ER) mRNA lacking sequences encoded within exon 5 has been described (Fuqua SAW, Fitzgerald SD, Chamness GC, Tandon AK, McDonnell DP, Nawaz Z, O'Malloy BW, McGuire WL 1991, Cancer Res 51: 105-109). We have examined the expression of the exon 5-deleted ER (HE delta5) mRNA variant in breast biopsies using reverse transcriptase polymerase chain reaction (RT - PCR). HE delta5 mRNA was present in only 13% of non-malignant breast tissues compared with 32% of carcinomas (95% CI, P=0.05). Presence of the HE delta5 mRNA was associated with the presence of immunohistochemically detected ER (P=0.015) and progesterone receptor (PR) (P=0.02). There was a positive correlation between the presence of HE delta5 and disease-free survival (P=0.05), suggesting that the presence of HE delta5 may be an indicator of better prognosis. We have raised a monoclonal antibody specific to the C-terminal amino acids of HE delta5. This antibody recognized the variant but not the wild-type ER protein. We show that HE delta5 protein is present in breast cancer using immunohistochemical techniques. We also analysed trans-activation by HE delta5 in mammalian cells and showed that, in MCF-7 cells, HE delta5 competes with wild-type ER to inhibit ERE-dependent trans-activation. Our results indicate that this variant is unlikely to be responsible for endocrine resistance of breast cancer, but its presence at both the mRNA and protein level suggest that it may, nevertheless, be involved in regulating the expression of oestrogen-responsive genes in breast cancer.
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PMID:Presence of exon 5-deleted oestrogen receptor in human breast cancer: functional analysis and clinical significance. 909 67

As the size of breast tumors continues to decrease, it has become more difficult to obtain adequate tumor tissue for molecular studies. We have used the estrogen receptor (ER) gene as a model to study the ability to perform a quantitative analysis of ER mRNA extracted from archival breast carcinoma specimens using reverse transcriptase polymerase chain reaction. Based upon ER mRNA abundance, tumors were characterized as having low, medium, or high ER mRNA expression. These data were compared with ER and progesterone receptor (PR) status determined by enzyme immunoassay, tumor histology, and Bloom-Richardson grade. Comparing the low and high ER mRNA groups, there were statistically significant differences in ER-positive status (10% versus 95%; P = 0.0001), PR-positive status (10% versus 90%; P = 0.0001), and tumor grade (2.67 +/- 0.12 versus 2.09 +/- 0.14; P = 0.0025). Of the 28 tumors in the high ER mRNA group, 5 (18%) were invasive lobular carcinomas whereas all 24 tumors with low ER mRNA were invasive ductal carcinomas. These data demonstrate that archival breast tumor specimens can be characterized for ER mRNA abundance. In addition, we conclude that the mechanisms regulating ER gene transcription influence the phenotype of breast carcinomas. These results also suggest that this technique can be designed to provide a quantitative analysis of gene expression for any gene of interest utilizing archival tumor specimens.
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PMID:Analysis of estrogen receptor messenger RNA in breast carcinomas from archival specimens is predictive of tumor biology. 913 83

The growth regulatory effects of PRL on the human breast are mediated by its receptor (PRLr), a member of the cytokine receptor family. Recent reverse transcriptase-PCR studies by our laboratory and others have shown PRL expression within breast tissues at the RNA level. To confirm the role of this growth factor-receptor complex in normal and malignant breast tissues, the expression of PRL and PRLr was examined in parallel with the estrogen receptor (ER) and progesterone receptor (PR). Sixty-nine cases of primary invasive breast carcinoma were examined for PRL and PRLr expression by in situ hybridization and immunohistochemical technique, respectively. These data revealed widespread expression of PRL and its receptor in the breast cancers studied (>95%) and in the normal breast tissues (>93%), with no association between the expression of PRL-PRLr and ER or PR. These findings stand in contrast to prior RIA-based studies that detected the PRLr in only 20-60% of breast carcinomas, most commonly in ER-PR-positive cells. These results confirm prior data indicating the presence of an autocrine/paracrine loop for the PRL-PRLr complex within human breast tissues. Given the widespread expression of PRL-PRLr in breast cancer, pharmacological interventions aimed at the inhibition of function of this growth regulatory receptor complex may be of considerable utility in the therapy of this disease.
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PMID:Expression of prolactin and its receptor in human breast carcinoma. 938 44


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