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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have examined the effect of LH on the regulation of the progesterone receptor (PR) in cultured porcine granulosa cells. In this study we used the RNase protection assay to evaluate the PR mRNA levels with a porcine cDNA clone isolated by the polymerase chain reaction (PCR) method. This clone was regarded as part of the porcine PR cDNA because of its 98.3% and 95.7% homology to the hormone-binding domain of human PR cDNA in amino acid and nucleotide sequences, respectively. Treatment with LH (500 ng/ml) increased porcine PR mRNA to a maximum level of 8.6 +/- 1.1-fold (mean +/- SE) after 3-h exposure. This induction was mimicked by (Bu)2cAMP as well as by FSH and hCG, and the increased PR caused by LH and (Bu)2cAMP occurred in a dose-dependent manner. Basal and LH-induced PR mRNA levels were not affected by progesterone (100 ng/ml), estrogen (100 ng/ml), and RU 486 (10 ng/ml) at 3 h. The mechanism of the increased PR mRNA levels was studied in the presence of actinomycin-D and cycloheximide. While inhibition of RNA synthesis with actinomycin-D blocked LH-induced PR mRNA expression, inhibition of protein synthesis with cycloheximide increased basal and LH-induced PR mRNA levels. These results indicate that the expression of PR mRNA is positively regulated by LH, and this induction does not require ongoing protein synthesis. There may be a cycloheximide-sensitive mechanism that modulates PR mRNA stability. From our results we suspect that progesterone modulates ovarian function through LH-induced PR in granulosa cells.
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PMID:Luteinizing hormone induces progesterone receptor gene expression in cultured porcine granulosa cells. 171 38

This paper addresses the expression of the epidermal growth factor (EGF) gene by human breast tumor biopsy samples. Northern analysis was used to demonstrate the presence of an approximately 5-kilobase mRNA which specifically hybridized with radiolabeled human EGF complementary DNA in some human breast tumor biopsy samples. Quantitation of EGF mRNA in 60 human breast tumor biopsies using the RNase protection assay revealed that 83% of tumors contained detectable EGF mRNA. Estrogen receptor (ER) and progesterone receptor (PgR) mRNAs were similarly quantitated in the same samples. It was found that 89.4% of the ER mRNA-positive breast tumor biopsies had detectable EGF mRNA, whereas only 58.3% of the ER mRNA-negative tumors had detectable EGF mRNA. Furthermore, whereas 90.5% of the PgR mRNA-positive tumors contained EGF mRNA, only 60% of the PgR mRNA-negative tumors contained EGF mRNA. chi 2 analysis indicated that the increased percentage of tumors expressing EGF in the receptor-positive groups was statistically significant (P less than 0.01). It was also found that the mean relative level of EGF mRNA in those tumors which were ER and PgR negative [9.8 +/- 5.6 (SEM) relative units] was significantly lower than those tumors which were ER and PgR positive (40.5 +/- 6.4 relative units, P less than 0.05) or ER positive and PgR negative (68.4 +/- 19.9 relative units, P less than 0.005). These observations suggest that the EGF-expressing tumors probably arose originally from hormonally responsive cell types and that EGF expression in a large proportion of human breast tumors in vivo may also be hormonally responsive.
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PMID:Epidermal growth factor gene expression in human breast cancer biopsy samples: relationship to estrogen and progesterone receptor gene expression. 236 77

The effect of RNase on the transformation of progesterone receptor from rabbit uterus was studied by density-gradient centrifugation and DNA-cellulose binding assay. The 7S form of the receptor in crude cytosol was RNase sensitive, and converted to the 4S form after RNase treatment. This reaction was prevented by an RNase inhibitor and reversed by the addition of ribosomal RNA. RNase treatment also caused a two-fold increase in the DNA binding of cytosolic receptor, and reduced the time required for heat-induced transformation. However, sucrose-gradient-purified progesterone receptor (7S) did not undergo transformation by warming unless exogenous RNase was added, thereby suggesting that a cytosolic factor, which might be endogenous RNase, is necessary for the heat-induced transformation of progesterone receptor. Furthermore, degradation of the receptors which occurred after prolonged warming at 25 degrees C in the presence of RNase could be prevented by the addition of DNA-cellulose to the reaction mixture. These results indicate that RNA is associated with the 7S form of progesterone receptor, and that its hydrolysis by RNase might be involved in the transformation of this receptor.
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PMID:Ribonuclease-induced transformation of progesterone receptor from rabbit uterus. 242 51

Steroid receptors exist in cytosol as 9S, non-DNA-binding species and as 4S (transformed) species that bind to DNA or nuclei. Labeling the progesterone receptor from rabbit uterine cytosol with [3H]progesterone in the presence of 10 mM sodium molybdate revealed a 9S species on sucrose gradient centrifugation. Without molybdate, the receptor sedimented as an intermediate species of 6S, which converted to 4S in 0.3 M NaCl. The 6S species could also be generated from the 4S species by dialysis. Dilution of the same 4S species gave only partial re-aggregation with 50% of the receptor remaining as 4S. Dialysis appeared to retain the association of a macromolecular aggregation factor present in cytosol. Serum did not seem to be the source of the aggregation factor, as perfusion of the uterine vasculature before excision did not affect the S value of the receptor. We tested whether RNA was involved by treating receptor with RNase A (100 micrograms/400 microliters cytosol). While the molybdate-stabilized cytosol receptor (9S) was unaffected, RNase A partially (50%) converted the 6S form of receptor to 4S. RNase A also partially converted the re-aggregated form back to 4S. Protease inhibitors had no effect on this action of RNase. Formation of receptor-ribonucleotide protein particles may play a role in steroid action in the cell.
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PMID:Occurrence of a 6S intermediate form of the progesterone receptor that is sensitive to ribonuclease. 243 71

Much clinical evidence indicates that androgens have beneficial effects in the treatment of breast cancer in women. Physiological concentrations of androgens strongly inhibit both basal and estrogen-induced cell proliferation in the human breast cancer cell line ZR-75-1 through their interaction with the androgen receptor. The present study shows that androgens strongly suppress estrogen receptor (ER) and progesterone receptor contents in this model, as measured by radioligand binding and anti-ER monoclonal antibodies. Similar inhibitory effects are observed on the levels of ER messenger RNA (mRNA) measured by ribonuclease protection assay. The androgenic effect is observed at subnanomolar concentrations of the nonaromatizable androgen 5 alpha-dihydrotestosterone, regardless of the presence of estrogens, and is competitively reversed by the antiandrogen hydroxyflutamide. Such data on ER expression provide an explanation for at least part of the antiestrogenic effects of androgens on breast cancer cell growth and moreover suggest that the specific inhibitory effects of androgen therapy could be additive to the standard treatment limited to blockade of estrogens by antiestrogens.
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PMID:Down-regulation of estrogen receptors by androgens in the ZR-75-1 human breast cancer cell line. 266 Dec 9

It has been reported that the response of target cells to steroid hormone (SH) stimulation may depend on their position in the cell cycle. The DNA and RNA contents of malignant cells of the endometrium cultured in vitro were measured using flow cytometry (FCM). We also measured estrogen receptor (ER) and progesterone receptor (PR) levels of cells at different positions in the cell cycle. The G1 and S phases of the cell cycle were investigated using cells synchronized by sodium n-butyrate (G1 block), methotrexate (S block), and excess thymidine (S block). For DNA measurements, the cells were stained with propidium iodide following RNase treatment. For RNA measurements (double-stranded RNA) the cells were treated with DNase. We found that S phase synchronization by methotrexate was 136.2% of control (100%). Using the excess thymidine block and release procedure, the S phase fraction was 185.1% of control. G1 phase synchronization by sodium n-butyrate was 134% of control. The estrogen receptor level in G1 phase synchronized cells increased to 5.94 fmol/micrograms DNA in the cytosol and 12.35 fmol/micrograms DNA in the nuclear fraction. These levels represent a sevenfold total increase over that of the control estrogen receptor level. Cells in S phase showed no significant increase in estrogen receptor levels over control cells. Based on this study, the functional increase of the steroid receptor was most significant in the G1 phase.
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PMID:Relationship between changes of the steroid receptor and synchronization in human endometrial adenocarcinoma cells in vitro. 320 23

A cell-free system was used to characterize the binding reaction between the progesterone receptor and nuclear acceptor sites prepared from rat placenta. Two forms of receptor-acceptor complex were examined. One was extracted from nuclei by exposure to 0.6 M KCl; the other type was resistant to salt extraction. Kinetic analysis indicated that the binding reactions were saturable (3-4 pmol binding sites/mg DNA) and of high affinity (Kd = 3-6 nM). Acceptor binding was specific for placental nuclei and did not occur with nuclei prepared from spleen or with denatured nuclei from placenta. Acceptor sites were further characterized by their sensitivity to RNase, DNase I, and protease. RNase treatment had no influence on receptor-acceptor binding. However, DNase I reduced the number of KCl-resistant acceptor sites by 41%, but only a 19% reduction occurred in KCl-extractable acceptor sites (P less than 0.05). Protease removed 34% and 48% of the KCl-resistant and -extractable acceptor sites, respectively, and combined treatment with DNase and protease eliminated 76% of acceptor-binding activity. The endogenous inhibitor previously described from rat placental cytosol blocked acceptor-binding sites in a concentration-dependent manner, a decrease of 1.15 pmol sites/mg inhibitor protein for resistant sites and 0.76 pmol/mg inhibitor protein for extractable sites. However, receptor-acceptor binding was not altered by treating nuclei with actinomycin D or chloroquine. Mercurial reagents reduced receptor-acceptor interaction by 80% and 94% in KCl-resistant and -extractable sites, respectively, whereas sulfhydryl alkylating agents reduced binding 35% and 76%. Pyridoxal phosphate destroyed 88-93% of acceptor binding. The results of these studies suggest that the progesterone receptor acceptor sites are composed of a complex of chromatin protein and DNA in rat placenta. Furthermore, the binding reaction requires the participation of sulfhydryl and terminal amino groups.
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PMID:Nuclear acceptor sites for progesterone-receptor complexes in rat placenta. 329 40

The binding of a steroid receptor to specific nuclear sites (i.e., nuclear acceptor sites) represents the immediate event preceding the steroid regulation of gene transcription. How the same steroid receptor regulates different genes in different tissues is unknown. Since a major fraction of the nuclear acceptor sites for a variety of steroid receptors has been reported to be masked in the chromatins of a variety of tissues, the differential expression of the nuclear acceptor sites may explain this regulation of different genes. In the avian oviduct, the removal of a subfraction of chromosomal non-histone proteins, termed CP-2, results in the unmasking of the nuclear acceptor sites for the progesterone receptor (PR). Further, the extent of masking of these nuclear acceptor sites for PR has been reported to vary during cytodifferentiation of the avian oviduct. This paper describes a method for the reconstitution of the masking of PR nuclear acceptor sites in the avian oviduct chromatin using a partially purified chromosomal protein fraction (CP-2b). The reannealling of the CP-2b fraction to unmasked avian oviduct chromatin (termed nucleoacidic protein or NAP) results in the "remasking" of about the same number of nuclear acceptor sites for PR as found in intact chromatin. Because some of the PR acceptor sites on the NAP cannot be remasked, these sites either must be protected from masking or not be recognized by the masking proteins. The masking activity apparently involves only protein(s) because the unmasking of acceptor sites can be achieved with protease but not ribonuclease activities and because the dissociated masking activity is destroyed only by proteases. The masking appears to be reversible because the reconstituted masked sites can again be unmasked. Preliminary purification and characterization of the masking activity in fraction CP-2b by molecular sieve chromatography indicate a heterogeneity of size with the activity eluting in a molecular weight range of from 60 000 to greater than 150 000. Whether the masking proteins prevent the binding of the progesterone receptor by directly binding the acceptor sites or by binding neighboring domains to condense the chromatin is unknown. It is speculated that the masking of acceptor sites may be responsible in part for determining the tissue-specific gene expression induced by steroids and/or may play a role in the unresponsiveness of certain human tumors containing steroid receptors.
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PMID:Proteins that mask the nuclear binding sites of the avian oviduct progesterone receptor. 407 35

The effects of long term treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) on estrogen receptor (ER) expression in the human breast cancer cell line, MCF-7, were studied. This study demonstrates that treatment of cells with the phorbol ester blocked estrogen receptor activity. Treatment of cells with 100 nM TPA resulted in an 80% decrease in the level of ER protein and a parallel decrease in ER mRNA and binding capacity. Following removal of TPA from the medium, the level of ER protein and mRNA returned to control values; however, the receptor failed to bind estradiol. These cells also failed to induce progesterone receptor in response to estradiol. In addition, TPA treatment blocked transcription from an estrogen response element in transient transfection assays and inhibited ER binding to its response element in a DNA mobility shift assay. The estrogen receptor in treated cells was recognized by two monoclonal anti-ER antibodies and was not quantitatively different from ER in control cells. RNase protection analysis failed to detect any qualitative changes in the ER mRNA transcript. Mixing experiments suggest that TPA induces/activates a factor which interacts with the ER to block binding of estradiol. The effects of TPA on ER levels and binding capacity were concentration-dependent. Low concentrations of TPA inhibited estradiol binding without a decrease in the level of protein, whereas higher concentrations were required to decrease the level of ER protein. The effects of TPA appear to be mediated by activation of protein kinase C since the protein kinase C inhibitors, H-7 and bryostatin, block the effects of TPA on estradiol induction of progesterone receptor. TPA treatment had no effect on the level or binding capacity of the glucocorticoid receptor, indicating that the effects are not universal for steroid receptors. These data demonstrate that activation of the protein kinase C signal transduction pathway modulates the estrogen receptor pathway. The long term effect of protein kinase C activation is to inhibit estrogen receptor function through induction/activation of a factor which interacts with the receptor.
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PMID:Effects of 12-O-tetradecanoylphorbol-13-acetate on estrogen receptor activity in MCF-7 cells. 755 63

We have recently shown that oxytocin (OT) is synthesized within human amnion, chorion, and decidua during late gestation. The levels of OT messenger ribonucleic acid (mRNA) increased around the time of parturition, suggesting that locally produced OT may play a role in this poorly understood process. In this report, we present results from investigations into the effects of estrogen and progesterone on the synthesis of OT by human chorio-decidua. Using an in vitro incubation system, estradiol at physiological concentrations more than doubled the concentration of OT mRNA. This was reflected by an increase in the amount of OT peptide secreted into the medium. The increase in OT mRNA was antagonized by tamoxifen, suggesting that the effects were estrogen receptor mediated. Progesterone had no effect on OT mRNA synthesis. Using ribonuclease protection assays, mRNAs for estrogen receptor (ER) and progesterone receptor (PR) were detected in all tissues examined. The highest levels were found in decidua, with lower amounts in chorion and very small amounts in amnion and placenta. This is the same relative tissue distribution that we previously demonstrated for OT mRNA. A single transcript was present for ER, and two transcripts were protected for PR. The concentrations of ER mRNA in chorio-decidua were 3-fold higher in tissues obtained after spontaneous labor onset than in tissues obtained from cesarean section at a similar gestational age but before labor onset. Levels of PR did not change significantly. We conclude that synthesis of OT in human chorio-decidua may be regulated in part by estrogen, and that regulation of ER levels may be an important factor modulating this effect. These data support the hypothesis of a paracrine network within human fetal membranes and decidua that may participate in regulating the timing of human birth.
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PMID:Estrogen stimulates oxytocin gene expression in human chorio-decidua. 785 22


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