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)

Recent evidence suggests that the expression of estrogen receptor (ER) variants in breast cancer may interfere with wild-type (wt) ER function and be related to tumor progression and resistance to hormone treatment. One of these variants, ER delta E5, lacking that part of the hormone-binding domain encoded by exon 5, has previously been identified in breast tumors with the unusual estrogen receptor negative (ER-) and progesterone receptor positive (PgR+) phenotype and found to possess constitutive and hormone-independent transcriptional activity. Using a ribonuclease protection assay, we analyzed 27 breast tumors and 4 breast cell lines for the presence of this variant. We found the ER delta E5 variant to be expressed, not only in all of three ER-/PgR+ tumors but also in 19 of 20 ER+/PgR+ or ER+/PgR- tumors. Moreover, the variant was always coexpressed with and often in excess of wtER. ER delta E5 was also found in three breast cancer cell lines (MCF7, T47D, and ZR75-1), although to a lesser extent than wtER. A complete absence of both ER delta E5 and wtER was noted in four ER-/PgR- tumors and one normal breast cell line (HBL-100). Thus, our data suggest that the occurrence of ER delta E5 in breast cancer may represent a critical stage in tumor progression to autonomy.
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PMID:An exon 5 deletion variant of the estrogen receptor frequently coexpressed with wild-type estrogen receptor in human breast cancer. 826 97

Estrogen receptor (ER) expression by breast tumors is an important predictor of disease-free survival in breast cancer patients and, more importantly, is a strong predictor of response to endocrine therapy. Variant forms of the ER may play an important role in the loss of hormone responsiveness and the progression to hormone independence. We have examined a panel of human breast tumor cell lines, both ER-positive and ER-negative, and have identified an ER mRNA variant containing a deletion of exon 5 in the ER-negative BT-20 and ER-positive MCF-7 cell lines. This exon 5 deletion variant has been previously reported to be overexpressed in ER-negative/progesterone receptor-positive breast tumors. Using RNase protection analysis, we have found that the predominant ER transcript in the BT-20 cells is the exon 5 deletion variant, while the principal transcript in MCF-7 cells is the wild-type ER mRNA. The variant ER transcript is translated into a truncated receptor protein of approximately M(r) 42,000 when expressed in yeast and, more important, in breast tumor cells. This is the first demonstration of an exon 5 deletion variant ER protein. Functional analysis has shown that this variant ER possesses constitutive transcriptional regulatory activity with respect to an estrogen-regulated reporter gene construct in a yeast expression system. The presence of this ER variant in breast tumor cell lines, as well as breast tumor biopsies and uterine tissue, suggests that it is a naturally occurring variant that may arise by alternative splicing, and whose overexpression may be involved in the progression of breast tumors to a hormone-independent state.
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PMID:Expression of a constitutively active estrogen receptor variant in the estrogen receptor-negative BT-20 human breast cancer cell line. 826 6

Mechanisms regulating responses of the ovine uterus to endocrine and paracrine signals during the estrous cycle and pregnancy are likely to require tissue- and cell-specific regulation of steroid hormone receptor gene expression. To determine effects of day and pregnancy status (cyclic or pregnant) on uterine estrogen receptor (ER) and progesterone receptor (PR) gene expression, ewes were hysterectomized either on Day 1 (Day 0 = estrus/mating), 6, 11, 13, or 15 of the estrous cycle (n = 3/day) or on Day 11, 13, 15, 17, or 25 of early pregnancy (n = 5/day). Steady state levels of ER and PR mRNA were determined in endometrial and myometrial tissues by slot-blot hybridization and ribonuclease protection assays, respectively, using homologous ovine ER and PR cRNA probes. Changes in spatial expression of ER and PR mRNA and protein in uterine tissue sections were determined by in situ hybridization and immunocytochemical analyses. In cyclic ewes, steady state levels of endometrial ER mRNA were highest on Day 1, declined between Days 1 and 6, and increased between Days 11 and 15. However in pregnant ewes, endometrial ER mRNA levels decreased between Days 11 and 15 and increased slightly between Days 15 and 25. In cyclic ewes, levels of myometrial ER mRNA were highest on Day 1, decreased to Day 6, and remained low thereafter. In cyclic ewes, endometrial PR mRNA levels were highest on Day 1, decreased between Days 1 and 11, and then increased between Days 13 and 15. In cyclic ewes, myometrial PR mRNA levels were highest on Day 1 and declined thereafter. Endometrial PR mRNA levels were not different between cyclic and pregnant ewes on Days 11, 13, and 15. In pregnant ewes, PR mRNA levels were low on Day 11, increased between Days 11 and 17, and decreased between Days 17 and 25. In pregnant ewes, myometrial PR mRNA levels were low and did not change between Days 11 and 25. In situ hybridization and immunocytochemical analyses revealed distinct tissue- and cell type-specific alterations in uterine ER and PR mRNA and protein expression during the estrous cycle and early pregnancy that generally paralleled overall changes in steady state levels of ER and PR mRNAs. In the endometrium, the most striking observation was that PR mRNA and protein expression disappeared from the luminal and shallow glandular epithelium between Days 6 and 13 of the estrous cycle, whereas ER mRNA and protein expression was low on Days 6 and 11 and increased between Days 11 and 15 in the luminal and shallow glandular epithelium. During early pregnancy, expression of ER and PR mRNAs, as well as ER and PR protein, was very low or absent in the luminal and shallow glandular epithelium between Days 13 and 25 of pregnancy. Moreover, ER and PR mRNA and protein were consistently present at low levels in the stroma and deep glandular epithelium in both cyclic (Days 11-15) and pregnant (Days 11-25) ewes. Collectively, results suggest that uterine ER and PR gene expression is regulated in a tissue- and cell type-specific manner during the estrous cycle and early pregnancy.
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PMID:Temporal and spatial alterations in uterine estrogen receptor and progesterone receptor gene expression during the estrous cycle and early pregnancy in the ewe. 856 11

Several studies in the past few years have supported the hypothesis that oxytocin (OT) is synthesized in a paracrine system within the pregnant human uterus and that this paracrine system may be an important regulator of the timing of human parturition. Using ribonuclease protection assays, we have demonstrated a three-fold increase in the rate of synthesis of OT mRNA in human decidua around the time of parturition. We also have shown that a similar increase in OT mRNA and peptide synthesis can be stimulated in vitro by physiological concentrations of estradiol. This increase is inhibited by concomitant use of the estrogen receptor (ER) blocker tamoxifen or by transcription inhibitors. Progesterone had little, if any effect. We also detected mRNAs for ER and progesterone receptor (PR) in amnion, chorion and decidua with the same relative tissue concentrations as OT mRNA. The concentrations of ER but not PR increased significantly around the time of labour onset. To determine if local OT concentrations may be regulated by changes in OT metabolism, we determined kinetic parameters for OT metabolism in decidua, chorion and placenta. [3H]tyrosyl-OT was used as substrate. Metabolites were separated using HPLC and identified using amino acid analysis and mass spectrometry. Metabolism in decidua and chorion occurred predominantly via a cytosolic post-proline endopeptidase and the activity was comparable to placenta. In microsomal fractions, cystine aminopeptidase activity predominated and placenta had significantly more activity than decidua and chorion. There were no changes in any Km or apparent vmax values around the time of parturition. These findings support the existence of a paracrine system within human decidua that involves sex steroids regulating synthesis of OT and that undergoes significant changes around the time of parturition. Changes in local OT concentrations are controlled by rates of synthesis rather than rates of metabolism.
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PMID:Synthesis and metabolism of oxytocin in late gestation in human decidua. 871 92

Previous studies in our laboratory indicated that the midcycle gonadotropin surge stimulates progesterone receptor (PR) expression in granulosa cells of the macaque preovulatory follicle. The current experiments were designed to determine whether gonadotropin or steroids continue to regulate PR in luteinized granulosa cells that contain these receptors after the LH surge. Luteinizing granulosa cells obtained from gonadotropin-treated rhesus macaques were cultured in chemically defined medium in the presence of low density lipoprotein (LDL; 100 micrograms/ml) with or without hCG (100 ng/ml) for up to 4 days. Cells were also cultured with various concentrations (0.25-250 ng/ml) of the 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) inhibitor trilostane to reduce progesterone (P) production in vitro. P and estradiol (E) in the media were assayed by RIA; PR mRNA was assessed by RNase protection assay, and cells expressing PR were identified by immunocytochemistry. Whereas hCG stimulated cellular P production through 4 days of culture, trilostane reduced hCG-stimulated P production in a dose-dependent fashion, with P levels decreasing more than 90% during incubation with 250 mg/ml trilostane (p < 0.05). When trilostane was removed from the media, P production returned to hCG-stimulated levels, indicating that trilostane (250 ng/ml) alone did not alter levels compared to those in controls. Before culture, 68 +/- 11% of luteinizing granulosa cells expressed PR; intense nuclear staining was typically observed. After 2 days of culture, 78 +/- 3% of cells remained PR-positive, but nuclear staining was more heterogeneous. Incubation with hCG did not alter the percentage of luteinized granulosa cells staining positive for PR but increased the intensity of PR staining. Trilostane treatment (25 ng/ml) in combination with hCG significantly reduced the percentage of PR-positive cells (54 +/- 9%) when compared with hCG treatment (83 +/- 2%, p < 0.05). These in vitro data suggest that macaque luteinized granulosa cells retain some PR expression in the absence of luteotropic hormones, but that gonadotropin stimulates PR mRNA levels and enhances PR expression as assessed by intensity of nuclear PR staining. In the presence of gonadotropin, trilostane effectively inhibited P production ad reduced the number of PR-positive cells, suggesting that P or a metabolite modulates PR expression in primate luteinized granulosa cells.
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PMID:Progesterone receptor messenger ribonucleic acid and protein in luteinized granulosa cells of rhesus monkeys are regulated in vitro by gonadotropins and steroids. 892 10

The two forms of the progesterone receptor, PR-A and PR-B, are independently regulated at the transcriptional level, and show distinct responses to progesterone antagonists. We were interested in possible differences in the PR-A to PR-B ratio between uterine myometrium and leiomyomata (fibroid), that might influence the response of fibroids to progesterone agonists and antagonists, and thus have consequences for the treatment of this condition. Fibroid and adjacent normal myometrium were obtained from 11 women undergoing hysterectomy. Immunohistochemistry using a monoclonal antibody which recognizes both PR-A and PR-B showed exclusively nuclear staining, and this was stronger in the leiomyomata than in adjacent myometrium. An antibody specific for PR-B gave fainter staining of both tissues. Western blotting confirmed a higher concentration of PR in leiomyomata than myometrium in eight out of 11 cases. In all cases both forms were present, with a consistent dominance of PR-A over PR-B. However an RNase protection assay showed that there was no difference between the concentrations of mRNA encoding PR-A and PR-B, or between the mRNA concentrations in leiomyomata and normal myometrium. We conclude that the observed differences between the levels of immunoreactive PR in leiomyomata and myometrium may result from post-translational control, and support the use of progesterone antagonists in the treatment of leiomyomata.
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PMID:Distribution of the A and B forms of the progesterone receptor messenger ribonucleic acid and protein in uterine leiomyomata and adjacent myometrium. 915 48

Down-regulation of the progesterone receptor (PR) by its ligand has been demonstrated in breast cancer cell lines and in the rat uterus. However, in the stromal cells of endometrium, reduction of the PR level is not apparent in the luteal phase of the menstrual cycle. The purpose of this study was to determine the effect of progestin on PR and PR mRNA in isolated human endometrial stromal cells. Western blot analysis showed that progesterone or medroxyprogesterone acetate increased the two isoforms, PR-A and PR-B, in stromal cells but reduced them in glandular epithelial cells. Progestin increased the PR-A and PR-B mRNA by 2- to > 10-fold in the stromal cells of 12 specimens measured by solution hybridization-ribonuclease protection assay. A time study showed that the increase in PR mRNA required at least a 2- to 3-day incubation with progestin and that the high mRNA levels were maintained or increased slightly beyond 10 days of progestin incubation. The stimulatory effect of progestin was inhibited by RU-486 and by cycloheximide, suggesting that the up-regulation requires ligand binding to PR and de novo protein synthesis. Progestin also increased the stability of PR mRNA in endometrial stromal cells. These results demonstrated for the first time that progestin exerts an up-regulation of PR by increasing the steady-state level of PR mRNA specifically in human endometrial stromal cells. The up-regulation of PR by progestin may be mediated in part by progestin-induced endometrial stromal cell factors such as estrogen and insulin-like growth factor-I, both of which stimulated the PR-A and PR-B mRNA in stromal cells.
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PMID:Regulation of progesterone receptor messenger ribonucleic acid by progestin in human endometrial stromal cells. 940 41

To gain insight into the possible biological role of variant estrogen receptor (ER) expression in human breast cancer, we have undertaken a study to determine if the expression of the clone 4 variant ER mRNA was associated with markers of either reduced endocrine sensitivity [i.e., progesterone receptor (PgR) negativity] or a poor prognosis (node positivity, large tumor size, and high percentage S-phase fraction). mRNA levels of clone 4 variant ER and wild-type (WT) ER were assayed by RNase protection assay in 106 breast cancer specimens. The tumors comprised two major groups: "good" prognosis and "poor" prognosis based on several conventional biological prognostic features. Each group was divided into three subgroups (ER+/PgR+, ER+/PgR-, and ER-/PgR-). WT and clone 4 variant ER mRNAs were undetected in ER-/PgR- tumors. We determined that clone 4 variant ER mRNA levels varied proportionately with WT mRNA levels, and regression analysis was used to determine if the amount of clone 4 variant ER mRNA relative to WT was associated with prognosis or PgR content. Significantly higher levels of clone 4 variant ER mRNA relative to WT were found in tumors with markers of poor prognosis compared to those with markers of good prognosis (P = 0.0004). Significantly higher levels of clone 4 variant ER mRNA relative to WT were found in PgR- tumors compared to PgR+ tumors (P = 0.011). Such data are consistent with an association of clone 4 variant ER mRNA expression with progression of human breast cancer from hormone dependence to independence.
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PMID:Relationship of clone 4 estrogen receptor variant messenger RNA expression to some known prognostic variables in human breast cancer. 981 68

Targeted disruption of the mouse estrogen receptor-alpha gene (estrogen receptor-alpha knockout; ERKO) results in a highly novel ovarian phenotype in the adult. The ERKO mouse model was used to characterize ER alpha-dependent processes in the ovary. Visualization of the ovaries of 10-, 20-, and 50-day-old wild-type (WT) and ERKO mice showed that the ERKO phenotype developed between 20 and 50 days of age. Developmental progression through the primordial, primary, and antral follicle stages appeared normal, but functional maturation of preovulatory follicles was arrested resulting in atresia or in anovulatory follicles, which in many cases formed large, hemorrhagic cysts. Corpora lutea were absent, which also indicates that the normal biochemical and mechanical processes that accomplish ovulation were compromised. Northern and ribonuclease protection analyses indicated that ERKO ovary FSH receptor (FSHR) messenger RNA (mRNA) expression was approximately 4-fold greater than in WT controls. Ovarian LH receptor (LHR) mRNA expression was also higher in the ERKO animals. Cellular localization studies by in situ hybridization analysis of ERKO ovaries showed a high level of LHR mRNA expression in the granulosa and thecal layers of virtually all the antral follicles. Ribonuclease protection analyses showed that ovarian progesterone receptor and androgen receptor mRNA expression were similar in the two groups. These results indicated that ER alpha action was not a prerequisite for LHR mRNA expression by thecal or granulosa cells or for ovarian expression of progesterone receptor mRNA. Ovarian estrogen receptor beta (ER beta) was detected immunohistochemically, was sharply compartmentalized to the granulosa cells, and was expressed approximately equally in the ERKO animals and the WT controls. In contrast, ER alpha staining was present in the thecal cells but not the granulosa cells of the WT animals. The summary findings indicate that in the adult the major cause of the ERKO phenotype is high circulating LH interacting with functional LHR of the theca and granulosa cells. These features result in a failure of the normal maturational events leading to successful ovulation and luteinization and presumably involve both hypothalamic-pituitary and intraovarian mechanisms dependent upon ER alpha action. The presence of ER beta in the granulosa cells did not rescue the phenotype of the ovary.
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PMID:Targeted disruption of the estrogen receptor-alpha gene in female mice: characterization of ovarian responses and phenotype in the adult. 1034 64

Glucosidase I initiates the processing of asparagine (N-) linked glycoproteins by removing the distal alpha1,2-linked glucosyl residue of the tetradecasaccharide Glc(3)Man(9)GlcNAc(2). The gene encoding this enzyme was isolated and its structural organization and promoter activity determined. The major transcript for glucosidase I on northern blot appeared to be 3.1 kb; Southern blotting and DNA sequencing indicated the size of the gene to be 6.8 kb, comprising four exons separated by three introns. The first exon encodes the cytoplasmic tail and transmembrane domain; the fourth encodes the putative catalytic domain of the enzyme. Exon-intron junctions are flanked by consensus splice donor and acceptor sequences. Transcription initiation sites were mapped by primer extension, ribonuclease protection assay and RT-PCR analysis. Primer extension results showed multiple initiation sites at -150, -156, and -272 bp relative to the translation initiation codon ATG. Sequence analysis of 5' flanking region showed no canonical TATA box, a high GC content, Sp1 and ETF binding sites (typical of a housekeeping gene promoter). Also noteworthy, the promoter region contains several generic STAT factor binding sites, one nearly perfect, and two half GR binding elements. Other cis- acting elements recognized by transcription factors such as AP-2, NF-kappaB, estrogen receptor, and progesterone receptor (PR) were also present in the putative promoter region. To determine the promoter activity, a construct encompassing the region between -2114 to -5 bp of the putative promoter was ligated to the chloramphenicol acetyltransferase (CAT) reporter plasmid and transiently transfected into COS 7 cells. CAT assay results clearly show transcriptional activity of the promoter.
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PMID:Genomic organization and promoter activity of glucosidase I gene. 1040 45


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