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 studies have revealed that the expression of P-glycoprotein/multidrug resistance genes is crucial for the development of resistance to a number of lipophilic cancer chemotherapeutic agents. To better understand the regulatory mechanisms of pgp gene expression, we isolated and characterized a DNA fragment containing the 5' portion of a Chinese hamster pgp gene. DNA sequence analysis revealed that this gene is pgp1, the hamster homologue of murine mdr3/mdr1a. This gene is expressed at a higher level in intestines than in kidney and liver, consistent with the expression pattern for the murine mdr3/mdr1a gene. The major transcription start site, determined by the S1 nuclease protection, RNase protection, and primer extension methods, lies 67 nucleotides upstream of the murine and human downstream transcription start site. A chimera containing 101 base pairs upstream from this start site and the chloramphenicol acetyltransferase (CAT) gene was able to direct CAT expression in transient transfection experiments. The AP-1 site, located at -48 base pairs, was crucial for the full pgp1 promoter activity, as demonstrated by site-directed mutagenesis of this site, enhancement of the CAT expression by cotransfection with the expression vectors encoding c-Jun/c-Fos genes, but sequestration with those containing retinoic acid receptor genes. The sequestration effect could be partially abolished when c-Jun/c-Fos genes were also included in cotransfection. An AP-1 or AP-1-like site is also present at the same location in both human and mouse mdr homologues. The involvement of AP-1 in the expression of mammalian pgp1-class genes is discussed.
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PMID:Analysis of the Chinese hamster P-glycoprotein/multidrug resistance gene pgp1 reveals that the AP-1 site is essential for full promoter activity. 166 Nov 34

Retinoic acid (RA) has profound effects on cell proliferation and differentiation both in vitro and in vivo. Many human cell lines are known to be sensitive to the growth-inhibitory action of RA. We analyzed established human solid tumor-derived cell lines for their RA sensitivity. Growth inhibition by RA in monolayer was examined by [3H]thymidine incorporation and cell proliferation. Here we report that 11 widely used human cell lines were RA resistant. The majority are carcinoma derived (A-431, BT-20, C-41, ACHN, HCT116, 293, A549, and PA-1); two are sarcoma derived (Saos-2 and A673); and one is a melanoma cell line (A-375). Since nuclear retinoid receptors are implicated in the biological effects of RA, we examined the expression of retinoic acid receptors (RARs) RAR alpha, RAR beta, RAR gamma, and the retinoid X receptors (RXRs) RXR alpha, RXR beta, and RXR gamma in the RA-resistant cell lines by northern blotting and by RNase protection analysis for RAR beta. RAR alpha transcripts were constitutively expressed in all cell lines. By contrast, RAR beta was expressed in only seven RA-resistant cell lines (Saos-2, ACHN, 293, A549, A-375, A673, and PA-1), and its level was enhanced by RA in some cases. In most cell lines, RAR gamma expression was low and was not affected by RA. The RXR genes showed a very distinct expression pattern in the group of selected cell lines. In general, RXR alpha was the most abundantly expressed subtype, RXR beta was expressed at low levels, and RXR gamma could not be detected. In none of the RA-resistant cell lines was RXR expression modulated by RA. The results presented here indicate that the resistance of these human tumor cell lines to RA cannot be simply correlated with expression of RAR or RXR or both.
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PMID:Retinoic acid receptor and retinoid X receptor expression in retinoic acid-resistant human tumor cell lines. 769 Oct 69

T3 inhibits transcription of the rat TSH beta gene, and two T3 response elements have been identified that bind T3 receptors and that share sequence homology with the consensus sequence that is also recognized by retinoic acid receptors (RARs). We, therefore, asked whether RA was a regulator of TSH beta gene expression in vivo. Using RNase protection analysis, we found that vitamin A deficiency led to a 2-fold increase in rat pituitary TSH beta messenger RNA (mRNA) levels, which returned to normal 18 h after treatment with RA (20 micrograms/rat). Vitamin A deficiency had no effect on TSH beta mRNA levels in hypothyroid rats. Coadministration of RA and T3 (10 micrograms/100g body wt) to either vitamin A-deficient or vitamin A-deficient, hypothyroid animals caused decreases in TSH beta mRNA content that were indistinguishable from those seen with T3 alone. Surprisingly, vitamin A deficiency had no significant effect on GH mRNA levels in euthyroid or hypothyroid rats. Furthermore, treatment of vitamin A-deficient, hypothyroid animals with RA for either 18 or 72 h had no effect on GH mRNA levels, whereas T3 caused 11-fold and 18-fold increases in GH mRNA, respectively, at these times. We also used transient transfection to test for direct, retinoid receptor-mediated regulation of TSH beta gene transcription by RA. A plasmid TSH beta luciferase, containing 0.8 kilobases of rat TSH beta gene 5'-flanking sequences, exon 1, and 150 base pairs of intron 1, was transfected into CV-1 cells. Cotransfection with RAR alpha and retinoid X receptor-beta induced TSH beta expression by 3.5-fold, and treatment with RA suppressed this induction by 46%. These results show that vitamin A levels play a significant role in regulating the expression of the TSH beta gene, but not the GH gene, in vivo and suggest that RA may suppress TSH beta gene transcription directly by an RAR-retinoid X receptor heterodimer-mediated mechanism.
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PMID:Regulation of thyroid-stimulating hormone beta-subunit and growth hormone messenger ribonucleic acid levels in the rat: effect of vitamin A status. 783 86

In amphibian limb regeneration memory for position in the proximal-distal axis can be respecified by retinoic acid. The favoured candidates to mediate this effect are the retinoic acid receptors (RARs) and of the RARs identified in the regeneration blastema, the delta receptor is the most abundant. The presence in blastemal mesenchyme of at least two delta receptor isoforms, delta 1 and delta 2, alternatively spliced at the A-B junction, was demonstrated in expression studies and by PCR cloning. The delta 1 receptor is abundant in regenerative structures such as the limb and tail, whereas the delta 2 and alpha receptors show a more uniform pattern of expression across adult newt tissues. Full-length cloning of the delta 1 receptor established the presence of an unusually long open reading frame and N-terminal sequence that appears unique among vertebrate retinoic acid receptors. Transient transfection of expression constructs into COS cells followed by Western blotting confirmed the existence of at least three potential initiation sites for delta 1 translation. The possibility that delta 1 RAR expression may specify positional memory directly was tested in RNase protection experiments. delta 1 receptor message is increased on amputation, but does not exhibit a pronounced differential distribution along the proximal-distal axis in normal and regenerating limbs, nor does it show a persistent alteration in expression levels following a dose of retinoic acid sufficient to respecify position. The possibility that the morphogenetic effects of RA may be mediated through receptor interactions is raised by the finding that single mesenchymal blastemal cells in culture can express multiple RAR subtypes (delta 1 and alpha) and isoforms (delta 1 and delta 2).
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PMID:Delta retinoic acid receptor isoform delta 1 is distinguished by its exceptional N-terminal sequence and abundance in the limb regeneration blastema. 838 39

The effect of vitamin A supplementation on stearoyl-CoA desaturase gene 1 expression in mouse liver was characterized. Normal BALB/c mice were fed 0.01% and 0.1% retinol palmitate as components of nonpurified diets. This treatment resulted in a 3-fold and a 7-fold induction of SCD1 mRNA levels, respectively, as determined by RNase protection analysis. Vitamin A-deficient animals were also fed diets containing 0.01% and 0.1% retinol palmitate, resulting in a similar pattern of SCD1 mRNA induction. Fatty acid synthase and beta-actin mRNA levels did not respond consistently or significantly to retinoic acid treatment. Dietary and hormonal studies were carried out to investigate the role of the retinoid X receptor in the regulation of SCD1 by type II steroid hormones. A receptor-saturating dose of thyroid hormone, triiodothyronine, repressed vitamin A-elevated SCD1 mRNA levels in vivo. Peroxisome proliferator-elevated SCD1 mRNA levels were unaffected by administration of thyroid hormone. This suggests that the retinoic acid receptor transcriptionally regulates SCD1 through a traditional mechanism of heterodimerization with the retinoid X receptor.
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PMID:Regulation of hepatic stearoyl-CoA desaturase gene 1 by vitamin A. 907 Feb 50

We have shown earlier that surgical human breast cancer tissue can be maintained in culture as in culture as intact tissue slices (organ culture). Because tumor organ culture ostensibly preserves the interacting network of tumor cells, stromal fibroblasts, endothelial cells and extracellular matrix, it represents a rather complex culture system. Such a system may be especially useful in preclinical trials, where the objective is to make extrapolations to the even more complex in vivo situation. A classical therapeutic target in breast cancer is the estrogen receptor, and we showed earlier that human breast cancer slices retain expression of this receptor in culture. Retinoic acid, the active form of vitamin A, is also an important (negative) growth regulator in breast cancer. In the present communication, we used in situ hybridization to monitor the expression of retinoic acid receptors in tumor slices cultured for 4 days. We show that both members of the all-trans retinoic acid and 9-cis retinoic acid receptor family (RAR and RXR, respectively) are expressed. Moreover, RNase protection analysis showed that expression of the cellular retinoic acid-binding protein type II gene, a known retinoic acid target gene, is upregulated by treatment with 1 microM all-trans retinoic acid for 2 days. These findings attest to the feasibility of using tumor organ cultures as a preclinical model for the evaluation of synthetic vitamin A derivatives (retinoids).
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PMID:Human breast carcinoma slice cultures retain retinoic acid sensitivity. 918 Oct 52

Bmp2, a highly conserved member of the transforming growth factor-beta gene family, is crucial for normal development. Retinoic acid, combined with cAMP analogs, sharply induces the Bmp2 mRNA during the differentiation of F9 embryonal carcinoma cells into parietal endoderm. Retinoic acid (RA) also induces the Bmp2 gene in chick limb buds. Since normal Bmp2 expression may require an endogenous retinoid signal and aberrant Bmp2 expression may cause some aspects of RA-induced teratogenesis, we studied the mechanism underlying the induction of Bmp2. Measurements of the Bmp2 mRNA half-life and nuclear run-on assays indicated that RA stimulated the transcription rate of the Bmp2 gene. The results of ribonuclease protection and primer extension assays indicated that Bmp2 transcription started 2,127 nucleotides upstream of the translation start site in F9 cells. To identify genetic elements controlling this transcription rate increase, upstream and downstream genomic sequences flanking the Bmp2 gene were screened using chloramphenicol acetyltransferase reporter genes in F9 cells and beta-galactosidase reporter genes in Saccharomyces cerevisiae that were cotransformed with retinoic acid receptor and retinoid X receptor expression plasmids. RA-dependent transcriptional activation was detected between base pairs -2,373 and -2,316 relative to the translation start site. We also identified a required Sp1 binding site between -2,308 and -2,298. The data indicate that Bmp2 is directly regulated by retinoic acid-bound receptors and Sp1.
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PMID:Transcriptional regulation of the Bmp2 gene. Retinoic acid induction in F9 embryonal carcinoma cells and Saccharomyces cerevisiae. 988 May 12

The peroxisome proliferator-activated receptor alpha (PPARalpha) plays a key role in lipid and lipoprotein metabolism. However, important inter- and intraspecies differences exist in the response to PPARalpha activators. This incited us to screen for PPARalpha variants with different signaling functions. In the present study, using a RT-PCR approach a variant human PPARalpha mRNA species was identified, which lacks the entire exon 6 due to alternative splicing. This deletion leads to the introduction of a premature stop codon, resulting in the formation of a truncated PPARalpha protein (PPARalphatr) lacking part of the hinge region and the entire ligand-binding domain. RNase protection analysis demonstrated that PPARalphatr mRNA is expressed in several human tissues and cells, representing between 20-50% of total PPARalpha mRNA. By contrast, PPARalphatr mRNA could not be detected in rodent tissues. Western blot analysis using PPARalpha-specific antibodies demonstrated the presence of an immunoreactive protein migrating at the size of in vitro produced PPARalphatr protein both in human hepatoma HepG2 cells and in human hepatocytes. Both in the presence or absence of 9-cis-retinoic acid receptor, PPARalphatr did not bind to DNA in gel shift assays. Immunocytochemical analysis of transfected CV-1 cells indicated that, whereas transfected PPARalphawt was mainly nuclear localized, the majority of PPARalphatr resided in the cytoplasm, with presence in the nucleus depending on cell culture conditions. Whereas a chimeric PPARalphatr protein containing a nuclear localization signal cloned at its N-terminal localized into the nucleus and exhibited strong negative activity on PPARalphawt transactivation function, PPARalphatr interfered with PPARalphatr transactivation function only under culture conditions inducing its nuclear localization. Cotransfection of the coactivator CREB-binding protein relieved the transcriptional repression of PPARalphawt by PPARalphatr, suggesting that the dominant negative effect of PPARalphatr might occur through competition for essential coactivators. In addition, PPARalphatr interfered with transcriptional activity of other nuclear receptors such as PPARgamma, hepatic nuclear factor-4, and glucocorticoid receptor-alpha, which share CREB-binding protein/p300 as a coactivator. Thus, we have identified a human PPARalpha splice variant that may negatively interfere with PPARalphawt function. Factors regulating either the ratio of PPARalphawt vs. PPARalphatr mRNA or the nuclear entry of PPARalphatr protein should therefore lead to altered signaling via the PPARalpha and, possibly also, other nuclear receptor pathways.
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PMID:A truncated human peroxisome proliferator-activated receptor alpha splice variant with dominant negative activity. 1047 44

The effects of all-trans-retinoic acid (RA), 9-cis-retinoic acid (9cRA), and thyroid hormone (T3) on GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression were studied using ribonuclease protection assay in the fetal rat pituitary gland and in MtT/S cells, a clonal GH cell line derived from an estrogen-induced somatotropic tumor in the rat. Although RA (1 microM), 9cRA (1 microM), or T3 (1 nM) alone showed little effect on GHRH-R mRNA expression in the MtT/S cells, each of these substances was found to act synergistically with dexamethasone (DEX; 500 nM) to increase GHRH-R mRNA expression. The effects of RAs and T3 were dose dependent, with maximum effects observed at 1 microM and 1 nM, respectively. The maximum effect of RAs or T3 was not further augmented by the addition of T3 or RAs, respectively. No apparent differences were observed in this study between the actions of RA and 9cRA. The Northern analyses showed that MtT/S cells express retinoic acid receptor alpha2 mRNA and thyroid hormone receptor beta2 mRNA, and DEX did not affect the levels of these mRNAs. This suggests that the role of DEX in enabling RAs or T3 to up-regulate GHRH-R mRNA levels is not an induction of the expression of each specific receptor for RAs and T3. The similar enhancement of DEX induction of GHRH-R mRNA by RAs or T3 was also observed in the fetal rat pituitary gland in culture, suggesting that RA and/or T3 is involved in the mechanisms responsible for the developmentally regulated expression of GHRH-R mRNA.
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PMID:Retinoic acids and thyroid hormone act synergistically with dexamethasone to increase growth hormone-releasing hormone receptor messenger ribonucleic acid expression. 1110 47

Peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that control the expression of genes involved in lipid homeostasis in mammals. We searched for PPAR in sea bass, a marine fish of particular interest to aquaculture, after hypothesizing that the physiological and molecular processes that regulate lipid metabolism in fish are similar to those in mammals. Here, we report the identification of complementary DNA and corresponding genomic sequences that encode three distinct PPAR from sea bass. The sea bass PPAR are the structural homologs of the mammalian PPAR alpha, beta/delta, and gamma isotypes. As revealed by RNase protection, the tissue expression profile of the fish PPAR appears to be very similar to that of the mammalian PPAR homologs. Thus, PPAR alpha is mainly expressed in the liver, PPAR gamma in adipose tissue, and PPAR beta in all tissues tested, with its highest levels in the liver, where it is also the dominant isotype expressed. Like mammalian PPAR, the sea bass isotypes recognize and bind to PPAR response elements of both mammalian and piscine origin, as heterodimers with the 9-cis retinoic acid receptor. Through the coactivator-dependent receptor ligand assay, we also demonstrated that natural FA and synthetic hypolipidemic compounds can act as ligands of the sea bass PPAR alpha and beta isotypes. This suggests that the sea bass PPAR act through similar mechanisms and perform the same critical lipid metabolism functions as mammalian PPAR.
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PMID:Molecular characterization of three peroxisome proliferator-activated receptors from the sea bass (Dicentrarchus labrax). 1572 23


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