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Results for “RNA, Competitive Endogenous”

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At least 145 records · Page 8Linked to original sources

PubMed1998

Up-regulation of neuropeptide Y-Y2 receptors in an animal model of temporal lobe epilepsy.

Receptor autoradiography with the Y2 receptor ligand 125I-peptide YY3-36 and in situ hybridization were applied to investigate changes in neuropeptide tyrosine-Y2 receptor expression after kainic acid-induced recurrent seizures in the rat hippocampus. In the strata oriens and radiatum of CA1 to CA3, which are densely innervated by Y2 receptor-bearing Schaffer collateral terminals, a transient 2-fold increase in Y2 receptor affinity was observed after 4-12 hr, with a later slow decline. No change was seen in Y2 mRNA expression in CA2/CA3 pyramidal cells, from which Schaffer collaterals originate. Conversely, in granule cells of the dentate gyrus, markedly elevated Y2 mRNA concentrations were observed (by 740% in the dorsal hippocampus) 24-48 hr after kainate injection. At the same time, a marked and lasting (up to 6 months) increase in the number of Y2 receptor sites (by 800%) was seen in the dentate hilus, which is innervated densely by mossy fibers. The early increase in Y2 receptor affinity in Schaffer collaterals was accompanied by a 60% decrease in the EC50 of peptide YY3-36 in inhibiting K(+)-stimulated glutamate release in hippocampal slices from kainic acid-treated rats. Our data indicate transient up-regulation of presynaptic Y2 receptors in Schaffer collaterals by a change in affinity and a permanent de novo synthesis of presynaptic Y2 receptors in granule cells/mossy fibers. These changes may cause augmented presynaptic inhibition of glutamate release from different hippocampal sites and, in conjunction with increased concentrations of neuropeptide tyrosine in mossy fibers, may represent an endogenous reactive anticonvulsant mechanism.

Animals↗

PubMed2004

A regulatory trade-off as a source of strain variation in the species Escherichia coli.

There are few existing indications that strain variation in prokaryotic gene regulation is common or has evolutionary advantage. In this study, we report on isolates of Escherichia coli with distinct ratios of sigma factors (RpoD, sigmaD, or sigma70 and RpoS or sigmaS) that affect transcription initiated by RNA polymerase. Both laboratory E. coli K-12 lineages and nondomesticated isolates exhibit strain-specific endogenous levels of RpoS protein. We demonstrate that variation in genome usage underpins intraspecific variability in transcription patterns, resistance to external stresses, and the choice of beneficial mutations under nutrient limitation. Most unexpectedly, RpoS also controlled strain variation with respect to the metabolic capability of bacteria with more than a dozen carbon sources. Strains with higher sigmaS levels were more resistant to external stress but metabolized fewer substrates and poorly competed for low concentrations of nutrients. On the other hand, strains with lower sigmaS levels had broader nutritional capabilities and better competitive ability with low nutrient concentrations but low resistance to external stress. In other words, RpoS influenced both r and K strategist functions of bacteria simultaneously. The evolutionary principle driving strain variation is proposed to be a conceptually novel trade-off that we term SPANC (for "self-preservation and nutritional competence"). The availability of multiple SPANC settings potentially broadens the niche occupied by a species consisting of individuals with narrow specialization and reveals an evolutionary advantage offered by polymorphic regulation. Regulatory diversity is likely to be a significant contributor to complexity in a bacterial world in which multiple sigma factors are a universal feature.

Acids↗

PubMed1997

Parathyroid hormone-related protein upregulates interleukin-1beta-induced nitric oxide synthesis.

The effect of parathyroid hormone-related protein on interleukin-1beta-induced nitric oxide production was studied in rat vascular smooth muscle cells. Interleukin-1beta time- and dose-dependently enhanced the production of nitrite, a stable metabolite of nitric oxide. Parathyroid hormone-related protein(1-34) alone up to 10(-7) mol/L had no obvious effect, but significantly increased the cytokine-induced nitrite production. RNA analysis revealed that the synergistic effect of parathyroid hormone-related protein(1-34) resulted from a potentiation of the expression of inducible nitric oxide synthase and GTP-cyclohydrolase I, the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, which is a cofactor of nitric oxide synthase. The increased nitric oxide release induced by interleukin-1beta or interleukin-1beta with parathyroid hormone-related protein(1-34) was completely inhibited by coincubation with 3x10(-3) mol/L N(G)-monomethyl-L-arginine, a competitive inhibitor of nitric oxide synthase, or with 10(-3) mol/L 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP-cyclohydrolase I. Endothelin-1 potentiated interleukin-1beta induction of nitric oxide, which might be mediated by endogenous parathyroid hormone-related protein. Neutralization of exogenous or endogenous parathyroid hormone-related protein with antibody attenuated the synergistic effect of parathyroid hormone-related protein, but did not affect interleukin-1beta induction of nitric oxide. These results suggest that locally produced parathyroid hormone-related protein acts as a synergistic regulator upregulating interleukin-1beta-induced nitric oxide synthesis in the cardiovascular system, and thereby may affect vascular tone and/or vascular remodeling after vascular injury in some pathological processes such as atherosclerosis and hypertension.

Animals↗

PubMed2005

Functional analysis of MRG-1: the ortholog of human MRG15 in Caenorhabditis elegans.

Mortality Factor on Chromosome 4 (MORF4) induces senescence in several immortal human cell lines. MORF-related gene on chromosome 15 (MRG15), another expressed family member, is highly conserved and expressed in yeast to humans. To determine the biological functions of human MRG15 (hMRG15) we used RNA-mediated interference (RNAi) to silence mrg-1, the Caenorhabditis elegans ortholog, and its closest homolog Y37D8A.11. Expression of mrg-1 RNAi resulted in sterility, body wall defects, vulval protrusion, and posterior developmental defects in worms. We expressed mrg-1 under its own and the cytomegalovirus promoter in human cells. Both constructs were expressed, indicating that C. elegans promoter elements are functional in mammalian cells. Overexpression from the cytomegalovirus promoter eventually resulted in cell death, possibly due to competition with hMRG15 in endogenous nucleoprotein complexes. Recent data indicate a role for yeast and human MRG15 in transcriptional regulation via chromatin remodeling. Here we demonstrate the importance of mrg-1 in development and reproduction in C. elegans and discuss its potential to impact the aging process.

Aging↗

PubMed2001

hnRNP F influences binding of a 64-kilodalton subunit of cleavage stimulation factor to mRNA precursors in mouse B cells.

Previous studies on the regulation of polyadenylation of the immunoglobulin (Ig) heavy-chain pre-mRNA argued for trans-acting modifiers of the cleavage-polyadenylation reaction operating differentially during B-cell developmental stages. Using four complementary approaches, we demonstrate that a change in the level of hnRNP F is an important determinant in the regulated use of alternative polyadenylation sites between memory and plasma stage B cells. First, by Western analyses of cellular proteins, the ratio of hnRNP F to H or H' was found to be higher in memory B cells than in plasma cells. In memory B cells the activity of CstF-64 binding to pre-mRNA, but not its amount, was reduced. Second, examination of the complexes formed on input pre-mRNA in nuclear extracts revealed large assemblages containing hnRNP H, H', and F but deficient in CstF-64 in memory B-cell extracts but not in plasma cells. Formation of these large complexes is dependent on the region downstream of the AAUAAA in pre-mRNA, suggesting that CstF-64 and the hnRNPs compete for a similar region. Third, using a recombinant protein we showed that hnRNP F could bind to the region downstream of a poly(A) site, block CstF-64 association with RNA, and inhibit the cleavage reaction. Fourth, overexpression of recombinant hnRNP F in plasma cells resulted in a decrease in the endogenous Ig heavy-chain mRNA secretory form-to-membrane ratio. These results demonstrate that mammalian hnRNP F can act as a negative regulator in the pre-mRNA cleavage reaction and that increased expression of F in memory B cells contributes to the suppression of the Ig heavy-chain secretory poly(A) site.

Amino Acid Sequence↗

PubMed2002

The role of the PKR-inhibitory genes, E3L and K3L, in determining vaccinia virus host range.

Vaccinia virus encodes two regulators of the cellular antiviral response. The E3L gene is thought to act primarily by sequestering double-stranded RNA, whereas the K3L gene is thought to act as a competitive inhibitor of the double-stranded RNA-dependent protein kinase, PKR. The broad host range associated with vaccinia virus replication appears to be related to the presence of these genes. The E3L gene is required for replication in HeLa cells, but is not required for replication in BHK cells. On the contrary, the K3L gene is required for replication in BHK cells, but is dispensable for replication in HeLa cells. Our results suggest that these cell lines varied in the expression of endogenous activatable PKR and that replication of vaccinia virus in different cell lines led to altered levels of double-stranded RNA synthesis from the virus. Vaccinia virus was able to overcome these cellular variations by regulating PKR activity through the synthesis of either E3L or K3L. The results suggest that vaccinia virus has evolved a broad host range by maintaining both the E3L and the K3L genes.

Animals↗

PubMedDate not supplied

Profile of cytokines produced in tumor tissue after administration of cyclophosphamide in a combination therapy with tumor necrosis factor.

BACKGROUND: Recent studies have shown that locoregional administration of tumor necrosis factor (TNF) or production of endogenous TNF in tumor tissue with a chemotherapeutic agent showed considerable antitumor effect without severe toxicities. To analyze the immunological role of chemotherapeutic agents in locoregional TNF therapy, the effect of cyclophosphamide (CY) on cytokine production after ONO-4007 treatment was examined. MATERIALS AND METHODS: Seven days after inoculation of Meth A fibrosarcoma in BALB/c mice, CY (100-150 mg/kg) was injected intraperitoneally and, after another 7 days, ONO-4007 (30 mg/kg) was injected intravenously. A competitive PCR quantitative analysis of the induced cytokine messenger RNA (mRNA) was performed for IL-12 (p40), TGF-beta, TNF-alpha, IL-1beta, IL-10 and IL-6. RESULTS: The antitumor effect of ONO-4007 was enhanced by preadministration of CY. CY significantly enhanced IL-12 (p40) mRNA compared to that by ONO-4007 alone. No increase in TGF-beta mRNA was observed in either treatment. CONCLUSION: The preadministration of CY enhances IL-12 production in tumor tissues and shifts the cytokine profile to the dominant Th1 type.

Animals↗

PubMed1984

Lymphokine regulation of activated (G1) lymphocytes. II. Glucocorticoid and anti-Tac-induced inhibition of human T lymphocyte proliferation.

The regulation of the first cell cycle of human, activated (G1) PBL was analyzed by flow cytometry and [3H]thymidine incorporation. Endogenous IL 2 production was blocked in situ by pharmacologic concentration of DEX (100 to 1000 nM), resulting in an 80 to 90% reduction of thymidine uptake. Although T lymphocyte activation (G0-G1a transition) by PHA was unaltered, cells remained in the G1a phase of the cell cycle due to insufficient RNA synthesis for proliferation. The addition of IL 2-containing supernatants reversed this inhibitory effect of DEX by allowing the cells to synthesize more RNA (G1a-G1b transition). Such cells could enter the S phase and proliferate. Similar studies were performed on cells treated with a monoclonal antibody (anti-Tac) against the IL 2 receptor. In these studies, IL 2-induced RNA synthesis, and subsequent proliferation of DEX-treated and PHA-stimulated cells was inhibited by anti-Tac. Anti-Tac did not, however, inhibit the effect of endogenous IL 2 (PHA-stimulated PBL without DEX treatment), although it did bind equally well to such cells. Thus, IL 2 directly or indirectly regulates human T cell proliferation at the level of RNA synthesis. Furthermore, anti-Tac can inhibit the mitogenic signal given by endogenous IL 2, but not by in situ produced IL 2, an observation of importance to further investigations of the mechanisms by which IL 2 interacts with specific receptors to elicit proliferation.

Adult↗

PubMed2001

An aryl hydrocarbon receptor (AHR) homologue from the soft-shell clam, Mya arenaria: evidence that invertebrate AHR homologues lack 2,3,7,8-tetrachlorodibenzo-p-dioxin and beta-naphthoflavone binding.

The aryl hydrocarbon receptor (AHR) mediates numerous toxic effects following exposure of vertebrate animals to certain aromatic environmental contaminants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To investigate possible effects of TCDD on invertebrates, a cDNA encoding an AHR homologue was cloned from the soft-shell clam, Mya arenaria. The predicted amino acid sequence contains regions characteristic of vertebrate AHRs: basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains and a glutamine-rich region. Phylogenetic analysis shows that the clam AHR sequence groups within the AHR subfamily of the bHLH-PAS family, in a clade containing AHR homologues from Drosophila melanogaster and Caenorhabditis elegans. AHR mRNA expression was detected in all tissue types tested: adductor muscle, digestive gland, foot, gill, gonad, mantle, and siphon. The in vitro-expressed clam AHR exhibited sequence-specific interactions with a mammalian xenobiotic response element (XRE). Velocity sedimentation analysis using either in vitro-expressed clam AHR or clam cytosolic proteins showed that this AHR homologue binds neither [(3)H]TCDD nor [(3)H]beta-naphthoflavone (BNF). Similarly, in vitro-expressed D. melanogaster and C. elegans AHR homologues lacked specific binding of these compounds. Thus, the absence of specific, high-affinity binding of the prototypical AHR ligands TCDD and BNF, is a property shared by known invertebrate AHR homologues, distinguishing them from vertebrate AHRs. Comparative studies of phylogenetically diverse organisms may help identify an endogenous ligand(s) and the physiological role(s) for this protein.

Amino Acid Sequence↗

PubMed2006

A novel role for proline- and acid-rich basic region leucine zipper (PAR bZIP) proteins in the transcriptional regulation of a BH3-only proapoptotic gene.

Proline- and acid-rich (PAR) basic region leucine zipper (bZIP) proteins thyrotroph embryonic factor (TEF), D-site-binding protein (DBP), and hepatic leukemia factor have been involved in neurotransmitter homeostasis and amino acid metabolism. Here we demonstrate a novel role for these proteins in the transcriptional control of a BH3-only gene. PAR bZIP proteins are able to transactivate the promoter of bcl-gS. This promoter is particularly responsive to TEF activation and is silenced by NFIL3, a repressor that shares the consensus binding site with PAR bZIP proteins. Consistently, transfection of TEF induces the expression of endogenous bcl-gS in cancer cells, and this induction is independent of p53. A naturally occurring variant of DBP (tDBP), lacking the transactivation domain, has been identified and shown to impede the formation of active TEF dimers in a competitive manner and to reduce the TEF-dependent induction of bcl-gS. Of note, treatment of cancer cells with etoposide induces TEF activation and promotes the expression of bcl-gS. Furthermore, blockade of bcl-gS or TEF expression by a small interfering RNA strategy or transfection with tDBP significantly reduces the etoposide-mediated apoptotic cell death. These findings represent the first described role for PAR bZIP proteins in the regulation of a gene involved in the execution of apoptosis.

Apoptosis↗

PubMed2003

Inhibition of vertebrate telomerases by the triphosphate derivatives of carbocyclic oxetanocin analogs.

Telomerase is a cellular endogenous reverse transcriptase that uses its internal RNA as a template for extension of the telomere repeat, thus maintaining telomere length. In order to clarify the susceptibility of telomerase to triphosphate derivatives of carbocyclic oxetanocins, inhibition by 9-[trans-trans-2,3-bis(hydroxymethyl)cyclobutyl]guanine triphosphate (C.OXT-GTP) and its methylene analog, 9-(cis-3-hydroxymethyl-2-methylenecyclobutyl)guanine triphosphate (m-C.OXT-GTP) was investigated. Both compounds showed potent inhibitory activity. Lineweaver-Burk plot analyses showed that the inhibition mode of these compounds was competitive with dGTP, the Ki values for C.OXT-GTP and m-C.OXT-GTP being 2.0 microM and 4.9 microM, respectively, and thus smaller than the Km of dGTP (11 microM).

Adenine↗

PubMed1993

Heterogeneous expression of alpha 1-adrenoceptor subtypes among rat nephron segments.

alpha 1-Adrenoceptor subtypes mediate many of the actions of the renal nerve, but their locations along the nephron are unknown. We investigated the distribution of alpha 1-adrenoceptor subtype mRNA and protein in rat proximal tubules and medullary thick ascending limbs (MTAL) using reverse transcription combined with polymerase chain reaction (PCR) and radioligand binding methods. Complementary primers were designed to span cDNA sequences in each of the third intracellular loops of the rat alpha 1B- and alpha 1D-adrenoceptors. Expression of the mRNA of alpha 1B- and alpha 1D-adrenoceptors was first detected in total RNA from whole rat kidney, and the PCR product identity was confirmed by sequencing. Endogenous expression of alpha 1B- and/or alpha 1D-adrenoceptor mRNA was then investigated in microdissected segments of the rat proximal convoluted tubule (S2 segments) and the MTAL. mRNA was reverse-transcribed directly from permeabilized microdissected segments and the resulting cDNA was subjected to PCR with the alpha 1-adrenoceptor primers. In proximal convoluted tubules, amplification of both alpha 1B- and alpha 1D-adrenoceptor mRNA was observed. In MTAL segments, only alpha 1D-adrenoceptor mRNA was detected. We also measured receptor protein using [3H]prazosin in saturation and competition binding experiments. Proximal tubular membranes contained 3.3-fold more alpha 1-adrenoceptor than did MTAL membranes (163 +/- 21 versus 49 +/- 3 fmol/mg of protein). When the alkylating agent chloroethylclonidine (CEC) (10 microM, 10 min) was used to define alpha 1-adrenoceptor subtypes, proximal tubules were found to contain primarily CEC-insensitive (alpha 1A) sites (68 +/- 4%) and MTAL primarily CEC-sensitive sites (75 +/- 3%). Most [3H]prazosin binding sites (72 +/- 2%) in MTAL segments were also sensitive to the alkylating agent SZL-49, consistent with their identification as alpha 1D-adrenoceptors. In competition studies with the antagonists WB4101, 5-methylurapidil, and (+)-niguldipine, both high and low affinity sites were observed in proximal tubules. WB4101 interacted with only one site in MTAL membranes, intermediate in affinity between those sites found in proximal tubules. We conclude that reverse transcription-PCR is a useful method for demonstrating the expression of alpha 1-adrenoceptor subtypes in small amounts of tissue. Results from our experiments suggest that alpha 1A-, alpha 1B-, and alpha 1D-adrenoceptors are all expressed in proximal tubules and that alpha 1D-adrenoceptors are the primary alpha 1-adrenoceptor subtype expressed in MTAL. The distinct anatomical distribution of each of these adrenoceptor subtypes suggests that they serve different functions in the kidney.

Animals↗

PubMed1977

Squirrel monkey retrovirus: an endogenous virus of a new world primate.

Squirrel monkey retrovirus (SMRV) was isolated by cocultivation of squirrel monkey lung cells with canine cells. 3H-labeled 60-70S SMRV RNA, isolated from virus grown in canine cells, hybridized to the same extent and to the same Cot1/2 value to the DNA of all tissues of all squirrel monkeys tested; Cot1/2 values show that SMRV proviral sequences are present in the low repetitive range. No SMRV proviral sequences were detected in tissues from a variety of other New World monkeys, Old World monkeys, or apes. Murine, feline, bovine, and canine cells also contain no detectable SMRV proviral sequences. Competitive molecular hybridization studies revealed no detectable sequence homology between the 60-70S RNAs of SMRV and Mason-Pfizer virus (MPV). The virion-associated DNA polymerase of SMRV is similar to that of MPV in that it has a molecular weight of approximately 80,000 and prefers magnesium as a divalent cation using oligo(dG)-poly(rC) as primer-template. The virion-associated DNA polymerase of SMRV can be clearly distinguished from those of MPV and the mouse mammary tumor viruses, however, by its preference for manganese as a divalent cation in the presence of high salt.

Animals↗

PubMed1995

The roles of microfilament-associated proteins, drebrins, in brain morphogenesis: a review.

The cytoskeleton has been suggested to be one of the important endogenous factors that control neuronal morphogenesis. Analysis of the developmental changes in the protein composition of the brain led to the discovery of novel developmentally regulated actin-binding proteins, drebrins. Drebrins exhibit a number of characteristics that one might expect for an intracellular regulator of neuronal morphogenesis. Drebrin has three isoforms and the mRNA of each isoform is transcribed from a single gene through alternative RNA splicing mechanisms. The expression pattern of each isoform is regulated spatially and temporally in the developing brain. Drebrin and tropomyosin competitively bind to actin filaments, and the exclusion of tropomyosin from actin filaments by overexpression of drebrin in fibroblasts results in the appearance of thick, curving bundles of actin filaments, and the formation of cell processes. Taken together, these data indicate that drebrin is one of the intracellular regulators of the neuronal morphogenesis.

Actins↗

PubMed2004

Poly(A)-binding protein-interacting protein 2, a strong regulator of vascular endothelial growth factor mRNA.

Expression of vascular endothelial growth factor (VEGF) is tightly regulated, particularly at the level of its mRNA stability, which is essentially mediated through the 3'-untranslated region (3'-UTR) of VEGF mRNA. To identify new protein partners regulating VEGF mRNA stability, we screened a cDNA expression library with an RNA probe corresponding to the entire VEGF mRNA 3'-UTR. We identified the "poly(A)-binding protein-interacting protein 2" (PAIP2) as a new VEGF mRNA 3'-UTR interacting protein. By RNA electromobility shift assays, we showed that PAIP2 binds to two distinct regions of a domain encompassing base 1 to 1280 of the VEGF 3'-UTR. Such in vitro interaction was confirmed using cell extracts in which PAIP2 expression is induced by tetracycline (Tet-on cells). Moreover, we demonstrated by RNA affinity purification as well as by ribonucleoprotein complexes immunoprecipitation, that PAIP2 interacts with VEGF mRNA in vivo. Using an in vitro RNA degradation assay, the half-life of VEGF 3'-UTR was found to be increased by overexpressing PAIP2. PAIP2 stabilizes endogenous VEGF mRNA in Tet-on cells, leading to increased VEGF secretion. Moreover, RNAi-mediated knock-down of PAIP2 significantly reduces the steady-state levels of endogenous VEGF mRNA. We also showed, by in vitro protein-protein interactions and co-immunoprecipitation experiments, that PAIP2 interacts with HuR, an already known VEGF mRNA-binding protein, suggesting cooperation of both proteins for VEGF mRNA stabilization. Hence, PAIP2 appears to be a crucial regulator of VEGF mRNA and as a consequence, any variation in its expression could modulate angiogenesis.

3' Untranslated Regions↗

PubMed1999

Interruption of activin A autocrine regulation by antisense oligodeoxynucleotides accelerates liver tumor cell proliferation.

Administration of activin A, a member of the transforming growth factor-beta superfamily inhibits hepatocyte proliferation in vitro and reduces liver mass in vivo. However, a role of endogenous activin A in local growth modulation has not been established in any system. The aim of this study was to examine the production of activin A in the human hepatoma cell line HLF and to explore a possible autocrine role of activin as a cell growth inhibitor by blocking production of endogenous activin using antisense oligodeoxynucleotides. Administration of exogenous activin A suppressed HLF cell growth, and immunoreactive activin A was shown to be produced in the cells at confluency by Western blotting analysis. Cells were exposed to phosphorothioate-modified oligodeoxynucleotides, synthesized with antisense or randomly shuffled base sequences of activin betaA subunit messenger RNA, under serum-free conditions. Uptake of the oligodeoxynucleotides into the cells was confirmed by use of fluorescein isothiocyanate-labeled oligodeoxynucleotides. Administration of antisense oligodeoxynucleotides reduced activin A production as confirmed by both competitive PCR and Western blotting. Activin betaA antisense oligodeoxynucleotides significantly increased cell proliferation compared with controls. These findings are consistent with the existence of an autocrine role of activin A as an inhibitor of hepatocyte proliferation.

Activins↗

PubMed1995

RNA-protein interactions in the ribonucleoprotein T-complexes in a mitochondrial extract from Leishmania tarentolae.

We have investigated protein-RNA interactions and the incorporation of [alpha-32P]UTP into the guide RNA and mRNA components of the 'T-complexes' in a mitochondrial extract from Leishmania tarentolae. The terminal uridylyl transferase-containing complex T-IV is probably involved in the maturation of the 3'-oligo(U) tail of the gRNAs, but the biological function and biochemical nature of the remaining T-complexes is not known. We have found that the relative extent of labeling of the RNA components is dependent on the UTP concentration: at low levels, the main endogenous RNA components labeled are the gRNAs in T-IV; at higher levels, the mRNAs in all of the T-complexes are preferentially labeled. We also show a tentative correlation in the migration pattern of UTP-labeled T-complexes and complexes which bind exogenous labeled RNA. The relative extent of binding to specific complexes is dependent upon the type of RNA. Most of the interactions between the labeled RNAs and proteins can be disrupted by heparin or a large excess of rRNA, but two labeled complexes were resistant to competition. Most of the binding of labeled exogenous gRNA is disrupted by competition with a large excess of rRNA, but predigestion of the extract with micrococcal nuclease and saturation with rRNA uncovered a high affinity complex, which involves at least two proteins interacting with the bound gRNAs. A knowledge of the RNA and protein components may aid in understanding the biological roles of these RNP complexes.

Animals↗

PubMed2001

Aryl hydrocarbon receptor/dioxin receptor in human monocytes and macrophages.

Aryl hydrocarbon receptor (AhR) belongs to the bHLH/PAS transcription factor family and is activated by various polycyclic or halogenated aromatic hydrocarbons, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3-methylcholanthrene (3MC). In the present study, we showed that in U937 cells and human macrophages AhR, with its partner cofactor Arnt, is expressed and CYP1A1 mRNA expression is induced in the presence of AhR ligand 3MC. Moreover, we showed that AhR, associating with Arnt, binds to target DNA sequences and activates transcription. Since part of AhR is activated into DNA binding species in the absence of exogenous ligand and competitive AhR antagonist alpha-naphthoflavone inhibits this activation process with reducing CYP1A1 mRNA expression levels, the presence of endogenous ligand is indicated.

Benzoflavones↗