Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor necrosis factor (TNF) is a pleiotropic biomodulator and an important inducer of certain pathophysiologic immune reactions such as granuloma formation, cachexia, and septic shock. The production of TNF by astrocytes, which may figure prominently in the development of immune responses within the central nervous system, is subject to post-transcriptional regulation. We have previously shown that in virus-stimulated astrocytes, inhibition of protein kinase C results in a specific, 10-fold decrease in TNF mRNA half-life. Here we show that the decay of TNF messages induced in the macrophage-like cell line RAW 264.7 by either virus or lipopolysaccharide was subject to similar regulation, and that this pathway influenced the amount of TNF protein released by stimulated cells. Using a modified RNase protection assay, we demonstrate that inhibition of protein kinase C significantly enhanced the rate of poly(A) removal from TNF mRNA, thus facilitating an early event in the process of mRNA degradation.
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PMID:Poly(A) removal is the kinase-regulated step in tumor necrosis factor mRNA decay. 131 Mar 8

The in vitro expression of bovine leukemia virus (BLV) in short-term cultured bovine peripheral blood mononuclear cells (PBMC) is associated with increased spontaneous lymphocyte blastogenesis. The purpose of this study was to determine whether intracellular pathways responsible for antigen- or mitogen-induced lymphocyte blastogenesis were also responsible for induction of BLV expression. The protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-3-methylpiperazine dihydrochloride (3-methyl H7) decreased blastogenesis in a dose-dependent manner, as measured by [3H]thymidine incorporation, in unstimulated, lipopolysaccharide-stimulated and phorbol ester (PMA)-stimulated BLV-infected PBMC. Similarly, 3-methyl H7 decreased BLV expression, as measured by production of gp51 envelope antigen or p24gag antigen, in BLV-infected PBMC under the same conditions. Using an RNase protection assay, the inhibition of BLV expression by 3-methyl H7 was shown to be due to decreased transcriptional activity. The cyclic GMP-dependent protein kinase and cyclic AMP-dependent protein kinase inhibitor N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA1004) did not inhibit either BLV expression or blastogenesis of BLV-infected bovine PBMC. Additional evidence for the PKC-dependent expression of BLV was obtained by using a persistently BLV-infected B-lymphocyte cell line, NBC-13. Activation of PKC by PMA in NBC-13 cells increased BLV expression. 3-methyl H7 decreased the PMA-induced expression of BLV in NBC-13 cells in a dose-dependent manner, whereas HA1004 did not inhibit this expression. These results identify a mechanism for the induction of BLV expression through PKC activation and therefore indicate that latency and replication of BLV is controlled by normal B-lymphocyte intracellular signaling pathways.
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PMID:Inhibition of protein kinase C results in decreased expression of bovine leukemia virus. 131 12

The expression of the beta isoenzyme for protein kinase C is regulated developmentally and in response to inducers of cell differentiation (such as phorbol esters and 1 alpha,25-dihydroxyvitamin D3). The 5' segment of the gene for protein kinase C beta was cloned from a human leukocyte genomic library in EMBL3 bacteriophage. This segment of the gene (greater than 54 kilobases in length) encompassed the coding sequence for the amino-terminal regulatory domain of the enzyme, the 5'-untranslated region, and the 5'-flanking region. Initiation of transcription was identified by S1 nuclease analysis and confirmed by RNase protection analysis at 197 base pairs 5' of the initiator ATG. Sequence analysis of the 5'-flanking region revealed it to be extremely G+C-rich (> 80%) with many features of a CpG island. Comparison of sequence with known cis-regulatory motifs disclosed a number of potential regulatory elements including an octamer binding motif at -76, Sp1-binding sites at -94 and -63, E boxes at -110, -26, and +18, an AP-1 site at -442, and an AP-2 site at -330. To demonstrate promoter activity, a 630-base pair fragment extending from -587 to +43 was subcloned in front of a promoterless luciferase gene. This fragment was able to drive the expression of luciferase in transient transfections of human hematopoietic cells. Deletion analysis demonstrated that a fragment -111 to +43 was necessary and sufficient for promoter activity; this fragment did not contain TATA or CAAT motifs. The promoter was stimulated 8-20-fold by phorbol esters accounting for the previously observed transcriptional activation of protein kinase C beta. This phorbol ester responsiveness was conferred by the basal promoter (-111 to +43) and was independent of the AP-1 site. These results define a novel mechanism of protein kinase C autoregulation at a transcriptional level.
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PMID:Cloning and characterization of the major promoter of the human protein kinase C beta gene. Regulation by phorbol esters. 140 Mar 96

In human breast carcinoma MCF-7 cells, phorbol diesters inhibit proliferation and induce cell maturation. We investigated the involvement of TGF-beta 1 in the PCK-mediated inhibition of breast cancer cell proliferation. Using an RNase protection assay, we showed that TPA induced a dose-dependent increase in levels of TGF-beta 1 mRNA that paralleled the inhibitory effect on MCF-7 proliferation. Similar results were obtained with another TPA-sensitive breast cancer cell line (BT-20). TPA did not increase TGF-beta 1 mRNA levels in the MCF-7:RPh-4 and T47D cell lines, which are both insensitive to the growth inhibitory effects of phorbol esters. In addition, the increase in TGF-beta 1 mRNA level was not observed after treatment of the MCF-7 cell with other inducers of cell differentiation such as forskolin, DMF, HMBA and sodium butyrate. The induction of TGF-beta 1 mRNA by TPA along with its inhibitory effect on cell proliferation suggests that TGF-beta 1 mediates, at least in part, the inhibitory effect of PKC activation.
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PMID:[Regulation by protein kinase C of TGF-beta 1 expression in cultured cells of breast adenocarcinoma]. 142 93

Calcyclin is a member of the S-100 family of calcium-binding proteins, whose expression is enhanced when quiescent cells are exposed to mitogenic signals. The function of calcyclin is unknown, but it is thought to be involved in modulating the intracellular calcium concentration following mitogenic stimuli. Since activation of protein kinase C (PKC) also occurs following stimulation of quiescent cells by a variety of mitogens, we have investigated the relationship between calcyclin expression and PKC activation in three human endometrial adenocarcinoma cell lines. The addition of 10(-7) M 4 beta-phorbol 12-myristate 13-acetate (PMA) to HEC-50 and HEC-1B cell cultures resulted in a change in cell morphology, an inhibition of proliferation, an increase in calcyclin transcription rate, and an increase in calcyclin mRNA and calcyclin protein levels. In contrast, PMA had no effect on cell morphology or cell proliferation in the Ishikawa adenocarcinoma cell line but enhanced calcyclin expression. Another bioactive phorbol ester had the same effect, whereas the calcium ionophore A23187 and the non-phorbol-ester-type tumor promoter thapsigargin had no effect on calcyclin expression. The effect of PMA on calcyclin expression was blocked by the simultaneous addition of the PKC inhibitor staurosporine and by protein synthesis inhibition with cycloheximide. RNase protection assays and primer extension analysis demonstrated that PMA enhanced transcription from all three of the previously identified transcription start sites in the calcyclin gene. These data clearly demonstrate a dissociation between calcyclin expression and cellular proliferation and suggest that the enhanced calcyclin expression which is seen in quiescent cells following mitogenic stimuli may result from activation of the PKC system.
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PMID:Differential effects of phorbol esters on proliferation and calcyclin expression in human endometrial carcinoma cells. 146 12

We have established an RNase protection method to quantify the expression of mRNA for the human protein kinase C (PK-C) isoforms alpha, beta 1, beta 2, and gamma. This was used to investigate whether each isoform is differentially expressed during the differentiation of hematopoietic cells. Myeloid and lymphoid cells express PK-C alpha, beta 1, and beta 2 mRNAs in various proportions. PK-C gamma mRNA was detected in human brain, but not in hematopoietic cells. PK-C alpha mRNA decreases as HL-60 cells mature to a neutrophil phenotype in response to retinoic acid, but its abundance does not change during monocytic differentiation in response to vitamin D3. PK-C alpha mRNA and protein were undetectable in peripheral blood neutrophils, but are present in monocytes. The mRNAs for PK-C beta 1 and beta 2 isoforms increase during HL-60 differentiation and are expressed in both neutrophils and monocytes. Therefore, the PK-C alpha isoform is specifically down-regulated during human neutrophil terminal differentiation. These data suggest that mature neutrophil functions do not require the PK-C alpha isoform.
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PMID:Down-regulation of human protein kinase C alpha is associated with terminal neutrophil differentiation. 161 Oct 98

Protein phosphorylation is considered an early cellular mechanism of signal transduction by surface immunoglobulins (sIg) and other receptors of B cells. Using intact human peripheral blood B cells of young subjects labeled with orthophosphate, increased phosphorylation levels of serine/threonine and tyrosine substrates were demonstrated on indicator phosphoproteins corresponding to the CD20 isoforms and microtubule-associated protein 2 kinase after cross-linking sIg and costimulation with phorbol diesters. By contrast, stimulated B cells from certain elderly subjects displayed substantial alterations in the phosphorylation patterns of serine/threonine or tyrosine indicator phosphoproteins. Also, age-related impairments in sIg stimulated mobilization of cytosolic protein kinase C (PKC) enzymatic activity and in cytosolic calcium [Ca2+]i responses of B cells were observed with the altered phosphorylation reactions. Comparison of the substrate phosphorylation profiles to the proliferative responses of stimulated B cells from individual elderly subjects suggested a model of signal transduction in which differing stimuli have different dependencies on phosphorylation reactions. Diminished proliferative responses after sIg ligation coincided with decreased phosphorylations of either tyrosine or serine/threonine indicator substrates. However, the decreased proliferative responses of B cells from elderly subjects with substantial reductions of tyrosine phosphorylation after sIg ligation were enhanced by the direct stimulation of serine/threonine kinase activity with phorbol diesters or CD40 ligation. Experiments with kinase inhibitors evaluated the relative dependency of different B cell stimuli on tyrosine and serine/threonine phosphorylation reactions. The proliferative responses of normal B cells to sIg ligation were quite sensitive to the tyrosine kinase inhibitor genistein whereas those observed following costimulations with phorbol diesters or CD40 ligation were more resistant. However, treatment of B cells with H7, an inhibitor of PKC activity, led to a more uniform reduction of B-cell responses after different stimuli. Results from RNase protection assays of c-myc expression also suggested that different B-cell stimuli might utilize distinct intracellular signaling pathways. Both the type of stimuli and mode of sIg ligation were important in determining the stimulated levels of c-myc mRNA expression. Thus, the current findings suggest that age-related defects are present in human B cell signaling pathways as reflected by tyrosine and serine/threonine phosphorylation reactions. Also, these age-related defects can coexist with altered mobilization of PKC enzymatic activity and with alterations in [Ca2+]i and proliferative responses.
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PMID:Signal transduction in human B cells during aging: alterations in stimulus-induced phosphorylations of tyrosine and serine/threonine substrates and in cytosolic calcium responsiveness. 180 9

Rapid stimulation of c-fos transcription by many agonists requires the serum response element (SRE), which binds at least two distinct nuclear proteins, p67SRF and p62TCF. Using nuclear protein extracts from 1321-N1 human astrocytoma cells, we investigated ligand-induced changes in binding of these proteins to SRE probes. In these cells c-fos mRNA expression can be induced by epidermal growth factor (EGF) through protein kinase C-independent pathways and by phorbol esters through protein kinase C. We detected two DNA-protein complexes that formed specifically with the SRE (bands 1 and 2). Band 2 formation was increased 4-6 min after stimulation with EGF as well as serum and phorbol esters; this peaked at 10-30 min and returned to basal levels by 60 min. Induction of band 2 formation preceded the onset and peak accumulation of c-fos mRNA (15 and 30 min after EGF stimulation, respectively) and its return to basal levels (by 1-2 h). Band 2 formation was also increased A431 cells stimulated with EGF and in HeLa and Swiss-3T3 cells stimulated with serum. We found that band 1 contained p67SRF bound to the SRE; band 2 contained p67SRF and a second protein. Gel shift analyses using [35S]methionine-labeled p67SRF and nonradioactive DNA probes suggested that hormone treatment most likely modified the second protein component of band 2. Transient transfection of 1321-N1 cells with plasmids containing point mutations that prevented band 2 formation in vitro also abolished induction of c-fos transcription in vivo as assayed by RNase protection analysis. Thus, hormone-stimulated formation of the protein-DNA complex represented by band 2 may be involved in the activation of c-fos transcription.
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PMID:Epidermal growth factor and other mitogens induce binding of a protein complex to the c-fos serum response element in human astrocytoma and other cells. 190 75

The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the regulation of the estrogen receptor (ER) was investigated in this study. After treatment with 100 nM TPA the concentration of receptor protein was measured using an enzyme immunoassay. By 24 h the receptor protein declined by about 80% from a level of approximately 236 fmol of ER/mg of protein in control cells to 50 fmol of ER/mg of protein in cells treated with TPA. Similar results were obtained with an estrogen receptor ligand binding assay. After removal of TPA, the level of ER returned to control values. 4-alpha-Phorbol, a compound related to TPA, had no effect on ER. The effects of TPA on ER expression appear to be mediated by activation of protein kinase C as H-7, an inhibitor of protein kinase C, blocks these effects. In addition to the effect on ER protein, TPA treatment also resulted in a decrease in the steady-state level of ER mRNA as determined by a RNase protection assay. The metabolic inhibitor cycloheximide was unable to prevent the TPA-induced decrease in ER mRNA. Transcription run-off experiments demonstrated that TPA had no effect on ER gene transcription. A half-life study demonstrated that TPA decreased ER mRNA half-life by a factor of 6 from approximately 4 h in control cells to 40 min in TPA-treated cells. These data suggest that the decline in ER expression is mediated by post-transcriptional destabilization of ER mRNA.
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PMID:Post-transcriptional destabilization of estrogen receptor mRNA in MCF-7 cells by 12-O-tetradecanoylphorbol-13-acetate. 191 23

12-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of U937 promonocytes leads to a 30-fold increase in transforming growth factor beta 1 (TGF-beta 1) gene expression, and this effect results from a stabilized mRNA. Similar up-regulation was detected in TPA-treated K562 erythroblasts but was absent from cell lines that do not differentiate in response to TPA. Related studies in vitro showed that postnuclear extracts of U937 promonocytes contain a ribonuclease system that degrades TGF-beta 1 mRNA selectively and that this system is completely blocked by prior treatment of the cells with TPA. These data identify a new mechanism for regulating TGF-beta 1 mRNA levels and allow us to establish the overall basis for control of TGF-beta 1 gene expression by activation of protein kinase C. Our results also provide a new basis for understanding the long-term up-regulation of TGF-beta 1 gene expression that can accompany hematopoietic cell differentiation.
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PMID:A phorbol ester-regulated ribonuclease system controlling transforming growth factor beta 1 gene expression in hematopoietic cells. 223 28


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