Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.21.1 (DNase)
 7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carnitine palmitoyltransferase (CPT) regulates the flux of long-chain fatty acids into the mitochondria for subsequent beta-oxidation. A 485 bp segment of the promoter for the gene encoding the 68 kDa CPT was isolated from a rat lambda DASH genomic library using the polymerase chain reaction. The promoter contained a consensus binding sequence for CREB (cyclic AMP response element binding protein) at -153 to -166, and for C/EBP alpha (CCAAT/enhancer binding protein) at -115 to -128. DNAase I footprinting using proteins isolated from rat liver nuclei indicated the presence of several regions of nuclear protein binding, most notably at -95 to -130, at -273 to -295, and at a wide region encompassing -395 to -465. DNAase I footprinting studies with purified CREB and C/EBP alpha confirmed that protein binding to DNA occurred at the sites predicted by the consensus sequences. The segment containing 481 bp of 5' flanking sequence plus 181 bp of untranslated mRNA was ligated to the structural gene for chloramphenicol acetyltransferase (CAT). When this plasmid was transfected into Hep G2 cells, CAT activity was stimulated 7-fold by addition of 1 mM-8-bromo-cyclic AMP (8-Br-cAMP) or co-transfection of the expression vector coding for the catalytic subunit of protein kinase A (PKA). The ability of several known second messengers and transcription factors to stimulate transcription of 68 kDa CPT promoter-CAT reporter was tested in co-transfection experiments. 68 kDa CPT promoter-CAT reporter transcription activity was stimulated 7-fold by addition of 8-Br-cAMP, and this induction was depressed 50% by the addition of phorbol esters. When the 68 kDa CPT promoter-CAT reporter was co-transfected with an expression vector for CREB or C/EBP alpha, transcription was increased 3- and 10-fold respectively. 8-Br-cAMP caused an additional 8-fold induction in the presence of each factor to yield 25- and 80-fold induction respectively. Co-transfection of the expression vector for c-jun also increased the CAT activity driven by the 68 kDa CPT promoter, while co-transfection with the expression vector for c-fos had no effect. When expression vectors for both c-jun and c-fos were co-transfected with the 68 kDa CPT promoter, c-fos depressed the induction seen with c-jun alone.
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PMID:Isolation and characterization of the promoter for the gene coding for the 68 kDa carnitine palmitoyltransferase from the rat. 825 Aug 54

The level of expression of cellular proto-oncogens c-myc and c-fos in rat liver has been studied as a function of protein synthesis rate (cycloheximide dose). Activation of proto-oncogens has been established to be initiated by 50% inhibition of nuclear protein synthesis. This promotes a certain level in chromatin structural rearrangements which is manifested, in particular, in decreasing activity of chromatin cleavage by Ca2+, Mg(2+)-DNAase and increasing degree of chromatin condensation. A role of topoisomerase II in chromatin structural rearrangements during proto-oncogen activation is postulated.
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PMID:[Structural changes of chromatin during proto-oncogene activation by cycloheximide: dose-effect]. 145 95

Transcription factor activator protein 1 (AP-1) is a protein fraction that contains c-fos, c-jun, and several other related proteins. Although this protein fraction can stimulate transcription in vitro, the relative contributions of c-fos and c-jun to the transcriptional effect of AP-1 are not clear. In order to approach this question, we have overexpressed both proteins using a baculovirus-mediated expression system and defined their DNA-binding and transcriptional enhancement activities in vitro. Gel mobility-shift and DNase 1 footprinting assays showed that c-jun protein specifically binds to DNA through an AP-1 binding site. Under the same conditions, no detectable binding of c-fos protein was observed. However, when the DNA binding assays were performed in the presence of both c-jun and c-fos, a marked increase in the affinity of c-jun for the AP-1 site was observed. An AP-1-dependent transcription assay was used to test the capability of both proteins to stimulate correctly initiated RNA synthesis in vitro. Under our conditions, c-jun protein was capable of stimulating specific RNA transcription in an AP-1 site-dependent manner. In contrast, c-fos protein showed no detectable transcriptional activation by itself. However, a transcription assay carried out in the presence of both c-fos and c-jun proteins showed that the c-fos/c-jun complex was more active as a transcriptional regulator than c-jun protein alone. These experimental results indicate that c-fos and c-jun proteins are required to reconstitute full AP-1-dependent transcriptional activation and directly demonstrate that c-fos is a regulator of gene expression.
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PMID:A direct role for c-fos in AP-1-dependent gene transcription. 212 90

As in tumors with c-myc chromosomal translocations, c-myc retrovirus-induced monocyte tumors constitutively express an activated form of c-myc (the proviral gene), whereas the normal endogenous c-myc genes are transcriptionally silent. Treatment of these retrovirus-induced tumor cells with a number of bioactive chemicals and growth factors that are known to induce c-myc expression in cells of the monocyte lineage failed to induce the endogenous c-myc gene. In contrast, the same treatments induced the c-fos gene in both tumors and a control macrophage line. To investigate c-myc suppression further, a normal copy of the human c-myc gene was introduced into tumor and control cell lines by using a retrovirus with self-inactivating long terminal repeats. This transduced normal gene was expressed at equivalent levels in all cells, regardless of the state of endogenous c-myc gene expression, and was strongly induced by agents that induce the normal gene in the control cells. These results indicate that the signal transduction pathways that normally activate the c-myc gene are functional in myc-induced tumor cells and suggest that endogenous c-myc is actively suppressed. An examination of the c-myc locus itself showed that the lack of transcriptional activity correlated with the absence of several prominent DNase I-hypersensitive sites in the 5'-flanking region of the gene but without loss of general DNase sensitivity. Furthermore, analysis of 22 methylation-sensitive restriction enzyme sites in the 5'-flanking region, first exon, and first intron indicated that the silent c-myc genes remained in the same unmethylated state as did actively expressed genes. Thus, c-myc suppression does not appear to result from the most frequently described mechanisms of gene inactivation.
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PMID:Germ line c-myc is not down-regulated by loss or exclusion of activating factors in myc-induced macrophage tumors. 247 87

Two regions of the Epstein-Barr virus BZLF1 trans-activator protein have sequence similarity to the c-fos protein. Part of the similarity corresponds to the region of c-fos which is similar to the DNA binding domain of c-jun and GCN-4. The structure of the exon which contains this region in c-fos and BZLF1 is also highly conserved between the two genes. Complete BZLF1 protein and a C terminal fragment were prepared either as purified fusion proteins or by in vitro translation from a BZLF1 cDNA. Gel retardation and DNase footprinting assays using these proteins show that BZLF1 is a sequence specific DNA binding protein capable of binding to a target sequence which contains a consensus AP-1 site.
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PMID:Epstein-Barr virus BZLF1 trans-activator specifically binds to a consensus AP-1 site and is related to c-fos. 254 Sep 54

Transient transcriptional activation of the c-fos gene following serum stimulation of susceptible cells requires a conserved DNA element located 300 bp 5' to the mRNA cap site. A DNA-binding gel electrophoresis assay was used to detect a protein(s) in HeLa cell nuclear extracts that specifically binds to the 5' activating element. The protein recognizes a region of dyad symmetry within the 5' activating element, defined by binding competition, dimethylsulphate (DMS) interference and DNAase I and DMS protection studies. A single 22 bp synthetic copy of the dyad symmetry element will both compete efficiently for protein binding and restore serum regulation to c-fosH genes that lack the 5' activating element.
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PMID:Identification of a protein-binding site that mediates transcriptional response of the c-fos gene to serum factors. 352 58

Activation of liver Ito cells is characterized by increased proliferation, fibrogenesis, loss of cellular retinoid and change of cell-shape. Here, we have described fundamental differences between freshly isolated Ito cells (FIC) and long-term cultured Ito cells (LTIC). This process of activation correlates with the absence of expression of Pro alpha 1(I) gene in FIC. LTIC expressed abundant transcripts of Pro alpha 1(I) gene. Nuclear run-off experiments showed the inability of FIC to support Pro alpha 1(I) RNA transcription while LTIC transcribed it greater than 5-fold as compared with FIC. Transforming growth factor beta (TGF beta)-treated LTIC had a preferential increase in the rate of Pro alpha 1(I) gene transcription as compared with control LTIC. A human collagen type I promoter-enhancer construct (pCOL-KT) [Thompson, Simkevich, Holness, Kang and Raghow (1991) J. Biol. Chem. 266, 2549-2556] was readily expressed in LTIC but failed to be expressed in FIC. Furthermore, TGF beta treatment of LTIC resulted in an increased expression of pCOL-KT. The deletion of an activator protein-1 (AP-1) binding site (+598 to +604) in the 360 bp enhancer region of pCOL-KT (S360) caused decreased expression of the CAT reporter gene, suggesting that this bonafide AP-1 site can, at least in part, mediate the transactivation effect of TGF beta. Using DNAase I protection, we demonstrate a single foot-print located at +590 to +625 in the S360 fragment; nuclear extracts prepared from TGF beta-treated LTIC exhibited greater activity of these AP-1 binding proteins. Gel mobility assays corroborated and extended the footprinting observation. No AP-1-binding activity was found in the nuclear extracts of FIC. Double-stranded oligonucleotides containing the consensus AP-1 motif were able to compete out the binding; consensus NF-1 motif oligonucleotides failed to do so. The preincubation of nuclear extracts from control and TGF beta-treated LTIC with antibodies against c-jun and c-fos rendered a reduced binding of AP-1 proteins to the target S360 fragment.
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PMID:Activation of Ito cells involves regulation of AP-1 binding proteins and induction of type I collagen gene expression. 781 86

Hepatic transcription of insulin-like growth factor binding protein-1 (IGFBP-1) is rapidly downregulated by growth hormone (GH) which is also known to induce expression of c-fos and c-jun. Co-expression of c-fos or c-jun in rat hepatocytes, individually or together, suppresses IGFBP-1 promoter activity by approximately 60%. When hepatic nuclear extracts from sham-operated, hypophysectomized (hypox) and GH-treated hypox rats were analyzed by DNase-1 footprinting, differences in the protection pattern were identified in three regions of the IGFBP-1 promoter. F1 corresponding to - 660 to - 640 bp showed acute changes in response to GH administration. In additional regions, F2 and F3, representing - 758 to - 748 bp and - 477 to - 447 bp, respectively, differences were apparent between nuclear extracts from the hypox and sham-operated rats. When F1 and F2 were removed by deletion of the region from - 824 to - 557 bp, the GH response was lost but suppression by co-expression of c-fos and c-jun was preserved. A putative AP-1 binding site was present in the F3 footprint region, however removal of F3 did not affect the GH responsiveness. These data indicate that several distinct sequences, other than the putative AP-1 site are involved in mediating the GH effects on IGFBP-1 transcription.
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PMID:Growth hormone suppression of insulin-like growth factor binding protein-1 promoter activity. 1037 14

RNA splicing generates two products in equal molar amounts, mature mRNAs and spliced introns. Although the mechanism of RNA splicing and the fate of the spliced mRNA products have been well studied, very little is known about the fate and stability of most spliced introns. Research in this area has been hindered by the widely held view that most vertebrate introns are too unstable to be detectable. Here, we report that we are able to detect all three spliced introns from the coding region of the Pem homeobox gene. By using a tetracycline (tet)-regulated promoter, we found that the half-lives of these Pem introns ranged from 9 to 29 min, comparable with those of short lived mRNAs such as those encoding c-fos and c-myc. The half-lives of the Pem introns correlated with both their length and 5' to 3' orientation in the Pem gene. Subcellular fractionation analysis revealed that spliced Pem introns and pre-mRNA accumulated in the nuclear matrix, high salt-soluble, and DNase-sensitive fractions within the nucleus. Surprisingly, we found that all three of the spliced Pem introns were also in the cytoplasmic fraction, whereas Pem pre-mRNAs, U6 small nuclear RNA, and a spliced intron from another gene were virtually excluded from this fraction. This indicates either that spliced Pem introns are uniquely exported to the cytoplasm for degradation or they reside in a unique soluble nuclear fraction. Our study has implications for understanding the regulation of RNA metabolism, as the stability of introns and the location of their degradation may dictate the following: (i) the stability of nearby mRNAs that compete with spliced introns for rate-limiting nucleases, (ii) the rate at which free nucleotides are available for further rounds of transcription, and (iii) the rate at which splicing factors are recycled.
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PMID:Localization and stability of introns spliced from the Pem homeobox gene. 1127 82

Degree of nucleolysis has critical significance for isolation of nuclear matrix (NM) specifically enriched in transcribed DNA sequences as demonstrated at the example of inactive (c-fos, c-myc, and Ck) and active (p53, albumin, and 28S rRNA) genes in resting hepatocytes. Optimal degree of nucleolysis features degradation of loop domains of chromatin with preserved relatively uniform molecular weight distribution of DNA. Deviation from these parameters leads to nonspecific fragmentation of chromatin in various gene loci and isolation of NM samples nonspecifically enriched or depleted of transcribed DNA sequences. Under optimal hydrolytic conditions, the transcribed chromatin is more resistant to endogenous DNase attack, which allows selective conservation of its association with the nuclear matrix.
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PMID:[Endogenous DNases as a tool for isolation of nuclear matrix: critical parameters of nucleolysis]. 1473 82


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