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

---

Query: EC:3.1.30.1 (S1 nuclease)
3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examine the influence of the immunoglobulin locus on the expression of the translocated c-myc oncogene in mouse plasmacytomas. The level of c-myc RNA was 30- 35-fold greater in tumor cells than in normal, quiescent B cells. Mitogen stimulation of the lymphocytes with lipopolysaccharide induced a 15-fold increase in c-myc expression per cell to a level that was similar to that in the transcription of the translocated c-myc gene involved initiation from sequences in the first c-myc intron. Abundant RNA transcripts were also found from the noncoding strand of the c-myc intron in most tumor lines. S1 nuclease mapping was used to locate the intronic sequences that are used to initiate the tumor-specific c-myc RNAs. Six different initiation sites within the intron were mapped, none of which have the TATA sequence usually associated with eucaryotic RNA polymerase II promoters. The noncoding strand transcripts were also found to initiate in the c-myc intron. Transcription of the c-myc coding strand was independent of the position of the translocation breakpoint, even when the heavy chain switch and constant regions were deleted.
...
PMID:Transcriptional activation of the translocated c-myc oncogene in mouse plasmacytomas: similar RNA levels in tumor and proliferating normal cells. 632 72

We have established the structure and nucleotide sequence of the 5' end of the human c-myc oncogene, using a cloned genomic fragment isolated from a fetal liver library (clone lambda MC41) and cloned cDNA from the human leukemic cell line K562. The human c-myc oncogene consists of three exons and two introns. Primer extension of the human c-myc mRNA of three different cell lines and S1 nuclease protection experiments served to establish the position of two transcription initiation sites. The splicing site of the first exon-intron boundary was determined by comparative analysis of the sequences of the genomic and cDNA clones. The first exon contains termination codons in all three reading frames and no translation initiation signals, confirming our previous observation that the c-myc mRNA has a long 5' noncoding sequence. This first exon also was found to be utilized in the formation of c-myc mRNAs in a variety of human cell lines.
...
PMID:The structure and nucleotide sequence of the 5' end of the human c-myc oncogene. 657 11

A gene-specific transcription assay was developed that is based on pulse-labeled incorporation of [3H]uridine into nuclear RNA. Transcription is quantified by scintillation counting of [3H]uridine incorporated into nuclear RNA that is protected from S1 nuclease digestion by hybridization with cold gene probes. This assay was dependent upon partial degradation of nuclear RNA and optimization of hybridization and nuclease digestion conditions. To validate this assay, transcription of beta-actin and c-myc genes was measured in two different human cell lines using the incorporation assay in parallel with the nuclear run-off assay. Transcription kinetics of the beta-actin and c-myc genes in serum-stimulated fibrosarcoma HT-1080 cells determined by [3H]uridine incorporation were comparable to that determined by the nuclear run-off method. For beta-actin, there was an approximate 2-fold increase in transcription rate within two hours of stimulation that declined to basal levels by 20 h. The c-myc gene response followed a similar kinetics as for the beta-actin gene except that maximal enhancement was greater at 6-9-fold. The relative transcriptional activities of the beta-actin gene to that of the c-myc gene were virtually identical using the two assay methods. Comparable transcription results using both methods were also observed when beta-actin and c-myc gene transcription were measured in log-phase HL-60 leukemia cells.
...
PMID:Measurement of gene-specific transcription by nuclease protection of pulse-labeled nuclear RNA. 769 98

The cholecystokinin-B and gastrin receptor is encoded by a single gene composed of five exons and spanning over 10 kilobases on human chromosome 11p 15.5-->15.4. Exon 4 has two possible alternative splicing donor sites that seem to be conserved in other species such as the canine, rat, Mastomys, and mouse. They could generate two receptor isoforms (short- and long-form), which differ in their putative third cytoplasmic domain of the serpentine G-protein-coupled receptors. In the present study, we examined whether an alternative splicing is operated in a tissue-specific manner and whether two receptor isoforms have functional differences. RNase-protection assay and S1 nuclease mapping demonstrated the preferential expression of the short-form in the human brain as well as the digestive organs, stomach and pancreas. The two putative isoforms of the cholecystokinin-B/gastrin receptor expressed in mouse fibroblasts showed the same characteristics in their ligand-bindings, the major signal transduction such as phosphoinositides production, cytoplasmic Ca2+ increase, tyrosine phosphorylation of focal adhesion kinase, activation of mitogen-activated protein kinase, and the induction of early-responsive genes such as c-fos, c-myc, and c-jun. Moreover, the ligand-dependent trophic effect was seen in both receptor isoforms. Taken together with the absence of tissue-specific expression of two receptor isoforms, these results suggest a species-specific dominant splice donor site in exon 4 of the human receptor gene.
...
PMID:Functional characterization of two cholecystokinin-B/gastrin receptor isoforms: a preferential splice donor site in the human receptor gene. 784 14

Analysis by the circular permutation assay of the human epsilon-globin gene region revealed that the DNA bend sites were located every 682.5 +/- 132.0 base pairs on average, separating the region into domains. Among 10 major and 1 minor bend sites mapped in the region, the transcription initiation and termination sites of the epsilon-globin gene were located close to the bend sites, and the first and the second exons of the epsilon-globin gene were separated from the third exon by another site. The bend sites were also located anterior to the two Alu family sequences. Short poly(dA).poly(dT) tracts typical for DNA bending were not always present in the sites. Fine mapping of a bend site having no poly(dA).poly(dT) tracts with concatenated oligonucleotides and analysis by S1 nuclease nicking assay indicated that the unusual structure, a base slippage or a partial triplex DNA structure, formed by a polypurine.polypyrimidine sequence in the region is the basis of bending. The bend sites were mapped in the promoter region (within approximately 300 base pairs from the cap site) of the human beta-globin and in c-myc and erythropoietin receptor genes, as well as in the mouse beta maj-globin gene. The conservation and the periodicity of the bend sites in the noncoding region suggest the active role of the sites that is a signal for nucleosome phasing.
...
PMID:Periodicity of DNA bend sites in human epsilon-globin gene region. Possibility of sequence-directed nucleosome phasing. 807 50

In contrast to small-cell lung cancer, few data are available on the role of oncogene overexpression in non-small-cell lung cancers (NSCLC). To determine the prevalence and extent of the transcriptional activation of cancer genes in NSCLC we investigated the level of mRNA of the three important cellular oncogenes--erbB2, Ki-ras, and c-myc--in 39 surgically or endoscopically obtained tumor samples and 24 samples of normal bronchopulmonary tissue taken from the same patients. Tissue RNA was prepared and the specific mRNA analyzed by the highly sensitive nuclease S1 protection assay. Oncogene mRNA in the tumors was quantified by comparison with the homogeneously weak signals in normal lung tissue preparations with densitometry. The presence of two- to four-fold excess RNA was defined as moderate and a greater than fourfold RNA amount as strong gene overexpression. In contrast to normal tissue the oncogene mRNA amount varied considerably among tumors, showing increases up to 64-fold in erbB2, 13-fold in Ki-ras, and 57-fold in c-myc. Moderate and strong (in brackets) mRNA overexpression occurred with 33% (33%) in erbB2, 36% (18%) in Ki-ras, and 18% (23%) in c-myc. Simultaneous overexpression of two genes was observed with 41% and increased mRNA of all genes tested with 20% of the NSCLC samples. Augmented oncogene mRNA was observed most frequently in large-cell carcinoma. The c-myc overexpression was significantly more prevalent in large-cell cancer than in adenocarcinoma. Tumor differentiation was negatively correlated with c-myc mRNA amounts.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Oncogene overexpression in non-small-cell lung cancer tissue: prevalence and clinicopathological significance. 818 64

Much of our knowledge about the regulation of the c-myc proto-oncogene expression has come from studies of c-myc gene expression in several well defined ex vivo systems, including differentiation systems and tumor cells. However, very few investigations have been performed to determine the factors and cis-acting sequences that regulate c-myc expression in vivo. In order to obtain information on the sequences required to regulate c-myc gene transcription from the two major P1 and P2 initiation sites in the mouse, we have generated several constructs containing human or murine c-myc genomic sequences with various 5' flanking sequences and derived corresponding transgenic mice. A sensitive S1 nuclease protection assay was performed to analyse and to compare transgene expression with that of the endogenous c-myc mRNA, either in adult organs, or during development. None of the transgenic mice expressed the construct appropriately, although several strains exhibited unexpected expression most probably due to position effects. Our results indicate that the cis-acting elements described to regulate c-myc expression ex vivo are not sufficient to drive the correct expression of c-myc gene in vivo and strongly suggest that additional regulatory elements located upstream from -3500 (with respect to mouse P1 promoter) and downstream 1500 bp from polyadenylation sites are required.
...
PMID:The cis-acting elements known to regulate c-myc expression ex vivo are not sufficient for correct transcription in vivo. 829 Feb 63

Activation of the murine c-myc promoter by murine c-Myb protein was examined in several cell lines by using a transient expression system in which Myb expression vectors activate the c-myc promoter linked to a chloramphenicol acetyltransferase reporter gene or a genomic beta-globin gene. S1 nuclease protection analyses confirmed that the induction of c-myc by c-Myb was transcriptional and affected both P1 and P2 start sites in a murine T-cell line, EL4, and a myelomonocytic line, WEHI-3. Mutational analyses of the c-myc promoter revealed that two distinct regions could confer Myb responsiveness in two T-cell lines, a distal site upstream of P1 and a proximal site within the first noncoding exon. In contrast, only the proximal site was required for other cell lineages examined. Five separate Myb-binding sites were located in this proximal site and found to be important for c-Myb trans activation. DNA binding was necessary for c-myc activation, as shown by the loss of function associated with mutation of Myb's DNA-binding domain and by trans-dominant repressor activity of the DNA binding, trans-activation-defective mutant. The involvement of additional protein factors was addressed by inhibiting protein synthesis with cycloheximide in a conditional expression system in which the activity of presynthesized Myb was under the control of estrogen. These experiments indicate that de novo synthesis of additional proteins was not necessary for c-myc trans activation. Together these data reveal two cell lineage-dependent pathways by which c-Myb regulates c-myc; however, both pathways are mechanistically indistinguishable in that direct DNA binding by Myb is required for activating c-myc whereas neither de novo protein synthesis nor other labile proteins are necessary.
...
PMID:Mechanism of c-myc regulation by c-Myb in different cell lineages. 847 46

We have previously shown that in vivo the steady-state level of c-myc mRNA in different quiescent organs and its induction in the early stages of hepatic regeneration and after inhibition of protein synthesis are mainly controlled by post-transcriptional mechanisms. In order to localize the target sequences for these mechanisms, transgenic lines expressing various versions of the human c-myc proto-oncogene have been constructed. To avoid all possible transcriptional controls due to the c-myc 5' regulatory region, the c-myc genomic sequences were fused to MHC H-2Kb class I regulatory sequences, which have previously been shown to be able to drive reporter gene expression in most adult tissues. The transgenes contained either all human c-myc genomic sequences or were deleted for one of the sequences which have been shown in in vitro experiments to play a role in c-myc mRNA stabilization, in particular exon 1, intron 1 and the 3' non-coding region. Several independent transgenic lines were derived for each construct. Using S1 nuclease protection analysis, we have monitored H-2K, mouse c-myc and transgene mRNA expression in several quiescent adult organs, at the start of liver regeneration and after inhibition of protein synthesis in each transgenic line. Our results indicate that the 5' non-coding sequences, including exon 1 and intron 1, and the 3' untranslated region are all dispensable in the different aspects of c-myc post-transcriptional regulation.
...
PMID:The 5' and 3' non-coding sequences of the c-myc gene, required in vitro for its post-transcriptional regulation, are dispensable in vivo. 851 Sep 35

In vivo short term (2 h) insulin-regulated gene expression was examined in skeletal muscle of persons with differing insulin sensitivities. Nine genes were analyzed by a S1 nuclease protection assay with multiple probes (multiple S1 nuclease protection assay) to allow the simultaneous examination of RNA abundances from the multiple genes. In insulin-sensitive individuals, 5 of these 9 genes were insulin responsive. RNA from the proto-oncogenes c-Ha-ras, c-myc, and c-src transiently increased 2- to 4-fold within 30 min of insulin infusion. In addition, the RNA abundance of myf-5, a muscle specific differentiation factor, increased 3-fold with a time course similar to that of c-Ha-ras, c-myc, and c-src. In contrast, type 1 protein phosphatase alpha (PPP1A) RNA levels decreased by 50% within 30 min. In insulin-resistant individuals, the RNA levels of c-Ha-ras and myf-5 did not increase, whereas c-src RNA did increase within 30 min of insulin infusion. RNA encoding c-myc transiently increased in both groups; however, this response was lower in insulin-resistant individuals than in insulin-sensitive individuals in a pattern similar to c-Ha-ras and myf-5. PPP1A RNA levels slightly increased in insulin-resistant individuals. In both insulin-sensitive and insulin-resistant persons, RNA quantities of GLUT4, c-jun, c-fos, and the insulin receptor did not change over the period of insulin infusion. However, overall RNA levels of the insulin receptor and c-jun were lower in insulin-resistant individuals.
...
PMID:Insulin regulation of multiple ribonucleic acid species in human skeletal muscle in insulin-sensitive and insulin-resistant subjects. 863 61


<< Previous 1 2 3 4 5 Next >>

---