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

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A unique form of nucleoplasmic and cytoplasmic protein glycosylation, O-linked GlcNAc, has previously been detected, using Gal transferase labeling techniques, on a myriad of proteins (for review see Hart, G. W., Haltiwanger, R. S., Holt, G. D., and Kelly, W. G. (1989a) Annu. Rev. Biochem. 58, 841-874), including many RNA polymerase II transcription factors (Jackson, S. P., and Tjian, R. (1988) Cell 55, 125-133). However, virtually nothing is known about the degree of glycosylation at individual sites, or, indeed, the actual sites of attachment of O-GlcNAc on transcription factors. In this paper we provide rigorous evidence for the occurrence and locations of O-GlcNAc on the c-fos transcription factor, serum response factor (SRF), expressed in an insect cell line. Fast atom bombardment mass spectrometry (FAB-MS) of proteolytic digests of SRF provides evidence for the presence of a single substoichiometric O-GlcNAc residue on each of four peptides isolated after sequential cyanogen bromide, tryptic, and proline specific enzyme digestion: these peptides are 306VSASVSP312, 274GTTSTIQTAP283, 313SAVSSADGTVLK324, and 374DSSTDLTQTSSSGTVTLP391. Using an array of techniques, including manual Edman degradation, aminopeptidase, and elastase digestion, together with FAB-MS, the major sites of O-GlcNAc attachment were shown to be serine residues within short tandem repeat regions. The highest level of glycosylation was found on the SSS tandem repeat of peptide (374-391) which is situated within the transcriptional activation domain of SRF. The other glycosylation sites observed in SRF are located in the region of the protein between the DNA binding domain and the transcriptional activation domain. Glycosylation of peptides (274-283) and (313-324) was found to occur on the serine in the TTST tandem repeat and on serine 316 in the SS repeat, respectively. The lowest level of glycosylation was recovered in peptide (306-312) which lacks tandem repeats. All the glycosylation sites identified in SRF are situated in a relatively short region of the primary sequence close to or within the transcriptional activation domain which is distant from the major sites of phosphorylation catalyzed by casein kinase II.
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PMID:Localization of O-GlcNAc modification on the serum response transcription factor. 151 32

A general transcription factor IID which binds to the TATA box promoter element on RNA polymerase II genes regulates and initiates eukaryotic mRNA synthesis. A quantitative polymerase chain reaction procedure was developed and the human transcription factor IID (hTFIID) transcript was measured in normal human tissues, lung carcinomas, lung carcinoma cell lines, and breast carcinomas. In some normal tissues such as liver, fetal lung, and placenta, relatively low to moderate levels of hTFIID mRNA were detected. In contrast, hTFIID transcript was highly expressed in nearly all solid lung carcinomas and cell lines including both small cell lung cancer and non-small cell lung cancer. hTFIID mRNA was present to a greater extent in small cell lung cancer than non-small cell lung cancer in solid tumors and cell lines. In solid carcinomas of breast, overexpression of hTFIID was also detected. A serum induction study using a serum-starved small cell lung cancer cell line, Lu134BS, indicated hTFIID transcription to be rapidly induced at 15 min following stimulation and its response essentially similar to that of protooncogene, c-fos. These results indicate the involvement of the expression of the general transcription factor hTFIID in lung and breast carcinoma, such as being associated with poor differentiation and high mitotic activity.
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PMID:A general transcription initiation factor, human transcription factor IID, overexpressed in human lung and breast carcinoma and rapidly induced with serum stimulation. 172 4

A strong block to the elongation of nascent RNA transcripts by RNA polymerase II occurs in the 5' part of the mammalian c-fos proto-oncogene. In addition to the control of initiation, this mechanism contributes to transcriptional regulation of the gene. In vitro transcription experiments using nuclear extracts and purified transcription templates allowed us to map a unique arrest site within the mouse first intron 385 nucleotides downstream from the promoter. This position is in keeping with that estimated from nuclear run-on assays performed with short DNA probes and thus suggests that it corresponds to the actual block in vivo. Moreover, we have shown that neither the c-fos promoter nor upstream sequences are absolute requirements for an efficient transcription arrest both in vivo and in vitro. Finally, we have characterized a 103-nucleotide-long intron 1 motif comprising the arrest site and sufficient for obtaining the block in a cell-free transcription assay.
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PMID:Sequence requirements for premature transcription arrest within the first intron of the mouse c-fos gene. 190 50

Genes of higher eucaryotic cells are considered to show only a limited response to nutritional stress. Here we show, however, that omission of a single essential amino acid from the medium caused a marked rise in the mRNA levels of c-myc, c-jun, junB and c-fos oncogenes and ornithine decarboxylase (ODC) in CHO cells. There was no general accumulation of mRNAs in amino acid-starved cells, since the gamma-actin, beta-tubulin, protein kinase C, RNA polymerase II, and glyceraldehyde-3-phosphate dehydrogenase mRNAs and the total poly(A)+ mRNA were not increased. The levels of c-myc, ODC, and c-jun mRNAs were elevated more by amino acid starvation than by inhibition of protein synthesis with cycloheximide, which is known to increase the levels of these mRNAs. Importantly, however, cycloheximide present during amino acid starvation reduced the rise in the levels of the mRNAs down to the level obtained with cycloheximide alone. This implies that protein synthesis is required for the accumulation of c-myc, ODC, and c-jun mRNAs in amino acid-deprived cells. The junB and c-fos mRNAs, instead, were increased to the same extent or less by amino acid starvation than by cycloheximide treatment. The accumulation of the c-myc mRNA in amino acid-starved cells was due to both stabilization of the mRNA and increase of its transcription. The rise in the c-jun mRNA level seemed to be caused merely by stabilization of the mRNA. Further, despite the inhibition of general protein synthesis, amino acid starvation led to an increase in the synthesis of c-myc polypeptide. The results suggest that mammalian cells have a specific mechanism for registering shortages of amino acids in order to make adjustments compatible with cellular growth.
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PMID:Deprivation of a single amino acid induces protein synthesis-dependent increases in c-jun, c-myc, and ornithine decarboxylase mRNAs in Chinese hamster ovary cells. 212 33

The functional association between DNA topoisomerase I and gene activity has been analyzed using the tightly regulated c-fos proto-oncogene, which undergoes rapid transitions between active and inactive states of transcription. We show that the topoisomerase I inhibitor camptothecin can be used to measure topoisomerase I activity throughout the transcription cycle of the c-fos gene. Upon induction of c-fos transcription in the presence of camptothecin, topoisomerase I cleavages spread through the gene in the 5' to 3' direction and concomitantly transcriptional elongation is retarded. Parallel kinetic measurements of RNA polymerase II activity and topoisomerase I activity demonstrate a quantitative and temporal link between the two enzymes. Our results argue that topoisomerase I quantitatively relieves the torsional consequences of transcriptional elongation in intact cells.
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PMID:Rapid induction of c-fos transcription reveals quantitative linkage of RNA polymerase II and DNA topoisomerase I enzyme activities. 215 54

A new affinity chromatographic procedure for the separation of transcriptionally active nucleosomes has been used to study the changes that take place in chromatin structure along the c-fos and c-myc genes when RNA synthesis is inhibited. Mercury-affinity chromatography separates the sulfhydryl-reactive nucleosomes of transcriptionally active genes from the compactly beaded, non-reactive nucleosomes of transcriptionally inert DNA sequences. The new procedure also discriminates between nucleosomes that have "unfolded" to reveal the previously shielded SH groups of histone H3 and nucleosomes that bind to the mercury column because of their association with thiol-containing non-histone proteins located in the transcription unit. Both classes of Hg-bound nucleosomes contain the c-fos and c-myc sequences, but only when they are being transcribed. We compared the effects of alpha-amanitin and actinomycin D on the transcription of c-fos and c-myc with the effects of each inhibitor on the distribution of the corresponding oncogenic DNA sequences in the chromatographically separated nucleosome fractions. It was found that the inhibition of RNA polymerase II by alpha-amanitin (added at the peaks of c-fos or c-myc expression in serum-stimulated BALB/c 3T3 cells) resulted in a rapid loss of affinity of the oncogene-containing nucleosomes for the mercury column. There was no corresponding effect on the mercury-binding properties of nucleosomes containing 28 S ribosomal gene sequences, which continue to be transcribed by amanitin-resistant RNA polymerase I. Therefore, the binding of the c-fos and c-myc nucleosomes to the mercury column seems to depend upon reversible structural changes associated with their transcription. Surprisingly, there was no corresponding loss of affinity of the c-fos and c-myc nucleosomes for the mercury column when actinomycin D was employed to inhibit RNA synthesis, despite the fact that transcription of both genes had been arrested abruptly. Measurements of [3H]actinomycin D binding show its preferential intercalation into the transcriptionally active nucleosomes. We suggest that the intercalation of actinomycin D into the DNA of active nucleosomes can lock the transcription complex into an "unfolded" but potentially active configuration. This was confirmed by run-off transcription assays showing a restoration of c-fos and c-myc RNA synthesis when actinomycin D was displaced by proflavine.
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PMID:Reversible and irreversible changes in nucleosome structure along the c-fos and c-myc oncogenes following inhibition of transcription. 232 30

RNA polymerase II seems to be prone to stop at intrinsic pause sites, thus introducing a further potential level of regulation. It was recently shown that RNA polymerase II was held at the P2 promoter of c-myc gene. We confirmed the presence of engaged polymerases in the murine fibroblastic Ltk- and pre-B lymphoid 70Z3 cell lines. High resolution run-on analysis and in vivo permanganate-dependent footprinting showed that this holds true for the c-fos gene in unstimulated cells where a strong block to transcription elongation was evidenced. In contrast to what was observed in the c-myc gene, an even more intense signal was observed in run-on experiments downstream to the promoter, on a c-fos oligonucleotide including position +385 where an in vitro transcription arrest site was previously mapped. Genomic footprinting of DNA from intact cells and isolated nuclei confirmed the involvement of several thymidines belonging to a T-rich stretch in a melted region which was not detected upon polymerase release. In order to observe a short abortive c-fos transcript accumulating in vivo we resorted to microinjection of c-fos templates in Xenopus oocytes where transcripts were stable.
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PMID:Elongation and premature termination of transcripts initiated from c-fos and c-myc promoters show dissimilar patterns. 783 31

Human diploid fibroblasts undergo a limited number of population doublings in vitro and are used widely as a model of cellular aging. Despite growing evidence that cellular aging occurs as a consequence of altered gene expression, little is known about the activity of transcription factors in aging cells. Here, we report a dramatic reduction in the ability of proteins extracted from the nuclei of near-senescent fibroblasts to bind the serum response element which is necessary for serum-induced transcription of the c-fos gene. In contrast, the activities of proteins binding to the RNA polymerase core element, TATA, as well as to the cyclic AMP response element were maintained during cellular aging. While no major differences in the expression of the serum response factor (SRF) that binds the serum response element were seen between early-passage and late-passage cells, hyperphosphorylation of SRF was observed in near-senescent cells. Furthermore, removal of phosphatase inhibitors during the isolation of endogenous nuclear proteins restored the ability of SRF isolated from old cells to bind the SRE. These data, therefore, indicate that hyperphosphorylation of SRF plays a role in altering the ability of this protein to bind to DNA and regulate gene expression in senescent cells.
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PMID:Loss of serum response element-binding activity and hyperphosphorylation of serum response factor during cellular aging. 800 92

Simian virus 40 (SV40) small t antigen (t) can activate transcription from certain RNA polymerase II and III promoters (M. Loeken, I. Bikel, D. M. Livingston, and J. Brady, Cell 55:1171-1177, 1988). Here we report a new function of t, its ability to repress human c-fos promoter and AP-1 transcriptional activity in CV-1P cells. This function is the product of a discrete N-terminal domain of t, because the large T antigen (T)/t-common polypeptide, which contains only the first 82 amino acids common to both T and t of SV40, was, like the intact protein, an active repressor. The data further suggest that the t- and T/t-common-mediated repression of c-fos expression was most likely manifest at the level of transcription. In keeping with the possibility that t affects the expression of the genomic c-fos promoter, it also led to repression of AP-1 formation. Thus, SV40 is both an activator and a repressor of transcription. Its ability to inhibit c-fos expression should be considered in light of the natural history of SV40 in its natural host.
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PMID:Transrepression of RNA polymerase II promoters by the simian virus 40 small t antigen. 808 58

DNA-protein interactions around the regulatory region of the pS2 gene were studied to gain insight into the mechanisms that operate in the estrogen receptor regulated expression of this gene in the MCF-7 human breast cancer cell. Using a revised photocrosslinking technology in combination with gel retardation assays, two distinct multiprotein DNA complexes were shown to assemble in an estrogen receptor-dependent process. Immunological analysis demonstrated the participation of both the estrogen receptor and a c-fos related protein in the formation of these complexes. The results support a model of estrogen receptor function in which the receptor facilitates the formation of multiprotein complexes at DNA sites that can regulate the transcription of a hormone responsive gene by RNA polymerase II and any additional general transcription machinery. These receptor-containing complexes are referred to as "receptorsomes."
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PMID:Estrogen receptor-dependent formation of two distinct multiprotein complexes on the human pS2 gene regulatory segment. Participation of a c-fos related protein. 825 52


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