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Showing papers on "Transcription (biology) published in 1994"


Journal ArticleDOI
TL;DR: The inhibition of NF-kappa B activation by antioxidants and specific protease inhibitors may provide a pharmacological basis for interfering with these acute processes in suppressing toxic/septic shock, graft-vs-host reactions, acute inflammatory reactions, severe phase response, and radiation damage.
Abstract: NF-kappa B is a ubiquitous transcription factor. Nevertheless, its properties seem to be most extensively exploited in cells of the immune system. Among these properties are NF-kappa B's rapid posttranslational activation in response to many pathogenic signals, its direct participation in cytoplasmic/nuclear signaling, and its potency to activate transcription of a great variety of genes encoding immunologically relevant proteins. In vertebrates, five distinct DNA binding subunits are currently known which might extensively heterodimerize, thereby forming complexes with distinct transcriptional activity, DNA sequence specificity, and cell type- and cell stage-specific distribution. The activity of DNA binding NF-kappa B dimers is tightly controlled by accessory proteins called I kappa B subunits of which there are also five different species currently known in vertebrates. I kappa B proteins inhibit DNA binding and prevent nuclear uptake of NF-kappa B complexes. An exception is the Bcl-3 protein which in addition can function as a transcription activating subunit in th nucleus. Other I kappa B proteins are rather involved in terminating NF-kappa B's activity in the nucleus. The intracellular events that lead to the inactivation of I kappa B, i.e. the activation of NF-kappa B, are complex. They involve phosphorylation and proteolytic reactions and seem to be controlled by the cells' redox status. Interference with the activation or activity of NF-kappa B may be beneficial in suppressing toxic/septic shock, graft-vs-host reactions, acute inflammatory reactions, acute phase response, and radiation damage. The inhibition of NF-kappa B activation by antioxidants and specific protease inhibitors may provide a pharmacological basis for interfering with these acute processes.

4,708 citations



Journal ArticleDOI
21 Jul 1994-Nature
TL;DR: The results indicate that p53 either represses genes necessary for cell survival or is a component of the enzymatic machinery for apoptotic cleav-age or repair of DNA5.
Abstract: The tumour suppressor p53 is required to induce programmed cell death (apoptosis) by DNA-damaging agents. As p53 is a transcriptional activator that mediates gene induction after DNA damage, it has been proposed to be a genetic switch that activates apoptosis-mediator genes. Here we evaluate the role of p53 in DNA-damage-induced apoptosis by establishing derivatives of GHFT1 cells, that are somatotropic progenitors immortalized by expression of SV40 T-antigen, which express a temperature-sensitive p53 mutant. In these cells induction of apoptosis by DNA damage depends strictly on p53 function. A shift to the permissive temperature triggers apoptosis following DNA damage, but this is independent of new RNA or protein synthesis. The extent of apoptotic DNA cleavage is directly proportional to the period during which p53 is functional. These results do not support the proposal that p53 is an activator of apoptosis-mediator genes but rather indicate that p53 either represses genes necessary for cell survival or is a component of the enzymatic machinery for apoptotic cleavage or repair of DNA.

879 citations


Journal ArticleDOI
11 Mar 1994-Cell
TL;DR: It is reported here that the inactive Stat91 in the cytoplasm of untreated cells is a monomer and that upon IFN-gamma-induced phosphorylation it forms a stable homodimer.

816 citations


Journal ArticleDOI
TL;DR: Histochemical staining experiments and gene fusion experiments indicated that the 5′ region of cor15a between nucleotides −305 and +78 (relative to the start of transcription) contains a cis-acting element(s) that can impart cold-regulated gene expression.
Abstract: Previous nuclear run-on experiments indicated that the cor15a (cold-regulated) gene of Arabidopsis thaliana L. (Heyn) has a cold-inducible promoter (Hajela et al., Plant Physiol 93: 1246-1252, 1990). The data presented here indicate that the 5' region of cor15a between nucleotides -305 and +78 (relative to the start of transcription) contains a cis-acting element(s) that can impart cold-regulated gene expression. Histochemical staining experiments indicated that the cor15a promoter is inactive, or very weakly active, in most of the tissues and organs of plants grown at normal temperature and that it becomes activated throughout most of the plant in response to low temperature. Notable exceptions to this general pattern include constitutive activity of the promoter in anthers of control grown plants and apparent inactivity of the promoter in the roots and ovaries of cold-treated plants. Histochemical staining experiments also indicated that low temperature regulation of cor15a does not involve the synthesis of a regulatory molecule that can spread throughout the plant and induce cor gene expression at normal growth temperature. Finally, gene fusion experiments indicated that the 5' region of cor15a between nucleotides -305 and +78, in addition to imparting cold-regulated gene expression, can impart ABA- and drought-regulated gene expression.

810 citations


Journal ArticleDOI
21 Jul 1994-Nature
TL;DR: It is reported here that micro-injection of an anti-CBP antiserum into fibroblasts can inhibit transcription from a cAMP responsive promoter, and proposed that CBP is recruited to the promoter through interaction with certain phosphorylated factors, and may thus play a critical role in the transmission of inductive signals from cell surface receptor to the transcriptional apparatus.
Abstract: A number of signalling pathways stimulate transcription of target genes through nuclear factors whose activities are primarily regulated by phosphorylation. Cyclic AMP regulates the expression of numerous genes, for example, through the protein kinase-A (PKA)-mediated phosphorylation of transcription factor CREB at Ser 133. Although phosphorylation may stimulate transcriptional activators by modulating their nuclear transport or DNA-binding affinity, CREB belongs to a class of proteins whose phosphorylation appears specifically to enhance their trans-activation potential. Recent work describing a phospho-CREB binding protein (CBP) which interacts specifically with the CREB trans-activation domain prompted us to examine whether CBP is necessary for cAMP regulated transcription. We report here that microinjection of an anti-CBP antiserum into fibroblasts can inhibit transcription from a cAMP responsive promoter. Surprisingly, CBP also cooperates with upstream activators such as c-Jun, which are involved in mitogen responsive transcription. We propose that CBP is recruited to the promoter through interaction with certain phosphorylated factors, and that CBP may thus play a critical role in the transmission of inductive signals from cell surface receptor to the transcriptional apparatus.

746 citations


Journal ArticleDOI
15 Jul 1994-Cell
TL;DR: It is demonstrated that yan can repress transcription and that this repression activity is negatively regulated by the Ras1/MAPK signal, most likely through direct phosphorylation of yan by MAPK.

687 citations


Journal ArticleDOI
11 Feb 1994-Cell
TL;DR: It is shown that P encodes a Myb homolog that recognizes the sequence CCT/AACC, in sharp contrast with the C/TAACGG bound by vertebrate Myb proteins.

629 citations


Journal ArticleDOI
11 Feb 1994-Science
TL;DR: Many transcription factors contain proline- or glutamine-rich activation domains and it is shown that simple homopolymeric stretches of these amino acids can activate transcription when fused to the DNA binding domain of GAL4 factor.
Abstract: Many transcription factors contain proline- or glutamine-rich activation domains. Here it is shown that simple homopolymeric stretches of these amino acids can activate transcription when fused to the DNA binding domain of GAL4 factor. In vitro, activity increased with polymer length, whereas in cell transfection assays maximal activity was achieved by 10 to 30 glutamines or about 10 prolines. Similar results were obtained when glutamine stretches were placed within a [GAL4]-VP16 chimeric protein. Because these stretches are encoded by rapidly evolving triplet repeats (microsatellites), they may be the main cause for modulation of transcription factor activity and thus result in subtle or overt genomic effects.

611 citations


Journal ArticleDOI
TL;DR: It is shown that Mi protein binds DNA as a homo- or heterodimer with TFEB, TFE3, or TFEC, together constituting a new MiT family, suggesting that Mi's critical roles in melanocyte survival and pigmentation are mediated by MiTFamily interactions and transcriptional activities.
Abstract: The microphthalmia (mi) gene appears essential for pigment cell development and/or survival, based on its mutation in mi mice. It has also been linked to the human disorder Waardenburg Syndrome. The mi gene was recently cloned and predicts a basic/helix-loop-helix/leucine zipper (b-HLH-ZIP) factor with tissue-restricted expression. Here, we show that Mi protein binds DNA as a homo- or heterodimer with TFEB, TFE3, or TFEC, together constituting a new MiT family. Mi can also activate transcription through recognition of the M box, a highly conserved pigmentation gene promoter element, and may thereby determine tissue-specific expression of pigmentation enzymes. Six mi mutations shown recently to cluster in the b-HLH-ZIP region produce surprising and instructive effects on DNA recognition and oligomerization. An alternatively spliced exon located outside of the b-HLH-ZIP region is shown to significantly modulate DNA recognition by the basic domain. These findings suggest that Mi's critical roles in melanocyte survival and pigmentation are mediated by MiT family interactions and transcriptional activities.

609 citations


Journal ArticleDOI
09 Jun 1994-Nature
TL;DR: This work purify two proteins encoded by separate genes that represent the pre-existing and cytosolic components of NF-AT, indicating that distinct signalling pathways converge onNF-ATc to regulate its function.
Abstract: THE NF-AT transcription complex1 is required for the expression of a group of proteins that collectively coordinate the immune response2–4 . Here we purify two proteins encoded by separate genes that represent the pre-existing (p) and cytosolic (c) components of NF-AT. Expression of the full-length complementary DNA enco-ding NF-ATc activates the interleukin (IL-2) promoter in non-T lymphocytes, whereas a dominant negative of NF-ATc specifically blocks activation of the IL-2 promoter in T lymphocytes, indicating that NF-ATc is required for IL-2 gene expression. NF-ATc RNA expression is largely restricted to lymphoid tissues and is induced upon T-cell activation. The other protein, NF-ATp, is highly homo-logous to NF-ATc over a limited domain which shows similarity to the Dorsal/Rel family5, but has a wider tissue distribution. Agents that increase intracellular Ca2+ or activate protein kinase C independently modify NF-ATc, indicating that distinct signalling pathways converge on NF-ATc to regulate its function.

Journal Article
TL;DR: Results indicate that hMCP-1 expression is controlled by at least two distinct regulatory elements: a kappa B site and a GC box that seem to be associated with stimulus-specific and tissue-specific regulation, respectively.
Abstract: Expression of the human monocyte chemoattractant protein-1 (hMCP-1) is ubiquitous in various cell types and is increased by a wide variety of stimuli. We initially found that the effects of various stimuli, including IL-1 beta, TNF-alpha, and 2-O-tetradecanoylphorbol 13-acetate, on the expression of hMCP-1 mRNA were quite different among A172 glioblastoma cells, HT1080 fibrosarcoma cells, and SKLMS1 leiomyosarcoma cells. These findings suggested that hMCP-1 expression is regulated both in a stimulus-specific and a tissue-specific manner. To elucidate the mechanism underlying this stimulus-specific and tissue-specific regulation, we isolated a hMCP-1 5'-flanking genomic DNA fragment and sequenced it extensively up to bp 3011 upstream from the transcriptional start site. Among many putative cis-elements, we identified two cis-elements critical for the transcription of the hMCP-1 gene. The first element is a remote kappa B binding site located far upstream between bp -2612 and -2603 that was important for IL-1 beta-, TNF-alpha-, and 2-O-tetradecanoylphorbol 13-acetate-induced enhancer activity. Mutation at the kappa B consensus site resulted in a complete loss of these stimulus-induced enhancer activities. The second element is a GC box located between bp -64 and -59 that was important for the maintenance of basal transcriptional activity. Overexpression of rSp1 resulted in increased hMCP-1 transcriptional activity, possibly suggesting the role of Sp1 in controlling basal hMCP-1 transcription via this GC box. These results together indicate that hMCP-1 expression is controlled by at least two distinct regulatory elements: a kappa B site and a GC box that seem to be associated with stimulus-specific and tissue-specific regulation, respectively.

Journal ArticleDOI
TL;DR: The mapping of a region of Sp1 with alternating glutamine and hydrophobic residues which is required for the interaction with dTAFII110 and is important for mediating transcriptional activation is reported.
Abstract: Activation of transcription by the promoter-specific factor Sp1 requires coactivators that are tightly associated with the TATA-box-binding protein (TBP) in the TFIID complex. Recent work has shown that the two glutamine-rich activation domains of Sp1, A and B, can interact with at least one component of this complex, the TBP-associated factor dTAFII110. Here we report the mapping of a region of Sp1 with alternating glutamine and hydrophobic residues which is required for the interaction with dTAFII110 and is important for mediating transcriptional activation. Substitution of bulky hydrophobic residues within this region decreased both interaction with dTAFII110 and transcriptional activation in Drosophila cells. In contrast, mutation of glutamine residues in this region had no effect. Thus, the strength of the Sp1-TAF interaction correlates with the potency of Sp1 as a transcriptional activator, indicating that this activator-TAF interaction is an important part of the mechanism of transcriptional activation. Sequence comparison of three activation domains shown to bind dTAFII110 suggests that different activators that utilize dTAFII110 as a coactivator may share common sequence features that we have determined to be important for the Sp1-dTAFII110 interaction.

Journal ArticleDOI
TL;DR: Results demonstrate that the amino-terminal domain and the zinc finger region work in concert to confer high affinity and specific DNA- binding properties to the ROR isoforms and suggest a novel strategy to control DNA-binding activity of nuclear receptors.
Abstract: Three isoforms of a novel member of the steroid hormone nuclear receptor superfamily related to the retinoic acid receptors have been identified. The three isoforms, referred to as RORal, R0Ra2, and R0Ra3, share common DNA- and putative ligand-binding domains but are characterized by distinct amino-terminal domains generated by alternative RNA processing. An exon encoding a functionally important subregion of the amino-terminal domain of the RORa2 isoform resides on the opposite strand of a cytochrome c-processed pseudogene. Binding site selection using in vitro-synthesized proteins reveals that the RORal and R0Ra2 isoforms bind DNA as monomers to hormone response elements composed of a 6-bp AT-rich sequence preceding a half-site core motif PuGGTCA (RORE). However, RORal and RORa2 display different binding specificities: RORal binds to and constitutively activates transcription from a large subset of ROREs, whereas R0Ra2 recognizes ROREs with strict specificity and displays weaker transcriptional activity. The differential DNA-binding activity of each isoform maps to their respective amino-terminal domains. Whereas truncation of the amino-terminal domain diminishes the ability of RORal to bind DNA, a similar deletion relaxes RORa2-binding specificity to that displayed by RORal. Remarkably, transfer of the entire amino-terminal region of RORal or amino-terminal deletion of RORa2 confers RORE-binding specificities to het^erologous receptors. These results demonstrate that the amino-terminal domain and the zinc finger region work in concert to confer high affinity and specific DNA-binding properties to the ROR isoforms and suggest a novel strategy to control DNA-binding activity of nuclear receptors.

Journal ArticleDOI
TL;DR: It is demonstrated here that rpoS/sigma S expression is not only transcriptionally controlled, but is also extensively regulated at the levels of translation and protein stability, and sigma S is a highly unstable protein in exponentially growing cells, that is stabilized at the onset of starvation.
Abstract: The second vegetative sigma factor sigma S (encoded by the rpoS gene) is the master regulator in a complex regulatory network that governs the expression of many stationary phase-induced and osmotically regulated genes in Escherichia coli. Using a combination of gene-fusion technology and quantitative immunoblot, pulse-labeling, and immunoprecipitation analyses, we demonstrate here that rpoS/sigma S expression is not only transcriptionally controlled, but is also extensively regulated at the levels of translation and protein stability. rpoS transcription is inversely correlated with growth rate and is negatively controlled by cAMP-CRP. In complex medium rpoS transcription is stimulated during entry into stationary phase, whereas in minimal media, it is not significantly induced. rpoS translation is stimulated during transition into stationary phase as well as by an increase in medium osmolarity. A model involving mRNA secondary structure is suggested for this novel type of post-transcriptional growth phase-dependent and osmotic regulation. Furthermore, sigma S is a highly unstable protein in exponentially growing cells (with a half-life of 1.4 min), that is stabilized at the onset of starvation. When cells are grown in minimal glucose medium, translational induction and sigma S stabilization occur in a temporal order with the former being stimulated already in late exponential phase and the latter taking place at the onset of starvation. Although sigma S does not control its own transcription, it is apparently indirectly involved in a negative feedback control that operates on the post-transcriptional level. Our analysis also indicates that at least five different signals [cAMP, a growth rate-related signal (ppGpp?), a cell density signal, an osmotic signal, and a starvation signal] are involved in the control of all these processes that regulate rpoS/sigma S expression.

Journal ArticleDOI
Kevin J. Leco1, Rama Khokha1, N Pavloff1, S P Hawkes1, Dylan R. Edwards1 
TL;DR: It is proposed that TIMP-3 functions in a tissue-specific fashion as part of an acute response to remodeling stimuli in murine tissue inhibitor of metalloproteinases-3.


Journal ArticleDOI
TL;DR: Sigma E, an RNA polymerase sigma factor of apparent M(r) 28,000, was previously identified by its ability to direct transcription from the P2 promoter of the agarose gene (dagA) of Streptomyces coelicolor as mentioned in this paper.
Abstract: sigma E, an RNA polymerase sigma factor of apparent M(r) 28,000, was previously identified by its ability to direct transcription from the P2 promoter of the agarose gene (dagA) of Streptomyces coelicolor. A degenerate oligonucleotide probe, designed from the N-terminal sequence of purified sigma E, was used to isolate the sigma E gene (sigE). The predicted sequence of sigma E shows greatest similarity to sequences of seven other proteins: Myxococcus xanthus CarQ, Pseudomonas aeruginosa AlgU, Pseudomonas syringae HrpL, Escherichia coli sigma E, Alcaligenes eutrophus CnrH, E. coli FecI, and Bacillus subtilis SigX, a protein of unknown function. These eight proteins define a subfamily of eubacterial RNA polymerase factors sufficiently different from other sigma s that, in many cases, they are not identified by standard similarity searching methods. Available information suggests that all of them regulate extracytoplasmic functions and that they function as effector molecules responding to extracytoplasmic stimuli. A. eutrophus CnrH appears to be a plasmid-encoded factor.

Journal ArticleDOI
TL;DR: iNOS is identified as the first gene that requires IRF-1 for IFN-gamma-dependent transcriptional regulation, and site-specific substitution of two conserved nucleotides withinIRF-E in the context of the full-length iNOS promoter ablatedIFN- gamma's contribution to synergistic enhancement of transcription.
Abstract: Interferon gamma (IFN-gamma) interacts synergistically with bacterial lipopolysaccharide (LPS) to induce transcription of iNOS, the isoform of nitric oxide synthase whose activity is independent of elevated Ca2+ and exogenous calmodulin. To define a cis-acting element mediating IFN-gamma-dependent synergy, we made deletions in iNOS promoter constructs fused to reporter genes, transfected RAW 264.7 macrophages, and treated the cells with IFN-gamma and/or LPS. This analysis implicated the region from positions -951 to -911, a cluster of four enhancer elements known to bind IFN-gamma-responsive transcription factors, including an interferon regulatory factor binding site (IRF-E) at nucleotides -913 to -923. Site-specific substitution of two conserved nucleotides within IRF-E in the context of the full-length iNOS promoter ablated IFN-gamma's contribution to synergistic enhancement of transcription. Electromobility shift assays performed with a probe containing IRF-E revealed the existence of a complex in nuclei of RAW 264.7 macrophages that was present only after treatment with IFN-gamma, which reacted specifically with anti-IRF-1 immunoglobulin G and which included a species migrating at 40-45 kD, consistent with the apparent molecular weight of murine IRF-1. Thus, the synergistic contribution of IFN-gamma to transcription of iNOS in RAW 264.7 macrophages requires that IRF-1 bind to IRF-E in the iNOS promoter. In conjunction with the work of Kamijo et al. (Kamijo, R., H. Harada, T. Matsuyama, M. Bosland, J. Gerecitano, D. Shapiro, J. Le, K. S. Im, T. Kimura, S. Green et al. 1994. Science [Wash. DC]. 263:1612), these findings identify iNOS as the first gene that requires IRF-1 for IFN-gamma-dependent transcriptional regulation.

Journal ArticleDOI
06 Oct 1994-Nature
TL;DR: It is reported that the switching of the RAR from an activator to an inhibitor of retinoid-dependent transcription requires that it be bound to the upstream half-site of DR1 elements and that it allosterically block the binding of ligand to the RXR.
Abstract: Retinoic acid receptors (RARs) and retinoid X receptors (RXRs) regulate transcription by binding to response elements in target genes that generally consist of two direct repeat half-sites of consensus sequence AGGTCA (ref. 1). RAR/RXR heterodimers activate transcription in response to all-trans or 9-cis retinoic acid by binding to direct repeats spaced by five base pairs (DR5 elements), such that RAR occupies the downstream half-site. RXR homodimers activate transcription in response to 9-cis retinoic acid by binding to direct repeats spaced by one base pair (DR1 elements). Although RXR/RAR heterodimers bind to DR1 elements with higher affinity than RXR homodimers, in most contexts they are unable to activate transcription in response to either all-trans or 9-cis retinoic acid. As a result, RARs inhibit RXR-dependent transcription from these sites. We report that the switching of the RAR from an activator to an inhibitor of retinoid-dependent transcription requires that it be bound to the upstream half-site of DR1 elements and that it allosterically block the binding of ligand to the RXR.

Journal ArticleDOI
TL;DR: It has been proposed that the state of the ribosome is the physiological sensor for the induction of cold‐shock proteins and that the Csp proteins, which share sequence similarity with other prokaryotic proteins and with the‘cold‐shock domain’ of eukaryotic Y‐box proteins, may have a function in activating transcription or unwinding or masking RNA molecules.
Abstract: The cold-shock response of Escherichia coli describes a specific pattern of gene expression in response to abrupt shifts to lower temperatures. This pattern includes the induction of cold-shock proteins, synthesis of proteins involved in transcription and translation, and repression of heat-shock proteins. The identified cold-shock proteins are involved in various cellular functions from supercoiling of DNA to initiation of translation. The major cold-shock protein, CspA, has high sequence similarity with three other E. coli proteins--CspB, CspC, and CspD. Using translational lacZ fusions, cspB was found to be cold-shock inducible at the level of transcription like cspA, while cspC and cspD were not. The Csp proteins, which share sequence similarity with other prokaryotic proteins and with the 'cold-shock domain' of eukaryotic Y-box proteins, may have a function in activating transcription or unwinding or masking RNA molecules. Because the cold-shock response can also be induced by the addition of certain inhibitors of translation, it has been proposed that the state of the ribosome is the physiological sensor for the induction. In addition to E. coli, cold-shock proteins have also been found in other prokaryotic and eukaryotic organisms.


Journal ArticleDOI
TL;DR: It is concluded that proper central plus-strand termination, mediated by a novel cis-active termination sequence, is a key step in HIV-1 replication.

Journal ArticleDOI
07 Oct 1994-Cell
TL;DR: The identification of a human TBP-associated factor (TAF), hTAFII30, associated with a subset of TFIID complexes and the existence of functionally distinct TFIIDs populations that share common TAFIIs but differ in specific TAFiIs are demonstrated.

Journal ArticleDOI
07 Oct 1994-Cell
TL;DR: In vitro assembly and transcriptional properties of TBP-TAF complexes reconstituted from the nine recombinant subunits of Drosophila TFIID are reported and it is suggested that TAFs perform multiple functions during activation.

Journal ArticleDOI
TL;DR: Human genomic DNA fragments containing catechol O-methyltransferase (COMT) sequences were isolated and the exon-intron structure analysed by sequencing, PCR and comparing to the human COMT cDNA sequences, indicating tissue-specific regulation of the COMT gene at transcriptional level.
Abstract: Human genomic DNA fragments containing catechol O-methyltransferase (COMT) sequences were isolated and the exon-intron structure analysed by sequencing, PCR and comparing to the human COMT cDNA sequences The gene contains six exons, of which exons 1 and 2 are non-coding MB-ATG and S-ATG codons, responsible for the initiation of translation of the membrane-bound (MB) and soluble (S) forms of the enzyme, are located in exon 3 Two distinct COMT-specific transcripts, 13 kb and 15 kb, were detected in various human tissues and cell lines Different quantities of the shorter COMT-specific mRNA in the tissues studied suggest a tissue-specific regulation of the COMT gene at transcriptional level Mapping of the 5′ ends of the COMT mRNAs showed that transcription initiates at multiple sites in two separate DNA regions, which are preceded by functional promoter sequences The proximal promoter (P1), located between the two translation initiation codons and extending approximately 200 bp upstream of the MB-ATG initiation codon, apparently gives rise to the 13-kb S-COMT mRNA (S-mRNA) The distal promoter (P2) is located in a DNA fragment in front of and partly overlapping the transcription-start region of the 15-kb transcript, suggesting that it controls the expression of this MB-mRNA Similarities between the rat and human COMT gene promoters are analyzed

Journal ArticleDOI
TL;DR: It is shown that NF-kappa B activates p53 and that this activation is inducible by TNF-alpha, which could be a mechanism by which cells can recover from stress.

Journal ArticleDOI
12 Aug 1994-Cell
TL;DR: Results indicate that PC4 is a general coactivator that functions cooperatively with TAFs and mediates functional interactions between upstream activators and the general transcriptional machinery.

Journal ArticleDOI
13 Oct 1994-Nature
TL;DR: The crystal structure at 3.0 Å resolution of a complex between recombinant MS2 cap-sids and the 19-nucleotide RNA fragment is reported, the first example of a structure at this resolution for a sequence-specific protein-RNA complex apart from the transfer RNA synthetase complexes.
Abstract: THE RNA bacteriophage MS2 is a convenient model system for the study of protein–RNA interactions. The MS2 coat protein achieves control of two distinct processes—sequence-specific RNA encapsidation and repression of replicase translation—by binding to an RNA stem–loop structure of 19 nucleotides containing the initiation codon of the replicase gene. The binding of a coat protein dimer to this hairpin shuts off synthesis of the viral replicase1, switching the viral replication cycle to virion assembly rather than continued replication. The operator fragment alone can trigger self-assembly of the phage capsid at low protein concentrations and a complex of about 90 RNA operator fragments per protein capsid has been described2. We report here the crystal structure at 3.0 A resolution of a complex between recombinant MS2 cap-sids and the 19-nucleotide RNA fragment. It is the first example of a structure at this resolution for a sequence-specific protein-RNA complex apart from the transfer RNA synthetase complexes3–5. The structure shows sequence-specific interactions between conserved residues on the protein and RNA bases essential for binding.

Journal ArticleDOI
TL;DR: The data suggest that properties of the chs transgene locus other than the expression level are important for inducing co-suppression, and the possible role of antisense RNA, which was detected in all transformants, ectopic pairing and the structure of the integrated T-DNAs in the mechanism of the selective increase in chs RNA turnover are discussed.
Abstract: Summary Co-suppression of the pigmentation gene chalcone synthase (chs) in Petunia hybrida by chs transgenes leads to white or variegated flowers and is characterized by a reduction in steady-state mRNA levels. To determine the level at which suppression occurs different petunia transformants were analysed containing CaMV-35S RNA promoter-driven hybrid genes consisting of the β-glucuronidase gene (uidA) linked to the full-length chsA cDNA, the 5′ half or to the 3′ half. With these transgenes one out of 12–15 primary transformants showed suppression of the transgenes and of the resident chs genes throughout the flower or in sectors. The reduction in steady-state chs mRNA was not the result of a transcriptional inactivation event. As determined by nuclear run-on experiments, transcription of suppressed chs genes was similar to that of non-suppressed genes. This indicates that co-suppression occurs post-transcriptionally. Among individual transformants the transgenes were transcribed at different levels but neither a high nor a low level correlated with a particular degree or pattern of suppression. Surprisingly, even a promoterless chs transgene construct was found to suppress the endogenous chs genes in three out of 15 transformants. It remains, however, unknown whether or not transcription of the transgene locus is required to induce co-suppression. The data suggest that properties of the chs transgene locus other than the expression level are important for inducing co-suppression. The possible role of antisense RNA, which was detected in all transformants, ectopic pairing and the structure of the integrated T-DNAs in the mechanism of the selective increase in chs RNA turnover are discussed.