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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used monolayers of parental 3T3 fibroblasts and 3T3 cells expressing transfected cell adhesion molecules (CAMs, NCAM, N-cadherin, or L1) as a culture substrate for cerebellar neurons. Previous studies suggest that the transfected CAMs promote neurite outgrowth by activating a second messenger pathway within the responding neuron that involves influx of calcium into neurons as a consequence of activation of an FGF receptor. The same neurite outgrowth response can be induced by FGF or a number of agents that directly activate defined steps in the CAM signaling pathway. In the present study we show that the neurite outgrowth stimulated by the above three CAMs, FGF, arachidonic acid (AA), and K+ depolarization can be abolished by the Ca2+/calmodulin-dependent (CaM) kinase inhibitor, KN-62. We also demonstrate that neurite outgrowth over astrocytes, which represent a more physiologically relevant cellular substrate, can be substantially inhibited by a number of agents that block the CAM signaling pathway, including KN-62. However, neurite outgrowth induced by activation of protein kinase A is unaffected by inhibition of CaM kinase activity as is basal neurite outgrowth over 3T3 monolayers or a polylysine/laminin substrate. These results suggest that CaM kinase activity is specifically required downstream of calcium influx in the CAM and FGF signaling pathway leading to axonal growth.
Mol Cell Neurosci 1995 Feb
PMID:A Ca2+/calmodulin kinase inhibitor, KN-62, inhibits neurite outgrowth stimulated by CAMs and FGF. 759 59

The c-myc oncogene c-Myc is commonly activated in cancer and transactivates gene expression by binding to CACGTG DNA sequences as a heterodimeric complex with Max. The ornithine decarboxylase (ODC), p53, prothymosin alpha and ECA39 promoters are transactivated by c-Myc, and are considered direct targets, as activation is mediated by CACGTG sequences. Interestingly, the c-Myc-responsive CACGTG sequences in the p53, prothymosin alpha, ECA39 and murine ODC genes are all downstream of the RNA CAP site, suggesting that downstream sequences are preferred c-Myc targets. Using a series of heterologous reporter constructs, we have tested the effects of position and orientation of c-Myc-responsive CACGTG sequences on c-Myc's ability to activate transcription. A single binding site conferred c-Myc-responsiveness independent of position and orientation, and over distances of 1.7 kbp. The extent of transactivation was not significantly influenced by position of the responsive elements. By contrast, the extent of transactivation was dependent upon the number of c-Myc binding sites. The results demonstrate that c-Myc activates transcription independent of position and orientation and that considerable flexibility exists in the interaction of c-Myc transactivation domains with the general transcription machinery.
Cell Mol Biol Res 1994
PMID:Position and orientation independent transactivation by c-Myc. 778 88

The NagC repressor binds to two sites in the intergenic nagE-B region overlapping the divergently expressed nagE and nagB promoters. In addition the NagC repressor binds to two sites upstream of the manXYZ operon. Although basically palindromic, there is little sequence consensus between the four operators. To identify the DNA sequence important for NagC recognition, we have taken advantage of the fact that repression of the nagE and nagB genes requires the formation of a loop of DNA between molecules of the repressor bound to the nagE and nagB operators. The nagE operator was systematically mutagenised and the effect of the mutations measured on the level of expression from a nagB-lacZ fusion. These experiments showed that the most important positions for recognition are the two A.T base-pairs at positions-5 and -6 from the centre of symmetry. These are the only absolutely conserved bases in the four operators. Certain changes of residues at position -3 and -4 have fairly strong effects while changes at -7 to -10 have only minor effects. However the presence of a G or C base at positions + 11 or -11 produces a NagC binding site with considerably higher affinity than the wide-type nagE operator both in vitro and in vivo, a "super-operator". The presence of a super-operator considerably increased the stability of the binary looped NagC-DNA complex in vitro. However in the presence of cAMP/CAP, NagC showed the same apparent binding affinity to wild-type and super-operators indicating that one role of cAMP/CAP in the repression complex is to reduce the need for high affinity sites. These super-operators allow a higher level of repression of the nagE promoter compared to the nagB, presumably due to the existence of linear complexes of NagC bound to BoxE.
J Mol Biol 1995 Jun 23
PMID:Nag repressor-operator interactions: protein-DNA contacts cover more than two turns of the DNA helix. 779 Dec 15

The res sites, the loci for site-specific recombination by resolvase, contain three binding sites for the protein; the cross-over site, I, and accessory sites II and III. The role of DNA bending by resolvase was examined by replacing either II or III in the res site from Tn21 with the recognition sequence for a heterologous DNA-bending protein, CAP (the catabolite-gene activator protein from Escherichia coli). The CAP sequence was placed at either the same position as the target sequence for Tn21 resolvase or a different position along the DNA. The activity of Tn21 resolvase for recombination between each hybrid and a wild-type res site was measured in the presence of CAP and cyclic AMP. When III was substituted, CAP inhibited Tn21 recombination, except when the CAP sequence was placed sufficiently far away from site II to allow resolvase to bind non-specifically to the DNA between II and the CAP site. With the substitutions at II, the extent of Tn21 recombination in the presence of CAP varied with the position of the CAP sequence: more recombination was observed when it superimposed the target sequence for resolvase than when it was displaced by five base-pairs. Efficient recombination by Tn21 resolvase thus seems to demand the cognate protein at site III in res, presumably for protein-protein interactions in the synaptic complex, while the function of resolvase at site II can be fulfilled, at least in part, by a heterologous DNA bend.
J Mol Biol 1995 Jan 20
PMID:Site-specific recombination at res sites containing DNA-binding sequences for both Tn21 resolvase and CAP. 784 14

This article describes the use of three reporter enzymes used to study promoter activity in transgenic animals. Chloramphenicol acetyl transferase may be assayed by a nonchromatographic method that is rapid and sensitive. beta-Galactosidase is measured by a photometric assay and luciferase is assayed by measuring the emission of light using a luminometer. The relative merits of each enzyme is discussed. The use of reporter enzymes provides a rapid and sensitive method for analysis of transgene expression.
Mol Biotechnol 1994 Aug
PMID:Reporter enzymes for the study of promoter activity. 786 66

Hepatocyte growth factor (HGF), a cytokine with multiple functions, exhibits cell-type-specific as well as cytokine- and steroid hormone-regulated expression. The HGF gene is known to be expressed predominately in mesenchymal but not in epithelial cells. In this study, we report the identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse HGF gene, which is evidently responsible for the suppression of HGF expression in epithelial cells. Gel mobility shift assays and DNase I footprinting studies revealed that a 27-bp element (-16 to +11) around the transcription initiation site is responsible for the binding of a nuclear protein which is present in epithelial but not in mesenchymally derived cells. Further analysis of the binding activity of the DNA region with nuclear protein revealed that an approximately 19-bp sequence containing a unique palindromic structure (5'-AACCGACCGGTT-3') overlapped by a CAP box is essential for binding. Substitution of a single base (the contact site) within this region by site-directed mutagenesis resulted in total abrogation of the binding of the nuclear protein and a concomitant increase in the transcriptional activity of various lengths of HGF-chloramphenicol acetyltransferase fused genes when transfected into the epithelial cell line RL95-2 but not the mesenchymal cell line NIH 3T3. Southwestern (DNA-protein) analyses revealed that the nuclear protein which binds to this repressor element is a single polypeptide of approximately 70 kDa. Analysis of the nuclear extract prepared from regenerating mouse liver at various times after two-thirds partial hepatectomy by gel mobility shift assay revealed a substantial reduction (more than 75% within 3 h) in the binding of the repressor to its cognate binding site. Our results suggest that a cis-acting transcriptional repressor in the promoter region of the mouse HGF gene is involved in cell-type-specific regulation through binding to its cognate trans-acting protein which exists in epithelial cells but is absent in fibroblast cells.
Mol Cell Biol 1994 Nov
PMID:Identification of a cell-type-specific transcriptional repressor in the promoter region of the mouse hepatocyte growth factor gene. 793 20

CAP-dependent promoters can be divided into classes based on the position of the DNA site for CAP. In class I CAP-dependent promoters, the DNA site for CAP is located upstream of the DNA site for polymerase; the DNA site for CAP can be located at various distances from the transcription start point, provided that the DNS site for CAP and the DNA site for RNA polymerase are on the same face of the DNA helix. In class II CAP-dependent promoters, the DNA site for CAP overlaps the DNA site for RNA polymerase, replacing the -35 determinants for binding of RNA polymerase. In previous work, we have shown that a surface loop consisting of amino acid residues 152 to 166 of CAP is essential for transcription activation at the best-characterized class I CAP-dependent promoter, the lac promoter, and we proposed that this surface loop makes direct protein-protein contact with RNA polymerase in the ternary complex of lac promoter, CAP, and RNA polymerase. Here, we show that the surface loop consisting of amino acid residues 152 to 166 is essential for transcription activation at other class I CAP-dependent promoters and at a class II CAP-dependent promoter. We show further that the effects of alanine substitutions of residues 152 to 166 are qualitatively identical at the lac promoter and other class I CAP-dependent promoters, but are different at a class II CAP-dependent promoter. We propose that the surface loop consisting of residues 152 to 166 makes identical molecular interactions in transcription activation at all class I CAP-dependent promoters, irrespective of distance between the DNA site for CAP and the transcription start point, but makes a different set of molecular interactions in transcription activation at class II CAP-dependent promoters.
J Mol Biol 1994 Nov 04
PMID:Characterization of the activating region of Escherichia coli catabolite gene activator protein (CAP). II. Role at Class I and class II CAP-dependent promoters. 796 85

Androgen and androgen receptor (AR) play an important role in sexual differentiation and prostate proliferation. To investigate AR gene transcriptional regulation, a 2.3-kilobase AR gene promoter region was isolated, sequenced, and characterized. Chloramphenicol acetyltransferase (CAT) assay and sequence homology search of AR gene promoter among human, rat, and mouse revealed some potential cis-acting elements, including a GC box, a suppressor region, and a purine-rich element. Deletion analysis and gel retardation assay using a 50-base pair (bp) double-strand purine-rich element showed that this purine-rich element can bind to specific proteins in nuclear extract of LNCaP and HeLa cells and may be essential for AR gene transcription. Furthermore, to investigate the effect of cAMP on AR gene transcription, we treated LNCaP and HeLa cells with 10 mM (Bu)2cAMP after transfection with CAT gene reporter plasmids linked to the AR gene promoter. This treatment induced several folds of CAT activity in LNCaP cells only, and the induction was further confirmed at AR mRNA level by Northern blot analysis and reverse transcription-polymerase chain reaction assay. Deletion analysis of the AR gene promoter showed that a region between 530 bp and 380 bp upstream of AR gene transcription initiation site, which includes one potential cAMP response element (CRE), is responsible for cAMP induction. Gel retardation analysis using this CRE (AR/CRE1) showed that AR/CRE1 can bind to specific proteins in nuclear extract of LNCaP cells, which appears to form a different binding complex compared to somatostatin/CRE.
Mol Endocrinol 1994 Jan
PMID:Identification of 3',5'-cyclic adenosine monophosphate response element and other cis-acting elements in the human androgen receptor gene promoter. 815 32

The cyanobacterium Synechocystis PCC6803 was chosen as a target organism for construction of a suitable photosynthetic host to enable selection of variant plant-like ribulose bisphosphate carboxylase/oxygenase (Rubisco) enzymes. The DNA region containing the operon encoding Rubisco (rbc) was cloned, sequenced and used for the construction of a transformation vector bearing flanking sequences to the rbc genes. This vector was utilized for the construction of a cyanobacterial rbc null mutant in which the entire sequence comprising both rbc genes, was replaced by the Rhodospirillum rubrum rbcL gene linked to a chloramphenicol resistance gene. Chloramphenicol-resistant colonies, Syn6803 delta rbc, were detected within 8 days when grown under 5% CO2 in air. These transformants were unable to grow in air (0.03% CO2). Analysis of their genome and Rubisco protein confirmed the site of the mutation at the rbc locus, and indicated that the mutation had segregated throughout all of the chromosome copies, consequently producing only the bacterial type of the enzyme. In addition, no carboxysome structures could be detected in the new mutant. Successful restoration of the wild-type rbc locus, using vectors bearing the rbc operon flanked by additional sequences at both termini, could only be achieved upon incubating the transformed cells under 5% CO2 in air prior to their transferring to air. The yield of restored transformants was proportionally related to the length of those sequences flanking the rbc operon which participate in the homologous recombination. The Syn6803 delta rbc mutant is amenable for the introduction of in vitro mutagenized rbc genes into the rbc locus, aiming at the genetic modification of the hexadecameric type Rubisco.
Plant Mol Biol 1993 Nov
PMID:Construction of a Synechocystis PCC6803 mutant suitable for the study of variant hexadecameric ribulose bisphosphate carboxylase/oxygenase enzymes. 821 82

Buffalo rat liver cells were stably transfected with an expression vector containing rat GH (rGH) receptor cDNA. Transfected cells expressed rGH receptor mRNA and specifically bound GH with high affinity. When transfected cells were stimulated with GH, levels of lipoprotein lipase (LPL) mRNA were increased in a time- and dose-dependent fashion, while glyceraldehyde-3-phosphate-dehydrogenase mRNA levels were unaffected. No GH binding or LPL mRNA could be detected in untransfected cells. Treatment of transfected cells with actinomycin D inhibited the GH-stimulated increase in LPL mRNA, indicating that GH acts at a transcriptional level. When protein synthesis was inhibited using cycloheximide, basal levels of LPL mRNA were increased, and there was no GH stimulation. This suggests that LPL gene expression is constantly repressed by a labile protein. Chloramphenicol acetyltransferase constructs containing the human LPL promoter could be regulated by GH. In conclusion, stimulation of the rGH receptor in stably transfected Buffalo rat liver cells results in specific induction of LPL gene expression. This provides a novel model to study the mechanism of GH action, particularly in relation to gene regulation.
Mol Endocrinol 1993 Aug
PMID:A novel in vitro model for studying signal transduction and gene regulation via the growth hormone receptor. 823 17


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