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

In an attempt to study potential feedback regulation of the neu oncogene, we have found that the neu oncogene product specifically represses its own promoter activity. Deletion analysis indicated a 140-bp region (nucleotides -312 to -173 relative to the ATG initiation codon) in the rat neu promoter responsible for neu autorepression. Gel shift assays and methylation interference analysis further demonstrated that a GGTGGGGGGG sequence (nucleotides -243 to -234 relative to the ATG initiation codon) in this 140-bp region interacts with specific protein complexes. The GGTGGGGGGG sequence (GTG element), which functions as an enhancer, is sufficient to cause neu-mediated repression in a heterologous promoter. Furthermore, it produces different gel shift patterns with nuclear extracts from neu-transformed cell lines and their parental lines, suggesting that a transcriptional factor(s) interacting with this enhancer element has been perturbed by the introduction of neu. Taken together, the data presented in this report show that (i) the neu oncogene product autorepresses its own promoter, (ii) the neu promoter contains a novel enhancer, and (iii) neu autorepression is mediated through this enhancer, likely by inhibition of the enhancer activity.
Mol Cell Biol 1992 Jun
PMID:Negative autoregulation of the neu gene is mediated by a novel enhancer. 135 Mar 24

The amount of agonist activity displayed by the antiglucocorticoid dexamethasone mesylate (Dex-Mes) for the induction of tyrosine aminotransferase (TAT) in rat hepatoma cells is greater than for glutamine synthetase and varies over a period of weeks. This variation, which has been reproduced over a period of 40 h by changing the density of the cells, suggests the involvement of a trans-acting factor. The target of this proposed trans-acting factor has now been localized to the region between -3.9 to -2.9 of the rat TAT gene from experiments with cells that were stably transfected with hybrid TAT/CAT constructs. Deletion experiments with transiently transfected TAT/tk promoter/CAT constructs revealed that this entire activity could be conveyed by a 21 bp sequence of the TAT gene. Gel shift experiments support the binding of a factor(s) to this 21 bp sequence. Thus the activity of the antagonist Dex-Mes is relatively independent of steroid structure and is largely determined by the further interactions of a trans-acting factor with the cis-acting sequence. We call this novel sequence a glucocorticoid modulatory element. A model is advanced which accounts for almost all of the results concerning TAT induction by glucocorticoids. This same model may also be useful in explaining why the amount of agonist activity of most antisteroids varies, even for different genes within the same cell.
J Steroid Biochem Mol Biol 1992 Sep
PMID:Modulation of the agonist activity of antisteroids by a novel cis-acting element. 135 17

The alpha-amylase gene is known to be regulated by the plant hormone gibberellin (GA) in cereal aleurone cells. The accumulation of the mRNA corresponding to a rice high pI alpha-amylase gene, OSamy-c, was stimulated 20-fold by exogenous GA3 in half-seeds lacking embryos. Regulatory regions in the promoter of this high pI sub-family were analyzed. The OSamy-c 5' flanking sequence, spanning positions -231 to +29, was fused upstream of the beta-glucuronidase (GUS) gene coding region. The delivery of this plasmid into rice aleurone cells by the biolistic method resulted in a GA-stimulated synthesis of GUS. Gel retardation assays were performed to study protein-DNA interactions between putative regulatory sequences of OSamy-c and partially purified rice seed extracts. We identified multiple seed-specific protein factors that bind to proximal regions of the OSamy-c promoter between positions -231 and -162. Five different proteins were distinguished based on competitive binding studies. Three protein binding regions were located by footprinting analyses, one of which is located in the conserved sequence also found upstream of other GA-inducible genes. Two protein factors in rice aleurone cells that interact with the putative regulatory sequence do not require GA induction.
Mol Gen Genet 1992 Apr
PMID:Regulation and interaction of multiple protein factors with the proximal promoter regions of a rice high pI alpha-amylase gene. 137 14

It is well established that the gene encoding the hormone secretin is expressed in a specific enteroendocrine cell, the S cell. We now show that the secretin gene is transiently expressed in insulin-producing B cells of the developing pancreatic islets in addition to the intestine. Furthermore, secretin is produced by most established islet cell lines. In order to identify and characterize the regulatory elements within the secretin gene that control tissue-specific expression, we have introduced secretin reporter gene constructions into the secretin-producing HIT and STC-1 cell lines as well as the nonexpressing INR1-G9 glucagonoma line. Analysis of deletion mutants revealed that sequences between 174 and 53 bp upstream from the transcriptional start site are required for maximal expression in secretin-producing cells. This positive element functioned independently of position and orientation. Further deletions into the enhancer resulted in a stepwise loss of transcriptional activity, suggesting the presence of several discrete control elements. The sequence CAGCTG within the secretin enhancer closely resembles that of the core of the B-cell-specific enhancer in the insulin gene. Point mutations introduced into this putative element led to greater than 85% reduction in transcriptional activity. Gel mobility shift assays suggested that a factor in B cells closely related or identical to proteins that bind to the insulin enhancer interacts with the CAGCTG motif in the secretin gene.
Mol Cell Biol 1992 Aug
PMID:Identification of a transcriptional enhancer important for enteroendocrine and pancreatic islet cell-specific expression of the secretin gene. 137 28

Erwinia chrysanthemi secretes five major isoenzymes of pectate lyases encoded by the pelABCDE genes. The nucleotide sequence of the region surrounding the pelB gene of E. chrysanthemi 3937 was determined, including the regulatory regions involved in pelB and pelC expression. Analysis of the transcripts showed that transcription of pelB or pelC gave, in both cases, only one transcript. The transcription initiation sites of both pelB and pelC were precisely determined as well as the position of the transcription termination of pelB. The pelB and pelC promoters are very similar, showing a good homology with the -35 consensus region but low homology with the -10 consensus. In both cases a KdgR-box overlaps the -35 region. The pelC gene may have two KdgR operators. Moreover, the pelB and pelC genes are preceded by other sequences presenting the typical symmetry of operator sites that could be involved in more specific regulations. Comparison of E. chyrsanthemi pel regulatory regions revealed three classes of homology: pelA, pelB-pelC and pelD-pelE. The sole regulatory sequence conserved among the three classes corresponds to the KdgR-binding site. Moreover, all the pel regulatory regions are AT-rich in contrast to the coding regions which are GC-rich. Gel retardation experiments with fragments overlapping the pelB or pelC regulatory regions demonstrated that the KdgR protein specifically binds to these regions. Other proteins probably also interact with these DNA fragments. Transcription of pelB terminates in a region corresponding to a GC-rich inverted repeat followed by a run of T residues, typical of rho-independent transcription termination sites. Moreover, preliminary results imply that a region adjacent to pelC provoke, directly or indirectly, the repression of pelB and pelC expression.
Mol Microbiol 1992 Aug
PMID:Analysis of the regulation of the pelBC genes in Erwinia chrysanthemi 3937. 140 75

IrgA is an iron-regulated virulence factor for infection in an animal model with classical Vibrio cholerae strain 0395. We detected gene sequences hybridizing to irgA at high stringency in clinical isolates in addition to 0395, including another classical strain of V. cholerae, three V. cholerae strains of the El Tor biotype, three non-O1 isolates of V. cholerae, and individual isolates of Vibrio parahaemolyticus, Vibrio fluvialis, and Vibrio alginolyticus. No hybridization to irgA was seen with chromosomal DNA from Vibrio vulnificus or Aeromonas hydrophila. To verify that irgA is the structural gene for the major iron-regulated outer membrane protein of V. cholerae, we determined the amino-terminal sequence of this protein recovered after gel electrophoresis and demonstrated that it corresponds to the amino acid sequence of IrgA deduced from the nucleotide sequence. Gel electrophoresis showed that two El Tor strains of V. cholerae had a major iron-regulated outer membrane protein identical in size and appearance to IrgA in strain 0395, consistent with the findings of DNA hybridization. We have previously suggested that IrgA might be the outer membrane receptor for the V. cholerae siderophore, vibriobactin. Biological data presented here, however, show that a mutation in irgA had no effect on the transport of vibriobactin and produced no defect in the utilization of iron from ferrichrome, ferric citrate, haemin or haemoglobin. The complete deduced amino acid sequence of IrgA demonstrated homology to the entire class of Escherichia coli TonB-dependent proteins, particularly Cir. Unlike the situation with Cir, however, we were unable to demonstrate a role for IrgA as a receptor for catechol-substituted cephalosporins. The role of IrgA in the pathogenesis of V. cholerae infection, its function as an outer membrane receptor, and its potential interaction with a TonB-like protein in V. cholerae remain to be determined.
Mol Microbiol 1992 Aug
PMID:Characterization of a Vibrio cholerae virulence factor homologous to the family of TonB-dependent proteins. 140 79

beta-cell type-specific expression of the upstream glucokinase promoter was studied by transfection of fusion genes and analysis of DNA-protein interactions. A construct containing 1,000 bp of 5'-flanking DNA was efficiently expressed in HIT M2.2.2 cells, a beta-cell-derived line that makes both insulin and glucokinase, but not in NIH 3T3 cells, a heterologous cell line. In a series of 5' deletion mutations between bases -1000 and -100 (relative to a base previously designated +1), efficient expression in HIT cells was maintained until -280 bp, after which transcription decreased in a stepwise manner. The sequences between -180 and -1 bp contributing to transcriptional activity in HIT cells were identified by studying 28 block transversion mutants that spanned this region in 10-bp steps. Two mutations reduced transcription 10-fold or more, while six reduced transcription between 3- and 10-fold. Three mutationally sensitive regions of this promoter were found to bind to a factor that was expressed preferentially in pancreatic islet beta cells. The binding sites, designated upstream promoter elements (UPEs), shared a consensus sequence of CAT(T/C)A(C/G). Methylation of adenine and guanine residues within this sequence prevented binding of the beta-cell factor, as did mutations at positions 2, 3, and 5. Analysis of nuclear extracts from different cell lines identified UPE-binding activity in HIT M2.2.2 and beta-TC-3 cells but not in AtT-20, NIH 3T3, or HeLa cells; the possibility of a greatly reduced amount in alpha-TC-6 cells could not be excluded. UV laser cross-linking experiments supported the beta-cell type expression of this factor and showed it to be approximately 50 kDa in size. Gel mobility shift competition experiments showed that this beta-cell factor is the same that binds to similar elements, termed CT boxes, in the insulin promoter. Thus, a role for these elements (UPEs or CT boxes), and the beta-cell factor that binds to them, in determining the expression of genes in the beta cells of pancreatic islets is suggested.
Mol Cell Biol 1992 Oct
PMID:Multiple elements in the upstream glucokinase promoter contribute to transcription in insulinoma cells. 140 48

The effects of glucocorticoid hormones on the expression of the growth factor-inducible genes JE, KC, and c-myc were analyzed in parental BALB/3T3 and polyomavirus middle-T antigen-transfected cell lines. Northern (RNA) blot hybridization and run-on transcription analysis showed that (i) glucocorticoid hormones selectively inhibit JE and KC expression at the transcriptional level and (ii) the downregulatory effect of glucocorticoids on JE and KC expression is partial for serum-stimulated and middle T antigen-transformed cells and total for quiescent and exponentially growing cells. Gel mobility assays using AP-1 oligonucleotides showed a positive correlation between glucocorticoid downregulating effect and presence of the AP-1 complex. JE and KC downregulation by means of the AP-1 complex may play a role in the actions of glucocorticoids as anti-inflammatory and antitumor agents. The ability of glucocorticoids to downregulate JE and KC was used to investigate the relevance of these genes to the mitogenic response to serum growth factors. Hydrocortisone did not alter the basal DNA synthesis level displayed by quiescent 3T3 cells, but it potentiated both the mitogenic effect of platelet-derived growth factor and c-myc induction by serum growth factors. Upon serum restimulation, untreated and dexamethasone-treated quiescent 3T3 cultures entered the S phase after an identical time lag (G1). These results suggest that (i) JE and KC are not necessary for the G0----G1----S transition and (ii) c-myc overexpression is likely to be the basis for the potentiating effect of glucocorticoids on serum growth factors.
Mol Cell Biol 1992 Oct
PMID:Downregulation of JE and KC genes by glucocorticoids does not prevent the G0----G1 transition in BALB/3T3 cells. 140 51

The common ice plant, Mesembryanthemum crystallinum, shifts from C3 to crassulacean acid metabolism (CAM) photosynthesis in response to osmotic stress. The expression of a number of genes encoding enzymes involved in the CAM pathway increases as a result of increased transcription rates. To begin to investigate the mechanisms responsible for the transcriptional activation, we have characterized the 5' control region of a specific isoform of phosphoenolpyruvate carboxylase gene (Ppc1) that plays a key role in CAM. We have determined the nucleotide sequence of the 5' flanking region of this gene. Ppc1 contains a long 5'-leader sequence with the transcriptional start site located 332/333 nucleotides 5' of the translational initiation codon. Multiple DNA interactions with nuclear factors are detectable within the 5'-flanking region of Ppc1. We have used copper orthophenanthroline footprinting to demonstrate that one particularly abundant factor (designated PCAT-1) binds the Ppc1 promoter at two distinct A/T-rich sites located -128 to -158 and -187 to -205 bp upstream of the transcriptional start site. These binding sites share a loose consensus motif having the sequence AARTAAC(T/A)A(G/T)TTTY. Gel retardation competition experiments with oligonucleotides containing these A/T-rich binding sites suggest that both sites bind the same factor, but with different affinities. Fractionation of crude nuclear extracts by heparin-agarose chromatography indicates that PCAT-1 is more prevalent in extracts prepared from salt-stressed leaf tissue. Additional binding activities that interact with the PCAT-1 binding sites have been detected that either increase or decrease in abundance or binding affinity in response to salt stress.
Plant Mol Biol 1992 Nov
PMID:Salt stress alters A/T-rich DNA-binding factor interactions within the phosphoenolpyruvate carboxylase promoter from Mesembryanthemum crystallinum. 142 Nov 45

We purified a large amount of dynamin with high enzymatical activity from rat brain tissue by a new procedure. Dynamin 0.48 mg was obtained from 20 g of rat brain. The purity of dynamin was almost 98%. Dynamin plays a role of GTPase rather than ATPase. In the absence of microtubules, Michaelis constant (Km) and maximum velocity (Vmax) for dynamin GTPase were 370 microM and 0.25 min-1, respectively, and in their presence, both were significantly accelerated up to 25 microM and 5.5 min-1. On the other hand, the ATPase activity was very low in the absence of microtubules, and even in their presence, Km and Vmax for dynamin ATPase were 0.2 mM and 0.91 min-1. Despite slow GTPase turnover rate in the absence of microtubules, binding of GTP and its nonhydrolizing analogues was very fast, indicating that GTP binding step is not rate limiting. Dynamin did not cause a one-directional consistent microtubule sliding movement just like kinesin or dynein in the presence of 2 mM ATP or 2 mM GTP. We observed the molecular structure of dynamin with low-angle rotary shadowing technique and revealed that the dynamin molecule is globular in shape. Gel filtration assay revealed that these globules were the oligomers of 100-kDa dynamin polypeptide. Dynamin bound to microtubules with a 1:1 approximately 1.2 molar ratio in the absence of GTP. Quick-freeze deep-etch electron microscopy of the dynamin-microtubule complex showed that dynamin decorates the surface of microtubules helically, like a screw bolt, very orderly and tightly with 11.4 +/- 0.9 (SD)nm period. Contrary to the previous report, microtubules make bundles by the attachment of the dynamin helixes around each adjacent microtubule, and no cross-bridge formation was observed.
Mol Biol Cell 1992 Oct
PMID:Interaction of dynamin with microtubules: its structure and GTPase activity investigated by using highly purified dynamin. 142 74


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