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:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chloramphenicol acetyltransferase gene cat-86 is induced through a mechanism that is a variation of classical attenuation. Induction results from the destabilization of an RNA stem-loop that normally sequesters the cat-86 ribosome-binding site. Destabilization of the stem-loop is due to the stalling of a ribosome in the leader region of cat-86 mRNA at a position that places the A site of the stalled ribosome at leader codon 6. Two events can stall ribosomes at the correct location to induce cat-86 translation: addition of chloramphenicol to cells and starvation of cells for the amino acid specified by leader codon 6. Induction by amino acid starvation is an anomaly because translation of the cat-86 coding sequence requires all 20 amino acids. To explain this apparent contradiction we postulated that amino acid starvation triggers intracellular proteolysis, thereby providing levels of the deprived amino acid sufficient for cat-86 translation. Here we show that a mutation in relA, the structural gene for stringent factor, blocks intracellular proteolysis that is normally triggered by amino acid starvation. The relA mutation also blocks induction of cat-86 by amino acid starvation, but the mutation does not interfere with chloramphenicol induction. Induction by amino acid starvation can be demonstrated in relA mutant cells if the depleted amino acid is restored at very low levels (e.g., 2 micrograms/ml). A mutation in relC, which may be the gene for ribosomal protein L11, blocks induction of cat-86 by either chloramphenicol or amino acid starvation. We believe this effect is due to a structural alteration of the ribosome resulting from the relC mutation and not to the relaxed phenotype of the cells.
...
PMID:Induction of cat-86 by chloramphenicol and amino acid starvation in relaxed mutants of Bacillus subtilis. 314 54

Regulation of argininosuccinate synthetase (AS) was studied by using minigenes containing 3 kilobases of DNA upstream from the TATAA box and 9 kilobases downstream (including the first four exons of the AS gene) ligated to either the cDNA for AS or to the chloramphenicol acetyltransferase (CAT) gene. Unlike the endogenous AS gene, expression of the CAT minigene was not elevated in Canr1 cells, which overproduce AS compared with parental RPMI-2650 cells. Expression of the CAT minigene in both stable and transient analyses was four- to five-fold higher in RPMI-2650 cells grown in citrulline medium than in cells grown in arginine medium. Although endogenous AS activity is not subject to metabolite regulation in Canr1 cells and expression of the CAT minigene in Canr1 cells was not increased when cells were grown in citrulline medium, expression of the CAT minigene was 10- to 22-fold greater when intracellular arginine pools were depleted by transient starvation for arginine and citrulline.
...
PMID:Arginine-mediated regulation of an argininosuccinate synthetase minigene in normal and canavanine-resistant human cells. 378 95

A derivative of the R factor NR1 (called R12) has been isolated which undergoes an increased number of rounds of replication each division cycle in Proteus mirabilis, Escherichia coli, and Salmonella typhimurium. The alteration resulting in the increased number of copies (round of replication mutation) is associated with the transfer factor component of the R factor. R12 has the same drug resistance pattern as NR1, is the same size as shown by sedimentation in a sucrose gradient and electron microscopy (63 x 10(6) daltons), and has the same partial denaturation map. The level of the R factor gene product chloramphenicol acetyltransferase has been examined in P. mirabilis and was found to be consistent with gene dosage effects. The plasmid to chromosomal deoxyribonucleic acid ratio of NR1 increases several fold after entry into stationary phase, whereas this ratio for R12 remains approximately constant. Individual copies of R12 are selected at random for replication from a multicopy plasmid pool. A smaller percentage of R12 copies replicate during amino acid starvation than has previously been found for NR1 in similar experiments.
...
PMID:Round of replication mutant of a drug resistance factor. 459 7

The phoB gene, which encodes a positive control factor for a number of phosphate-regulated genes in Escherichia coli, was cloned into multicopy plasmid pBR322. A phoB-cat fusion that expressed chloramphenicol transacetylase from the phoB promoter was constructed. Studies of the expression of the phoB-cat fusion showed that the pattern of regulation of the phoB gene was similar to that of the phoA gene, the structural gene for alkaline phosphatase. The phoB gene was derepressed under conditions of phosphate starvation, was constitutively expressed in a phoR background, and required the phoM gene product for expression in a phoR strain. Finally, a functional phoB product was required for its own synthesis. Our results indicate either that phoA gene expression responds directly to the concentration of the phoB gene product in cells or that the phoA and phoB controlling elements are quite similar.
...
PMID:Analysis of regulation of phoB expression using a phoB-cat fusion. 631 14

The polyhydroxyalkanoic acid (PHA) biosynthetic gene locus was cloned and characterized from an Acinetobacter sp. isolated from activated sludge. Nucleotide sequence analysis identified three clustered genes, phaAAc (encoding a beta-ketothiolase), phaBAc (encoding an acetoacetyl coenzyme A reductase), and phaCAc (encoding a PHA synthase). In addition, an open reading frame (ORF1) with potential to encode a 13-kDa protein was identified within this locus. The sequence of the putative translational product of ORF1 does not show significant similarity to any sequences in the database. A plasmid containing the Acinetobacter pha locus conferred the ability to accumulate poly-beta-hydroxybutyrate on its Escherichia coli host. These genes appear to lie in an operon transcribed by two promoters upstream of phaBAc, an apparent constitutive promoter, and a second promoter induced by phosphate starvation and under pho regulon control. These as well as a number of additional potential transcription start points were identified by a combination of primer extension and promoter-chloramphenicol acetyltransferase gene fusion studies carried out in Acinetobacter or E. coli transformants.
...
PMID:Phosphate concentration regulates transcription of the Acinetobacter polyhydroxyalkanoic acid biosynthetic genes. 763 32

The state of induction of the platelet-derived growth factor (PDGF) A chain markedly differs among drugs and cells. The increase in A chain mRNA by serum was due to activation of transcription. Transcription was also activated by cycloheximide (CHX) even during serum starvation, indicating that the expression of the PDGF-A chain is inhibited by transcription suppressor factor with a short life during serum starvation. On the other hand, post-transcriptional regulation played a very important role in the increase in A chain mRNA by 12-O-tetradecanoylphorbol-13-acetate (TPA) and superinduction by TPA and CHX. We also analyzed the regions of PDGF-A chain gene that respond to serum and TPA by the chloramphenicol acetyltransferase (CAT) assay and the gel retardation assay. The region from TATA to -135 bp has the activity of the basal expression of PDGF-A chain gene and is considered to be involved in down regulation after the treatment with serum and TPA. Elements that respond to serum and increase the expression of PDGF-A chain gene are present in the region from -135 bp to -223 bp. Elements that inhibit the expression of PDGF-A chain gene during serum starvation are present in the region from -223 bp to -416 bp.
...
PMID:Mechanism of regulation of PDGF-A chain gene expression by serum and TPA. 784 Nov 94

Rat pheochromocytoma PC12 cells were permanently transfected with a plasmid vector, containing the tat gene of human immunodeficiency virus type 1 (HIV-1). Various clones were obtained showing the production of different levels of bioactive Tat protein (Tat) after transient cotransfection with an HIV-1 long terminal repeat-chloramphenicol acetyltransferase reporter plasmid. Under conditions of serum starvation, tat-positive PC12 clones expressing high levels of Tat showed a significantly (P < 0.05) higher proliferation rate with respect to both mock-transfected PC12 cells and tat-positive PC12 cells expressing lower levels of Tat. Moreover, all tat-positive PC12 cell clones showed a partial morphological differentiation into sympathetic-like neurons, when seeded in low density (5 x 10(3) cells/cm2) cultures. On the other hand, mock-transfected PC12 cells showed the round shaped morphology typical of untreated PC12 cells and displayed signs of neuronal differentiation only after treatment with 100 ng/ml of nerve growth factor. The addition of 5 micrograms/ml of anti-Tat monoclonal antibody to the culture medium of tat-positive PC12 cell clones almost completely blocked their increased proliferation rate (P < 0.05), but did not affect neuronal differentiation. A significant (P < 0.05) increase in cell proliferation was consistently observed in PC12 cells supplemented with low concentrations of Tat (5 to 25 ng/ml), whereas neuronal differentiation was hardly affected by exogenous Tat. Our data strongly suggest that Tat exerts a complex influence on the proliferation and differentiation of PC12 cells, and this might help in increasing understanding of the pathogenesis of the frequent neurological disorders observed in AIDS patients.
...
PMID:Influence of the human immunodeficiency virus type 1 Tat protein on the proliferation and differentiation of PC12 rat pheochromocytoma cells. 827 65

By making operon fusions with lambda placMu53, we identified, cloned, and analyzed the phoH gene belonging to the phosphate (pho) regulon. We mapped the phoH gene at 23.6 min in the Escherichia coli genomic library (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987). Its nucleotide sequence revealed an open reading frame of 354 amino acids which contains sequences for nucleotide-binding motifs. From comparison of the DNA sequences, phoH was found to be identical to psiH, which had been identified as a phosphate starvation-inducible gene (W.W. Metcalf, P.M. Steed, and B.L. Wanner, J. Bacteriol. 172:3191-3200, 1990). The PhoH protein was overproduced by the T7 promoter system, identified as a protein of about 39 kDa, and purified. The amino-terminal amino acid sequence of the PhoH protein agreed with the one deduced from the DNA sequence. We demonstrated that PhoH has an ATP-binding activity by a photoaffinity labeling experiment. Two transcriptional initiation sites (P1 and P2) were identified by S1 nuclease mapping. The upstream P1 promoter contains a pho box, the conserved sequence shared by the pho regulon genes. The region containing the pho box was bound by PhoB protein, the transcriptional activator of the pho regulon, as revealed by footprinting. Regulation of phoH expression in vivo was studied by constructing plasmids containing transcriptional fusions of the phoH promoters with a promoterless gene for chloramphenicol acetyltransferase. Transcription from the P1 promoter required the phoB function and was induced by phosphate limitation, while transcription from the P2 promoter was independent of phoB and constitutive under tested conditions.
...
PMID:Molecular analysis of the phoH gene, belonging to the phosphate regulon in Escherichia coli. 844 94

Starvation inhibits and refeeding stimulates transcription of the malic enzyme gene in chick liver. DNA between -320 and +72 base pairs (bp) is DNase I-hypersensitive in hepatic nuclei from fed but not starved chicks (Ma, X. J., and Goodridge, A. G. (1992) Nucleic Acids Res. 20, 4997-5002). A polypyrimidine/polypurine (PPY/PPU) tract lies within the DNase I-hypersensitive region. In hepatocytes transiently transfected with plasmids containing triiodothyronine response elements and a minimal promoter from the malic enzyme gene linked to the chloramphenicol acetyltransferase gene, deletion of the PPY/PPU tract inhibited chloramphenicol acetyltransferase activity by about 90% with or without triiodothyronine. Fine mapping of S1 nuclease-sensitive sites suggests that the PPY/PPU tract can assume different isoforms of non-B-DNA, some of which may be triplex structures. The PPY/PPU tract contains specific binding sites for single- and double-stranded DNA binding proteins and, with 8 bp 3' of the tract, can function as a promoter. A (CT)7 repeat binds single-stranded DNA-binding protein and is essential for promoter activity. Two C-rich elements bind single-stranded DNA-binding proteins and may mediate inhibition of promoter function. The single- and double-stranded DNA-binding proteins that interact with the PPY/PPU tract may regulate transcription of the malic enzyme gene.
...
PMID:Characterization of a polypyrimidine/polypurine tract in the promoter of the gene for chicken malic enzyme. 866 63

Transformed A5 mouse lung cells were examined for mechanisms that may explain their loss of glucocorticoid-induced growth inhibition. These cells were compared to nontransformed C10 mouse lung cells, which retain this response. Southern blot analysis revealed no major differences in the amount or pattern of restriction fragments for the glucocorticoid receptor (GR) gene between the responsive and nonresponsive cells. Northern blot analysis demonstrated that both cell lines expressed GR mRNA at similar levels and that these mRNAs had similar relative stabilities. The mRNA from both cell lines was used for reverse transcription-polymerase chain reaction amplification and direct sequencing with primers for different regions of the GR cDNA. A conservative mutation previously shown not to affect receptor function was detected within the DNA-binding domain region of the GR from both cell lines. Because of the ability of the transcription factors for activator protein-1 to antagonize GR function, c-jun and c-fos mRNA levels were examined. A5 cells were found to have higher levels of c-jun mRNA than C10 cells both during active cell growth and after serum starvation. Stable transfection of the nonresponsive A5 cells with a rat GR expression vector (A5GR7) resulted in strong glucocorticoid-induced growth inhibition, demonstrating that these cells retain the ability to be growth inhibited by these steroids. The A5GR7 transfectants also had higher mouse mammary tumor virus (MMTV)-chloramphenicol acetyltransferase (CAT) activity than the parental A5 cells and lower levels of c-jun during active cell growth. Transient transfection of the C10 cells with c-jun expression vector strongly reduced glucocorticoid-inducible MMTV-CAT activity. These results suggest that the transformed A5 cells apparently contain functional GR but that the high level of c-jun mRNA expression (probably resulting from the activated Ki-ras allele in these cells) may antagonize their ability to respond to the growth-inhibitory signaling of glucocorticoids.
...
PMID:Loss of glucocorticoid-dependent growth inhibition in transformed mouse lung cells. 878 64


<< Previous 1 2 3 Next >>

---