Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have recently identified an Egr1 motif that overlaps with the Sp1 element in the tyrosine hydroxylase (TH) promoter. Here we examine whether this motif has a functional role in the regulation of TH transcription in PC12 cells. In nuclear extracts from control PC12 cells, an oligonucleotide containing the TH Sp1/Egr1 motif binds Sp1-containing complexes. Treatment of PC12 cells with phorbol ester (2 micrometer 12-O-tetradecanoylphorbol-13-acetate (TPA)) gives rise to a new Egr1-containing complex. TPA treatment reduces the steady-state levels of the Sp1 protein and leads to the appearance of immunoreactive Egr1 protein within 30-60 min. Expression of the Egr1 protein in PC12 cells stimulates the chloramphenicol acetyltransferase reporter gene placed under the control of the first 272 nucleotides of the rat TH promoter. Site-directed mutagenesis of either the Sp1/Egr1 motif or of an upstream AP-1 motif or both abolishes the Egr1-mediated induction of chloramphenicol acetyltransferase activity. An oligonucleotide encompassing the AP-1/E-box sequence of the rat TH promoter competes in electrophoretic mobility shift assays for binding of nuclear extracts from control and TPA-treated cells to an oligonucleotide containing the Sp1/Egr1 element, indicating that these two enhancers may interact. The results show that Egr1 can activate TH transcription and reveals cross-talk between Sp1/Egr1 and AP-1 factors.
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PMID:Ability of Egr1 to activate tyrosine hydroxylase transcription in PC12 cells. Cross-talk with AP-1 factors. 1084 66

The role of c-Fos in neurodegeneration or neuroprotection after cerebral ischemia is controversial. To investigate whether early c-Fos induction after ischemia is associated with neuroprotection, rats were subjected to 10 minutes of transient forebrain ischemia and c-Fos expression was examined. Resistant dentate granule cells and neurons in CA2-4 displayed more robust immunoreactivity than vulnerable neurons in the CA1 region of hippocampus during early hours of reperfusion. By 6 hours after reperfusion, c-Fos immunoreactivity was greatly diminished in all areas of the hippocampus. Administration of N-acetyl-O-methyldopamine (NAMDA), a compound previously shown to protect CA1 neurons against ischemia, increased c-Fos immunoreactivity in the CA1 vulnerable region at 6 hours after ischemia and protected SK-N-BE(2)C neurons from oxygen glucose deprivation. Further in vitro study showed that NAMDA potentiated phorbol-12 myristate-13 acetate (PMA)-induced c-Fos expression, AP1 binding activity, and late gene expression determined by chloramphenicol acetyltransferase (CAT) activity from AP1 containing tyrosine hydroxylase promoter-CAT fusion gene in SK-N-BE(2)C neurons. In vivo and in vitro results showed that a neuroprotectant, NAMDA, in concert with another stimulus (for example, ischemia or PMA) up-regulates c-Fos expression and suggested that the early rise of NAMDA-induced c-Fos expression in vulnerable CA1 neurons may account for neuroprotection by means of up-regulating late gene expression for survival.
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PMID:Early c-Fos induction after cerebral ischemia: a possible neuroprotective role. 1133 65

Tyrosine hydroxylase (TH) is expressed specifically in catecholaminergic cells and is transcriptionally activated via a protein kinase C (PKC)-dependent pathway. To identify regulatory regions of the TH gene, transfected neural crest-derived catecholaminergic cells [human neuroblastoma SH-SY5Y and bovine adrenal medullary (BAM) cells] or glia-derived SF-763 cells were used to analyze expression of a chloramphenicol acetyltransferase (CAT) reporter gene under the control of 5'-flanking sequences of the bovine TH gene. Plasmid pTH(-245/+21)CAT was constructed by fusing the -245 to +21 region of the TH gene to CAT sequences in the promoterless pCAT basic plasmid. Cells transfected with pTH(-245/+21)CAT expressed CAT activity at levels 8- to 100-fold higher than those of cells transfected with pCAT basic. In SH-SY5Y or BAM cells, pTH(-245/+21)CAT supported the expression of CAT at levels similar to or higher than that supported by the tissue nonspecific viral SV40 promoter/enhancer. In glia-like cells, CAT expression from pTH(-245/+2 1)CAT was about 13-fold lower than that under the control of the SV40 promoter. Incubation of neuroblastoma cells with the active phorbol ester, phorbol 12-myristate 13-acetate (PMA), increased expression of CAT from pTH(-245/+2 1)CAT over 6-fold and was accompanied by induction of c-fos and c-jun mRNAs and proteins. The regulation of TH promoter function by c-Fos/c-Jun was corroborated by transactivation of the TH promoter in SH-SY5Y cells engineered to overexpress exogenous c-Fos and c-Jun. TH gene sequences essential for c-Fos/c-Jun transactivation were located in the -245 to -52 region, upstream from a CRE-like element. Gel mobility assays demonstrated binding of c-Fos-antigen(s) to the region of the TH promoter that supports activation by PMA and c-Fos/c-Jun. Temporal patterns of nicotinic agonist-stimulated induction of c-fos and TH mRNA are also consistent with a role for c-Fos in TH gene transcription. Our results demonstrate that the 5'-flanking region of the bovine TH gene operates as an authentic promoter capable (i) of directing cell-specific expression of a bacterial CAT gene and (ii) of conferring responsivity to PKC-stimulation. The results also suggest that the nuclear proteins c-Fos and c-Jun contribute to PKC pathway-mediated activation of the TH gene via direct interaction with the TH gene promoter. The activation of TH gene expression by PKC/c-Fos/c-Jun may serve as an additional or alternative mechanism to activation by the cAMP-CRE pathway.
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PMID:A 5'-flanking region of the bovine tyrosine hydroxylase gene is involved in cell-specific expression, activation of gene transcription by phorbol ester, and transactivation by c-Fos and c-Jun. 1991 82


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