Ability of Egr1 to activate tyrosine hydroxylase transcription in PC12 cells. Cross-talk with AP-1 factors.
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.
Papanikolaou
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NA
Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York 10595, USA.
Sabban
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D000818:Animals; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D051766:Early Growth Response Protein 1; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D017930:Genes, Reporter; D017874:Immediate-Early Proteins; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism; D016716:PC12 Cells; D011485:Protein Binding; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D014446:Tyrosine 3-Monooxygenase; D015500:Chloramphenicol O-Acetyltransferase; D013755:Tetradecanoylphorbol Acetate