Ectopic expression of the cAMP-responsive element binding protein inhibits phorbol ester-mediated induction of tissue-type plasminogen activator gene expression.
The human tissue-type plasminogen activator (t-PA) gene is regulated in a cell-type dependent manner. The t-PA gene is transcriptionally induced by the phorbol ester PMA in HeLa cells, but suppressed by PMA in HT-1080 cells. A cAMP responsive element (tPACRE) and a Sp-1 site located within the proximal t-PA gene promoter are functionally important in both cell systems. HeLa and HT-1080 cells contain a different repertoire of factors that associate with the tPACRE. In HT-1080 cells, CREB and c-Jun are the two major t-PACRE binding proteins identified, while activating transcription factor 2 (ATF-2) is a predominant t-PACRE binding protein in HeLa cells. To determine whether alteration in the distribution of tPACRE binding proteins would influence the differential regulation of the t-PA gene in these cells, the tPACRE binding profiles in these two cell systems were manipulated by over expressing ATF-2 in HT-1080 cells and CREB in HeLa cells. Supershift experiments confirmed that the overexpression of these factors resulted in binding to the tPACRE site. However, the presence of ATF-2 in HT-1080 cells did not affect either constitutive or PMA-mediated suppression of the endogenous t-PA gene. In contrast, enforced tPACRE-binding activity of CREB in HeLa cells significantly reduced the magnitude of PMA-mediated induction of t-PA mRNA in HeLa cells. These results indicate that the introduction of CREB into HeLa cells disrupts the regulation of the t-PA gene.
Costa
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Monash University Department of Medicine, Box Hill Hospital, Box Hill, Victoria, Australia.
Medcalf
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RL
D051698:Activating Transcription Factor 2; D051786:Cyclic AMP Response Element Modulator; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D010703:Phorbol Esters / Q000494:pharmacology*; D012097:Repressor Proteins / Q000378:metabolism; D020218:Response Elements; D010959:Tissue Plasminogen Activator / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D010703:Phorbol Esters; D012097:Repressor Proteins; D014157:Transcription Factors; D051786:Cyclic AMP Response Element Modulator; D010959:Tissue Plasminogen Activator