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Activation of transcription of the human presenilinâ1 gene by 12âOâtetradecanoylphorbol 13âacetate
- Pastorcic, Martine, Das, Hriday K.
- European journal of biochemistry 2002 v.269 no.23 pp. 5956-5962
- Northern blotting, brain, gene expression, genes, hepatoma, human cell lines, humans, messenger RNA, neurons, point mutation, tissues, transcription factors, transcriptional activation
- We have recently identified an Ets element controlling over 90% of the basal expression of the human presenilinâ1 (PS1) gene. We have also shown that Ets1 and Ets2 act as transactivators of the PS1 gene by cotransfection experiments in SKâNâSH neuronal cells. The PS1 gene is widely but differentially expressed across tissues and the expression in brain appears to be restricted to neurons. To gain further insight into the regulation of the gene we have examined the regulation of PS1 by 12âOâtetradecanoylphorbol 13âacetate (TPA). SKâNâSH neuronal cells were treated with 0.2âÂµm TPA for 30âmin to 24âh and the level of expression of the endogenous PS1 gene was measured by Northern blot analysis. A twoâ to threefold increase in the level of PS1 mRNA appeared 4â8âh after the addition of TPA. A similar increase in transcription activity was observed in nuclear run off experiments, indicating that the increased mRNA level results from an activation in the initiation of transcription of PS1. Consistently, TPA also increased the level of PS1 protein. No activation of the PS1 endogenous gene by TPA was observed in hepatoma HepG2 cells. Next we tested the effect of TPA on the expression of the PS1 promoter by transfecting fusion genes including various fragments of the PS1 promoter linked to a CAT reporter into SKâNâSH cells. TPA also stimulated the expression of the PS1CAT constructs. Generally wild type constructs â687/+178, â118/+178, â22/+178 including the short â35/+6 fragment showed a minor twoâ to threefold activation by TPA. Point mutations eliminating the â10 Ets motif or the â6 CREB/AP1 motif did not decrease the stimulation by TPA. Thus TPA appears to activate the transcription of the PS1 gene by a mechanism which does not require these elements.