A (G+C)-rich motif in the aldolase C promoter functions as a constitutive transcriptional enhancer element.
The enzyme fructose-1,6-bisphosphate aldolase consists of three isozymes that are expressed in a tissue-specific manner. Using antibodies against aldolase B and C, it is shown that aldolase C is expressed in virtually all neuronal cell lines derived from the central and peripheral nervous system. Recently, experiments with transgenic mice indicated that a (G+C)-rich region of the aldolase C promoter might function as a neuron-specific control element of the rat aldolase C gene [Thomas, M., Makeh, I., Briand, P., Kahn, A. & Skala, H. (1993) Eur. J. Biochem. 218, 143-151). To functionally analyse this element, a plasmid consisting of four copies of this (G+C)-rich sequence, a TATA box, and the rabbit beta-globin gene as reporter was constructed. This plasmid was transfected into neuronal and nonneuronal cell lines and transcription was monitored by RNase protection mapping of the beta-globin mRNA. It is shown that the (G+C)-rich element of the aldolase C promoter directs transcription in neuronal as well as in nonneuronal cells. In contrast, the synapsin I promoter, used as a control for neuron-specific gene expression, directed transcription only in neuronal cells. In gel-retardation assays, two major DNA-protein complexes were detected with the (G+C)-rich element of the aldolase C promoter used as a DNA probe and nuclear extracts from brain and liver as a source for DNA-binding proteins. These DNA-proteins interactions could be impaired by a DNA probe that contained an Sp1-binding site, indicating that Sp1 or an Sp1-related factor binds to the aldolase C promoter (G+C)-rich element. This was confirmed by supershift analysis with antibodies specific for Sp1. The zinc finger transcription factor zif268/egr-1, also known to recognize a (G+C)-rich consensus site, did not, however, bind to the (G+C)-rich motif of the aldolase C promoter, nor could it stimulate transcription in transactivation assays from this control region. From these data, we conclude that the (G+C)-rich element of the aldolase C promoter functions as a constitutive transcriptional response element mediated by Sp1 and Sp1-related transcription factors.
Cibelli
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G
Institute for Genetics, University of Cologne, Germany.
Schoch
S
S
Pajunk
H
H
Brand
I A
IA
Thiel
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G
D000818:Animals; D001483:Base Sequence; D002490:Central Nervous System / Q000201:enzymology; D003596:Cytosine / Q000032:analysis*; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism; D051766:Early Growth Response Protein 1; D004742:Enhancer Elements, Genetic; D005634:Fructose-Bisphosphate Aldolase / Q000235:genetics* / Q000378:metabolism; D006147:Guanine / Q000032:analysis*; D006801:Humans; D017874:Immediate-Early Proteins; D051379:Mice; D008969:Molecular Sequence Data; D017933:Peripheral Nervous System / Q000201:enzymology; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D006147:Guanine; D003596:Cytosine; D004247:DNA; D005634:Fructose-Bisphosphate Aldolase