Identification of an erythroid active element in the transferrin receptor gene.
Hemoglobin synthesis consumes most of the iron that is taken up by cells from plasma transferrin, and this process requires very high expression of transferrin receptors (TfR) at the membranes of erythroid cells. Studies in our and other laboratories indicate that a dramatic increase in TfR levels during erythroid differentiation occurs at the transcriptional level. In this study, we investigated the transcriptional regulation of the TfR in terms of its promoter activity and DNA-protein binding in murine erythroleukemia cells. Reporter gene assays revealed that the TfR promoter activity was stimulated 6-8-fold in murine erythroleukemia cells induced to differentiate into hemoglobin-synthesizing cells by either Me(2)SO or N,N'-hexamethylene-bis-acetamide. A minimal region (-118 to +14) was required for the differentiation-induced promoter activity. Mutation of either an Ets-binding site or an activator protein-1/cyclic AMP-response element-like motif within this region, but not disruption of the adjacent GC-rich/specificity protein-1 sequence, inhibited the inducible promoter activity. Electrophoresis mobility shift assays suggest that the cyclic AMP-response element-binding proteins/activating transcription factor-like factors and Ets-like factors bind constitutively to this bipartite element. Upon induction of differentiation, a shift in the pattern of the cyclic AMP-response element-binding protein/activating transcription factor-like binding factors was observed. Our data indicate that the TfR gene promoter contains an erythroid active element that stimulates the receptor gene transcription upon induction of hemoglobin synthesis.
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Lady Davis Institute for Medical Research, Jewish General Hospital, and the Departments of Physiology and Medicine, McGill University, Montreal, Quebec H3T 1E2, Canada.
Ponka
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D051696:Activating Transcription Factors; D001483:Base Sequence; D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology* / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D011960:Receptors, Estrogen / Q000378:metabolism; D011990:Receptors, Transferrin / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D020218:Response Elements; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D051696:Activating Transcription Factors; D001798:Blood Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D011960:Receptors, Estrogen; D011990:Receptors, Transferrin; D014157:Transcription Factors; D000242:Cyclic AMP