Transcriptional regulation in megakaryocytes: the thrombopoietin receptor gene as a model.
The MPL gene codes for the thrombopoietin receptor, whose ligand specifically controls megakaryocytic differentiation. In order to understand the molecular basis for the megakaryocyte-specific expression of MPL, we analyzed the regulatory elements of this gene. Two regions are hypersensitive to DNase I in nuclei of cells that express MPL: the promoter and a portion of intron 6. The latter behaves as a chromatin-dependent enhancer. A 200 bp fragment of the promoter is sufficient for high-level specific expression. This fragment can bind several transacting factors in vitro, including GATA-1 and members of the Ets family. GATA-1 binds with low affinity to a unique GATA motif at -70 in the MPL promoter, and destruction of this site yields only a modest decrease in expression level in human erythroleukemia (HEL) cells. Ets proteins also bind with low affinity to two sites. One is located at position -15 and its destruction reduces expression to 50%; the other is located immediately downstream of the GATA motif and plays a crucial role in expression of the promoter in HEL cells, as its inactivation reduces expression to 15%. This study indicates a molecular basis for the coregulation of markers of megakaryocyte differentiation. Finally, we describe other nuclear factor binding sites that may be involved in the cell-type-specific expression of MPL.
Mignotte
V
V
INSERM U. 91, Hôpital Henri Mondor, Créteil, France.
Deveaux
S
S
Filipe
A
A
D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D019169:Jurkat Cells; D020014:K562 Cells; D008533:Megakaryocytes / Q000378:metabolism* / Q000502:physiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D016329:Sp1 Transcription Factor / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D002843:Chromatin; D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D009363:Neoplasm Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; C082218:MPL protein, human; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D003850:Deoxyribonuclease I