title: Induction of basic helix-loop-helix protein-containing complexes during erythroid differentiation.
abstract: The involvement of basic helix-loop-helix (bHLH) transcription factors in erythroid differentiation and development has been established by forced expression of the proteins TAL1 and Id1 in cultured cell lines and by targeted disruption of the mouse TAL1 gene. To better understand the mechanism by which bHLH proteins regulate erythropoiesis, we have investigated HLH protein-DNA interactions in mouse erythroleukemia (MEL) cells before and during chemically induced differentiation. Three bHLH (E-box) binding activities were found to be induced in nuclei from differentiating MEL cells. Using specific antisera, we have demonstrated that these complexes are dimers of TAL1 and ubiquitous E proteins. Similar complexes were detected in nuclear extracts from a human erythroid cell line, K562, and from mouse fetal liver. All three bHLH complexes were disrupted in vitro by Id1, a dominant-negative HLH protein that we and others have previously shown to antagonize MEL cell differentiation. During differentiation of an Id1-overexpressing MEL cell line, induction of a complex containing TAL1 and E2A was not only blocked but reduced below the levels seen in undifferentiating cells. These observations are consistent with the idea that TAL1 and Id1 have opposing effects on erythroid differentiation and that the level of TAL1/E2A heterodimer and/or another E protein-containing complex may influence the decision of a cell to terminally differentiate.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Lister
authors.forename: M H
authors.initials: MH
authors.lastname: Baron
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D019556:COS Cells; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015672:Erythroid Precursor Cells / Q000166:cytology* / Q000378:metabolism*; D004920:Erythropoiesis; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D007106:Immune Sera; D051798:Inhibitor of Differentiation Protein 1; D051379:Mice; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000378:metabolism*; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D007106:Immune Sera; D051798:Inhibitor of Differentiation Protein 1; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D051820:TCF Transcription Factors; D015534:Trans-Activators; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; C497453:ID1 protein, human; C497455:Idb1 protein, mouse; C544894:TCF7L2 protein, human; C489366:Tal1 protein, mouse; C090743:Tcf4 protein, mouse; C544895:Tcf7l2 protein, mouse; C067143:TAL1 protein, human