An ikaros-containing chromatin-remodeling complex in adult-type erythroid cells.
We have previously described a SWI/SNF-related protein complex (PYR complex) that is restricted to definitive (adult-type) hematopoietic cells and that specifically binds DNA sequences containing long stretches of pyrimidines. Deletion of an intergenic DNA-binding site for this complex from a human beta-globin locus construct results in delayed human gamma- to ... beta-globin switching in transgenic mice, suggesting that the PYR complex acts to facilitate the switch. We now show that PYR complex DNA-binding activity also copurifies with subunits of a second type of chromatin-remodeling complex, nucleosome-remodeling deacetylase (NuRD), that has been shown to have both nucleosome-remodeling and histone deacetylase activities. Gel supershift assays using antibodies to the ATPase-helicase subunit of the NuRD complex, Mi-2 (CHD4), confirm that Mi-2 is a component of the PYR complex. In addition, we show that the hematopoietic cell-restricted zinc finger protein Ikaros copurifies with PYR complex DNA-binding activity and that antibodies to Ikaros also supershift the complex. We also show that NuRD and SWI/SNF components coimmunopurify with each other as well as with Ikaros. Competition gel shift experiments using partially purified PYR complex and recombinant Ikaros protein indicate that Ikaros functions as a DNA-binding subunit of the PYR complex. Our results suggest that Ikaros targets two types of chromatin-remodeling factors-activators (SWI/SNF) and repressors (NuRD)-in a single complex (PYR complex) to the beta-globin locus in adult erythroid cells. At the time of the switch from fetal to adult globin production, the PYR complex is assembled and may function to repress gamma-globin gene expression and facilitate gamma- to beta-globin switching.
Mesh Terms:
Adenosine Triphosphatases, Aging, Animals, Autoantigens, Chromatin, DNA, DNA Helicases, DNA-Binding Proteins, Gene Expression Regulation, Globins, Histone Deacetylases, Histones, Humans, Ikaros Transcription Factor, Leukemia, Erythroblastic, Acute, Macromolecular Substances, Mi-2 Nucleosome Remodeling and Deacetylase Complex, Mice, Mice, Transgenic, Nuclear Proteins, Precipitin Tests, Protein Binding, Sin3 Histone Deacetylase and Corepressor Complex, Substrate Specificity, Transcription Factors, Tumor Cells, Cultured, Zinc Fingers
Adenosine Triphosphatases, Aging, Animals, Autoantigens, Chromatin, DNA, DNA Helicases, DNA-Binding Proteins, Gene Expression Regulation, Globins, Histone Deacetylases, Histones, Humans, Ikaros Transcription Factor, Leukemia, Erythroblastic, Acute, Macromolecular Substances, Mi-2 Nucleosome Remodeling and Deacetylase Complex, Mice, Mice, Transgenic, Nuclear Proteins, Precipitin Tests, Protein Binding, Sin3 Histone Deacetylase and Corepressor Complex, Substrate Specificity, Transcription Factors, Tumor Cells, Cultured, Zinc Fingers
Mol. Cell. Biol.
Date: Oct. 01, 2000
PubMed ID: 11003653
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