Stable co-occupancy of transcription factors and histones at the HIV-1 enhancer.
To investigate mechanisms yielding DNase I-hypersensitive sites (DHSs) at gene regulatory regions, we have initiated a biochemical analysis of transcription factor binding and nucleosome remodeling with a region of the human immunodeficiency virus 1 (HIV-1) 5' long terminal repeat (LTR) that harbors constitutive DHSs in vivo. In vitro reconstitution of an HIV-1 5' LTR fragment into nucleosome core particles demonstrates that Sp1, NF-kappaB1, LEF-1, ETS-1 and USF can gain access to their binding sites in HIV-1 nucleosomal DNA. The factor-bound mononucleosomes resist histone displacement from the DNA by the chromatin remodeling activity, SW1-SNF, or the histone chaperone, nucleoplasmin, suggesting that the binding of these factors to nucleosomal HIV-1 sequences forms a stable complex that includes the underlying histones. However, when the HIV-1 5' LTR fragment is incorporated into a nucleosomal array, Sp1 and NF-kappaB1 binding produce regions of enhanced DNase I sensitivity specifically at the HIV-1 nucleosome. These regions resemble the observed in vivo DHSs, yet the HIV-1 nucleosome remains intact even in the presence of nucleoplasmin. Thus, the constitutive DHSs identified at the HIV-1 enhancer in native chromatin may reflect the presence of a ternary complex composed of transcriptional activators, histones and DNA.
Steger
D J
DJ
Department of Biochemistry and Molecular Biology, The Center for Gene Regulation, The Pennsylvania State University, University Park 16802-4500, USA.
Workman
J L
JL
D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D016322:HIV Enhancer; D018257:Helix-Loop-Helix Motifs; D006657:Histones / Q000378:metabolism*; D006801:Humans; D051821:Lymphoid Enhancer-Binding Factor 1; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D056489:Nucleoplasmins; D009707:Nucleosomes / Q000378:metabolism; D010750:Phosphoproteins; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013698:Templates, Genetic; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D051720:Upstream Stimulatory Factors
D002352:Carrier Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C494041:ETS1 protein, human; D006657:Histones; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; D016328:NF-kappa B; D009687:Nuclear Proteins; D056489:Nucleoplasmins; D009707:Nucleosomes; D010750:Phosphoproteins; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D011505:Protein-Tyrosine Kinases; D003850:Deoxyribonuclease I