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Activation of the HIV-1 enhancer by the LEF-1 HMG protein on nucleosome-assembled DNA in vitro.
Sheridan, P. L.; Sheline, C. T.; Cannon, K. et al.
1995In Genes and Development, 9 (17), p. 2090-104
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Keywords :
Animals; Base Sequence; Binding Sites; Cloning, Molecular; DNA, Viral/metabolism; DNA-Binding Proteins/metabolism; Drosophila; HIV Enhancer/genetics; HIV-1/genetics; Hela Cells; Humans; Lymphoid Enhancer-Binding Factor 1; Molecular Sequence Data; Nucleosomes/metabolism; Proto-Oncogene Protein c-ets-1; Proto-Oncogene Proteins/metabolism; Proto-Oncogene Proteins c-ets; Recombinant Proteins/metabolism; Sp1 Transcription Factor/metabolism; T-Lymphocytes/metabolism; Transcription Factors/metabolism; Transcriptional Activation; Tumor Cells, Cultured
Abstract :
[en] Lymphoid enhancer-binding factor 1 (LEF-1) is a regulatory high mobility group (HMG) protein that activates the T cell receptor alpha (TCR alpha) enhancer in a context-restricted manner in T cells. In this paper we demonstrate that the distal region of the human immunodeficiency virus-1 (HIV-1) enhancer, which contains DNA-binding sites for LEF-1 and Ets-1, also provides a functional context for activation by LEF-1. First, we show that mutations in the LEF-1-binding site inhibit the activity of multimerized copies of the HIV-1 enhancer in Jurkat T cells, and that LEF-1/GAL4 can activate a GAL4-substituted HIV-1 enhancer 80- to 100-fold in vivo. Second, recombinant LEF-1 is shown to activate HIV-1 transcription on chromatin-assembled DNA in vitro. By using a nucleosome-assembly system derived from Drosophila embryos, we find that the packaging of DNA into chromatin in vitro strongly represses HIV-1 transcription and that repression can be counteracted efficiently by preincubation of the DNA with LEF-1 (or LEF-1 and Ets-1) supplemented with fractions containing the promoter-binding protein, Sp1. Addition of TFE-3, which binds to an E-box motif upstream of the LEF-1 and Ets-1 sites, further augments transcription in this system. Individually or collectively, none of the three enhancer-binding proteins (LEF-1, Ets-1, and TFE-3) could activate transcription in the absence of Sp1. A truncation mutant of LEF-1 (HMG-88), which contains the HMG box but lacks the trans-activation domain, did not activate transcription from nucleosomal DNA, indicating that bending of DNA by the HMG domain is not sufficient to activate transcription in vitro. We conclude that transcription activation by LEF-1 in vitro is a chromatin-dependent process that requires a functional trans-activation domain in addition to the HMG domain.
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Sheridan, P. L.
Sheline, C. T.
Cannon, K.
Voz, Marianne  ;  Université de Liège - ULiège > Département des sciences de la vie > GIGA-R : Biologie et génétique moléculaire
Pazin, M. J.
Kadonaga, J. T.
Jones, K. A.
Language :
English
Title :
Activation of the HIV-1 enhancer by the LEF-1 HMG protein on nucleosome-assembled DNA in vitro.
Publication date :
1995
Journal title :
Genes and Development
ISSN :
0890-9369
eISSN :
1549-5477
Publisher :
Cold Spring Harbor Laboratory Press, Cold Spring Harbor, United States - New York
Volume :
9
Issue :
17
Pages :
2090-104
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 28 November 2012

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