The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform
Katherine A Jones - One of the best experts on this subject based on the ideXlab platform.
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activation of the hiv 1 enhancer by the lef 1 HMG Protein on nucleosome assembled dna in vitro
Genes & Development, 1995Co-Authors: Philip L Sheridan, C T Sheline, K Cannon, Michael J Pazin, James T Kadonaga, Katherine A JonesAbstract:: 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.
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the hlef tcf 1 alpha HMG Protein contains a context dependent transcriptional activation domain that induces the tcr alpha enhancer in t cells
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
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The hLEF/TCF-1 alpha HMG Protein contains a context-dependent transcriptional activation domain that induces the TCR alpha enhancer in T cells.
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
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a thymus specific member of the HMG Protein family regulates the human t cell receptor c alpha enhancer
Genes & Development, 1991Co-Authors: Marian L Waterman, Wolfgang H Fischer, Katherine A JonesAbstract:: The human T cell-specific transcription factor TCF-1 alpha plays a key role in the tissue-specific activation of the T cell receptor (TCR) C alpha enhancer and binds to pyrimidine-rich elements (5'-PyCTTTG-3') present in a variety of other T cell-specific control regions. Using amino acid sequence information derived from the DNA affinity-purified Protein, we have now isolated cDNA clones encoding TCF-1 alpha. The TCF-1 alpha cDNA contains a single 68-amino-acid domain that is homologous to a region conserved among high-mobility group (HMG) and nonhistone chromosomal Proteins. Expression of full-length and mutant cDNA clones in bacteria reveal that the single HMG motif, which is predicted to contain two extended alpha-helical segments, is sufficient to direct the sequence-specific binding of TCF-1 alpha to DNA. Northern blot experiments demonstrate further that TCF-1 alpha mRNA is highly tissue specific, found primarily in the thymus or T cell lines. The immature CEM T cell line expresses relatively low levels of TCF-1 alpha mRNA, which are increased upon activation of these cells by phorbol esters. Interestingly, the cloned TCF-1 alpha Protein is a potent transcriptional activator of the human TCR alpha enhancer in nonlymphoid cell lines, whereas the activity of the endogenous Protein in T cell lines is strongly dependent on an additional T cell-specific Protein that interacts with the core enhancer. TCF-1 alpha is currently unique among the newly emerging family of DNA-binding regulatory Proteins that share the HMG motif in that it is a highly tissue-specific RNA polymerase II transcription factor.
Marian L Waterman - One of the best experts on this subject based on the ideXlab platform.
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the hlef tcf 1 alpha HMG Protein contains a context dependent transcriptional activation domain that induces the tcr alpha enhancer in t cells
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
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The hLEF/TCF-1 alpha HMG Protein contains a context-dependent transcriptional activation domain that induces the TCR alpha enhancer in T cells.
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
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a thymus specific member of the HMG Protein family regulates the human t cell receptor c alpha enhancer
Genes & Development, 1991Co-Authors: Marian L Waterman, Wolfgang H Fischer, Katherine A JonesAbstract:: The human T cell-specific transcription factor TCF-1 alpha plays a key role in the tissue-specific activation of the T cell receptor (TCR) C alpha enhancer and binds to pyrimidine-rich elements (5'-PyCTTTG-3') present in a variety of other T cell-specific control regions. Using amino acid sequence information derived from the DNA affinity-purified Protein, we have now isolated cDNA clones encoding TCF-1 alpha. The TCF-1 alpha cDNA contains a single 68-amino-acid domain that is homologous to a region conserved among high-mobility group (HMG) and nonhistone chromosomal Proteins. Expression of full-length and mutant cDNA clones in bacteria reveal that the single HMG motif, which is predicted to contain two extended alpha-helical segments, is sufficient to direct the sequence-specific binding of TCF-1 alpha to DNA. Northern blot experiments demonstrate further that TCF-1 alpha mRNA is highly tissue specific, found primarily in the thymus or T cell lines. The immature CEM T cell line expresses relatively low levels of TCF-1 alpha mRNA, which are increased upon activation of these cells by phorbol esters. Interestingly, the cloned TCF-1 alpha Protein is a potent transcriptional activator of the human TCR alpha enhancer in nonlymphoid cell lines, whereas the activity of the endogenous Protein in T cell lines is strongly dependent on an additional T cell-specific Protein that interacts with the core enhancer. TCF-1 alpha is currently unique among the newly emerging family of DNA-binding regulatory Proteins that share the HMG motif in that it is a highly tissue-specific RNA polymerase II transcription factor.
Wolfgang H Fischer - One of the best experts on this subject based on the ideXlab platform.
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a thymus specific member of the HMG Protein family regulates the human t cell receptor c alpha enhancer
Genes & Development, 1991Co-Authors: Marian L Waterman, Wolfgang H Fischer, Katherine A JonesAbstract:: The human T cell-specific transcription factor TCF-1 alpha plays a key role in the tissue-specific activation of the T cell receptor (TCR) C alpha enhancer and binds to pyrimidine-rich elements (5'-PyCTTTG-3') present in a variety of other T cell-specific control regions. Using amino acid sequence information derived from the DNA affinity-purified Protein, we have now isolated cDNA clones encoding TCF-1 alpha. The TCF-1 alpha cDNA contains a single 68-amino-acid domain that is homologous to a region conserved among high-mobility group (HMG) and nonhistone chromosomal Proteins. Expression of full-length and mutant cDNA clones in bacteria reveal that the single HMG motif, which is predicted to contain two extended alpha-helical segments, is sufficient to direct the sequence-specific binding of TCF-1 alpha to DNA. Northern blot experiments demonstrate further that TCF-1 alpha mRNA is highly tissue specific, found primarily in the thymus or T cell lines. The immature CEM T cell line expresses relatively low levels of TCF-1 alpha mRNA, which are increased upon activation of these cells by phorbol esters. Interestingly, the cloned TCF-1 alpha Protein is a potent transcriptional activator of the human TCR alpha enhancer in nonlymphoid cell lines, whereas the activity of the endogenous Protein in T cell lines is strongly dependent on an additional T cell-specific Protein that interacts with the core enhancer. TCF-1 alpha is currently unique among the newly emerging family of DNA-binding regulatory Proteins that share the HMG motif in that it is a highly tissue-specific RNA polymerase II transcription factor.
Peter Carlsson - One of the best experts on this subject based on the ideXlab platform.
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the hlef tcf 1 alpha HMG Protein contains a context dependent transcriptional activation domain that induces the tcr alpha enhancer in t cells
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
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The hLEF/TCF-1 alpha HMG Protein contains a context-dependent transcriptional activation domain that induces the TCR alpha enhancer in T cells.
Genes & Development, 1993Co-Authors: Peter Carlsson, Marian L Waterman, Katherine A JonesAbstract:hLEF/TCF-Iot is a lymphoid cell-specific HMG Protein that activates the distal enhancer of the gene encoding the a-subunit of the T-cell receptor (TCRot). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCRa enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion Proteins can activate a GAL4-substituted TCRcz enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCRc~ enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched Protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCRoL enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.
Mark C Williams - One of the best experts on this subject based on the ideXlab platform.
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the yeast HMG Protein hmo1 alters nucleosome structure
Biophysical Journal, 2014Co-Authors: Micah J Mccauley, Nicole A Becker, Molly Nelson Holt, Uma Muthurajan, Karolin Luger, James L Maher, Nathan Israeloff, Mark C WilliamsAbstract:High-mobility group (HMG) Proteins are DNA binding Proteins believed to play a significant role in reorganizing the conformation of chromatin, which facilitates transcription, replication and DNA repair. HMO1 is a dual box HMGB Protein from Saccharomyces cerevisiae that generates strong bends in DNA. These bends disrupt chromatin, possibly opening binding sites for other factors. To study this architectural function, we have observed the conformation of nucleosomes deposited on a surface using an atomic force microscope (AFM). The AFM images are obtained by probing nucleosome arrays in liquid, revealing tightly compacted nucleosomes, which are characterized by small inter-core particle distances. Increasing concentrations of HMO1 decrease average core particle distances, which indicates that these Proteins alter chromatin structure. Complementary experiments utilize Optical Tweezers (OT) to unfold arrays of nucleosome core particles, probing structural stability. OT data shows that forces of 10 - 20 pN are required to fully disrupt the core particles, and further experiments are expected to reveal the stability of the nucleosomes in the presence of HMO1.