An Integrated Computational and Experimental Binding Study Identifies the DNA Binding Domain as the Putative Binding Site of Novel Pyrimidinetrione Signal Transducer and Activator of Transcription 3 (STAT3) Inhibitors

ABSTRACT Pot1 is a single-stranded-DNA-binding protein that recognizes telomeric G-strand DNA. It is essential for telomere capping in Saccharomyces pombe and regulates telomere length in humans. Human Pot1 also interacts with proteins that bind the duplex region of the telomeric tract. Thus, like Cdc13 from S. cerevisiae, Pot 1 may have multiple roles at the telomere. We show here that endogenous chicken Pot1 (cPot1) is present at telomeres during periods of the cell cycle when t loops are thought to be present. Since cPot1 can bind internal loops and directly adjacent DNA-binding sites, it is likely to fully coat and protect both G-strand overhangs and the displaced G strand of a t loop. The minimum binding site of cPot1 is double that of the S. pombe DNA-binding domain. Although cPot can self associate, dimerization is not required for DNA binding and hence does not explain the binding-site duplication. Instead, the DNA-binding domain appears to be extended to contain a second binding motif in addition to the conserved oligonucleotide-oligosaccharide (OB) fold present in other G-strand-binding proteins. This second motif could be another OB fold. Although dimerization is inefficient in vitro, it may be regulated in vivo and could promote association with other telomere proteins and/or telomere compaction.

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Dissection of a carboxy-terminal region of the yeast regulatory protein RAP1 with effects on both transcriptional activation and silencing

Molecular and Cellular Biology ◽

10.1128/mcb.12.3.1209-1217.1992 ◽

1992 ◽

Vol 12 (3) ◽

pp. 1209-1217

Author(s):

C F Hardy ◽

D Balderes ◽

D Shore

Keyword(s):

Dna Binding ◽

Binding Site ◽

Transcriptional Activation ◽

Binding Sites ◽

Binding Protein ◽

Binding Domain ◽

Dominant Negative Effect ◽

Dna Binding Domain ◽

Wild Type ◽

Carboxy Terminal

RAP1 is an essential sequence-specific DNA-binding protein in Saccharomyces cerevisiae whose binding sites are found in a large number of promoters, where they function as upstream activation sites, and at the silencer elements of the HMR and HML mating-type loci, where they are important for repression. We have examined the involvement of specific regions of the RAP1 protein in both repression and activation of transcription by studying the properties of a series of hybrid proteins containing RAP1 sequences fused to the DNA-binding domain of the yeast protein GAL4 (amino acids 1 to 147). GAL4 DNA-binding domain/RAP1 hybrids containing only the carboxy-terminal third of the RAP1 protein (which lacks the RAP1 DNA-binding domain) function as transcriptional activators of a reporter gene containing upstream GAL4 binding sites. Expression of some hybrids from the strong ADH1 promoter on multicopy plasmids has a dominant negative effect on silencers, leading to either partial or complete derepression of normally silenced genes. The GAL4/RAP1 hybrids have different effects on wild-type and several mutated but functional silencers. Silencers lacking either an autonomously replicating sequence consensus element or the RAP1 binding site are strongly derepressed, whereas the wild-type silencer or a silencer containing a deletion of the binding site for another silencer-binding protein, ABF1, are only weakly affected by hybrid expression. By examining a series of GAL4 DNA-binding domain/RAP1 hybrids, we have mapped the transcriptional activation and derepression functions to specific parts of the RAP1 carboxy terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

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Dissection of a carboxy-terminal region of the yeast regulatory protein RAP1 with effects on both transcriptional activation and silencing.

Molecular and Cellular Biology ◽

10.1128/mcb.12.3.1209 ◽

1992 ◽

Vol 12 (3) ◽

pp. 1209-1217 ◽

Cited By ~ 49

Author(s):

C F Hardy ◽

D Balderes ◽

D Shore

Keyword(s):

Dna Binding ◽

Binding Site ◽

Transcriptional Activation ◽

Binding Sites ◽

Binding Protein ◽

Binding Domain ◽

Dominant Negative Effect ◽

Dna Binding Domain ◽

Wild Type ◽

Carboxy Terminal

RAP1 is an essential sequence-specific DNA-binding protein in Saccharomyces cerevisiae whose binding sites are found in a large number of promoters, where they function as upstream activation sites, and at the silencer elements of the HMR and HML mating-type loci, where they are important for repression. We have examined the involvement of specific regions of the RAP1 protein in both repression and activation of transcription by studying the properties of a series of hybrid proteins containing RAP1 sequences fused to the DNA-binding domain of the yeast protein GAL4 (amino acids 1 to 147). GAL4 DNA-binding domain/RAP1 hybrids containing only the carboxy-terminal third of the RAP1 protein (which lacks the RAP1 DNA-binding domain) function as transcriptional activators of a reporter gene containing upstream GAL4 binding sites. Expression of some hybrids from the strong ADH1 promoter on multicopy plasmids has a dominant negative effect on silencers, leading to either partial or complete derepression of normally silenced genes. The GAL4/RAP1 hybrids have different effects on wild-type and several mutated but functional silencers. Silencers lacking either an autonomously replicating sequence consensus element or the RAP1 binding site are strongly derepressed, whereas the wild-type silencer or a silencer containing a deletion of the binding site for another silencer-binding protein, ABF1, are only weakly affected by hybrid expression. By examining a series of GAL4 DNA-binding domain/RAP1 hybrids, we have mapped the transcriptional activation and derepression functions to specific parts of the RAP1 carboxy terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

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Role of the IE62 Consensus Binding Site in Transactivation by the Varicella-Zoster Virus IE62 Protein

Journal of Virology ◽

10.1128/jvi.02522-09 ◽

2010 ◽

Vol 84 (8) ◽

pp. 3767-3779 ◽

Cited By ~ 13

Author(s):

Kris White ◽

Hua Peng ◽

John Hay ◽

William T. Ruyechan

Keyword(s):

Dna Binding ◽

Varicella Zoster Virus ◽

Binding Site ◽

Consensus Sequence ◽

Binding Domain ◽

Dna Binding Domain ◽

Consensus Binding Site ◽

Mobility Shift ◽

Varicella Zoster ◽

Mobility Shift Assay

ABSTRACT The varicella-zoster virus (VZV) IE62 protein is the major transcriptional activator. IE62 is capable of associating with DNA both nonspecifically and in a sequence-specific manner via a consensus binding site (5′-ATCGT-3′). However, the function of the consensus site is poorly understood, since IE62 efficiently transactivates promoter elements lacking this sequence. In the work presented here, sequence analysis of the VZV genome revealed the presence of 245 IE62 consensus sites throughout the genome. Some 54 sites were found to be present within putative VZV promoters. Electrophoretic mobility shift assay (EMSA) experiments using an IE62 fragment containing the IE62 DNA-binding domain and duplex oligonucleotides that did or did not contain the IE62 consensus binding sequence yielded KD (equilibrium dissociation constant) values in the nanomolar range. Further, the IE62 DNA binding domain was shown to have a 5-fold-increased affinity for its consensus site compared to nonconsensus sequences. The effect of consensus site presence and position on IE62-mediated activation of native VZV and model promoters was examined using site-specific mutagenesis and transfection and superinfection reporter assays. In all promoters examined, the consensus sequence functioned as a distance-dependent repressive element. Protein recruitment assays utilizing the VZV gI promoter indicated that the presence of the consensus site increased the recruitment of IE62 but not Sp1. These data suggest a model where the IE62 consensus site functions to down-modulate IE62 activation, and interaction of IE62 with this sequence may result in loss or decrease of the ability of IE62 to recruit cellular factors needed for full promoter activation.

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Crystallization and Preliminary X-ray Analysis of the DNA Binding Domain of the Hin Recombinase with Its DNA Binding Site

Journal of Molecular Biology ◽

10.1006/jmbi.1993.1443 ◽

1993 ◽

Vol 232 (3) ◽

pp. 982-986

Author(s):

Jin-An Feng ◽

Melvin Simon ◽

David P. Mack ◽

Peter B. Dervan ◽

Reid C. Johnson ◽

...

Keyword(s):

Dna Binding ◽

Binding Site ◽

Binding Domain ◽

Dna Binding Domain ◽

X Ray ◽

Dna Binding Site ◽

Hin Recombinase

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Smooth Muscle-Specific Genes Are Differentially Sensitive to Inhibition by Elk-1

Molecular and Cellular Biology ◽

10.1128/mcb.25.22.9874-9885.2005 ◽

2005 ◽

Vol 25 (22) ◽

pp. 9874-9885 ◽

Cited By ~ 47

Author(s):

Jiliang Zhou ◽

Guoqing Hu ◽

B. Paul Herring

Keyword(s):

Smooth Muscle ◽

Dna Binding ◽

Binding Site ◽

Serum Response Factor ◽

Specific Protein ◽

Binding Domain ◽

Dominant Negative ◽

Differential Sensitivity ◽

Dna Binding Domain ◽

Mobility Shift

ABSTRACT Understanding the mechanism of smooth muscle cell (SMC) differentiation will provide the foundation for elucidating SMC-related diseases, such as atherosclerosis, restenosis, and asthma. In the current study, overexpression of Elk-1 in SMCs down-regulated expression of several endogenous smooth muscle-restricted proteins, including telokin, SM22α, and smooth muscle α-actin. In contrast, down-regulation of endogenous Elk-1 in smooth muscle cells increased the expression of only telokin and SM22α, suggesting that smooth muscle-specific promoters are differentially sensitive to the inhibitory effects of Elk-1. Consistent with this, overexpression of the DNA binding domain of Elk-1, which acts as a dominant-negative protein by displacing endogenous Elk-1, enhanced the expression of telokin and SM22α without affecting expression of smooth muscle α-actin. Elk-1 suppressed the activity of smooth muscle-restricted promoters, including the telokin promoter that does not contain a consensus Elk-1 binding site, through its ability to block myocardin-induced activation of the promoters. Gel mobility shift and chromatin immunoprecipitation assays revealed that Elk-1 binds to a nonconsensus binding site in the telokin promoter and Elk-1 binding is dependent on serum response factor (SRF) binding to a nearby CArG box. Although overexpression of the SRF-binding B-box domain of Elk-1 is sufficient to repress the myocardin activation of the telokin promoter, this repression is not as complete as that seen with an Elk-1 fragment that includes the DNA binding domain. In addition, reporter gene assays demonstrate that an intact Elk-1 binding site in the telokin promoter is required for Elk-1 to maximally inhibit promoter activity. Together, these data suggest that the differential sensitivity of smooth muscle-specific genes to inhibition by Elk-1 may play a role in the complex changes in smooth muscle-specific protein expression that are observed under pathological conditions.

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The monomer-binding orphan receptor Rev-Erb represses transcription as a dimer on a novel direct repeat.

Molecular and Cellular Biology ◽

10.1128/mcb.15.9.4791 ◽

1995 ◽

Vol 15 (9) ◽

pp. 4791-4802 ◽

Cited By ~ 132

Author(s):

H P Harding ◽

M A Lazar

Keyword(s):

Retinoic Acid ◽

Dna Binding ◽

Binding Site ◽

Binding Domain ◽

Luciferase Reporter ◽

Dna Binding Domain ◽

Transactivation Domain ◽

Direct Repeats ◽

Basal Transcription ◽

C Terminus

Rev-Erb is an orphan nuclear receptor which binds as a monomer to the thyroid/retinoic acid receptor half-site AGGTCA flanked 5' by an A/T-rich sequence, referred to here as a Rev monomer site. Fusion of Rev-Erb to the DNA binding domain of yeast GAL4 strongly repressed basal transcription of a GAL4-luciferase reporter gene as a result of the presence of a C-terminal domain containing both the hinge and heptad repeat regions. Nevertheless, wild-type Rev-Erb did not repress basal transcription from the Rev monomer binding site. Therefore, a DNA binding site selection strategy was devised to test the hypothesis that Rev-Erb may function on a different site as a dimer. This approach identified sequences containing two Rev monomer sites arranged as direct repeats with the AGGTCA motifs separated by 2 bp (Rev-DR2). Remarkably, Rev-Erb bound as a homodimer to Rev-DR2 but not to other direct repeats or to a standard DR2 sequence. The DNA binding domain contained all of the determinants for Rev-DR2-specific homodimerization. Rev-Erb bound cooperatively as a homodimer to Rev-DR2, and this interaction was 5 to 10 times more stable than Rev-Erb monomer binding to the Rev monomer site. Functionally, Rev-Erb markedly repressed the basal activity of a variety of promoters with a strong Rev-DR2 specificity. The C terminus was required for this repression, consistent with the GAL4 results. However, the Rev-DR2 specificity did not require the C terminus in vivo, since fusion of C-terminally truncated Rev-Erb to a heterologous transactivation domain created a transcriptional activator specific for Rev-DR2. In addition to idealized Rev-DR2 sites, Rev-Erb also repressed basal as well as retinoic acid-induced transcription from a naturally occurring Rev-DR2 in the CRBPI gene. Thus, although Rev-Erb is distinguished from other thyroid/steroid receptor superfamily members by its ability to bind DNA as a monomer, it functions as a homodimer to repress transcription of genes containing a novel DR2 element.

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