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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ada gene of Escherichia coli encodes a 39-kDa protein which serves both as a transcriptional activator of the adaptive response to alkylating agents and as a DNA repair enzyme demethylating O6-methyl-guanine and phosphotriester residues. Here, the isolated Ada protein was found to be readily cleaved into two fragments of similar size by treatment with trypsin, chymotrypsin, subtilisin, or V8 protease. The fragments retained their respective methyltransferase activities. The Ada protein is, therefore, comprised of two stable active domains united by a central hinge region of about 10 amino acids. Post-translational modification of the Ada protein by methylation of a specific cysteine residue in the NH2-terminal domain is known to convert it to an efficient transcriptional activator. This residue has now been identified as Cys-69.
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PMID:Functional domains and methyl acceptor sites of the Escherichia coli ada protein. 316 36

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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PMID:The monomer-binding orphan receptor Rev-Erb represses transcription as a dimer on a novel direct repeat. 765 96

The ada gene of Escherichia coli K-12 encodes the 39-kDa Ada protein, which consists of two domains joined by a hinge region that is sensitive to proteolytic cleavage in vitro. The amino-terminal domain has a DNA methyltransferase activity that repairs the S-diastereoisomer of methylphosphotriesters while the carboxyl-terminal domain has a DNA methyltransferase activity that repairs O6-methylguanine and O4-methylthymine lesions. Transfer of a methyl group to Cys-69 by repair of a methylphosphotriester lesion converts Ada into a transcriptional activator of the ada and alkA genes. Activation of ada, but not alkA, requires elements contained within the carboxyl-terminal domain of Ada. In addition, physiologically relevant concentrations of the unmethylated form of Ada specifically inhibit methylated Ada-promoted ada transcription both in vitro and in vivo and it has been suggested that this phenomenon plays a pivotal role in the down-regulation of the adaptive response. A set of site-directed mutations were generated within the hinge region, changing the lysine residue at position 178 to leucine, valine, glycine, tyrosine, arginine, cysteine, proline, and serine. All eight mutant proteins have deficiencies in their ability to activate ada transcription in the presence or absence of a methylating agent but are proficient in alkA activation. AdaK178P (lysine 178 changed to proline) is completely defective for the transcriptional activation function of ada while it is completely proficient for transcriptional activation of alkA. In addition, AdaK178P possesses both classes of DNA repair activities both in vitro and in vivo. Transcriptional activation of ada does not occur if both the amino- and carboxyl-terminal domains are produced separately within the same cell. The mutation at position 178 might interfere with activation of ada transcription by changing a critical contact with RNA polymerase, by causing a conformational change of Ada, or by interfering with the communication of conformational information between the amino- and the carboxyl-terminal domains. These results indicate that the hinge region of Ada is important for ada but not alkA transcription and further support the notion that the mechanism(s) by which Ada activates ada transcription differs from that by which it activates transcription at alkA.
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PMID:Alteration of lysine 178 in the hinge region of the Escherichia coli ada protein interferes with activation of ada, but not alkA, transcription. 786 1

Mastomys natalensis is a rodent of African origin afflicted with a very high incidence of skin tumors (keratoacanthomas and squamous carcinomas), which are associated with a papillomavirus, M. natalensis papillomavirus (MnPV). We have determined the genomic sequence of MnPV, which has a size of 7687 bp. The genomic organization is similar to that of other papillomaviruses, with open reading frames E6, E7, E1, E2, and E4 in the early and L2 and L1 in the late region. Due to an unusually large hinge region, the transcriptional activator E2 has a size of 542 amino acids rather than 400 to 460 amino acids, as in other papillomaviruses. An open reading frame E5 coding for a small hydrophobic membrane protein is missing, as is the case for some cutaneous human papillomaviruses (HPV). This fact, together with the composition of cis-responsive elements in its long control region and phylogenetic evaluation of segments of its E6, E1, and L1 genes, indicates a relationship of MnPV to the cottontail rabbit papillomavirus and several HPV types found in lesions of cutaneous epithelia, in particular to those that are associated with epidermodysplasia verruciformis. MnPV may be a useful model system for tumorigenesis of cutaneous epithelia in humans.
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PMID:The Mastomys natalensis papillomavirus: nucleotide sequence, genome organization, and phylogenetic relationship of a rodent papillomavirus involved in tumorigenesis of cutaneous epithelia. 829 Dec 35

To assess the importance of various regions of the androgen receptor (AR) in transcriptional regulation, we have compared its activation functions (AFs) in yeast and mammalian cells. The receptor's amino-terminal region contains a major transcriptional activator (AF-1) in both cell types, whereas AF-2 in the ligand-binding domain (LBD) is very weak in mammalian cells but clearly functional in the yeast. Hormone-binding ability of LBD is mandatory for AF-2 to operate, as illustrated by mutated LBD constructs. The activity of AF-2 in yeast is severely attenuated when the hinge region is attached to LBD, suggesting that the former region modulates AF-2 in vivo, probably by presenting an interface for interacting proteins.
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PMID:The presence of a transcription activation function in the hormone-binding domain of androgen receptor is revealed by studies in yeast cells. 925 51

We constructed an in vivo reporter system to measure the activity of CooA as the transcriptional activator and showed that the recombinant CooA was active as the transcriptional activator in the presence of CO even in E. coli cells. A dominant positive mutant of CooA, in which Met131 was replaced by Leu, was isolated by a random mutagenesis with this reporter system. The electronic absorption spectra of M131L mutant were identical to those of wild type CooA in oxidized (Fe3+), reduced (Fe2+), and CO-bound (CO-Fe2+) state, indicating that the coordination structure and environment of the heme were not changed by this mutation. Methionine at position 131 was the carboxyl-terminal end of the heme-binding domain of CooA, which would be adjacent to the hinge region connecting the heme-binding domain and the DNA-binding domain.
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PMID:Single transduction in the transcriptional activator CooA containing a heme-based CO sensor: isolation of a dominant positive mutant which is active as the transcriptional activator even in the absence of CO. 939 45

The multifunctional 39 kDa Escherichia coli Ada protein (O6-methylguanine-DNA methyltransferase) (EC 2.1.1.63), product of the ada gene, is a monomeric globular polypeptide with two distinct alkylacceptor activities located in two domains. The two domains are of nearly equal size and are connected by a hinge region. The Ada protein accepts stoichiometrically the alkyl group from O6-alkylguanine in DNA at the Cys-321 residue and from alkyl phosphotriester at the Cys-69 residue. This protein functions in DNA repair by direct dealkylation of mutagenic O6-alkylguanine. The protein methylated at Cys-69 becomes a transcriptional activator of the genes in the ada regulon, including its own. Each of the two domains functions independently as an alkyl acceptor. The purified homogeneous protein is unstable at 37 degrees C and spontaneously loses about 30% of its secondary structure in less than 30 min concomitant with a complete loss of activity. However, sedimentation equilibrium studies indicated that the inactive protein remains in the monomeric form without aggregation. Furthermore, electrospray mass spectroscopic analysis indicated the absence of oxidation of the inactive protein. This temperature-dependent inactivation of the Ada protein is inhibited by DNA. In the presence of increasing concentrations of urea or guanidine, the protein gradually loses more than 80% of its structure. The two alkyl acceptor activities appear to be differentially sensitive to unfolding and the phosphotriester methyltransferase activity is resistant to 7 M urea. The partial or complete unfolding induced by urea or guanidine is completely reversed within seconds by removal of the denaturant. The heat-coagulated protein can also be restored to full activity by cycling it through treatment with 8 M urea or 6 M guanidine. These results suggest that the nascent or unfolded Ada polypeptide folds to a metastable form which is active and that the thermodynamically stable structure is partially unfolded and inactive.
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PMID:Reversible folding of Ada protein (O6-methylguanine-DNA methyltransferase) of Escherichia coli. 948 44

Application of the "essential dynamics" method to the NMR cluster of structures for the R2R3 DNA-binding domain of the mouse c-Myb transcriptional activator is described. Using this method, large concerted fluctuations of atoms are extracted showing a hinge-bending motion between the two (R2 and R3) Myb repeats on the basis of NMR data alone. Molecular dynamics simulation of the same protein allowed quantitative comparison of the large concerted motions calculated from experimental and theoretical data, showing a significant degree of similarity. Detailed inspection of the motions reveals a conserved proline that plays a key role in determining hinge flexibility. The proline-to-alanine mutation at this position, which has previously been characterized biochemically, was subjected to molecular dynamics and subsequent essential dynamics analysis. The hinge-bending motion between the two repeats was found to be enhanced for the mutant. The approach described should have general applications, predicting the effect of mutations on protein dynamic properties of other proteins.
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PMID:Essential dynamics from NMR clusters: dynamic properties of the Myb DNA-binding domain and a hinge-bending enhancing variant. 957 Oct 87

CooA, a heme-containing transcriptional activator, binds CO to the heme moiety and then undergoes a structural change that promotes the specific binding to the target DNA. To elucidate the activation mechanism coupled to CO binding, we investigated the CO-dependent structural transition of CooA with small-angle X-ray scattering (SAXS). In the absence of CO, the radius of gyration Rg and the second virial coefficient (A2) were 25.3(+/-0.5)A and -0.39(+/-0.25) x 10(-4)ml mol g(-2), respectively. CO binding caused a slight increase in Rg (by 0.5A) and a marked decrease in A2 (by 5.09 x 10(-4)ml mol g(-2)). The observed decrease in A2 points to higher attractive interactions between CO-bound CooA molecules in solution compared with CO-free CooA. Although the minor alternation of Rg rules out changes in the overall structure, the marked change in the surface properties points to a CO-induced conformational transition. The experimental Rg and SAXS curves of the two states did not agree with the crystal structure of CO-free CooA. We thus simulated the solution structures of CooA based on the experimental data using rigid-body refinements as well as low-resolution model reconstructions. Both results demonstrate that the hinge region connecting the N-terminal heme domain and C-terminal DNA-binding domain is kinked in CO-free CooA, so that the two domains are positioned close to each other. The CO-dependent structural change observed by SAXS corresponds to a slight swing of the DNA-binding domains away from the heme domains coupled with their rotation by about 8 degrees around the axis of 2-fold symmetry.
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PMID:Activation mechanisms of transcriptional regulator CooA revealed by small-angle X-ray scattering. 1528 77

Papillomaviruses are small DNA viruses which establish persistent infection in the epithelial tissue of various animal species. Three papillomavirus proteins encoded by the bovine papillomavirus type 1 E2 open reading frame have a common C-terminal DNA binding and dimerization domain and function as dimeric proteins in the regulation of viral gene expression, genome replication, and maintenance. The full-length E2 protein, expressed usually at the lowest level of the three, is an activator, while shorter forms of E2, lacking the transactivation domain, serve as repressors of replication and transcription. In virally infected cells, the full-length E2 protein forms heterodimers with repressor forms of the E2 protein and the biological activities of such heterodimers are poorly known. In order to study the functionality of E2 heterodimers, we joined the full-length E2 protein and E2 repressor by a flexible polypeptide hinge so that they formed a single-chain intramolecular dimer. The single-chain E2 heterodimers folded correctly to form genuine pseudodimers capable of binding to the specific E2 protein binding site with high affinity. Characterization of the activities of this protein in transcription showed that it functions as an effective transcriptional activator, which is comparable to what was found for the full-length E2 protein. The single-chain heterodimer is dependent to some extent on Brd4 protein and is able to support papillomavirus origin replication; however, it does not support the partitioning of the multimeric E2 binding site containing plasmids in dividing cells. Our results suggest that E2 heterodimers serve as activators of transcription and replication during the viral life cycle.
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PMID:Characterization of the functional activities of the bovine papillomavirus type 1 E2 protein single-chain heterodimers. 1694 89


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