Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 33
Filtrar
1.
Pharm Res ; 40(6): 1383-1397, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36869246

RESUMO

PURPOSE: Reversible self-association (RSA) has long been a concern in therapeutic monoclonal antibody (mAb) development. Because RSA typically occurs at high mAb concentrations, accurate assessment of the underlying interaction parameters requires explicitly addressing hydrodynamic and thermodynamic nonideality. We previously examined the thermodynamics of RSA for two mAbs, C and E, in phosphate buffered saline (PBS). Here we continue to explore the mechanistic aspects of RSA by examining the thermodynamics of both mAbs under reduced pH and salt conditions. METHODS: Dynamic light scattering and sedimentation velocity (SV) studies were conducted for both mAbs at multiple protein concentrations and temperatures, with the SV data analyzed via global fitting to determine best-fit models, interaction energetics, and nonideality contributions. RESULTS: We find that mAb C self-associates isodesmically irrespective of temperature, and that association is enthalpically driven but entropically penalized. Conversely, mAb E self-associates cooperatively and via a monomer-dimer-tetramer-hexamer reaction pathway. Moreover, all mAb E reactions are entropically driven and enthalpically modest or minimal. CONCLUSIONS: The thermodynamics for mAb C self-association are classically seen as originating from van der Waals interactions and hydrogen bonding. However, relative to the energetics we determined in PBS, self-association must also be linked to proton release and/or ion uptake events. For mAb E, the thermodynamics implicate electrostatic interactions. Furthermore, self-association is instead linked to proton uptake and/or ion release, and primarily by tetramers and hexamers. Finally, although the origins of mAb E cooperativity remain unclear, ring formation remains a possibility whereas linear polymerization reactions can be eliminated.


Assuntos
Anticorpos Monoclonais , Prótons , Anticorpos Monoclonais/metabolismo , Cloreto de Sódio , Difusão Dinâmica da Luz , Termodinâmica
2.
Pharm Res ; 38(2): 243-255, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33604786

RESUMO

PURPOSE: Reversible self-association (RSA) remains a challenge in the development of therapeutic monoclonal antibodies (mAbs). We recently analyzed the energetics of RSA for five IgG mAbs (designated as A-E) under matched conditions and using orthogonal methods. Here we examine the thermodynamics of RSA for two of the mAbs that showed the strongest evidence of RSA (mAbs C and E) to identify underlying mechanisms. METHODS: Concentration-dependent dynamic light scattering and sedimentation velocity (SV) studies were carried out for each mAb over a range of temperatures. Because self-association was weak, the SV data were globally analyzed via direct boundary fitting to identify best-fit models, accurately determine interaction energetics, and account for the confounding effects of thermodynamic and hydrodynamic nonideality. RESULTS: mAb C undergoes isodesmic self-association at all temperatures examined, with the energetics indicative of an enthalpically-driven reaction offset by a significant entropic penalty. By contrast, mAb E undergoes monomer-dimer self-association, with the reaction being entropically-driven and comprised of only a small enthalpic contribution. CONCLUSIONS: Classical interpretations implicate van der Waals interactions and H-bond formation for mAb C RSA, and electrostatic interactions for mAb E. However, noting that RSA is likely coupled to additional equilibria, we also discuss the limitations of such interpretations.


Assuntos
Anticorpos Monoclonais/química , Termodinâmica , Anticorpos Monoclonais/uso terapêutico , Química Farmacêutica , Difusão Dinâmica da Luz , Multimerização Proteica , Eletricidade Estática
3.
Nat Commun ; 9(1): 1337, 2018 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-29626214

RESUMO

Glucocorticoids (GCs) are potent repressors of NF-κB activity, making them a preferred choice for treatment of inflammation-driven conditions. Despite the widespread use of GCs in the clinic, current models are inadequate to explain the role of the glucocorticoid receptor (GR) within this critical signaling pathway. GR binding directly to NF-κB itself-tethering in a DNA binding-independent manner-represents the standing model of how GCs inhibit NF-κB-driven transcription. We demonstrate that direct binding of GR to genomic NF-κB response elements (κBREs) mediates GR-driven repression of inflammatory gene expression. We report five crystal structures and solution NMR data of GR DBD-κBRE complexes, which reveal that GR recognizes a cryptic response element between the binding footprints of NF-κB subunits within κBREs. These cryptic sequences exhibit high sequence and functional conservation, suggesting that GR binding to κBREs is an evolutionarily conserved mechanism of controlling the inflammatory response.


Assuntos
NF-kappa B/genética , NF-kappa B/metabolismo , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Elementos de Resposta , Substituição de Aminoácidos , Animais , Sítios de Ligação/genética , Cristalografia por Raios X , Células HEK293 , Células HeLa , Humanos , Modelos Moleculares , Mutagênese Sítio-Dirigida , NF-kappa B/química , Ressonância Magnética Nuclear Biomolecular , Receptores de Glucocorticoides/química , Fator de Necrose Tumoral alfa/metabolismo
4.
ACS Omega ; 3(2): 2141-2154, 2018 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-29619413

RESUMO

Neuropeptide Y (NPY) is a 36-residue peptide, abundant in the central and peripheral nervous system. The peptide interacts with membrane-bound receptors to control processes such as food intake, vasoconstriction, and memory retention. The N-terminal polyproline sequence of NPY folds back onto a C-terminal α-helix to form a hairpin structure. The hairpin undergoes transient unfolding to allow the monomer to interact with its target membranes and receptors and to form reversible dimers in solution. Using computational, functional, and biophysical approaches, we characterized the role of two conserved tyrosines (Y20 and Y27) located within the hydrophobic core of the hairpin fold. Successive mutation of the tyrosines to more hydrophobic phenylalanines increased the thermal stability of NPY and reduced functional activity, consistent with computational studies predicting a more stable hairpin structure. However, mutant stability was high relative to wild-type: melting temperatures increased by approximately 20 °C for the single mutants (Y20F and Y27F) and by 30 °C for the double mutant (Y20F + Y27F). These findings suggested that the mutations were not just simply enhancing hairpin structure stability, but might also be driving self-association to dimer. Using analytical ultracentrifugation, we determined that the mutations indeed increased self-association, but shifted the equilibrium toward hexamer-like species. Notably, these latter species were not unique to the NPY mutants, but were found to preexist at low levels in the wild-type population. Collectively, the findings indicate that NPY self-association is more complex than previously recognized and that the ensemble of NPY quaternary states is tunable by modulating hairpin hydrophobicity.

5.
J Pharm Sci ; 107(7): 1820-1830, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29571738

RESUMO

Monoclonal antibodies (mAbs) represent a major class of biotherapeutics and are the fastest growing category of biologic drugs on the market. However, mAb development and formulation are often impeded by reversible self-association (RSA), defined as the dynamic exchange of monomers with native-state oligomers. Here, we present a comparative analysis of the self-association properties for 5 IgG mAbs, under matched conditions and using orthogonal methods. Concentration-dependent dynamic light scattering and sedimentation velocity studies revealed that the majority of mAbs examined exhibited weak to moderate RSA. However, because these studies were carried out at mAb concentrations in the mg/mL range, we also observed significant nonideality. Noting that nonideality frequently masks RSA and vice versa, we conducted direct boundary fitting of the sedimentation velocity data to determine stoichiometric binding models, interaction affinities, and nonideality terms for each mAb. These analyses revealed equilibrium constants from micromolar to millimolar and stoichiometric models from monomer-dimer to isodesmic. Moreover, even for those mAbs described by identical models, we observed distinct kinetics of self-association. The accuracy of the models and their corresponding equilibrium constants were addressed using sedimentation equilibrium and simulations. Overall, these results serve as the starting point for the comparative dissection of RSA mechanisms in therapeutic mAbs.


Assuntos
Anticorpos Monoclonais/química , Imunoglobulina G/química , Algoritmos , Difusão Dinâmica da Luz , Humanos , Multimerização Proteica , Termodinâmica , Ultracentrifugação
6.
J Pharm Sci ; 106(8): 2178-2186, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28479353

RESUMO

There are numerous problems with size exclusion chromatography (SEC), which often lead to inaccuracies in protein aggregate characterization. Hence, this study tested sedimentation velocity analytical ultracentrifugation (SV-AUC) as an orthogonal tool to SEC for quantifying the monomer and aggregates in intravenous immunoglobulin (IVIg) formulations. IVIg samples were subjected to agitation stress and analyzed using SEC mobile phases composed of 200 mM sodium phosphate (pH 7.0) with 0, 50, 100, 200, or 400 mM of NaCl. Surprisingly, 400 mM of NaCl was required in the mobile phase to attain complete protein recovery from the SEC column. Significant discrepancies between SEC and SV-AUC were reported when SEC analysis was performed using suboptimal concentrations (e.g., 0, 50, 100, and 200 mM) of NaCl in the mobile phase. The continuous sedimentation coefficient distributions obtained with SV-AUC resolved the high molecular weight species, whereas with SEC the high molecular weight species eluted as a single peak. Only with the orthogonal use of SV-AUC, we were able to develop a robust SEC method for accurate quantitation of monomer and aggregates in unagitated and agitated IVIg samples. Additionally, this article describes a modification to an existing method of quantitating insoluble aggregates from SV-AUC boundary data.


Assuntos
Cromatografia em Gel/métodos , Imunoglobulinas Intravenosas/química , Agregados Proteicos , Ultracentrifugação/métodos , Humanos , Estabilidade Proteica
7.
J Pharm Sci ; 105(12): 3483-3486, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27671238

RESUMO

Training researchers for positions in the United States biopharmaceutical industry has long been driven by academia. This commentary explores how the changing landscape of academic training will impact the industrial workforce, particularly with regard to the development of protein therapeutics in the area of biophysical and higher order structural characterization. We discuss how to balance future training and employment opportunities, how academic-industrial partnerships can help young scientists acquire the skills needed by their future employer, and how an appropriately trained workforce can facilitate the translation of new technology from academic to industrial laboratories. We also present suggestions to facilitate the coordinated development of industrial-academic educational partnerships to develop new training programs, and the ability of students to locate these programs, through the development of authoritative public resources.


Assuntos
Pesquisa Biomédica/educação , Indústria Farmacêutica/educação , Pesquisadores/educação , Ensino/educação , Pesquisa Biomédica/economia , Pesquisa Biomédica/tendências , Indústria Farmacêutica/economia , Indústria Farmacêutica/tendências , Humanos , Estrutura Terciária de Proteína , Parcerias Público-Privadas , Proteínas Recombinantes/química , Pesquisadores/economia , Pesquisadores/tendências , Ensino/tendências
8.
Methods Enzymol ; 562: 363-89, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26412661

RESUMO

Steroid receptors comprise a family of ligand-activated transcription factors. The members include the androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and progesterone receptor (PR). Each receptor controls distinct sets of genes associated with development, metabolism, and homeostasis. Although a qualitative understanding of how individual receptors mediate gene expression has come into focus, quantitative insight remains less clear. As a step toward delineating the physical mechanisms by which individual receptors activate their target genes, we have carried out a systematic dissection of receptor interaction energetics with their multisite regulatory elements. Analytical ultracentrifugation (AUC) has proved indispensable in these studies, in part by revealing the energetics of receptor self-association and its thermodynamic coupling to DNA binding. Here, we discuss these findings in the context of understanding specificity of receptor-mediated gene control. We first highlight the role of sedimentation velocity and sedimentation equilibrium in addressing receptor assembly state, and present a comparative analysis across the receptor family. We then use these results for understanding how receptors assemble at multisite regulatory elements, and hypothesize how these findings might play a role in receptor-specific gene regulation. Finally, we examine receptor behavior in a cellular context, with a view toward linking our in vitro studies with in vivo function.


Assuntos
Receptores de Esteroides/fisiologia , Evolução Molecular , Regulação da Expressão Gênica , Humanos , Mutação de Sentido Incorreto , Regiões Promotoras Genéticas , Ligação Proteica , Multimerização Proteica , Receptores de Esteroides/química , Receptores de Esteroides/isolamento & purificação , Termodinâmica , Ultracentrifugação
9.
Biochemistry ; 54(34): 5306-14, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26267475

RESUMO

The glucocorticoid receptor (GR) is a member of the steroid receptor family of ligand-activated transcription factors. Recent live cell imaging studies have revealed that interactions of GR with chromatin are highly dynamic, with average receptor residence times of only seconds. These findings were surprising because early kinetic studies found that GR-DNA interactions in vitro were much slower, having calculated residence times of minutes to hours. However, these latter analyses were conducted at a time when it was possible to work with only either partially purified holoreceptor or its purified but isolated DNA binding domain. Noting these limitations, we reexamined GR-DNA dissociation kinetics using a highly purified holoreceptor shown to be amenable to rigorous study. We first observe that GR-DNA interactions in vitro are not slow as previously thought but converge with in vivo behavior, having residence times of only seconds to tens of seconds. This rapid exchange is seen at six individual response elements and the multisite MMTV promoter used in live cell imaging. Second, GR dissociation rates are identical for all response elements. Thus, previously observed differences in receptor affinity toward these sequences are not due to differences in off rate but in on rate. Finally, dissociation kinetics are biphasic in character. A minimal kinetic model consistent with the data is that in which DNA-bound GR interconverts between states on a second time scale, with dissociation occurring via a multistep process. We speculate that receptor interconversion in this time frame can be recognized by the coregulatory proteins that interact with GR, leading to unique transcriptional responses.


Assuntos
DNA/metabolismo , Receptores de Glucocorticoides/metabolismo , Animais , Fenômenos Biofísicos , DNA/química , DNA/genética , Pegada de DNA , Humanos , Técnicas In Vitro , Cinética , Vírus do Tumor Mamário do Camundongo/genética , Regiões Promotoras Genéticas , Receptores de Estrogênio/química , Receptores de Estrogênio/genética , Receptores de Estrogênio/metabolismo , Receptores de Glucocorticoides/química , Receptores de Glucocorticoides/genética , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Elementos de Resposta
10.
PLoS One ; 10(5): e0126420, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25997164

RESUMO

Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies.


Assuntos
Ultracentrifugação/métodos , Ultracentrifugação/normas , Calibragem , Reprodutibilidade dos Testes
11.
Proteins ; 82(9): 2078-87, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24648119

RESUMO

Steroid receptors comprise a homologous family of ligand-activated transcription factors. The receptors bind largely identical response elements in vitro, yet regulate distinct gene networks in vivo. This paradox raises the issue of how transcriptional specificity is achieved, particularly if multiple receptor populations are competing for identical sites. Noting that receptor-DNA energetics are a primary force in driving transcriptional activity, differences in interaction energetics among the receptors might underlie receptor-specific transcriptional control. Thermodynamic dissections support this premise-upon assembling at an identical promoter architecture, individual receptors exhibit vast differences in cooperative and self-association energetics. More intriguingly, these parameters distribute in a way that mirrors the evolutionary divergence of the steroid receptor family. For example, the closely related progesterone and glucocorticoid receptors (PR and GR) display little or no self-association but strong intersite cooperativity, whereas the more distantly related estrogen receptor (ER-α) shows inverse behavior. These findings suggest that receptors view genomic promoter architectures as a collection of affinity landscapes; receptors select from this landscape via their unique interaction energetics. To test this idea, we analyzed the cooperative binding energetics of the above three receptors using an array of promoters. We find that cooperativity is not only receptor-specific but also highly promoter-specific. Thus PR shows maximal cooperativity at promoters with closely spaced and in phase binding sites. GR cooperativity is maintained over greater distances, is larger energetically, and shows markedly different phase dependency. Finally, ER-α appears incapable of cooperativity regardless of promoter architecture, consistent with its more distant phylogeny.


Assuntos
Receptor alfa de Estrogênio/genética , Regiões Promotoras Genéticas/genética , Receptores de Glucocorticoides/genética , Receptores de Progesterona/genética , Elementos de Resposta/genética , Sítios de Ligação , Proteínas de Ligação a DNA/metabolismo , Receptor alfa de Estrogênio/metabolismo , Ligação Proteica , Estrutura Terciária de Proteína , Receptores de Glucocorticoides/metabolismo , Receptores de Progesterona/metabolismo , Termodinâmica , Transcrição Gênica
12.
Nucleic Acids Res ; 42(2): 691-700, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24064251

RESUMO

Steroid receptors comprise an evolutionarily conserved family of transcription factors. Although the qualitative aspects by which individual receptors regulate transcription are well understood, a quantitative perspective is less clear. This is primarily because receptor function is considerably more complex than that of classical regulatory factors such as phage or bacterial repressors. Here we discuss recent advances in placing receptor-specific transcriptional regulation on a more quantitative footing, specifically focusing on the role of macromolecular interaction energetics. We first highlight limitations and challenges associated with traditional approaches for assessing the role of energetics (more specifically, binding affinity) with functional outcomes such as transcriptional activation. We next demonstrate how rigorous in vitro measurements and straightforward interaction models quantitatively relate energetics to transcriptional activity within the cell, and follow by discussing why such an approach is unexpectedly effective in explaining complex functional behavior. Finally, we examine the implications of these findings for considering the unique gene regulatory properties of the individual receptors.


Assuntos
Regulação da Expressão Gênica , Receptores de Esteroides/metabolismo , Elementos de Resposta , Transcrição Gênica , DNA/metabolismo , Ligação Proteica
13.
J Mol Biol ; 425(22): 4223-35, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-23917122

RESUMO

Steroid receptors comprise a homologous family of ligand-activated transcription factors. The members include androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and progesterone receptor (PR). Phylogenetic studies demonstrate that AR, GR, MR, and PR are most closely related, falling into subgroup 3C. ER is more distantly related, falling into subgroup 3A. To determine the quantitative basis by which receptors generate their unique transcriptional responses, we are systematically dissecting the promoter-binding energetics of all receptors under a single "standard state" condition. Here, we examine the self-assembly and promoter-binding energetics of full-length AR and a mutant associated with prostate cancer, T877A. We first demonstrate that both proteins exist only as monomers, showing no evidence of dimerization. Although this result contradicts the traditional understanding that steroid receptors dimerize in the absence of DNA, it is fully consistent with our previous work demonstrating that GR and two PR isoforms either do not dimerize or dimerize only weakly. Moreover, both AR proteins exhibit substantial cooperativity between binding sites, again as seen for GR and PR. In sharp contrast, the more distantly related ER-α dimerizes so strongly that energetics can only be measured indirectly, yet cooperativity is negligible. Thus, homologous receptors partition their promoter-binding energetics quite differently. Moreover, since receptors most closely related by phylogeny partition their energetics similarly, such partitioning appears to be evolutionarily conserved. We speculate that such differences in energetics, coupled with different promoter architectures, serve as the basis for generating receptor-specific promoter occupancy and thus function.


Assuntos
Regiões Promotoras Genéticas , Receptores Androgênicos/metabolismo , Sítios de Ligação , Humanos , Cinética , Masculino , Ligação Proteica/efeitos dos fármacos , Multimerização Proteica , Receptores Androgênicos/química , Receptores Androgênicos/genética , Receptores de Esteroides/química , Receptores de Esteroides/metabolismo , Cloreto de Sódio/farmacologia , Termodinâmica
14.
Biophys Chem ; 172: 8-17, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23333595

RESUMO

Steroid receptors assemble at DNA response elements as dimers, resulting in coactivator recruitment and transcriptional activation. Our work has focused on dissecting the energetics associated with these events and quantitatively correlating the results with function. A recent finding is that different receptors dimerize with large differences in energetics. For example, estrogen receptor-α (ER-α) dimerizes with a ΔG=-12.0 kcal/mol under conditions in which the glucocorticoid receptor (GR) dimerizes with a ΔG≤-5.1 kcal/mol. To determine the molecular forces responsible for such differences, we created a GR/ER chimera, replacing the hormone-binding domain (HBD) of GR with that of ER-α. Cellular and biophysical analyses demonstrate that the chimera is functionally active. However, GR/ER dimerization energetics are intermediate between the parent proteins and coupled to a strong ionic linkage. Since the ER-α HBD is the primary contributor to dimerization, we suggest that GR residues constrain an ion-regulated HBD assembly reaction.


Assuntos
Receptores de Estrogênio/metabolismo , Receptores de Glucocorticoides/metabolismo , Cloreto de Sódio/farmacologia , Sítios de Ligação , Pegada de DNA , Humanos , Luciferases/metabolismo , Multimerização Proteica , Receptores de Estrogênio/química , Receptores de Estrogênio/genética , Receptores de Glucocorticoides/química , Receptores de Glucocorticoides/genética , Elementos de Resposta/genética , Ativação Transcricional
15.
J Mol Biol ; 422(1): 18-32, 2012 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-22698871

RESUMO

The glucocorticoid receptor (GR) is a member of the steroid receptor family of ligand-activated transcription factors. A long-standing question has focused on how GR and other receptors precisely control gene expression. One difficulty in addressing this is that GR function is influenced by multiple factors including ligand and coactivator levels, chromatin state, and allosteric coupling. Moreover, the receptor recognizes an array of DNA sequences that generate a range of transcriptional activities. Such complexity suggests that any single parameter-DNA binding affinity, for example-is unlikely to be a dominant contributor to function. Indeed, a number of studies have suggested that for GR and other receptors, binding affinity toward different DNA sequences is poorly correlated with transcriptional activity. As a step toward determining the factors most predictive of GR function, we rigorously examined the relationship between in vitro GR-DNA binding energetics and in vivo transcriptional activity. We first demonstrate that previous approaches for assessing affinity-function relationships are problematic due to issues of data transformation and linearization. Thus, the conclusion that binding energetics and transcriptional activity are poorly correlated is premature. Using more appropriate analyses, we find that energetics and activity are in fact highly correlated. Furthermore, this correlation can be quantitatively accounted for using simple binding models. Finally, we show that the strong relationship between energetics and transcriptional activity is recapitulated in multiple promoter contexts, cell lines, and chromatin environments. Thus, despite the complexity of GR function, DNA binding energetics are the primary determinant of sequence-specific transcriptional activity.


Assuntos
DNA/química , Receptores de Glucocorticoides/química , Transcrição Gênica , Sequência de Bases , Sítios de Ligação , Células Cultivadas , DNA/metabolismo , Humanos , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Receptores de Glucocorticoides/metabolismo , Termodinâmica , Ativação Transcricional , Transfecção
16.
Biochemistry ; 51(22): 4463-72, 2012 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-22587663

RESUMO

The glucocorticoid receptor (GR) is a member of the steroid receptor family of ligand-activated transcription factors. A number of studies have shown that steroid receptors regulate distinct but overlapping sets of genes; however, the molecular basis for such specificity remains unclear. Previous work from our laboratory has demonstrated that under identical solution conditions, three other steroid receptors [the progesterone receptor A isoform (PR-A), the progesterone receptor B isoform (PR-B), and estrogen receptor α (ER-α)] differentially partition their self-association and promoter binding energetics. For example, PR-A and PR-B generate similar dimerization free energies but differ significantly in their extents of intersite cooperativity. Conversely, ER-α maintains an intersite cooperativity most comparable to that of PR-A yet dimerizes with an affinity orders of magnitude greater than that of either of the PR isoforms. We have speculated that these differences serve to generate receptor-specific promoter occupancies, and thus receptor-specific gene regulation. Noting that GR regulates a unique subset of genes relative to the other receptors, we hypothesized that the receptor should maintain a unique set of interaction energetics. We rigorously determined the self-association and promoter binding energetics of full-length, human GR under conditions identical to those used in our earlier studies. We find that unlike all other receptors, GR shows no evidence of reversible self-association. Moreover, GR assembles with strong intersite cooperativity comparable to that seen only for PR-B. Finally, simulations show that such partitioning of interaction energetics allows for receptor-specific promoter occupancies, even under conditions where multiple receptors are competing for binding at identical sites.


Assuntos
Regulação da Expressão Gênica , Regiões Promotoras Genéticas , Receptores de Glucocorticoides/metabolismo , Sítios de Ligação , Humanos , Receptores de Glucocorticoides/química , Receptores de Glucocorticoides/isolamento & purificação , Elementos de Resposta , Termodinâmica
17.
Mol Cell Endocrinol ; 355(1): 15-24, 2012 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-22330642

RESUMO

Progesterone receptors (PRs) mediate response to progestins in the normal breast and breast cancer. To determine if liganded PR regulate microRNAs (miRNAs) as a component of their action, we profiled mature miRNA levels following progestin treatment. Indeed, 28 miRNAs are significantly altered by 6h of progestin treatment. Many progestin-responsive genes are putative targets of progestin-regulated miRNAs; for example, progestin treatment decreases miR-29, thereby relieving repression of one of its direct targets, the gene encoding ATPase, Na(+)/K(+) transporting, beta 1 polypeptide (ATP1B1). Thus, liganded PR regulates ATP1B1 through sites in the promoter and the 3'UTR, to achieve maximal tight hormonal regulation of ATP1B1 protein via both transcriptional and translational control. We find that ATP1B1 serves to limit migration and invasion in breast cancer cells. Lastly, we demonstrate that PR itself is regulated by a progestin-upregulated miRNA, miR-513a-5p, providing a novel mechanism for tight control of PR protein expression.


Assuntos
Neoplasias da Mama/metabolismo , MicroRNAs/genética , Progestinas/farmacologia , Receptores de Progesterona/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Regiões 3' não Traduzidas , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Movimento Celular , Feminino , Genes Reporter , Humanos , Luciferases , MicroRNAs/metabolismo , Análise em Microsséries , Progestinas/metabolismo , Regiões Promotoras Genéticas , Biossíntese de Proteínas/efeitos dos fármacos , ATPase Trocadora de Sódio-Potássio/genética , Transcrição Gênica/efeitos dos fármacos , Transfecção
18.
Methods Mol Biol ; 796: 187-204, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22052491

RESUMO

A long-standing goal of biomedical research has been to determine the quantitative mechanisms responsible for gene regulation and transcriptional activation. These events occur through numerous protein-protein and protein-DNA interactions, many of which are allosterically coupled. For systems where highly purified protein is available, analytical ultracentrifugation provides a means to study these linked reactions, allosteric or otherwise. Sedimentation velocity is an ultracentrifugation technique that provides rigorous insight into protein self-association, homogeneity, and gross structure. Because self-association is often in dynamic equilibrium with other reactions such as DNA binding, an explicit and independent analysis of each interaction is critical to revealing mechanism. This chapter details a protocol for using sedimentation velocity to dissect the linkage between transcription factor self-association and site-specific DNA binding.


Assuntos
DNA/metabolismo , Proteínas/metabolismo , Fatores de Transcrição/metabolismo , Ultracentrifugação/métodos , Ligação Proteica , Proteínas/química , Receptores de Esteroides/química , Receptores de Esteroides/metabolismo , Fatores de Transcrição/química
19.
Biochemistry ; 51(3): 739-49, 2012 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-22201220

RESUMO

Steroid receptors define a family of ligand-activated transcription factors. Recent work has demonstrated that the receptors regulate distinct but overlapping gene networks, yet the mechanisms by which they do so remain unclear. We previously determined the microscopic binding energetics for progesterone receptor (PR) isoform assembly at promoters containing multiple response elements. We found that the two isoforms (PR-A and PR-B) share nearly identical dimerization and intrinsic DNA binding free energies but maintain large differences in cooperative free energy. Moreover, cooperativity can be modulated by monovalent ion binding and promoter layout, suggesting that differences in cooperativity might control isoform-specific promoter occupancy and thus receptor function. To determine whether cooperative binding energetics are common to other members of the steroid receptor family, we dissected the thermodynamics of estrogen receptor-α (ER-α):promoter interactions. We find that the ER-α intrinsic DNA binding free energy is identical to that of the PR isoforms. This was expected, noting that receptor DNA binding domains are highly conserved. Unexpectedly, ER-α generates negligible cooperativity-orders of magnitude less than predicted based on our studies of the PR isoforms. However, analysis of the cooperativity term suggests that it reflects a balance between highly favorable cooperative stabilization and unfavorable promoter bending. Moreover, ER-α cooperative free energy is compensated for by a large increase in dimerization free energy. Collectively, the results demonstrate that steroid receptors differentially partition not only cooperative energetics but also dimerization energetics. We speculate that this ability serves as a framework for regulating receptor-specific promoter occupancy and thus receptor-specific gene regulation.


Assuntos
Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Regiões Promotoras Genéticas/genética , Receptores de Progesterona/genética , Receptores de Progesterona/metabolismo , Termodinâmica , Sequência de Bases , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Dimerização , Metabolismo Energético/genética , Receptor alfa de Estrogênio/química , Regulação da Expressão Gênica , Humanos , Dados de Sequência Molecular , Ligação Proteica/genética , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Receptores de Progesterona/química
20.
Biophys Chem ; 159(1): 24-32, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21696881

RESUMO

Since 1987, the Gibbs Conference on Biothermodynamics has maintained a focus on understanding the quantitative aspects of gene regulatory systems. These studies coupled rigorous techniques with exact theory to dissect the linked reactions associated with bacterial and lower eukaryotic gene regulation. However, only in the last ten years has it become possible to apply this approach to clinically relevant, human gene regulatory systems. Here we summarize our work on the thermodynamics of human steroid receptors and their interactions with multi-site promoter sequences, highlighting results not available from more traditional biochemical and structural approaches. Noting that the Gibbs Conference has also served as a vehicle to promote the broader use of thermodynamics in understanding biology, we then discuss collaborative work on the hydrodynamics of a cytokine implicated in tumor suppression, prostate derived factor (PDF).


Assuntos
Citocinas/metabolismo , Regiões Promotoras Genéticas , Receptores de Esteroides/metabolismo , Animais , Citocinas/química , Regulação da Expressão Gênica , Humanos , Hidrodinâmica , Multimerização Proteica , Receptores de Esteroides/química , Termodinâmica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA