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Biomedical subjects

Anna K Mapp

Publications and source records attributed to Anna K Mapp.

17 recordsLinked to original sources
PubMed2006

Converting inactive peptides into potent transcriptional activators.

Significant efforts have been devoted to the development of artificial transcriptional activators for use as mechanistic tools, as therapeutic agents, and for biomanufacturing applications. One of the primary challenges has been the development of artificial activators that exhibit potency in cells comparable to that of endogenous activators; the vast majority function only moderately in the cellular context. Here we demonstrate that the superimposition of two distinct binding modes, a masking interaction and an interaction with the transcriptional machinery, has a profoundly positive effect on the cellular activity of artificial activators, with up to 600-fold enhancement observed. Incorporation of this feature into future generations of small molecule transcriptional activators should increase their nuclear uptake and facilitate their accessibility to their target proteins, thus significantly augmenting both their activity and utility.

Biochemistry↗
PubMed2006

[3,3]-rearrangements of phosphonium ylides.

Allylic phosphonium ylides are readily generated by the combination of an allylic alcohol, a carbene, and a chlorophosphite. Here we demonstrate that these intermediates undergo a thermal [3,3]-rearrangement to provide single isomers of homoallylic phosphonates in good to excellent yields. This new reaction manifold for phosphorus ylides is tolerant of a range of substitution patterns on the reactants and provides access to structurally complex intermediates for the synthesis of enzyme inhibitors, aminophosphonic acids, and natural products.

Alcohols↗
PubMed2005

Stereochemical promiscuity in artificial transcriptional activators.

Small molecule replacements of transcriptional activation domains are highly desirable targets due to their utility as mechanistic tools and their long-term therapeutic potential for a variety of human diseases. Here, we examine the ability of amphipathic isoxazolidines differing only in the placement of constituent side chains to function as transcriptional activation domains. The results reveal that precise positioning of functional groups within a conformationally constrained small molecule scaffold is not required for transcription function; rather, the balance of polarity and hydrophobicity within the scaffold is the more important determinant of transcription function. This suggests that a number of different organic molecule scaffolds should function as transcriptional activator domains when appropriately functionalized, a hypothesis currently under investigation.

DNA↗
PubMed2005

Thermal and catalyzed [3,3]-phosphorimidate rearrangements.

[3,3]-Sigmatropic rearrangements have been widely utilized for the synthesis of structurally complex organic molecules because of the ease with which carbon-carbon bonds are formed in a regio- and stereocontrolled manner. However, there are far fewer [3,3]-rearrangements available for the selective formation of carbon-nitrogen bonds despite the enormous potential of such reactions for the preparation of stereodefined allylic amines. We describe here the scope and mechanism of a [3,3]-rearrangement of allylic phosphorimidates that provides access to stereodefined allylic amines of diverse structure. The reactive intermediate in the reaction, an allylic phosphorimidate, is produced in situ through the combination of readily available starting materials (allylic alcohols, chlorophosphites, and organic azides), rendering the reaction an efficient three-component process. Analogous to other [3,3]-rearrangements, the stereochemistry in an allylic alcohol starting material is transferred with fidelity to the allylic amine product and, further, allylic amines are produced as single olefin isomers. In addition, a crossover experiment indicates that the rearrangement is an intramolecular process. Finally, activation of the allylic moiety either through incorporation of electron-deficient functional groups or through the use of a transition-metal catalyst significantly facilitates the reaction and consequently the preparation of a wider range of substitution patterns.

Allyl Compounds↗
PubMed2005

Unraveling the mechanism of a potent transcriptional activator.

Despite their enormous potential as novel research tools and therapeutic agents, artificial transcription factors (ATFs) that up-regulate transcription robustly in vivo remain elusive. In investigating an ATF that does function exceptionally well in vivo, we uncovered an unexpected relationship between transcription function and a binding interaction between the activation domain and an adjacent region of the DNA binding domain. Disruption of this interaction leads to complete loss of function in vivo, even though the activation domain is still able to bind to its target in the transcriptional machinery. We propose that this interaction parallels those between natural activation domains and their regulatory proteins, concealing the activation domain from solvent and the cellular milieu until it binds to its transcriptional machinery target. Inclusion of this property in the future design of ATFs should enhance their efficacy in vivo.

Amino Acid Sequence↗
PubMed2005

Succinct synthesis of beta-amino acids via chiral isoxazolines.

beta-Amino acids are important synthetic targets due to their presence in a wide variety of natural products, pharmaceutical agents, and mimics of protein structural motifs. While beta-amino acids containing geminal substitution patterns have enormous potential for application in these contexts, synthetic challenges to the stereoselective preparation of this class of compound have thus far limited more complete studies. We present here a straightforward method employing chiral isoxazolines as key intermediates to access five different beta-amino acid structural types with excellent selectivity. Of particular note is the use of this approach to prepare highly substituted cis-beta-proline analogues. The ready access to these diversely substituted compounds is expected to facilitate future studies of the structure and function of this important class of molecules.

Amino Acids↗
PubMed2005

Chemical approaches to transcriptional regulation.

Given the correlation between many human diseases and mis-regulated transcription, there is a growing need for molecules that can inhibit or mimic key interactions between transcriptional activators and their binding partners. Because transcriptional activators typically participate in many different protein-protein binding events, the identification of small molecules or peptides that specifically target individual interactions represents a significant challenge. In spite of this, several small molecules that preferentially inhibit particular complexes of transcriptional activators or mimic the function of activators have recently been reported. These molecules serve as excellent mechanistic tools for studying transcription and, further, have outstanding therapeutic potential.

Gene Expression Regulation↗
PubMed2005

Functional specificity of artificial transcriptional activators.

Misregulated transcription is linked to many human diseases, and thus artificial transcriptional activators are highly desirable as mechanistic tools and as replacements for their malfunctioning natural counterparts. We previously reported two artificial transcriptional activation domains obtained from synthetic peptide libraries screened for binding to the yeast transcription protein Med15(Gal11). Here we demonstrate that the transcriptional potency of the Med15 ligands is increased through straightforward structural alterations. These artificial activation domains upregulate transcription via specific Med15 binding interactions and do not function in mammalian cells, which lack Med15. This functional specificity stands in contrast to most natural or artificial activation domains that function across all eukaryotic cell types. The results indicate that the screening strategy holds excellent promise for identifying peptide and small molecule transcriptional activators that function by unique mechanisms with advantageous specificity properties.

Binding Sites↗
PubMed2004

A small molecule transcriptional activation domain.

Artificial transcriptional activators are excellent tools for studying the mechanistic details of transcriptional regulation. Furthermore, as the correlation between a wide range of human diseases and misregulated transcription becomes increasingly evident, such molecules may in the long run serve as the basis for transcription-based therapeutic agents. The greatest challenge in this arena has been the discovery of organic molecules that are functional mimics of transcriptional activation domains, sequences of natural proteins that participate in a variety of protein-protein interactions to control transcriptional levels. We describe the first examples of small molecules that function in this capacity, isoxazolidines containing an array of polar and hydrophobic functional groups. Despite their small size, the most potent of the structures functions nearly as well as a natural activation domain.

Activating Transcription Factors↗
PubMed2004

A phosphorimidate rearrangement for the facile and selective preparation of allylic amines.

Allylic phosphorimidates, readily prepared from the combination of an allylic alcohol, an azide, and a chlorophosphite, undergo [3,3]-rearrangement under thermal conditions to provide single isomers of allylic phosphoramidates. This new rearrangement is tolerant of a range of substitution patterns on the reactants. Treatment of the products of the rearrangement with ethanethiolate followed by acid produces a protected allylic amine. This strategy thus provides an attractive and versatile procedure for the preparation of key synthetic intermediates, allylic amines.

Allyl Compounds↗
PubMed2004

Finding their groove; bifunctional molecules arrest growth of cancer cells.

In this issue, Dickinson et al. describe an exciting advance in the search for inhibitors of transcription that function well in cells . The authors screen for small molecules that selectively damage DNA and identify a histone gene as a potential new target for cancer therapeutic development.

Antineoplastic Agents↗
PubMed2003

Targeting the transcriptional machinery with unique artificial transcriptional activators.

The link between a growing number of human diseases and misregulation of gene expression has spurred intense interest in artificial transcriptional activators that could be used to restore controlled expression of affected genes. To expand the repertoire of activation domains available for the construction of artificial transcriptional regulators, a selection strategy was used to identify two unique activation domain motifs. These activation domains bear little sequence homology to endogenous counterparts and bind to unique sites within the transcriptional machinery. A comparison with two well-characterized activation domains, VP2 and P201, demonstrated for the first time that functional potency is not solely dictated by binding affinity. Finally, the selection strategy described is readily applicable to the identification of small molecule activation domains.

Amino Acid Sequence↗
PubMed2003

Regulating transcription: a chemical perspective.

Many human diseases are characterized by altered gene expression patterns caused by malfunctioning transcriptional regulators. This has spurred new efforts in the development of artificial transcription factors that regulate the expression of specific genes either positively or negatively. Despite impressive advances in the last decade, artificial transcription factors that reconstitute all of the functions of natural regulators are not yet a reality. Such factors will be powerful chemical tools for unraveling the mechanisms by which gene expression is regulated and in the long term offer considerable therapeutic potential.

Amino Acid Sequence↗
PubMed2003

A concise approach to structurally diverse beta-amino acids.

We have demonstrated that the high yields and selectivities of 1,3-dipolar cycloadditions can be translated into facile stereoselective syntheses of a diverse array of beta-amino acids, key components of bioactive natural products, beta-lactams, and peptidomimetics. Simply by selecting different combinations of three readily available starting materials (an oxime, a chiral allylic alcohol, and a nucleophile), we used the reaction sequence to prepare four different beta-amino acid structural types with a variety of substitution patterns in good overall yield. Of particular note is the use of this approach to prepare highly substituted beta-amino acids not readily accessible by previously reported methodologies. This will pave the way for future studies of the structure and function of this important class of molecules.

Amino Acids↗
PubMed2002

Modular design of artificial transcription factors.

Eukaryotic transcription factors are composed of interchangeable modules. This has led to the design of a wide variety of modular artificial transcription factors (ATFs) that can stimulate or inhibit the expression of targeted genes. The ability to regulate the expression of any targeted gene using a 'programmable' ATF offers a powerful tool for functional genomics and bears tremendous promise in developing the field of transcription-based therapeutics.

Biotechnology↗