Sequence-specific trapping of topoisomerase I by DNA binding polyamide-camptothecin conjugates

Hairpin pyrrole−imidazole polyamides are synthetic ligands that bind in the minor groove of DNA with affinities and specificities comparable to those of DNA binding proteins. Three polyamide−camptothecin conjugates 1−3 with linkers varying in length between 7, 13, and 18 atoms were synthesized to trap the enzyme Topoisomerase I and induce cleavage at predetermined DNA sites. One of these, polyamide−camptothecin conjugate 3 at nanomolar concentration (50 nM) in the presence of Topo I (37 °C), induces DNA cleavage between three and four base pairs from the polyamide binding site in high yield (77%)

Sequence-specific trapping of topoisomerase I by DNA binding polyamide-camptothecin conjugates

Hairpin pyrrole−imidazole polyamides are synthetic ligands that bind in the minor groove of DNA with affinities and specificities comparable to those of DNA binding proteins. Three polyamide−camptothecin conjugates 1−3 with linkers varying in length between 7, 13, and 18 atoms were synthesized to trap the enzyme Topoisomerase I and induce cleavage at predetermined DNA sites. One of these, polyamide−camptothecin conjugate 3 at nanomolar concentration (50 nM) in the presence of Topo I (37 °C), induces DNA cleavage between three and four base pairs from the polyamide binding site in high yield (77%)

Identification and molecular genetic analysis of the cichorine gene cluster in Aspergillus nidulans

We recently demonstrated that the phytotoxin cichorine is produced by Aspergillus nidulans. Through a set of targeted deletions, we have found a cluster of seven genes that are required for its biosynthesis. Two of the deletions yielded molecules that give information about the biosynthesis of this metabolite

Hydroxybenzamide/pyrrole pair distinguishes T·A from A·T base pairs in the minor groove of DNA

A new aromatic pair, 2-hydroxy-6-methoxybenzamide/1-methylpyrrole at the terminal position of hairpin polyamides has been designed for distinguishing T·A from A·T base pairs and both from G·C/C·G in the minor groove of DNA. Four eight-ring hairpin polyamides with benzamide (Bz), 2-hydroxybenzamide (Hb-1), 2-hydroxy-6-methylbenzamide (Hb-2), and 2-hydroxy-6-methoxybenzamide (Hb-3) at the N-terminal position were synthesized. The equilibrium association constants (K_a) were determined at four DNA sites which differ at a single common position, 5‘-TNTACA-3‘ (N = T, A, G, C). Quantitative DNase I footprint titration experiments reveal that (Hb-3)PyPyPy-(R)^H2^Nγ-ImPyPyPy-β-Dp (4) bound the sequences 5‘-TTTACA-3‘ and 5‘-TATACA-3‘ with high affinity; K_a = 2.6 × 10^(10) M^(-1) and K_a = 8.4 × 10^9 M^(-1), respectively, a 3-fold specificity for T vs A was found. Importantly, the sequences 5‘-TGTACA-3‘ and 5‘-TCTACA-3‘ are bound with 50 and 200 times lower affinity, revealing an overall specificity of Hb-3/Py of T > A ≫ G > C. These results expand the repertoire of sequences targetable by hairpin polyamides

Hydroxybenzamide/pyrrole pair distinguishes T·A from A·T base pairs in the minor groove of DNA

A new aromatic pair, 2-hydroxy-6-methoxybenzamide/1-methylpyrrole at the terminal position of hairpin polyamides has been designed for distinguishing T·A from A·T base pairs and both from G·C/C·G in the minor groove of DNA. Four eight-ring hairpin polyamides with benzamide (Bz), 2-hydroxybenzamide (Hb-1), 2-hydroxy-6-methylbenzamide (Hb-2), and 2-hydroxy-6-methoxybenzamide (Hb-3) at the N-terminal position were synthesized. The equilibrium association constants (K_a) were determined at four DNA sites which differ at a single common position, 5‘-TNTACA-3‘ (N = T, A, G, C). Quantitative DNase I footprint titration experiments reveal that (Hb-3)PyPyPy-(R)^H2^Nγ-ImPyPyPy-β-Dp (4) bound the sequences 5‘-TTTACA-3‘ and 5‘-TATACA-3‘ with high affinity; K_a = 2.6 × 10^(10) M^(-1) and K_a = 8.4 × 10^9 M^(-1), respectively, a 3-fold specificity for T vs A was found. Importantly, the sequences 5‘-TGTACA-3‘ and 5‘-TCTACA-3‘ are bound with 50 and 200 times lower affinity, revealing an overall specificity of Hb-3/Py of T > A ≫ G > C. These results expand the repertoire of sequences targetable by hairpin polyamides

State of the art: noninvasive imaging and management of neurovascular trauma

Neurotrauma represents a significant public health problem, accounting for a significant proportion of the morbidity and mortality associated with all traumatic injuries. Both blunt and penetrating injuries to cervicocerebral vessels are significant and are likely more common than previously recognized. Imaging of such injuries is an important component in the evaluation of individuals presenting with such potential injuries, made all the more important since many of the vascular injuries are clinically silent. Management of injuries, particularly those caused by blunt trauma, is constantly evolving. This article addresses the current state of imaging and treatment of such injuries

Mechanisms and regulation of surface interactions and biofilm formation in Agrobacterium

For many pathogenic bacteria surface attachment is a required first step during host interactions. Attachment can proceed to invasion of host tissue or cells or to establishment of a multicellular bacterial community known as a biofilm. The transition from a unicellular, often motile, state to a sessile, multicellular, biofilm-associated state is one of the most important developmental decisions for bacteria. Agrobacterium tumefaciens genetically transforms plant cells by transfer and integration of a segment of plasmid-encoded transferred DNA (T-DNA) into the host genome, and has also been a valuable tool for plant geneticists. A. tumefaciens attaches to and forms a complex biofilm on a variety of biotic and abiotic substrates in vitro. Although rarely studied in situ, it is hypothesized that the biofilm state plays an important functional role in the ecology of this organism. Surface attachment, motility, and cell division are coordinated through a complex regulatory network that imparts an unexpected asymmetry to the A. tumefaciens life cycle. In this review we describe the mechanisms by which A. tumefaciens associates with surfaces, and regulation of this process. We focus on the transition between flagellar-based motility and surface attachment, and on the composition, production, and secretion of multiple extracellular components that contribute to the biofilm matrix. Biofilm formation by A. tumefaciens is linked with virulence both mechanistically and through shared regulatory molecules. We detail our current understanding of these and other regulatory schemes, as well as the internal and external (environmental) cues mediating development of the biofilm state, including the second messenger cyclic-di-GMP, nutrient levels, and the role of the plant host in influencing attachment and biofilm formation. A. tumefaciens is an important model system contributing to our understanding of developmental transitions, bacterial cell biology, and biofilm formation

Conversion of Polyethylenes into Fungal Secondary Metabolites

Waste plastics represent major environmental and economic burdens due to their ubiquity, slow breakdown rates, and inadequacy of current recycling routes. Polyethylenes are particularly problematic, because they lack robust recycling approaches despite being the most abundant plastics in use today. We report a novel chemical and biological approach for the rapid conversion of polyethylenes into structurally complex and pharmacologically active compounds. We present conditions for aerobic, catalytic digestion of polyethylenes collected from post‐consumer and oceanic waste streams, creating carboxylic diacids that can then be used as a carbon source by the fungus Aspergillus nidulans. As a proof of principle, we have engineered strains of A. nidulans to synthesize the fungal secondary metabolites asperbenzaldehyde, citreoviridin, and mutilin when grown on these digestion products. This hybrid approach considerably expands the range of products to which polyethylenes can be upcycled

Proteomic and Metabolomic Characteristics of Extremophilic Fungi Under Simulated Mars Conditions

Filamentous fungi have been associated with extreme habitats, including nuclear power plant accident sites and the International Space Station (ISS). Due to their immense adaptation and phenotypic plasticity capacities, fungi may thrive in what seems like uninhabitable niches. This study is the first report of fungal survival after exposure of monolayers of conidia to simulated Mars conditions (SMC). Conidia of several Chernobyl nuclear accident-associated and ISS-isolated strains were tested for UV-C and SMC sensitivity, which resulted in strain-dependent survival. Strains surviving exposure to SMC for 30 min, ISSFT-021-30 and IMV 00236-30, were further characterized for proteomic, and metabolomic changes. Differential expression of proteins involved in ribosome biogenesis, translation, and carbohydrate metabolic processes was observed. No significant metabolome alterations were revealed. Lastly, ISSFT-021-30 conidia re-exposed to UV-C exhibited enhanced UV-C resistance when compared to the conidia of unexposed ISSFT-021

An Efficient System for Heterologous Expression of Secondary Metabolite Genes in Aspergillus nidulans

This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/ja401945a.Fungal secondary metabolites (SMs) are an important source of medically valuable compounds. Genome projects have revealed that fungi have many SM biosynthetic gene clusters that are not normally expressed. To access these potentially valuable, cryptic clusters, we have developed a heterologous expression system in Aspergillus nidulans. We have developed an efficient system for amplifying genes from a target fungus, placing them under control of a regulatable promoter, transferring them into A. nidulans and expressing them. We have validated this system by expressing non-reducing polyketide synthases of Aspergillus terreus and additional genes required for compound production and release. We have obtained compound production and release from six of these NR-PKSs and have identified the products. To demonstrate that the procedure allows transfer and expression of entire secondary metabolite biosynthetic pathways, we have expressed all the genes of a silent A. terreus cluster and demonstrate that it produces asperfuranone. Further, by expressing the genes of this pathway in various combinations, we have clarified the asperfuranone biosynthetic pathway. We have also developed procedures for deleting entire A. nidulans SM clusters. This allows us to remove clusters that might interfere with analyses of heterologously expressed genes and to eliminate unwanted toxins