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Eukaryotic transcription activators stimulate the expression of specific sets of target genes through recruitment of co-activators such as the RNA polymerase II-interacting Mediator complex (1,2). Aberrant function of transcription activators has been implicated in several diseases. However, therapeutic targeting efforts have been hampered by a lack of detailed molecular knowledge of the mechanisms of gene activation by disease-associated transcription activators. We previously identified an activator-targeted three-helix bundle KIX domain in the human MED15 Mediator subunit that is structurally conserved in Gal11/Med15 Mediator subunits in fungi (3,4). The Gal11/Med15 KIX domain engages pleiotropic drug resistance transcription factor (Pdr1) orthologues, which are key regulators of the multidrug resistance pathway in Saccharomyces cerevisiae and in the clinically important human pathogen Candida glabrata (5,6). The prevalence of C. glabrata is rising, partly owing to its low intrinsic susceptibility to azoles, the most widely used antifungal agent (7,8). Drug-resistant clinical isolates of C. glabrata most commonly contain point mutations in Pdr1 that render it constitutively active (9-14), suggesting that this transcriptional activation pathway represents a linchpin in C. glabrata multidrug resistance. Here we perform sequential biochemical and in vivo high-throughput screens to identify small-molecule inhibitors of the interaction of the C. glabrata Pdr1 activation domain with the C. glabrata Gal11A KIX domain. The lead compound (iKIX1) inhibits Pdr1-dependent gene activation and re-sensitizes drug-resistant C. glabrata to azole antifungals in vitro and in animal models for disseminated and urinary tract C. glabrata infection. Determining the NMR structure of the C. glabrata Gal11A KIX domain provides a detailed understanding of the molecular mechanism of Pdr1 gene activation and multidrug resistance inhibition by iKIX1. We have demonstrated the feasibility of small-molecule targeting of a transcription factor-binding site in Mediator as a novel therapeutic strategy in fungal infectious disease., On the basis of our previous findings that deletion of the KIX domain of S. cerevisiae GAL11 or C. glabrata GAL11A abrogates Pdrl-dependent transcriptional responses and xenobiotic tolerance we hypothesized [...]

Non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) produce numerous secondary metabolites with various therapeutic/antibiotic properties (1). Like fatty acid synthases (FAS), these enzymes are organized in modular assembly lines [...]

Non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) found in bacteria, fungi and plants use two different types of thioesterases for the production of highly active biological compounds (1,2). Type [...]

Multidrug resistance (MDR) is a serious complication during treatment of opportunistic fungal infections that frequently afflict immunocompromised individuals, such as transplant recipients and cancer patients undergoing cytotoxic chemotherapy. Improved knowledge [...]

Author(s): Raimund Muscheler (corresponding author) [1]; Jürg Beer [1]; Gerhard Wagner [1]; Robert C. Finkel [2] Variations in atmospheric radiocarbon ([sup.14] C) concentrations can be attributed either to changes in [...]

The solution structure of tGCN5 catalytic domain in complex with coenzyme A has been determined. The structure consists of the amino-terminal domain similar to those of other GCN5-related N-acetyltransferases, and the carboxy-terminal domain. Coenzyme A binds between the two domains, and chemical shift changes on titration with histone H3 peptides suggest a binding site at the domain boundary opposite coenzyme A.

A 20K domain of NFATc needed to bind DNA and mobilize transcription has been identified. The two proteins use significantly different strategies for DNA recognition despite the relation between the overall folds of the NFATc DNA-binding protein and NF-kB p50. Both structures exhibit differences in the length and conformation of the segments which link these strands. NFAT and Rel proteins have been found to have a high sequence similarity.

The sterol regulatory element binding protein (SREBP) family of transcription activators are critical regulators of cholesterol and fatty acid homeostasis. We previously demonstrated that human SREBPs bind the CREB-binding protein (CBP)/p300 acetyltransferase KIX domain and recruit activator-recruited co-factor (ARC)/Mediator co-activator complexes through unknown mechanisms. Here we show that SREBPs use the evolutionarily conserved ARC105 (also called MED15) subunit to activate target genes. Structural analysis of the SREBP-binding domain in ARC105 by NMR revealed a three-helix bundle with marked similarity to the CBP/p300 KIX domain. In contrast to SREBPs, the CREB and c-Myb activators do not bind the ARC105 KIX domain, although they interact with the CBP KIX domain, revealing a surprising specificity among structurally related activator-binding domains. The Caenorhabditis elegans SREBP homologue SBP-1 promotes fatty acid homeostasis by regulating the expression of lipogenic enzymes. We found that, like SBP-1, the C. elegans ARC105 homologue MDT-15 is required for fatty acid homeostasis, and show that both SBP-1 and MDT-15 control transcription of genes governing desaturation of stearic acid to oleic acid. Notably, dietary addition of oleic acid significantly rescued various defects of nematodes targeted with RNA interference against sbp-1 and mdt-15, including impaired intestinal fat storage, infertility, decreased size and slow locomotion, suggesting that regulation of oleic acid levels represents a physiologically critical function of SBP-1 and MDT-15. Taken together, our findings demonstrate that ARC105 is a key effector of SREBP-dependent gene regulation and control of lipid homeostasis in metazoans. [ABSTRACT FROM AUTHOR]

Presents an analysis of the large fluctuations in atmospheric radiocarbon concentrations of unclear origin that occurred during the Younger Dryas cold period. Use of the [sup10] beryllium record from the GISP2 ice core to model past production rates of radionucleotides; Finding that the largest part of the fluctuations can be attributed to variations in production rate; Reasons for the residual difference between the measured and modelled radiocarbon concentrations.