scholarly journals Characterization of the Biosynthetic Genes for 10,11-Dehydrocurvularin, a Heat Shock Response-Modulating Anticancer Fungal Polyketide from Aspergillus terreus

2013 ◽  
Vol 79 (6) ◽  
pp. 2038-2047 ◽  
Author(s):  
Yuquan Xu ◽  
Patricia Espinosa-Artiles ◽  
Vivien Schubert ◽  
Ya-ming Xu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Aspergillus Terreus ◽  
Polyketide Synthase ◽  
Polyketide Synthases ◽  
Content Type ◽  
Shock Response ◽  
Starter Unit ◽  
Acid Lactone ◽  
Resorcylic Acid Lactones

ABSTRACT10,11-Dehydrocurvularin is a prevalent fungal phytotoxin with heat shock response and immune-modulatory activities. It features a dihydroxyphenylacetic acid lactone polyketide framework with structural similarities to resorcylic acid lactones like radicicol or zearalenone. A genomic locus was identified from the dehydrocurvularin producer strainAspergillus terreusAH-02-30-F7 to reveal genes encoding a pair of iterative polyketide synthases (A. terreusCURS1 [AtCURS1] and AtCURS2) that are predicted to collaborate in the biosynthesis of 10,11-dehydrocurvularin. Additional genes in this locus encode putative proteins that may be involved in the export of the compound from the cell and in the transcriptional regulation of the cluster. 10,11-Dehydrocurvularin biosynthesis was reconstituted inSaccharomyces cerevisiaeby heterologous expression of the polyketide synthases. Bioinformatic analysis of the highly reducing polyketide synthase AtCURS1 and the nonreducing polyketide synthase AtCURS2 highlights crucial biosynthetic programming differences compared to similar synthases involved in resorcylic acid lactone biosynthesis. These differences lead to the synthesis of a predicted tetraketide starter unit that forms part of the 12-membered lactone ring of dehydrocurvularin, as opposed to the penta- or hexaketide starters in the 14-membered rings of resorcylic acid lactones. TetraketideN-acetylcysteamine thioester analogues of the starter unit were shown to support the biosynthesis of dehydrocurvularin and its analogues, with yeast expressing AtCURS2 alone. Differential programming of the product template domain of the nonreducing polyketide synthase AtCURS2 results in an aldol condensation with a different regiospecificity than that of resorcylic acid lactones, yielding the dihydroxyphenylacetic acid scaffold characterized by an S-type cyclization pattern atypical for fungal polyketides.

scholarly journals Membrane Fluidity and Temperature Sensing Are Coupled via Circuitry Comprised of Ole1, Rsp5, and Hsf1 in Candida albicans

2014 ◽  
Vol 13 (8) ◽  
pp. 1077-1084 ◽  
Author(s):  
Michelle D. Leach ◽  
Leah E. Cowen
Keyword(s):  
Candida Albicans ◽  
Fatty Acid ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Fatty Acid Synthase ◽  
Temperature Sensing ◽  
Yeast Cells ◽  
Thermal Transitions ◽  
Content Type ◽  
Shock Response

ABSTRACTTemperature is a ubiquitous environmental variable which can profoundly influence the physiology of living cells as it changes over time and space. When yeast cells are exposed to a sublethal heat shock, normal metabolic functions become repressed and the heat shock transcription factor Hsf1 is activated, inducing heat shock proteins (HSPs).Candida albicans, the most prevalent human fungal pathogen, is an opportunistic pathogen that has evolved as a relatively harmless commensal of healthy individuals. Even thoughC. albicansoccupies thermally buffered niches, it has retained the classic heat shock response, activating Hsf1 during slow thermal transitions such as the increases in temperature suffered by febrile patients. However, the mechanism of temperature sensing in fungal pathogens remains enigmatic. A few studies withSaccharomyces cerevisiaesuggest that thermal stress is transduced into a cellular signal at the level of the membrane. In this study, we manipulated the fluidity ofC. albicansmembrane to dissect mechanisms of temperature sensing. We determined that in response to elevated temperature, levels ofOLE1, encoding a fatty acid desaturase, decrease. Subsequently, loss ofOLE1triggers expression ofFAS2, encoding a fatty acid synthase. Furthermore, depletion ofOLE1prevents full activation of Hsf1, thereby reducingHSPexpression in response to heat shock. This reduction in Hsf1 activation is attributable to the E3 ubiquitin ligase Rsp5, which regulatesOLE1expression. To our knowledge, this is the first study to define a molecular link between fatty acid synthesis and the heat shock response in the fungal kingdom.

Dimethyl-sulfoxide is a Suitable Solvent for Fluorescent Microscopy Detection of Medium and Strong Heat Shock Inductors Using Transgenic Zebrafish

2018 ◽  
Vol 69 (2) ◽  
pp. 337-340
Author(s):  
Vlad Preluca ◽  
Bogdan Horatiu Serb ◽  
Sanda Marchian ◽  
Diter Atasie ◽  
Mihaela Cernusca Mitariu ◽  
...  
Keyword(s):  
Heat Shock ◽  
Dimethyl Sulfoxide ◽  
Heat Shock Response ◽  
Protein Misfolding ◽  
Fluorescent Microscopy ◽  
Screening Tests ◽  
Transgenic Zebrafish ◽  
Fluorescent Intensity ◽  
Shock Response ◽  
Heat Shock Induction

Heat shock inductors have potential as treatment for degenerative and protein misfolding diseases. Dimethyl-sulfoxide is widely used as a solvent in pharmacological screening tests and has been shown to have heat shock induction effects. Transgenic Tg (hsp70l:EGFP-HRAS_G12V)io3(AB) zebrafish larvae were exposed for 24 hours to dimethyl-sulfoxide in concentratios of 0.1-2%, and to moderate heat shock inductors pentoxifylline and tacrolimus. Positive controls were exposed to 35, 38 and 40�C for 20 min, and incubated for 24 h at 28�C. Heat shock response was measured by fluorescence microscopy and signal intensity quantification in FIJI. Dimethyl-sulfoxide caused a dose-dependant increase in fluorescent intensity, but significantly lower compared with exposure to 38 and 40�C. Pentoxifylline and tacrolimus induced a significantly higher increase in fluorescence compared with 0.5% dimethyl-sulfoxide. Thus, although dimethyl-sulfoxide has independent heat shock induction effects, concentrations of up to 0.5% are suitable for heat shock response screening tests.

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