7 results on '"Eachus, Rachel A."'
Search Results
2. Regulation by let-7 and lin-4 miRNAs results in target mRNA degradation
- Author
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Bagga, Shveta, Bracht, John, Hunter, Shaun, Massirer, Katlin, Holtz, Janette, Eachus, Rachel, and Pasquinelli, Amy E.
- Subjects
Messenger RNA -- Research ,Caenorhabditis elegans -- Genetic aspects ,Nucleotide sequence -- Research ,Genetic research ,Biological sciences - Abstract
Regulation by the let-7 microRNAs (miRNA) in Caenorhabditis elegans leads to degradation of its lin-41 target mRNA, despite the fact that its 3'unrelated regions (UTR) regulatory sequences can only partially base pair with the miRNA. The results reveal that mRNAs containing partial miRNA complementary sites can be targeted for degradation in vivo, raising the possibility that regulation at the level of mRNA stability may be common than previously appreciated for the miRNA pathway.
- Published
- 2005
3. Engineering Escherichia coli for production of functionalized terpenoids using plant P450s
- Author
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Michelle C. Y. Chang, Eachus Rachel, Dae-Kyun Ro, Jay D. Keasling, and William Trieu
- Subjects
Molecular Structure ,Chemistry ,Terpenes ,fungi ,Cell Biology ,Protein engineering ,Plants ,medicine.disease_cause ,Protein Engineering ,Small molecule ,Chemical synthesis ,Terpenoid ,Artemisinins ,Metabolic pathway ,chemistry.chemical_compound ,Biochemistry ,Biosynthesis ,Cytochrome P-450 Enzyme System ,In vivo ,medicine ,Escherichia coli ,Molecular Biology - Abstract
Terpenoids are a highly diverse class of natural products that have historically provided a rich source for discovery of pharmacologically active small molecules, such as paclitaxel (Taxol) and artemisinin. Unfortunately, these secondary metabolites are typically produced in low abundance in their host organism, and their isolation consequently suffers from low yields and high consumption of natural resources. Furthermore, chemical synthesis of terpenoids can also be difficult to scale for industrial production. For these reasons, an attractive alternative strategy is to engineer metabolic pathways for production of pharmaceuticals or their precursors in a microbial host such as Escherichia coli. A key step is developing methods to carry out cytochrome P450 (P450)-based oxidation chemistry in vivo. Toward this goal, we have assembled two heterologous pathways for the biosynthesis of plant-derived terpenoid natural products, and we present the first examples of in vivo production of functionalized terpenoids in E. coli at high titer using native plant P450s.
- Published
- 2007
4. Production of the antimalarial drug precursor artemisinic acid in engineered yeast
- Author
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Dae-Kyun Ro, Eric M. Paradise, John M. Ndungu, James Kirby, Richmond Sarpong, Mario Ouellet, Timothy S. Ham, Ho Kimberly, Karl Fisher, Michelle C. Y. Chang, Karyn L. Newman, Eachus Rachel, Yoichiro Shiba, Sydnor T. Withers, and Jay D. Keasling
- Subjects
Amorpha-4,11-diene ,Molecular Sequence Data ,Plasmodium falciparum ,Artemisia annua ,Mevalonic Acid ,Saccharomyces cerevisiae ,Sesquiterpene lactone ,Drug Costs ,Gas Chromatography-Mass Spectrometry ,chemistry.chemical_compound ,Antimalarials ,Bioreactors ,Cytochrome P-450 Enzyme System ,parasitic diseases ,medicine ,Animals ,Artemisinin ,Malaria, Falciparum ,chemistry.chemical_classification ,Multidisciplinary ,biology ,Drug discovery ,Monooxygenase ,biology.organism_classification ,medicine.disease ,Yeast ,Artemisinins ,chemistry ,Biochemistry ,Fermentation ,Genetic Engineering ,Sesquiterpenes ,Malaria ,medicine.drug - Abstract
Drug-resistant strains of the malaria parasite are widespread, and as a result mortality due to malaria has increased significantly in recent years. Artemisinin, isolated from the herb Artemisia annua (sweet wormwood), is one drug that shows a high efficacy in killing multi-resistant strains of the parasite. The drug is extremely expensive, and high demand has led to a shortage of artemisinin, available only by extraction from the plant source. Ro et al. now report the development of a yeast strain engineered to carry a cytochrome P450 monooxygenase from A. annua that can produce the drug precursor, artemisinic acid. Artemisinin can be synthesized from this precursor. If the efficiency of this process can be improved, this engineered yeast strain has the potential to alleviate the drug shortage. Through the bio-engineering of Saccharomyces cerevisiae high titres of artemisinic acid were produced using a novel cytochrome P450 monooxygenase. Optimization of this process on an industrial scale may significantly reduce the cost of artemisinin, which could then be used to combat malaria in resource-poor settings. Malaria is a global health problem that threatens 300โ500 million people and kills more than one million people annually1. Disease control is hampered by the occurrence of multi-drug-resistant strains of the malaria parasite Plasmodium falciparum2,3. Synthetic antimalarial drugs and malarial vaccines are currently being developed, but their efficacy against malaria awaits rigorous clinical testing4,5. Artemisinin, a sesquiterpene lactone endoperoxide extracted from Artemisia annua L (family Asteraceae; commonly known as sweet wormwood), is highly effective against multi-drug-resistant Plasmodium spp., but is in short supply and unaffordable to most malaria sufferers6. Although total synthesis of artemisinin is difficult and costly7, the semi-synthesis of artemisinin or any derivative from microbially sourced artemisinic acid, its immediate precursor, could be a cost-effective, environmentally friendly, high-quality and reliable source of artemisinin8,9. Here we report the engineering of Saccharomyces cerevisiae to produce high titres (up to 100 mg l-1) of artemisinic acid using an engineered mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) from A. annua that performs a three-step oxidation of amorpha-4,11-diene to artemisinic acid. The synthesized artemisinic acid is transported out and retained on the outside of the engineered yeast, meaning that a simple and inexpensive purification process can be used to obtain the desired product. Although the engineered yeast is already capable of producing artemisinic acid at a significantly higher specific productivity than A. annua, yield optimization and industrial scale-up will be required to raise artemisinic acid production to a level high enough to reduce artemisinin combination therapies to significantly below their current prices.
- Published
- 2005
5. Engineering Escherichia coli for production of functionalized terpenoids using plant P450s
- Author
-
Chang, Michelle C Y, primary, Eachus, Rachel A, additional, Trieu, William, additional, Ro, Dae-Kyun, additional, and Keasling, Jay D, additional
- Published
- 2007
- Full Text
- View/download PDF
6. Trans-splicing and polyadenylation of let-7 microRNA primary transcripts
- Author
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BRACHT, JOHN, primary, HUNTER, SHAUN, additional, EACHUS, RACHEL, additional, WEEKS, PHILLIP, additional, and PASQUINELLI, AMY E., additional
- Published
- 2004
- Full Text
- View/download PDF
7. Production of the antimalarial drug precursor artemisinic acid in engineered yeast.
- Author
-
Dae-Kyun Ro, Paradise, Eric M., Ouellet, Mario, Fisher, Karl J., Newman, Karyn L., Ndungu, John M., Ho, Kimberly A., Eachus, Rachel A., Ham, Timothy S., Kirby, James, Chang, Michelle C. Y., Withers, Sydnor T., Shiba, Yoichiro, Sarpong, Richmond, and Keasling, Jay D.
- Subjects
ANTIMALARIALS ,ANTIPARASITIC agents ,MALARIA treatment ,DRUG resistance in microorganisms ,YEAST ,PROTOZOAN diseases ,PLASMODIUM falciparum ,MONOOXYGENASES - Abstract
Malaria is a global health problem that threatens 300โ500 million people and kills more than one million people annually. Disease control is hampered by the occurrence of multi-drug-resistant strains of the malaria parasite Plasmodium falciparum. Synthetic antimalarial drugs and malarial vaccines are currently being developed, but their efficacy against malaria awaits rigorous clinical testing. Artemisinin, a sesquiterpene lactone endoperoxide extracted from Artemisia annua L (family Asteraceae; commonly known as sweet wormwood), is highly effective against multi-drug-resistant Plasmodium spp., but is in short supply and unaffordable to most malaria sufferers. Although total synthesis of artemisinin is difficult and costly, the semi-synthesis of artemisinin or any derivative from microbially sourced artemisinic acid, its immediate precursor, could be a cost-effective, environmentally friendly, high-quality and reliable source of artemisinin. Here we report the engineering of Saccharomyces cerevisiae to produce high titres (up to 100 mg l
-1 ) of artemisinic acid using an engineered mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) from A. annua that performs a three-step oxidation of amorpha-4,11-diene to artemisinic acid. The synthesized artemisinic acid is transported out and retained on the outside of the engineered yeast, meaning that a simple and inexpensive purification process can be used to obtain the desired product. Although the engineered yeast is already capable of producing artemisinic acid at a significantly higher specific productivity than A. annua, yield optimization and industrial scale-up will be required to raise artemisinic acid production to a level high enough to reduce artemisinin combination therapies to significantly below their current prices. [ABSTRACT FROM AUTHOR]- Published
- 2006
- Full Text
- View/download PDF
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