@article{shianna_dotson_tove_parks_2001, title={Identification of a UPC2 homolog in Saccharomyces cerevisiae and its involvement in aerobic sterol uptake}, volume={183}, ISSN={["0021-9193"]}, DOI={10.1128/JB.183.3.830-834.2001}, abstractNote={ABSTRACT Saccharomyces cerevisiae normally will not take up sterols from the environment under aerobic conditions. A specific mutant, upc2-1, of the predicted transcriptional activator UPC2 (YDR213w) has been recognized as a strain that allows a high level of aerobic sterol uptake. Another predicted transcriptional activator, the YLR228c gene product, is highly homologous to Upc2p. In fact, at the carboxy terminus 130 of the last 139 amino acids are similar between the two proteins. Since these proteins are very similar, the effect of mutations in the YLR228c open reading frame (ORF) was compared with like alterations in UPC2. First, the YLR228c ORF was insertionally inactivated and crossed with various UPC2constructs. Deletion of YLR228c and UPC2 in combination resulted in nonviability, suggesting that the two proteins have some essential overlapping function. The upc2-1point mutation responsible for aerobic sterol uptake was duplicated in the homologous carboxy region of the YLR228c ORF using site-directed mutagenesis. This mutation on a high-copy vector resulted in an increase in sterol uptake compared to an isogenic wild-type strain. The combination of both point mutations resulted in the greatest level of aerobic sterol uptake. When the YLR228c point mutation was expressed from a low-copy vector there was little if any effect on sterol uptake. Gas chromatographic analysis of the nonsaponifiable fractions of the various strains showed that the major sterol for all YLR228c andUPC2 combinations was ergosterol, the consensus yeast sterol.}, number={3}, journal={JOURNAL OF BACTERIOLOGY}, author={Shianna, KV and Dotson, WD and Tove, S and Parks, LW}, year={2001}, month={Feb}, pages={830–834} }
 @article{dotson_tove_parks_2000, title={Biochemical modifications and transcriptional alterations attendant to sterol feeding in Phytophthora parasitica}, volume={35}, ISSN={["0024-4201"]}, DOI={10.1007/s11745-000-0519-9}, abstractNote={Phytophthora species are eukaryotic sterol auxotrophs that possess the ability to grow, albeit poorly, in the complete absence of sterols. Growth of Phytophthora is often improved substantially when an exogenous source of sterol is provided. Additionally, sterols may be required for sexual and asexual sporulation in Phytophthora. Our research has been focused on identifying and characterizing the immediate physiological effects following sterol addition to cultures of P. parasitica. Through gas chromatographic analysis of extracts from P. parasitica cultures that were fed various sterols, we have obtained evidence for sterol C5 desaturase and delta7 reductase activities in this organism. Zoo blots were probed with DNA sequences encoding these enzymes, from Saccharomyces cerevisiae and Arabidopsis thaliana. Hybridization of a S. cerevisiae ERG3 probe to P. parasitica DNA was observed, implicating sequence similarity between the sterol C5 desaturase encoding genes. Differential display experiments, using RNA from P. parasitica, have demonstrated a pattern of altered gene expression between cultures grown in the presence and absence of sitosterol. Characterization of sterol-related metabolic effects and sterol functions in Phytophthora should lead to improved measures for control of this important group of plant pathogens.}, number={3}, journal={LIPIDS}, author={Dotson, WD and Tove, SR and Parks, LW}, year={2000}, month={Mar}, pages={243–247} }
 @article{crowley_parks_1999, title={Dual physiological effects of antifungal sterol biosynthetic inhibitors on enzyme targets and on transcriptional regulation}, volume={55}, DOI={10.1002/(SICI)1096-9063(199904)55:4<393::AID-PS933>3.3.CO;2-P}, abstractNote={For many antifungal agents, enzymes leading to ergosterol biosynthesis are primary targets. Inhibition of ergosterol biosynthesis in treated cells results in the formation of aberrant sterols, lacking one or more structural features of esgosterol. Furthermore, the total sterol levels are often higher than the total sterol amounts in non-treated cells. The ERG3 gene, encoding the sterol C-5 desaturase, was used as a model for the regulation by some antifungal agents of genes encoding enzymes in ergosterol biosynthesis. Treatment of yeast cells with three sterol biosynthetic inhibitors with different targets in the ergosterol biosynthetic pathway led to an increase in ERG3 mRNA levels. The increase in ERG3 mRNA by drug treatment correlated with a decrease in ergosterol content within the cells. No correlation was evident between ERG3 mRNA and total sterol levels, as treatment with at least one inhibitor, fenpropimorph, led to a slight increase in total sterol, while ERG3 mRNA levels decreased. Treatment of cells with fenpropimorph and ketoconazole resulted in a decrease in ergosterol as a percentage of total sterol, while lovastatin caused an increase in the ergosterol percentage. These results indicate that a second indirect effect of the antifungal sterol biosynthetic inhibitors is on transcriptional regulation. The physiology of the treated cell is affected not only by a decrease in ergosterol but also by an enhanced accumulation of defective sterols. © 1999 Society of Chemical Industry}, number={4}, journal={Pesticide Science}, author={Crowley, J. H. and Parks, L. W.}, year={1999}, pages={393–397} }
 @article{leak_tove_parks_1999, title={In yeast, upc2-1 confers a decrease in tolerance to LiCl and NaCl, which can be suppressed by the P-type ATPase encoded by ENA2}, volume={18}, ISSN={["1044-5498"]}, DOI={10.1089/104454999315510}, abstractNote={Wild-type yeast cells are unable to take up sterols from their growth media under aerobic conditions and are relatively resistant to monovalent cations. A yeast mutant (upc2-1) with a defect in the aerobic exclusion of sterols was found to have increased sensitivity to LiCl and NaCl. Although cation sensitivity has been reported for mutants that synthesize altered sterols, the mutant with upc2-1 continues to produce the normal sterol, ergosterol. The ENA2 gene was cloned on the basis of remediating the hypersensitivity to the monovalent cations.}, number={2}, journal={DNA AND CELL BIOLOGY}, author={Leak, FW and Tove, S and Parks, LW}, year={1999}, month={Feb}, pages={133–139} }
 @article{crowley_tove_parks_1998, title={A calcium-dependent ergosterol mutant of Saccharomyces cerevisiae}, volume={34}, ISSN={["1432-0983"]}, DOI={10.1007/s002940050371}, number={2}, journal={CURRENT GENETICS}, author={Crowley, JH and Tove, S and Parks, LW}, year={1998}, month={Aug}, pages={93–99} }
 @article{crowley_leak_shianna_tove_parks_1998, title={A mutation in a purported regulatory gene affects control of sterol uptake in Saccharomyces cerevisiae}, volume={180}, number={16}, journal={Journal of Bacteriology}, author={Crowley, J. H. and Leak, F. W. and Shianna, K. V. and Tove, S. and Parks, L. W.}, year={1998}, pages={4177–4183} }
 @article{tomeo_palermo_tove_parks_1997, title={A conditional sterol esterification defect in yeast having either a SEC1 or SEC5 mutation in the secretory pathway}, volume={13}, DOI={10.1002/(sici)1097-0061(199704)13:5<449::aid-yea99>3.0.co;2-a}, abstractNote={Two temperature‐conditional secretory mutations, sec1 and sec5, cause the accumulation of post‐Golgi vesicles when strains containing these mutations are grown at 37°C. In addition to accumulating vesicles, the mutants do not esterify free sterol on rich media at the restrictive temperature. It is the high level of inositol in the media that causes this condition in the yeast Saccharomyces cerevisiae, not a defective steryl ester synthase or lack of substrates. When strains containing the sec1 or sec5 mutation were transformed separately with a plasmid carrying SEC1 and SEC5, the esterification and secretory defects were alleviated. Double mutants containing sec6, sec14 or sec18 with either a sec1 or sec5 mutation have normal esterification levels. Strains with suppressor mutations were isolated that grew at 37°C, esterified sterols and had diminished accumulation of vesicles, when grown at the restrictive temperature on defined media with additional inositol. Electron microscopy was used to examine vesicle accumulation, the number of lipid droplets, and to further characterize the esterification defect. When grown at 37°C on defined medium, the strains with sec5 or sec1 accumulated the usual secretory vesicles, but when grown under similar conditions with elevated levels of inositol, accumulated an additional vesicular‐like body. © 1997 John Wiley & Sons, Ltd.}, number={5}, journal={Yeast}, author={Tomeo, M. E. and Palermo, L. M. and Tove, S. R. and Parks, L. W.}, year={1997}, pages={449–462} }
 @article{palermo_leak_tove_parks_1997, title={Assessment of the essentiality of ERG genes late in ergosterol biosynthesis in Saccharomyces cerevisiae}, volume={32}, ISSN={["1432-0983"]}, DOI={10.1007/s002940050252}, number={2}, journal={CURRENT GENETICS}, author={Palermo, LM and Leak, FW and Tove, S and Parks, LW}, year={1997}, month={Aug}, pages={93–99} }
 @article{smith_parks_1997, title={Requirement of heme to replace the sparking sterol function in the yeast Saccharomyces cerevisiae}, volume={1345}, ISSN={["0005-2760"]}, DOI={10.1016/S0005-2760(96)00165-8}, abstractNote={At least four distinctive sterol functions have been defined in the yeast Saccharomyces cerevisiae. One of these functions, identified as sparking, has the lowest quantitative requirement for sterol, but has the greatest structural specificity. Based on studies utilizing a yeast strain auxotrophic for both heme and sterol biosynthesis, it had been reported that a delta 5-sterol was essential for the growth of the organism. We demonstrate here that heme, and not a heme precursor, can replace the delta 5-sparking sterol requirement of heme auxotrophic strains of yeast.}, number={1}, journal={BIOCHIMICA ET BIOPHYSICA ACTA-LIPIDS AND LIPID METABOLISM}, author={Smith, SJ and Parks, LW}, year={1997}, month={Mar}, pages={71–76} }