Response to the inhibitors of mevalonate pathway in yeast

In this experiment we performed the transcriptional profiling of the wild type yeast Saccharomyces cerevisiae upon treatment with lovastatin or zaragozic acid. These drugs are known to exert a repressing effect on the sterol branch of the isoprenoid pathway, but their action differs at the level of FPP biosynthesis. While lovastatin decreases FPP availability because it is an inhibitor of HMGR, zaragozic acid increases this level because it inhibits squalene synthase. In this work, we were interested especially in genes, whose expression would be oppositely regulated in the presence of lovastatin or zaragozic acid, since these genes could be affected by variation in FPP level and thus related somehow to the isoprenoid pathway. We measured changes in the gene expresion after exposure of cells to two inhibitors of the mevalonate pathway, Lovastatin and Zaragozic acid. Changes caused by these drugs were followed in time after 10, 30 and 60 minutes. We carried out the experiment, in the presence of 25 µg/mL lovastatin and 10 µg/mL of zaragozic acid, since these concentrations did not inhibit significantly the growth rate of the cells. These low doses permitted to reduce the risk of observing secondary effects due to growth inhibition and cell death. For each point of the experiment, total RNAs from two independent yeast cultures were extracted. For labeling we employed dye swapping (dCTP-Cy3 and dCTP-Cy5) and hybridized cDNA on two independent microarrays. Thus, every gene was represented by four intensities from two independent DNA arrays.