Genome-wide expression profiling of the cryptolepine-induced toxicity in Saccharomyces cerevisiae

We have used the budding yeast Saccharomyces cerevisiae to identify genes that may confer sensitivity in vivo to the antimalarial and cytotoxic agent cryptolepine. To this end, five S. cerevisiae strains, which differ in the condition of genes related to cell membrane integrity and to DNA damage repair, were exposed to several concentrations of cryptolepine. Results showed a relatively mild toxicity of cryptolepine for wild type strains, which increased by either increasing cell permeability (∆erg6 or ISE2 strains) or disrupting DNA damage repair (∆rad52 strains). These results are compatible with the ability of cryptolepine to intercalate into DNA and therefore, promote DNA lesions. The effects of low concentrations of cryptolepine (IC20 and IC40) were then analysed by comparison between gene expression profiles of treated and untreated ∆erg6 yeast cells. Significant changes in expression levels were observed for 349 genes (117 up-regulated and 232 down-regulated). General stress-related genes constituted the only recognizable functional cluster whose expression was increased upon cryptolepine treatment, making up about 20% of up-regulated genes. In contrast, analysis of characteristics of down-regulated genes revealed a specific effect of cryptolepine on genes related to iron-transport or acid phosphatases, as well as a significant proportion of cell wall components. In particular, the effects of cryptolepine treatment on transcription of iron transport-related genes were compatible with of a loss-of-function of the iron sensor Aft1p, indicating a possible disruption of the iron metabolism is S. cerevisiae. As iron metabolism is one of the putative antimalarial effects of cryptolepine, this finding exemplarises the utility of S. cerevisiae in drug-developing schemes. These results are analyzed in the context of the known cryptolepine activities as antimalarial and cytotoxic drug. Eight sets of microarray data were produced, corresponding to treatments with two different cryptolepine concentration (7.5 and 17µM, equivalent to IC20 and IC40), each performed by duplicated, and each RNA preparation labeled and hybridized twice, swapping dyes between treated and untreated samples. Data is presented as treated to untreated fluorescence ratios.