Elucidating the transcriptional regulatory network controlling the TPO1 response to benzoic acid in yeast

Abstract

Multidrug resistance (MDR) is the simultaneous acquisition of resistance to wide range of structurally and functionally unrelated cytotoxic chemical compounds that has severe consequences in cancer therapy, agriculture and food industry.

Saccharomyces cerevisiae is a well-established model organism used to study the mechanisms of MDR. In yeast and other related organisms, MDR is often caused by drug-efflux pumps that are able to export a wide range of unrelated chemicals. Tpo1, a drug:H⁺ antiporter of the major facilitator superfamily, is one such drug-efflux pump. In the current work, our aim was to characterize the transcriptional regulatory network controlling TPO1 response to benzoic acid.

We have employed two complementary approaches to achieve this aim. First, we have used RT-PCR to measure the transcript levels of Tpo1 and five of its known and putative regulators (GCN4, STP1, STP2, PDR1, PDR3) over a time course in wild type and respective deletion mutants. We have subsequently used this information to construct a logical model of TPO1 regulation.

In the second part, we have developed a computational approach that combines data from multiple public sources to predict novel regulators for TPO1 and we have verified some of the prediction experimentally using, ß-galactosidase assays.

Our results indicate that in benzoic acid stress, Pdrl/Pdr3 seem to play no role in regulating TPO1 and instead, a complex interplay between Gcn4, and Stp1 is responsible for the up regulation of TP01. Screening for new regulators revealed Hal9 and Ash1 that seem to be repressing TPOl expression in control conditions or in benzoic acid stress, respectively. Furthermore, multiple transcription factors previously implicated in pseudohyphal growth also have a small effect on TPOl expression.