Role of Saccharomyces cerevisiae PMT1 in endoplasmic reticulum stress response

Abstract:

[Objective] Endoplasmic reticulum stress (ERS) activates a cytoprotective signaling cascade, termed as unfolded protein response (UPR). Recent advances have unveiled that UPR pathway was mainly mediated by Hac1p (transcription factor) and Ire1p (ERS sensor) in yeast. Our previous results suggest that protein-O-mannosyltransferase 1 (PMT1) deficiency enhanced the basal activity of UPR, and extended the replicative lifespan of yeast. In this study, we attempted to further study the effect of PMT1-deficiency on ERS response induced by tunicamycin in Saccharomyces cerevisiae. [Methods] Colony-forming ability of PMT1/IRE1 and PMT1/HAC1 double-gene deletion strains (pmt1Dire1D and pmt1Dhac1D) was analyzed under ERS condition. Cell proliferation assay was performed using the Microbial Viability Assay Kit. Expression levels of canonical UPR target genes were determined by quantitative RT-PCR (qRT-PCR). [Results] PMT1 deficiency strain (pmt1D) grew slowly under ERS condition, while both the IRE1- and HAC1- deletion strain (ire1D and hac1D) were not viable under this condition, compared to the control strain. The double-gene deletion strain (pmt1Dhac1D) exhibited enhanced growth ability under ERS condition, compared with the hac1D strain. Nonetheless, expression levels of UPR target genes showed no significant difference between pmt1Dhac1D and hac1D strains. [Conclusion] PMT1 deficiency enables hac1D strain to resist tunicamycin induced ERS, independent of the UPR activity.

Key words:Saccharomyces cerevisiae, Endoplasmic reticulum stress, Unfolded protein response, Tunicamycin