Induction of the Unfolded Protein Response at High Temperature in Saccharomyces cerevisiae.

Tatsuya Hata,Yuki Ishiwata-Kimata,Yukio Kimata

doi:10.3390/ijms23031669

Tatsuya Hata, Yuki Ishiwata-Kimata + Show 1 more

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https://doi.org/10.3390/ijms23031669

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Abstract

Ire1 is an endoplasmic reticulum (ER)-located endoribonuclease that is activated in response to ER stress. In yeast Saccharomyces cerevisiae cells, Ire1 promotes HAC1-mRNA splicing to remove the intron sequence from the HAC1u mRNA (“u” stands for “uninduced”). The resulting mRNA, which is named HAC1i mRNA (“i” stands for “induced”), is then translated into a transcription factor that is involved in the unfolded protein response (UPR). In this study, we designed an oligonucleotide primer that specifically hybridizes to the exon-joint site of the HAC1i cDNA. This primer allowed us to perform real-time reverse transcription-PCR to quantify HAC1i mRNA abundance with high sensitivity. Using this method, we detected a minor induction of HAC1-mRNA splicing in yeast cells cultured at their maximum growth temperature of 39 °C. Based on our analyses of IRE1-gene mutant strains, we propose that when yeast cells are cultured at or near their maximum growth temperature, protein folding in the ER is disturbed, leading to a minor UPR induction that supports cellular growth.

Highlights

The endoplasmic reticulum (ER) is the cellular compartment wherein secretory and membrane proteins are folded
This study aimed to discover scenarios that provoke ER stress and activate Ire1 in S. cerevisiae
One experimental approach frequently employed for checking cellular unfolded protein response (UPR) level is to monitor the expression of the Hac1-target genes

Summary

Introduction

The endoplasmic reticulum (ER) is the cellular compartment wherein secretory and membrane proteins are folded. In response to ER stress, eukaryotic cells alter their gene expression profile. This protective response is known as the unfolded protein response (UPR) and is at least partly controlled by the ER-located type-I transmembrane protein Ire1 [1,2]. The luminal domain of Ire directly senses unfolded proteins that accumulate in the ER, leading to activation of Ire as an endoribonuclease [4,5,6]. The accumulation of unfolded proteins in the ER and LBS are distinct types of ER stress-inducing stimuli that are both detected by Ire, but in different ways

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