Kinetochore genes are required to fully activate secretory pathway expansion in S. cerevisiae under induced ER stress.
Basal ER stress occurs when proteins misfold in normal physiological conditions and are corrected by the unfolded protein response (UPR). Elevated ER stress occurs when misfolding is refractory as found in numerous diseases such as atherosclerosis, Type II diabetes and some cancers. In elevated ER stress it is unclear whether cells utilise the same or different networks of genes as in basal levels of ER stress. To probe this question, we used secretory pathway reporters Yip3p-GFP, Erv29p-GFP, Orm2p-GFP and UPREpr-GFP placed on the yeast deletion mutant array (DMA) genetic background. The reporter's expression levels, measured by automated microscopy, at basal versus elevated ER stress induced by the over-expression of CPY* were compared. A novel group of kinetochore genes (CTF19 complex) were found to be uniquely required for full induction of all four ER stress reporters in elevated stress. A follow-up reporter screen was developed by mating the ctf19Δ kinetochore gene deletion strain into the genome-wide XXXp-GFP tagged library then testing with over-expressed CPY*. This screen identified Bcy1p and Bfr1p as possible signalling points that down-regulate the UPR and secretory pathway when kinetochore proteins are absent under elevated stress conditions. Bfr1p appears to be a checkpoint that monitors the integrity of kinetochores at increased levels of ER stress. This study concludes that functional kinetochores are required for full activation of the secretory pathway in elevated ER stress and that the responses to basal and elevated levels of ER stress require different networks of genes.
School of Biological Sciences, Victoria University of Wellington, Kelburn Parade, Wellington, New Zealand. paul.atkinson@vuw.ac.nz.
Yee S
YS
Low
Peter W
PW
Bircham
David R
DR
Maass
Paul H
PH
Atkinson
D002268:Carboxypeptidases / Q000235:genetics*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal; D016681:Genome, Fungal; D018386:Kinetochores / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D055571:Secretory Pathway / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects
C089100:BFR1 protein, S cerevisiae; C574570:Bcy1 protein, S cerevisiae; C477822:CTF19 protein, S cerevisiae; D003598:Cytoskeletal Proteins; D018942:Macrolides; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D002268:Carboxypeptidases; C520242:CPY protein, S cerevisiae