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    Global transcript and phenotypic analysis of yeast cells expressing Ssa1, Ssa2, Ssa3 or Ssa4 as sole source of cytosolic Hsp70-Ssa chaperone activity

    Hasin, Naushaba and Cusack, Sarah and Ali, Shahin S. and Fitzpatrick, David A. and Jones, Gary W. (2014) Global transcript and phenotypic analysis of yeast cells expressing Ssa1, Ssa2, Ssa3 or Ssa4 as sole source of cytosolic Hsp70-Ssa chaperone activity. BMC Genomics, 15 (194). pp. 1-12. ISSN 1471-2164

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    Background: Cytosolic Hsp70 is a ubiquitous molecular chaperone that is involved in responding to a variety of cellular stresses. A major function of Hsp70 is to prevent the aggregation of denatured proteins by binding to exposed hydrophobic regions and preventing the accumulation of amorphous aggregates. To gain further insight into the functional redundancy and specialisation of the highly homologous yeast Hsp70-Ssa family we expressed each of the individual Ssa proteins as the sole source of Hsp70 in the cell and assessed phenotypic differences in prion propagation and stress resistance. Additionally we also analysed the global gene expression patterns in yeast strains expressing individual Ssa proteins, using microarray and RT-qPCR analysis. Results: We confirm and extend previous studies demonstrating that cells expressing different Hsp70-Ssa isoforms vary in their ability to propagate the yeast [PSI+] prion, with Ssa3 being the most proficient. Of the four Ssa family members the heat inducible isoforms are more proficient in acquiring thermotolerance and we show a greater requirement than was previously thought, for cellular processes in addition to the traditional Hsp104 protein disaggregase machinery, in acquiring such thermotolerance. Cells expressing different Hsp70-Ssa isoforms also display differences in phenotypic response to exposure to cell wall damaging and oxidative stress agents, again with the heat inducible isoforms providing better protection than constitutive isoforms. We assessed global transcriptome profiles for cells expressing individual Hsp70-Ssa isoforms as the sole source of cytosolic Hsp70, and identified a significant difference in cellular gene expression between these strains. Differences in gene expression profiles provide a rationale for some phenotypic differences we observed in this study. We also demonstrate a high degree of correlation between microarray data and RT-qPCR analysis for a selection of genes. Conclusions: The Hsp70-Ssa family provide both redundant and variant-specific functions within the yeast cell. Yeast cells expressing individual members of the Hsp70-Ssa family as the sole source of Ssa protein display differences in global gene expression profiles. These changes in global gene expression may contribute significantly to the phenotypic differences observed between the Hsp70-Ssa family members.

    Item Type: Article
    Additional Information: © 2014 Hasin et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated. We thank Daniel Masison for plasmids, Elizabeth Craig and John Glover for antibodies, used in this study. This work was supported in part by Science Foundation Ireland grant RFP/07/BIC493 awarded to GWJ. NH was supported by a John and Pat Hume postgraduate scholarship. Microarray analysis was performed by Toray Industries as part of a 3D-GeneTM Competition Award to GWJ.
    Keywords: Saccharomyces cerevisiae; Prion; Heat shock; Stress; Hsp70; Ssa1; Ssa2; Ssa3; Ssa4; Chaperone; Gene expression;
    Academic Unit: Faculty of Science and Engineering > Biology
    Item ID: 6019
    Identification Number:
    Depositing User: Dr. Gary Jones
    Date Deposited: 10 Apr 2015 15:50
    Journal or Publication Title: BMC Genomics
    Publisher: BioMed Central
    Refereed: Yes
    Funders: Science Foundation Ireland (SFI), John and Pat Hume postgraduate scholarship, Toray Industries
      Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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