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Title: The Hsp90 requirement in the Slt2p stress-activated MAP kinase activity of yeast
Author: Truman, Andrew William
ISNI:       0000 0001 3536 8356
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2005
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The Hsp90 molecular chaperone function is essential and extremely well conserved in eukaryotic organisms, yet much of the mechanism of Hsp90 action remains a mystery. This investigation set out to identify a model client protein of Hsp90 in the yeast Saccharomyces cerevisiae that would be amenable to structural and genetic analysis. Initial studies were conducted on HSF (1-583) strain, which has a C-terminally truncated heat shock transcription factor resulting in low Hsp90 expression. This mutant displayed a swollen cell phenotype that could be suppressed with osmotic stabilisation, indicating that the mutant had defective maintenance of cell wall integrity under stress conditions. This was shown to be a result of an inability to activate Rim 1p, the transcription factor regulated by the cell integrity MAP kinase pathway. Expression of the T22I mutant form of the Hsp82 isoform of Hsp90 expressed as the sole Hsp90 of the cell was also shown to generate a cell integrity defect. Unlike with HSF (1-583), this is apparent at low as well as high temperatures of growth. An interaction between Hsp82 and the MAP kinase Slt2p, the activator of RIm 1p, was demonstrated by both protein binding and two hybrid studies. This interaction was shown to be reinforced under cell wall stressing conditions and dependent on the phosphorylation status of S1t2p. The final part of this investigation revealed that mammalian BMK1 (ERK5) MAP kinase can substantially provide Slt2p MAP kinase function in yeast. We demonstrated that this BMKl protein could associate with both isoforms of Hsp90 in yeast, Hsp82 and Hsc82. Overall, the data indicated the Slt2p MAP kinase is a client protein of Hsp82, providing the first evidence for an Hsp90 involvement in activity of a member of the MAP kinase family proteins.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available