title: Investigating the protein-protein interactions of the yeast Hsp90 chaperone system by two-hybrid analysis: potential uses and limitations of this approach.
abstract: The Hsp90 chaperone cycle involves sequential assembly of different Hsp90-containing multiprotein complexes, the accessory proteins ("cochaperones") that are associated with these complexes being exchanged as the cycle proceeds from its early to its late stages. To gain insight as to whether the 2-hybrid system could be used to probe the interactions of this Hsp90 system, yeast transformants were constructed that express the Gal4p deoxyribonucleic acid-binding domain (BD) fused to the 2 Hsp90 isoforms and the various Hsp90 system cochaperones of yeast. These "bait" fusions were then introduced by mating into other transformants expressing nearly all the 6000 proteins of yeast expressed as fusions to the Gal4p activation domain (AD). High throughput 2-hybrid screening revealed the ability of Hsp90 and Hsp90 system cochaperones to engage in stable interactions in vivo, both with each other and with the various other proteins of the yeast proteome. Consistent with the transience of most chaperone associations, interactions to Hsp90 itself were invariably weak and generally influenced by stress. Mutations within a Hsp90-BD bait fusion and an AD-Cdc37 "prey" fusion were used to provide in vivo confirmation of the in vitro data that shows that Cdc37p is interacting with the "relaxed" conformation of Hsp90 and also to provide indications that Cdc37p needs to be phosphorylated at its N-terminus for any appreciable interaction with Hsp90. A number of potentially novel cochaperone interactions were also identified, providing a framework for these to be analyzed further using other techniques.
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Millson
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Truman
authors.forename: Francis
authors.initials: F
authors.lastname: Wolfram
authors.forename: Victoria
authors.initials: V
authors.lastname: King
authors.forename: Barry
authors.initials: B
authors.lastname: Panaretou
authors.forename: Chrisostomos
authors.initials: C
authors.lastname: Prodromou
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Pearl
authors.forename: Peter W
authors.initials: PW
authors.lastname: Piper
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008858:Microscopy, Phase-Contrast; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins