Navigating the Chaperone Network: An Integrative Map of Physical and Genetic Interactions Mediated by the Hsp90 Chaperone

Abstract

Physical, genetic, and chemical-genetic interactions centered on the conserved chaperone Hsp90 were mapped at high resolution in yeast using systematic proteomic and genomic methods. Physical interactions were identified using genome-wide two hybrid screens combined with large-scale affinity purification of Hsp90-containing protein complexes. Genetic interactions were uncovered using synthetic genetic array technology and by a microarray-based chemical-genetic screen of a set of about 4700 viable yeast gene deletion mutants for hypersensitivity to the Hsp90 inhibitor geldanamycin. An extended network, consisting of 198 putative physical interactions and 451 putative genetic and chemical-genetic interactions, was found to connect Hsp90 to cofactors and substrates involved in a wide range of cellular functions. Two novel Hsp90 cofactors, Tah1 (YCR060W) and Pih1 (YHR034C), were also identified. These cofactors interact physically and functionally with the conserved AAA(+)-type DNA helicases Rvb1/Rvb2, which are key components of several chromatin remodeling factors, thereby linking Hsp90 to epigenetic gene regulation.

The complementation of yeast with human or Plasmodium falciparum Hsp90 confers differential inhibitor sensitivities

“…We now add Pf Hsp90 to the list of heterologous Hsp90's that can apparently fulfill at least the essential functions of Hsp90 in yeast for vegetative growth in standard growth media. Whatever these functions are exactly, they must include many of the ones that have been highlighted by global biochemical and genetic analyses of Hsp90 interactions in this organism [25][26][27][28]. The results of these genetic complementation experiments underscore the high evolutionary conservation of Hsp90 [29][30][31][32].…”

Heparin exerts a dual effect on murine lupus nephritis by enhancing enzymatic chromatin degradation and preventing chromatin binding in glomerular membranes

“…For example, nucleosome assembly protein 1, nucleoplasmin, and Hsp90 induce changes in chromatin conformation that are assumed to increase accessibility for proteinases and nucleases (20)(21)(22)(23)(24)(25). It is not known whether such molecules are tolerated in vivo in doses necessary for a therapeutic effect.…”

Chaperone-related immune dysfunction: an emergent property of distorted chaperone networks

“…This prompts the investigation of immune dysfunction in chaperone deficiencies and folding diseases and suggests novel experiments to assess the role of molecular chaperones in immune function during stress and aging. Because our proposal is related to the function of molecular chaperones [2] are shown using the Osprey program [50]. Human homologs of yeast network members were included, using the Saccharomyces Genome Database (http://www.yeastgenome.org).…”

“…Chaperones are important parts of cellular networks, forming complexes with each other, with the numerous co-chaperones regulating their function and with hundreds of other cellular proteins. Examples of these chaperone-related network modules, the recently described 627 members of the yeast 90 kDa Hsp (Hsp90) network [2] and the known 160 binding partners of Hsp90 are shown in Figure 1. Behaving as key elements (hubs) in the organization of the protein-interaction networks and genetic-regulatory and membrane or organelle networks of the cell, chaperones promote crosstalk between various signaling pathways, regulate transcriptional networks and might have a role in the coupling of the membrane network of mitochondria, the endoplasmic reticulum and the cell nucleus [3].…”