Characterization of a novel 23-kilodalton protein of inactive progesterone receptor complexes. Mol Cell Biol

Department of Biochemistry and Molecular Biology, Mayo Graduate School, Rochester, Minnesota 55905.
Molecular and Cellular Biology (Impact Factor: 4.78). 04/1994; 14(3):1956-63. DOI: 10.1128/MCB.14.3.1956
Source: PubMed

ABSTRACT Immunoprecipitation of unactivated avian progesterone receptor results in the copurification of hsp90, hsp70, and three additional proteins, p54, p50, and p23. p23 is also present in immunoaffinity-purified hsp90 complexes along with hsp70 and another protein, p60. Antibody and cDNA probes for p23 were prepared in an effort to elucidate the significance and function of this protein. Antibodies to p23 detect similar levels of p23 in all tissues tested and cross-react with a protein of the same size in mice, rabbits, guinea pigs, humans, and Saccharomyces cerevisiae, indicating that p23 is a conserved protein of broad tissue distribution. These antibodies were used to screen a chicken brain cDNA library, resulting in the isolation of a 468-bp partial cDNA clone encoding a sequence containing four sequences corresponding to peptide fragments isolated from chicken p23. This partial clone was subsequently used to isolate a full-length human cDNA clone. The human cDNA encodes a protein of 160 amino acids that does not show homology to previously identified proteins. The chicken and human cDNAs are 88% identical at the DNA level and 96.3% identical at the protein level. p23 is a highly acidic phosphoprotein with an aspartic acid-rich carboxy-terminal domain. Bacterially overexpressed human p23 was used to raise several monoclonal antibodies to p23. These antibodies specifically immunoprecipitate p23 in complex with hsp90 in all tissues tested and can be used to immunoaffinity isolate progesterone receptor complexes from chicken oviduct cytosol.

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Available from: Jill L Johnson, Jun 29, 2015
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    • "These co-chaperones assist Hsp90 by modulating its ATPase cycle and by facilitating its interactions with various client/substrate proteins [8-10]. An extensively studied Hsp90 co-chaperone is p23 (known as Sba1 in the budding yeast Saccharomyces cerevisiae) [11,12]. This ubiquitous acidic protein binds and stabilizes the ATP-bound dimeric form of Hsp90 [10,13,14], inhibits ATP hydrolysis and thereby traps Hsp90 in a state with high affinity for client proteins [15,16]. "
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    ABSTRACT: To make sense out of gene expression profiles, such analyses must be pushed beyond the mere listing of affected genes. For example, if a group of genes persistently display similar changes in expression levels under particular experimental conditions, and the proteins encoded by these genes interact and function in the same cellular compartments, this could be taken as very strong indicators for co-regulated protein complexes. One of the key requirements is having appropriate tools to detect such regulatory patterns. We have analyzed the global adaptations in gene expression patterns in the budding yeast when the Hsp90 molecular chaperone complex is perturbed either pharmacologically or genetically. We integrated these results with publicly accessible expression, protein-protein interaction and intracellular localization data. But most importantly, all experimental conditions were simultaneously and dynamically visualized with an animation. This critically facilitated the detection of patterns of gene expression changes that suggested underlying regulatory networks that a standard analysis by pairwise comparison and clustering could not have revealed. The results of the animation-assisted detection of changes in gene regulatory patterns make predictions about the potential roles of Hsp90 and its co-chaperone p23 in regulating whole sets of genes. The simultaneous dynamic visualization of microarray experiments, represented in networks built by integrating one's own experimental with publicly accessible data, represents a powerful discovery tool that allows the generation of new interpretations and hypotheses.
    BioData Mining 06/2011; 4(1):15. DOI:10.1186/1756-0381-4-15 · 2.02 Impact Factor
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    • "ture of wheat HSP20 ( van Montfort et al . , 2001b ) reveals that its fold closely resembles that of the CS ( CHORD and SGT1 ) domain ( Finn et al . , 2006 ) found in SGT1 and p23 , which are required for binding to HSP90 ( Boter et al . , 2007 ) . p23 regulates human HSP90 activity by direct interaction with the ATP - bound active form of HSP90 ( Johnson et al . , 1994 ) . The related folds of HSP20s and p23 , together with the experi - mentally verified chaperoning activities of both , could indicate a similar biochemical function as chaperones and co - regulators of HSP90 activity ( Bose et al . , 1996 ) . However , we were not able to detect an interaction between RSI2 and the I - 2 - interacting H"
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    ABSTRACT: Race-specific disease resistance in plants depends on the presence of resistance (R) genes. Most R genes encode NB-ARC-LRR proteins that carry a C-terminal leucine-rich repeat (LRR). Of the few proteins found to interact with the LRR domain, most have proposed (co)chaperone activity. Here, we report the identification of RSI2 (Required for Stability of I-2) as a protein that interacts with the LRR domain of the tomato R protein I-2. RSI2 belongs to the family of small heat shock proteins (sHSPs or HSP20s). HSP20s are ATP-independent chaperones that form oligomeric complexes with client proteins to prevent unfolding and subsequent aggregation. Silencing of RSI2-related HSP20s in Nicotiana benthamiana compromised the hypersensitive response that is normally induced by auto-active variants of I-2 and Mi-1, a second tomato R protein. As many HSP20s have chaperone properties, the involvement of RSI2 and other R protein (co)chaperones in I-2 and Mi-1 protein stability was examined. RSI2 silencing compromised the accumulation of full-length I-2 in planta, but did not affect Mi-1 levels. Silencing of heat shock protein 90 (HSP90) and SGT1 led to an almost complete loss of full-length I-2 accumulation and a reduction in Mi-1 protein levels. In contrast to SGT1 and HSP90, RSI2 silencing led to accumulation of I-2 breakdown products. This difference suggests that RSI2 and HSP90/SGT1 chaperone the I-2 protein using different molecular mechanisms. We conclude that I-2 protein function requires RSI2, either through direct interaction with, and stabilization of I-2 protein or by affecting signalling components involved in initiation of the hypersensitive response.
    The Plant Journal 05/2010; 63(4):563-72. DOI:10.1111/j.1365-313X.2010.04260.x · 5.97 Impact Factor
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    • "Hsp90 is required for the activation and stabilization of several signaling proteins, referred to as client proteins of Hsp90. The acidic 23-kDa protein p23 was first identified as a component of the progesterone receptor (PR)–Hsp90 complex (Johnson et al. 1994). Since then, it has come to be widely recognized as a co-chaperone of Hsp90 (Felts and Toft 2003; Pratt and Toft 2003), possessing also passive chaperoning activity itself (Bose et al. 1996) as well as a reported prostaglandin synthase activity (Tanioka et al. 2000). "
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    ABSTRACT: The small acidic protein p23 is best described as a co-chaperone of Hsp90, an essential molecular chaperone in eukaryotes. p23 binds to the ATP-bound form of Hsp90 and stabilizes the Hsp90-client protein complex by slowing down ATP turnover. The stabilizing activity of p23 was first characterized in studies of steroid receptor-Hsp90 complexes. Earlier studies of the Hsp90 chaperone complex in plants suggested that a p23-like stabilizing activity was absent in plant cell lysates. Here, we show that p23-like proteins are present in plants and are capable of binding Hsp90, but unlike human p23 and yeast ortholog Sba1, the plant p23-like proteins do not stabilize the steroid receptor-Hsp90 complexes formed in wheat germ lysate. Furthermore, these proteins do not inhibit the ATPase activity of plant Hsp90. While transcripts of Arabidopsis thaliana p23-1 and Atp23-2 were detected under normal growing conditions, those of the closely related Brassica napus p23-1 were present only after moderate heat stress. These observations suggest that p23-like proteins in plants are conserved in their binding to Hsp90 but have evolved mechanisms of action different from their yeast and animal counterparts.
    Cell Stress and Chaperones 03/2010; 15(5):703-15. DOI:10.1007/s12192-010-0182-1 · 3.16 Impact Factor
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