The Ydj1 molecular chaperone facilitates formation of active p60v-src in yeast.

Dey, Barna; Caplan, Avrom J.; Boschelli, Frank

doi:10.1091/mbc.7.1.91

Cited by 65 publications

(69 citation statements)

References 52 publications

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“…v-Src protein did not accumulate in ydj1 mutant strains expressing N134 and N274, but it is unknown whether this is due to lower levels of v-Src mRNA or reduced protein stability. In cells expressing G315E, the level of v-Src is unaffected, but the protein is much less active, results similar to those observed for the ydj1-G315D (29) and ydj1-151 mutations (15). Analysis of Hsp90 mutants also revealed affects on v-Src activity as well as stability (40), suggesting multiple roles for both Hsp90 and Ydj1 in v-Src maturation.…”

Section: Discussionmentioning

confidence: 54%

A Role for the Hsp40 Ydj1 in Repression of Basal Steroid Receptor Activity in Yeast

Johnson

Craig

2000

Molecular and Cellular Biology

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In addition to its roles in translocation of preproteins across membranes, Ydj1 facilitates the maturation of Hsp90 substrates, including mammalian steroid receptors, which activate transcription in yeast in a hormonedependent manner. To better understand Ydj1's function, we have constructed and analyzed an array of Ydj1 mutants in vivo. Both the glucocorticoid receptor and the estrogen receptor exhibited elevated activity in the absence of hormone in all ydj1 mutant strains, indicating a strict requirement for Ydj1 activity in hormonal control. Glucocorticoid receptor containing a mutation in the carboxy-terminal transcriptional activation domain, AF-2, retained elevated basal activity, while mutation of the amino-terminal transactivation domain, AF-1, eliminated the elevated basal activity observed in ydj1 mutant strains. This result indicates that the source of activity is AF-1, which is normally repressed by the carboxy-terminal hormone binding domain in the absence of hormone. Chimeric proteins containing the hormone binding domain of the estrogen or glucocorticoid receptor fused to heterologous activation and DNA binding domains also exhibited elevated activity in the absence of hormone. Thus, Ydj1 mutants appear to increase basal receptor activity by altering the ability of the hormone binding domain of the receptor to repress nearby activation domains. We propose that Ydj1 functions to present steroid receptors to the Hsp90 pathway for folding and hormonal control. In the presence of Ydj1 mutants that fail to bind substrate efficiently, some receptor escapes the Hsp90 pathway, resulting in constitutive activity.Hsp90, a highly conserved, abundant, and essential cytosolic molecular chaperone, functions in the maturation of a limited set of substrate proteins. Hsp90 was originally found to be involved in the activation of proteins involved in signaling pathways such as steroid hormone receptors and the oncogenic tyrosine kinase v-Src. Recent studies have revealed interaction with the hepatitis B retrovirus, nitric oxide synthase, telomerase, and the mutant form of p53 (7,23), suggesting that Hsp90 may be involved in the maturation of many diverse substrates.Hsp90 functions with a number of cochaperones in an apparently dynamic but ordered pathway leading to substrate maturation (48). Much of what is known about the interaction of Hsp90 and cochaperones with substrate proteins comes from studies of steroid hormone receptors (45). Besides promoting receptor activity, Hsp90 and cochaperones prevent steroid receptor activity in the absence of hormone, as receptors bound to Hsp90 cannot bind DNA and are therefore inactive as transcription factors. In vitro studies in reticulocyte lysates have led to the identification of proteins required for steroid receptor activation. Purified receptor is unable to bind hormone, but incubation in reticulocyte lysate results in a form of the receptor bound to Hsp90, p23, and immunophilins of the cyclophilin and FK506-binding protein classes (45). This mature form is capable o...

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Section: Discussionmentioning

confidence: 54%

A Role for the Hsp40 Ydj1 in Repression of Basal Steroid Receptor Activity in Yeast

Johnson

Craig

2000

Molecular and Cellular Biology

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“…Although the biochemical function of the mTid-1⅐GAP complex is not known, enhanced binding of mTid-1 I to GAP may conceivably exert inhibitory effects on GAP activity. In this context, it is note- worthy that the persistent association of a Ydj1 mutant with v-src severely compromises the in vivo activity of the kinase without affecting the levels of v-src in the cell (26). Alternatively, increased binding of mTid-1 with GAP may serve to sequester GAP away from Ras.…”

Section: Resultsmentioning

confidence: 99%

“…In this context, they regulate many facets of the signaling process that have been described for protein modules such as pleckstrin homology SH2 and SH3 domains, namely subcellular localization, regulation of enzymatic activity, and enzyme/substrate recognition (5). For example, genetic studies of v-src toxicity in yeast indicate that the DnaJ protein, Ydj1, is necessary for the correct subcellular targeting and kinase activation of v-src (26,27). Ydj1 has also been implicated as a positive regulator of cell cycle progression essential for efficient recognition and phosphorylation of cyclin CLN3 by cdc28, events that signal CLN3 degradation (28).…”

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confidence: 99%

A Mouse Homologue of the Drosophila Tumor Suppressor l(2)tid Gene Defines a Novel Ras GTPase-activating Protein (RasGAP)-binding Protein

Trentin¹,

Yin²,

Tahir³

et al. 2001

Journal of Biological Chemistry

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p120 GTPase-activating protein (GAP) down-regulates Ras by stimulating GTP hydrolysis of active Ras. In addition to its association with Ras, GAP has been shown to bind to several tyrosine-phosphorylated proteins in cells stimulated by growth factors or expressing transforming tyrosine kinase variants. Here we report the cloning and characterization of a novel GAP-binding protein, mTid-1, a DnaJ chaperone protein that represents the murine homolog of the Drosophila tumor suppressor l(2)tid gene. Three alternatively spliced variants of mTid-1 were isolated, two of which correspond to the recently identified hTid-1 L and hTid-1 S forms of the human TID1 gene that exhibit opposing effects on apoptosis. We demonstrate that both cytoplasmic precursor and mitochondrial mature forms of mTid-1 associate with GAP in vivo. Interestingly, although mTid-1 is found tyrosine-phosphorylated in v-src-transformed fibroblast cells, GAP selectively binds to the unphosphorylated form of mTid-1. In immunofluorescence experiments, GAP and Tid-1 were shown to colocalize at perinuclear mitochondrial membranes in response to epidermal growth factor stimulation. These findings raise the possibility that Tid chaperone proteins may play a role in governing the conformation, activity, and/or subcellular distribution of GAP, thereby influencing its biochemical and biological activity within cells.

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“…Furthermore, comparison of the results presented here with those previously reported using heterologous clients reveals some common trends. Deletion of CPR6 or SBA1, for example, results in a only a slight defect in v-Src or nuclear receptor signaling, whereas deletion of CPR7 or YDJ1 resulted in strong signaling defects (Kimura et al, 1995;Dey et al, 1996;Duina et al, 1996;Warth et al, 1997;Fang et al, 1998). By correlation, cochaperones that are essential for viability are also likely to play essential roles in the folding pathway; examples here are Cdc37 and Cns1.…”

Section: Discussionmentioning

confidence: 97%

Sti1 and Cdc37 Can Stabilize Hsp90 in Chaperone Complexes with a Protein Kinase

Lee

Shabbir

Cardozo

et al. 2004

MBoC

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Hsp90 functions in association with several cochaperones for folding of protein kinases and transcription factors, although the relative contribution of each to the overall reaction is unknown. We assayed the role of nine different cochaperones in the activation of Ste11, a Saccharomyces cerevisiae mitogen-activated protein kinase kinase kinase. Studies on signaling via this protein kinase pathway was measured by ␣-factor-stimulated induction of FIG1 or lacZ, and repression of HHF1. Several cochaperone mutants tested had reduced FIG1 induction or HHF1 repression, although to differing extents. The greatest defects were in cpr7⌬, sse1⌬, and ydj1⌬ mutants. Assays of Ste11 kinase activity revealed a pattern of defects in the cochaperone mutant strains that were similar to the gene expression studies. Overexpression of CDC37, a chaperone required for protein kinase folding, suppressed defects the sti1⌬ mutant back to wild-type levels. CDC37 overexpression also restored stable Hsp90 binding to the Ste11 protein kinase domain in the sti1⌬ mutant strain. These data suggest that Cdc37 and Sti1 have functional overlap in stabilizing Hsp90:client complexes. Finally, we show that Cns1 functions in MAP kinase signaling in association with Cpr7. INTRODUCTIONAmong several major classes of molecular chaperone that have been characterized, Hsp90 appears to function primarily in folding of signal transducing proteins such as transcription factors and protein kinases (Caplan, 1999;Prodromou and Pearl, 2003). Hsp90 does not act alone in this capacity, but in association with several cochaperones that may also have chaperone function as defined by their ability to prevent polypeptide aggregation in vitro.The current understanding of how Hsp90 cochaperones function derived from in vitro studies on progesterone receptors (PR) and glucocorticoid receptors (GR; Toft, 1997, 2003). The results of these studies showed that Hsp70 and Hsp40 first interact with the receptor ligandbinding domain. Hsp90 is recruited into this complex by the cochaperone called Hop, which interacts with both Hsp90 and Hsp70. Subsequently, Hsp70 and Hop are displaced by other cochaperones, such as one of many immunophilins and p23. Folding occurs in association with ATP hydrolysis by Hsp90, which is stimulated by another cochaperone called Aha1 (and its paralog Hch1; Panaretou et al., 2002;Lotz et al., 2003). It is unclear whether folding occurs while the receptor is in association with Hsp90 or after its release. Whether the cochaperones are required for this reaction is not clear, because purified Hsp70 and Hsp90 can together facilitate folding of GR in vitro, whereas cochaperones such as Hop stimulate the reaction (Morishima et al., 2000;Rajapandi et al., 2000). Furthermore, deletion of yeast Hop (STI1), or p23 (SBA1) does not result in a slow growth phenotype except under stress conditions (Nicolet and Craig, 1989;Chang et al., 1997;Bohen, 1998;Fang et al., 1998).Another question is whether the scheme described above for nuclear receptors reflects a set of ...

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The Ydj1 molecular chaperone facilitates formation of active p60v-src in yeast.

Cited by 65 publications

References 52 publications

A Role for the Hsp40 Ydj1 in Repression of Basal Steroid Receptor Activity in Yeast

A Role for the Hsp40 Ydj1 in Repression of Basal Steroid Receptor Activity in Yeast

A Mouse Homologue of the Drosophila Tumor Suppressor l(2)tid Gene Defines a Novel Ras GTPase-activating Protein (RasGAP)-binding Protein

Sti1 and Cdc37 Can Stabilize Hsp90 in Chaperone Complexes with a Protein Kinase

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