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[SWI], the prion formed by the chromatin remodeling factor Swi1, is highly sensitive to alterations in Hsp70 chaperone system activity.

Hines JK, Li X, Du Z, Higurashi T, Li L, Craig EA - PLoS Genet. (2011)

Bottom Line: In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins.Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state.Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT
The yeast prion [SWI+], formed of heritable amyloid aggregates of the Swi1 protein, results in a partial loss of function of the SWI/SNF chromatin-remodeling complex, required for the regulation of a diverse set of genes. Our genetic analysis revealed that [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 Ssa, two of its J-protein co-chaperones, Sis1 and Ydj1, and the nucleotide exchange factors of the Hsp110 family (Sse1/2). Notably, while all yeast prions tested thus far require Sis1, [SWI+] is the only one known to require the activity of Ydj1, the most abundant J-protein in yeast. The C-terminal region of Ydj1, which contains the client protein interaction domain, is required for [SWI+] propagation. However, Ydj1 is not unique in this regard, as another, closely related J-protein, Apj1, can substitute for it when expressed at a level approaching that of Ydj1. While dependent upon Ydj1 and Sis1 for propagation, [SWI+] is also highly sensitive to overexpression of both J-proteins. However, this increased prion-loss requires only the highly conserved 70 amino acid J-domain, which serves to stimulate the ATPase activity of Hsp70 and thus to stabilize its interaction with client protein. Overexpression of the J-domain from Sis1, Ydj1, or Apj1 is sufficient to destabilize [SWI+]. In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins. Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state. Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments.

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[SWI+] is destabilized by overexpression of Sse1 or Sse2.Wild-type [SWI+] cells were transformed with either empty vector or vectors expressing Sse1 or Sse2 from high copy plasmids under the control of the constitutive GPD promoter. (A and B) One representative transformant for each vector is shown. (A) Serial dilutions of individual transformants were spotted onto raffinose- and glucose-based media to test for [SWI+] loss. [SWI+] cells receiving only empty vector and [swi−] cells were used as controls. (B) [SWI+] maintenance was also monitored by transformation of the original transformants with vector expressing Swi1NQ-YFP, and subsequent fluorescence analysis. (C) Results for each vector are expressed as the fraction of the original transformants which remained [SWI+] over the total number examined (Fraction [SWI+]).
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pgen-1001309-g007: [SWI+] is destabilized by overexpression of Sse1 or Sse2.Wild-type [SWI+] cells were transformed with either empty vector or vectors expressing Sse1 or Sse2 from high copy plasmids under the control of the constitutive GPD promoter. (A and B) One representative transformant for each vector is shown. (A) Serial dilutions of individual transformants were spotted onto raffinose- and glucose-based media to test for [SWI+] loss. [SWI+] cells receiving only empty vector and [swi−] cells were used as controls. (B) [SWI+] maintenance was also monitored by transformation of the original transformants with vector expressing Swi1NQ-YFP, and subsequent fluorescence analysis. (C) Results for each vector are expressed as the fraction of the original transformants which remained [SWI+] over the total number examined (Fraction [SWI+]).

Mentions: The Hsp110-type Sse protein family consists of two homologous isoforms Sse1 and Sse2 [50]. Because [SWI+] has exhibited a high sensitivity to ectopic chaperone expression, we also tested whether overexpression of either isoform would affect [SWI+]. To do this, [SWI+] cells were transformed with high-copy plasmids expressing either Sse1 or Sse2 from the constitutive GPD promoter or, as a control, empty vector. Overexpression of either isoform significantly destabilized [SWI+] relative to strains transformed with empty vector (Figure 7). Greater than 92% of the transformants overexpressing an NEF became [swi−], while less than 4% of the vector control did. We conclude that stable [SWI+] propagation requires moderate expression of Sse proteins.


[SWI], the prion formed by the chromatin remodeling factor Swi1, is highly sensitive to alterations in Hsp70 chaperone system activity.

Hines JK, Li X, Du Z, Higurashi T, Li L, Craig EA - PLoS Genet. (2011)

[SWI+] is destabilized by overexpression of Sse1 or Sse2.Wild-type [SWI+] cells were transformed with either empty vector or vectors expressing Sse1 or Sse2 from high copy plasmids under the control of the constitutive GPD promoter. (A and B) One representative transformant for each vector is shown. (A) Serial dilutions of individual transformants were spotted onto raffinose- and glucose-based media to test for [SWI+] loss. [SWI+] cells receiving only empty vector and [swi−] cells were used as controls. (B) [SWI+] maintenance was also monitored by transformation of the original transformants with vector expressing Swi1NQ-YFP, and subsequent fluorescence analysis. (C) Results for each vector are expressed as the fraction of the original transformants which remained [SWI+] over the total number examined (Fraction [SWI+]).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3040656&req=5

pgen-1001309-g007: [SWI+] is destabilized by overexpression of Sse1 or Sse2.Wild-type [SWI+] cells were transformed with either empty vector or vectors expressing Sse1 or Sse2 from high copy plasmids under the control of the constitutive GPD promoter. (A and B) One representative transformant for each vector is shown. (A) Serial dilutions of individual transformants were spotted onto raffinose- and glucose-based media to test for [SWI+] loss. [SWI+] cells receiving only empty vector and [swi−] cells were used as controls. (B) [SWI+] maintenance was also monitored by transformation of the original transformants with vector expressing Swi1NQ-YFP, and subsequent fluorescence analysis. (C) Results for each vector are expressed as the fraction of the original transformants which remained [SWI+] over the total number examined (Fraction [SWI+]).
Mentions: The Hsp110-type Sse protein family consists of two homologous isoforms Sse1 and Sse2 [50]. Because [SWI+] has exhibited a high sensitivity to ectopic chaperone expression, we also tested whether overexpression of either isoform would affect [SWI+]. To do this, [SWI+] cells were transformed with high-copy plasmids expressing either Sse1 or Sse2 from the constitutive GPD promoter or, as a control, empty vector. Overexpression of either isoform significantly destabilized [SWI+] relative to strains transformed with empty vector (Figure 7). Greater than 92% of the transformants overexpressing an NEF became [swi−], while less than 4% of the vector control did. We conclude that stable [SWI+] propagation requires moderate expression of Sse proteins.

Bottom Line: In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins.Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state.Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

ABSTRACT
The yeast prion [SWI+], formed of heritable amyloid aggregates of the Swi1 protein, results in a partial loss of function of the SWI/SNF chromatin-remodeling complex, required for the regulation of a diverse set of genes. Our genetic analysis revealed that [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 Ssa, two of its J-protein co-chaperones, Sis1 and Ydj1, and the nucleotide exchange factors of the Hsp110 family (Sse1/2). Notably, while all yeast prions tested thus far require Sis1, [SWI+] is the only one known to require the activity of Ydj1, the most abundant J-protein in yeast. The C-terminal region of Ydj1, which contains the client protein interaction domain, is required for [SWI+] propagation. However, Ydj1 is not unique in this regard, as another, closely related J-protein, Apj1, can substitute for it when expressed at a level approaching that of Ydj1. While dependent upon Ydj1 and Sis1 for propagation, [SWI+] is also highly sensitive to overexpression of both J-proteins. However, this increased prion-loss requires only the highly conserved 70 amino acid J-domain, which serves to stimulate the ATPase activity of Hsp70 and thus to stabilize its interaction with client protein. Overexpression of the J-domain from Sis1, Ydj1, or Apj1 is sufficient to destabilize [SWI+]. In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins. Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state. Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments.

Show MeSH
Related in: MedlinePlus