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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 sensitive to J-protein or J-domain overexpression.High copy plasmids expressing various J-proteins or J-domain containing fragments under the control of the constitutive GPD promoter were used to transform a wild type [SWI+] strain. Individual transformants were isolated, repatched once on media selective for the plasmid, and then retransformed with a Swi1NQ-YFP expression vector. YFP aggregation was used to score the original transformants for [SWI+] maintenance. The number of transformants remaining [SWI+] is reported as a fraction of the total examined (Fraction [SWI+]). Gene domain structures for the J-proteins Sis1, Ydj1, and Apj1 are shown using the following notation: J, J-domain; G/F, glycine/phenylalanine-rich region; G/M, glycine/methionine-rich region; peptide-binding, C-terminal peptide-binding domains I & II; Zn2+ & peptide-binding, Zinc finger-like region and peptide binding domains I & II; Gly, glycine-rich region; HA, hemegglutinin A tag. Random peptide sequence is indicated by a thin line.
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pgen-1001309-g004: [SWI+] is sensitive to J-protein or J-domain overexpression.High copy plasmids expressing various J-proteins or J-domain containing fragments under the control of the constitutive GPD promoter were used to transform a wild type [SWI+] strain. Individual transformants were isolated, repatched once on media selective for the plasmid, and then retransformed with a Swi1NQ-YFP expression vector. YFP aggregation was used to score the original transformants for [SWI+] maintenance. The number of transformants remaining [SWI+] is reported as a fraction of the total examined (Fraction [SWI+]). Gene domain structures for the J-proteins Sis1, Ydj1, and Apj1 are shown using the following notation: J, J-domain; G/F, glycine/phenylalanine-rich region; G/M, glycine/methionine-rich region; peptide-binding, C-terminal peptide-binding domains I & II; Zn2+ & peptide-binding, Zinc finger-like region and peptide binding domains I & II; Gly, glycine-rich region; HA, hemegglutinin A tag. Random peptide sequence is indicated by a thin line.

Mentions: Since Sis1 overexpression so potently affected [SWI+], we decided to test two other J-proteins, Ydj1 and Apj1, which had previously been found to affect yeast prions when overexpressed [12], [24], [42]–[45]. To this end, wild-type [SWI+] cells were transformed with either high-copy overexpression plasmids or empty vector. Transformants were repatched once before a second transformation with plasmid bearing Swi1NQ-YFP for prion scoring. The fate of at least 30 independent transformants was determined in each case. [SWI+] was maintained in >90% of control transformants receiving empty vector but, as expected, none of the transformants overexpressing Sis1 maintained the prion (Figure 4).


[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 sensitive to J-protein or J-domain overexpression.High copy plasmids expressing various J-proteins or J-domain containing fragments under the control of the constitutive GPD promoter were used to transform a wild type [SWI+] strain. Individual transformants were isolated, repatched once on media selective for the plasmid, and then retransformed with a Swi1NQ-YFP expression vector. YFP aggregation was used to score the original transformants for [SWI+] maintenance. The number of transformants remaining [SWI+] is reported as a fraction of the total examined (Fraction [SWI+]). Gene domain structures for the J-proteins Sis1, Ydj1, and Apj1 are shown using the following notation: J, J-domain; G/F, glycine/phenylalanine-rich region; G/M, glycine/methionine-rich region; peptide-binding, C-terminal peptide-binding domains I & II; Zn2+ & peptide-binding, Zinc finger-like region and peptide binding domains I & II; Gly, glycine-rich region; HA, hemegglutinin A tag. Random peptide sequence is indicated by a thin line.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3040656&req=5

pgen-1001309-g004: [SWI+] is sensitive to J-protein or J-domain overexpression.High copy plasmids expressing various J-proteins or J-domain containing fragments under the control of the constitutive GPD promoter were used to transform a wild type [SWI+] strain. Individual transformants were isolated, repatched once on media selective for the plasmid, and then retransformed with a Swi1NQ-YFP expression vector. YFP aggregation was used to score the original transformants for [SWI+] maintenance. The number of transformants remaining [SWI+] is reported as a fraction of the total examined (Fraction [SWI+]). Gene domain structures for the J-proteins Sis1, Ydj1, and Apj1 are shown using the following notation: J, J-domain; G/F, glycine/phenylalanine-rich region; G/M, glycine/methionine-rich region; peptide-binding, C-terminal peptide-binding domains I & II; Zn2+ & peptide-binding, Zinc finger-like region and peptide binding domains I & II; Gly, glycine-rich region; HA, hemegglutinin A tag. Random peptide sequence is indicated by a thin line.
Mentions: Since Sis1 overexpression so potently affected [SWI+], we decided to test two other J-proteins, Ydj1 and Apj1, which had previously been found to affect yeast prions when overexpressed [12], [24], [42]–[45]. To this end, wild-type [SWI+] cells were transformed with either high-copy overexpression plasmids or empty vector. Transformants were repatched once before a second transformation with plasmid bearing Swi1NQ-YFP for prion scoring. The fate of at least 30 independent transformants was determined in each case. [SWI+] was maintained in >90% of control transformants receiving empty vector but, as expected, none of the transformants overexpressing Sis1 maintained the prion (Figure 4).

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