1
|
Denney AS, Weems AD, McMurray MA. Selective functional inhibition of a tumor-derived p53 mutant by cytosolic chaperones identified using split-YFP in budding yeast. G3-GENES GENOMES GENETICS 2021; 11:6318398. [PMID: 34544131 PMCID: PMC8496213 DOI: 10.1093/g3journal/jkab230] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 06/17/2021] [Indexed: 11/25/2022]
Abstract
Life requires the oligomerization of individual proteins into higher-order assemblies. In order to form functional oligomers, monomers must adopt appropriate 3D structures. Molecular chaperones transiently bind nascent or misfolded proteins to promote proper folding. Single missense mutations frequently cause disease by perturbing folding despite chaperone engagement. A misfolded mutant capable of oligomerizing with wild-type proteins can dominantly poison oligomer function. We previously found evidence that human-disease-linked mutations in Saccharomyces cerevisiae septin proteins slow folding and attract chaperones, resulting in a kinetic delay in oligomerization that prevents the mutant from interfering with wild-type function. Here, we build upon our septin studies to develop a new approach for identifying chaperone interactions in living cells, and use it to expand our understanding of chaperone involvement, kinetic folding delays, and oligomerization in the recessive behavior of tumor-derived mutants of the tumor suppressor p53. We find evidence of increased binding of several cytosolic chaperones to a recessive, misfolding-prone mutant, p53(V272M). Similar to our septin results, chaperone overexpression inhibits the function of p53(V272M) with minimal effect on the wild type. Unlike mutant septins, p53(V272M) is not kinetically delayed under conditions in which it is functional. Instead, it interacts with wild-type p53 but this interaction is temperature sensitive. At high temperatures or upon chaperone overexpression, p53(V272M) is excluded from the nucleus and cannot function or perturb wild-type function. Hsp90 inhibition liberates mutant p53 to enter the nucleus. These findings provide new insights into the effects of missense mutations.
Collapse
Affiliation(s)
- Ashley S Denney
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Andrew D Weems
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Michael A McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| |
Collapse
|
2
|
Villali J, Dark J, Brechtel TM, Pei F, Sindi SS, Serio TR. Nucleation seed size determines amyloid clearance and establishes a barrier to prion appearance in yeast. Nat Struct Mol Biol 2020; 27:540-549. [PMID: 32367069 PMCID: PMC7293557 DOI: 10.1038/s41594-020-0416-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 03/18/2020] [Indexed: 12/14/2022]
Abstract
Amyloid appearance is a rare event that is promoted in the presence of
other aggregated proteins. These aggregates were thought to act by templating
the formation of an assembly-competent nucleation seed, but we find an
unanticipated role for them in enhancing the persistence of amyloid after it
arises. Specifically, Saccharoymyces cerevisiae Rnq1 amyloid
reduces chaperone-mediated disassembly of Sup35 amyloid, promoting its
persistence in yeast. Mathematical modeling and corresponding in
vivo experiments link amyloid persistence to the conformationally
defined size of the Sup35 nucleation seed and suggest that amyloid is actively
cleared by disassembly below this threshold to suppress appearance of the
[PSI+] prion in vivo.
Remarkably, this framework resolves multiple known inconsistencies in the
appearance and curing of yeast prions. Thus, our observations establish the size
of the nucleation seed as a previously unappreciated characteristic of prion
variants that is key to understanding transitions between prion states.
Collapse
Affiliation(s)
- Janice Villali
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA.,Relay Therapeutics, Cambridge, MA, USA
| | - Jason Dark
- Department of Applied Mathematics, University of California, Merced, Merced, CA, USA
| | - Teal M Brechtel
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Fen Pei
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA.,BioLegend, San Diego, CA, USA
| | - Suzanne S Sindi
- Department of Applied Mathematics, University of California, Merced, Merced, CA, USA.
| | - Tricia R Serio
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA.
| |
Collapse
|
3
|
Oliver EE, Troisi EM, Hines JK. Prion-specific Hsp40 function: The role of the auxilin homolog Swa2. Prion 2017; 11:174-185. [PMID: 28574745 PMCID: PMC5480384 DOI: 10.1080/19336896.2017.1331810] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 05/09/2017] [Accepted: 05/10/2017] [Indexed: 01/14/2023] Open
Abstract
Yeast prions are protein-based genetic elements that propagate through cell populations via cytosolic transfer from mother to daughter cell. Molecular chaperone proteins including Hsp70, the Hsp40/J-protein Sis1, and Hsp104 are required for continued prion propagation, however the specific requirements of chaperone proteins differ for various prions. We recently reported that Swa2, the yeast homolog of the mammalian protein auxilin, is specifically required for the propagation of the prion [URE3]. 1 [URE3] propagation requires both a functional J-domain and the tetratricopeptide repeat (TPR) domain of Swa2, but does not require Swa2 clathrin binding. We concluded that the TPR domain determines the specificity of the genetic interaction between Swa2 and [URE3], and that this domain likely interacts with one or more proteins with a C-terminal EEVD motif. Here we extend that analysis to incorporate additional data that supports this hypothesis. We also present new data eliminating Hsp104 as the relevant Swa2 binding partner and discuss our findings in the context of other recent work involving Hsp90. Based on these findings, we propose a new model for Swa2's involvement in [URE3] propagation in which Swa2 and Hsp90 mediate the formation of a multi-protein complex that increases the number of sites available for Hsp104 disaggregation.
Collapse
|
4
|
Sharma J, Wisniewski BT, Paulson E, Obaoye JO, Merrill SJ, Manogaran AL. De novo [PSI +] prion formation involves multiple pathways to form infectious oligomers. Sci Rep 2017; 7:76. [PMID: 28250435 PMCID: PMC5427932 DOI: 10.1038/s41598-017-00135-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 02/09/2017] [Indexed: 11/09/2022] Open
Abstract
Prion and other neurodegenerative diseases are associated with misfolded protein assemblies called amyloid. Research has begun to uncover common mechanisms underlying transmission of amyloids, yet how amyloids form in vivo is still unclear. Here, we take advantage of the yeast prion, [PSI +], to uncover the early steps of amyloid formation in vivo. [PSI +] is the prion form of the Sup35 protein. While [PSI +] formation is quite rare, the prion can be greatly induced by overexpression of the prion domain of the Sup35 protein. This de novo induction of [PSI +] shows the appearance of fluorescent cytoplasmic rings when the prion domain is fused with GFP. Our current work shows that de novo induction is more complex than previously thought. Using 4D live cell imaging, we observed that fluorescent structures are formed by four different pathways to yield [PSI +] cells. Biochemical analysis of de novo induced cultures indicates that newly formed SDS resistant oligomers change in size over time and lysates made from de novo induced cultures are able to convert [psi -] cells to [PSI +] cells. Taken together, our findings suggest that newly formed prion oligomers are infectious.
Collapse
Affiliation(s)
- Jaya Sharma
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201, USA
| | - Brett T Wisniewski
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201, USA
| | - Emily Paulson
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201, USA
| | - Joanna O Obaoye
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201, USA
| | - Stephen J Merrill
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201, USA
| | - Anita L Manogaran
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201, USA.
| |
Collapse
|
5
|
Du Z, Goncharoff DK, Cheng X, Li L. Analysis of [SWI + ] formation and propagation events. Mol Microbiol 2017; 104:105-124. [PMID: 28035761 DOI: 10.1111/mmi.13616] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/26/2016] [Indexed: 01/01/2023]
Abstract
The budding yeast, Saccharomyces cerevisiae, harbors several prions that are transmitted as altered, heritable protein conformations. [SWI+ ] is one such prion whose determinant is Swi1, a subunit of the evolutionarily conserved chromatin-remodeling complex SWI/SNF. Despite the importance of Swi1, the molecular events that lead to [SWI+ ] prionogenesis remain poorly understood. In this study, we have constructed floccullin-promoter-based URA3 reporters for [SWI+ ] identification. Using these reporters, we show that the spontaneous formation frequency of [SWI+ ] is significantly higher than that of [PSI+ ] (prion form of Sup35). We also show that preexisting [PSI+ ] or [PIN+ ] (prion form of Rnq1), or overproduction of Swi1 prion-domain (PrD) can considerably promote Swi1 prionogenesis. Moreover, our data suggest a strain-specific effect of overproduction of Sse1 - a nucleotide exchange factor of the molecular chaperone Hsp70, and its interaction with another molecular chaperone Hsp104 on [SWI+ ] maintenance. Additionally, we show that Swi1 aggregates are initially ring/ribbon-like then become dot-like in mature [SWI+ ] cells. In the presence of [PSI+ ] or [PIN+ ], Swi1 ring/ribbon-like aggregates predominantly colocalize with the Sup35 or Rnq1 aggregates; without a preexisting prion, however, such colocalizations are rarely seen during Swi1-PrD overproduction-promoted Swi1 prionogenesis. We have thus demonstrated a complex interacting mechanism of yeast prionogenesis.
Collapse
Affiliation(s)
- Zhiqiang Du
- Department of Biochemistry and Molecular Genetics, the Feinberg School of Medicine, Northwestern University, 320 E Superior St, Searle 7-650, Chicago, IL, 60611, USA
| | - Dustin Kenneth Goncharoff
- Department of Biochemistry and Molecular Genetics, the Feinberg School of Medicine, Northwestern University, 320 E Superior St, Searle 7-650, Chicago, IL, 60611, USA
| | - Xudong Cheng
- Department of Biochemistry and Molecular Genetics, the Feinberg School of Medicine, Northwestern University, 320 E Superior St, Searle 7-650, Chicago, IL, 60611, USA
| | - Liming Li
- Department of Biochemistry and Molecular Genetics, the Feinberg School of Medicine, Northwestern University, 320 E Superior St, Searle 7-650, Chicago, IL, 60611, USA
| |
Collapse
|
6
|
Kumar N, Gaur D, Gupta A, Puri A, Sharma D. Hsp90-Associated Immunophilin Homolog Cpr7 Is Required for the Mitotic Stability of [URE3] Prion in Saccharomyces cerevisiae. PLoS Genet 2015; 11:e1005567. [PMID: 26473735 PMCID: PMC4608684 DOI: 10.1371/journal.pgen.1005567] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/14/2015] [Indexed: 11/18/2022] Open
Abstract
The role of Hsp70 chaperones in yeast prion propagation is well established. Highly conserved Hsp90 chaperones participate in a number of cellular processes, such as client protein maturation, protein degradation, cellular signalling and apoptosis, but little is known about their role in propagation of infectious prion like aggregates. Here, we examine the influence of Hsp90 in the maintenance of yeast prion [URE3] which is a prion form of native protein Ure2, and reveal a previously unknown role of Hsp90 as an important regulator of [URE3] stability. We show that the C-terminal MEEVD pentapeptide motif, but not the client maturation activity of Hsp90, is essential for [URE3] prion stability. In testing deletions of various Hsp90 co-chaperones known to bind this motif, we find the immunophilin homolog Cpr7 is essential for [URE3] propagation. We show that Cpr7 interacts with Ure2 and enhances its fibrillation. The requirement of Cpr7 is specific for [URE3] as its deletion does not antagonize both strong and weak variant of another yeast prion [PSI+], suggesting a distinct role of the Hsp90 co-chaperone with different yeast prions. Our data show that, similar to the Hsp70 family, the Hsp90 chaperones also influence yeast prion maintenance, and that immunophilins could regulate protein multimerization independently of their activity as peptidyl-prolyl isomerases.
Collapse
Affiliation(s)
- Navinder Kumar
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Deepika Gaur
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Arpit Gupta
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Anuradhika Puri
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| | - Deepak Sharma
- Council of Scientific and Industrial Research-Institute of Microbial Technology, Chandigarh, India
| |
Collapse
|
7
|
Kiktev DA, Melomed MM, Lu CD, Newnam GP, Chernoff YO. Feedback control of prion formation and propagation by the ribosome-associated chaperone complex. Mol Microbiol 2015; 96:621-32. [PMID: 25649498 DOI: 10.1111/mmi.12960] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2015] [Indexed: 01/01/2023]
Abstract
Cross-beta fibrous protein aggregates (amyloids and amyloid-based prions) are found in mammals (including humans) and fungi (including yeast), and are associated with both diseases and heritable traits. The Hsp104/70/40 chaperone machinery controls propagation of yeast prions. The Hsp70 chaperones Ssa and Ssb show opposite effects on [PSI(+)], a prion form of the translation termination factor Sup35 (eRF3). Ssb is bound to translating ribosomes via ribosome-associated complex (RAC), composed of Hsp40-Zuo1 and Hsp70-Ssz1. Here we demonstrate that RAC disruption increases de novo prion formation in a manner similar to Ssb depletion, but interferes with prion propagation in a manner similar to Ssb overproduction. Release of Ssb into the cytosol in RAC-deficient cells antagonizes binding of Ssa to amyloids. Thus, propagation of an amyloid formed because of lack of ribosome-associated Ssb can be counteracted by cytosolic Ssb, generating a feedback regulatory circuit. Release of Ssb from ribosomes is also observed in wild-type cells during growth in poor synthetic medium. Ssb is, in a significant part, responsible for the prion destabilization in these conditions, underlining the physiological relevance of the Ssb-based regulatory circuit.
Collapse
Affiliation(s)
- Denis A Kiktev
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA; Laboratory of Amyloid Biology, St. Petersburg State University, St. Petersburg, Russia
| | | | | | | | | |
Collapse
|
8
|
Johnson CR, Weems AD, Brewer JM, Thorner J, McMurray MA. Cytosolic chaperones mediate quality control of higher-order septin assembly in budding yeast. Mol Biol Cell 2015; 26:1323-44. [PMID: 25673805 PMCID: PMC4454179 DOI: 10.1091/mbc.e14-11-1531] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Septin hetero-oligomers polymerize into cytoskeletal filaments with essential functions in many eukaryotic cell types. Mutations within the oligomerization interface that encompasses the GTP-binding pocket of a septin (its "G interface") cause thermoinstability of yeast septin hetero-oligomer assembly, and human disease. When coexpressed with its wild-type counterpart, a G interface mutant is excluded from septin filaments, even at moderate temperatures. We show that this quality control mechanism is specific to G interface mutants, operates during de novo septin hetero-oligomer assembly, and requires specific cytosolic chaperones. Chaperone overexpression lowers the temperature permissive for proliferation of cells expressing a G interface mutant as the sole source of a given septin. Mutations that perturb the septin G interface retard release from these chaperones, imposing a kinetic delay on the availability of nascent septin molecules for higher-order assembly. Un-expectedly, the disaggregase Hsp104 contributes to this delay in a manner that does not require its "unfoldase" activity, indicating a latent "holdase" activity toward mutant septins. These findings provide new roles for chaperone-mediated kinetic partitioning of non-native proteins and may help explain the etiology of septin-linked human diseases.
Collapse
Affiliation(s)
- Courtney R Johnson
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Andrew D Weems
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Jennifer M Brewer
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Jeremy Thorner
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Michael A McMurray
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| |
Collapse
|
9
|
Abstract
Multiple prion elements, which are transmitted as heritable protein conformations and often linked to distinct phenotypes, have been identified in the budding yeast, Saccharomyces cerevisiae. It has been shown that overproduction of a prion protein Swi1 can promote the de novo conversion of another yeast prion [PSI(+)] when Sup35 is co-overproduced. However, the mechanism underlying this Pin(+) ([PSI(+)] inducible) activity is not clear. Moreover, how the Swi1 prion ([SWI(+)]) interacts with other yeast prions is unknown. Here, we demonstrate that the Pin(+) activity associated with Swi1 overproduction is independent of Rnq1 expression or [PIN(+)] conversion. We also show that [SWI(+)] enhances the appearance of [PSI(+)] and [PIN(+)]. However, [SWI(+)] significantly compromises the Pin(+) activity of [PIN(+)] when they coexist. We further demonstrate that a single yeast cell can harbor three prions, [PSI(+)], [PIN(+)], and [SWI(+)], simultaneously. However, under this condition, [SWI(+)] is significantly destabilized. While the propensity to aggregate underlies prionogenesis, Swi1 and Rnq1 aggregates resulting from overproduction are usually nonheritable. Conversely, prion protein aggregates formed in nonoverexpressing conditions or induced by preexisting prion(s) are more prionogenic. For [PSI(+)] and [PIN(+)] de novo formation, heterologous "facilitators," such as preexisting [SWI(+)] aggregates, colocalize only with the newly formed ring-/rod-shaped Sup35 or Rnq1 aggregates, but not with the dot-shaped mature prion aggregates. Their colocalization frequency is coordinated with their prion inducibility, indicating that prion-prion interactions mainly occur at the early initiation stage. Our results provide supportive evidence for the cross-seeding model of prionogenesis and highlight a complex interaction network among prions in yeast.
Collapse
|
10
|
Westergard L, True HL. Extracellular environment modulates the formation and propagation of particular amyloid structures. Mol Microbiol 2014; 92:698-715. [PMID: 24628771 DOI: 10.1111/mmi.12579] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2014] [Indexed: 11/27/2022]
Abstract
Amyloidogenic proteins, including prions, assemble into multiple forms of structurally distinct fibres. The [PSI(+)] prion, endogenous to the yeast Saccharomyces cerevisiae, is a dominantly inherited, epigenetic modifier of phenotypes. [PSI(+)] formation relies on the coexistence of another prion, [RNQ(+)]. Here, in order to better define the role of amyloid diversity on cellular phenotypes, we investigated how physiological and environmental changes impact the generation and propagation of diverse protein conformations from a single polypeptide. Utilizing the yeast model system, we defined extracellular factors that influence the formation of a spectrum of alternative self-propagating amyloid structures of the Sup35 protein, called [PSI(+)] variants. Strikingly, exposure to specific stressful environments dramatically altered the variants of [PSI(+)] that formed de novo. Additionally, we found that stress also influenced the association between the [PSI(+)] and [RNQ(+)] prions in a way that it superceded their typical relationship. Furthermore, changing the growth environment modified both the biochemical properties and [PSI(+)]-inducing capabilities of the [RNQ(+)] template. These data suggest that the cellular environment contributes to both the generation and the selective propagation of specific amyloid structures, providing insight into a key feature that impacts phenotypic diversity in yeast and the cross-species transmission barriers characteristic of prion diseases.
Collapse
Affiliation(s)
- Laura Westergard
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | | |
Collapse
|
11
|
Chernova TA, Wilkinson KD, Chernoff YO. Physiological and environmental control of yeast prions. FEMS Microbiol Rev 2013; 38:326-44. [PMID: 24236638 DOI: 10.1111/1574-6976.12053] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 11/08/2013] [Accepted: 11/10/2013] [Indexed: 11/30/2022] Open
Abstract
Prions are self-perpetuating protein isoforms that cause fatal and incurable neurodegenerative disease in mammals. Recent evidence indicates that a majority of human proteins involved in amyloid and neural inclusion disorders possess at least some prion properties. In lower eukaryotes, such as yeast, prions act as epigenetic elements, which increase phenotypic diversity by altering a range of cellular processes. While some yeast prions are clearly pathogenic, it is also postulated that prion formation could be beneficial in variable environmental conditions. Yeast and mammalian prions have similar molecular properties. Crucial cellular factors and conditions influencing prion formation and propagation were uncovered in the yeast models. Stress-related chaperones, protein quality control deposits, degradation pathways, and cytoskeletal networks control prion formation and propagation in yeast. Environmental stresses trigger prion formation and loss, supposedly acting via influencing intracellular concentrations of the prion-inducing proteins, and/or by localizing prionogenic proteins to the prion induction sites via heterologous ancillary helpers. Physiological and environmental modulation of yeast prions points to new opportunities for pharmacological intervention and/or prophylactic measures targeting general cellular systems rather than the properties of individual amyloids and prions.
Collapse
Affiliation(s)
- Tatiana A Chernova
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | | | | |
Collapse
|
12
|
Affiliation(s)
- Liming Li
- Department of Molecular Pharmacology and Biological Chemistry, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail:
| | | |
Collapse
|
13
|
Lancaster DL, Dobson CM, Rachubinski RA. Chaperone proteins select and maintain [PIN+] prion conformations in Saccharomyces cerevisiae. J Biol Chem 2012; 288:1266-76. [PMID: 23148221 DOI: 10.1074/jbc.m112.377564] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Prions are proteins that can adopt different infectious conformations known as "strains" or "variants," each with a distinct, epigenetically inheritable phenotype. Mechanisms by which prion variants are determined remain unclear. Here we use the Saccharomyces cerevisiae prion Rnq1p/[PIN(+)] as a model to investigate the effects of chaperone proteins upon prion variant determination. We show that deletion of specific chaperone genes alters [PIN(+)] variant phenotypes, including [PSI(+)] induction efficiency, Rnq1p aggregate morphology/size and variant dominance. Mating assays demonstrate that gene deletion-induced phenotypic changes are stably inherited in a non-Mendelian manner even after restoration of the deleted gene, confirming that they are due to a bona fide change in the [PIN(+)] variant. Together, our results demonstrate a role for chaperones in regulating the prion variant complement of a cell.
Collapse
Affiliation(s)
- David L Lancaster
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
| | | | | |
Collapse
|
14
|
Abstract
The concept of a prion as an infectious self-propagating protein isoform was initially proposed to explain certain mammalian diseases. It is now clear that yeast also has heritable elements transmitted via protein. Indeed, the "protein only" model of prion transmission was first proven using a yeast prion. Typically, known prions are ordered cross-β aggregates (amyloids). Recently, there has been an explosion in the number of recognized prions in yeast. Yeast continues to lead the way in understanding cellular control of prion propagation, prion structure, mechanisms of de novo prion formation, specificity of prion transmission, and the biological roles of prions. This review summarizes what has been learned from yeast prions.
Collapse
Affiliation(s)
- Susan W Liebman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA.
| | | |
Collapse
|
15
|
Manogaran AL, Hong JY, Hufana J, Tyedmers J, Lindquist S, Liebman SW. Prion formation and polyglutamine aggregation are controlled by two classes of genes. PLoS Genet 2011; 7:e1001386. [PMID: 21625618 PMCID: PMC3098188 DOI: 10.1371/journal.pgen.1001386] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 04/14/2011] [Indexed: 11/20/2022] Open
Abstract
Prions are self-perpetuating aggregated proteins that are not limited to mammalian systems but also exist in lower eukaryotes including yeast. While much work has focused around chaperones involved in prion maintenance, including Hsp104, little is known about factors involved in the appearance of prions. De novo appearance of the [PSI+] prion, which is the aggregated form of the Sup35 protein, is dramatically enhanced by transient overexpression of SUP35 in the presence of the prion form of the Rnq1 protein, [PIN+]. When fused to GFP and overexpressed in [ps−] [PIN+] cells, Sup35 forms fluorescent rings, and cells with these rings bud off [PSI+] daughters. We investigated the effects of over 400 gene deletions on this de novo induction of [PSI+]. Two classes of gene deletions were identified. Class I deletions (bug1Δ, bem1Δ, arf1Δ, and hog1Δ) reduced the efficiency of [PSI+] induction, but formed rings normally. Class II deletions (las17Δ, vps5Δ, and sac6Δ) inhibited both [PSI+] induction and ring formation. Furthermore, class II deletions reduced, while class I deletions enhanced, toxicity associated with the expanded glutamine repeats of the huntingtin protein exon 1 that causes Huntington's disease. This suggests that prion formation and polyglutamine aggregation involve a multi-phase process that can be inhibited at different steps. Certain proteins that exist in functional unaggregated conformers can also form self-perpetuating infectious aggregates called prions. Here we investigate factors involved in the initial switch to the prion form. De novo appearance of the [PSI+] prion, which is the aggregated form of the Sup35 protein, is dramatically enhanced by overexpression of the SUP35 gene in the presence of the prion form of the Rnq1 protein, [PIN+]. When tagged with green fluorescent protein and transiently overexpressed in [psi−] [PIN+] cells, Sup35 forms fluorescent rings, and cells with these rings give rise to daughter cells that are [PSI+]. Here, we investigate factors required for this induction of [PSI+]. Analyses of over 400 gene deletions revealed two classes that reduce [PSI+] induction: one class forms fluorescent rings normally, and the other does not. Interestingly, the former class enhanced, while the latter class reduced, toxicity associated with the expanded polyglutamine repeats of the huntingtin protein exon 1 that causes Huntington's disease. These results suggest that prion formation and polyglutamine aggregation involve a multi-phase process that can be inhibited at different steps.
Collapse
Affiliation(s)
- Anita L. Manogaran
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States of America
| | - Joo Y. Hong
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Joan Hufana
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Jens Tyedmers
- Zentrum fuer Molekulare Biologie Heidelberg, DKFZ-ZMBH-Alliance, Universitaet Heidelberg, Heidelberg, Germany
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Susan Lindquist
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Susan W. Liebman
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
| |
Collapse
|
16
|
Newnam GP, Birchmore JL, Chernoff YO. Destabilization and recovery of a yeast prion after mild heat shock. J Mol Biol 2011; 408:432-48. [PMID: 21392508 DOI: 10.1016/j.jmb.2011.02.034] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 02/03/2011] [Accepted: 02/09/2011] [Indexed: 11/28/2022]
Abstract
Yeast prion [PSI(+)] is a self-perpetuating amyloid of the translational termination factor Sup35. Although [PSI(+)] propagation is modulated by heat shock proteins (Hsps), high temperature was previously reported to have little or no effect on [PSI(+)]. Our results show that short-term exposure of exponentially growing yeast culture to mild heat shock, followed by immediate resumption of growth, leads to [PSI(+)] destabilization, sometimes persisting for several cell divisions after heat shock. Prion loss occurring in the first division after heat shock is preferentially detected in a daughter cell, indicating the impairment of prion segregation that results in asymmetric prion distribution between a mother cell and a bud. Longer heat shock or prolonged incubation in the absence of nutrients after heat shock led to [PSI(+)] recovery. Both prion destabilization and recovery during heat shock depend on protein synthesis. Maximal prion destabilization coincides with maximal imbalance between Hsp104 and other Hsps such as Hsp70-Ssa. Deletions of individual SSA genes increase prion destabilization and/or counteract recovery. The dynamics of prion aggregation during destabilization and recovery are consistent with the notion that efficient prion fragmentation and segregation require a proper balance between Hsp104 and other (e.g., Hsp70-Ssa) chaperones. In contrast to heat shock, [PSI(+)] destabilization by osmotic stressors does not always depend on cell proliferation and/or protein synthesis, indicating that different stresses may impact the prion via different mechanisms. Our data demonstrate that heat stress causes asymmetric prion distribution in a cell division and confirm that the effects of Hsps on prions are physiologically relevant.
Collapse
Affiliation(s)
- Gary P Newnam
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA
| | | | | |
Collapse
|
17
|
Du Z, Crow ET, Kang HS, Li L. Distinct subregions of Swi1 manifest striking differences in prion transmission and SWI/SNF function. Mol Cell Biol 2010; 30:4644-55. [PMID: 20679490 PMCID: PMC2950522 DOI: 10.1128/mcb.00225-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 03/18/2010] [Accepted: 07/18/2010] [Indexed: 11/20/2022] Open
Abstract
We have recently reported that the yeast chromatin-remodeling factor Swi1 can exist as a prion, [SWI(+)], demonstrating a link between prionogenesis and global transcriptional regulation. To shed light on how the Swi1 conformational switch influences Swi1 function and to define the sequence and structural requirements for [SWI(+)] formation and propagation, we functionally dissected the Swi1 molecule. We show here that the [SWI(+)] prion features are solely attributable to the first 327 amino acid residues (N), a region that is asparagine rich. N was aggregated in [SWI(+)] cells but diffuse in [swi(-)] cells; chromosomal deletion of the N-coding region resulted in [SWI(+)] loss, and recombinant N peptide was able to form infectious amyloid fibers in vitro, enabling [SWI(+)] de novo formation through a simple transformation. Although the glutamine-rich middle region (Q) was not sufficient to aggregate in [SWI(+)] cells or essential for SWI/SNF function, it significantly modified the Swi1 aggregation pattern and Swi1 function. We also show that excessive Swi1 incurred Li(+)/Na(+) sensitivity and that the N/Q regions are important for this gain of sensitivity. Taken together, our results provide the final proof of "protein-only" transmission of [SWI(+)] and demonstrate that the widely distributed "dispensable" glutamine/asparagine-rich regions/motifs might have important and divergent biological functions.
Collapse
Affiliation(s)
- Zhiqiang Du
- Department of Molecular Pharmacology and Biological Chemistry, Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Emily T. Crow
- Department of Molecular Pharmacology and Biological Chemistry, Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Hyun Seok Kang
- Department of Molecular Pharmacology and Biological Chemistry, Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Liming Li
- Department of Molecular Pharmacology and Biological Chemistry, Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| |
Collapse
|
18
|
Neef DW, Turski ML, Thiele DJ. Modulation of heat shock transcription factor 1 as a therapeutic target for small molecule intervention in neurodegenerative disease. PLoS Biol 2010; 8:e1000291. [PMID: 20098725 PMCID: PMC2808216 DOI: 10.1371/journal.pbio.1000291] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 12/11/2009] [Indexed: 11/18/2022] Open
Abstract
A yeast-based small molecule screen identifies a novel activator of human HSF1 and protein chaperone expression and which appears to alleviate the toxicity of protein misfolding diseases. Neurodegenerative diseases such as Huntington disease are devastating disorders with no therapeutic approaches to ameliorate the underlying protein misfolding defect inherent to poly-glutamine (polyQ) proteins. Given the mounting evidence that elevated levels of protein chaperones suppress polyQ protein misfolding, the master regulator of protein chaperone gene transcription, HSF1, is an attractive target for small molecule intervention. We describe a humanized yeast-based high-throughput screen to identify small molecule activators of human HSF1. This screen is insensitive to previously characterized activators of the heat shock response that have undesirable proteotoxic activity or that inhibit Hsp90, the central chaperone for cellular signaling and proliferation. A molecule identified in this screen, HSF1A, is structurally distinct from other characterized small molecule human HSF1 activators, activates HSF1 in mammalian and fly cells, elevates protein chaperone expression, ameliorates protein misfolding and cell death in polyQ-expressing neuronal precursor cells and protects against cytotoxicity in a fly model of polyQ-mediated neurodegeneration. In addition, we show that HSF1A interacts with components of the TRiC/CCT complex, suggesting a potentially novel regulatory role for this complex in modulating HSF1 activity. These studies describe a novel approach for the identification of new classes of pharmacological interventions for protein misfolding that underlies devastating neurodegenerative disease. The misfolding of proteins into a toxic state contributes to a variety of neurodegenerative diseases such as Huntington, Alzheimer, and Parkinson disease. Although no known cure exists for these afflictions, many studies have shown that increasing the levels of protein chaperones, proteins that assist in the correct folding of other proteins, can suppress the neurotoxicity of the misfolded proteins. As such, increasing the cellular concentration of protein chaperones might serve as a powerful therapeutic approach in treating protein misfolding diseases. Because the levels of protein chaperones in the cell are primarily controlled by the heat shock transcription factor 1 [HSF1], we have designed and implemented a pharmacological screen to identify small molecules that can promote human HSF1 activation and increase the expression of protein chaperones. Through these studies, we have identified HSF1A, a molecule capable of activating human HSF1, increasing the levels of protein chaperones and alleviating the toxicity of misfolded proteins in both cell culture as well as fruit fly models of neurodegenerative disease.
Collapse
Affiliation(s)
- Daniel W. Neef
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Michelle L. Turski
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Dennis J. Thiele
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
19
|
Sharma D, Martineau CN, Le Dall MT, Reidy M, Masison DC, Kabani M. Function of SSA subfamily of Hsp70 within and across species varies widely in complementing Saccharomyces cerevisiae cell growth and prion propagation. PLoS One 2009; 4:e6644. [PMID: 19680550 PMCID: PMC2721632 DOI: 10.1371/journal.pone.0006644] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Accepted: 07/15/2009] [Indexed: 11/23/2022] Open
Abstract
Background The cytosol of most eukaryotic cells contains multiple highly conserved Hsp70 orthologs that differ mainly by their spatio-temporal expression patterns. Hsp70s play essential roles in protein folding, transport or degradation, and are major players of cellular quality control processes. However, while several reports suggest that specialized functions of Hsp70 orthologs were selected through evolution, few studies addressed systematically this issue. Methodology/Principal Findings We compared the ability of Ssa1p-Ssa4p from Saccharomyces cerevisiae and Ssa5p-Ssa8p from the evolutionary distant yeast Yarrowia lipolytica to perform Hsp70-dependent tasks when expressed as the sole Hsp70 for S. cerevisiae in vivo. We show that Hsp70 isoforms (i) supported yeast viability yet with markedly different growth rates, (ii) influenced the propagation and stability of the [PSI+] and [URE3] prions, but iii) did not significantly affect the proteasomal degradation rate of CFTR. Additionally, we show that individual Hsp70 orthologs did not induce the formation of different prion strains, but rather influenced the aggregation properties of Sup35 in vivo. Finally, we show that [URE3] curing by the overexpression of Ydj1p is Hsp70-isoform dependent. Conclusion/Significance Despite very high homology and overlapping functions, the different Hsp70 orthologs have evolved to possess distinct activities that are required to cope with different types of substrates or stress situations. Yeast prions provide a very sensitive model to uncover this functional specialization and to explore the intricate network of chaperone/co-chaperone/substrates interactions.
Collapse
Affiliation(s)
- Deepak Sharma
- Laboratory of Biochemistry and Genetics, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Céline N. Martineau
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
| | - Marie-Thérèse Le Dall
- Laboratoire de Microbiologie et Génétique Moléculaire, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, AgroParisTech, Thiverval-Grignon, France
| | - Michael Reidy
- Laboratory of Biochemistry and Genetics, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Daniel C. Masison
- Laboratory of Biochemistry and Genetics, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (DCM); (MK)
| | - Mehdi Kabani
- Laboratoire d’Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
- * E-mail: (DCM); (MK)
| |
Collapse
|
20
|
Bardill JP, Dulle JE, Fisher JR, True HL. Requirements of Hsp104p activity and Sis1p binding for propagation of the [RNQ(+)] prion. Prion 2009; 3:151-60. [PMID: 19770577 DOI: 10.4161/pri.3.3.9662] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The formation and maintenance of prions in the yeast Saccharomyces cerevisiae is highly regulated by the cellular chaperone machinery. The most important player in this regulation is Hsp104p, which is required for the maintenance of all known prions. The requirements for other chaperones, such as members of the Hsp40 or Hsp70 families, vary with each individual prion. [RNQ(+)] cells do not have a phenotype that is amenable to genetic screens to identify cellular factors important in prion propagation. Therefore, we used a chimeric construct that reports the [RNQ(+)] status of cells to perform a screen for mutants that are unable to maintain [RNQ(+)]. We found eight separate mutations in Hsp104p that caused [RNQ(+)] cells to become [rnq(-)]. These mutations also caused the loss of the [PSI(+)] prion. The expression of one of these mutants, Hsp104p-E190K, showed differential loss of the [RNQ(+)] and [PSI(+)] prions in the presence of wild type Hsp104p. Hsp104p-E190K inefficiently propagated [RNQ(+)] and was unable to maintain [PSI(+)]. The mutant was unable to act on other in vivo substrates, as strains carrying it were not thermotolerant. Purified recombinant Hsp104p-E190K showed a reduced level of ATP hydrolysis as compared to wild type protein. This is likely the cause of both prion loss and lack of in vivo function. Furthermore, it suggests that [RNQ(+)] requires less Hsp104p activity to maintain transmissible protein aggregates than Sup35p. Additionally, we show that the L94A mutation in Rnq1p, which reduces its interaction with Sis1p, prevents Rnq1p from maintaining a prion and inducing [PSI(+)].
Collapse
Affiliation(s)
- J Patrick Bardill
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, MO, USA
| | | | | | | |
Collapse
|
21
|
Pezza JA, Langseth SX, Raupp Yamamoto R, Doris SM, Ulin SP, Salomon AR, Serio TR. The NatA acetyltransferase couples Sup35 prion complexes to the [PSI+] phenotype. Mol Biol Cell 2008; 20:1068-80. [PMID: 19073888 DOI: 10.1091/mbc.e08-04-0436] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Protein-only (prion) epigenetic elements confer unique phenotypes by adopting alternate conformations that specify new traits. Given the conformational flexibility of prion proteins, protein-only inheritance requires efficient self-replication of the underlying conformation. To explore the cellular regulation of conformational self-replication and its phenotypic effects, we analyzed genetic interactions between [PSI(+)], a prion form of the S. cerevisiae Sup35 protein (Sup35([PSI+])), and the three N(alpha)-acetyltransferases, NatA, NatB, and NatC, which collectively modify approximately 50% of yeast proteins. Although prion propagation proceeds normally in the absence of NatB or NatC, the [PSI(+)] phenotype is reversed in strains lacking NatA. Despite this change in phenotype, [PSI(+)] NatA mutants continue to propagate heritable Sup35([PSI+]). This uncoupling of protein state and phenotype does not arise through a decrease in the number or activity of prion templates (propagons) or through an increase in soluble Sup35. Rather, NatA null strains are specifically impaired in establishing the translation termination defect that normally accompanies Sup35 incorporation into prion complexes. The NatA effect cannot be explained by the modification of known components of the [PSI(+)] prion cycle including Sup35; thus, novel acetylated cellular factors must act to establish and maintain the tight link between Sup35([PSI+]) complexes and their phenotypic effects.
Collapse
Affiliation(s)
- John A Pezza
- Brown University, Department of Molecular Biology, Cell Biology, and Biochemistry, Providence, RI 02912, USA
| | | | | | | | | | | | | |
Collapse
|
22
|
Abstract
Prions represent an unusual structural form of a protein that is 'infectious'. In mammals, prions are associated with fatal neurodegenerative diseases such as CJD (Creutzfeldt-Jakob disease), while in fungi they act as novel epigenetic regulators of phenotype. Even though most of the human prion diseases arise spontaneously, we still know remarkably little about how infectious prions form de novo. The [PSI+] prion of the yeast Saccharomyces cerevisiae provides a highly tractable model in which to explore the underlying mechanism of de novo prion formation, in particular identifying key cis- and trans-acting factors. Most significantly, the de novo formation of [PSI+] requires the presence of a second prion called [PIN+], which is typically the prion form of Rnq1p, a protein rich in glutamine and aspartic acid residues. The molecular mechanism by which the [PIN(+)] prion facilitates de novo [PSI+] formation is not fully established, but most probably involves some form of cross-seeding. A number of other cellular factors, in particular chaperones of the Hsp70 (heat-shock protein 70) family, are known to modify the frequency of de novo prion formation in yeast.
Collapse
|
23
|
Newly identified prion linked to the chromatin-remodeling factor Swi1 in Saccharomyces cerevisiae. Nat Genet 2008; 40:460-5. [PMID: 18362884 DOI: 10.1038/ng.112] [Citation(s) in RCA: 254] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 02/14/2008] [Indexed: 11/08/2022]
Abstract
SWI/SNF, an evolutionarily conserved ATP-dependent chromatin-remodeling complex, has an important role in transcriptional regulation. In Saccharomyces cerevisiae, SWI/SNF regulates the expression of approximately 6% of total genes through activation or repression. Swi1, a subunit of SWI/SNF, contains an N-terminal region rich in glutamine and asparagine, a notable feature shared by all characterized yeast prions--a group of unique proteins capable of self-perpetuating changes in conformation and function. Here we provide evidence that Swi1 can become a prion, [SWI+]. Swi1 aggregates in [SWI+] cells but not in nonprion cells. Cells bearing [SWI+] show a partial loss-of-function phenotype of SWI/SNF. [SW+] can be eliminated by guanidine hydrochloride treatment, HSP104 deletion or loss of Swi1. Moreover, we show [SWI+] is dominantly and cytoplasmically transmitted. Our findings reveal a novel mechanism of 'protein-only' inheritance that results in modification of chromatin-remodeling and, ultimately, global gene regulation.
Collapse
|
24
|
Bagriantsev SN, Gracheva EO, Richmond JE, Liebman SW. Variant-specific [PSI+] infection is transmitted by Sup35 polymers within [PSI+] aggregates with heterogeneous protein composition. Mol Biol Cell 2008; 19:2433-43. [PMID: 18353968 DOI: 10.1091/mbc.e08-01-0078] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The [PSI(+)] prion is the aggregated self-propagating form of the Sup35 protein from the yeast Saccharomyces cerevisiae. Aggregates of Sup35 in [PSI(+)] cells exist in different heritable conformations, called "variants," and they are composed of detergent-resistant Sup35 polymers, which may be closely associated with themselves, other proteins, or both. Here, we report that disassembly of the aggregates into individual Sup35 polymers and non-Sup35 components increases their infectivity while retaining their variant specificity, showing that variant-specific [PSI(+)] infection can be transmitted by Sup35 polymers alone. Morphological analysis revealed that Sup35 isolated from [PSI(+)] yeast has the appearance of short barrels, and bundles, which seem to be composed of barrels. We show that the major components of two different variants of [PSI(+)] are interacting infectious Sup35 polymers and Ssa1/2. Using a candidate approach, we detected Hsp104, Ssb1/2, Sis1, Sse1, Ydj1, and Sla2 among minor components of the aggregates. We demonstrate that Ssa1/2 efficiently binds to the prion domain of Sup35 in [PSI(+)] cells, but that it interacts poorly with the nonaggregated Sup35 found in [psi(-)] cells. Hsp104, Sis1, and Sse1 interact preferentially with the prion versus nonprion form of Sup35, whereas Sla2 and Ssb1/2 interact with both forms of Sup35 with similar efficiency.
Collapse
|
25
|
The role of Sse1 in the de novo formation and variant determination of the [PSI+] prion. Genetics 2008; 177:1583-93. [PMID: 18039878 DOI: 10.1534/genetics.107.077982] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Yeast prions are a group of non-Mendelian genetic elements transmitted as altered and self-propagating conformations. Extensive studies in the last decade have provided valuable information on the mechanisms responsible for yeast prion propagation. How yeast prions are formed de novo and what cellular factors are required for determining prion "strains" or variants--a single polypeptide capable of existing in multiple conformations to result in distinct heritable phenotypes--continue to defy our understanding. We report here that Sse1, the yeast ortholog of the mammalian heat-shock protein 110 (Hsp110) and a nucleotide exchange factor for Hsp70 proteins, plays an important role in regulating [PSI+] de novo formation and variant determination. Overproduction of the Sse1 chaperone dramatically enhanced [PSI+] formation whereas deletion of SSE1 severely inhibited it. Only an unstable weak [PSI+] variant was formed in SSE1 disrupted cells whereas [PSI+] variants ranging from very strong to very weak were formed in isogenic wild-type cells under identical conditions. Thus, Sse1 is essential for the generation of multiple [PSI+] variants. Mutational analysis further demonstrated that the physical association of Sse1 with Hsp70 but not the ATP hydrolysis activity of Sse1 is required for the formation of multiple [PSI+] variants. Our findings establish a novel role for Sse1 in [PSI+] de novo formation and variant determination, implying that the mammalian Hsp110 may likewise be involved in the etiology of protein-folding diseases.
Collapse
|
26
|
Chernoff YO. Stress and prions: lessons from the yeast model. FEBS Lett 2007; 581:3695-701. [PMID: 17509571 PMCID: PMC2695654 DOI: 10.1016/j.febslet.2007.04.075] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 04/20/2007] [Accepted: 04/21/2007] [Indexed: 10/23/2022]
Abstract
Yeast self-perpetuating amyloids (prions) provide a convenient model for studying the cellular control of highly ordered aggregates involved in mammalian protein assembly disorders. The very ability of an amyloid to propagate a prion state in yeast is determined by its interactions with the stress-inducible chaperone Hsp104. Prion formation and propagation are also influenced by other stress-related chaperones (Hsp70 and Hsp40), and by alterations of the protein trafficking and degradation networks. Some stress conditions induce prion formation or loss. It is proposed that prions arise as byproducts of the reversible assembly of highly ordered complexes, protecting certain proteins during unfavorable conditions.
Collapse
Affiliation(s)
- Yury O Chernoff
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA.
| |
Collapse
|
27
|
Current awareness on yeast. Yeast 2007. [DOI: 10.1002/yea.1322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
|