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1.
Nat Struct Biol ; 8(11): 958-62, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11685242

ABSTRACT

The [PSI(+)] factor of Saccharomyces cerevisiae is a protein-based genetic element (prion) comprised of a heritable altered conformation of the cytosolic translation termination factor Sup35p. In vitro, the prion-determining region (NM) of Sup35p undergoes conformational conversion from a highly flexible soluble state to structured amyloid fibers, with a rate that is greatly accelerated by preformed NM fiber nuclei. Nucleated conformational conversion is the molecular basis of the genetic inheritance of [PSI(+)] and provides a new model for studying amyloidogenesis. Here we investigate the importance of structure and structural flexibility in soluble NM. Elevated temperatures, chemical chaperones and certain mutations in NM increase or change its structural content and inhibit or enhance nucleated conformational conversion. We propose that the structural flexibility of NM is particularly suited to allowing heritable protein-based changes in cellular behavior.


Subject(s)
Amyloidosis , Fungal Proteins/chemistry , Fungal Proteins/metabolism , Prions/chemistry , Prions/metabolism , Saccharomyces cerevisiae , Amyloidosis/genetics , Fungal Proteins/genetics , Molecular Chaperones/genetics , Mutation/genetics , Oligopeptides/chemistry , Oligopeptides/genetics , Oligopeptides/metabolism , Osmolar Concentration , Peptide Termination Factors , Pliability , Prions/genetics , Protein Biosynthesis , Protein Denaturation , Protein Structure, Quaternary , Protein Structure, Secondary , Repetitive Sequences, Amino Acid/genetics , Saccharomyces cerevisiae/chemistry , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolism , Solubility , Temperature
2.
Biochem Soc Symp ; (68): 35-43, 2001.
Article in English | MEDLINE | ID: mdl-11573346

ABSTRACT

Recently, a novel mode of inheritance has been described in the yeast Saccharomyces cerevisiae. The mechanism is based on the prion hypothesis, which posits that self-perpetuating changes in the conformation of single protein, PrP, underlie the severe neurodegeneration associated with the transmissible spongiform enchephalopathies in mammals. In yeast, two prions, [URE3] and [PSI+], have been identified, but these factors confer unique phenotypes rather than disease to the organism. In each case, the prion-associated phenotype has been linked to alternative conformations of the Ure2 and Sup35 proteins. Remarkably, Ure2 and Sup35 proteins existing in the alternative conformations have the unique capacity to transmit this physical state to the newly synthesized protein in vivo. Thus, a mechanism exists to ensure replication of the conformational information that underlies protein-only inheritance. We have characterized the mechanism by which Sup35 conformational information is replicated in vitro. The assembly of amyloid fibres by a region of Sup35 encompassing the N-terminal 254 amino acids faithfully recapitulates the in vivo propagation of [PSI+]. Mutations that alter [PSI+] inheritance in vivo change the kinetics of amyloid assembly in vitro in a complementary fashion, and lysates from [PSI+] cells, but not [psi-] cells, accelerate assembly in vitro. Using this system we propose a mechanism by which the alternative conformation of Sup35 is adopted by an unstructured oilgomeric intermediate at the time of assembly.


Subject(s)
Fungal Proteins/chemistry , Fungal Proteins/genetics , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/chemistry , Saccharomyces cerevisiae/genetics , Amyloid/chemistry , Models, Molecular , Peptide Termination Factors , Prions/chemistry , Prions/genetics , Protein Conformation , Protein Folding , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics
3.
Adv Protein Chem ; 57: 335-66, 2001.
Article in English | MEDLINE | ID: mdl-11447696

ABSTRACT

Biochemical characterization of the yeast prions has revealed many similarities with the mammalian amyloidogenic proteins. The ease of generating in vivo mutations in yeast and the developing in vitro models for [PSI+] and [URE3] circumvent many of the difficulties of studying the proteins linked to the mammalian amyloidoses. Future work especially aimed at understanding the molecular role of chaperone proteins in regulating conversion as well as the early steps in de novo formation of the prion state in yeast will likely provide invaluable lessons that may be more broadly applicable to related processes in higher eukaryotes. It is important to remember, however, that there are clear distinctions between disease states associated with amyloidogenesis and the epigenetic modulation of protein function by self-perpetuating conformational conversions. Amyloid formation is detrimental to mammals and is likely selected against, providing a possible explanation for the late onset of these disorders (Lansbury, 1999). In contrast, the known yeast prions are compatible with normal growth and, if beneficial to the organism, may be subject to evolutionary pressures that ultimately maximize transmission. In the prion proteins examined to date, distinct domains are responsible for normal function and for the conformational switches producing a prion conversion of that function. Recent work has demonstrated that the prion domains are both modular and transferable to other proteins on which they can confer a heritable epigenetic alteration of function (Edskes et al., 1999; Li and Lindquist, 2000; Patino et al., 1996; Santoso et al., 2000; Sondheimer and Lindquist, 2000). That is, prion domains need not coevolve with particular functional domains but might be moved from one protein to another during evolution. Such processes may be widely used in biology. Mechanistic studies of [PSI+] and [URE3] replication are sure to lay a foundation of knowledge for understanding a host of nonconventional genetic elements that currently remain elusive.


Subject(s)
Fungal Proteins/physiology , Molecular Chaperones/physiology , Prions/physiology , Saccharomyces cerevisiae Proteins , Amino Acid Sequence , Fungal Proteins/chemistry , In Vitro Techniques , Molecular Sequence Data , Peptide Termination Factors , Prions/chemistry
4.
Curr Biol ; 11(5): 366-9, 2001 Mar 06.
Article in English | MEDLINE | ID: mdl-11267875

ABSTRACT

The polymerization of many amyloids is a two-stage process initiated by the formation of a seeding nucleus or protofibril. Soluble protein then assembles with these nuclei to form amyloid fibers. Whether fiber growth is bidirectional or unidirectional has been determined for two amyloids. In these cases, bidirectional growth was established by time lapse atomic-force microscopy. Here, we investigated the growth of amyloid fibers formed by NM, the prion-determining region of the yeast protein Sup35p. The conformational changes in NM that lead to amyloid formation in vitro serve as a model for the self-perpetuating conformational changes in Sup35p that allow this protein to serve as an epigenetic element of inheritance in vivo. To assess the directionality of fiber growth, we genetically engineered a mutant of NM so that it contained an accessible cysteine residue that was easily labeled after fiber formation. The mutant protein assembled in vitro with kinetics indistinguishable from those of the wild-type protein and propagated the heritable genetic trait [PSI(+)] with the same fidelity. In reactions nucleated with prelabeled fibers, unlabeled protein assembled at both ends. Thus, NM fiber growth is bidirectional.


Subject(s)
Fungal Proteins/metabolism , Prions/metabolism , Saccharomyces cerevisiae Proteins , Peptide Termination Factors , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae/ultrastructure
5.
Proc Natl Acad Sci U S A ; 98(3): 914-9, 2001 Jan 30.
Article in English | MEDLINE | ID: mdl-11158570

ABSTRACT

Point mutations in either of the two nucleotide-binding domains (NBD) of Hsp104 (NBD1 and NBD2) eliminate its thermotolerance function in vivo. In vitro, NBD1 mutations virtually eliminate ATP hydrolysis with little effect on hexamerization; analogous NBD2 mutations reduce ATPase activity and severely impair hexamerization. We report that high protein concentrations overcome the assembly defects of NBD2 mutants and increase ATP hydrolysis severalfold, changing V(max) with little effect on K(m). In a complementary fashion, the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate inhibits hexamerization of wild-type (WT) Hsp104, lowering V(max) with little effect on K(m). ATP hydrolysis exhibits a Hill coefficient between 1.5 and 2, indicating that it is influenced by cooperative subunit interactions. To further analyze the effects of subunit interactions on Hsp104, we assessed the effects of mutant Hsp104 proteins on WT Hsp104 activities. An NBD1 mutant that hexamerizes but does not hydrolyze ATP reduces the ATPase activity of WT Hsp104 in vitro. In vivo, this mutant is not toxic but specifically inhibits the thermotolerance function of WT Hsp104. Thus, interactions between subunits influence the ATPase activity of Hsp104, play a vital role in its biological functions, and provide a mechanism for conditionally inactivating Hsp104 function in vivo.


Subject(s)
Adenosine Triphosphate/metabolism , Heat-Shock Proteins/chemistry , Heat-Shock Proteins/metabolism , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/metabolism , Adenosine Triphosphatases/chemistry , Adenosine Triphosphatases/metabolism , Amino Acid Substitution , Binding Sites , Estradiol/pharmacology , Fungal Proteins/chemistry , Fungal Proteins/metabolism , Kinetics , Mutagenesis, Site-Directed , Point Mutation , Protein Subunits , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/growth & development
7.
Nature ; 407(6803): 477-83, 2000 Sep 28.
Article in English | MEDLINE | ID: mdl-11028992

ABSTRACT

A major enigma in evolutionary biology is that new forms or functions often require the concerted effects of several independent genetic changes. It is unclear how such changes might accumulate when they are likely to be deleterious individually and be lost by selective pressure. The Saccharomyces cerevisiae prion [PSI+] is an epigenetic modifier of the fidelity of translation termination, but its impact on yeast biology has been unclear. Here we show that [PSI+] provides the means to uncover hidden genetic variation and produce new heritable phenotypes. Moreover, in each of the seven genetic backgrounds tested, the constellation of phenotypes produced was unique. We propose that the epigenetic and metastable nature of [PSI+] inheritance allows yeast cells to exploit pre-existing genetic variation to thrive in fluctuating environments. Further, the capacity of [PSI+] to convert previously neutral genetic variation to a non-neutral state may facilitate the evolution of new traits.


Subject(s)
Fungal Proteins/genetics , Genetic Variation , Prions/genetics , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/genetics , Anti-Bacterial Agents/pharmacology , Binding Sites , Ethanol/pharmacology , Fungal Proteins/physiology , Peptide Termination Factors , Phenotype , Prions/physiology , Protein Biosynthesis/drug effects , Saccharomyces cerevisiae/growth & development
8.
Science ; 289(5483): 1317-21, 2000 Aug 25.
Article in English | MEDLINE | ID: mdl-10958771

ABSTRACT

Prion proteins can serve as genetic elements by adopting distinct physical and functional states that are self-perpetuating and heritable. The critical region of one prion protein, Sup35, is initially unstructured in solution and then forms self-seeded amyloid fibers. We examined in vitro the mechanism by which this state is attained and replicated. Structurally fluid oligomeric complexes appear to be crucial intermediates in de novo amyloid nucleus formation. Rapid assembly ensues when these complexes conformationally convert upon association with nuclei. This model for replicating protein-based genetic information, nucleated conformational conversion, may be applicable to other protein assembly processes.


Subject(s)
Amyloid/chemistry , Fungal Proteins/chemistry , Prions/chemistry , Saccharomyces cerevisiae Proteins , Biopolymers/chemistry , Centrifugation, Density Gradient , Circular Dichroism , Electrophoresis, Polyacrylamide Gel , Endopeptidases/metabolism , Fungal Proteins/metabolism , Fungal Proteins/ultrastructure , Kinetics , Light , Micelles , Microscopy, Atomic Force , Microscopy, Electron , Models, Chemical , Peptide Termination Factors , Prions/metabolism , Prions/ultrastructure , Protein Conformation , Protein Folding , Scattering, Radiation , Solubility , Sonication
9.
Trends Cell Biol ; 10(3): 98-105, 2000 Mar.
Article in English | MEDLINE | ID: mdl-10675903

ABSTRACT

Recent work suggests that two unrelated phenotypes, [PSI+] and [URE3], in the yeast Saccharomyces cerevisiae are transmitted by non-covalent changes in the physical states of their protein determinants, Sup35p and Ure2p, rather than by changes in the genes that encode these proteins. The mechanism by which alternative protein states are self-propagating is the key to understanding how proteins function as elements of epigenetic inheritance. Here, we focus on recent molecular-genetic analysis of the inheritance of the [PSI+] factor of S. cerevisiae. Insights into this process might be extendable to a group of mammalian diseases (the amyloidoses), which are also believed to be a manifestation of self-perpetuating changes in protein conformation.


Subject(s)
Extrachromosomal Inheritance/genetics , Fungal Proteins/metabolism , Repressor Proteins/metabolism , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism , Fungal Proteins/genetics , Glutathione Peroxidase , HSP70 Heat-Shock Proteins/metabolism , Heat-Shock Proteins/metabolism , Peptide Termination Factors , Phenotype , Prions/genetics , Prions/metabolism , Protein Binding/genetics , Protein Biosynthesis
10.
Annu Rev Cell Dev Biol ; 15: 661-703, 1999.
Article in English | MEDLINE | ID: mdl-10611975

ABSTRACT

The [PSI+] factor of the yeast Saccharomyces cerevisiae is an epigenetic regulator of translation termination. More than three decades ago, genetic analysis of the transmission of [PSI+] revealed a complex and often contradictory series of observations. However, many of these discrepancies may now be reconciled by a revolutionary hypothesis: protein conformation-based inheritance (the prion hypothesis). This model predicts that a single protein can stably exist in at least two distinct physical states, each associated with a different phenotype. Propagation of one of these traits is achieved by a self-perpetuating change in the protein from one form to the other. Mounting genetic and biochemical evidence suggests that the determinant of [PSI+] is the nuclear encoded Sup35p, a component of the translation termination complex. Here we review the series of experiments supporting the yeast prion hypothesis and provide another look at the 30 years of work preceding this theory in light of our current state of knowledge.


Subject(s)
Fungal Proteins/metabolism , Peptide Termination Factors , Prions/metabolism , Protein Biosynthesis , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/metabolism , Amino Acid Sequence , Animals , Codon, Nonsense , Humans , Molecular Chaperones/metabolism , Molecular Sequence Data
12.
Mol Cell Biol ; 19(2): 1325-33, 1999 Feb.
Article in English | MEDLINE | ID: mdl-9891066

ABSTRACT

The maintenance of [PSI], a prion-like form of the yeast release factor Sup35, requires a specific concentration of the chaperone protein Hsp104: either deletion or overexpression of Hsp104 will cure cells of [PSI]. A major puzzle of these studies was that overexpression of Hsp104 alone, from a heterologous promoter, cures cells of [PSI] very efficiently, yet the natural induction of Hsp104 with heat shock, stationary-phase growth, or sporulation does not. These observations pointed to a mechanism for protecting the genetic information carried by the [PSI] element from vicissitudes of the environment. Here, we show that simultaneous overexpression of Ssa1, a protein of the Hsp70 family, protects [PSI] from curing by overexpression of Hsp104. Ssa1 protein belongs to the Ssa subfamily, members of which are normally induced with Hsp104 during heat shock, stationary-phase growth, and sporulation. At the molecular level, excess Ssa1 prevents a shift of Sup35 protein from the insoluble (prion) to the soluble (cellular) state in the presence of excess Hsp104. Overexpression of Ssa1 also increases nonsense suppression by [PSI] when Hsp104 is expressed at its normal level. In contrast, hsp104 deletion strains lose [PSI] even in the presence of overproduced Ssa1. Overproduction of the unrelated chaperone protein Hsp82 (Hsp90) neither cured [PSI] nor antagonized the [PSI]-curing effect of overproduced Hsp104. Our results suggest it is the interplay between Hsp104 and Hsp70 that allows the maintenance of [PSI] under natural growth conditions.


Subject(s)
Fungal Proteins/metabolism , HSP70 Heat-Shock Proteins/metabolism , Heat-Shock Proteins/metabolism , Prions/metabolism , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/metabolism , Adenosine Triphosphatases , Fungal Proteins/genetics , Gene Expression , Genes, Fungal , HSP70 Heat-Shock Proteins/genetics , HSP90 Heat-Shock Proteins , Heat-Shock Proteins/genetics , Prions/chemistry , Prions/genetics , Protein Conformation , Saccharomyces cerevisiae/genetics , Solubility , Suppression, Genetic , Temperature
13.
Nucleic Acids Res ; 25(18): 3665-71, 1997 Sep 15.
Article in English | MEDLINE | ID: mdl-9278488

ABSTRACT

The ability to place a series of gene constructs at a specific site in the genome opens new possibilities for the experimental examination of gene expression and chromosomal position effects. We report that the FLP- FRT site-specific recombination system of the yeast 2mu plasmid can be used to integrate DNA at a chromosomal FRT target site in Drosophila. The technique we used was to first integrate an FRT- flanked gene by standard P element-mediated transformation. FLP was then used to excise the FRT- flanked donor DNA and screen for FLP-mediated re-integration at an FRT target at a different chromosome location. Such events were recovered from up to 5% of the crosses used to screen for mobilization and are easily detectable by altered linkage of a white reporter gene or by the generation of a white + gene upon integration.


Subject(s)
DNA Nucleotidyltransferases/genetics , DNA/genetics , Drosophila/genetics , Genes, Insect , Recombination, Genetic , Animals , Gene Expression Regulation , Gene Targeting
14.
Trends Genet ; 12(11): 467-71, 1996 Nov.
Article in English | MEDLINE | ID: mdl-8973157

ABSTRACT

The unusual genetic behaviour of two yeast extrachromosomal elements [PSI] and [URE3] is entirely consistent with a prion-like mechanism of inheritance involving an autocatalytic alteration in the conformation of a normal cellular protein. In the case of both yeast determinants the identity of the underlying cellular prion protein is known. The discovery that the molecular chaperone Hsp104 is essential for the establishment and maintenance of the [PSI] determinant provides an explanation for several aspects of the puzzling genetic behaviour of these determinants. What remains to be explained is whether these determinants represent 'disease states' of yeast or represent the first examples of a unique mechanism for producing a heritable change in phenotype without an underlying change in genotype.


Subject(s)
Fungal Proteins/genetics , Prions/genetics , Saccharomyces cerevisiae Proteins , Yeasts/genetics , Gene Expression Regulation, Fungal , Glutathione Peroxidase , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Models, Biological , Peptide Termination Factors , PrPC Proteins/chemistry , PrPC Proteins/genetics , PrPC Proteins/metabolism , PrPSc Proteins/chemistry , PrPSc Proteins/genetics , PrPSc Proteins/metabolism , Prions/metabolism , Protein Conformation
15.
J Exp Biol ; 199(Pt 8): 1837-44, 1996 Aug.
Article in English | MEDLINE | ID: mdl-8708583

ABSTRACT

To determine how the accumulation of the major Drosophila melanogaster heat-shock protein, Hsp70, affects inducible thermotolerance in larvae and pupae, we have compared two sister strains generated by site-specific homologus recombination. One strain carried 12 extra copies of the Hsp70 gene at a single insertion site (extra-copy strain) and the other carried remnants of the transgene construct but lacked the extra copies of Hsp70 (excision strain). Hsp70 levels in whole-body lysates of larvae and pupae were measured by ELISA with an Hsp70-specific antibody. In both extra-copy and excision strains, Hsp70 was undetectable prior to heat shock. Hsp70 concentrations were higher in the extra-copy strain than in the excision strain at most time points during and after heat shock. Pretreatment (i.e. exposure to 36 degrees C before heat shock) significantly improved thermotolerance, and this improvement was greater and more rapid in larvae and pupae of the extra-copy strain than in those of the excision strain. The experimental conditions resemble thermal regimes actually experienced by Drosophila in the field. Thus, these findings represent the best evidence to date that the amount of a heat-shock protein affects the fitness of a complex animal in the wild.


Subject(s)
Drosophila melanogaster/physiology , Gene Expression , HSP70 Heat-Shock Proteins/genetics , HSP70 Heat-Shock Proteins/physiology , Hot Temperature , Protein Engineering , Animals , Drosophila melanogaster/genetics , Kinetics , Larva/physiology , Pupa/physiology , Recombination, Genetic
16.
Science ; 268(5212): 880-4, 1995 May 12.
Article in English | MEDLINE | ID: mdl-7754373

ABSTRACT

The yeast non-Mendelian factor [psi+] has been suggested to be a self-modified protein analogous to mammalian prions. Here it is reported that an intermediate amount of the chaperone protein Hsp104 was required for the propagation of the [psi+] factor. Over-production or inactivation of Hsp104 caused the loss of [psi+]. These results suggest that chaperone proteins play a role in prion-like phenomena, and that a certain level of chaperone expression can cure cells of prions without affecting viability. This may lead to antiprion treatments that involve the alteration of chaperone amounts or activity.


Subject(s)
Fungal Proteins/biosynthesis , Heat-Shock Proteins/physiology , Prions/biosynthesis , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/physiology , Fungal Proteins/genetics , Fungal Proteins/physiology , Gene Expression , Heat-Shock Proteins/genetics , Mutation , Saccharomyces cerevisiae/genetics , Suppression, Genetic
17.
Curr Biol ; 3(12): 842-53, 1993 Dec 01.
Article in English | MEDLINE | ID: mdl-15335817

ABSTRACT

BACKGROUND: Heat-shock proteins (hsps) are thought to protect cells against stresses, especially due to elevated temperatures. But while genetic manipulation of hsp gene expression can protect microorganisms and cultured metazoan cells against lethal stress, this has so far not been demonstrated in multicellular organisms. Testing whether expression of an hsp transgene contributes to increased stress tolerance is complicated by a general problem of transgene analysis: if the transgene cannot be targeted to a precise site in the genome, newly observed phenotypes may be due to either the action of the transgene or mutations caused by the transgene insertion. RESULTS: To study the relationship between heat tolerance and hsp expression in Drosophila melanogaster, we have developed a novel method for transgene analysis, based upon the site-specific FLP recombinase. The method employs site-specific sister chromatid exchange to create an allelic series of transgene insertions that share the same integration site, but differ in transgene copy number. Phenotypic differences between members of this series can be confidently attributed to the transgenes. Using such an allelic series and a novel thermotolerance assay for Drosophila embryos, we investigated the role of the 70 kD heat-shock protein, Hsp 70, in thermotolerance. At early embryonic stages, Hsp70 accumulation was rate-limiting for thermotolerance, and elevated Hsp70 expression increased survival at extreme temperatures. CONCLUSION: Our results provide an improved method for analyzing transgenes and demonstrate that, in Drosophila, Hsp70 is a critical thermotolerance factor. They show, moreover, that manipulating the expression of a single hsp can be sufficient to improve the stress tolerance of a complex multicellular organism.

18.
Science ; 248(4959): 1112-5, 1990 Jun 01.
Article in English | MEDLINE | ID: mdl-2188365

ABSTRACT

A heat shock protein gene, HSP104, was isolated from Saccharomyces cerevisiae and a deletion mutation was introduced into yeast cells. Mutant cells grew at the same rate as wild-type cells and died at the same rate when exposed directly to high temperatures. However, when given a mild pre-heat treatment, the mutant cells did not acquire tolerance to heat, as did wild-type cells. Transformation with the wild-type gene rescued the defect of mutant cells. The results demonstrate that a particular heat shock protein plays a critical role in cell survival at extreme temperatures.


Subject(s)
Fungal Proteins/genetics , Heat-Shock Proteins/physiology , Hot Temperature , Saccharomyces cerevisiae/physiology , Cloning, Molecular , Fungal Proteins/biosynthesis , Genes, Fungal , Heat-Shock Proteins/biosynthesis , Heat-Shock Proteins/genetics , Mutation , Restriction Mapping , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/growth & development
19.
Mol Cell Biol ; 9(11): 5265-71, 1989 Nov.
Article in English | MEDLINE | ID: mdl-2689876

ABSTRACT

Analysis of the cloned gene confirms that hsp26 of Saccharomyces cerevisiae is a member of the small heat shock protein superfamily. Previous mutational analysis failed to demonstrate any function for the protein. Further experiments presented here demonstrate that hsp26 has no obvious regulatory role and no major effect on thermotolerance. It is possible that the small heat shock protein genes originated as primitive viral or selfish DNA elements.


Subject(s)
Heat-Shock Proteins/genetics , Saccharomyces cerevisiae/genetics , Amino Acid Sequence , Base Sequence , Cloning, Molecular , DNA Mutational Analysis , DNA, Fungal/genetics , Molecular Sequence Data , Sequence Homology, Nucleic Acid , Temperature , Time Factors
20.
Genetics ; 122(2): s1-s48, 1989 Jun.
Article in English | MEDLINE | ID: mdl-17246502
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