Yeast prions: could they be exaptations? The URE2/[URE3] system in Kluyveromyces lactis

Safadi, Rim Al; Talarek, Nicolas; Jacques, Noémie; Aigle, Michel

doi:10.1111/j.1567-1364.2010.00700.x

Cited by 26 publications

(25 citation statements)

References 13 publications

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“…Extensive barriers to transmission of [PSI+] between wild S. cerevisiae have been found, suggesting that this protection from "catching" a prion has been selected in evolution (34). The notion that prion-forming ability is generally conserved (46) is not true for Ure2p, as the Saccharomyces castellii, Kluyveromyces lactis, and Candida glabrata Ure2ps cannot become [URE3] even though they are closely related to that of S. cerevisiae Ure2p, whereas the more distantly related Candida albicans Ure2p can form a prion (33,49,50). Prion-forming ability appears to be sporadic rather than conserved.…”

Section: Discussionmentioning

confidence: 99%

Sex, prions, and plasmids in yeast

Kelly

Shewmaker

Kryndushkin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Even deadly prions may be widespread in nature if they spread by infection faster than they kill off their hosts. The yeast prions [PSI+] and [URE3] (amyloids of Sup35p and Ure2p) were not found in 70 wild strains, while [PIN+] (amyloid of Rnq1p) was found in ∼16% of the same population. Yeast prion infection occurs only by mating, balancing the detrimental effects of carrying the prion. We estimated the frequency of outcross mating as about 1% of mitotic doublings from the known detriment of carrying the 2-μm DNA plasmid (∼1%) and its frequency in wild populations (38/70). We also estimated the fraction of total matings that are outcross matings (∼23-46%) from the fraction of heterozygosity at the highly polymorphic RNQ1 locus (∼46% [PIN+] of S. cerevisiae are parallel in-register β-sheet amyloids of Sup35p, Ure2p, and Rnq1p, respectively (7-10); the [Het-s] prion of P. anserina is a β-helical amyloid of the HET-s protein (11). Sup35p is a subunit of the translation termination factor (12, 13), Ure2p is a regulator of nitrogen catabolism (14), and Rnq1p has no known function (15).The mammalian prions are uniformly lethal but nonetheless are found in wild animals. For example, chronic wasting disease of deer and elk is found in ∼10% of wild deer in parts of Wyoming, Colorado, Illinois, and Wisconsin (16). Evidently, infectious spread outpaces the lethal effects on the animals. The [Het-s] prion of P. anserina is involved in heterokaryon incompatibility, a normal function of that species, and, as a result, ∼80% of wild strains with the appropriate chromosomal genotype carry the [Het-s] (20), a result confirmed by others (21) and which we interpreted as meaning that they are substantially detrimental. Nonetheless, others argue that these prions are beneficial, promoting survival by allowing cells to resist stress (22, 23), although the reported effects were not reproducible with the same strains (24). It is reported further that certain stress conditions increase the frequency of[PSI+] when assayed using a synthetic Sup35p with an elevated prion-forming tendency (25). Here we test these conditions for an effect on prion formation by the wild-type Sup35p.Our argument, that the rare occurrence of an infectious agent in nature implies pathologic effects on the host, relies on outcross mating being a fairly frequent event. Yeast prions spread only by mating (there is no extracellular prion species in the replication cycle), and if outcross mating is extremely rare, then yeast prions could be rare even if their effects on the host were neutral. Yeast spores germinate with mating type either a or α, and a and α spores from the same tetrad may mate (intratetrad or brothersister). The mating-type switching system (homothallism) results in the clone from a single germinated spore becoming a mixture of a and α cells which can mate with each other. These two kinds of "selfing" are unlikely to spread any virus, plasmid, or prion, because probably both mating partners will lack the element, or both will have it. Alternat...

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Section: Discussionmentioning

confidence: 99%

Sex, prions, and plasmids in yeast

Kelly

Shewmaker

Kryndushkin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…However, we find that the C. glabrata Ure2p, which has the conserved prion domain sequence (residues 10-39 in S. cerevisiae), cannot form a prion. Similarly, the Kluyveromyces lactis Ure2p, which also has the conserved prion domain sequence, cannot form a [URE3] prion as tested in K. lactis itself (Safadi et al 2011). In contrast, the Ure2p of C. albicans, which lacks the conserved sequence, forms a prion much like that of S. cerevisiae.…”

Section: Hostmentioning

confidence: 99%

Prion-Forming Ability of Ure2 of Yeasts Is Not Evolutionarily Conserved

et al. 2011

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ABSTRACT[URE3] is a prion (infectious protein) of the Saccharomyces cerevisiae Ure2p, a regulator of nitrogen catabolism. We show that wild S. paradoxus can be infected with a [URE3] prion, supporting the use of S. cerevisiae as a prion test bed. We find that the Ure2p of Candida albicans and C. glabrata also regulate nitrogen catabolism. Conservation of amino acid sequence within the prion domain of Ure2p has been proposed as evidence that the [URE3] prion helps its host. We show that the C. albicans Ure2p, which does not conserve this sequence, can nonetheless form a [URE3] prion in S. cerevisiae, but the C. glabrata Ure2p, which does have the conserved sequence, cannot form [URE3] as judged by its performance in S. cerevisiae. These results suggest that the sequence is not conserved to preserve prion forming ability.

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“…36,37 In Sup35, the unstructured NM region participates in the protein's function in translational termination. Genetic evolution of this region might have rendered the protein competent for prionization and thus entailed the gene product with a neofunction at the population level as bet hedging device.…”

Section: Evolutionary Origin Of [Het-s] or How A Loss-of-function Mamentioning

confidence: 99%

As a toxin dies a prion comes to life: A tentative natural history of the [Het-s] prion

Daskalov

Saupe

2015

Prion

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A variety of signaling pathways, in particular with roles in cell fate and host defense, operate by a prion-like mechanism consisting in the formation of open-ended oligomeric signaling complexes termed signalosomes. This mechanism emerges as a novel paradigm in signal transduction. Among the proteins forming such signaling complexes are the Nod-like receptors (NLR), involved in innate immunity. It now appears that the [Het-s] fungal prion derives from such a cell-fate defining signaling system controlled by a fungal NLR. What was once considered as an isolated oddity turns out to be related to a conserved and widespread signaling mechanism. Herein, we recall the relation of the [Het-s] prion to the signal transduction pathway controlled by the NWD2 Nod-like receptor, leading to activation of the HET-S pore-forming cell death execution protein. We explicit an evolutionary scenario in which formation of the [Het-s] prion is the result of an exaptation process or how a loss-of-function mutation in a pore-forming cell death execution protein (HET-S) has given birth to a functional prion ([Het-s]).

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Yeast prions: could they be exaptations? The URE2/[URE3] system in Kluyveromyces lactis

Cited by 26 publications

References 13 publications

Sex, prions, and plasmids in yeast

Sex, prions, and plasmids in yeast

Prion-Forming Ability of Ure2 of Yeasts Is Not Evolutionarily Conserved

As a toxin dies a prion comes to life: A tentative natural history of the [Het-s] prion

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