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Science

Prions, Darwin's Friend 48

Posted by michael from the say-hello-to-my-little-friend dept.
blamanj writes "Prions, the recently discovered bits of protein thought to be responsible for mad cow disease are turning up all over. It has been shown that prions change the behavior of yeasts, and may therefore offer a speedy way for yeast to evolve."
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Prions, Darwin's Friend More

Prions, Darwin's Friend

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  • How (Score:1)

    by egoff ( 636181 )
    infectious.

  • You know what this means... (Score:5, Funny)

    by Smidge204 ( 605297 ) on Tuesday August 17, 2004 @05:47PM (#9996134) Journal
    Super beer! Man, for once all this science mumbojumbo actually pays off!

    =Smidge=

  • Mad Yeast Disease? (Score:4, Funny)

    by Carnildo ( 712617 ) on Tuesday August 17, 2004 @05:51PM (#9996154) Homepage Journal
    Does this mean that it's no longer safe to drink beer and eat bread?
    • Whoever modded the parent off-topic is an idjit. People, you don't make bread OR beer without yeast, which is influenced, apparently, by these prions. The same prions that are suspected to be the cause of Mad Cow Disease. See the connection? Yeah, the parent is definitely on-topic.
      • The parent is nothing more than a troll (meant that in the good way, as in "fishing for silly answer"). And you gave him that silly answer :P

        Some prions are *linked* to (causes of) diseases, but they're not necessarily always "bad things". It's like saying "oh no, I won't eat cow meat anymore, because some cows have the MadCowDisease", or even more obvious, "I'll never eat anything organic again, because it has genes, and some genes cause genetic disorders, so I'm afraid".

        Yup... lack of logic can be damag

      • Re:Mad Yeast Disease? (Score:5, Informative)

        by Anonymous Coward on Tuesday August 17, 2004 @06:44PM (#9996511)
        The same prions that are suspected to be the cause of Mad Cow Disease. See the connection? Yeah, the parent is definitely on-topic.

        Except that these prions are not at all related to the Mad cow disease ones. "Prion" is a class of infectious substance, akin to "bacterium" or "virus". It's a relatively new class, so the mad cow disease ones are best known, but saying "Yeast prions will give you vCJD" is like saying "plant bacteria will give you tuberculosis".

      • And, in addition to what my sibling posts have already pointed out, you can make bread without yeast. You can use another raising agent, as in soda bread [allrecipes.com] (which uses baking soda), or consider the many unleavened breads, which (by definition) don't have anything in them to make them rise.

        And as for beer... well, some things that are sold a beer bear a remarkable similarity to a liquid that we all produce without using any yeast ;-)

  • The Selfish Protein (Score:4, Funny)

    by danratherfan ( 624592 ) on Tuesday August 17, 2004 @05:57PM (#9996207) Journal
    If only the Selfish Protein knew how much pain it's causing mankind.

    Somebody call Dawkins. I smell another book.
  • Instead of relying on technology all the time, maybe we could get back to actually living for working instead of working for a living.
    • I consider technology to be a natural extension of evolution - it's just that the progress is not totally random, so it's a lot more effective.
    • There is no evidence that humans have stopped evolving. Indeed, if you waited for a few hundred generations, you'd see it happening.

      Be patient, Grasshopper.

      • well, human gene base is quite small compared to animals i recall, something like two chimps from the same tribe can have more variation in the genes than two humans chosen randomly from anywhere from the planet.

        (though, there's differences in average height and whatever, i guess that would count as evolution that those change between distant generations)
        • True, but we (humans) nearly died off not that long ago. It was so bad, that from looking at mitochondrial DNA it looks like we are all descend from a one woman [google.com]. (Not to be confused with "Eve", there were other women alive at her time)

          It's neat to see that prions are involved in inheretance. We inherent only DNA from our fathers, but there are lots of cell parts that don't come from nuclear DNA, but divide from our mother's egg. Not to mention that our genes can be "active" or "inactive" when we get t

          • Re:Now if they could only get humans to evolve aga (Score:5, Interesting)

            by JanneM ( 7445 ) on Tuesday August 17, 2004 @09:59PM (#9997440) Homepage
            It was so bad, that from looking at mitochondrial DNA it looks like we are all descend from a one woman.

            _Every_ animal and plant species trivially descends from one individual (counted as females from mitochondrial DNA for simplicity, but it holds for the "real" DNA as well). Nothing strange about it.

            What makes our recent past interesting is that the youngest common ancestor is a lot younger than the species. That can indicate a population crunch - though it is not proof of it by any means.

            A speciation event would look just the same, for instance - a separate subgroup splits off and grows to dominate, while the original species dies off. Of course, nobody would see it as a speciation event until enough time has passed for the distinct groups to actually differ enough to no longer be able to interbreed.

    • Heinlein's Methuselah's Children talked about genetically improving humans. Unfortunately, unimproved humans found the "improved" human too revolting to deal with.

      Star Trek: TOS touched on human evolution with Khan's supermen, as well as with the two personnel (the commander(lieutenant?) and the psychologist) who got zapped by an ion storm.

      Isaac Asimov touched on it in his universe with the Spacers. (Specifically one of the first fifty or so worlds colonized from Earth...that one developed a race of huma
      • The problem with the SFnal vision of the "hated race of supermen" (which goes at least back to Slan) is that no one is going to breed a race of posthumans who are superior to their makers in every way, nor is one going to emerge by mutation. Instead, if it does turn out that substantial improvements to the human germline are possible, what will happen is that we'll tinker around the edges, improving things here and there. The improvements that will make up the change from human to superhuman will happen o
      • Or the cartoon ExoSquad, as I recall. That cartoon had a lot of promise. I don't remember if I ever saw the whole thing, but it was pretty grown up for a cartoon.
  • Great. Just what we needed. Smart Bread (Except during Passover)

    • As an Israelly, I would say one needs smart bread especially on Passover.

      I can see the adds now: "your merchandise will evade religious/government inspectors by itself ! A fortune saved in bribes !"

  • Hmm... (Score:2, Funny)

    by numbski ( 515011 ) *
    Yeast, LOAF [slashdot.org]...

    Taco, what are you trying to tell us exactly?

  • More and more of the neat stuff is epigenetic... (Score:5, Interesting)

    by Anonymous Coward on Tuesday August 17, 2004 @06:29PM (#9996408)
    ...from DNA methylation effecting cell differentiation and cloning and cancer to this new possible epigenetic mechanism for coping with environmental stresses. It doesn't live in the DNA sequence it lives in the runtime. How much more really cool stuff will be found that may be driven by the DNA or the puzzle pieces may be sequenced by it, but doesn't exist "on paper."
  • This wouldn't be the first time they "discovered" that something that is "bad" in some cases is "good" in others.

    So what does that article tell us?
    That, by having a protein (infectious variant prion) that causes others to malfunction (generating altered proteins), so, in some cases, it *can* cause a "spontaneous" (read:accidental) mutation/selection that will (in the short run) allow that cell to survive when it normally wouldn't have, thus creating a evolutionary "short-cut".

    Wellcome to the "Darwin's Evo
    • It's one thing to assert evolution through unknown mechanisms (as Darwin did), and another to identify and model these mechanisms.

      If this is true, and if this is widespread (at least in prokaryotes), than this may be a significant addition to the understanding of epigenetics's role in evolution. Very much NOT 19th century.

      ( Disclaimer: IANAB )

      • Re:You're missing the point. (Score:5, Interesting)

        by Belgand ( 14099 ) <belgand@planetfortress . c om> on Wednesday August 18, 2004 @12:54AM (#9998278) Homepage
        Speaking as a biologist with research interests in molecular genetics (mutation specifically) and who spent a good deal of time working in a yeast lab this is just fucking amazing. There is a great deal of potential in this.

        If prions are acting as a form of epigenetic plasmids then... wow. I mean, just wow. The sheer possibility for customized prions for gene therapy in somatic eukaryotic cells could be huge.
        • As a computer scientist who has always had an interest (though never academically persued) in molecular genetics, can you explain this a bit better.

          I know that mutations naturally occur, do these pions accelerate the process or tailor the process to more effective mutation?
        • Exactly.

          The one way that this could be akin to a "protein plasmid" would be custom designed prions that would prionize* with native regulatory proteins (either at transcription or further downstream somewhere, heck you could even prionize the final, presumably broken, gene product)....

          Um... ....of course that pre-assumes a lot of non-existent molecular modeling and synthesizing technologies, but hey, Protein Plasmids for Humans!!

          * prionize: to exhibit an alternative protein configuration that catalyzes t

  • mechanism for variable expression in vertabrates? (Score:5, Informative)

    by oliphaunt ( 124016 ) on Tuesday August 17, 2004 @08:03PM (#9996899) Homepage
    from the article:
    In its non-infectious form, the protein normally helps to read and convert the DNA code into other proteins. But in its infectious form, the prion stops working. This means that many proteins are manufactured slightly sloppily.


    The team believes that prions may therefore offer a speedy way for yeast to evolve, because those cells with the infectious prion churn out a whole range of slightly altered proteins. Normally this is bad news for the yeast, but when the cells find themselves in a tough spot, one or two of them may grow better in the new conditions as a result, and so help the colony to survive.


    This is interesting for a number of reasons, but the one that sticks out in my mind is the transfer of plasmids [cmu.edu] between prokaryotes. Eukaryotes, like eyu and me, don't pass our DNA around as casually as, say, Staphlococcus Aureus does. This has the benefit that our DNA is relatively stable, meaning that we are almost guaranteed to be able to breed with someone two or three generations younger than we are ourselves (hellOOOO, Hef!) but the trade-off is that we're not very responsive to environmental stressors that require quick adaptation to survive.

    In simpler terms, through conjugation live bacteria can pick up spare DNA from other living bacteria and immediately "evolve" to meet a new environmental challenge without needing to wait for another generation to be born before the mutation can take effect. The plasmid DNA is then passed along to the daughter cells of successuful bacteria. This obviously confers huge selective advantages on bacteria which pick up plasmids that code for antibiotic resistance genes.

    I interpret this prion research in yeast to suggest that yeast can experience the same kind of variable protein expression as bacteria, throught the mechanism of prion inactivation. This is significant because eukaryotic cells do not experience conjugation, and generally do not have plasmids, but DO transport various small proteins across the cell wall and into the cytoplasm.

    And if it works for yeast, perhaps the prion mechanism is intended to perform the same function in humans, or in the cows that end up with BSE. The test would be to find some gene in a higher mammal that expresses one way when a prion is in conformation A, but expresses another way in conformation B...

    • Re:mechanism for variable expression in vertabrate (Score:5, Informative)

      by Dr. GeneMachine ( 720233 ) on Wednesday August 18, 2004 @08:20AM (#10000308)
      I wouldn't compare this effect to plasmid based inheritance. As far as I understand the article, the yeast prion PSI is a suppressor of nonsense mutation. This means that PSI works at the level of translation, the production of proteins from genetic information. Translation is normally a well regulated process which terminates at so called stop codons. PSI now enables the yeast translation machinery to read over this stop codons, thereby producing longer proteins with somewhat altered functions, or even new proteins which where silenced by stop codons. At this point this mechanism does not created inheritable phenotypes. Nevertheless, the group of True et al. found inheritably changed phenotypes in some PSI+ stems. This might be - and I'm speculating here - due to the production of altered replication proteins by this mechanism, which then introduce more mutations into the yeast genome.

      In this light, the mechanism of yeast prion action is more akin to some error prone repair and replication mechanisms in bacteria, which are triggered by stress and result in an increase in spontaneous mutations. This is different from plasmid transfer, which is a directed transfer of well-defined genetic information

      In case of mammalian prions, I see no indication of a similar mechanism. Human prion protein huPrP is a cell surface protein which does not interfere with the translation apparatus or with genetic processes in the nucleus. It rather appears to be involved in regulatory processes which transduce signals from outside into the cell.
      Yeast and mammalian prions share no common characteristics except for the ability to exist in to different conformations and to autocatalytically propagate one of these conformations. In general, prions are no functionally homogenous group. Another example would be the prions of slime molds, which play a role in the exchange of genetic information by cell fusion. Here the prion-conversion mechanism creates some kind of incompatibility groups, shutting down the fusion zone if two cells belonging to different compatibility groups try to fuse.

      The prion phenomenon is a basic biophysical characteristic, it has not to be bound to a certain function. The fact that yeasts and fungi have found a way to use this physical property of certain proteins does not implicate that other prions have to have useful functions also. It is absolutely possible that mammalian prions are a purely pathological phenomenon.

  • Macro Evolution - Khan! (Score:3, Interesting)

    by erinacht ( 592019 ) on Wednesday August 18, 2004 @04:48AM (#9999053) Homepage
    If "safe" prions could be harnessed or even engineered and a human could be placed in an environment that would stress their inbuilt abilities - eg space travel, it must be possible to pass on the "benefits" of their MACRO evolution to the next generation - perhpas getting rid of legs or whatever else would suit long term space dwellers.

    Imagine a ship travelling to our nearest neigbouring star, it would take several generations for us to reach there so the colonists when they arrived wouldn't actually be "human" like we are!

    Now if we can work out the environment on the alien planet before we send off the ship, we could engineer the prion/environment to force evolution's hand to create the modifications required to live in the environment they're going to.

    I feel a novel coming on!
  • In this case, prions are causing the yeast cells to make slightly varied proteins. when they are exposed to stress conditions, some very very few of these infected yeasts gain a more efficient way of survival because of this pre-adaptation, thus by having the upper hand in the competition for limited resources, they are selected for survival. this effect is very similar to any kind of mutagens (mutation causing agents), in fact the main test to determine the potential of a chemical to cause cancer is workin
  • Where the hell have you been for the past 40+ years (since kuru was discovered), or even 20+ years (1982, when the term Prion was introduced by Prusiner - meaning "PROteinaceous INfectious particles")?

    You have a strange meaning for "recent"...

  • Prions, Darwin's Friend. No they aren't. Darwin doesn't have any FRIENDS!

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