I've spent this last week familiarizing myself with this article for my biochemistry class. Obviously, the article is way to large to bite off in one blog. One spot that draws my curiosity.
The AUR1 is promoted by the presence of Galactose. The kicker is that the presence of Glucose will turn off the gene. The organism is unable to live without the target sphingolipids. Is there some reason for this? I would think that adaptation would have long since accounted for this. Weird.
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Does Galactose involve devouring planets?
Is this one of those processes involved in diabetes? It seems like glucose does all kinds of nasty stuff if you let it roam too much where it doesn't belong.
Mark - The gene was probably adapted just fine, at least until humans started jacking with it.
The researchers intentionally put the AUR1 gene isolated from kinetoplastids under control of a yeast promoter (Gal1) that could be induced (by galactose) or suppressed (by glucose). This is explained in the Experimental Procedures section and again in the Results, about 10 lines up from the bottom of page 20202.
I haven't read the rest of the paper, but I assume they turned the gene on and off to see what effect expression of the gene had on the yeast cells.
I second Tex's comment. It was an artificial construct. I don't know where the Gal1 promoter is from, probably a bacterium. Such a setup is a neat way of regulating say galactosidase. In the presence of galactose the enzyme is expressed to deal with it, in the presence of glucose it is not required so is inhibited. In the presence of both (feeding on Sucrose) there will be a balance.
It has nothing to do with sphingolipid synthesis, it was just a piece of biotech that allows them control of the gene after they put it in mammalian cells. Doing this sort of thing is standard practice, happens all the time.
Yeah, it's much more common in yeast though. The GAL inducible promoter is a great tool for overexpressing proteins (for purification or phenotypic effects), or even tracking its movement through the cell: say you fuse GFP to your protein of interest and put it under the promoter. Where does it end up after 5, 10, 60, 1800 minutes of expression? Good way to characterize transport systems.