Today's "oh, COOOOOOL" moment.

[theweaselking]

Scientist grows a virus he calls "Phoenix" - by sequencing it *out* of the human genome.

That's right, he's found a way to reconstitute *endogeneous retroviruses*.

Apparently they've been doing this for years. Why was I not informed?

Comments

[cmseward.livejournal.com]

I think the neatest thing I read about this sort of research is that they think it might lead to a *cure* for HIV, not just a treatment. (I recall something about the retrovirus being able to out-compete HIV, and since the retrovirus is already part of our DNA, it doesn't cause as much damage.)

[falconwarrior.livejournal.com]

Is there a "layman's terms" version of this? While this seems extraordinarily interesting, I am humbled by my current lack of understanding in regards to most of the terminology used.

[theweaselking.livejournal.com]

Short version:

Retroviruses, such as herpes and HIV, are viruses that not only infect your cells and multiply, but that *write themselves into your DNA* so instead of simply sitting in the cell and hijacking your cell's systems to reproduce themselves, they've actually reprogrammed the cell to perform their function.

Essentially, a retroviral infection is permanent. It writes itself into your DNA, and it stays when the cell reproduces, and everything else like that.

If it infects sperm and/or ova, this means that the retrovirus is part of the DNA that you pass on to your children, and your children will have this viral infection in the same way you did, from conception.

However, the human immune system is not so easily thwarted. Evolution being what it is, a mutation that *breaks* a permanent crippling disease is very heavily selected for, meaning the odds of a retrovirus staying *working* in the system for generations if it's got deleterious effects are very low. What happens, then, is that a mutation breaks the virus' ability to harm you, at which point there's absolutely no selective pressure to actually remove the virus from your system at all - so it sits in your DNA, occasionally spitting out proteins that the rest of your system ignores, and passes itself on to all your children, too. Since you *don't* have the disease, and everyone who doesn't have your mutation *does* have the disease, you are very heavily advantaged, and your genes will tend to outcompete the diseased ones.

That's what an endogeneous retrovirus (ERV) is - a "broken" retroviral infection from thousands or millions of years ago that exists, harmlessly, in the genome. And this man has found a way to pick an ERV from the human genome, sequence it out, figure out what it originally looked like before the mutation broke it, and build it - enabling him to resurrect the original form of the disease.

Which is AWESOME.

What's really interesting is that you can use ERVs to show common descent[1]. Since ERVs are apparently a fairly common event on the scale of the existence of DNA, and all descendents of someone with an ERV will show the same ERV, you can show that all primates have ERVs A and B, showing common descent from a common ancestor.

Further, you can show that if humans have the entire alphabet of ERVs, and chimpanzees have A through X, and gorillas have A through Q (and some extra ones in greek letters), and monkeys have A through M (with some Cyrillic letters added), you can show *where* the splits happened, in what order - because a common ERV must come from a common ancestor, and an uncommon ERV must show up *after* the split from the common ancestor. You can build a really quite detailed taxonomic tree this way.

[1]: This is simplified from the real explanation, of course, but you get the point