The Role of Retroviruses in Human Evolution

mhackarbie writes "The current edition of the New Yorker magazine has up a story about endogenous retroviruses in the genomes of humans and other species. Although researchers have known about such non-functional retroviral 'fossils' in the human genome for some time, the large amount of recent genomic data underscores just how pervasive they are, in a compelling tale that involves humans, their primate cousins, and a variety of viral invaders. Some researchers are even bringing back non-functional viral remnants from the dead by fixing their broken genes."

Comments

Re:Oh no!

[Dr. Eggman]

Obviously if enough individuals survived with cells reproducing its DNA containing the retrovirus for it to become a species-wide "fossil" it was either not very harmful or possibly even beneficial to our ancestors. You might be able to make the case that perhaps we have since lost the ability to combat these retroviruses, but then we must consider the possibility that in some individuals these portions of dormant virus data have been reactivate naturally. If this has occurred and we are indeed now ill equipt to fight it, then it would have been observed as some disease and possibly classified as a genetic disorder. Who knows, by reactivating these, we have discover the cause, and subsequently the cure (as obviously we naturally beat it once) to some terrible genetic malady!

Hmm

[pclminion]

How do we know the the retrovirus genome didn't originate with the hosts themselves? Did these viruses evolve truly independently, or might they have started out as fragments of genetic code from some larger organism which somehow escaped and became self-sufficient?

In other words, when we look at the human genome and say, "This is riddled with retroviruses!" is it not possible that the retroviruses were actually there all along, and only later became able to leave the parent cell and operate independently?

Are retroviruses actually just chunks of "rebel DNA" from our own genome, or possibly from some other species?

Re:Hmm

[Harmonious Botch]

That is a damn good question.

A 'rebel DNA leaving home' must have happened at least once, in some species, otherwise how could viruses exist? They seem way too complex to have happened by chance, and they can't evolve until they are complex enough to infect.

Re:Hmm

[cpricejones]

To understand this, you can do sequence comparisons between retroviral genes and our own genes. For example, retroviruses have an enzyme called reverse transcriptase. This enzyme is a type of polymerase. We have many polymerases in our body, and if RT developed from one of them, then there would be very substantial sequence similarity. This is one way to figure out what proteins do if you do not know their function. You compare their amino acid sequence to other known proteins and see if they are similar. This is very common, and it is how researchers establish relationships between retroviruses to understand how they evolve. For example, HIV is a member of the subgroup of retroviruses called lentiviruses, and these viruses have many things in common. HIV has a cousin called SIV (simian immunodeficiency virus) that is very similar. A really good reference is Coffin, RETROVIRUSES, from Cold Spring Harbor Press.

Re:Bringing back the dead?

[skeftomai]

Are viruses even alive in the first place?

Cambrian explosion?

[Tablizer]

Such viruses may be responsible for the Cambrian Explosion. A new kind of virus may have helped "share good ideas" like eyes, nervous systems, enzymes, etc. between different species of early animals. This may have propelled evolution by allowing life to mix and match instead of each branch having to reinvent stuff from scratch.