Comments on: How ‘superspreader’ viruses invaded our genes

By: Totto

Totto — Fri, 27 Apr 2012 04:52:05 +0000

This is very interesting. However, I couldn’t find a clue of how ERVs or IAPs got their env gene missed/lost during translation, hence it’s not involved in assembly which make the progeny virus unable to infect new cells. Any information on this?

By: Nathan Myers

Nathan Myers — Thu, 26 Apr 2012 03:37:28 +0000

I see this differently. The ones without env are confined to the cell, and reproduce there or not at all. Their fate depends on the host's own. The ones with access to an env can make the jump to other species, and indeed that's how they got into us in the first place. They don't need to fill up the the genome to be successful. They succeed when they are expressed and escape. This distinction is probably visible in the viral genomes. I'm betting that although there are many more copies of the viruses without env, there's lots more variety in the ones that have it.

By: Amber Farooqui

Amber Farooqui — Wed, 25 Apr 2012 17:41:21 +0000

Nice post. I wonder what happens with RNA viruses and whether some of them are “picky” to invade “the genes” that might help in systemic spread and fatal outcome

By: Ed Yong

Ed Yong — Wed, 25 Apr 2012 08:21:21 +0000

@Zmil – Thank you. That distinction was lost on me. I’ve amended the offending paragraph.

By: zmil

zmil — Tue, 24 Apr 2012 23:01:16 +0000

Nitpick that does not really affect the conclusion of this very interesting post:

Env does not make the viral protein coat, but rather the viral envelope protein, which is inserted into the lipid membrane which surrounds the protein coat. Without Env, the viruses can still make particles within the cell, and in some cases even exit the cell complete with a lipid membrane, but, as you noted, without Env, they have no way to get back inside.

By: Ed Yong

Ed Yong — Tue, 24 Apr 2012 18:50:31 +0000

Good question. There are some virologists who would actually say that this is the true form of a virus, and the coated particles that float between cells are something extra.

There is also a long and rich debate about whether viruses are alive or not (some links: http://www.scientificamerican.com/article.cfm?id=are-viruses-alive-2004 and http://www.virology.ws/2004/06/09/are-viruses-living/).

And *that* reflects the fact that we really don’t have a clear answer about how the define “life”. Clearly, an animal is alive. As is a bacterium. My table isn’t. But what about a replicating molecule? A virus? A prion? A rock containing replicating molecules? Personally, I’d say that this is an attempt to put a firm divide on a continuum. I agree with what Szostak has to say here: http://www.txchnologist.com/2012/can-a-scientist-define-life-by-carl-zimmer

By: G Pares

G Pares — Tue, 24 Apr 2012 15:08:45 +0000

Do you think that a sequence of DNA without the capacity to infect other cells or individuals can still be considered a virus? At which point we tell that something is alive or it’s just a complex molecule? Or it’s the same? It’s kind of frightening in some way, I feel less a living thing and more a bunch of DNA.