Freethought & Rationalism Archive

Advocatus Diaboli · 04-30-2003, 01:39 AM

How do we know that ERVs are from viruses? Is there a spesific kind of DNA which clearly tells they are from viruses?

Thanks!

Wounded King · 04-30-2003, 04:02 AM

There are sequences coding for protein coats and other elements characteristic of viruses.

Quetzal · 04-30-2003, 04:28 AM

Quote:

Originally posted by Advocatus Diaboli
How do we know that ERVs are from viruses? Is there a spesific kind of DNA which clearly tells they are from viruses?

Thanks!

As WK noted, ERV's have most often sequence similarity with "standard" retroviruses. All retroviruses have at least the genes 5' - gag - pol - env - 3' in that sequence flanked by LTR (long terminal repeats) - although bunches have more genes. All identified ERV's have internal sequences homologous to gag, pol, and sometimes env open reading frames flanked by LTRs. What I think interesting is that evolution can co-opt even the bad things like retroviruses to functionality:

Quote:

Nature. 2000 Feb 17;403(6771):715, 717.

"Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis."

Mi S, Lee X, Li X, Veldman GM, Finnerty H, Racie L, LaVallie E, Tang XY, Edouard P, Howes S, Keith JC Jr, McCoy JM.

Many mammalian viruses have acquired genes from their hosts during their evolution. The rationale for these acquisitions is usually quite clear: the captured genes are subverted to provide a selective advantage to the virus. Here we describe the opposite situation, where a viral gene has been sequestered to serve an important function in the physiology of a mammalian host. This gene, encoding a protein that we have called syncytin, is the envelope gene of a recently identified human endogenous defective retrovirus, HERV-W. We find that the major sites of syncytin expression are placental syncytiotrophoblasts, multinucleated cells that originate from fetal trophoblasts. We show that expression of recombinant syncytin in a wide variety of cell types induces the formation of giant syncytia, and that fusion of a human trophoblastic cell line expressing endogenous syncytin can be inhibited by an anti-syncytin antiserum. Our data indicate that syncytin may mediate placental cytotrophoblast fusion in vivo, and thus may be important in human placental morphogenesis.

Can't live with 'em, can't live without 'em.

(I would insert cheesy grin smilie here, but pz would have me executed.)

Wounded King · 04-30-2003, 06:03 AM

You are assuming that the retroviruses came before the endoviruses. There are LTR retrotransposons which may share many of these features but not be of retroviral origin. It may even be that the retroviruses originated from these retrotransposons.

Lerat E, Capy P.
Retrotransposons and retroviruses: analysis of the envelope gene.
Mol Biol Evol. 1999 Sep;16(9):1198-207.

Quetzal · 04-30-2003, 07:52 AM

Quote:

Originally posted by Wounded King
You are assuming that the retroviruses came before the endoviruses. There are LTR retrotransposons which may share many of these features but not be of retroviral origin. It may even be that the retroviruses originated from these retrotransposons.

Lerat E, Capy P.
Retrotransposons and retroviruses: analysis of the envelope gene.
Mol Biol Evol. 1999 Sep;16(9):1198-207.

Actually, I wasn't, since the topic of retrotransposons hadn't been mentioned. I am well aware of RLE retrotransposons that contain LTRs and even env homologs. I also read (awhile ago) an interesting article about the origin of retroviruses from rogue RNA elements (I'll see if I can dig it up - if not, suffice that I don't disagree with anything you wrote).

Wounded King · 04-30-2003, 01:34 PM

I thought that interpretation was implicit in your suggestion that

Quote:

evolution can co-opt even the bad things like retroviruses to functionality

Which is much less surprising, although still interesting, if retroviruses have an origin from within the genome originally.

Advocatus Diaboli · 05-02-2003, 01:45 AM

Thank you for the links and information.

Advocatus Diaboli · 05-03-2003, 04:56 PM

Wow. I'm arguing with a really skeptical and critical thinking creationist.

Now he demands a site which has the ERV's humans share with "lower animals" displayed in full detail, with charts about genealogy. :banghead:
TalkOrigins doesn't seem to have anything like that. He seems to believe that ERV's are a hoax...

Can anyone help?

Dr.GH · 05-03-2003, 05:45 PM

Quote:

Now he demands a site which has the ERV's humans share with "lower animals" displayed in full detail, with charts about genealogy.

I think that these will do for now. They will require registration.

Constructing primate phylogenies from ancient retrovirus sequences

PNAS -- Johnson and Coffin 96 (18) 10254
http://www.pnas.org/cgi/content/full/96/18/10254#Top

Isolation and phylogeny of endogenous retrovirus sequences belonging to the HERV-W family in primates

J Gen Virol -- Kim et al. 80 (10): 2613
http://vir.sgmjournals.org/cgi/content/full/80/10/2613

Nic Tamzek · 05-04-2003, 01:34 AM

The PNAS article is free online, bless their little academic hearts.

For a different take on the ERV-placenta issue, see Mike Gene's posts (which I am disputing) over on this ARN thread:

http://www.arn.org/boards/ubb-get_to...00690-p-2.html

04-30-2003, 01:39 AM	#1
Advocatus Diaboli Regular Member Join Date: Sep 2002 Location: Finland Posts: 372	Query about ERVs How do we know that ERVs are from viruses? Is there a spesific kind of DNA which clearly tells they are from viruses? Thanks!

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04-30-2003, 04:02 AM	#2
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	There are sequences coding for protein coats and other elements characteristic of viruses.

04-30-2003, 06:03 AM	#4
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	You are assuming that the retroviruses came before the endoviruses. There are LTR retrotransposons which may share many of these features but not be of retroviral origin. It may even be that the retroviruses originated from these retrotransposons. Lerat E, Capy P. Retrotransposons and retroviruses: analysis of the envelope gene. Mol Biol Evol. 1999 Sep;16(9):1198-207.

05-02-2003, 01:45 AM	#7
Advocatus Diaboli Regular Member Join Date: Sep 2002 Location: Finland Posts: 372	Thank you for the links and information.

05-03-2003, 04:56 PM	#8
Advocatus Diaboli Regular Member Join Date: Sep 2002 Location: Finland Posts: 372	Wow. I'm arguing with a really skeptical and critical thinking creationist. Now he demands a site which has the ERV's humans share with "lower animals" displayed in full detail, with charts about genealogy. :banghead: TalkOrigins doesn't seem to have anything like that. He seems to believe that ERV's are a hoax... Can anyone help?

05-04-2003, 01:34 AM	#10
Nic Tamzek Senior Member Join Date: Jan 2002 Location: California Posts: 646	The PNAS article is free online, bless their little academic hearts. For a different take on the ERV-placenta issue, see Mike Gene's posts (which I am disputing) over on this ARN thread: http://www.arn.org/boards/ubb-get_to...00690-p-2.html

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