Monday, March 26, 2007

A new ERV just in time for Easter!

The first lentiviral ERV was found in Oryctolagus cuniculus, the European rabbit! ERVs are about the best we can hope for in terms of viral 'fossils', so finding a lentiviral ERV can help us understand the evolution of lentiviruses.

Because of their absence in our genome, we assumed that lentiviruses were simply 'newer' viruses, evolutionarily--theyre younger, so they havent had as many opportunities to integrate. These authors think their ERV was inserted in the European rabbit genome about 7 million years ago. Our HERVs inserted themselves ~50 million years ago, so even though this RELIK (cute name!) is 'ancient', I would still call it young on an evolutionary timescale.

RELIK is pretty simple for a complex retrovirus (lentiviruses are 'complex', vs a 'simple' betaretrovirus), but it still has lots of tasty bits: gag (matrix, capsid, nucleoproteins), pol (protease, reverse transcriptase, RNaseH, dUTPase, integrase) and env (subunit and transmembrane) of course-- but also tat and rev! Its sequence is also A rich, C poor, characteristic of lentiviruses-- So I believe them.

Oh now before the Deniers start hopping around, they searched 46 mammalian genome libraries. And they only found these guys. And though the RELIKs were relatively 'complete', they were all hopelessly degraded. For example, one chunk had five stop codons, 11 frameshift mutations, and two SINE insertions. You arent going to get a pathogenic ERV out of that.

4 comments:

Chris Noble said...

Hi ERV,

While we're talking about cute little mammals (we get the Easter Bilby in Australia), what did you make of this paper from last year about Koala ERVs?

Retroviral invasion of the koala genome.

ERV said...

Bleh just saw this comment, Chris, sorry!

No, I havent seen it--Hmm, they say something kinda strange in the abstract, though:
A group of more intact endogenous retroviruses are considered to have entered the genomes of some species more recently, through infection by exogenous viruses, but this event has never been directly proved.
I was under the impression that retroviruses like MMTV had exogenous and endogenous components. All the more reason to read the paper! Thanks!

Chris Noble said...

I guess the real question is the age of the endogenous MMTVs.

Do all mice have the same number endogenous MMTVs in the same location in the genome?

I thought that perhaps HIV "rethinkers" would use the KoRV paper as evidence that HIV might be endogenous even though not every human has proviral HIV DNA.

ERV said...

Im not 100% on this, but I dont think mice necessarily do have all their ERVs in the same locations, because of the endogenous/exogenous limbo of some of their retroviruses.

I need to research this more :)