The Missing Transposable Link
March 6, 2011 10:47 PM Subscribe
posted by jjray (35 comments total)
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In the 1940s Barbara McClintock
discovered the remarkable phenomenon of mobile genetic elements, or transposons
: parasitic DNA that makes up a significant fraction of the human genome. (Here is a video segment about McClintock: Part 1
.) The discovery remains highly important: we now know that transposons play a role in driving genome evolution
. Where do they come from? A compelling hypothesis is that some evolved from viruses
Now a marine biology group at UBC has found a virus whose closest genetic relative is a type of transposon.
(The paywalled paper's abstract is here
.) But that is not even the interesting part.
It turns out that the virus in question is a type of virophage- reader, it infects other viruses
. Previously, mimivirus
was shown to be infected by the so-called Sputnik virophage
for pretty pictures
The new one they are calling mavirus. It infects Cafeteria roenbergensis virus
, or CroV
. CroV, in turn, infects a (eukaryotic) single-celled marine bicosoecid called, well, Cafeteria roenbergensis
. Mavirus appears to protect C. roenbergensis
from CroV, thus gaining a toehold in the genome: permanent incorporation of mavirus would confer permanent protection . If this explains the origins of transposons, it may be that they began with mutualistic host-virus interactions, and only later evolved into parasitic DNA.