To Ahmed Alzohairy,
The question which should be asked here - what do words 'great similarity' mean?
If it just imply that there are great structural similarity and, for some extend, similarity of their sequences, than it is not surprising because viruses derived from retrotransposons and they share many common features. The essential enzymes have very conserved domains which possess great similarity to each other from different retrotransposon and viruses.
However, there is also another layer to this question. If we are talking about particular genome, e.g. human, we have to remember that some retrovirus sequences can be captured by genome and become internalized and vertically transmitted from progenitor to progeny; but it does not change the fact that originally viruses derived from retrotransposons through several steps of modular evolution.
I think this is helpful, http://www.ncbi.nlm.nih.gov/books/NBK19468/
No, actually, it is the other way around. Here THE original paper: http://www.ncbi.nlm.nih.gov/pubmed/1698615
Human LTR retrotransposons are equivocally endogen retroviruses (HERVs), which invaded the human genome >25 Myr ago (IHGSC, 2001). I am not sure :)
To Ahmed Alzohairy,
"Human LTR retrotransposons are equivocally endogen retroviruses (HERVs), which invaded the human genome >25 Myr ago (IHGSC, 2001)."
Technically and out of context, this is right, BUT...
LTR retrotransposons (HERVs) in human genome evolved as a part of genome during the long history of evolution starting from single cell eukaryotes. LTR retrotransposons did not invade genome from outside as one could imagine in case of retrovirus invasion, they arose from within and spread through genome.
But this does not explain their great similarity with Viruses !!!! something missing :) ?
To Ahmed Alzohairy,
The question which should be asked here - what do words 'great similarity' mean?
If it just imply that there are great structural similarity and, for some extend, similarity of their sequences, than it is not surprising because viruses derived from retrotransposons and they share many common features. The essential enzymes have very conserved domains which possess great similarity to each other from different retrotransposon and viruses.
However, there is also another layer to this question. If we are talking about particular genome, e.g. human, we have to remember that some retrovirus sequences can be captured by genome and become internalized and vertically transmitted from progenitor to progeny; but it does not change the fact that originally viruses derived from retrotransposons through several steps of modular evolution.
But How could viruses derived from retrotransposons if they are older than their hosts??
According to International Committee on Taxonomy of Viruses currently Retrotransposons are classified into Pseudovidae and Metaviridae families of viruses (without an affiliation to any order).
Retrotransposons are more diverse, their structures are simpler and they are spreed in all eukaryotes (first, think about one cell organisms). Of curse, there are numerous phylogenetic studies in this topic in the years1980 -90. As a result of many studies it is now considered that viruses are evolved from retrotransposons. Dynamic balanced evolution of both made modern complex genomes, where following the ancestry is almost impossible, as sequences between genes accumulates mutations rapidly.
The structure similarity between Retrotransposon and retroviruses is not by coincides. Both the theory of "common ancestor" and the theory of " Decent with modification" can apply to explain this similarity and evolution. I agree to some extent with " Angelika Voronova " and " Olga Novikova
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