Intron loss?

Martin Kennedy mkennedy at
Sun Nov 14 00:40:13 EST 1993

n article <CGED17.487 at>, James.F.X.Wellehan at (Jim Wellehan) writes:
> In article <1993Nov12.170828.353 at>
> mkennedy at (Martin Kennedy) writes:
>> Don't forget that there are endogenous mammalian (including human) reverse
>> transcriptases
> Are these thought to be just remnants left behind in the genome by
> retroviruses, or is there a postulated function for them?
> Jim

I don't know the answer to that Jim;  the one paper I can lay my hands on
(Mathias et al., '91; Science  254 p1808) describes a reverse transcriptase
from the human L1 repetitive DNA sequence.  These things are "retrotransposons"
or maybe could be considered to be endogenous retroviruses.  Whether they 
evolved within the human genome, or derived from exogenous retroviruses isn't 
clear to me.  Mathias et al. show the L1 RT is functional, and proposed that 
it may be involved in the dispersion of many mammalian retroelements. Having
said that, most L1 elements don't encode functional RT; this particular RT gene
came from an L1 element that was shown to undergo a recent transposition event.



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