Intron loss?

[Martin Kennedy]

n article <CGED17.487 at dartvax.dartmouth.edu>, James.F.X.Wellehan at dartmouth.edu (Jim Wellehan) writes:
> In article <1993Nov12.170828.353 at chmeds.ac.nz>
> mkennedy at chmeds.ac.nz (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.

-- 
Cheers,

Martin

NNNN   NN  Martin A Kennedy (E-mail = mkennedy at chmeds.ac.nz)  ZZZZZZZ  
NN NN  NN       Cytogenetic and Molecular Oncology Unit          ZZZ
NN  NN NN           Christchurch School of Medicine            ZZZ
NN   NNNN              Christchurch, New Zealand              ZZZZZZZ
	      Phone (64-3)364-0880  Fax (64-3)364-0750