Reverse transcriptase

[Patrick O'Neil]

On Thu, 25 May 1995, Rod Pennington wrote:

> >.............. The retroelements are considered old, defective viral
> >units, in any case.  They would then not be part of the original bacterial
> >genome, but riders that came along later and now, with the loss of ability
> >(or need) to encode capsid and bud (or lyse) the cell, can now be
>  
> I thought at least some retrotransposons *did* encode a capsid-like
> protein.  TY elements in yeast, for example.  These form encapsidated
> virus-like particals that, under EM, look like virions (this is from

  copia elements in Drosophila produce cytosolic virus-like particles that
accumulate but do not leave, thus producing what would appear to be capsid
proteins...but this is not bacteria.  Another Drosophila element, gypsy,
does not produce virus-like particles and neither do Ty elements in yeast 
or LINE elements in mammals.

A slight correction:  the bacterial elements, msDNA, are very unlike 
retroviruses in appearance.  They are extremely small and do not really 
code for anything within their limits, bordered by inverted repeats.  
I suppose it would be very difficult to tie this element to any 
retrovirus, unless it can be considered so degenerate as to be 
unrecognizable as a retroviral remnant.

Patrick