a question concerning dsRNAs

Thu May 19 17:48:26 EST 1994

I have a few comments to make on the following argument:

>Subj:	a question concerning ds RNAS

>It is my understanding that a cell commits suicide
>if there are double-stranded RNAs present inside.
>This is alleged to reflect a give-it-up strategy in
>case of viral infection, so that the spread of the
>virus is inhibited.  However, I believe most RNA viri
>are of the retrovirus class.  As such they would not

The retroviruses form a very small subset of the RNA viruses.
There are dozens of groups of RNA viruses which have no DNA
intermediate in both the animal and plant viruses. Also some
groups have a dsRNA genome; infact the vast majority of plant
viruses have a RNA genome.

>be generating any ds-RNA (RNA->DNA->RNA, rather
>than RNA->RNA).  I believe also that there are only
>a limited number of known RNA viri that do not have
>reverse transcriptase activity.  Therefore, can one

Actually there are a limited number of RNA viruses that
do have reverse transcriptase activity; most don't.

>assume that this strategy was so effective that those
>viri employing the ds-RNA phenotype just went (mostly)
>extinct, and this adamant reaction is vestigial?  What
>could explain this strong reaction to ds-RNA?  Was
>this type of viri more common in times past?  Is there
>some other explanation?  

It is possible to isolate dsRNA from plant tissue infected with
many kinds of RNA viruses. Whether this is artefactual is not
known for sure as far as I know; these dsRNAs are intermediates
of RNA replication. Many plant cells survive in the presence of 
this dsRNA intermediate.

>Periferally, what is the explanation for the existance
>of reverse transcriptase in eukaryotes?  Are we looking
>at viral contamination here, a leftover gene from some
>infection, or is there some use to eukaryotes for reverse

>sticknbd at miranda.cc.vanderbilt.edu


 Chris Rampitsch                       |       RAMPITSCH at BCRSSU.AGR.CA
 Dept. Plant Science, Univ. of BC      |       Phone (604) 494-7711
 Vancouver, British Columbia           |       Fax   (604) 494-0755
 Canada V6T 2A2                      _/\_
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