Intravirion nucleic acid replication
ohungnes at bioslave.uio.no
Sun Aug 27 17:03:52 EST 1995
Karl Fischer (kfischer at gpu.srv.ualberta.ca) wrote:
: The virus we work with (hepatitis B virus) encapsidates a pregenomic RNA
: which is reverse transcribed WITHIN the virus capsid to give the partially
: double-stranded DNA genome.
: My question is - What other viruses demonstrate intravirion replication of
: their genome as opposed to ex virion synthesis then encapsidation?
: I suspect caulimovirus (another pararetrovirus) does this but am curious
: as to what other viruses utilize this strategy.
It seems that some retroviruses perform partial reverse
transcription in the virions (somebody in Gallo's group
has been working on this, I think). I would guess that
depletion of dNTPs is a limiting factor here, as particle
maturation happens more or less simultaneously with, or after,
virion budding. I wouldn't be surprised if the reverse
transcription reaction of the incoming genome also happens
within a more or less complete nucleocapsid complex.
Maybe the crucial difference between hepadna- and retrovirus
reverse transcription is that the hepadnaviruses assemble a structure
with active polymerase and RNA genome at a stage when dNTPs from
the mother cell are still freely available, whereas the retroviruses
Do you think there is a connection between this and the funny way
hepadnaviruses primes their first-strand synthesis? This quite
effectively males sure that nothing but virus RNA is used as template,
I would think. A prematurely activated retrovirus RT would perhaps
be too promiscuous. As far as I've understood, you can't assay
hepadnavirus RT activity using an exogenous template.
OTOH, the synthesis of the viral RNA genome, which is the real
multiplication step, is catered for by the cellular RNA pol
2 and takes place outside any virus-generated structures in both
hepadna- and retroviruses, I guess.
Olav Hungnes olav.hungnes at embnet.uio.no
National Institute Phone (+47)22042200
of Public Health FAX (+47)22353605
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