Pfu-spiked cycle sequencing

Robert Preston rapr at MED.PITT.EDU
Thu Jun 9 09:06:17 EST 1994

Forwarded message:
> From: ohungnes at (Olav Hungnes)
> Robert Preston (rapr at MED.PITT.EDU) wrote:
> : Forwarded message:
> : > From: jspaffor at (J. David Spafford)
> : > [edit] 
> : > I use an ABI sequencer with a 9600 Perkin Elmers PCR machine.  Usually I can
> : > get up to 400 bp of good sequence and no more.  ABI provides AmpliTaq with
> : > their sequencing kit.  Would I get longer sequence if I spike it with Pfu
> : > DNA polymerase?
> : > J. David Spafford
> : You mean, do Wayne Barnesian Long-PCR factors come into play in the 400-700
> : bp range?  Interesting possibility.  Well worth an experiment.  Be sure to
> : post the results!
> : Rob Preston
> I don't know much about Pfu, but in the good old days of Vent I was told 
> that the 5'to 3' proofreading exonuclease activity would eat at all kinds of 
> non-base-paired 3' termini, even the primers to some extent. Isn't there 
> a chance that the Pfu will start degrading dideoxy-terminated molecules 
> from their 3' end and make a mess of the entire reaction?
> Olav
> --
There seems to be some confusion about 5' and 3' there, Olav, but more
to the point, why would dideoxyterminated strands be degraded? They are
not mis-paired (we use them for sequencing, after all), so presumably they
would not be editor substrates.  They just can't be extended further.  In
any case, even if they were edited sometimes, further synthesis on the
same strand would likely fix things up (for fluor primer chemistry) or it
would be irrelevant (for fluor terminator chemistry).  Even MORE to the point,
one experiment (well, maybe two or three tries, if it's as simple as these)
is worth far more than any of this verbal rationalization..
Rob Preston
rapr at med.pitt.edyu

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