Polymerase stringency

m griep mgriep at unlinfo.unl.edu
Tue May 24 08:52:58 EST 1994

pjc at waikato.ac.nz (Peter Charlton) writes:

>Can anyone give me any pointers to information on the selectivity or stringency
>of DNA and RNA polymerases for nucleotides other than the standard five
>(G,C,A,T,U). I guess 5-hydroxymethylcytidine can be recognised, since it occurs
>in some viral genomes. Can it be incorporated opposite a G; if 5-HMC were
>supplied to an in vitro DNA synthesis would it be utilised by the polymerase?
>What other modified nucleotides could be recognised succesfully?

>Any replies gratefully received,

DNA and RNA polymerases do not appear to recognize 
the actual bases or sugars of the (d)NTPs.  A wide
variety of chemical modifications to the NTPs will
be incorporated by the polymerase into chain in vitro.
Fidelity of incorporation seems to have more to do
with the base pair size than its actual sequence.
That is, A-T has the same overall width as G-C.
An interesting demonstration of what I'm saying is
in the Nature, vol 343, p.33 article by Benner and 
workers in which they synthesized "new" bases and 
showed that they could be incorporated into chains
by RNA and DNA polymerases.

Mark Griep
Department of Chemistry      ____   ____      __________________
Center for Biotechnology    |    | /    |    |                  \_
University of Nebraska      |    |/     |    |                    \

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