Specific points on p53 exonuclease function
rgj20 at HERMES.CAM.AC.UK
Thu Nov 14 08:06:10 EST 1996
Earlier this month I posted a request for information regarding the
possibility of p53 being an exonuclease for a critical review of
Mummenbrauer at al., p53 exhibits 3'-5' exonucleases activity, Cell 85. I
realise that I shouldn't have made such a general request and now have
some specific questions regarding the paper.
1. Mummenbrauer et al use a 30-mer oligonucleotide for their gel assays of
exonuclease activty. This sequence was found to be bound by p53 by
Foord et al.(1993) when part of a ds DNA fragment. Why therefore did
Mummenbrauer use the sequence as a ssDNA oligo and not dsDNA?
2. Why did the researchers use ssDNA oligo for the gell assays and ds poly
dA.dT for the filter binding assays?
3. If the exonuclease activity is seen with the ss 30-mer oligo then why
doesn't ss poly dA DNA compete with the ds poy dA.dT in their assay?
4. It is stated in table 2 of the paper that p53 is acting as tetramer
when behaving as an exonuclease (though no evidence is put forward) but
later on it is shown that the core domain on its own posseses
exonuclease activity. This contrasts with the fact that core domain was
shown by Pavelitch et al.(1993) to be a monomer in solution.
Thanks for your help,
King's College, Cambridge, UK.
PS Any information I recieve from this newsgroup that I use in my review
will of course be referenced to whoever posted it.
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