A cryptic proofreading 3'----5' exonuclease associated with the polymerase subunit of the DNA polymerase-primase from Drosophila melanogaster.


The DNA polymerase-primase from Drosophila lacks 3'----5' exonuclease ...
The DNA polymerase-primase from Drosophila lacks 3'----5' exonuclease activity. However, a potent exonuclease can be detected after separating the 182-kDa polymerase subunit from the other three subunits of the enzyme (73, 60, and 50 kDa) by glycerol gradient sedimentation in the presence of 50% ethylene glycol. The exonuclease activity cosediments with the polymerase subunit, suggesting that the two activities reside in the same polypeptide. The 3'----5' exonuclease excises mismatched bases at the 3' termini of primed synthetic and natural DNA templates. Excision of a mispaired base at the 3' terminus occurs at a 10-fold greater rate than excision of the correctly paired base. When replication fidelity is measured by the bacteriophage phi X174 am3 reversion assay, the isolated polymerase subunit is at least 100-fold more accurate than either the intact polymerase-primase or a complex of the 182- and 73-kDa subunits. These results suggest that the 3'----5' exonuclease functions as a proofreading enzyme during Drosophila DNA replication in vitro and very likely in vivo.




new topics/pols set partial results complete validated


No results available for this paper.

Entry validated by:

Using Polbase tables:


Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).


It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.