An error-correcting proofreading exonuclease-polymerase that copurifies with DNA-polymerase-alpha-primase.

Abstract:

A DNA polymerase with a 3'-to 5'-exonuclease that copurified with polymerase-primase from calf thymus was purified and extensively characterized. Its exonuclease degraded single-stranded DNA from 3' to 5' in a strictly distributive manner. On synthetic template-primer junctions, 3'-terminal mispairs were excised with a 10- to 20-fold preference over correctly paired nucleotides. In comparison to the 3'- to 5'-exonuclease the DNA polymerase activity was rather low. The ratio of nucleotides incorporated to nucleotides excised was in the order of 1 to 3 nucleotide insertions per excision, suggesting that net forward DNA synthesis is not the primary role of this DNA polymerase. DNA synthesis was performed with a low processivity in the presence and absence of PCNA. Both the polymerase and exonuclease activities were inhibited to a comparable extent by AMP. Thus, the exonuclease-polymerase might represent a novel DNA polymerase that we tentatively designate as DNA polymerase zeta. Possible benefits of DNA polymerase zeta in the process of error correction and the apparent dichotomy of an built-in proofreading activity for the processive DNA polymerases gamma, delta, and epsilon and an obviously external proofreading function for the less processive animal cell DNA polymerases alpha and beta are discussed.

Polymerases:

Topics:

Status:

new topics/pols set partial results complete validated

Results:

No results available for this paper.

Entry validated by:

Log in to edit reference All References

Using Polbase tables:

Sorting:

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).

Filtering:

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.