The Fidelity of DNA Polymerase β during Distributive and Processive DNA Synthesis

• Published in: The Journal of biological chemistry 1999-02, Vol.274 (6), p.3642-3650
• Main Authors: Osheroff, Wendy P., Jung, Hai Kwan, Beard, William A., Wilson, Samuel H., Kunkel, Thomas A.
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; DNA Polymerase beta - genetics; DNA Polymerase beta - metabolism; DNA Replication; DNA, Recombinant; Frameshift Mutation; Humans; Molecular Sequence Data; Rats; Recombinant Proteins - genetics; Recombinant Proteins - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.6.3642

During base excision repair, DNA polymerase β fills 1–6-nucleotide gaps processively, reflecting a contribution of both its 8- and 31-kDa domains to DNA binding. Here we report the fidelity of pol β during synthesis to fill gaps of 1, 5, 6, or >300 nucleotides. Error rates during distributive synthesis by recombinant rat and human polymerase (pol) β with a 390-base gap are similar to each other and to previous values with pol β purified from tissues. The base substitution fidelity of human pol β when processively filling a 5-nucleotide gap is similar to that with a 361-nucleotide gap, but “closely-spaced” substitutions are produced at a rate at least 60-fold higher than for distributive synthesis. Base substitution fidelity when filling a 1-nucleotide gap is higher than when filling a 5-nucleotide gap, suggesting a contribution of the 8-kDa domain to the dNTP binding pocket and/or a difference in base stacking or DNA structure imposed by pol β. Nonetheless, 1-nucleotide gap filling is inaccurate, even generating complex substitution-addition errors. Finally, the single-base deletion error rate during processive synthesis to fill a 6-nucleotide gap is indistinguishable from that of distributive synthesis to fill a 390-nucleotide gap. Thus the mechanism of processivity by pol β does not allow the enzyme to suppress template misalignments.