Overexpression of DNA polymerase beta results in an increased rate of frameshift mutations during base excision repair.
DNA polymerase beta (Pol beta) is important for the base excision repair (BER) pathway. Overexpression of Pol beta is frequently found in cancer cells and is thought to be associated with tumorigenesis. In this study, we examined BER fidelity in extracts derived from a human lymphoblastoid cell line that over expresses Pol beta compared to normal control cells. Using an in vitro mutagenesis assay, we found an increased rate of frameshift mutations arising during DNA repair in whole-cell extracts derived from the Pol beta-overexpressing cells. We demonstrate that the addition of excess Pol beta to a control cell extract enhances the mutagenic potential of the extract. Furthermore, using cell extracts and purified Pol beta, we demonstrate that the mechanism of frameshift formation involves slippage of Pol beta during the one-nucleotide gap-filling step of BER and that this slippage is fixed by strand-displacement synthesis stimulated by an excess of Pol beta.
Chan
Katie
K
Radiation and Genome Stability Unit, Medical Research Council, Harwell, Oxfordshire OX11 0RD, UK.
Houlbrook
Sue
S
Zhang
Qiu-Mei
QM
Harrison
Mark
M
Hickson
Ian D
ID
Dianov
Grigory L
GL
D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019951:DNA Polymerase beta / Q000378:metabolism / Q000494:pharmacology*; D004260:DNA Repair / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology; D004926:Escherichia coli; D016368:Frameshift Mutation / Q000187:drug effects* / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D009841:Oligonucleotides
D009841:Oligonucleotides; D019951:DNA Polymerase beta