DNA polymerase beta（POLB) is a member of the DNA polymerase type-X family. In eukaryotic cells， POLB performs base excision repair necessary for DNA maintenance， replication， recombination， and drug resistance. POLB has 2 separate domains； the larger is the polymerase domain itself， whereas a small basic N-terminal domain contains an AP lyase activity which excises the abasic sugar-phosphate residue at the strand break. POLB fills single nucleotide gaps in DNA produced by the base excision repair pathway of mammalian cells. POLB overexpression， as seen in some human tumors， could convene an increase in spontaneous mutagenesis.
