DNA polymerase lambda (pol lambda), also designated DNA polymerase lambda or Pol Beta2, is a low-fidelity polymerase which plays a role in both spontaneous and DNA damage-induced mutagenesis. Encoded by the POLL gene, pol lambda is a member of the DNA polymerase type-X family. Pol lambda extends primer-terminal mispairs opposite nondamaged DNA templates, suggesting that it may assist in extending mismatched base pairs during normal DNA replication. In addition, pol ?may play a role in the mutagenic bypass of T-T dimers. Proliferating cell nuclear antigen (PCNA), a protein essential to DNA replication, interacts with pol lambda and thus influences the ability of pol ?to synthesize DNA.