<p>This entry represents DNA polymerase eta from the Y-family of DNA polymerases. Y-family polymerases are characterised by their low-fidelity synthesis on undamaged DNA templates and by their ability to traverse replication-blocking lesions. By contrast, high-fidelity polymerases (such as DNA polymerase III) are sensitive to distortions in the DNA template. As a result, Y-family polymerases can extend primer strands across DNA strand lesions that would otherwise stall replicative polymerases. Organisms can contain more than one Y-family polymerase, each with a unique DNA damage bypass and fidelity profile. For example, humans posses four Y-family polymerases: DNA polymerases kappa, iota, eta and Rev1. Y-family polymerases show no homology to DNA polymerases from the A-, B-, C-, D- or X-families [<cite idref="PUB00026570"/>].</p><p>Mutations in DNA polymerase eta are responsible for an inherited disorder, the variant form of xeroderma pigmentosum [<cite idref="PUB00044579"/>]. These account for about a fifth of xeroderma pigmentosum patients, where the NER pathway is normal but there is a defect in their ability to replicate UV-damaged DNA. The crystal structure of DNA polymerase eta has been determined [<cite idref="PUB00026401"/>].</p> DNA polymerase eta