POLG

DNA polymerase subunit gamma is an is_associated_with::enzyme that in humans is encoded by the POLG is_associated_with::gene.

Function
POLG is a gene that codes for the catalytic subunit of the mitochondrial is_associated_with::DNA polymerase, called DNA polymerase gamma. The human POLG cDNA and gene were cloned and mapped to chromosome band 15q25. In is_associated_with::eukaryotic cells, the is_associated_with::mitochondrial DNA is replicated by DNA polymerase gamma, a trimeric protein complex composed of a catalytic subunit of 140 kDa encoded by the POLG gene and a dimeric accessory subunit of 55 kDa encoded by the is_associated_with::POLG2 gene. The catalytic subunit contains three enzymatic activities, a DNA polymerase activity, a 3’-5’ exonuclease activity that proofreads misincorporated nucleotides, and a 5’-dRP lyase activity required for base excision repair.

Clinical significance
Mutations in the POLG gene are associated with several is_associated_with::mitochondrial diseases, including is_associated_with::Alpers' disease, is_associated_with::ataxia-neuropathy disorders, and dominant and recessive forms of is_associated_with::progressive external ophthalmoplegia. A list of all published mutations in the POLG coding region and their associated disease can be found at the Human DNA Polymerase Gamma Mutation Database.