POLG
Encyclopedia
DNA polymerase subunit gamma is an enzyme
that in humans is encoded by the POLG gene
.
, called DNA polymerase gamma . The human POLG cDNA and gene were originally cloned mapped to chromosome 15, 15,q25. In eukaryotic cells, the 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 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.
, ataxia-neuropathy disorders, and dominant and recessive forms of progressive external ophthalmoplegia. A list of lists all published mutations in the POLG coding region and their associated disease can be found at the Human DNA Polymerase Gamma Mutation Database.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that in humans is encoded by the POLG gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Functions
POLG (alias, POLG1 or POLGa) is the gene that codes for the catalytic subunit of the mitochondrial DNA polymeraseDNA polymerase
A DNA polymerase is an enzyme that helps catalyze in the polymerization of deoxyribonucleotides into a DNA strand. DNA polymerases are best known for their feedback role in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand....
, called DNA polymerase gamma . The human POLG cDNA and gene were originally cloned mapped to chromosome 15, 15,q25. In eukaryotic cells, the mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
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 POLG2
POLG2
DNA polymerase subunit gamma-2, mitochondrial is an protein that in humans is encoded by the POLG2 gene. The POLG2 gene encodes a 55 kDa accessory subunit protein that imparts high processivity and salt tolerance to the catalytic subunit of DNA polymerase gamma, encoded by the POLG gene. -Further...
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.
Mutations
Mutations in the POLG gene are associated with several mitochondrial diseases, including Alpers' diseaseAlpers' disease
Alpers' disease, also called Alpers' syndrome, progressive sclerosing poliodystrophy, and progressive infantile poliodystrophy, is a progressive degenerative disease of the central nervous system that occurs mostly in infants and children. It is an autosomal recessive disorder that is sometimes...
, ataxia-neuropathy disorders, and dominant and recessive forms of progressive external ophthalmoplegia. A list of lists all published mutations in the POLG coding region and their associated disease can be found at the Human DNA Polymerase Gamma Mutation Database.