POLG2

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External IDs	GeneCards: [1]
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Species	Human	Mouse
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DNA polymerase subunit gamma-2, mitochondrial is a 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. Mutations in this gene result in autosomal dominant progressive external ophthalmoplegia with mitochondrial DNA deletions.

Structure

POLG2 is located on the q arm of chromosome 17 in position 23.3 and has 8 exons. POLG2, the protein encoded by this gene, contains a phosphoserine modified residue at p. 38 and a transit peptide. Its structure consists of 25 beta strands, 21 alpha helixes, and 8 turns.

Function

POLG2 encodes the processivity subunit of the mitochondrial DNA polymerase gamma. The encoded protein forms a heterotrimer containing one catalytic subunit and two processivity subunits. This protein enhances DNA binding, stimulates polymerase and exonuclease activity, and promotes processive DNA synthesis.

Catalytic activity

Deoxynucleoside triphosphate + DNA(n) = diphosphate + DNA(n+1)

Clinical significance

Mutations in POLG2 have been associated with progressive external ophthalmoplegia with mitochondrial DNA deletions. This disease results in progressive weakness of ocular muscles and levator muscle of the upper eyelid and patients with it may also manifest skeletal myopathy, ragged-red fibers and atrophy shown on muscle biopsy, cataracts, hearing loss, sensory axonal neuropathy, ataxia, depression, hypogonadism, and parkinsonism. This mutlisystemic disease has been linked to a G451E mutation that disrupts the DNA polymerase gamma subunits.

In patients with chronic hepatitis C, those carrying the DDX5 minor allele or DDX5-POLG2 haplotypes are thought to be at an increased risk of advanced fibrosis. It is important to note, however, that those carrying the CPT1A minor allele are believed to be at a decreased risk.

Interactions

POLG2 has been shown to have 32 binary protein-protein interactions including 19 co-complex interactions. POLG2 appears to interact with POLG.

Further reading

• Michiels S, Danoy P, Dessen P, Bera A, Boulet T, Bouchardy C, Lathrop M, Sarasin A, Benhamou S (August 2007). "Polymorphism discovery in 62 DNA repair genes and haplotype associations with risks for lung and head and neck cancers". Carcinogenesis. 28 (8): 1731–9. doi:10.1093/carcin/bgm111. PMID 17494052.
• Huang H, Shiffman ML, Cheung RC, Layden TJ, Friedman S, Abar OT, Yee L, Chokkalingam AP, Schrodi SJ, Chan J, Catanese JJ, Leong DU, Ross D, Hu X, Monto A, McAllister LB, Broder S, White T, Sninsky JJ, Wright TL (May 2006). "Identification of two gene variants associated with risk of advanced fibrosis in patients with chronic hepatitis C". Gastroenterology. 130 (6): 1679–87. doi:10.1053/j.gastro.2006.02.032. PMID 16697732.
• Longley MJ, Clark S, Yu Wai Man C, Hudson G, Durham SE, Taylor RW, Nightingale S, Turnbull DM, Copeland WC, Chinnery PF (June 2006). "Mutant POLG2 disrupts DNA polymerase gamma subunits and causes progressive external ophthalmoplegia". American Journal of Human Genetics. 78 (6): 1026–34. doi:10.1086/504303. PMC 1474082. PMID 16685652.
• Yakubovskaya E, Chen Z, Carrodeguas JA, Kisker C, Bogenhagen DF (January 2006). "Functional human mitochondrial DNA polymerase gamma forms a heterotrimer". The Journal of Biological Chemistry. 281 (1): 374–82. doi:10.1074/jbc.M509730200. PMID 16263719.
• Carrodeguas JA, Pinz KG, Bogenhagen DF (December 2002). "DNA binding properties of human pol gammaB". The Journal of Biological Chemistry. 277 (51): 50008–14. doi:10.1074/jbc.M207030200. PMID 12379656.
• Johnson AA, Tsai Y, Graves SW, Johnson KA (February 2000). "Human mitochondrial DNA polymerase holoenzyme: reconstitution and characterization". Biochemistry. 39 (7): 1702–8. doi:10.1021/bi992104w. PMID 10677218.
• Carrodeguas JA, Bogenhagen DF (March 2000). "Protein sequences conserved in prokaryotic aminoacyl-tRNA synthetases are important for the activity of the processivity factor of human mitochondrial DNA polymerase". Nucleic Acids Research. 28 (5): 1237–44. doi:10.1093/nar/28.5.1237. PMC 102604. PMID 10666468.
• Lim SE, Longley MJ, Copeland WC (December 1999). "The mitochondrial p55 accessory subunit of human DNA polymerase gamma enhances DNA binding, promotes processive DNA synthesis, and confers N-ethylmaleimide resistance". The Journal of Biological Chemistry. 274 (53): 38197–203. doi:10.1074/jbc.274.53.38197. PMID 10608893.

This article incorporates text from the United States National Library of Medicine, which is in the public domain.