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Mutant POLG2 disrupts DNA polymerase γ subunits and causes progressive external ophthalmoplegia

Lookup NU author(s): Dr Steve Durham, Professor Robert Taylor, Professor Doug Turnbull, Professor Patrick Chinnery

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Abstract

DNA polymerase γ (pol γ) is required to maintain the genetic integrity of the 16,569-bp human mitochondrial genome (mtDNA). Mutation of the nuclear gene for the catalytic subunit of pol γ (POLG) has been linked to a wide range of mitochondrial diseases involving mutation, deletion, and depletion of mtDNA. We describe a heterozygous dominant mutation (c.1352G→A/p.G451E) in POLG2, the gene encoding the p55 accessory subunit of pol γ, that causes progressive external ophthalmoplegia with multiple mtDNA deletions and cytochrome c oxidase (COX)-deficient muscle fibers. Biochemical characterization of purified, recombinant G451E-substituted p55 protein in vitro revealed incomplete stimulation of the catalytic subunit due to compromised subunit interaction. Although G451E p55 retains a wild-type ability to bind DNA, it fails to enhance the DNA-binding strength of the p140-p55 complex. In vivo, the disease most likely arises through haplotype insufficiency or heterodimerization of the mutated and wild-type proteins, which promote mtDNA deletions by stalling the DNA replication fork. The progressive accumulation of mtDNA deletions causes COX deficiency in muscle fibers and results in the clinical phenotype. © 2006 by The American Society of Human Genetics. All rights reserved.


Publication metadata

Author(s): Longley MJ, Clark S, Man CYW, Hudson G, Durham SE, Taylor RW, Nightingale S, Turnbull DM, Copeland WC, Chinnery PF

Publication type: Article

Publication status: Published

Journal: American Journal of Human Genetics

Year: 2006

Volume: 78

Issue: 6

Pages: 1026-1034

ISSN (print): 0002-9297

ISSN (electronic): 1537-6605

Publisher: Cell Press

URL: http://dx.doi.org/10.1086/504303

DOI: 10.1086/504303

PubMed id: 16685652


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