Twinkle helicase <i>(PEO1)</i> gene mutation causes mitochondrial DNA depletion

Sarzi, Emmanuelle; Goffart, Steffi; Serre, Valérie; Chrétien, Dominique; Slama, Abdelhamid; Münnich, Arnold; Spelbrink, Johannes N.; Rötig, Agnès

doi:10.1002/ana.21207

Cited by 156 publications

(110 citation statements)

References 27 publications

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“…Three related individuals who were homozygous for a mutation causing dual T457I substitutions developed severe hepatocerebral MDS and died within the first three years of life. The heterozygous parents and grandparents in this consanguineous pedigree were unaffected, which established a recessive mode of inheritance (45). Similarly, homozygous Y508C substitution results in IOSCA, which is a special form of MDS with a specific pattern of neuronal degeneration, and heterozygotes are unaffected (46).…”

Section: Discussionmentioning

confidence: 93%

Disease Variants of the Human Mitochondrial DNA Helicase Encoded by C10orf2 Differentially Alter Protein Stability, Nucleotide Hydrolysis, and Helicase Activity

Longley

Humble

Sharief

et al. 2010

Journal of Biological Chemistry

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Missense mutations in the human C10orf2 gene, encoding the mitochondrial DNA (mtDNA) helicase, co-segregate with mitochondrial diseases such as adult-onset progressive external ophthalmoplegia, hepatocerebral syndrome with mtDNA depletion syndrome, and infantile-onset spinocerebellar ataxia. To understand the biochemical consequences of C10orf2 mutations, we overproduced wild type and 20 mutant forms of human mtDNA helicase in Escherichia coli and developed novel schemes to purify the recombinant enzymes to near homogeneity. A combination of molecular crowding, non-ionic detergents, Mg 2؉ ions, and elevated ionic strength was required to combat insolubility and intrinsic instability of certain mutant variants. A systematic biochemical assessment of the enzymes included analysis of DNA binding affinity, DNA helicase activity, the kinetics of nucleotide hydrolysis, and estimates of thermal stability. In contrast to other studies, we found that all 20 mutant variants retain helicase function under optimized in vitro conditions despite partial reductions in DNA binding affinity, nucleotide hydrolysis, or thermal stability for some mutants. Such partial defects are consistent with the delayed presentation of mitochondrial diseases associated with mutation of C10orf2.Chronic disruption of mitochondrial function can result in a broad array of neuromuscular degenerative disorders known as mitochondrial diseases, including progressive external ophthalmoplegia (PEO), 2 Alpers syndrome, parkinsonism, and several complex ataxia neuropathy syndromes (1-3). A heritable form of PEO was first mapped to a chromosomal interval near position 10q24 in a Finnish pedigree (4). One molecular hallmark of PEO was the age-dependent accumulation of mtDNA deletions in somatic tissues of affected individuals, which suggested that this locus was needed for replication or maintenance of mtDNA (4). In 2001, autosomal dominant PEO with mtDNA deletions was shown to co-segregate with 11 different missense mutations in the C10orf2 gene (5), which encoded a protein containing predicted amino acid sequences homologous to portions of the bacteriophage T7 gene product 4 and other superfamily 4 DNA helicases (5, 6). Since that time, numerous reports have identified 23 additional missense mutations in C10orf2 associated with heritable mitochondrial diseases such as adPEO, hepatocerebral mtDNA depletion syndrome (MDS), and infantile-onset spinocerebellar ataxia (IOSCA) (7, 8) (see Fig. 1).Several lines of evidence more directly link C10orf2 function to maintenance of mtDNA. The C10orf2 gene product dynamically colocalizes with mtDNA in nucleoprotein structures known as mitochondrial nucleoids (5, 9), and knocking down expression of C10orf2 by RNAi results in the rapid decrease in mtDNA copy number in cultured human osteosarcoma (143B) cells (10). Overexpression of catalytic mutants and dominant disease variants of the mtDNA helicase in cultured human or Schneider cells results in stalled mtDNA replication or depletion of mtDNA (11-13), which emulates the...

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Section: Discussionmentioning

confidence: 93%

Disease Variants of the Human Mitochondrial DNA Helicase Encoded by C10orf2 Differentially Alter Protein Stability, Nucleotide Hydrolysis, and Helicase Activity

Longley

Humble

Sharief

et al. 2010

Journal of Biological Chemistry

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“…For example, the mitochondrion-specific polymerase ␥ and helicase Twinkle are important in mtDNA replication and when reconstituted in vitro together with the mitochondrial single-stranded DNA-binding protein function as a minimal mtDNA replisome (24). The importance of Twinkle has been underscored by the discovery of human mutations that lead to mitochondrial diseases, including progressive external ophthalmoplegia (35), mtDNA depletion syndrome (21,34), and infantile-onset spinocerebellar ataxia (20,30). In this report, we provide in vivo evidence that hDna2 accumulates within nucleoid structures upon the expression of mutant Twinkle proteins known to induce mtDNA stalling/ pausing.…”

Section: Discussionmentioning

confidence: 99%

Human Dna2 Is a Nuclear and Mitochondrial DNA Maintenance Protein

Duxin¹,

Dao²,

Martinsson

et al. 2009

Molecular and Cellular Biology

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Dna2 is a highly conserved helicase/nuclease that in yeast participates in Okazaki fragment processing, DNA repair, and telomere maintenance. Here, we investigated the biological function of human Dna2 (hDna2).Immunofluorescence and biochemical fractionation studies demonstrated that hDna2 was present in both the nucleus and the mitochondria. Analysis of mitochondrial hDna2 revealed that it colocalized with a subfraction of DNA-containing mitochondrial nucleoids in unperturbed cells. Upon the expression of disease-associated mutant forms of the mitochondrial Twinkle helicase which induce DNA replication pausing/stalling, hDna2 accumulated within nucleoids. RNA interference-mediated depletion of hDna2 led to a modest decrease in mitochondrial DNA replication intermediates and inefficient repair of damaged mitochondrial DNA. Importantly, hDna2 depletion also resulted in the appearance of aneuploid cells and the formation of internuclear chromatin bridges, indicating that nuclear hDna2 plays a role in genomic DNA stability. Together, our data indicate that hDna2 is similar to its yeast counterpart and is a new addition to the growing list of proteins that participate in both nuclear and mitochondrial DNA maintenance.DNA damage arises from errors in the replication process, as well as a myriad of intrinsic and extrinsic DNA-damaging agents that continually assault cells. Failure to efficiently repair DNA lesions leads to accumulation of mutations that contribute to numerous pathologies, including carcinogenesis. In addition to genomic DNA, mitochondrial DNA (mtDNA) is subject to damage that requires repair to maintain integrity. For these reasons, it is not surprising that DNA replication and repair proteins display significant plasticity that allows participation in several divergent replication and repair processes. In addition, numerous mechanisms, including alternative splicing, posttranslational modifications, or utilization of alternative translation initiation start sites, allow DNA replication and repair proteins such as Pif1, DNA ligase III, and APE1 to localize to the nucleus and the mitochondrion and participate in DNA replication and/or repair (9, 17, 25), thus ensuring genomic DNA and mtDNA integrity.Dna2 is an evolutionarily conserved helicase/nuclease enzyme. Originally discovered in Saccharomyces cerevisiae, Dna2 orthologs are found throughout the animal kingdom, including humans (5,22,28). Early studies demonstrated that Dna2 functions in concert with Flap endonuclease 1 (FEN1) to remove long DNA flaps that form upon lagging-strand DNA replication (6). However, in contrast to FEN1, Dna2 is an essential gene in yeast, suggesting that other proteins, including FEN1, cannot compensate for its loss in DNA replication or that it possesses functions beyond its role in Okazaki fragment processing. In agreement with this, genetic and biochemical studies have implicated Dna2 in DNA double-strand break (DSB) repair, telomere regulation, and mitochondrial function (8,10,15,26,38,44,45).Analysis of Dna2 in yeas...

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“…Mutations in C10orf2 have been associated with variable phenotypes, including infantile-onset spinocerebellar ataxia [11,[93][94][95][96][97], autosomal dominant PEO [98][99][100], and hepatocerebral MDS [101,102]. Mutations in C10orf2 are a rare cause of early-onset hepatocerebral MDS that has been reported in 5 children from 2 unrelated families.…”

Section: C10orf2-related Hepatocerebral Mdsmentioning

confidence: 99%

“…mtDNA content is severely reduced in liver tissue. Prognosis is poor with 3 of the reported affected children dying between 2 and 3 years of age [101,102].…”

Section: C10orf2-related Hepatocerebral Mdsmentioning

confidence: 99%

Mitochondrial DNA Depletion Syndromes: Review and Updates of Genetic Basis, Manifestations, and Therapeutic Options

2013

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Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are a genetically and clinically heterogeneous group of autosomal recessive disorders that are characterized by a severe reduction in mtDNA content leading to impaired energy production in affected tissues and organs. MDS are due to defects in mtDNA maintenance caused by mutations in nuclear genes that function in either mitochondrial nucleotide synthesis (TK2, SUCLA2,

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Twinkle helicase (PEO1) gene mutation causes mitochondrial DNA depletion

Cited by 156 publications

References 27 publications

Disease Variants of the Human Mitochondrial DNA Helicase Encoded by C10orf2 Differentially Alter Protein Stability, Nucleotide Hydrolysis, and Helicase Activity

Disease Variants of the Human Mitochondrial DNA Helicase Encoded by C10orf2 Differentially Alter Protein Stability, Nucleotide Hydrolysis, and Helicase Activity

Human Dna2 Is a Nuclear and Mitochondrial DNA Maintenance Protein

Mitochondrial DNA Depletion Syndromes: Review and Updates of Genetic Basis, Manifestations, and Therapeutic Options

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