title: Structure-function defects of the TWINKLE linker region in progressive external ophthalmoplegia.
abstract: TWINKLE is the helicase at the mitochondrial DNA (mtDNA) replication fork in mammalian cells. Mutations in the PEO1 gene, which encodes TWINKLE, cause autosomal dominant progressive external ophthalmoplegia (AdPEO), a disorder associated with deletions in mtDNA. Here, we characterized seven different AdPEO-causing mutations in the linker region of TWINKLE and we identified distinct molecular phenotypes. For some mutations, protein hexamerization and DNA helicase activity are completely abolished whereas others display more subtle effects. To better understand these distinct phenotypes, we constructed a molecular model of TWINKLE based on the three-dimensional structure of the bacteriophage T7 gene 4 protein. The structural model explains the molecular phenotypes and also predicts the functional consequences of other AdPEO-causing mutations. Our findings provide a molecular platform for further studies in cell- and animal-based model systems and demonstrate that knowledge of the bacteriophage T7 DNA replication machinery may be key to understanding the molecular and phenotypic consequences of mutations in the mtDNA replication apparatus.
authors.affiliation: Division of Metabolic Diseases, Department of Laboratory Medicine, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden.
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Korhonen
authors.forename: Vineet
authors.initials: V
authors.lastname: Pande
authors.forename: Teresa
authors.initials: T
authors.lastname: Holmlund
authors.forename: Géraldine
authors.initials: G
authors.lastname: Farge
authors.forename: Xuan Hoi
authors.initials: XH
authors.lastname: Pham
authors.forename: Lennart
authors.initials: L
authors.lastname: Nilsson
authors.forename: Maria
authors.initials: M
authors.lastname: Falkenberg
mesh_terms: D003001:Cloning, Molecular; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics*; D019915:DNA Primase / Q000737:chemistry; D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D006801:Humans; D024101:Mitochondrial Proteins; D008958:Models, Molecular; D009154:Mutation; D017246:Ophthalmoplegia, Chronic Progressive External / Q000235:genetics*; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D019915:DNA Primase; D004265:DNA Helicases; C431576:TWNK protein, human