title: Large-scale expansions of Friedreich's ataxia GAA repeats in yeast.
abstract: Large-scale expansions of DNA repeats are implicated in numerous hereditary disorders in humans. We describe a yeast experimental system to analyze large-scale expansions of triplet GAA repeats responsible for the human disease Friedreich's ataxia. When GAA repeats were placed into an intron of the chimeric URA3 gene, their expansions caused gene inactivation, which was detected on the selective media. We found that the rates of expansions of GAA repeats increased exponentially with their lengths. These rates were only mildly dependent on the repeat's orientation within the replicon, whereas the repeat-mediated replication fork stalling was exquisitely orientation dependent. Expansion rates were significantly elevated upon inactivation of the replication fork stabilizers, Tof1 and Csm3, but decreased in the knockouts of postreplication DNA repair proteins, Rad6 and Rad5, and the DNA helicase Sgs1. We propose a model for large-scale repeat expansions based on template switching during replication fork progression through repetitive DNA.
authors: Department of Biology, Tufts University, Medford, MA 02155, USA.
authors: Alexander A
authors: AA
authors: Shishkin
authors: Irina
authors: I
authors: Voineagu
authors: Robert
authors: R
authors: Matera
authors: Nicole
authors: N
authors: Cherng
authors: Brook T
authors: BT
authors: Chernet
authors: Maria M
authors: MM
authors: Krasilnikova
authors: Vidhya
authors: V
authors: Narayanan
authors: Kirill S
authors: KS
authors: Lobachev
authors: Sergei M
authors: SM
authors: Mirkin
mesh_terms: D004261:DNA Replication / Q000235:genetics; D005621:Friedreich Ataxia / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D007438:Introns / Q000235:genetics; D033862:Iron-Binding Proteins / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D018911:Trinucleotide Repeats / Q000235:genetics*; D015003:Yeasts / Q000235:genetics*; D000096923:Frataxin
chemical_list: D033862:Iron-Binding Proteins; D012333:RNA, Messenger; D000096923:Frataxin