Large-scale contractions of Friedreich’s ataxia GAA repeats in yeast occur during DNA replication due to their triplex-forming ability

Alexandra N. Khristich, Jillian F. Armenia, Robert M. Matera, Anna A. Kolchinski, and Sergei M. Mirkin; PNAS first published January 7, 2020 Doi:10.1073/pnas.1913416117

Expansions of GAA repeats cause a severe hereditary neurodegenerative disease, Friedreich’s ataxia. In this study, we characterized the mechanisms of GAA repeat contractions in a yeast experimental system. These mechanisms might, in the long run, aid development of a therapy for this currently incurable disease. We show that GAA repeats contract during DNA replication, which can explain the high level of somatic instability of this repeat in patient tissues. We also provided evidence that a triple-stranded DNA structure is at the heart of GAA repeat instability. This discovery highlights the role of triplex DNA in genome instability and human disease.

Large-scale contractions of Friedreich’s ataxia GAA repeats in yeast occur during DNA replication due to their triplex-forming ability