Holliday Junctions Formed from Human Telomeric DNA

Cells have evolved inherent mechanisms, like homologous recombination (HR), to repair damaged DNA. However, repairs at telomeres can lead to genomic instability, often associated with cancer. While most rapidly dividing cells employ telomerase, the others maintain telomere length through HR-dependen...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2018-11, Vol.140 (45), p.15366-15374
Main Authors: Haider, Shozeb, Li, Pengfei, Khiali, Soraia, Munnur, Deeksha, Ramanathan, Arvind, Parkinson, Gary N
Format: Article
Language:English
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Summary:Cells have evolved inherent mechanisms, like homologous recombination (HR), to repair damaged DNA. However, repairs at telomeres can lead to genomic instability, often associated with cancer. While most rapidly dividing cells employ telomerase, the others maintain telomere length through HR-dependent alternative lengthening of telomeres (ALT) pathways. Here we describe the crystal structures of Holliday junction intermediates of the HR-dependent ALT mechanism. Using an extended human telomeric repeat, we also report the crystal structure of two Holliday junctions in close proximity, which associate together through strand exchange to form a hemicatenated double Holliday junction. Our combined structural results demonstrate that ACC nucleotides in the C-rich lagging strand (5′-CTAACCCTAA-3′) at the telomere repeat sequence constitute a conserved structural feature that constrains crossover geometry and is a preferred site for Holliday junction formation in telomeres.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.8b08699