Protection of Arabidopsis Blunt-Ended Telomeres is Mediated by a Physical Association with the Ku Heterodimer

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VALUCHOVÁ Soňa FULNEČEK Jaroslav PROKOP Zbyněk STOLT-BERGNER P. JANOUSKOVA e HOFR Ctirad ŘÍHA Karel

Druh Článek v odborném periodiku
Časopis / Zdroj THE PLANT CELL ONLINE
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Popis Telomeres form specialized chromatin that protects natural chromosome termini from being recognized as DNA double-strand breaks. Plants possess unusual blunt-ended telomeres that are unable to form tloops or complex with single-strand DNA binding proteins, raising the question of the mechanism behind their protection. We have previously suggested that blunt-ended telomeres in Arabidopsis thaliana are protected by Ku, a DNA repair factor with a high affinity for DNA ends. In non-homologous end joining (NHEJ), Ku loads onto broken DNA via a channel consisting of positively charged amino acids. Here, we demonstrate that while association of Ku with plant telomeres also depends on this channel, Ku’s requirements for DNA binding differ between DNA repair and telomere protection. We show that a Ku complex proficient in DNA loading but impaired in translocation along DNA is able to protect bluntended telomeres but is deficient in DNA repair. This suggests that Ku physically sequesters blunt-ended telomeres within its DNA binding channel, shielding them from other DNA repair machineries.

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