The Ku70/80 heterodimer is essential for NHEJ (non-homologous end-joining) double-strand break DNA repair and telomere integrity. Inactivation of the KU70 gene in Arabidopsis results in telomere lengthening. In the Early Edition of the Proceedings of the National Academy of Sciences, Karel Riha and Dorothy Shippen report that Ku70 is important for the maintenance of the telomeric C strand and is a negative regulator of telomerase (PNAS, DOI:10.1073/pnas.0236128100, December 30, 2002).

Riha and Shippen analyzed plants lacking both KU70 and TERT (encoding the catalytic subunit of telomerase). The ku70tert double mutants no longer exhibited the telomere elongation seen in ku70 single mutants. Double-mutants displayed accelerated telomere shortening, reflecting a defect in C-strand maintenance. Also, double-mutants exhibited proliferative defects, but no evidence for chromosome end fusion events.

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