Weeding out functions for Ku

The Ku70/80 heterodimer is essential for the non-homologous end-joining type of repair of DNA double-strand breaks and for 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 (Proc Natl Acad Sci USA 2002, 10.1073/pnas.0236128100). They analysed plants lacking both KU70 and TERT (encoding the catalytic subunit of telomerase). The ku70/tert double mutants no longer exhibited the telomere elongation seen in ku70single mutants. Double-mutants had accelerated telomere shortening, reflecting a defect in C-strand maintenance, and had proliferative defects, but there was no evidence for chromosome-end fusion events.