Ku is associated with the telomere in mammals

Telomeres are specialized DNA/protein complexes that comprise the ends of e ukaryotic chromosomes. The highly expressed Ku heterodimer, composed of 70 and 80 K-d subunits (Ku70 and Ku80), is the high-affinity DNA binding compo nent of the DNA-dependent protein kinase. Ku is critical for nonhomologous DNA double-stranded break repair and site-specific recombination of V(D)J g ene segments. Ku also plays an important role in telomere maintenance in ye ast, Herein, we report, using an in vivo crosslinking method, that human an d hamster telomeric DNAs specifically coimmuno-precipitate with human Ku80 after crosslinking. Localization of Ku to the telomere does not depend on t he DNA-dependent protein kinase catalytic component, These findings suggest a direct link between Ku and the telomere in mammalian cells.