The Ku protein complex is involved in length regulation of Drosophila telomeres.

Chromosome ends in Drosophila melanogaster can be elongated either by terminal attachment of the telomere-specific retrotransposons HeT-A and TART or by terminal gene conversion. Here we show that a decrease in Ku70 or Ku80 gene dosage causes a sharp increase in the frequency of HeT-A and TART attachments to a broken chromosome end and in terminal DNA elongation by gene conversion. Loss of Ku80 has more pronounced effects than loss of Ku70. However, lower Ku70 concentration reduces the stability of terminally deficient chromosomes. Our results suggest a role of the end-binding Ku complex in the accessibility and length regulation of Drosophila telomeres.