Maturation of telomere 3’-overhangs is linked to the replication stress response

Passage of the replication fork through telomeric repeats necessitates additional DNA processing by DNA repair factors, to regenerate the terminal 3’-overhang structure at leading telomeres. These factors are prevented from promoting telomeric recombination or fusion by an uncharacterized mechanism. Here we show that Rad5, a DNA helicase and ubiquitin ligase involved in the DNA damage tolerance pathway, participates in this mechanism. Rad5 is enriched at telomeres during telomere replication. Accelerated senescence seen in the absence of telomerase and Rad5, can be compensated for by a pathway involving the Rad51 recombinase and counteracted by the helicase Srs2. However, this pathway is only active at short telomeres. Instead, the ubiquitous activity of Rad5 during telomere replication is necessary for the proper reconstitution of the telomeric 3’-overhang, indicating that Rad5 is required to coordinate telomere maturation during telomere replication.Competing Interest StatementThe authors have declared no competing interest.