Cell cycle-dependent spatial segregation of telomerase from sites of DNA damage.

Telomerase can generate a novel telomere at DNA double-strand breaks (DSBs), an event called de novo telomere addition. How this activity is suppressed remains unclear. Combining single-molecule imaging and deep sequencing, we show that the budding yeast telomerase RNA ( RNA) is spatially segregated to the nucleolus and excluded from sites of DNA repair in a cell cycle-dependent manner. Although RNA accumulates in the nucleoplasm in G1/S, Pif1 activity promotes RNA localization in the nucleolus in G2/M. In the presence of DSBs, RNA remains nucleolar in most G2/M cells but accumulates in the nucleoplasm and colocalizes with DSBs in cells, leading to de novo telomere additions. Nucleoplasmic accumulation of RNA depends on Cdc13 localization at DSBs and on the SUMO ligase Siz1, which is required for de novo telomere addition in cells. This study reveals novel roles for Pif1, Rad52, and Siz1-dependent sumoylation in the spatial exclusion of telomerase from sites of DNA repair.