RPA facilitates telomerase activity at chromosome ends in budding and fission yeasts

Abstract

In Saccharomyces cerevisiae , the telomerase complex binds to chromosome ends and is activated in late S‐phase through a process coupled to the progression of the replication fork. Here, we show that the single‐stranded DNA‐binding protein RPA (replication protein A) binds to the two daughter telomeres during telomere replication but only its binding to the leading‐strand telomere depends on the Mre11/Rad50/Xrs2 (MRX) complex. We further demonstrate that RPA specifically co‐precipitates with yKu, Cdc13 and telomerase. The interaction of RPA with telomerase appears to be mediated by both yKu and the telomerase subunit Est1. Moreover, a mutation in Rfa1 that affects both the interaction with yKu and telomerase reduces the dramatic increase in telomere length of a rif1 Δ, rif2 Δ double mutant. Finally, we show that the RPA/telomerase association and function are conserved in Schizosaccharomyces pombe. Our results indicate that in both yeasts, RPA directly facilitates telomerase activity at chromosome ends.