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

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 Delta, rif2 Delta 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. The EMBO Journal (2012) 31, 2034-2046. doi: 10.1038/emboj.2012.40; Published online 21 February 2012 Subject Categories: genome stability & dynamics