FIGURE 1: Rif1 is a multi-faceted genome maintenance factor. At origins of replication, Rif1 attenuates origin firing by recruiting PP1/Glc7, which reverses activating Mcm4 and Sld3 phosphorylation mediated by DDK (see Box 1). At DSBs, Rif1 tightly encases the break ends, gating access of the end-resection machinery. As a result, DSB ends are stabilized, promoting their re-ligation by NHEJ. At budding yeast telomeres, Rif1 forms part of an interlinked telosome protein meshwork with Rap1 and Rif2, underpinning telomere architecture and function. In addition, direct Rif1-DNA interactions are required to counteract telomerase and inadvertent checkpoint activation at chromosome ends (see text for details). CST denotes the Cdc13-Stn1-Ten1 complex bound to ssDNA telomeric overhangs.