FIG. 6.

Model of Cdc13 action at the telomeres. (A) The Cdc13 dimer, together with Stn1 and Ten1, binds the single-stranded telomeric overhang and caps the ends of the chromosomes, most likely in late S phase, when the telomeric overhangs are long. Cdc13N (blue spheres) caps the chromosome end, while the DBD (red ovals) binds telomeric DNA upstream of this site. (B) Cdc13 recruits telomerase (Est2; green claw shapes) to the telomeres via its interaction with Est1 (magenta spheres). (C) Cdc13N dissociates from the telomeric overhang to allow telomerase access to the 3′ end of the DNA and initiation of telomere replication, while Cdc13 remains tethered to the telomeres via the DBD-DNA interaction.