Elongation of the telomeric overhang by telomerase is counteracted by synthesis of the complementary strand by the CST complex, CTC1(Cdc13)/Stn1/Ten1. Interaction of budding yeast Stn1 with overhang-binding Cdc13 is increased by Cdc13 SUMOylation. Human and fission yeast CST instead interact with overhang-binding TPP1/POT1. We show that the fission yeast TPP1 ortholog, Tpz1, is SUMOylated. Tpz1 SUMOylation restricts telomere elongation and promotes Stn1/Ten1 telomere association, and a SUMO-Tpz1 fusion protein has increased affinity for Stn1. Our data suggest that SUMO inhibits telomerase through stimulation of Stn1/Ten1 action by Tpz1, highlighting the evolutionary conservation of the regulation of CST function by SUMOylation.
This study shows that Tpz1 SUMOylation in fission yeast is required for Stn1/Ten1 recruitment to telomeres and, thus, prevention of telomere elongation. Tpz1 SUMOylation increases its affinity for Stn1.
- Fission yeast telomere protein Tpz1, the TPP1 ortholog, is SUMOylated at lysine 242.
- Tpz1 SUMOylation limits telomere elongation and the association of telomerase with telomeres.
- As SUMOylation of budding yeast Cdc13, Tpz1 SUMOylation is required for efficient recruitment of Stn1/Ten1 to telomeres.
- SUMO-mediated recruitment of Stn1 is proposed to be a conserved feature within the CST complex.