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Keywords:

  • CST;
  • Stn1;
  • telomeres;
  • Tpz1;
  • SUMO

Abstract

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.

Synopsis

Thumbnail image of graphical abstract

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.