SUMOylation regulates telomere length by targeting the shelterin subunit Tpz1Tpp1 to modulate shelterin-Stn1 interaction in fission yeast

Telomeres protect DNA ends of linear eukaryotic chromosomes from degradation and fusion through the recruitment of telomerase. We previously found that SUMOylation negatively regulates telomere extension; however, how SUMOylation limits telomere extension has remained unknown until now. Here we provide major mechanistic insights into how the SUMOylation pathway collaborates with shelterin and Stn1-Ten1 complexes to regulate telomere length. We establish that SUMOylation of the shelterin subunit TPP1 homolog in Schizosaccharomyces pombe (Tpz1) prevents telomerase accumulation at telomeres by promoting recruitment of Stn1-Ten1 to telomeres in S-phase. Thus, our findings establish that Tpz1 not only contributes to telomerase recruitment via its interaction with Ccq1-Est1, but also contributes to the negative regulation of telomerase via its SUMOylation-mediated interaction with Stn1-Ten1.