SUMOylation regulates telomere length homeostasis by targeting Cdc13

Abstract

Telomere length homeostasis is an important aspect of telomere biology. Here we show that SUMOylation limits telomere length and targets multiple telomere proteins in Saccharomyces cerevisiae. A main target is Cdc13, which both positively and negatively regulates telomerase and confers end protection. We demonstrate that Cdc13 SUMOylation restrains telomerase functions by promoting Cdc13 interaction with the telomerase inhibitor Stn1, without affecting end protection. Mutation of the Cdc13 SUMOylation site (cdc13-snm) lengthens telomeres and reduces the Stn1 interaction, whereas Cdc13-SUMO fusion has the opposite effects. cdc13-snm's effect on telomere length is epistatic with stn1, but not with yku70, tel1 or est1 alleles, and is suppressed by Stn1 overexpression. Cdc13 SUMOylation peaks in early to mid S phase, prior to its known Cdk1-mediated phosphorylation, and the two modifications act antagonistically, suggesting that the opposite roles of Cdc13 in telomerase regulation can be separated temporally and regulated by distinct modifications.

SUMOylation regulates telomere length by targeting the shelterin subunit Tpz1 Tpp1 to modulate shelterin–Stn1 interaction in fission yeast

“…(Fig. 5A) (21). Furthermore, mutations in Polα also cause telomere elongation in budding yeast (33), and CST interacts with the Polα-primase complex (34,35).…”

“…Like the modification with ubiquitin (ubiquitylation) and other ubiquitin-like modifiers, SUMOylation is achieved with a distinct but evolutionarily conserved enzymatic cascade consisting of E1-activating, E2-conjugating, and E3 ligase enzymes (15)(16)(17). Factors involved in SUMOylation regulate recombinationbased telomere maintenance in mammals and budding yeast (18)(19)(20), and SUMOylation of Cdc13 promotes Cdc13-Stn1 interaction to restrain telomerase-dependent telomere elongation in budding yeast (21). In fission yeast, mutations of SUMO (Pmt3) or SUMO E3 ligase (Pli1) lead to long telomeres in a telomerase-dependent manner (22,23).…”

Replication of Telomeres and the Regulation of Telomerase

“…The phosphorylation of Cdc13 at T308 by Cdk1 in late S phase and G 2 favors the interaction of Cdc13 with Est1 rather than the competing interaction of Cdc13 with Stn1 -Ten1 (Li et al 2009). Another modification, Cdc13 SUMOylation, peaks in early to mid S phase (Hang et al 2011). Mutation of the SUMO site reduced the interaction with Stn1, promoting telomere elongation (Hang et al 2011).…”

“…Another modification, Cdc13 SUMOylation, peaks in early to mid S phase (Hang et al 2011). Mutation of the SUMO site reduced the interaction with Stn1, promoting telomere elongation (Hang et al 2011). Ku70/80 and Sir4 are other telomeric proteins modified by Siz2 E3 ligase-dependent SUMOylation, promoting perinuclear position of budding yeast telomeres (Ferreira et al 2011).…”

Posttranslational control of telomere maintenance and the telomere damage response

“…53 Interestingly, recent studies have found that prior to its phosphorylation, Cdc13 is target of SUMOylation. 54 SUMOylation of Cdc13 promotes its interaction with Stn1 and thereby restrains telomerase function, whereas mutation of the SUMOylation site in Cdc13 induces telomerase-mediated lengthening of telomeres due to weakening of the Cdc13-Stn1 interaction.…”