Fission Yeast Pot1-Tpp1 Protects Telomeres and Regulates Telomere Length

摘要

Telomeres are specialized chromatin structures that protect chromosomal ends. Protection of telomeres 1 (PotI) binds to the telomeric G-rich overhang, thereby protecting telomeres and regulating telomerase. Mammalian P0Tl and TPP1 interact and constitute part of the six-protein shelterin complex. Here we report that Tpz1, the TPP1 homolog in fission yeast, forms a complex with Potl. Tpzl binds to Ccql and the previously undiscovered protein Pozl (Potl-associated in Schizosaccharomyces pombe), which protect telomeres redundantly and regulate telomerase in positive and negative manners, respectively. Thus, the Potl-Tpzl complex accomplishes its functions by recruiting effector molecules Ccql and Pozl. Moreover, Pozl bridges Potl-Tpzl and Tazl-Rapl, thereby connecting the single-stranded and double-stranded telomeric DNA regions. Such molecular architectures are similar to those of mammalian shelterin, indicating that the overall DNA-protein architecture is conserved across evolution.