Fission yeast Pot1-Tpp1 protects telomeres and regulates telomere length

Telomeres are specialized chromatin structures that protect chromosomal ends. Protection of telomeres 1 ( Pot1) binds to the telomeric G- rich overhang, thereby protecting telomeres and regulating telomerase. Mammalian POT1 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 Pot1. Tpz1 binds to Ccq1 and the previously undiscovered protein Poz1 ( Pot1- associated in Schizosaccharomyces pombe), which protect telomeres redundantly and regulate telomerase in positive and negative manners, respectively. Thus, the Pot1- Tpz1 complex accomplishes its functions by recruiting effector molecules Ccq1 and Poz1. Moreover, Poz1 bridges Pot1- Tpz1 and Taz1- Rap1, 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.