Stn1 and Ten1 are DNA-binding proteins with specificity for telomeric DNA substrates and both protect chromosome termini from unregulated resection and regulate telomere length. Stn1 complexes with Ten1 and Cdc13 to function as a telomere-specific replication protein A (RPA)-like complex [1]. These three interacting proteins associate with the telomeric overhang in budding yeast, whereas a single protein known as Pot1 (protection of telomeres-1) performs this function in fission yeast, and a two-subunit complex consisting of POT1 and TPP1 associates with telomeric ssDNA in humans. S.pombe has Stn1- and Ten1-like proteins that are essential for chromosome end protection. Stn1 orthologues exist in all species that have Pot1, whereas Ten1-like proteins can be found in all fungi. Fission yeast Stn1 and Ten1 localise at telomeres in a manner that correlates with the length of the ssDNA overhang, suggesting that they specifically associate with the telomeric ssDNA. Two separate protein complexes are required for chromosome end protection in fission yeast. Protection of telomeres by multiple proteins with OB-fold domains is conserved in eukaryotic evolution [2]. Ten1 is one of the three components of the CST complex, which, in conjunction with the Shelterin complex helps protect telomeres from attack by DNA-repair mechanisms [4].

1: RPA-like proteins mediate yeast telomere function. Gao H, Cervantes RB, Mandell EK, Otero JH, Lundblad V; Nat Struct Mol Biol. 2007;14:208-214. PMID:17293872

2: Protection of telomeres by a conserved Stn1-Ten1 complex. Martin V, Du LL, Rozenzhak S, Russell P; Proc Natl Acad Sci U S A. 2007;104:14038-14043. PMID:17715303

3: Telomere capping proteins are structurally related to RPA with an additional telomere-specific domain. Gelinas AD, Paschini M, Reyes FE, Heroux A, Batey RT, Lundblad V, Wuttke DS; Proc Natl Acad Sci U S A. 2009; [Epub ahead of print] PMID:19884503

4: The CST complex and telomere maintenance: the exception becomes the rule. Wellinger RJ; Mol Cell. 2009;36:168-169. PMID:19854124