TPP1 (Est3 in yeast) is a component of the telomerase holoenzyme (shelterin complex), involved in telomere replication. It has been demonstrated that TPP1 dimerises and binds to DNA and RNA. Furthermore, TPP1 stimulates the dissociation of RNA/DNA hetero-duplexes [, ]. Yeast telomerase protein TPP1 (Est3) is a novel type of GTPase []. The key residues in Saccharomyces cerevisiae are an Asp at residue 86 and the Arg at residue 110. The Asp is totally conserved in the family, whereas the Arg is not so well conserved. The N-terminal of TPP1 is likely to be the binding surface for TIN2, whereas the C terminus probably binds to POT1, thereby tethering POT1 to the shelterin complex []. The complex bound to telomeric DNA increases the activity and processivity of the human telomerase core enzyme, thus helping to maintain the length of the telomeres [, , ].The human shelterin complex includes six proteins: telomere repeat binding factor 1 (TRF1); TRF2, repressor/activator protein 1 (RAP1); TRF1-interacting nuclear protein 2 (TIN2); TIN2-interacting protein 1 (TPP1), also known as ACD from adrenocortical dysplasia protein; and protection of telomeres 1 (POT1) [].
Adrenocortical dysplasia protein (acd, also known as TPP1) is a component of the shelterin complex (telosome) that is involved in the regulation of telomere length and protection. Shelterin associates with arrays of double-stranded TTAGGG repeats added by telomerase and protects chromosome ends; without its protective activity, telomeres are no longer hidden from the DNA damage surveillance and chromosome ends are inappropriately processed by DNA repair pathways []. It also forms a heterodimer with POT1 that increases the activity and processivity of the telomerase core enzyme [].This entry also includes fission yeast TPP1 homologue, Tpz1. Together with Pot1 it forms a complex that protects telomeres and regulates telomere length [].
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 []. 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. Two separate protein complexes are required for chromosome end protection in fission yeast while a two-subunit complex consisting of POT1 and TPP1 associates with telomeric ssDNA in humans. Protection of telomeres by multiple proteins with OB-fold domains is conserved in eukaryotic evolution [].This entry represents the C-terminal domain of Stn1 and consists of tandem winged helix-turn-helix motifs [, ].
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 []. 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. Two separate protein complexes are required for chromosome end protection in fission yeast while a two-subunit complex consisting of POT1 and TPP1 associates with telomeric ssDNA in humans. Protection of telomeres by multiple proteins with OB-fold domains is conserved in eukaryotic evolution [].This entry represents the C-terminal domain of Stn1 and consists of tandem winged helix-turn-helix motifs [, ].
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 []. 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 []. 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 [].This entry represent Ten1 from fungi.
