title: Telomerase recruitment by the telomere end binding protein-beta facilitates G-quadruplex DNA unfolding in ciliates.
abstract: The telomeric G-overhangs of the ciliate Stylonychia lemnae fold into a G-quadruplex DNA structure in vivo. Telomeric G-quadruplex formation requires the presence of two telomere end binding proteins, TEBPalpha and TEBPbeta, and is regulated in a cell-cycle dependent manner. Unfolding of this structure in S phase is dependent on the phosphorylation of TEBPbeta. Here we show that TEBPbeta phosphorylation is necessary but not sufficient for a G-quadruplex unfolding rate compatible with telomere synthesis. The telomerase seems to be actively involved in telomeric G-quadruplex DNA structure unfolding in vivo. Significantly, the telomerase is recruited to telomeres by phosphorylated TEBPbeta, and hence telomerase recruitment is cell-cycle regulated through phosphorylation. These observations allow us to propose a model for the regulation of G-quadruplex unfolding and telomere synthesis during the cell cycle.
authors.affiliation: Institute of Cell Biology, University Witten/Herdecke, Stockumer Strasse 10, 58453 Witten, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Paeschke
authors.forename: Stefan
authors.initials: S
authors.lastname: Juranek
authors.forename: Tomas
authors.initials: T
authors.lastname: Simonsson
authors.forename: Anne
authors.initials: A
authors.lastname: Hempel
authors.forename: Daniela
authors.initials: D
authors.lastname: Rhodes
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Lipps
mesh_terms: D000818:Animals; D002453:Cell Cycle; D016798:Ciliophora; D054856:G-Quadruplexes; D009690:Nucleic Acid Conformation; D010766:Phosphorylation; D021381:Protein Transport; D019098:Telomerase / Q000378:metabolism*; D016615:Telomere; D034501:Telomere-Binding Proteins / Q000378:metabolism*
chemical_list: D034501:Telomere-Binding Proteins; D019098:Telomerase