Telomerase recruitment by the telomere end binding protein-beta facilitates G-quadruplex DNA unfolding in ciliates.
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.
Paeschke
Katrin
K
Institute of Cell Biology, University Witten/Herdecke, Stockumer Strasse 10, 58453 Witten, Germany.
Juranek
Stefan
S
Simonsson
Tomas
T
Hempel
Anne
A
Rhodes
Daniela
D
Lipps
Hans Joachim
HJ
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*
D034501:Telomere-Binding Proteins; D019098:Telomerase