Paeschke Katrin, Simonsson Tomas, Postberg Jan, Rhodes Daniela, Lipps Hans Joachim
Institute of Cell Biology, University Witten/Herdecke, Stockumer Strasse 10, 58453 Witten, Germany.
Nat Struct Mol Biol. 2005 Oct;12(10):847-54. doi: 10.1038/nsmb982. Epub 2005 Sep 4.
Telomere end-binding proteins (TEBPs) bind to the guanine-rich overhang (G-overhang) of telomeres. Although the DNA binding properties of TEBPs have been investigated in vitro, little is known about their functions in vivo. Here we use RNA interference to explore in vivo functions of two ciliate TEBPs, TEBPalpha and TEBPbeta. Silencing the expression of genes encoding both TEBPs shows that they cooperate to control the formation of an antiparallel guanine quadruplex (G-quadruplex) DNA structure at telomeres in vivo. This function seems to depend on the role of TEBPalpha in attaching telomeres in the nucleus and in recruiting TEBPbeta to these sites. In vitro DNA binding and footprinting studies confirm the in vivo observations and highlight the role of the C terminus of TEBPbeta in G-quadruplex formation. We have also found that G-quadruplex formation in vivo is regulated by the cell cycle-dependent phosphorylation of TEBPbeta.
端粒末端结合蛋白（TEBPs）与端粒富含鸟嘌呤的突出端（G-突出端）结合。尽管已在体外研究了TEBPs的DNA结合特性，但对其在体内的功能却知之甚少。在这里，我们使用RNA干扰来探索两种纤毛虫TEBPs，即TEBPα和TEBPβ在体内的功能。沉默编码这两种TEBPs的基因的表达表明，它们在体内协同控制端粒处反平行鸟嘌呤四链体（G-四链体）DNA结构的形成。该功能似乎取决于TEBPα在将端粒附着于细胞核以及将TEBPβ募集至这些位点中的作用。体外DNA结合和足迹研究证实了体内观察结果，并突出了TEBPβ的C末端在G-四链体形成中的作用。我们还发现，体内G-四链体的形成受TEBPβ细胞周期依赖性磷酸化的调节。
