title: Super-resolution fluorescence imaging of telomeres reveals TRF2-dependent T-loop formation.
abstract: We have applied a super-resolution fluorescence imaging method, stochastic optical reconstruction microscopy (STORM), to visualize the structure of functional telomeres and telomeres rendered dysfunctional through removal of shelterin proteins. The STORM images showed that functional telomeres frequently exhibit a t-loop configuration. Conditional deletion of individual components of shelterin showed that TRF2 was required for the formation and/or maintenance of t-loops, whereas deletion of TRF1, Rap1, or the POT1 proteins (POT1a and POT1b) had no effect on the frequency of t-loop occurrence. Within the shelterin complex, TRF2 uniquely serves to protect telomeres from two pathways that are initiated on free DNA ends: classical nonhomologous end-joining (NHEJ) and ATM-dependent DNA damage signaling. The TRF2-dependent remodeling of telomeres into t-loop structures, which sequester the ends of chromosomes, can explain why NHEJ and the ATM signaling pathway are repressed when TRF2 is present.
authors.affiliation: Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY 10065, USA.
authors.forename: Ylli
authors.initials: Y
authors.lastname: Doksani
authors.affiliation: Department of Molecular and Cellular Biology, Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.|Department of Chemistry and Chemical Biology, Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.
authors.forename: John Y
authors.initials: JY
authors.lastname: Wu
authors.affiliation: Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY 10065, USA.
authors.forename: Titia
authors.initials: T
authors.lastname: de Lange
authors.affiliation: Department of Chemistry and Chemical Biology, Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.|Department of Physics, Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhuang
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D000089804:Shelterin Complex; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins; D035341:Telomeric Repeat Binding Protein 2 / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C507326:POT1 protein, mouse; D000089804:Shelterin Complex; C534796:TRF2 protein, mouse; D034501:Telomere-Binding Proteins; D035341:Telomeric Repeat Binding Protein 2