title: Mutually exclusive binding of telomerase RNA and DNA by Ku alters telomerase recruitment model.
abstract: In Saccharomyces cerevisiae, the Ku heterodimer contributes to telomere maintenance as a component of telomeric chromatin and as an accessory subunit of telomerase. How Ku binding to double-stranded DNA (dsDNA) and to telomerase RNA (TLC1) promotes Ku's telomeric functions is incompletely understood. We demonstrate that deletions designed to constrict the DNA-binding ring of Ku80 disrupt nonhomologous end-joining (NHEJ), telomeric gene silencing, and telomere length maintenance, suggesting that these functions require Ku's DNA end-binding activity. Contrary to the current model, a mutant Ku with low affinity for dsDNA also loses affinity for TLC1 both in vitro and in vivo. Competition experiments reveal that wild-type Ku binds dsDNA and TLC1 mutually exclusively. Cells expressing the mutant Ku are deficient in nuclear accumulation of TLC1, as expected from the RNA-binding defect. These findings force reconsideration of the mechanisms by which Ku assists in recruiting telomerase to natural telomeres and broken chromosome ends. PAPERCLIP:
authors.affiliation: Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado Biofrontiers Institute, Boulder, CO 80309-0215, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Pfingsten
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Goodrich
authors.forename: Cornelius
authors.initials: C
authors.lastname: Taabazuing
authors.forename: Faissal
authors.initials: F
authors.lastname: Ouenzar
authors.forename: Pascal
authors.initials: P
authors.lastname: Chartrand
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Cech
mesh_terms: D001483:Base Sequence; D059766:DNA End-Joining Repair; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012313:RNA / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D017384:Sequence Deletion; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism*; D016615:Telomere / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C081647:high affinity DNA-binding factor, S cerevisiae; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase