title: Electron microscopic visualization of telomerase from Euplotes aediculatus bound to a model telomere DNA.
abstract: Binding of the telomerase ribonucleoprotein from the ciliate Euplotes aediculatus to telomeric DNA in vitro has been examined by electron microscopy (EM). Visualization of the structures that formed revealed a globular protein complex that localized to the DNA end containing the E. aediculatus telomere consensus 3'-single-strand T(4)G(4)T(4)G(4)T(4)G(2) overhang. Gel filtration confirmed that purified E. aediculatus telomerase is an active dimer in solution, and comparison of the size of the DNA-associated complex with apoferritin suggests that E. aediculatus telomerase binds to a single telomeric 3'-end as a dimer. Up to 43% of the telomerase-DNA complexes appeared by EM to involve tetramers or larger multimers of telomerase in association with two or more DNA ends. These data provide the first direct evidence that telomerase is a functional dimer and suggest that two telomerase ribonucleoprotein particles cooperate to elongate each Euplotes telomere in vivo.
authors.affiliation: Lineberger Comprehensive Cancer Center and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Fouché
authors.forename: Ian K
authors.initials: IK
authors.lastname: Moon
authors.forename: Brian R
authors.initials: BR
authors.lastname: Keppler
authors.forename: Jack D
authors.initials: JD
authors.lastname: Griffith
authors.forename: Michael B
authors.initials: MB
authors.lastname: Jarstfer
mesh_terms: D000818:Animals; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D016812:Euplotes / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D016615:Telomere / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; D019098:Telomerase