title: Triple-helix structure in telomerase RNA contributes to catalysis.
abstract: Telomerase is responsible for replication of the ends of linear chromosomes in most eukaryotes. Its intrinsic RNA subunit provides the template for synthesis of telomeric DNA by the reverse-transcriptase (TERT) subunit and tethers other proteins into the ribonucleoprotein (RNP) complex. We report that a phylogenetically conserved triple helix within a pseudoknot structure of this RNA contributes to telomerase activity but not by binding the TERT protein. Instead, 2'-OH groups protruding from the triple helix participate in both yeast and human telomerase catalysis; they may orient the primer-template relative to the active site in a manner analogous to group I ribozymes. The role of RNA in telomerase catalysis may have been acquired relatively recently or, alternatively, telomerase may be a molecular fossil representing an evolutionary link between RNA enzymes and RNP enzymes.
authors.affiliation: Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, Campus Box 215, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Qiao
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Cech
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D006801:Humans; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D019098:Telomerase / Q000737:chemistry* / Q000378:metabolism; D015003:Yeasts
chemical_list: C422952:telomerase RNA; D012313:RNA; D019098:Telomerase