title: Structure and folding of the Tetrahymena telomerase RNA pseudoknot.
abstract: Telomerase maintains telomere length at the ends of linear chromosomes using an integral telomerase RNA (TER) and telomerase reverse transcriptase (TERT). An essential part of TER is the template/pseudoknot domain (t/PK) which includes the template, for adding telomeric repeats, template boundary element (TBE), and pseudoknot, enclosed in a circle by stem 1. The Tetrahymena telomerase holoenzyme catalytic core (p65-TER-TERT) was recently modeled in our 9 Å resolution cryo-electron microscopy map by fitting protein and TER domains, including a solution NMR structure of the Tetrahymena pseudoknot. Here, we describe in detail the structure and folding of the isolated pseudoknot, which forms a compact structure with major groove U•A-U and novel C•G-A+base triples. Base substitutions that disrupt the base triples reduce telomerase activity in vitro NMR studies also reveal that the pseudoknot does not form in the context of full-length TER in the absence of TERT, due to formation of a competing structure that sequesters pseudoknot residues. The residues around the TBE remain unpaired, potentially providing access by TERT to this high affinity binding site during an early step in TERT-TER assembly. A model for the assembly pathway of the catalytic core is proposed.
authors.affiliation: Department of Chemistry and Biochemistry, and Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA.
authors.forename: Darian D
authors.initials: DD
authors.lastname: Cash
authors.affiliation: Department of Chemistry and Biochemistry, and Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA feigon@mbi.ucla.edu.
authors.forename: Juli
authors.initials: J
authors.lastname: Feigon
mesh_terms: D001483:Base Sequence; D020134:Catalytic Domain; D006801:Humans; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D059370:RNA Folding; D016053:RNA, Protozoan / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D019098:Telomerase / Q000737:chemistry* / Q000378:metabolism; D059505:Telomere Homeostasis; D016808:Tetrahymena thermophila / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016053:RNA, Protozoan; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase