title: Template definition by Tetrahymena telomerase reverse transcriptase.
abstract: The ribonucleoprotein enzyme telomerase extends chromosome ends by copying a specific template sequence within its integral RNA component. An active recombinant telomerase RNP is minimally composed of this RNA and the telomerase reverse transcriptase (TERT) protein, which contains sequence motifs conserved among viral reverse transcriptases (RTs), flanked by N- and C-terminal extensions specific to TERTs. We have used site-directed mutagenesis to explore the roles of Tetrahymena TERT in determining features of telomerase activity in general and in establishing the boundaries and use of an internal RNA template in specific. We identify a new ciliate-specific motif in the TERT N-terminus required for template definition. Moreover, several residues in reverse transcriptase motifs 1, 2, A and D are critical for specific aspects of internal template use. Our results indicate that the unique specificity of telomerase activity is conferred to a reverse transcriptase active site by TERT residues both within and beyond the RT motif region.
authors.affiliation: Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3204, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Miller
authors.forename: J K
authors.initials: JK
authors.lastname: Liu
authors.forename: K
authors.initials: K
authors.lastname: Collins
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins; D006801:Humans; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012313:RNA / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012156:Reticulocytes / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019098:Telomerase / Q000737:chemistry / Q000235:genetics*; D013768:Tetrahymena / Q000201:enzymology*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; C422952:telomerase RNA; D012313:RNA; C509186:TERT protein, human; D019098:Telomerase; C509187:Tert protein, mouse