title: Two RNA subunits and POT1a are components of Arabidopsis telomerase.
abstract: Telomerase is a ribonucleoprotein (RNP) reverse transcriptase whose essential RNA subunit (TER) functions as a template for telomere repeat synthesis. Here we report the identification of two divergent TER moieties in the flowering plant Arabidopsis thaliana. Although both TER1 and TER2 copurify with telomerase activity and serve as templates for telomerase in vitro, depletion of TER1, but not TER2, leads to decreased telomerase activity and progressive telomere shortening in vivo. Moreover, mutation of the templating domain in TER1 results in the incorporation of mutant telomere repeats on chromosome ends. Thus, TER1 provides the major template for telomerase in vivo. We also show that POT1a binds TER1 with a Kd of 2 × 10(-7) M and the two components assemble into an enzymatically active RNP in vivo. In contrast, TER1-POT1b and TER2-POT1a associations were not observed. In other organisms POT1 proteins bind telomeric DNA and provide chromosome end protection. We propose that duplication of TER and POT1 in Arabidopsis fueled the evolution of novel protein-nucleic acid interactions and the migration of POT1 from the telomere to the telomerase RNP.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A and M University, 2128 TAMU, College Station, TX 77843-2128, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Cifuentes-Rojas
authors.forename: Kalpana
authors.initials: K
authors.lastname: Kannan
authors.forename: Lin
authors.initials: L
authors.lastname: Tseng
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D017931:DNA Primers / Q000235:genetics; D020440:Gene Duplication / Q000235:genetics; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics*; D021141:Nucleic Acid Amplification Techniques; D009841:Oligonucleotides / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics*; D012313:RNA / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D009687:Nuclear Proteins; D009841:Oligonucleotides; C528256:POT1A protein, Arabidopsis; D021122:Protein Subunits; D012313:RNA; D019098:Telomerase