RETRACTED: 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 proteinnucleic acid interactions and the migration of POT1 from the telomere to the telomerase RNP.OB fold | RNA template | gene duplication

Telomerase and retrotransposons: Reverse transcriptases that shaped genomes

“…Dorothy Shippen presented a case of telomerase RNA (TER) duplication and functional specialization. In the plant Arabidopsis thaliana, one of the two TERs acts as a repressor rather than a stimulator of telomere elongation, possibly by forming an inactive complex with the catalytic TERT (15). This finding illustrates the adaptability of telomerase components.…”

Genetic Architecture of Natural Variation of Telomere Length inArabidopsis thaliana

“…This could also depend on the nature of investigated polymorphism as others may have immediate effects. Rates of telomere elongation and shortening are seen to be more drastic in studies where key genes involved in telomere metabolism are inactivated (Riha et al 2002;Surovtseva et al 2007;Cifuentes-Rojas et al 2011). Comparisons between published mutants and natural polymorphisms, however, are not straightforward as such polymorphisms will not necessarily knock out gene function, but are rather expected to modulate gene expression or protein functions and interactions.…”

“…Processes that mediate rapid changes in telomere length such as telomere rapid deletion and ALT have previously been described in Arabidopsis and could contribute to the establishment of new length homeostasis in early generations (Watson and Shippen 2007). Mapping of QTL by CIM analysis revealed two major loci that contribute to elongated telomeres; while none of the Pro-0/Col-0 QTL include KU70 or KU80, they do involve POT1 genes that encode proteins known to bind the TER1 component of telomerase (Surovtseva et al 2007;Cifuentes-Rojas et al 2011). Backcrosses of relevant RILs and further characterization of these loci would provide valuable information on important factors influencing telomere elongation.…”

Identification of PlantRAD52Homologs and Characterization of theArabidopsis thaliana RAD52-Like Genes

“…It was recently discovered that the telomerase RNA1 (TER1) transcript overlaps with the first two exons and introns of RAD52-1 (Cifuentes-Rojas et al, 2011). TER1 is the RNA subunit of telomerase and serves as a template for telomeric DNA addition.…”

“…RNA was extracted from inflorescences for analysis of TER1 expression in RAD52-1 knockdown lines. cDNA was synthesized using Superscript III, as described by Cifuentes-Rojas et al, (2011). TER1UF and TER1UR primers were used for the PCR (see Supplemental Table 2 online for primers sequences).…”