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Vol. 14, Issue 12, 4794-4804, December 2003
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* Children's Medical Research Institute, Westmead, New South Wales 2145, Australia;
Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
Submitted July 4, 2003;
Revised August 22, 2003;
Accepted August 26, 2003
Monitoring Editor: Peter Walter
Telomerase is an enzyme that utilizes an internal RNA molecule as a template for the extension of chromosomal DNA ends. The catalytic core of telomerase consists of the RNA subunit and a protein reverse transcriptase subunit, known as telomerase reverse transcriptase (TERT). It has previously been shown that both yeast and human telomerase can form dimers or multimers in which one RNA in the complex can influence the activity of another. To test the proposal that dimerization might be essential for telomerase activity, we sought to determine whether Tetrahymena thermophila telomerase is active as a dimer or a monomer. Recombinant Tetrahymena telomerase eluted from a gel filtration column at the size of a monomeric complex (one RNA plus one TERT), and those fractions showed processive telomerase activity. We were unable to detect dimerization of Tetrahymena telomerase by coprecipitation experiments, by using tags on either the TERT protein or telomerase RNA. Therefore, a majority, if not all, of the recombinant Tetrahymena telomerase in our reconstitution system is present as a monomeric complex. We were also unable to detect dimerization of native telomerase from mating and vegetative Tetrahymena cell extracts. These results demonstrate that Tetrahymena telomerase does not need to dimerize to be active and processive.
Abbreviations used: DTT, dithiothreitol; TERT, telomerase reverse transcriptase.
Corresponding author. E-mail address: tbryan{at}cmri.usyd.edu.au.
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