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Tetrahymena telomerase is active as a monomer
Tracy M Bryan1, Karen J Goodrich, Thomas R Cech
1Children's Medical Research Institute, Westmead, New South Wales 2145, Australia. tbryan@cmri.usyd.edu.au
Molecular Biology of the Cell
|September 19, 2003
Summary
Tetrahymena telomerase, composed of RNA and telomerase reverse transcriptase (TERT), functions as a monomer, not a dimer. This finding challenges the necessity of dimerization for telomerase activity and processivity.
Area of Science:
- Molecular Biology
- Biochemistry
- Enzymology
Background:
- Telomerase extends chromosomal DNA ends using an internal RNA template.
- The enzyme's catalytic core comprises RNA and telomerase reverse transcriptase (TERT).
- Previous studies suggest yeast and human telomerase can form active dimers or multimers.
Purpose of the Study:
- To investigate whether Tetrahymena thermophila telomerase requires dimerization for activity.
- To determine if Tetrahymena telomerase functions as a monomer or dimer.
Main Methods:
- Gel filtration chromatography to assess the size of recombinant Tetrahymena telomerase.
- Coprecipitation assays using tagged TERT protein and telomerase RNA to detect dimerization.
- Analysis of native telomerase from Tetrahymena cell extracts.
Main Results:
- Recombinant Tetrahymena telomerase eluted as a monomeric complex (one RNA plus one TERT).
- Fractions containing monomeric telomerase exhibited processive activity.
- Dimerization of Tetrahymena telomerase was not detected in recombinant or native forms.
- Native telomerase from Tetrahymena cell extracts also showed no signs of dimerization.
Conclusions:
- Tetrahymena telomerase is active and processive as a monomer.
- Dimerization is not essential for Tetrahymena telomerase function.
- This study provides evidence against the universal requirement of telomerase dimerization for activity.