Telomerase reverse transcriptase genes identified in Tetrahymena thermophila and Oxytricha trifallax
AUTOR(ES)
Bryan, Tracy M.
FONTE
The National Academy of Sciences
RESUMO
Telomerase reverse transcriptase (TERT) has been identified as the catalytic subunit of the chromosome end-replicating enzyme in Euplotes, yeasts, and mammals. However, it was not reported among the protein components of purified Tetrahymena telomerase, the first telomerase identified and the most thoroughly studied. It therefore seemed possible that Tetrahymena used an alternative telomerase that lacked a TERT protein. We now report the cloning and sequencing of a Tetrahymena thermophila gene whose encoded protein has the properties expected for a TERT, including large size (133 kDa), basicity (calculated pI = 10.0), and reverse transcriptase sequence motifs with telomerase-specific features. The expression of mRNA from the Tetrahymena TERT gene increases dramatically at 2–5 h after conjugation, preceding de novo addition of telomeres to macronuclear DNA molecules. We also report the cloning and sequencing of the ortholog from Oxytricha trifallax. The Oxytricha macronuclear TERT gene has no introns, whereas that of Tetrahymena has 18 introns. Sequence comparisons reveal a new amino acid sequence motif (CP), conserved among the ciliated protozoan TERTs, and allow refinement of previously identified motifs. A phylogenetic tree of the known TERTs follows the phylogeny of the organisms in which they are found, consistent with an ancient origin rather than recent transposition. The conservation of TERTs among eukaryotes supports the model that telomerase has a conserved core (TERT plus the RNA subunit), with other subunits of the holoenzyme being more variable among species.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=21101Documentos Relacionados
- Template definition by Tetrahymena telomerase reverse transcriptase
- The reverse transcriptase component of the Tetrahymena telomerase ribonucleoprotein complex
- Telomerase catalysis: A phylogenetically conserved reverse transcriptase
- RNA Binding Domain of Telomerase Reverse Transcriptase
- Functional Multimerization of the Human Telomerase Reverse Transcriptase