Positive and Negative Regulation of Tetrahymena Telomerase Holoenzyme
| Autor: | Ramadevi Prathapam, Kathleen Collins, Keren L. Witkin |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Telomerase
DNA Complementary Antibodies Gene Expression Regulation Enzymologic Telomerase RNA component chemistry.chemical_compound Animals Telomerase reverse transcriptase S-Phase Kinase-Associated Proteins Molecular Biology Telomere-binding protein biology Tetrahymena Articles Cell Biology biology.organism_classification Ubiquitin ligase Telomere Phenotype Biochemistry chemistry biology.protein Holoenzymes Peptides Gene Deletion DNA Protein Binding |
| Zdroj: | Molecular and Cellular Biology. 27:2074-2083 |
| ISSN: | 1098-5549 |
| DOI: | 10.1128/mcb.02105-06 |
| Popis: | Telomerase replenishes the telomeric repeats that cap eukaryotic chromosome ends. To perform DNA synthesis, the active site of telomerase reverse transcriptase (TERT) copies a template within the integral telomerase RNA (TER). In vivo, TERT and TER and additional subunits form a telomerase holoenzyme capable of telomere elongation. We previously purified epitope-tagged Tetrahymena thermophila TERT and characterized two of the associated proteins. Here we characterize the remaining two proteins that were enriched by TERT purification. The primary sequence of the p75 polypeptide lacks evident homology with other proteins, whereas the p20 polypeptide is the Tetrahymena ortholog of a conserved multifunctional protein, Skp1. Genetic depletion of p75 induced telomere shortening without affecting the accumulation of TER or TERT, suggesting that p75 promotes telomerase function at the telomere. Affinity purification of p75 coenriched telomerase activity and each other known telomerase holoenzyme protein. On the other hand, genetic depletion of Skp1p induced telomere elongation, suggesting that this protein plays a negative regulatory role in the maintenance of telomere length homeostasis. Affinity purification of Skp1p did not detectably enrich active telomerase but did copurify ubiquitin ligase machinery. These studies reveal additional complexity in the positive and negative regulation of Tetrahymena telomerase function. |
| Databáze: | OpenAIRE |
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